The British Columbia Building Code | Section 4.1. | Structural Loads and Procedures Pt 2
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Section 4.1. Structural Loads and Procedures
4.1.1. General
4.1.1.1. Scope
1) The scope of this Part shall be as described in Subsection1.3.3.of Division A.
4.1.1.2. Definitions
1) Words that appear in italics in this Part are defined in Article1.4.1.2.of Division A.
4.1.1.3. Design Requirements
1) Buildings and their structural members and connections, including formwork and falsework, shall be designed
to have sufficient structural capacity and structural integrity to safely and effectively resist all loads, effects of loads
and influences that may reasonably be expected, having regard to the expected service life of buildings, and shall in any
case satisfy the requirements of this Section. (See Note A-4.1.1.3.(1).)
2) Buildings and their structural members shall be designed for serviceability, in accordance with
Articles4.1.3.4.,4.1.3.5. and4.1.3.6. (See Note A-4.1.1.3.(2).)
3) All permanent and temporary structural members, including the formwork and falsework of a building,
shall be protected against loads exceeding the specified loads during the construction period except when, as verified
by analysis or test, temporary overloading of a structural member would result in no impairment of that member or
any other member.
4) Falsework, scaffolding, and formwork shall be designed in conformance with
a) CSAS269.1, “Falsework for Construction Purposes,”
b) CAN/CSA-S269.2-M, “Access Scaffolding for Construction Purposes,” or
c) CAN/CSA-S269.3-M, “Concrete Formwork.”
5) Precautions shall be taken during all phases of construction to ensure that the building is not damaged or
distorted due to loads applied during construction.
4.1.1.4. Structural Drawings and Related Documents
1) Structural drawings and related documents shall conform to the appropriate requirements of Section2.2.of
DivisionC. (See Subsection2.2.4.of DivisionC.)
4.1.1.5. Design Basis
1) Except as provided in Sentence(2), buildings and their structural members shall be designed in conformance
with the procedures and practices provided in this Part.
2) Provided the design is carried out by a person especially qualified in the specific methods applied and
provided the design demonstrates a level of safety and performance in accordance with the requirements of Part4,
buildings and their structural components falling within the scope of Part4 that are not amenable to analysis using a
generally established theory may be designed by
a) evaluation of a full-scale structure or a prototype by a loading test, or
b) studies of model analogues.
(See NoteA-4.1.1.5.(2).)
4.1.2. Specified Loads and Effects
4.1.2.1. Loads and Effects
(See NoteA-4.1.2.1.)
1) Except as provided in Article4.1.2.2., the following categories of loads, specified loads and effects shall be
taken into consideration in the design of a building and its structural members and connections:
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
D dead load – a permanent load due to the weight of building components, as specified in Subsection4.1.4.,
E earthquake load and effects – a rare load due to an earthquake, as specified in Subsection4.1.8.,
H a permanent load due to lateral earth pressure, including groundwater,
L live load – a variable load due to intended use and occupancy (including loads due to cranes and the pressure
of liquids in containers), as specified in Subsection4.1.5.,
L
XC
live load exclusive of crane loads,
C live load due to cranes including self weight,
C
d
self weight of all cranes positioned for maximum effects,
C
7
crane bumper impact load,
P permanent effects caused by pre-stress,
S variable load due to snow, including ice and associated rain, as specified in Article4.1.6.2., or due to rain,
as specified in Article4.1.6.4.,
T effects due to contraction, expansion, or deflection caused by temperature changes, shrinkage, moisture
changes, creep, ground settlement, or a combination thereof (see NoteA-4.1.2.1.(1)), and
W wind load – a variable load due to wind, as specified in Subsection4.1.7.,
where
a) load means the imposed deformations (i.e.deflections, displacements or motions that induce deformations
and forces in the structure), forces and pressures applied to the building structure,
b) permanent load is a load that changes very little once it has been applied to the structure, except during
repair,
c) variable load is a load that frequently changes in magnitude, direction or location, and
d) rare load is a load that occurs infrequently and for a short time only.
2) Minimum specified values of the loads described in Sentence(1), as set forth in Subsections4.1.4. to 4.1.8.,
shall be increased to account for dynamic effects where applicable.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
3) For the purpose of determining specified loads S, W or E in Subsections4.1.6., 4.1.7. and4.1.8., buildings
shall be assigned an Importance Category based on intended use and occupancy, in accordance with Table4.1.2.1.
(SeeNoteA-4.1.2.1.(3).)
4.1.2.2. Loads Not Listed
1) Where a building or structural member can be expected to be subjected to loads, forces or other effects not
listed in Article4.1.2.1., such effects shall be taken into account in the design based on the most appropriate
information available.
4.1.3. Limit States Design
(See NoteA-4.1.3.)
4.1.3.1. Definitions
1) In this Subsection, the term
a) limit states means those conditions of a building structure that result in the building ceasing to fulfill the
function for which it was designed (those limit states concerning safety are called ultimate limit states (ULS)
and include exceeding the load-carrying capacity, overturning, sliding and fracture; those limit states that
restrict the intended use and occupancy of the building are called serviceability limit states (SLS) and include
deflection, vibration, permanent deformation and local structural damage such as cracking; and those limit
states that represent failure under repeated loading are called fatigue limit states),
b) specified loads (C, D, E, H, L, P, S, T and W) means those loads defined in Article4.1.2.1.,
c) principal load means the specified variable load or rare load that dominates in a given load combination,
Table 4.1.2.1.
Importance Categories for Buildings
Forming Part of Sentence 4.1.2.1.(3)
Use and Occupancy Importance Category
Buildings that represent a low direct or indirect hazard to human life in the event of failure, including:
• low human-occupancy buildings, where it can be shown that collapse is not likely to cause injury or other serious
consequences
• minor storage buildings
Low
(1)
All buildings except those listed in Importance Categories Low, High and Post-disaster Normal
Buildings that are likely to be used as post-disaster shelters, including buildings whose primary use is:
• as an elementary, middle or secondary school
• as a community centre
Manufacturing and storage facilities containing toxic, explosive or other hazardous substances in sufficient quantities to be
dangerous to the public if released
(1)
High
Post-disaster buildings are buildings that are essential to the provision of services in the event of a disaster, and include:
• hospitals, emergency treatment facilities and blood banks
• telephone exchanges
• power generating stations and electrical substations
• control centres for air, land and marine transportation
• public water treatment and storage facilities, and pumping stations
• sewage treatment facilities and buildings having critical national defence functions
• buildings of the following types, unless exempted from this designation by the authority having jurisdiction:
(2)
• emergency response facilities
• fire, rescue and police stations, and housing for vehicles, aircraft or boats used for such purposes
• communications facilities, including radio and television stations
Post-disaster
Notes to Table4.1.2.1.:
(1) See Note A-Table 4.1.2.1.
(2) See Note A-1.4.1.2.(1), Post-disaster Buildings, in Division A.
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
d) companion load means a specified variable load that accompanies the principal load in a given load
combination,
e) service load means a specified load used for the evaluation of a serviceability limit state,
f) principal-load factor means a factor applied to the principal load in a load combination to account for the
variability of the load and load pattern and the analysis of its effects,
g) companion-load factor means a factor that, when applied to a companion load in the load combination,
givesthe probable magnitude of a companion load acting simultaneously with the factored principal load,
h) importance factor, I, means a factor applied in Subsections4.1.6.,4.1.7. and4.1.8. to obtain the specified load
and take into account the consequences of failure as related to the limit state and the use and occupancy of the
building,
i) factored load means the product of a specified load and its principal-load factor or companion-load factor,
j) effects refers to forces, moments, deformations or vibrations that occur in the structure,
k) nominal resistance, R, of a member, connection or structure, is based on the geometry and on the specified
properties of the structural materials,
l) resistance factor, , means a factor applied to a specified material property or to the resistance of a member,
connection or structure, and that, for the limit state under consideration, takes into account the variability of
dimensions and material properties, workmanship, type of failure and uncertainty in the prediction of
resistance, and
m) factored resistance, R, means the product of nominal resistance and the applicable resistance factor.
4.1.3.2. Strength and Stability
1) A building and its structural components shall be designed to have sufficient strength and stability so that the
factored resistance, R, is greater than or equal to the effect of factored loads, which shall be determined in
accordance with Sentence4.1.3.2.(2).
2) Except as provided in Sentence(3), the effect of factored loads for a building or structural component shall be
determined in accordance with the requirements of this Article and the following load combination cases, the
applicable combination being that which results in the most critical effect:
a) for load cases without crane loads, the load combinations listed in Table4.1.3.2.-A, and
b) for load cases with crane loads, the load combinations listed in Table4.1.3.2.-B.
(See NoteA-4.1.3.2.(2).)
3) Other load combinations that must also be considered are the principal loads acting with the companion
loads taken as zero.
4) Where the effects due to lateral earth pressure, H, restraint effects from pre-stress, P, and imposed
deformation, T, affect the structural safety, they shall be taken into account in the calculations, with load factors of
1.5, 1.0 and 1.25 assigned to H, P and T respectively. (See NoteA-4.1.3.2.(4).)
5) Except as provided in Sentence4.1.8.16.(2), the counteracting factored dead load – 0.9D in load combination
cases 2, 3 and 4 and 1.0D in load combination case 5 in Table4.1.3.2.-A, and 0.9D in load combination cases 1 to 5
and 1.0D in load combination case 6 in Table4.1.3.2.-B – shall be used when the dead load acts to resist overturning,
uplift, sliding, failure due to stress reversal, and to determine anchorage requirements and the factored resistance of
members. (See NoteA-4.1.3.2.(5).)
6) The principal-load factor 1.5 for live loads L in Table4.1.3.2.-A and L
XC
in Table4.1.3.2.-B may be reduced to
1.25 for liquids in tanks.
7) The companion-load factor for live loads L in Table4.1.3.2.-A and L
XC
in Table4.1.3.2.-B shall be increased
by 0.5 for storage areas, and equipment areas and service rooms referred to in Table4.1.5.3.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
8) Except as provided in Sentence(9), the load factor 1.25 for dead load, D, for soil, superimposed earth, plants
and trees given in Tables4.1.3.2.-A and4.1.3.2.-B shall be increased to 1.5, except that when the soil depth exceeds
1.2m, the factor may be reduced to 1+0.6/h
s
but not less than 1.25, where hs is the depth of soil in metres
supported by the structure.
9) A principal-load factor of 1.5 shall be applied to the weight of saturated soil used in load combination case 1
of Table4.1.3.2.-A.
10) Earthquake load, E, in load combination cases5 of Table4.1.3.2.-A and 6 of Table4.1.3.2.-B includes
horizontal earth pressure due to earthquake determined in accordance with Sentence4.1.8.16.(7).
Table 4.1.3.2.-A
Load Combinations Without Crane Loads for Ultimate Limit States
Forming Part of Sentences 4.1.3.2.(2) and (5) to (10)
Case
Load Combination
(1)
Principal Loads Companion Loads
11.4D
(2)
–
2 (1.25D
(3)
or 0.9D
(4)
) + 1.5L
(5)
1.0S
(6)
or 0.4W
3 (1.25D
(3)
or 0.9D
(4)
) + 1.5S 1.0L
(6)(7)
or 0.4W
4 (1.25D
(3)
or 0.9D
(4)
) + 1.4W 0.5L
(7)
or 0.5S
51.0D
(4)
+ 1.0E
(8)
0.5L
(6)(7)
+ 0.25S
(6)
Notes to Table4.1.3.2.-A:
(1) See Sentences 4.1.3.2.(2), (3) and (4).
(2) See Sentence 4.1.3.2.(9).
(3) See Sentence 4.1.3.2.(8).
(4) See Sentence 4.1.3.2.(5).
(5) See Sentence 4.1.3.2.(6).
(6) See Article 4.1.5.5.
(7) See Sentence 4.1.3.2.(7).
(8) See Sentence 4.1.3.2.(10).
Table 4.1.3.2.-B
Load Combinations With Crane Loads for Ultimate Limit States
Forming Part of Sentences 4.1.3.2.(2), (5) to (8), and (10)
Case
Load Combination
(1)
Principal Loads Companion Loads
1(1.25D
(2)
or 0.9D
(3)
) + (1.5C + 1.0L
XC
)1.0S
(4)
or 0.4W
2(1.25D
(2)
or 0.9D
(3)
) + (1.5L
XC
(5)
+ 1.0C) 1.0S
(4)
or 0.4W
3(1.25D
(2)
or 0.9D
(3)
) + 1.5S 1.0C + 1.0L
XC
(4)(6)
)
4(1.25D
(2)
or 0.9D
(3)
) + 1.4W (1.0C
(7)
+ 0.5L
XC
(4)(6)
)
5(1.25D
(2)
or 0.9D
(3)
) + C
7
–
61.0D
(3)
+ 1.0E
(8)
1.0C
d
+ 0.5L
XC
(4)(6)
+ 0.25S
(4)
Notes to Table4.1.3.2.-B:
(1) See Sentences 4.1.3.2.(2), (3) and (4).
(2) See Sentence 4.1.3.2.(8).
(3) See Sentence 4.1.3.2.(5).
(4) See Article 4.1.5.5.
(5) See Sentence 4.1.3.2.(6).
(6) See Sentence 4.1.3.2.(7).
(7) Side thrust due to cranes need not be combined with full wind load.
(8) See Sentence 4.1.3.2.(10).
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
11) Provision shall be made to ensure adequate stability of the structure as a whole and adequate lateral, torsional
and local stability of all structural parts.
12) Sway effects produced by vertical loads acting on the structure in its displaced configuration shall be taken
into account in the design of buildings and their structural members.
4.1.3.3. Fatigue
1) A building and its structural components, including connections, shall be checked for fatigue failure under the
effect of cyclical loads, as required in the standards listed in Section4.3. (See NoteA-4.1.3.3.(1).)
2) Where vibration effects, such as resonance and fatigue resulting from machinery and equipment, are likely to
be significant, a dynamic analysis shall be carried out. (See NoteA-4.1.3.3.(2).)
4.1.3.4. Serviceability
1) A building and its structural components shall be checked for serviceability limit states as defined in
Clause4.1.3.1.(1)(a) under the effect of service loads for serviceability criteria specified or recommended in
Articles4.1.3.5. and4.1.3.6. and in the standards listed in Section4.3. (SeeNoteA-4.1.3.4.(1).)
4.1.3.5. Deflection
1) In proportioning structural members to limit serviceability problems resulting from deflections,
consideration shall be given to
a) the intended use of the building or member,
b) limiting damage to non-structural members made of materials whose physical properties are known at the
time of design,
c) limiting damage to the structure itself, and
d) creep, shrinkage, temperature changes and pre-stress.
(See NoteA-4.1.3.5.(1).)
2) The lateral deflection of buildings due to service wind and gravity loads shall be checked to ensure that
structural elements and non-structural elements whose nature is known at the time the structural design is carried out
will not be damaged.
3) Except as provided in Sentence(4), the total drift per storey under service wind and gravity loads shall not
exceed 1/500 of the storey height unless other drift limits are specified in the design standards referenced in
Section4.3. (See NoteA-4.1.3.5.(3).)
4)
The deflection limits required in Sentence(3) do not apply to industrial buildings or sheds if experience has
proven that greater movement will have no significant adverse effects on the strength and function of the building.
5) The building structure shall be designed for lateral deflection due to E, in accordance with Article4.1.8.13.
4.1.3.6. Vibration
1) Floor systems susceptible to vibration shall be designed so that vibrations will have no significant adverse
effects on the intended occupancy of the building. (See NoteA-4.1.3.6.(1).)
2) Where the fundamental vibration frequency of a structural system supporting an assembly occupancy used for
rhythmic activities, such as dancing, concerts, jumping exercises or gymnastics, is less than 6 Hz, the effects of
resonance shall be investigated by means of a dynamic analysis. (See NoteA-4.1.3.6.(2).)
3) A building susceptible to lateral vibration under wind load shall be designed in accordance with Article4.1.7.1.
so that the vibrations will have no significant adverse effects on the intended use and occupancy of the building.
(SeeNoteA-4.1.3.6.(3).)
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4.1.4. Dead Loads
4.1.4.1. Dead Loads
1) The specified dead load for a structural member consists of
a) the weight of the member itself,
b) the weight of all materials of construction incorporated into the building to be supported permanently by the
member,
c) the weight of partitions,
d) the weight of permanent equipment, and
e) the vertical load due to earth, plants and trees.
2) Except as provided in Sentence(5), in areas of a building where partitions, other than permanent partitions,
areshown on the drawings, or where partitions might be added in the future, allowance shall be made for the weight
of such partitions.
3) The partition weight allowance referred to in Sentence(2) shall be determined from the actual or anticipated
weight of the partitions placed in any probable position, but shall be not less than 1kPa over the area of floor being
considered.
4) Partition loads used in design shall be shown on the drawings as provided in Clause2.2.4.3.(1)(d)of
DivisionC.
5) In cases where the dead load of the partition is counteractive, the load allowances referred to in Sentences(2)
and(3) shall not be included in the design calculations.
6) Except for structures where the dead load of soil is part of the load-resisting system, where the dead load due to
soil, superimposed earth, plants and trees is counteractive, it shall not be included in the design calculations.
(SeeNoteA-4.1.4.1.(6).)
4.1.5. Live Loads Due to Use and Occupancy
4.1.5.1. Loads Due to Use of Floors and Roofs
1) Except as provided in Sentence(2), the specified live load on an area of floor or roof depends on the intended
use and occupancy, and shall not be less than either the uniformly distributed load patterns listed in Article4.1.5.3., the
loads due to the intended use and occupancy, or the concentrated loads listed in Article4.1.5.9., whichever produces
the most critical effect. (See NoteA-4.1.5.1.(1).)
2) For buildings in the Low Importance Category as described in Table4.1.2.1., a factor of 0.8 may be applied to
the live load.
4.1.5.2. Uses Not Stipulated
1) Except as provided in Sentence(2), where the use of an area of floor or roof is not provided for in
Article4.1.5.3., the specified live loads due to the use and occupancy of the area shall be determined from an analysis of
the loads resulting from the weight of
a) the probable assembly of persons,
b) the probable accumulation of equipment and furnishings, and
c) the probable storage of materials.
2) For buildings in the Low Importance Category as described in Table4.1.2.1., a factor of 0.8 may be applied to
the live load.
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.5.3. Full and Partial Loading
1) The uniformly distributed live load shall be not less than the value listed in Table4.1.5.3., which may be
reduced as provided in Article4.1.5.8., applied uniformly over the entire area or on any portions of the area,
whichever produces the most critical effects in the members concerned.
Table 4.1.5.3.
Specified Uniformly Distributed Live Loads on an Area of Floor or Roof
Forming Part of Sentence 4.1.5.3.(1)
Use of Area of Floor or Roof Minimum Specified Load,kPa
Assembly Areas
4.8
a) Except for the areas listed under b), c), d) and e), assembly areas with or without fixed seats
including
Arenas
(1)
(areas without fixed seats that have backs)
Auditoria
Churches (areas without fixed seats that have backs)
Dance floors
Dining areas
(2)
Foyers and entrance halls
Grandstands
(1)
(areas without fixed seats that have backs), reviewing stands and bleachers
Gymnasia
Lecture halls
(1)
(areas without fixed seats that have backs)
Museums
Promenades
Rinks
Stadia
(1)
(areas without fixed seats that have backs)
Theatres (areas without fixed seats that have backs)
Other areas with similar uses
b) Classrooms and courtrooms with or without fixed seats
(1)
2.4
c) Portions of assembly areas with fixed seats that have backs for the following uses:
2.9
(1)
Arenas
Grandstands
Stadia
d) Portions of assembly areas with fixed seats that have backs for the following uses:
2.4
Churches
Lecture halls
(1)
Theatres
e) Vomitories, exits, lobbies and corridors
(1)
4.8
Attics
(1)
Accessible by a stairway in residential occupancies only 1.4
Having limited accessibility so that there is no storage of equipment or material 0.5
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Balconies
Exterior 4.8
Interior and mezzanines that could be used by an assembly of people as a viewing area
(1)
4.8
Interior and mezzanines other than above
(3)
Corridors, lobbies and aisles
(1)
Other than those listed below 4.8
Not more than 1 200 mm in width and all upper floor corridors of residential areas only of
apartments, hotels and motels (that cannot be used by an assembly of people as a
viewing area)
(1)
(1)(3)
Equipment areas and service rooms including
3.6
(4)
Generator rooms
Mechanical equipment exclusive of elevators
Machine rooms
Pump rooms
Transformer vaults
Ventilating or air-conditioning equipment
Exits and fire escapes 4.8
Factories 6.0
(4)
Footbridges 4.8
Garages for
Vehicles not exceeding 4 000 kg gross weight 2.4
Vehicles exceeding 4 000 kg but not exceeding 9 000 kg gross weight 6.0
Vehicles exceeding 9 000 kg gross weight 12.0
(1)
Kitchens (other than residential) 4.8
Libraries
Stack rooms 7.2
Reading and study rooms 2.9
Office areas (not including record storage and computer rooms) located in
Basement and the first storey 4.8
Floors above the first storey 2.4
Operating rooms and laboratories 3.6
Patients’ bedrooms 1.9
Recreation areas that cannot be used for assembly purposes including
3.6
Billiard rooms
Bowling alleys
Pool rooms
Table 4.1.5.3. (continued)
Specified Uniformly Distributed Live Loads on an Area of Floor or Roof
Forming Part of Sentence 4.1.5.3.(1)
Use of Area of Floor or Roof Minimum Specified Load,kPa
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.5.4. Loads for Occupancy Served
1) The following shall be designed to carry not less than the specified load required for the occupancy they serve,
provided they cannot be used by an assembly of people as a viewing area:
a) corridors, lobbies and aisles not more than 1 200mm wide,
b) all corridors above the first storey of residential areas of apartments, hotels and motels, and
c) interior balconies and mezzanines.
4.1.5.5. Loads on Exterior Areas
(See NoteA-4.1.5.5.)
1) Exterior areas accessible to vehicular traffic shall be designed for their intended use, including the weight of
firefighting equipment, but not for less than the snow and rain loads prescribed in Subsection4.1.6.
2) Except as provided in Sentences(3) and(4), roofs shall be designed for either the uniform live loads specified
in Table4.1.5.3., the concentrated live loads listed in Table4.1.5.9., or the snow and rain loads prescribed in
Subsection4.1.6., whichever produces the most critical effects in the members concerned.
3) Exterior areas accessible to pedestrian traffic, but not vehicular traffic, shall be designed for their intended
use, but not for less than the greater of
a) the live load prescribed for assembly areas in Table4.1.5.3., or
b) the snow and rain loads prescribed in Subsection4.1.6.
4) Roof parking decks shall be designed for either the uniformly distributed live loads specified in Table4.1.5.3.,
the concentrated live loads listed in Table4.1.5.9., or the roof snow load, whichever produces the most critical effect in
the members concerned.
Residential areas (within the scope of Article 1.3.3.2. of Division A)
Sleeping and living quarters in apartments, hotels, motels, boarding schools and colleges 1.9
Residential areas (within the scope of Article 1.3.3.3. of Division A)
Bedrooms 1.9
Other areas 1.9
Stairs within dwelling units 1.9
Retail and wholesale areas 4.8
Roofs 1.0
(1)(5)
Sidewalks and driveways over areaways and basements 12.0
(1)(5)
Storage areas 4.8
(4)
Toilet areas 2.4
Underground slabs with earth cover
(5)
Warehouses 4.8
(4)
Notes to Table4.1.5.3.:
(1) See Note A-Table 4.1.5.3.
(2) See Article 4.1.5.6.
(3) See Article 4.1.5.4.
(4) See Sentence 4.1.5.1.(1).
(5) See Article 4.1.5.5.
Table 4.1.5.3. (continued)
Specified Uniformly Distributed Live Loads on an Area of Floor or Roof
Forming Part of Sentence 4.1.5.3.(1)
Use of Area of Floor or Roof Minimum Specified Load,kPa
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4.1.5.6. Loads for Dining Areas
1) The minimum specified live load listed in Table4.1.5.3. for dining areas may be reduced to 2.4kPa for areas in
buildings that are being converted to dining areas, provided that the floor area does not exceed 100m
2
and the dining
area will not be used for other assembly purposes, including dancing.
4.1.5.7. More Than One Occupancy
1) Where an area of floor or roof is intended for 2 or more occupancies at different times, the value to be used
from Table4.1.5.3. shall be the greatest value for any of the occupancies concerned.
4.1.5.8. Variation with Tributary Area
(See NoteA-4.1.5.8.)
1) An area used for assembly occupancies designed for a live load of less than 4.8kPa and roofs designed for the
minimum loading specified in Table4.1.5.3. shall have no reduction for tributary area.
2) Where a structural member supports a tributary area of a floor or a roof, or a combination thereof, that is
greater than 80m
2
and either used for assembly occupancies designed for a live load of 4.8kPa or more, or used for
storage, manufacturing, retail stores, garages or as a footbridge, the specified live load due to use and occupancy is the
load specified in Article4.1.5.3. multiplied by
where A is the tributary area in square metres for this type of use and occupancy.
3) Where a structural member supports a tributary area of a floor or a roof, or a combination thereof, that is
greater than 20m
2
and used for any use or occupancy other than those indicated in Sentences(1) and(2), the specified
live load due to use and occupancy is the load specified in Article4.1.5.3. multiplied by
where B is the tributary area in square metres for this type of use and occupancy.
4) Where the specified live load for a floor is reduced in accordance with Sentence(2) or(3), the structural
drawings shall indicate that a live load reduction factor for tributary area has been applied.
0.5 冪 20/A
0.3 冪 9.8/B
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.5.9. Concentrated Loads
1) The specified live load due to possible concentrations of load resulting from the use of an area of floor or roof
shall not be less than that listed in Table4.1.5.9. applied over the loaded area noted and located so as to cause
maximum effects, except that for occupancies not listed in Table4.1.5.9., the concentrations of load shall be
determined in accordance with Article4.1.5.2.
4.1.5.10. Sway Forces in Assembly Occupancies
1) The floor assembly and other structural elements that support fixed seats in any building used for assembly
occupancies accommodating large numbers of people at one time, such as grandstands, stadia and theatre balconies,
shallbe designed to resist a horizontal force equal to not less than 0.3kN for each metre length of seats acting
parallel to each row of seats, and not less than 0.15kN for each metre length of seats acting at right angles to each
row of seats, based on the assumption that these forces are acting independently of each other.
4.1.5.11. Crane-Supporting Structures and Impact of Machinery and Equipment
(See NoteA-4.1.5.11.)
1) The minimum specified load due to equipment, machinery or other objects that may produce impact shall be
the sum of the weight of the equipment or machinery and its maximum lifting capacity, multiplied by an appropriate
factor listed in Table4.1.5.11.
2) Crane-supporting structures shall be designed for the appropriate load combinations listed in Article4.1.3.2.
3) Crane runway structures shall be designed to resist a horizontal force applied normal to the top of the rails
equal to not less than 20% of the sum of the weights of the lifted load and the crane trolley (excluding other parts of
the crane).
4) The force described in Sentence(3) shall be equally distributed on each side of the runway and shall be
assumed to act in either direction.
5) Crane runway structures shall be designed to resist a horizontal force applied parallel to the top of the rails
equal to not less than 10% of the maximum wheel loads of the crane.
Table 4.1.5.9.
Specified Concentrated Live Loads on an Area of Floor or Roof
Forming Part of Sentence 4.1.5.9.(1)
Area of Floor or Roof
Minimum Specified Concentrated
Load,kN
Loaded Area,mm xmm
Roof surfaces 1.3 200 x 200
Floors of classrooms 4.5 750 x 750
Floors of offices, manufacturing buildings, hospital wards and stages 9.0 750 x 750
Floors and areas used by vehicles not exceeding 4 000 kg gross weight 18 120 x 120
Floors and areas used by vehicles exceeding 4 000 kg but not exceeding
9 000 kg gross weight
36 120 x 120
Floors and areas used by vehicles exceeding 9 000 kg gross weight 54
(1)
250 x 600
(1)
Driveways and sidewalks over areaways and basements 54
(1)
250 x 600
(1)
Notes to Table4.1.5.9.:
(1) See Note A-Table 4.1.5.9.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4.1.5.12. Bleachers
1) Bleacher seats shall be designed for a uniformly distributed live load of 1.75kN for each linear metre or for a
concentrated load of 2.2kN distributed over a length of 0.75 m, whichever produces the most critical effect on the
supporting members.
2) Bleachers shall be checked by the erector after erection to ensure that all structural members, including
bracing specified in the design, have been installed.
3) Telescopic bleachers shall be provided with locking devices to ensure stability while in use.
4.1.5.13. Helicopter Landing Areas
1) Helicopter landing areas on roofs shall be constructed in conformance with the requirements for heliports
contained in TC SOR/96-433, “Canadian Aviation Regulations – Part III.”
4.1.5.14. Loads on Guards and Handrails
(See NoteA-4.1.5.14. and 4.1.5.15.(1).)
1) The minimum specified horizontal load applied outward at the minimum required height of every required
guard shall be
a) 3.0kN/m for open viewing stands without fixed seats and for means of egress in grandstands, stadia, bleachers
and arenas,
b) a concentrated load of 1.0kN applied at any point, so as to produce the most critical effect, for access ways
to equipment platforms, contiguous stairs and similar areas where the gathering of many people is
improbable, and
c) 0.75kN/m or a concentrated load of 1.0kN applied at any point so as to produce the most critical effect,
whichever governs for locations other than those described in Clauses(a) and(b).
2) The minimum specified horizontal load applied inward at the minimum required height of every required
guard shall be half that specified in Sentence(1).
3) Individual elements within the guard, including solid panels and pickets, shall be designed for a load of 0.5kN
applied outward over an area of 100mm by 100mm located at any point in the element or elements so as to produce
the most critical effect.
4) The size of the opening between any two adjacent vertical elements within a guard shall not exceed the limits
required by Part3 when each of these elements is subjected to a specified live load of 0.1
kN applied in opposite
directions in the in-plane direction of the guard so as to produce the most critical effect.
5) The loads required in Sentence(3) need not be considered to act simultaneously with the loads provided for
in Sentences(1),(2) and(6).
6) The minimum specified load applied vertically at the top of every required guard shall be 1.5kN/m and need
not be considered to act simultaneously with the horizontal load provided for in Sentence(1).
Table 4.1.5.11.
Factors for the Calculation of Impact Loads
Forming Part of Sentence 4.1.5.11.(1)
Cause of Impact Factor
Operation of cab or radio-operated cranes 1.25
Operation of pendant or hand-operated cranes 1.10
Operation of elevators
(1)
Supports for light machinery, shaft or motor-driven 1.20
Supports for reciprocating machinery (e.g. compressors) 1.50
Supports for power-driven units (e.g. piston engines) 1.50
Notes to Table4.1.5.11.:
(1) See the Elevating Devices Safety Regulation
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
7) Handrails and their supports shall be designed and constructed to withstand the following loads, which need
not be considered to act simultaneously:
a) a concentrated load not less than 0.9kN applied at any point and in any direction for all handrails, and
b) a uniform load not less than 0.7kN/m applied in any direction to handrails not located within dwelling units.
4.1.5.15. Loads on Vehicle Guardrails
1) Vehicle guardrails shall be designed for a concentrated load of 22kN applied horizontally outward at any
point 500mm above the floor surface so as to produce the most critical effect. (See NoteA-4.1.5.14.
and 4.1.5.15.(1).)
2) The loads required in Sentence(1) need not be considered to act simultaneously with the loads provided for
in Article4.1.5.14.
4.1.5.16. Loads on Walls Acting As Guards
1) Where the floor elevation on one side of a wall, including a wall around a shaft, is more than 600mm higher
than the elevation of the floor or ground on the other side, the wall shall be designed to resist the appropriate
outward lateral design loads prescribed elsewhere in Subsection4.1.5. or 0.5kPa acting outward, whichever produces
the more critical effect.
4.1.5.17. Firewalls
(See NoteA-4.1.5.17.)
1) Firewalls shall be designed to resist the maximum effect due to
a) the appropriate lateral design loads prescribed elsewhere in this Section, or
b) a factored lateral load of 0.5kPa under fire conditions, as described in Sentence(2).
2) Under fire conditions, where the fire-resistance rating of the structure is less than that of the firewall,
a) lateral support shall be assumed to be provided by the structure on one side only, or
b) another structural support system capable of resisting the loads imposed by a fire on either side of the firewall
shall be provided.
4.1.6. Loads Due to Snow and Rain
4.1.6.1. Specified Load Due to Rain or to Snow and Associated Rain
1) The specified load on a roof or any other building surface subject to snow and associated rain shall be the
snow load specified in Article4.1.6.2., or the rain load specified in Article4.1.6.4., whichever produces the more
critical effect.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4.1.6.2. Specified Snow Load
(See NoteA-4.1.6.2.)
1) The specified load, S, due to snow and associated rain accumulation on a roof or any other building surface
subject to snow accumulation shall be calculated using the formula
where
I
s
= importance factor for snow load as provided in Table4.1.6.2.-A,
S
s
= 1-in-50-year ground snow load, inkPa, determined in accordance with Subsection1.1.3.,
C
b
= basic roof snow load factor in Sentence(2),
C
w
= wind exposure factor in Sentences(3) and(4),
C
s
= slope factor in Sentences(5), (6) and(7),
C
a
= accumulation factor in Sentence(8), and
S
r
= 1-in-50-year associated rain load, in kPa, determined in accordance with Subsection1.1.3., but not
greater than S
s
(C
b
C
w
C
s
C
a
).
2) The basic roof snow load factor, C
b
, shall
a) be determined as follows:
i)
ii)
where
l
c
= characteristic length of the upper or lower roof, defined as 2w−w
2
/l, in m,
w = smaller plan dimension of the roof, in m, and
l = larger plan dimension of the roof, in m, or
b) conform to Table4.1.6.2.-B, using linear interpolation for intermediate values of l
c
C
w
2
.
(See NoteA-4.1.6.2.(2).)
3) Except as provided for in Sentence(4), the wind exposure factor, C
w
, shall be 1.0.
Table 4.1.6.2.-A
Importance Factor for Snow Load, I
S
Forming Part of Sentence 4.1.6.2.(1)
Importance Category
Importance Factor, Is
ULS SLS
Low 0.8 0.9
Normal 1 0.9
High 1.15 0.9
Post-disaster 1.25 0.9
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4) For buildings in the Low and Normal Importance Categories as set out in Table4.1.2.1., the wind exposure
factor, C
w
, given in Sentence(3) may be reduced to 0.75 for rural areas only, or to 0.5 for exposed areas north of the
treeline, where
a) the building is exposed on all sides to wind over open terrain as defined in Clause4.1.7.3.(5)(a), and is expected
to remain so during its life,
b) the area of roof under consideration is exposed to the wind on all sides with no significant obstructions on
the roof, such as parapet walls, within a distance of at least 10times the difference between the height of the
obstruction and C
b
C
w
S
s
/ metres, where is the specific weight of snow on roofs as specified in
Article4.1.6.13., and
c) the loading does not involve the accumulation of snow due to drifting from adjacent surfaces.
5) Except as provided for in Sentences(6) and(7), the slope factor, C
s
, shall be
a) 1.0 where the roof slope, , is equal to or less than 30°,
b) (70° − )/40° where is greater than 30° but not greater than 70°, and
c) 0 where exceeds 70°.
Table 4.1.6.2.-B
Basic Roof Snow Load Factor for l
c
> (70/C
w
2
)
Forming Part of Sentence 4.1.6.2.(2)
Value of
l
c
C
w
2
Value of C
w
1.0 0.75 0.5
Value of C
b
70 0.80 0.80 0.80
80 0.82 0.85 0.91
100 0.85 0.94 1.11
120 0.88 1.01 1.27
140 0.90 1.07 1.40
160 0.92 1.12 1.51
180 0.93 1.16 1.60
200 0.95 1.19 1.67
220 0.96 1.21 1.73
240 0.96 1.24 1.78
260 0.97 1.25 1.82
280 0.98 1.27 1.85
300 0.98 1.28 1.88
320 0.98 1.29 1.90
340 0.99 1.30 1.92
360 0.99 1.30 1.93
380 0.99 1.31 1.95
400 0.99 1.31 1.96
420 0.99 1.32 1.96
440 1.00 1.32 1.97
460 1.00 1.32 1.98
480 1.00 1.32 1.98
500 1.00 1.33 1.98
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
6) The slope factor, Cs, for unobstructed slippery roofs where snow and ice can slide completely off the roof
shall be
a) 1.0 where the roof slope, , is equal to or less than 15°,
b) (60° − )/45° where is greater than 15° but not greater than 60°, and
c)
where exceeds 60°.
7) Unless otherwise stated in this Subsection, the slope factor, C
s
, shall be 1.0 when used in conjunction with
accumulation factors for increased snow loads.
8) The accumulation factor, C
a
, shall be 1.0, which corresponds to the uniform snow load case, except that
where appropriate for the shape of the roof, it shall be assigned other values that account for
a) increased non-uniform snow loads due to snow drifting onto a roof that is at a level lower than other parts of
the same building or at a level lower than another building within 5m of it horizontally, as prescribed in
Articles4.1.6.5., 4.1.6.6. and4.1.6.8.,
b) increased non-uniform snow loads on areas adjacent to roof projections, such as penthouses, large chimneys
and equipment, as prescribed in Articles4.1.6.7. and4.1.6.8.,
c) non-uniform snow loads on gable, arch or curved roofs and domes, as prescribed in Articles4.1.6.9.
and4.1.6.10.,
d) increased snow or ice loads due to snow sliding as prescribed in Article4.1.6.11.,
e) increased snow loads in roof valleys, as prescribed in Article4.1.6.12., and
f) increased snow or ice loads due to meltwater draining from adjacent building elements and roof projections.
9) For shapes not addressed in Sentence(8), C
a
corresponding to the non-uniform snow load case shall be
established based on applicable field observations, special analyses including local climatic effects, appropriate model
tests, or a combination of these methods.
4.1.6.3. Full and Partial Loading
1) A roof or other building surface and its structural members subject to loads due to snow accumulation shall be
designed for the specified load given in Sentence4.1.6.2.(1), distributed over the entire loaded area.
2) In addition to the distribution mentioned in Sentence(1), flat roofs and shed roofs, gable roofs of 15° slope
or less, and arch or curved roofs shall be designed for the specified uniform snow load indicated in
Sentence4.1.6.2.(1), which shall be calculated using the accumulation factor C
a
= 1.0, distributed on any one portion
of the loaded area and half of this load on the remainder of the loaded area, in such a way as to produce the most
critical effects on the member concerned. (See NoteA-4.1.6.3.(2).)
520 1.00 1.33 1.99
540 1.00 1.33 1.99
560 1.00 1.33 1.99
580 1.00 1.33 1.99
600 1.00 1.33 1.99
620 1.00 1.33 2.00
Table 4.1.6.2.-B (continued)
Basic Roof Snow Load Factor for l
c
> (70/C
w
2
)
Forming Part of Sentence 4.1.6.2.(2)
Value of
l
c
C
w
2
Value of C
w
1.0 0.75 0.5
Value of C
b
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.6.4. Specified Rain Load
1) Except as provided in Sentence(4), the specified load, S, due to the accumulation of rainwater on a surface
whose position, shape and deflection under load make such an accumulation possible, is that resulting from the
one-day rainfall determined in conformance with Subsection1.1.3. and applied over the horizontal projection of the
surface and all tributary surfaces. (See NoteA-4.1.6.4.(1).)
2) The provisions of Sentence(1) apply whether or not the surface is provided with a means of drainage, such
as rainwater leaders.
3) Except as provided in Sentence4.1.6.2.(1), loads due to rain need not be considered to act simultaneously
with loads due to snow. (See NoteA-4.1.6.4.(3).)
4) Where scuppers are provided and where the position, shape and deflection of the loaded surface make an
accumulation of rainwater possible, the loads due to rain shall be the lesser of either the one-day rainfall determined
in conformance with Subsection1.1.3. or a depth of rainwater equal to 30mm above the level of the scuppers,
applied over the horizontal projection of the surface and tributary areas.
4.1.6.5. Multi-level Roofs
1) The drifting load of snow on a roof adjacent to a higher roof shall be taken as trapezoidal, as shown in
Figure4.1.6.5.-A, and the accumulation factor, C
a
, shall be determined as follows:
where
C
a0
= peak value of C
a
at x = 0 determined in accordance with Sentences(3) and(4) and
as shown in Figure4.1.6.5.-B,
x = distance from roof step as shown in Figure4.1.6.5.-A, and
x
d
= length of drift determined in accordance with Sentence(2) and as shown in Figure4.1.6.5.-A.
2) The length of the drift,
xd
, shall be calculated as follows:
where
= specific weight of snow as specified in Article4.1.6.13.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Figure 4.1.6.5.-A
Snow load factors for lower level roofs
Forming Part of Sentences 4.1.6.5.(1) and (3) and 4.1.6.6.(1)
Notes to Figure 4.1.6.5.-A:
(1) If a > 5 m or h ≤ 0.8S
s
/, drifting from the higher roof need not be considered.
(2) For lower roofs with parapets, Cs = 1.0, otherwise it varies as a function of slope α as defined in Sentences 4.1.6.2.(5) and (6).
EG01301B
x
d
= 5 (C
a0
-1)
x
h
α
h
α
a
Distribution of snow load, S
x
d
x = 10 h
′
h
p
C
b
S
s
γ
γh
C
b
S
s
F
C
b
C
a0
= the lesser of
β
1
and
C
b
C
w
S
s
γ
h′ = h –
1.0
f(α)
1.0
1.0
1.0 for non-exposed
roof areas
0.75 for exposed roof areas
0.5 for exposed roof areas
north of tree line
1.0
1.0
f(α)
f(α)
f(α)
C
w
C
s
(2)
C
a
Factors
(1)
C
a0
x
0
0 < x ≤ x
d
x
d
< x ≤ 10 h′
> 10 h′
C
a0
–
(
C
a0
– 1)
x
d
x
x
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
3) The value of C
a0
for each of CasesI, II, and III shall be the lesser of
where
= 1.0 for Case I, and 0.67 for Cases II and III,
h = difference in elevation between the lower roof surface and the top of the parapet on the upper roof as
shown in Figure4.1.6.5.-A, and
where
C
ws
=value of C
w
applicable to the source of drifting,
l
cs
= characteristic length of the source area for drifting, defined as , where w
s
and l
s
are
respectively the shorter and longer dimensions of the relevant source areas for snow drifting shown in
Figure4.1.6.5.-B for CasesI, II and III, and
where
h
p
= height of the roof perimeter parapet of the source area, to be taken as zero unless all the roof edges of
the source area have parapets.
4) The value of C
a0
shall be the highest of CasesI, II and III, considering the different roof source areas for
drifting snow, as specified in Sentence(3) and Figure4.1.6.5.-B.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Figure 4.1.6.5.-B
Snow load cases I, II and III for lower level roofs
Forming Part of Sentences 4.1.6.5.(1), (3) and (4)
4.1.6.6. Horizontal Gap between a Roof and a Higher Roof
1) Where the roof of one building is separated by a distance, a, from an adjacent building with a higher roof as
shown in Figure4.1.6.5.-A, the influence of the adjacent building on the value of the accumulation factor, C
a
, for the
lower roof shall be determined as follows:
a) if a > 5m, the influence of the adjacent building on C
a
for the lower roof can be ignored, and
b) if a ≤ 5m, C
a
for the lower roof shall be calculated in accordance with Article4.1.6.5. for values of x ≥ a.
Lower
Roof
Upper
Roof
source
area for
snow in
drift
length
of step
snow drift
Case I
Case II
Lower
roof
Upper
Roof
Snow drift
Source
area for
snow in
drift
Source
area for
snow in
drift
distance
to upwind
roof edge
h
Case III
Lower
Roof
Upper
Roof
snow drift
ROOF PLAN
EG01302B
source
area for
snow in
drift
Lower
Roof
source area for
snow in drift
1.0
0.67
parapet height of
upper-roof source
area
Case I
Case II Case III
0.67
Parameter
β
h
p
l
cs
=
2w
s
–
l
s
w
s
parapet height of
lower-roof source
area
with w
s
and l
s
being the shorter
and longer
dimensions of
the upper roof
with w
s
and l
s
being the shorter
and longer
dimensions of
source area on
lower roof for
upwind facing
step
with w
s
and l
s
being the shorter
and longer
dimensions of the
source area on
the lower roof for
downwind facing
step
parapet height of
lower-roof source
area
W
i
n
d
W
i
n
d
W
i
n
d
snow drift
2
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.6.7. Areas Adjacent to Roof Projections
1) Except as provided in Sentences(2) and(3), the accumulation factor, C
a
, for areas adjacent to roof-mounted
vertical projections shall be calculated in accordance with Sentence4.1.6.5.(1) using the following values for the peak
accumulation factor, C
a0
, and the drift length, x
d
:
a) C
a0
shall be taken as the lesser of
b) x
d
shall be taken as the lesser of 3.35h and (2/3)l
0
, where
h = height of the projection, and
l
0
= longest horizontal dimension of the projection.
(See NoteA-4.1.6.7.(1).)
2) C
a
is permitted to be calculated in accordance with Article4.1.6.5. for larger projections.
(SeeNoteA-4.1.6.7.(2).)
3) Where the longest horizontal dimension of the roof projection, l
0
, is less than 3m, the drift surcharge
adjacent to the projection need not be considered.
4.1.6.8. Snow Drift at Corners
1) The drift loads on the lower level roof against the two faces of an outside corner of an upper level roof or
roof obstruction shall be extended radially around the corner as shown in Figure4.1.6.8.-A and may be taken as the
least severe of the drift loads lying against the two faces of the corner.
2) The drift loads on the lower level roof against the two faces of an inside corner of an upper level roof or a
parapet shall be calculated for each face and applied as far as the bisector of the corner angle as shown in
Figure4.1.6.8.-B.
Figure 4.1.6.8.-A
Snow load at outside corner
Forming Part of Sentence 4.1.6.8.(1)
L
o
w
e
r
r
o
o
f
Upper roof
Face with
higher C
a0
radius of drift
surcharge = x
d
Face with
lower C
a0
x
d
Upper roof
Lower roof
EG01383B
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Figure 4.1.6.8.-B
Snow load at inside corner
Forming Part of Sentence 4.1.6.8.(2)
4.1.6.9. Gable Roofs
(See NoteA-4.1.6.9.)
1) For all gable roofs, the full and partial load cases defined in Article4.1.6.3. shall be considered.
2) For gable roofs with a slope > 15°, the unbalanced load case shall also be considered by setting the values
of the accumulation factor, C
a
, as follows:
a) on the upwind side of the roof peak, C
a
shall be taken as 0, and
b) on the downwind side of the roof peak, C
a
shall be taken as
i) 0.25 + /20, where 15° ≤ ≤ 20°, and
ii) 1.25, where 20° < ≤ 90°.
3) For all gable roofs, the slope factor, C
s
, shall be as prescribed in Sentences4.1.6.2.(5) and(6).
4) For all gable roofs, the wind exposure factor, C
w
, shall be
a) as prescribed in Sentences4.1.6.2.(3) and(4) for the full and partial load cases, and
b) 1.0 for the unbalanced load case referred to in Sentence(2).
4.1.6.10. Arch Roofs, Curved Roofs and Domes
1) For all arch roofs, curved roofs and domes, the full and partial load cases defined in Article4.1.6.3. shall be
considered.
2) For arch roofs, curved roofs and domes with a rise-to-span ratio h/b > 0.05 (see Figure4.1.6.10.-A), the load
cases provided in Sentences(3) to(7) shall also be considered.
Face with
higher C
a0
Lower roof
Upper roof
bisector of
angle between
two faces
EG01384B
Face with
lower C
a0
Lower roof
Upper roof
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
3) For arch roofs with a slope at the edge
e
≤ 30° (see Figure4.1.6.10.-A and Table4.1.6.10.), Ca shall be
a) taken as 0 on the upwind side of the peak, and
b) on the downwind side of the peak, taken as
where
x = horizontal distance from the roof peak,
h = height of arch, and
b = width of arch.
Figure 4.1.6.10.-A
Accumulation factors for arch roofs and curved roofs
Forming Part of Sentences 4.1.6.10.(2) to (4)
Note to Figure 4.1.6.10.-A:
(1) Refer to Table 4.1.6.10. for applicable values of C
w
and Sentences 4.1.6.2.(5) and (6) for applicable values of C
s
.
Case I,
balanced:
all values
of α
e
Case II,
unbalanced:
α
e
≤ 30˚
Case II,
unbalanced:
α
e
> 30˚
α = 30˚
b
x
30
α
e
= slope at edge
EG01307B
C
a
C
s
C
a
not slippery
C
s
C
a
slippery
C
a
C
s
C
a
not slippery
C
s
C
a
slippery
C
a
and
C
s
C
a
not slippery
C
s
C
a
slippery
h
x
15
α = 15˚
α = 30˚
α ≥ 30˚
α = 15˚
α ≥ 30˚
15˚ < α < 30˚
α < 15˚
15˚ < α < 30˚
α
wind
x
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4) For arch roofs with a slope at the edge
e
> 30° (see Figure4.1.6.10.-A and Table4.1.6.10.), C
a
shall be
a) taken as
on the upwind side of the peak, and
b) on the downwind side of the peak,
i) for the part of the roof between the peak and point where the slope = 30°, taken as
where
x, h, b = as specified in Sentence(2), and
x
30
= value of x where the slope = 30°, and
ii) for the part of the roof where the slope > 30°, taken as
5) Except as provided in Sentence(6), C
a
for curved roofs shall be determined in accordance with the
requirements for arch roofs stated in Sentences(3) and(4).
6) Where the slope, , of a curved roof at its peak is greater than 10°, C
a
shall be determined in accordance with
the requirements for gable roofs stated in Article4.1.6.9. using a slope equal to the mean slope of the curved roof.
Table 4.1.6.10.
Load Cases for Arch Roofs, Curved Roofs and Domes
Forming Part of Sentences 4.1.6.10.(3), (4) and (9)
Load Case Range of Application
Factors
All Arch or Curved
Roofs and Domes
Arch and Curved Roofs Domes
C
w
C
a
Upwind Side
C
a
Downwind Side
C
a
Downwind Side
Case I All values of h/b As stated in 4.1.6.2.(3)
and (4)
1.0 1.0 1.0
Case II Slope at edge ≤ 30°
h/b > 0.05
all values of x
1.0 0.0
Slope at edge > 30°
h/b > 0.05
0 < x < x30
1.0 0.0
Slope at edge >30°
h/b > 0.05
x ≥ x30
1.0 0.0
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
7) For domes of circular plan form (see Figure4.1.6.10.-B), C
a
shall
a) along the central axis parallel to the wind, vary in the same way as for an arch roof with the same rise-to-span
ratio, h/b, and
b) off this axis, vary according to
where
C
a
(x,y) = value of C
a
at location (x,y),
C
a
(x,0) = value of C
a
on the central axis parallel to the wind,
x = distance along the central axis parallel to the wind,
y = horizontal coordinate normal to the x direction, and
r = radius of dome.
8) For all arch roofs, curved roofs and domes, the slope factor, C
s
, shall be as prescribed in Sentences4.1.6.2.(5)
and(6).
9) For all arch roofs, curved roofs and domes, the wind exposure factor, C
w
, shall be as prescribed in
Table4.1.6.10.
Figure 4.1.6.10.-B
Unbalanced snow accumulation factor on a circular dome
Forming Part of Sentence 4.1.6.10.(7)
Notes to Figure 4.1.6.10.-B:
(1) Refer to Table 4.1.6.10. for applicable values of C
w
and Sentences 4.1.6.2.(5) and (6) for applicable values of C
s
.
(2) Refer to Sentences 4.1.6.10.(3) and (4) for the calculation of C
a
(x,0).
4.1.6.11. Snow Loads Due to Sliding
1) Except as provided in Sentence(2), where an upper roof, or part thereof, slopes downwards with a slope
>
towards a lower roof, the snow load, S, on the lower roof, determined in accordance with Articles4.1.6.2.
and4.1.6.5., shall be augmented in accordance with Sentence(3) to account for the additional load resulting from
sliding snow.
2) Sentence(1) need not apply where
a) snow from the upper roof is prevented from sliding by a parapet or other effective means, or
b) the upper roof is not considered slippery and has a slope of less than 20°.
EG01308B
Wind
C
a
(x,0)
r
y
x
y
r
C
a
(x,y) = C
a
(x,0)
(
1–
)
Plan View
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
3) The total weight of additional snow resulting from sliding shall be taken as half the total weight of snow
resulting from the uniform load case prescribed in Article4.1.6.2. with
a) the accumulation factor C
a
= 1.0 for the relevant part of the upper roof,
b) the slope factor, C
s
, based on the slope of the lower roof, as prescribed in Sentences4.1.6.2.(5) and(6), and
c) the sliding snow distributed on the lower roof such that it is a maximum for x = 0 and decreases linearly to
0at x=x
d
, as shown in Figure4.1.6.11., where x and x
d
are as defined in Article4.1.6.5.
Figure 4.1.6.11.
Snow distribution on lower roof with sloped upper roof
Forming Part of Sentence 4.1.6.11.(3)
4.1.6.12. Valleys in Curved or Sloped Roofs
1) For valleys in curved or sloped roofs with a slope > 10°, in addition to the full and partial load cases
defined in Article4.1.6.3., the non-uniform load cases II and III presented in Sentences(2) and(3) shall be
considered to account for sliding, creeping and movement of meltwater.
2) For case II (see Figure4.1.6.12.), the accumulation factor, C
a
, shall be calculated as follows:
where
x = horizontal distance from the bottom of the valley, and
b = twice the horizontal distance between the bottom of the valley and the peak of the roof surface in
question.
3) For case III (see Figure4.1.6.12.), C
a
shall be calculated as follows:
where
x, b = as specified in Sentence(2).
h
α
Distribution of snow load, S
sliding load
drift load
EG01309B
x
d
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
Figure 4.1.6.12.
Snow loads in valleys of sloped or curved roofs
Forming Part of Sentences 4.1.6.12.(2) and (3)
Notes to Figure 4.1.6.12.:
(1) C
w
= 1, as per Sentence 4.1.6.2.(3).
(2) C
s
= 1, as per Sentence 4.1.6.2.(7).
4.1.6.13. Specific Weight of Snow
1) For the purposes of calculating snow loads in drifts, the specific weight of snow, , shall be taken as
4.0kN/m
3
or 0.43SS + 2.2kN/m
3
, whichever is lesser.
4.1.6.14. Snow Removal
1) Snow removal by mechanical, thermal, manual or other means shall not be used as a rationale to reduce
design snow loads.
4.1.6.15. Ice Loading of Structures
1) For lattice structures connected to the building, and other building components or appurtenances involving
small width elements subject to significant ice accretion, the weight of ice accretion and the effective area presented
to wind shall be as prescribed in CSAS37, “Antennas, Towers, and Antenna-Supporting Structures.”
Case III
Case II
Case I
2
x
1
x
2
α
1
α
2
α
1
b
2
2
b
1
4
b
1
4
b
2
α
2
EG01310A
8
b
1
8
b
2
S = I
s
(S
s
+ S
r
)
S = I
s
(0.5S
s
+ S
r
)
S = I
s
(0.5S
s
+ S
r
)
S = I
s
(1.5S
s
+ S
r
)
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4.1.7. Wind Load
4.1.7.1. Specified Wind Load
1) The specified wind loads for a building and its components shall be determined using the Static, Dynamic or
Wind Tunnel Procedure as stated in Sentences(2) to(5).
2) For the design of buildings that are not dynamically sensitive, as defined in Sentence4.1.7.2.(1), one of the
following procedures shall be used to determine the specified wind loads:
a) the Static Procedure described in Article4.1.7.3.,
b) the Dynamic Procedure described in Article4.1.7.8., or
c) the Wind Tunnel Procedure described in Article4.1.7.12.
3) For the design of buildings that are dynamically sensitive, as defined in Sentence4.1.7.2.(2), one of the
following procedures shall be used to determine the specified wind loads:
a) the Dynamic Procedure described in Article4.1.7.8., or
b) the Wind Tunnel Procedure described in Article4.1.7.12.
4) For the design of buildings that may be subject to wake buffeting or channelling effects from nearby buildings,
or that are very dynamically sensitive, as defined in Sentence4.1.7.2.(3), the Wind Tunnel Procedure described in
Article4.1.7.12., shall be used to determine the specified wind loads.
5) For the design of cladding and secondary structural members, one of the following procedures shall be used
to determine the specified wind loads:
a) the Static Procedure described in Article4.1.7.3., or
b) the Wind Tunnel Procedure described in Article4.1.7.12.
6) Computational fluid dynamics shall not be used to determine the specified wind loads for a building and its
components. (See NoteA-4.1.7.1.(6).)
4.1.7.2. Classification of Buildings
1) Except as provided in Sentences(2) and(3), a building is permitted to be classified as not dynamically
sensitive.
2) A
building shall be classified as dynamically sensitive if
a) its lowest natural frequency is less than 1Hz and greater than 0.25Hz,
b) its height is greater than 60m, or
c) its height is greater than 4 times its minimum effective width, where the effective width, w, of a building shall
be taken as
where the summations are over the height of the building for a given wind direction, h
i
is the height above grade to leveli, and w
i
is the width normal to the wind direction at height h
i
; the minimum effective width is the lowest value of the effective width
considering all wind directions.
3) A building shall be classified as very dynamically sensitive if
a) its lowest natural frequency is less than or equal to 0.25Hz, or
b) its height is more than 6 times its minimum effective width as defined in Clause(2)(c).
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.7.3. Static Procedure
1) The specified external pressure or suction due to wind on part or all of a surface of a building shall be
calculated as follows:
where
p = specified external pressure acting statically and in a direction normal to the surface, considered positive
when the pressure acts towards the surface and negative when it acts away from the surface,
I
W
= importance factor for wind load, as provided in Table4.1.7.3.,
q = reference velocity pressure, as provided in Sentence(4),
C
e
= exposure factor, as provided in Sentences(5) and(7),
C
t
= topographic factor, as provided in Article4.1.7.4.,
C
g
= gust effect factor, as provided in Sentence(8), and
C
p
= external pressure coefficient, as provided in Articles4.1.7.5. and4.1.7.6.
2) The net wind load for the building as a whole shall be the algebraic difference of the loads on the windward
and leeward surfaces, and in some cases, may be calculated as the sum of the products of the external pressures or
suctions and the areas of the surfaces over which they are averaged as provided in Sentence(1).
3) The net specified pressure due to wind on part or all of a surface of a building shall be the algebraic difference,
such as to produce the most critical effect, of the external pressure or suction calculated in accordance with
Sentence(1) and the specified internal pressure or suction due to wind calculated as follows:
where
p
i
= specified internal pressure acting statically and in a direction normal to the surface, either as a pressure
directed towards the surface or as a suction directed away from the surface,
I
W
, q, C
t
= as defined in Sentence(1),
C
ei
= exposure factor for internal pressure, as provided in Sentence(7),
C
gi
= internal gust effect factor, as provided in Sentence(10), and
C
pi
= internal pressure coefficient, as provided in Article4.1.7.7.
4) The reference velocity pressure, q, shall be the appropriate value determined in conformance with
Subsection1.1.3., based on a probability of being exceeded in any one year of 1in50.
Table 4.1.7.3.
Importance Factor for Wind Load, I
W
Forming Part of Sentences 4.1.7.3.(1) and (3)
Importance Category
Importance Factor, I
W
ULS SLS
Low 0.8 0.75
Normal 1 0.75
High 1.15 0.75
Post-disaster 1.25 0.75
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
5) The exposure factor, C
e
, shall be based on the reference height, h, determined in accordance with
Sentence(6), for the surface or part of the surface under consideration and shall be
a) (h/10)
0.2
but not less than 0.9 for open terrain, where open terrain is level terrain with only scattered buildings,
trees or other obstructions, open water or shorelines thereof,
b) 0.7(h/12)
0.3
but not less than 0.7 for rough terrain, where rough terrain is suburban, urban or wooded terrain
extending upwind from the building uninterrupted for at least 1km or 20times the height of the building,
whichever is greater, or
c) an intermediate value between the two exposures defined in Clauses(a) and(b) in cases where the site is less
than 1km or 20times the height of the building from a change in terrain conditions, whichever is greater,
provided an appropriate interpolation method is used (see NoteA-4.1.7.3.(5)(c)).
6) The reference height, h, shall be determined as follows:
a) for buildings whose height is less than or equal to 20m and less than the smaller plan dimension, h shall be the
mid-height of the roof above grade, but not less than 6m,
b) for other buildings, h shall be
i) the actual height above grade of the point on the windward wall for which external pressures are being
calculated,
ii) the mid-height of the roof for pressures on surfaces parallel to the wind direction, and
iii) the mid-height of the building for pressures on the leeward wall, and
c) for any structural element exposed to wind, h shall be the mid-height of the element above the ground.
7) The exposure factor for internal pressures, C
ei
, shall be determined as follows:
a) for buildings whose height is greater than 20m and that have a dominant opening, C
ei
shall be equal to the
exposure factor for external pressures, C
e
, calculated at the mid-height of the dominant opening, and
b) for other buildings, C
ei
shall be the same as the exposure factor for external pressures, C
e
, calculated for a
reference height, h, equal to the mid-height of the building or 6m, whichever is greater.
8) Except as provided in Sentences(9) and4.1.7.6.(1), the gust effect factor, C
g
, shall be one of the following
values:
a) 2.0 for the building as a whole and main structural members, or
b) 2.5 for external pressures and suctions on secondary structural members, including cladding.
9) For cases where C
g
and C
p
are combined into a single product, C
p
C
g
, the values of C
p
and C
g
need not be
independently specified. (See Article4.1.7.6.)
10) The internal gust effect factor, C
gi
, shall be 2.0, except it is permitted to be calculated using the following
equation for large structures enclosing a single large unpartitioned volume that does not have numerous overhead
doors or openings:
where
V
0
= internal volume, in m
3
, and
A = total area of all exterior openings of the volume, in m
2
.
(See NoteA-4.1.7.3.(10).)
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.7.4. Topographic Factor
1) Except as provided in Sentence(2), the topographic factor, C
t
, shall be taken as 1.0.
2) For buildings on hills or escarpments with a slope, H
h
/(2L
h
), greater than 0.1 (see Figure4.1.7.4.), the
topographic factor, C
t
, shall be calculated as follows:
where
where
ΔS
max
= applicable value from Table4.1.7.4.,
x = horizontal distance from the peak of the hill or escarpment,
L
h
= horizontal distance upwind from the peak to the point where the ground surface lies at half the height
of the hill or escarpment, or 2H
h
(where H
h
= height of hill or escarpment), whichever is greater,
z = height above ground, and
k and = applicable constants from Table4.1.7.4. based on shape of hill or escarpment.
Figure 4.1.7.4.
Speed-up of mean velocity on a hill or escarpment
Forming Part of Sentence 4.1.7.4.(2)
Note to Figure 4.1.7.4.:
(1) V
(z)
= wind speed
V(z)
z
L
h
“speed-up”
ΔS·V(z)
H
h
x
Hill
z
V(z)
V(z)
z
L
h
ΔS·V(z)
x
Escarpment
z
V(z)
H
h
EG00915C
H
h
/2
H
h
/2
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4.1.7.5. External Pressure Coefficients
1) Applicable values of external pressure coefficients, C
p
, are provided in
a) Sentences(2) to(5), and
b) Article4.1.7.6. for certain shapes of low buildings.
2) For the design of the main structural system, the value of C
p
shall be established as follows, where H is the
height of the building and D is the width of the building parallel to the wind direction:
a) on the windward face,
C
p
=0.6 for H/D < 0.25
= 0.27(H/D + 2) for 0.25 ≤ H/D < 1.0, and
=0.8 for H/D ≥ 1.0,
b) on the leeward face,
C
p
= ?0.3 for H/D < 0.25,
= ?0.27(H/D + 0.88) for 0.25 ≤ H/D < 1.0, and
= ?0.5 for H/D ≥ 1.0, and
c) on the walls parallel to the wind, C
p
= –0.7.
(See NoteA-4.1.7.5.(2) and (3).)
3) For the design of roofs, the value of C
p
shall be established as follows, where x is the distance from the
upwind edge of the roof:
a) for H/D ≥ 1.0, C
p
= –1.0, and
b) for H/D < 1.0,
C
p
= –1.0 for x ≤ H, and
= –0.5 for x > H.
(See NoteA-4.1.7.5.(2) and (3).)
4) For the design of the cladding and of secondary structural elements supporting the cladding, the value of C
p
shall be established as follows, where W and D are the widths of the building:
a) on walls, C
p
shall be taken as ±0.9, except that within a distance equal to the larger of 0.1D and 0.1W from a
building corner, the negative value of C
p
shall be taken as ?1.2,
b) on walls where vertical ribs deeper than 1m are placed on the facade, C
p
shall be taken as ±0.9, except that,
within a distance equal to the larger of 0.2D and 0.2W from a building corner, the negative value of C
p
shall be
taken as ?1.4, and
Table 4.1.7.4.
Parameters for Maximum Speed-up Over Hills and Escarpments
Forming Part of Sentence 4.1.7.4.(2)
Shape of Hill or Escarpment ΔS
max
(1)
α
k
x < 0 x ≥ 0
2-dimensional hill 2.2 H
h
/L
h
31.51.5
2-dimensional escarpment 1.3 H
h
/L
h
2.5 1.5 4
3-dimensional axi-symmetrical hill 1.6 H
h
/L
h
41.51.5
Notes to Table4.1.7.4.:
(1) For H
h
/L
h
> 0.5, assume H
h
/L
h
= 0.5 and substitute 2 H
h
for L
h
in the equation for ΔS.
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
c) on roofs, C
p
shall be taken as ?1.0, except that
i) within a distance equal to the larger of 0.1D and 0.1W from a roof edge, C
p
shall be taken as ?1.5,
ii) in a zone that is within a distance equal to the larger of 0.2W and 0.2D from a roof corner, C
p
shall be
taken as ?2.3 but is permitted to be taken as ?2.0 for roofs with perimeter parapets that are higher than
1m, and
iii) on lower levels of flat stepped roofs, positive pressure coefficients established for the walls of the steps
apply for a distance b (see Figure4.1.7.6.-D for the definition of b).
(See NoteA-4.1.7.5.(4).)
5) For the design of balcony guards, the internal pressure coefficient, C
pi
, shall be taken as zero and the value of
C
p
shall be taken as ±0.9, except that within a distance equal to the larger of 0.1W and 0.1D from a building corner,
C
p
shall be taken as ±1.2.
4.1.7.6. External Pressure Coefficients for Low Buildings
1) For the design of buildings with a height, H, that is both less than or equal to 20m and less than the smaller
plan dimension, the values of the product of the pressure coefficient and gust factor, C
p
C
g
, provided in Sentences(2)
to(9) are permitted to be used.
2) For the design of the main structural system of the building, which is affected by wind pressures on more than
one surface, the values of C
p
C
g
are provided in Figure4.1.7.6.-A.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Figure 4.1.7.6.-A
External peak values of C
p
C
g
for primary structural actions arising from wind load acting simultaneously on all surfaces of low buildings
(H ≤ 20 m)
Forming Part of Sentence 4.1.7.6.(2)
Notes to Figure 4.1.7.6.-A:
(1) The building must be designed for all wind directions. Each corner must be considered in turn as the windward corner shown in the sketches.
For all roof slopes, Load Case A and Load Case B are required as two separate loading conditions to generate the wind actions, including
torsion, to be resisted by the structural system.
roof
slope
1E
1
2
2E
3
3E
4
4E
wind direction
range
Z
(7)
5
5E
6
6E
roof
slope
1E
1
2
2E
3
3E
4
4E
wind direction
range
y
(6)
Load Case A: winds generally perpendicular to ridge
0° to 5°
Roof Slope
Building Surfaces
Load Case B: winds generally parallel to ridge
B
H
2.5 H
(8)
reference
height, (h)
(5)
20°
30° to 45°
90°
0.75
1.0
1.05
1.05
1.15
1.5
1.3
1.3
-1.3
-1.3
0.4
1.05
-2.0
-2.0
0.5
1.3
-0.7
-0.7
-0.9
-0.8
-1.0
-1.0
-1.3
-0.9
-0.55
-0.8
-0.7
-0.7
-0.8
-1.2
-0.9
-0.9
y
(6)
1 1E 2 3E 4
4E
EG00920B
2E
3
0° to 90°
Roof Slope
Building Surfaces
-0.85 -0.9 -1.3 -2.0 -0.7 -1.0 -0.85 -0.9 0.75 1.15 -0.55 -0.8
1 1E 2 2E 3 3E 4 4E 5 5E 6 6E
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
(2) For values of roof slope not shown, the coefficient (C
p
C
g
) can be interpolated linearly.
(3) Positive coefficients denote forces toward the surface, whereas negative coefficients denote forces away from the surface.
(4) For the design of foundations, exclusive of anchorages to the frame, only 70% of the effective load is to be considered.
(5) The reference height, h, for pressures is the mid-height of the roof or 6 m, whichever is greater. The eave height, H, may be substituted for the
mid-height of the roof if the roof slope is less than 7°.
(6) End-zone width y should be the greater of 6 m or 2z, where z is the width of the gable-wall end zone defined for Load Case B below.
Alternatively, for buildings with frames, the end zone y may be the distance between the end and the first interior frame.
(7) End-zone width z is the lesser of 10% of the least horizontal dimension and 40% of height, H, but not less than 4% of the least horizontal
dimension or 1 m.
(8) For B/H > 5 in Load Case A, the listed negative coefficients on surfaces 2 and 2E should only be applied on an area whose width is 2.5H
measured from the windward eave. The pressures on the remainder of the windward roof should be reduced to the pressures for the
leeward roof.
3) For the design of individual walls and wall cladding, the values of C
p
C
g
are provided in Figure4.1.7.6.-B.
4) For the design of roofs with a slope less than or equal to 7°, the values of C
p
C
g
are provided in
Figure 4.1.7.6.-C.
5) For the design of flat roofs with steps in elevation, the values of C
p
C
g
are provided in Figure4.1.7.6.-D.
6) For the design of gabled or hipped, single-ridge roofs with a slope greater than 7°, the values of C
p
C
g
are
provided in Figure4.1.7.6.-E.
7) For the design of gabled, multi-ridge roofs, the values of C
p
C
g
are provided in
a) Figure4.1.7.6.-C for roofs with a slope less than or equal to 10°, and
b) Figure4.1.7.6.-F for roofs with a slope greater than 10°.
8) For monosloped roofs, the values of C
p
C
g
are provided in
a) Figure4.1.7.6.-C for roofs with a slope less than or equal to 3°, and
b) Figure4.1.7.6.-G for roofs with a slope greater than 3° and less than or equal to 30°.
9) For sawtooth roofs, the values of C
p
C
g
are provided in
a) Figure4.1.7.6.-C for roofs with a slope less than or equal to 10°, and
b) Figure4.1.7.6.-H for roofs with a slope greater than 10°.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Figure 4.1.7.6.-B
External peak values of C
p
C
g
on individual walls for the design of cladding and secondary structural members
Forming Part of Sentence 4.1.7.6.(3)
Notes to Figure 4.1.7.6.-B:
(1) These coefficients apply for any roof slope, α.
(2) End-zone width z is the lesser of 10% of the least horizontal dimension and 40% of height, H, but not less than 4% of the least horizontal
dimension or 1 m.
(3) Combinations of external and internal pressures must be evaluated to obtain the most severe loading.
(4) Positive coefficients denote forces toward the surface, whereas negative coefficients denote forces away from the surface. Each structural
element must be designed to withstand forces of both signs.
(5) Pressure coefficients generally apply for facades with architectural features; however, where vertical ribs deeper than 1 m are placed on a
facade, a local C
p
C
g
of –2.8 applies to zone e.
H
z
z
z
z
α
e
e
e
w
w
e
EG00921B
reference
height, h
w
e
e
w
2.0
1.0
0
-1.0
-2.0
-3.0
C
p
C
g
and
Tributary Area, m
2
1 2 5 10 20 50 100
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
Figure 4.1.7.6.-C
External peak values of C
p
C
g
on roofs with a slope of 7° or less for the design of structural components and cladding
Forming Part of Sentences 4.1.7.6.(4), (7), (8) and (9)
Notes to Figure 4.1.7.6.-C:
(1) Coefficients for overhung roofs have the prefix “o” and refer to the same roof areas as referred to by the corresponding symbol without a prefix.
They include contributions from both upper and lower surfaces. In the case of overhangs, the walls are inboard of the roof outline.
(2) s and r apply to both roofs and upper surfaces of canopies.
(3) End-zone width z is the lesser of 10% of the least horizontal dimension and 40% of height, H, but not less than 4% of the least horizontal
dimension or 1 m.
(4) Combinations of external and internal pressures must be evaluated to obtain the most severe loading.
(5) Positive coefficients denote forces toward the surface, whereas negative coefficients denote forces away from the surface. Each structural
element must be designed to withstand forces of both signs.
(6) For calculating the uplift forces on tributary areas larger than 100 m
2
on unobstructed nearly-flat roofs with low parapets, and where the centre
of the tributary area is at least twice the height of the building from the nearest edge, the value of C
p
C
g
may be reduced from –1.5 to –1.1 at
x/H = 2 and further reduced linearly to –0.6 at x/H = 5, where x is the distance to the nearest edge and H is the height of the building.
(7) For roofs having a perimeter parapet with a height of 1 m or greater, the corner coefficients C
p
C
g
for tributary areas less than 1 m
2
can be
reduced from –5.4 to –4.4.
0
-1.0
-2.0
-3.0
-4.0
2
5102050100
(6)
-5.0
-6.0
r
s r c
1.0
z
z
zz
s
r r
H
α
0° < α ≤ 7°
c
oc
c
os
or
EG00922C
reference
height, h
roof with overhang
roof without overhang
Tributary Area, m
2
C
p
C
g
(7)
(2)
(1,7)
(1)
s
(2)
1
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Figure 4.1.7.6.-D
External peak values of C
p
C
g
for the design of the structural components and cladding of buildings with stepped roofs
Forming Part of Sentence 4.1.7.6.(5)
Notes to Figure 4.1.7.6.-D:
(1) The zone designations, pressure-gust coefficients and notes provided in Figure 4.1.7.6.-C apply on both the upper and lower levels of flat
stepped roofs, except that on the lower levels, positive pressure-gust coefficients equal to those in Figure 4.1.7.6.-B for walls apply for a
distance, b, where b is equal to 1.5h
1
but not greater than 30 m. For all walls in Figure 4.1.7.6.-D, zone designations and pressure coefficients
provided for walls in Figure 4.1.7.6.-B apply.
(2) Note (1) above applies only when the following conditions are met: h
1
≥ 0.3H, h
1
≥ 3 m, and W
1
, W
2
, or W
3
is greater than 0.25W but not greater
than 0.75W.
b
h
1
h
2
H
W
1
W
2
W
b
W
1
W
2
W
b
h
1
h
2
H
W
3
EG00923A
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
Figure 4.1.7.6.-E
External peak values of C
p
C
g
on single-span gabled and hipped roofs with a slope greater than 7° for the design of structural
components and cladding
Forming Part of Sentence 4.1.7.6.(6)
Notes to Figure 4.1.7.6.-E:
(1) Coefficients for overhung roofs have the prefix “o” and refer to the same roof areas as referred to by the corresponding symbol without a prefix.
They include contributions from both upper and lower surfaces.
(2) End-zone width z is the lesser of 10% of the least horizontal dimension and 40% of height, H, but not less than 4% of the least horizontal
dimension or 1 m.
(3) Combinations of external and internal pressures must be evaluated to obtain the most severe loading.
(4) Positive coefficients denote forces towards the surface, whereas negative coefficients denote forces away from the surface. Each structural
element must be designed to withstand forces of both signs.
(5) For hipped roofs with 7° < α ≤ 27°, edge/ridge strips and pressure-gust coefficients for ridges of gabled roofs apply along each hip.
z
z
z
z z
s
s
r r
11 0 100 0.1
2.0
1.0
0.0
-1.0
-2.0
-3.0
-4.0
-5.0
-6.0
-7.0
-8.0
H
reference
height, h
α
7° < α ≤ 45°
C
p
C
g
C
p
C
g
Tributary Area, m
2
Tributary Area, m
2
gable roofs
gable and hip roofs
11 0 100 0.1
2.0
1.0
0.0
-1.0
-2.0
-3.0
-4.0
-5.0
-6.0
-7.0
-8.0
α
r
s
c
roof with overhang
roof without overhang
h
z
z
r
s
oc
os
or
r
s
oc
os
c
s r c
s r c
7° < α ≤ 27°
27° < α ≤ 45°
7° < α ≤ 27°
C
or
EG00924D
c
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Figure 4.1.7.6.-F
External peak values of C
p
C
g
on multi-span gabled (folded) roofs with a slope greater than 10° for the design of structural components
and cladding
Forming Part of Sentence 4.1.7.6.(7)
Notes to Figure 4.1.7.6.-F:
(1) End-zone width z is the lesser of 10% of the least horizontal dimension and 40% of height, H, but not less than 4% of the least horizontal
dimension or 1 m.
(2) Combinations of external and internal pressures must be evaluated to obtain the most severe loading.
(3) Positive coefficients denote forces towards the surface, whereas negative coefficients denote forces away from the surface. Each structural
element must be designed to withstand forces of both signs.
(4) For α ≤ 10°, the coefficients given in Figure 4.1.7.6.-C apply, but for cases where α > than 7°, use α = 7°.
Tributary Area, m
2
Tributary Area, m
2
30° < α ≤ 45°
H
α
z
z
zzz z
s'
s
c
rr
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
0.1 1 10 100
c
s
s
r
C
p
C
g
'
s r c
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
0.1 1 10 100
C
p
C
g
s
'
s
s r c
c
r
r
α
H
EG00925B
reference
height, h
reference
height, h
10° < α ≤ 30°
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
Figure 4.1.7.6.-G
External peak values of C
p
C
g
on monoslope roofs for the design of structural components and cladding
Forming Part of Sentence 4.1.7.6.(8)
Notes to Figure 4.1.7.6.-G:
(1) End-zone width z is the lesser of 10% of the least horizontal dimension and 40% of height, H, but not less than 4% of the least horizontal
dimension or 1 m.
(2) Combinations of external and internal pressures must be evaluated to obtain the most severe loading.
(3) Positive coefficients denote forces towards the surface, whereas negative coefficients denote forces away from the surface. Each structural
element must be designed to withstand forces of both signs.
(4) For α ≤ 3°, the coefficients given in Figure 4.1.7.6.-C apply.
3°< α ≤ 10°
α
H
10° < α ≤ 30°
H
α
4z
2z 2z
2z
z
c
'
c
r
s
'
s
c
'
'
s
'
s
c
4z
2z
z
z
z
c
'
r
s
s
c
'
s
C
p
C
g
s
r
c
'
all regions
1
0
-1
-3
-2
-4
-5
-6
21050
1
5 20 100
C
p
C
g
'
s
s
r
c
c
'
all regions
1
0
-1
-3
-2
-4
-5
-6
21050
1
5 20 100
Tributary Area, m
2
reference
height, h
Tributary Area, m
2
reference
height, h
EG00926B
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Figure 4.1.7.6.-H
External peak values of C
p
C
g
on sawtooth roofs with a slope greater than 10° for the design of structural components and cladding
Forming Part of Sentence 4.1.7.6.(9)
Notes to Figure 4.1.7.6.-H:
(1) End-zone width z is the lesser of 10% of the least horizontal dimension and 40% of height, H, but not less than 4% of the least horizontal
dimension or 1 m.
(2) Combinations of external and internal pressures must be evaluated to obtain the most severe loading.
(3) Positive coefficients denote forces towards the surface, whereas negative coefficients denote forces away from the surface. Each structural
element must be designed to withstand forces of both signs.
(4) Negative coefficients on the corner zones of Span A differ from those on Spans B, C, and D.
(5) For α ≤ 10°, the coefficients given in Figure 4.1.7.6.-C apply, but for cases where α > than 7°, use α = 7°.
4.1.7.7. Internal Pressure Coefficient
1) The internal pressure coefficient, C
pi
, shall be as prescribed in Table4.1.7.7.
Table 4.1.7.7.
Internal Pressure Coefficients
Forming Part of Sentence 4.1.7.7.(1)
Building Openings Values for C
pi
Uniformly distributed small openings amounting to less than 0.1% of the total surface area of the
building
–0.15 to 0.0
Non-uniformly distributed openings of which none is significant or significant openings that are
wind-resistant and closed during storms
–0.45 to +0.30
Large openings likely to remain open during storms –0.70 to +0.70
Tributary Area, m
2
C
p
C
g
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
-8
EG00927C
1
2
5
10 20
50
100
H
2z
2z
z
c
r
s
s
z
z
zz
α
w/2
w/2
reference
height, h
10° < α < 30°
s
A B D
c
span A
r
c
spans B,C,D
r
c
s
C
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.7.8. Dynamic Procedure
1) For the application of the Dynamic Procedure, the provisions of Article4.1.7.3. shall be followed, except that
the exposure factor, C
e
, shall be as prescribed in Sentences(2) and(3), and the gust effect factor, C
g
, shall be as
prescribed in Sentence(4), when determining the wind loads on the main structural system.
2) For buildings in open terrain, as defined in Clause4.1.7.3.(5)(a), the value of C
e
for the design of the main
structural system shall be calculated as follows:
(See NoteA-4.1.7.8.(2) and (3).)
3) For buildings in rough terrain, as defined in Clause4.1.7.3.(5)(b), the value of C
e
for the design of the main
structural system shall be calculated as follows:
(See NoteA-4.1.7.8.(2) and (3).)
4) For the design of the main structural system, C
g
shall be calculated as follows:
where
g
p
= peak factor calculated as , and
/μ =,
where
= average fluctuation rate calculated as ,
T = 3 600 s,
K = 0.08 for open terrain and 0.10 for rough terrain,
C
eH
= exposure factor evaluated at reference height h = H,
B = background turbulence factor, a function of w/H determined from Figure4.1.7.8.,
s = size reduction factor calculated as ,
F = gust energy ratio calculated as , where x
0
= (1 220 f
n
/V
H
), and
= damping ratio, which shall be determined by a rational method, or may be taken to be 0.01 for steel
structures, 0.02 for concrete structures, and 0.015 for composite structures,
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
where
f
nD
= natural frequency of vibration of the building in the along-wind direction, in Hz,
f
n
= lowest natural frequency of the building, in Hz, as defined in Sentences4.1.7.2.(2) and(3),
H = height of the building,
w = effective width of windward face of the building calculated as , where w
i
= width normal to
wind direction at height h
i
, and
V
H
= mean wind speed at the top of the structure, in m/s, calculated as ,
where
V = reference wind speed at a height of 10 m, in m/s, calculated as ,
where
I
W
= importance factor,
q = reference velocity pressure, in Pa, and
= air density = 1.2929 kg/m
3
.
(See NoteA-4.1.7.8.(4).)
Figure 4.1.7.8.
Background turbulence factor, B
Forming Part of Sentence 4.1.7.8.(4)
1
2
3
4
5
6
8
10
20
30
40
50
60
80
100
200
300
400
Background Turbulence Factor, B
Height of Structure, m
B = 4/3
914/H
1 +
xH
457
1
1 +
xw
122
1
x
0
w/H
0
0.1
0.2
0.3
0.5
0.7
1.0
1.5
2.0
3.0
5.0
dx
(1 + x
2
)
4/3
EG00916B
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
0
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.7.9. Full and Partial Wind Loading
1) Except where the wind loads are derived from the combined C
p
C
g
values determined in accordance with
Article4.1.7.6., buildings and structural members shall be capable of withstanding the effects of the following loads:
a) the full wind loads acting along each of the 2 principal horizontal axes considered separately,
b) the wind loads described in Clause(a) but with 100% of the load removed from any one portion of the area,
c) the wind loads described in Clause(a) but with both axes considered simultaneously at 75% of their full
value, and
d) the wind loads described in Clause(c) but with 50% of these loads removed from any portion of the area.
(See NoteA-4.1.7.9.(1).)
4.1.7.10. Interior Walls and Partitions
1) In the design of interior walls and partitions, due consideration shall be given to differences in air pressure on
opposite sides of the wall or partition which may result from
a) pressure differences between the windward and leeward sides of a building,
b) stack effects due to a difference in air temperature between the exterior and interior of the building, and
c) air pressurization by the mechanical services of the building.
4.1.7.11. Exterior Ornamentations, Equipment and Appendages
(See NoteA-4.1.7.11.)
1) The effects of wind loads on exterior ornamentations, equipment and appendages, including the increase in
exposed area as a result of ice buildup as prescribed in CSAS37, “Antennas, Towers, and Antenna-Supporting
Structures,” shall be considered in the structural design of the connections and the building.
2) Where there are a number of similar components, the net increase in force is permitted to be based on the
total area for all similar components as opposed to the summation of forces of individual elements.
4.1.7.12. Wind Tunnel Procedure
1) Except as provided in Sentences(2) and(3), wind tunnel tests on scale models to determine wind loads on
buildings shall be conducted in accordance with ASCE/SEI49, “Wind Tunnel Testing for Buildings and
Other Structures.”
2) Where an adjacent building provides substantial sheltering effect, the wind loads for the main structural system
shall be no lower than 80% of the loads determined from tests referred to in Sentence(1) with the effect of the
sheltering building removed as applied to
a) the base shear force for buildings
with a ratio of height to minimum effective width, as defined in
Sentence4.1.7.2.(2), less than or equal to 1.0, or
b) the base moment for buildings with a ratio of height to minimum effective width greater than 1.0.
3) For the design of cladding and secondary structural members, the exterior wind loads determined from the
wind tunnel tests shall be no less onerous than those determined by analysis in accordance with Article4.1.7.3. using
the following assumptions:
a) C
p
= ±0.72 and C
g
= 2.5, where the building’s height is greater than 20m or greater than its minimum effective
width, and
b) C
p
C
g
= 80% of the values for zones w and r provided in Article4.1.7.6., where the building’s height is less than
or equal to 20m and no greater than its minimum effective width.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4.1.8. Earthquake Load and Effects
4.1.8.1. Analysis
1) Except as permitted in Sentence(2), the deflections and specified loading due to earthquake motions shall be
determined according to the requirements of Articles4.1.8.2. to4.1.8.22.
2) Where I
E
F
s
S
a
(0.2) and I
E
F
s
S
a
(2.0) are less than 0.16 and 0.03 respectively, the deflections and specified
loading due to earthquake motions are permitted to be determined in accordance with Sentences(3) to(15), where
a) I
E
is the earthquake importance factor and has a value of 0.8, 1.0, 1.3 and 1.5 for buildings of Low, Normal,
High and Post-Disaster importance respectively,
b) F
s
is the site coefficient based on the average N
60
or S
u
, as defined in Article4.1.8.2., for the top 30m of soil
below the footings, pile caps, or mat foundations and has a value of
i) 1.0 for rock sites or when N
60
> 50 or S
u
> 100kPa,
ii) 1.6 when 15 ≤ N
60
≤ 50 or 50kPa ≤ S
u
≤ 100kPa, and
iii) 2.8 for all other cases, and
c) S
a
(T) is the 5% damped spectral response acceleration value for period T, determined in accordance with
Subsection1.1.3.
3) The structure shall have a clearly defined
a) Seismic Force Resisting System (SFRS) to resist the earthquake loads and their effects, and
b) load path (or paths) that will transfer the inertial forces generated by the earthquake to the foundations and
supporting ground.
4) An unreinforced masonry SFRS shall not be permitted where
a) I
E
is greater than 1.0, or
b) the height above grade is greater than or equal to 30m.
5) The height above grade of SFRS designed in accordance with CSAS136, “North American Specification for
the Design of Cold-Formed Steel Structural Members,” shall be less than 15m.
6) Earthquake forces shall be assumed to act horizontally and independently about any two orthogonal axes.
7) The minimum lateral earthquake design force, V
s
, at the base of the structure in the direction under
consideration shall be calculated as follows:
where
S
a
(T
s
)=value of S
a
at T
s
determined by linear interpolation between the value of S
a
at 0.2 s, 0.5 s, and 1.0 s, and
=S
a
(0.2) for T
s
≤ 0.2 s,
W
t
=sum of W
i
over the height of the building, where W
i
is defined in Article4.1.8.2., and
R
s
= 1.5, except R
s
= 1.0 for structures where the storey strength is less than that in the storey above and for an
unreinforced masonry SFRS,
where
T
s
= fundamental lateral period of vibration of the building, as defined in Article4.1.8.2.,
= 0.085(h
n
)
¾
for steel moment frames,
= 0.075(h
n
)
¾
for concrete moment frames,
= 0.1 N for other moment frames,
= 0.025h
n
for braced frames, and
=0.05(h
n
)
¾
for shear walls and other structures,
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
where
h
n
= height above the base, in m, as defined in Article4.1.8.2.,
except that V
s
shall not be less than F
s
S
a
(1.0)I
E
W
t
/R
s
and, in cases where R
s
=1.5, V
s
need not be greater than
F
s
S
a
(0.5)I
E
W
t
/R
s
.
8) The total lateral earthquake design force, V
s
, shall be distributed over the height of the building in accordance
with the following formula:
where
F
x
= force applied through the centre of mass at level x,
W
x
, W
i
portion of W that is located at or is assigned to level x or i respectively, and
h
x
, h
i
= height, in m, above the base of level x and leveli as per Article4.1.8.2.
9) Accidental torsional effects applied concurrently with F
x
shall be considered by applying torsional moments
about the vertical axis at each level for each of the following cases considered separately:
a) +0.1D
nx
F
x
, and
b) ?0.1D
nx
F
x
.
10) Deflections obtained from a linear analysis shall include the effects of torsion and be multiplied by R
s
/I
E
to
get realistic values of expected deflections.
11) The deflections referred to in Sentence(10) shall be used to calculate the largest interstorey deflection, which
shall not exceed
a) 0.01h
s
for post-disaster buildings,
b) 0.02h
s
for High Importance Category buildings, and
c) 0.025h
s
for all other buildings,
where h
s
is the interstorey height as defined in Article4.1.8.2.
12) When earthquake forces are calculated using R
s
= 1.5, the following elements in the SFRS shall have their
design forces due to earthquake effects increased by 33%:
a) diaphragms and their chords, connections, struts and collectors,
b) tie downs in wood or drywall shear walls,
c) connections and anchor bolts in steel- and wood-braced frames,
d) connections in precast concrete, and
e) connections in steel moment frames.
13) Except as provided in Sentence(14), where cantilever parapet walls, other cantilever walls, exterior
ornamentation and appendages, towers, chimneys or penthouses are connected to or form part of a building, they
shall be designed, along with their connections, for a lateral force, V
sp
, distributed according to the distribution of
mass of the element and acting in the lateral direction that results in the most critical loading for design using the
following equation:
where W
p
= weight of a portion of a structure as defined in Article4.1.8.2.
14) The value of V
sp
shall be doubled for unreinforced masonry elements.
15) Structures designed in accordance with this Article need not comply with the seismic requirements stated in
the applicable design standard referenced in Section4.3.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4.1.8.2. Notation
1) In this Subsection
A
r
= response amplification factor to account for type of attachment of mechanical/electrical equipment, as
defined in Sentence4.1.8.18.(1),
A
x
= amplification factor at level x to account for variation of response of mechanical/electrical equipment
with elevation within the building, as defined in Sentence4.1.8.18.(1),
B
x
= ratio at level x used to determine torsional sensitivity, as defined in Sentence4.1.8.11.(10),
B = maximum value of B
x
, as defined in Sentence4.1.8.11.(10),
C
p
= seismic coefficient for mechanical/electrical equipment, as defined in Sentence4.1.8.18.(1),
D
nx
= plan dimension of the building at level x perpendicular to the direction of seismic loading being
considered,
e
x
= distance measured perpendicular to the direction of earthquake loading between centre of mass and
centre of rigidity at the level being considered (see NoteA-4.1.8.2.(1)),
F
a
= site coefficient for application in Subsection4.1.8., as defined in Sentence4.1.8.4.(7),
F(PGA) = site coefficient for PGA, as defined in Sentence4.1.8.4.(5),
F(PGV) = site coefficient for PGV, as defined in Sentence4.1.8.4.(5),
F
s
= site coefficient as defined in Sentence4.1.8.1.(2) for application in Article4.1.8.1.,
F(T) = site coefficient for spectral acceleration, as defined in Sentence4.1.8.4.(5),
F
t
= portion of V to be concentrated at the top of the structure, as defined in Sentence4.1.8.11.(7),
F
v
= site coefficient for application in Subsection4.1.8., as defined in Sentence4.1.8.4.(7),
F
x
= lateral force applied to level x, as defined in Sentence4.1.8.11.(7),
h
i
, h
n
, h
x
= the height above the base (i = 0) to level i, n, or x respectively, where the base of the structure is the
level at which horizontal earthquake motions are considered to be imparted to the structure,
h
s
=interstorey height (h
i
- h
i
-1),
I
E
= earthquake importance factor of the structure, as described in Sentence4.1.8.5.(1),
J = numerical reduction coefficient for base overturning moment, as defined in Sentence4.1.8.11.(6),
J
x
= numerical reduction coefficient for overturning moment at level x, as defined in Sentence4.1.8.11.(8),
Level i = any level in the building, i = 1 for first level above the base,
Level n = level that is uppermost in the main portion of the structure,
Level x = level that is under design consideration,
M
v
= factor to account for higher mode effect on base shear, as defined in Sentence4.1.8.11.(6),
M
x
= overturning moment at level x, as defined in Sentence4.1.8.11.(8),
N = total number of storeys above exterior grade to level n,
N
60
= Average Standard Penetration Resistance for the top 30m, corrected to a rod energy efficiency of 60%
of the theoretical maximum,
PGA = Peak Ground Acceleration expressed as a ratio to gravitational acceleration, as defined in
Sentence4.1.8.4.(1),
PGA
ref
= reference PGA for determining F(T), F(PGA) and F(PGV), as defined in Sentence4.1.8.4.(4),
PGV = Peak Ground Velocity, in m/s, as defined in Sentence4.1.8.4.(1),
PI = plasticity index for clays,
R
d
= ductility-related force modification factor reflecting the capability of a structure to dissipate energy
through reversed cyclic inelastic behaviour, as given in Article4.1.8.9.,
R
o
= overstrength-related force modification factor accounting for the dependable portion of reserve
strength in a structure designed according to these provisions, as defined in Article4.1.8.9.,
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
R
s
= combined overstrength and ductility-related modification factor, as defined in Sentence4.1.8.1.(7), for
application in Article4.1.8.1.,
S
p
= horizontal force factor for part or portion of a building and its anchorage, as given in
Sentence4.1.8.18.(1),
S(T) = design spectral response acceleration, expressed as a ratio to gravitational acceleration, for a period of
T, as defined in Sentence4.1.8.4.(9),
S
a
(T) = 5% damped spectral response acceleration, expressed as a ratio to gravitational acceleration, for a
period of T, as defined in Sentence4.1.8.4.(1),
SFRS = Seismic Force Resisting System(s) is that part of the structural system that has been considered in the
design to provide the required resistance to the earthquake forces and effects defined in
Subsection4.1.8.,
s
u
= average undrained shear strength in the top 30m of soil,
T = period in seconds,
T
a
= fundamental lateral period of vibration of the building or structure, in s, in the direction under
consideration, as defined in Sentence4.1.8.11.(3),
T
s
= fundamental lateral period of vibration of the building or structure, in s, in the direction under
consideration, as defined in Sentence4.1.8.1.(7),
T
x
= floor torque at level x, as defined in Sentence4.1.8.11.(11),
TDD = Total Design Displacement of any point in a seismically isolated structure, within or above the
isolation system, obtained by calculating the mean + (I
E
× the standard deviation) of the peak
horizontal displacements from all sets of ground motion histories analyzed, but not less than √I
E
× the
mean, where the peak horizontal displacement is based on the vector sum of the two orthogonal
horizontal displacements considered for each time step,
V = lateral earthquake design force at the base of the structure, as determined by Article4.1.8.11.,
V
d
= lateral earthquake design force at the base of the structure, as determined by Article4.1.8.12.,
V
e
= lateral earthquake elastic force at the base of the structure, as determined by Article4.1.8.12.,
V
ed
= lateral earthquake design elastic force at the base of the structure, as determined by Article4.1.8.12.,
V
p
= lateral force on a part of the structure, as determined by Article4.1.8.18.,
V
s
= lateral earthquake design force at the base of the structure, as determined by Sentence4.1.8.1.(7), for
application in Article4.1.8.1.,
V
s30
= average shear wave velocity in the top 30m of soil or rock,
W=dead load, as defined in Article4.1.4.1., except that the minimum partition load as defined in
Sentence4.1.4.1.(3) need not exceed 0.5kPa, plus 25% of the design snow load specified in
Subsection4.1.6., plus 60% of the storage load for areas used for storage, except that storage garages need
not be considered storage areas, and the full contents of any tanks (seeNoteA-4.1.8.2.(1)),
W
i
, W
x
= portion of W that is located at or is assigned to level i or x respectively,
W
p
= weight of a part or portion of a structure, e.g., cladding, partitions and appendages,
W
t
=sum of W
i
over the height of the building, for application in Sentence4.1.8.1.(7),
ave
= average displacement of the structure at level x, as defined in Sentence4.1.8.11.(10), and
max
= maximum displacement of the structure at level x, as defined in Sentence4.1.8.11.(10).
4.1.8.3. General Requirements
1) Except as provided in Sentence (9), t
he building shall be designed to meet the requirements of this Subsection
and of the design standards referenced in Section4.3.
2) Structures shall be designed with a clearly defined load path, or paths, that will transfer the inertial forces
generated in an earthquake to the supporting ground.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
3) The structure shall have a clearly defined Seismic Force Resisting System(s) (SFRS), as defined in
Article4.1.8.2.
4) The SFRS shall be designed to resist 100% of the earthquake loads and their effects. (See NoteA-4.1.8.3.(4).)
5) All structural framing elements not considered to be part of the SFRS must be investigated and shown to
behave elastically or to have sufficient non-linear capacity to support their gravity loads while undergoing
earthquake-induced deformations calculated from the deflections determined in Article4.1.8.13.
6) Stiff elements that are not considered part of the SFRS, such as concrete, masonry, brick or precast walls or
panels, shall be
a) separated from all structural elements of the building such that no interaction takes place as the building
undergoes deflections due to earthquake effects as calculated in this Subsection, or
b) made part of the SFRS and satisfy the requirements of this Subsection.
(See NoteA-4.1.8.3.(6).)
7) Stiffness imparted to the structure from elements not part of the SFRS, other than those described in
Sentence(6), shall not be used to resist earthquake deflections but shall be accounted for
a) in calculating the period of the structure for determining forces if the added stiffness decreases the
fundamental lateral period by more than 15%,
b) in determining the irregularity of the structure, except the additional stiffness shall not be used to make an
irregular SFRS regular or to reduce the effects of torsion (see NoteA-4.1.8.3.(7)(b) and (c)), and
c) in designing the SFRS if inclusion of the elements not part of the SFRS in the analysis has an adverse effect
on the SFRS (see NoteA-4.1.8.3.(7)(b) and (c)).
8) Structural modelling shall be representative of the magnitude and spatial distribution of the mass of the
building and of the stiffness of all elements of the SFRS, including stiff elements that are not separated in accordance
with Sentence4.1.8.3.(6), and shall account for
a) the effect of cracked sections in reinforced concrete and reinforced masonry elements,
b) the effect of the finite size of members and joints,
c) sway effects arising from the interaction of gravity loads with the displaced configuration of the structure,
and
d) other effects that influence the lateral stiffness of the building.
(See NoteA-4.1.8.3.(8).)
9) Notwithstanding the requirement stated in Sentence 4.3.1.1.(1), Update 1 to CSA O86-14 is not permitted to
be used in the application of Subsection 4.1.8.
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.8.4. Site Properties
1) The peak ground acceleration (PGA), peak ground velocity (PGV), and the 5% damped spectral response
acceleration values, S
a
(T), for the reference ground conditions (Site Class C in Table4.1.8.4.-A) for periods T of 0.2 s,
0.5 s, 1.0 s, 2.0 s, 5.0 s and 10.0 s shall be determined in accordance with Subsection1.1.3. and are based on a
2% probability of exceedance in 50 years.
2) Site classifications for ground shall conform to Table4.1.8.4.-A and shall be determined using V
s30
, or where
V
s30
is not known, using Sentence(3).
3) If average shear wave velocity, V
s30,
is not known, Site Class shall be determined from energy-corrected
Average Standard Penetration Resistance, N
60
, or from soil average undrained shear strength, s
u
, as noted in
Table4.1.8.4.-A, N
60
and s
u
being calculated based on rational analysis. (See NoteA-4.1.8.4.(3) and Table 4.1.8.4.-A.)
4) For the purpose of determining the values of F(T) to be used in the calculation of design spectral
acceleration, S(T), in Sentence(9), and the values of F(PGA) and F(PGV), the value of PGA
ref
to be used with
Tables4.1.8.4.-B to4.1.8.4.-I shall be taken as
a) 0.8 PGA, where the ratio S
a
(0.2)/PGA < 2.0, and
b) PGA, otherwise.
5) The values of the site coefficient for design spectral acceleration at period T, F(T), and of similar coefficients
F(PGA) and F(PGV) shall conform to Tables4.1.8.4.-B to4.1.8.4.-I using linear interpolation for intermediate values
of PGAref.
6) Site-specific evaluation is required to determine F(T), F(PGA) and F(PGV) for Site Class F.
(SeeNoteA-4.1.8.4.(3) and Table 4.1.8.4.-A.)
7) For all applications in Subsection4.1.8., F
a
= F(0.2) and F
v
= F(1.0).
Table 4.1.8.4.-A
Site Classification for Seismic Site Response
Forming Part of Sentences 4.1.8.4.(1) to (3)
Site Class Ground Profile Name
Average Properties in Top 30m, as per NoteA-4.1.8.4.(3) and Table 4.1.8.4.-A
Average Shear Wave Velocity,
V
s30
, m/s
Average Standard Penetration
Resistance,
N
60
Soil Undrained Shear
Strength, s
u
A Hard rock
(1)(2)
V
s30
> 1500 n/a n/a
B Rock
(1)
760 < V
s30
≤ 1500 n/a n/a
C Very dense soil and soft rock 360 < V
s30
< 760 N
60
> 50 s
u
> 100 kPa
DStiff soil 180 < V
s30
< 360 15 ≤ N
60
≤ 50 50 kPa < s
u
≤ 100 kPa
E Soft soil V
s30
< 180 N
60
< 15 s
u
< 50 kPa
Any profile with more than 3 m of soil with the following characteristics:
• plasticity index: PI > 20
• moisture content: w ≥ 40%, and
• undrained shear strength: s
u
< 25 kPa
FOther soils
(3)
Site-specific evaluation required
Notes to Table4.1.8.4.-A:
(1) Site Classes A and B, hard rock and rock, are not to be used if there is more than 3 m of softer materials between the rock and the underside of footing or mat
foundations. The appropriate Site Class for such cases is determined on the basis of the average properties of the total thickness of the softer materials (see
Note A-4.1.8.4.(3) and Table 4.1.8.4.-A).
(2) Where
V
s30
has been measured in-situ, the F(T) values for Site Class A derived from Tables 4.1.8.4.-B to 4.1.8.4.-G are permitted to be multiplied by the factor 0.04 +
(1500/
V
s30
)
½
.
(3) Other soils include:
a) liquefiable soils, quick and highly sensitive clays, collapsible weakly cemented soils, and other soils susceptible to failure or collapse under seismic loading,
b) peat and/or highly organic clays greater than 3 m in thickness,
c) highly plastic clays (PI > 75) more than 8 m thick, and
d) soft to medium stiff clays more than 30 m thick.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
8) For structures with a fundamental period of vibration equal to or less than 0.5 s that are built on liquefiable
soils, Site Class and the corresponding values of F(T) may be determined as described in Tables4.1.8.4.-A,4.1.8.4.-B,
and4.1.8.4.-C by assuming that the soils are not liquefiable. (See NoteA-4.1.8.4.(3) and Table 4.1.8.4.-A.)
9) The design spectral acceleration values of S(T) shall be determined as follows, using linear interpolation for
intermediate values of T:
S(T) = F(0.2)S
a
(0.2) or F(0.5)S
a
(0.5), whichever is larger, for T ≤ 0.2 s
=F(0.5)S
a
(0.5) for T = 0.5 s
=F(1.0)S
a
(1.0) for T = 1.0 s
=F(2.0)S
a
(2.0) for T = 2.0 s
=F(5.0)S
a
(5.0)for T = 5.0 s
=F(10.0)S
a
(10.0) for T ≥ 10.0 s
Table 4.1.8.4.-B
Values of F(0.2) as a Function of Site Class and PGA
ref
Forming Part of Sentences 4.1.8.4.(4) and (5)
Site Class
Values of F(0.2)
PGA
ref
≤ 0.1 PGA
ref
= 0.2 PGA
ref
= 0.3 PGA
ref
= 0.4 PGA
ref
≥ 0.5
A 0.690.690.690.690.69
B 0.770.770.770.770.77
C 1.001.001.001.001.00
D 1.241.091.000.940.90
E 1.641.241.050.930.85
F
(1) (1) (1) (1) (1)
Notes to Table4.1.8.4.-B:
(1) See Sentence 4.1.8.4.(6).
Table 4.1.8.4.-C
Values of F(0.5) as a Function of Site Class and PGA
ref
Forming Part of Sentences 4.1.8.4.(4) and (5)
Site Class
Values of F(0.5)
PGA
ref
≤ 0.1 PGA
ref
= 0.2 PGA
ref
= 0.3 PGA
ref
= 0.4 PGA
ref
≥ 0.5
A 0.57 0.57 0.57 0.57 0.57
B 0.65 0.65 0.65 0.65 0.65
C 1.00 1.00 1.00 1.00 1.00
D 1.47 1.30 1.20 1.14 1.10
E 2.47 1.80 1.48 1.30 1.17
F
(1) (1) (1) (1) (1)
Notes to Table4.1.8.4.-C:
(1) See Sentence 4.1.8.4.(6).
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
Table 4.1.8.4.-D
Values of F(1.0) as a Function of Site Class and PGA
ref
Forming Part of Sentences 4.1.8.4.(4) and (5)
Site Class
Values of F(1.0)
PGA
ref
≤ 0.1 PGA
ref
= 0.2 PGA
ref
= 0.3 PGA
ref
= 0.4 PGA
ref
≥ 0.5
A 0.570.570.570.570.57
B 0.630.630.630.630.63
C 1.001.001.001.001.00
D 1.551.391.311.251.21
E 2.812.081.741.531.39
F
(1) (1) (1) (1) (1)
Notes to Table4.1.8.4.-D:
(1) See Sentence 4.1.8.4.(6).
Table 4.1.8.4.-E
Values of F(2.0) as a Function of Site Class and PGA
ref
Forming Part of Sentences 4.1.8.4.(4) and (5)
Site Class
Values of F(2.0)
PGA
ref
≤ 0.1 PGA
ref
= 0.2 PGA
ref
= 0.3 PGA
ref
= 0.4 PGA
ref
≥ 0.5
A 0.58 0.58 0.58 0.58 0.58
B 0.63 0.63 0.63 0.63 0.63
C 1.00 1.00 1.00 1.00 1.00
D 1.57 1.44 1.36 1.31 1.27
E 2.90 2.24 1.92 1.72 1.58
F
(1) (1) (1) (1) (1)
Notes to Table4.1.8.4.-E:
(1) See Sentence 4.1.8.4.(6).
Table 4.1.8.4.-F
Values of F(5.0) as a Function of Site Class and PGA
ref
Forming Part of Sentences 4.1.8.4.(4) and (5)
Site Class
Values of F(5.0)
PGA
ref
≤ 0.1 PGA
ref
= 0.2 PGA
ref
= 0.3 PGA
ref
= 0.4 PGA
ref
≥ 0.5
A 0.61 0.61 0.61 0.61 0.61
B 0.64 0.64 0.64 0.64 0.64
C 1.00 1.00 1.00 1.00 1.00
D 1.58 1.48 1.41 1.37 1.34
E 2.93 2.40 2.14 1.96 1.84
F
(1) (1) (1) (1) (1)
Notes to Table4.1.8.4.-F:
(1) See Sentence 4.1.8.4.(6).
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Table 4.1.8.4.-G
Values of F(10.0) as a Function of Site Class and PGA
ref
Forming Part of Sentences 4.1.8.4.(4) and (5)
Site Class
Values of F(10.0)
PGA
ref
≤ 0.1 PGA
ref
= 0.2 PGA
ref
= 0.3 PGA
ref
= 0.4 PGA
ref
≥ 0.5
A 0.67 0.67 0.67 0.67 0.67
B 0.69 0.69 0.69 0.69 0.69
C 1.00 1.00 1.00 1.00 1.00
D 1.49 1.41 1.37 1.34 1.31
E 2.52 2.18 2.00 1.88 1.79
F
(1) (1) (1) (1) (1)
Notes to Table4.1.8.4.-G:
(1) See Sentence 4.1.8.4.(6).
Table 4.1.8.4.-H
Values of F(PGA) as a Function of Site Class and PGA
ref
Forming Part of Sentences 4.1.8.4.(4) and (5)
Site Class
Values of F(PGA)
PGA
ref
≤ 0.1 PGA
ref
= 0.2 PGA
ref
= 0.3 PGA
ref
= 0.4 PGA
ref
≥ 0.5
A 0.90 0.90 0.90 0.90 0.90
B 0.87 0.87 0.87 0.87 0.87
C 1.00 1.00 1.00 1.00 1.00
D 1.29 1.10 0.99 0.93 0.88
E 1.81 1.23 0.98 0.83 0.74
F
(1) (1) (1) (1) (1)
Notes to Table4.1.8.4.-H:
(1) See Sentence 4.1.8.4.(6).
Table 4.1.8.4.-I
Values of F(PGV) as a Function of Site Class and PGA
ref
Forming Part of Sentences 4.1.8.4.(4) and (5)
Site Class
Values of F(PGV)
PGA
ref
≤ 0.1 PGA
ref
= 0.2 PGA
ref
= 0.3 PGA
ref
= 0.4 PGA
ref
≥ 0.5
A 0.62 0.62 0.62 0.62 0.62
B 0.67 0.67 0.67 0.67 0.67
C 1.00 1.00 1.00 1.00 1.00
D 1.47 1.30 1.20 1.14 1.10
E 2.47 1.80 1.48 1.30 1.17
F
(1) (1) (1) (1) (1)
Notes to Table4.1.8.4.-I:
(1) See Sentence 4.1.8.4.(6).
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.8.5. Importance Factor
1) The earthquake importance factor, I
E
, shall be determined according to Table4.1.8.5.
4.1.8.6. Structural Configuration
1) Structures having any of the features listed in Table4.1.8.6. shall be designated irregular.
2) Structures not classified as irregular according to Sentence4.1.8.6.(1) may be considered regular.
3) Except as required by Article4.1.8.10., in cases where I
E
F
a
S
a
(0.2) is equal to or greater than 0.35, structures
designated as irregular must satisfy the provisions referenced in Table4.1.8.6.
Table 4.1.8.5.
Importance Factor for Earthquake Loads and Effects, I
E
Forming Part of Sentence 4.1.8.5.(1)
Importance Category
Importance Factor, I
E
ULS SLS
(1)
Low 0.8
(2)
Normal 1.0
High 1.3
Post-disaster 1.5
Notes to Table4.1.8.5.:
(1) See Article 4.1.8.13.
(2) See Note A-Table 4.1.8.5.
Table 4.1.8.6.
Structural Irregularities
(1)
Forming Part of Sentence 4.1.8.6.(1)
Type Irregularity Type and Definition Notes
1
Vertical Stiffness Irregularity
Vertical stiffness irregularity shall be considered to exist when the lateral stiffness of the SFRS in a storey is less than 70% of
the stiffness of any adjacent storey, or less than 80% of the average stiffness of the three storeys above or below.
(2)(3)(4)
2
Weight (mass) Irregularity
Weight irregularity shall be considered to exist where the weight, W
i
, of any storey is more than 150% of the weight of an
adjacent storey. A roof that is lighter than the floor below need not be considered.
(2)
3
Vertical Geometric Irregularity
Vertical geometric irregularity shall be considered to exist where the horizontal dimension of the SFRS in any storey is more
than 130% of that in an adjacent storey.
(2)(3)(4)(5)
4
In-Plane Discontinuity in Vertical Lateral-Force-Resisting Element
Except for braced frames and moment-resisting frames, an in-plane discontinuity shall be considered to exist where there is
an offset of a lateral-force-resisting element of the SFRS or a reduction in lateral stiffness of the resisting element in the
storey below.
(2)(3)(4)(5)
5
Out-of-Plane Offsets
Discontinuities in a lateral force path, such as out-of-plane offsets of the vertical elements of the SFRS.
(2)(3)(4)(5)
6
Discontinuity in Capacity – Weak Storey
A weak storey is one in which the storey shear strength is less than that in the storey above. The storey shear strength is the
total strength of all seismic-resisting elements of the SFRS sharing the storey shear for the direction under consideration.
(2)(3)
7
Torsional Sensitivity (to be considered when diaphragms are not flexible)
Torsional sensitivity shall be considered to exist when the ratio B calculated according to Sentence 4.1.8.11.(10) exceeds 1.7.
(2)(3)(4)(6)
8
Non-orthogonal Systems
A non-orthogonal system irregularity shall be considered to exist when the SFRS is not oriented along a set of orthogonal axes.
(2)(4)(7)
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4.1.8.7. Methods of Analysis
1) Analysis for design earthquake actions shall be carried out in accordance with the Dynamic Analysis
Procedure described in Article4.1.8.12. (see NoteA-4.1.8.7.(1)), except that the Equivalent Static Force Procedure
described in Article4.1.8.11. may be used for structures that meet any of the following criteria:
a) in cases where I
E
F
a
S
a
(0.2) is less than 0.35,
b) regular structures that are less than 60 m in height and have a fundamental lateral period, T
a
, less than 2 s in
each of two orthogonal directions as defined in Article4.1.8.8., or
c) structures with structural irregularity, of Type1, 2, 3, 4, 5, 6 or 8 as defined in Table4.1.8.6., that are less than
20 m in height and have a fundamental lateral period, T
a
, less than 0.5 s in each of two orthogonal directions
as defined in Article4.1.8.8.
4.1.8.8. Direction of Loading
1) Earthquake forces shall be assumed to act in any horizontal direction, except that the following shall be
considered to provide adequate design force levels in the structure:
a) where components of the SFRS are oriented along a set of orthogonal axes, independent analyses about each
of the principal axes of the structure shall be performed,
b) where the components of the SFRS are not oriented along a set of orthogonal axes and I
E
F
a
S
a
(0.2) is less
than 0.35, independent analyses about any two orthogonal axes is permitted, or
c) where the components of the SFRS are not oriented along a set of orthogonal axes and I
E
F
a
S
a
(0.2) is equal to
or greater than 0.35, analysis of the structure independently in any two orthogonal directions for 100% of the
prescribed earthquake loads applied in one direction plus 30% of the prescribed earthquake loads in the
perpendicular direction, with the combination requiring the greater element strength being used in the design.
4.1.8.9. SFRS Force Reduction Factors, System Overstrength Factors, and General
Restrictions
1) Except as provided in Sentence4.1.8.20.(7), the values of R
d
and R
o
and the corresponding system
restrictions shall conform to Table4.1.8.9. and the requirements of this Subsection.
2) When a particular value of R
d
is required by this Article, the corresponding R
o
shall be used.
3) For combinations of different types of SFRS acting in the same direction in the same storey, R
d
R
o
shall be
taken as the lowest value of R
d
R
o
corresponding to these systems.
4) For vertical variations of R
d
R
o
, excluding rooftop structures not exceeding two storeys in height whose weight
is less than the greater of 10% of W and 30% of W
i
of the level below, the value of R
d
R
o
used in the design of any
storey shall be less than or equal to the lowest value of R
d
R
o
used in the given direction for the storeys above, and the
requirements of Sentence4.1.8.15.(6) must be satisfied. (See NoteA-4.1.8.9.(4).)
9
Gravity-Induced Lateral Demand Irregularity
Gravity-induced lateral demand irregularity on the SFRS shall be considered to exist where the ratio, α, calculated in
accordance with Sentence 4.1.8.10.(5), exceeds 0.1 for an SFRS with self-centering characteristics and 0.03 for other systems.
(2)(3)(4)(7)
Notes to Table4.1.8.6.:
(1) One-storey penthouses with a weight of less than 10% of the level below need not be considered in the application of this Table.
(2) See Article 4.1.8.7.
(3) See Article 4.1.8.10.
(4) See Note A-Table 4.1.8.6.
(5) See Article 4.1.8.15.
(6) See Sentences 4.1.8.11.(10), (11) and 4.1.8.12.(4).
(7) See Article 4.1.8.8.
Table 4.1.8.6. (continued)
Structural Irregularities
(1)
Forming Part of Sentence 4.1.8.6.(1)
Type Irregularity Type and Definition Notes
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
5) If it can be demonstrated through testing, research and analysis that the seismic performance of a structural
system is at least equivalent to one of the types of SFRS mentioned in Table4.1.8.9., then such a structural system
will qualify for values of R
d
and R
o
corresponding to the equivalent type in that Table. (See NoteA-4.1.8.9.(5).)
Table 4.1.8.9.
SFRS Ductility-Related Force Modification Factors, R
d
, Overstrength-Related Force
Modification Factors, R
o
, and General Restrictions
(1)
Forming Part of Sentence 4.1.8.9.(1)
Type of SFRS R
d
R
o
Restrictions
(2)
Cases Where I
E
F
a
S
a
(0.2)
Cases
Where
I
E
F
v
S
a
(1.0)
< 0.2
≥ 0.2 to
<0.35
≥ 0.35 to
≤ 0.75
> 0.75 > 0.3
Steel Structures Designed and Detailed According to CSA S16(3)(4)
Ductile moment-resisting frames 5.0 1.5 NL NL NL NL NL
Moderately ductile moment-resisting frames 3.5 1.5 NL NL NL NL NL
Limited ductility moment-resisting frames 2.0 1.3 NL NL 60 30 30
Moderately ductile concentrically braced frames
Tension-compression braces 3.0 1.3 NL NL 40 40 40
Tension only braces 3.0 1.3 NL NL 20 20 20
Limited ductility concentrically braced frames
Tension-compression braces 2.0 1.3 NL NL 60 60 60
Tension only braces 2.0 1.3 NL NL 40 40 40
Ductile buckling-restrained braced frames 4.0 1.2 NL NL 40 40 40
Ductile eccentrically braced frames 4.0 1.5 NL NL NL NL NL
Ductile plate walls 5.0 1.6 NL NL NL NL NL
Limited ductility plate walls 2.0 1.5 NL NL 60 60 60
Conventional construction of moment-resisting frames,
braced frames or plate walls
Assembly occupancies 1.5 1.3 NL NL 15 15 15
Other occupancies 1.5 1.3 NL NL 60 40 40
Other steel SFRS(s) not defined above 1.0 1.0 15 15 NP NP NP
Concrete Structures Designed and Detailed According to CSA A23.3
Ductile moment-resisting frames 4.0 1.7 NL NL NL NL NL
Moderately ductile moment-resisting frames 2.5 1.4 NL NL 60 40 40
Ductile coupled walls 4.0 1.7 NL NL NL NL NL
Moderately ductile coupled walls 2.5 1.4 NL NL NL 60 60
Ductile partially coupled walls 3.5 1.7 NL NL NL NL NL
Moderately ductile partially coupled walls 2.0 1.4 NL NL NL 60 60
Ductile shear walls 3.5 1.6 NL NL NL NL NL
Moderately ductile shear walls 2.0 1.4 NL NL NL 60 60
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Conventional construction
Moment-resisting frames 1.5 1.3 NL NL 20 15 10
(5)
Shear walls 1.5 1.3 NL NL 40 30 30
Two-way slabs without beams 1.3 1.3 20 15 NP NP NP
Tilt-up construction
Moderately ductile walls and frames 2.0 1.3 30 25 25 25 25
Limited ductility walls and frames 1.5 1.3 30 25 20 20 20
(6)
Conventional walls and frames 1.3 1.3 25 20 NP NP NP
Other concrete SFRS(s) not listed above 1.0 1.0 15 15 NP NP NP
Timber Structures Designed and Detailed According to CSA O86
Shear walls
Nailed shear walls: wood-based panel 3.0 1.7 NL NL 30 20 20
Shear walls: wood-based and gypsum panels in
combination
2.0 1.7 NL NL 20 20 20
Moderately ductile cross-laminated timber shear
walls: platform-type construction
2.0 1.5 30 30 30 20 20
Limited ductility cross-laminated timber shear walls:
platform-type construction
1.0 1.3 30 30 30 20 20
Braced or moment-resisting frames with ductile
connections
Moderately ductile 2.0 1.5 NL NL 20 20 20
Limited ductility 1.5 1.5 NL NL 15 15 15
Other wood- or gypsum-based SFRS(s) not listed
above
1.0 1.0 15 15 NP NP NP
Masonry Structures Designed and Detailed According to CSA S304
Ductile shear walls 3.0 1.5NLNL604040
Moderately ductile shear walls 2.0 1.5 NL NL 60 40 40
Conventional construction
Shear walls 1.51.5NL60301515
Moment-resisting frames 1.5 1.5 NL 30 NP NP NP
Unreinforced masonry 1.0 1.0 30 15 NP NP NP
Other masonry SFRS(s) not listed above 1.0 1.0 15 NP NP NP NP
Table 4.1.8.9. (continued)
SFRS Ductility-Related Force Modification Factors, R
d
, Overstrength-Related Force
Modification Factors, R
o
, and General Restrictions
(1)
Forming Part of Sentence 4.1.8.9.(1)
Type of SFRS R
d
R
o
Restrictions
(2)
Cases Where I
E
F
a
S
a
(0.2)
Cases
Where
I
E
F
v
S
a
(1.0)
< 0.2
≥ 0.2 to
<0.35
≥ 0.35 to
≤ 0.75
> 0.75 > 0.3
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4.1.8.10. Additional System Restrictions
1) Except as required by Clause (2)(b), structures with a Type6 irregularity, Discontinuity in Capacity – Weak
Storey, as described in Table 4.1.8.6., are not permitted unless I
E
F
a
S
a
(0.2) is less than 0.2 and the forces used for
design of the SFRS are multiplied by R
d
R
o
.
2) Post-disaster buildings shall
a) not have any irregularities conforming to Types 1, 3, 4, 5, 7 and 9 as described in Table4.1.8.6., in cases
where I
E
F
a
S
a
(0.2) is equal to or greater than 0.35,
b) not have a Type6 irregularity as described in Table4.1.8.6.,
c) have an SFRS with an R
d
of 2.0 or greater, and
d) have no storey with a lateral stiffness that is less than that of the storey above it.
3) For buildings having fundamental lateral periods, T
a
, of 1.0s or greater, and where I
E
F
v
S
a
(1.0) is greater than
0.25, shear walls that are other than wood-based and form part of the SFRS shall be continuous from their top to the
foundation and shall not have irregularities of Type4 or 5 as described in Table4.1.8.6.
4) For buildings constructed with more than 4 storeys of continuous wood construction and where I
E
F
a
S
a
(0.2) is
equal to or greater than 0.35, timber SFRS consisting of shear walls with wood-based panels or of braced or
moment-resisting frames as defined in Table4.1.8.9. within the continuous wood construction shall not have Type4
or Type5 irregularities as described in Table4.1.8.6. (See NoteA-4.1.8.10.(4) and (5)
.)
Cold-Formed Steel Structures Designed and Detailed According to CSA S136
Shear walls
Screw-connected shear walls – wood-based panels 2.5 1.7 20 20 20 20 20
Screw-connected shear walls – wood-based and
gypsum panels in combination
1.5 1.7 20 20 20 20 20
Diagonal strap concentrically braced walls
Limited ductility 1.9 1.3 20 20 20 20 20
Conventional construction 1.2 1.3 15 15 NP NP NP
Other cold-formed SFRS(s) not defined above 1.0 1.0 15 15 NP NP NP
Notes to Table4.1.8.9.:
(1) See Article 4.1.8.10.
(2) NP = system is not permitted.
NL = system is permitted and not limited in height as an SFRS.
Numbers in this Table are maximum height limits above grade, in m.
Height may be limited in other Parts of the Code.
The most stringent requirement governs.
(3) Higher design force levels are prescribed in CSA S16 for some heights of buildings.
(4) See Note A-Table 4.1.8.9.
(5) Frames limited to a maximum of 2 storeys.
(6) Frames limited to a maximum of 3 storeys.
Table 4.1.8.9. (continued)
SFRS Ductility-Related Force Modification Factors, R
d
, Overstrength-Related Force
Modification Factors, R
o
, and General Restrictions
(1)
Forming Part of Sentence 4.1.8.9.(1)
Type of SFRS R
d
R
o
Restrictions
(2)
Cases Where I
E
F
a
S
a
(0.2)
Cases
Where
I
E
F
v
S
a
(1.0)
< 0.2
≥ 0.2 to
<0.35
≥ 0.35 to
≤ 0.75
> 0.75 > 0.3
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
5) For buildings constructed with more than 4 storeys of continuous wood construction and where I
E
F
a
S
a
(0.2) is
equal to or greater than 0.35, timber SFRS consisting of moderately ductile cross-laminated timber shear walls,
platform-type construction, or limited ductility cross-laminated timber shear walls, platform-type construction, as
defined in Table 4.1.8.9. within the continuous wood construction shall not have Type 4, 5, 6, 8, 9 or 10 irregularities
as described in Table 4.1.8.6. (See Note A-4.1.8.10.(4) and (5).)
6) The ratio, , for a Type9 irregularity as described in Table4.1.8.6. shall be determined independently for
each orthogonal direction using the following equation:
where
Q
G
= gravity-induced lateral demand on the SFRS at the critical level of the yielding system, and
Q
y
= the resistance of the yielding mechanism required to resist the minimum earthquake loads, which need
not be taken as less than R
o
multiplied by the minimum lateral earthquake force as determined in
Article4.1.8.11. or 4.1.8.12., as appropriate.
(See NoteA-4.1.8.10.(5).)
7) For buildings with a Type9 irregularity as described in Table4.1.8.6. and where I
E
F
a
S
a
(0.2) is equal to or
greater than 0.5, deflections determined in accordance with Article4.1.8.13. shall be multiplied by 1.2.
8) Structures where the value of , as determined in accordance with Sentence(5), exceeds twice the limits
specified in Table4.1.8.6. for a Type 9 irregularity, and where I
E
F
a
S
a
(0.2) is equal to or greater than 0.5 are not
permitted unless determined to be acceptable based on non-linear dynamic analysis studies. (See
NoteA-4.1.8.10.(8
).)
4.1.8.11. Equivalent Static Force Procedure for Structures Satisfying the Conditions of
Article 4.1.8.7.
1) The static loading due to earthquake motion shall be determined according to the procedures given in this
Article.
2) Except as provided in Sentence(12), the minimum lateral earthquake force, V, shall be calculated using the
following formula:
except
a) for walls, coupled walls and wall-frame systems, V shall not be less than
b) for moment-resisting frames, braced frames, and other systems, V shall not be less than
c) for buildings located on a site other than ClassF and having an SFRS with an R
d
equal to or greater than 1.5,
Vneed not be greater than the larger of
V S(T
a
)M
v
I
E
W/(R
d
R
o
)
S (4.0) M
v
I
E
W/(R
d
R
o
)
S (2.0) M
v
I
E
W/(R
d
R
o
)
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
3) Except as provided in Sentence(4), the fundamental lateral period, T
a
, in the direction under consideration in
Sentence(2), shall be determined as:
a) for moment-resisting frames that resist 100% of the required lateral forces and where the frame is not
enclosed by or adjoined by more rigid elements that would tend to prevent the frame from resisting lateral
forces, and where h
n
is in metres:
i) 0.085 (h
n
)
3/4
for steel moment frames,
ii) 0.075 (h
n
)
3/4
for concrete moment frames, or
iii) 0.1 N for other moment frames,
b) 0.025h
n
for braced frames where h
n
is in metres,
c) 0.05 (h
n
)
3/4
for shear wall and other structures where h
n
is in metres, or
d) other established methods of mechanics using a structural model that complies with the requirements of
Sentence4.1.8.3.(8), except that
i) for moment-resisting frames, T
a
shall not be taken greater than 1.5times that determined in Clause(a),
ii) for braced frames, T
a
shall not be taken greater than 2.0times that determined in Clause(b),
iii) for shear wall structures, T
a
shall not be taken greater than 2.0times that determined in Clause(c),
iv) for other structures, T
a
shall not be taken greater than that determined in Clause(c), and
v) for the purpose of calculating the deflections, the period without the upper limit specified in
Subclauses(d)(i) to(d)(iv) may be used, except that, for walls, coupled walls and wall-frame systems, T
a
shall not exceed 4.0s, and for moment-resisting frames, braced frames, and other systems, T
a
shall not
exceed 2.0s.
(See NoteA-4.1.8.11.(3).)
4) For single-storey buildings with steel deck or wood roof diaphragms, the fundamental lateral period, T
a
, in the
direction under consideration is permitted to be taken as
a) 0.05 (h
n
)
3/4
+ 0.004L for shear walls,
b) 0.035 h
n
+ 0.004L for steel moment frames and steel braced frames, or
c) the value obtained from methods of mechanics using a structural model that complies with the requirements
of Sentence4.1.8.3.(8), except that T
a
shall not be greater than 1.5 times the value determined in Clause(a)
or(b), as applicable,
where L is the shortest length of the diaphragm, in m, between adjacent vertical elements of the SFRS in the
direction perpendicular to the direction under consideration.
5) The weight, W, of the building shall be calculated using the following formula:
6) The higher mode factor, M
v
, and its associated base overturning moment reduction factor, J, shall conform
to Table4.1.8.11.
7) The total lateral seismic force, V, shall be distributed such that a portion, F
t
, shall be assumed to be
concentrated at the top of the building, where F
t
is equal to 0.07T
a
V but need not exceed 0.25V and may be
considered as zero where the fundamental lateral period, T
a
, does not exceed 0.7s; the remainder, V - F
t
, shall be
distributed along the height of the building, including the top level, in accordance with the following formula:
n
W
兺
W
i
i1
n
F
x
(V – F
t
)W
x
h
x
/
冢
兺
W
i
h
i
冣
i1
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Table 4.1.8.11.
Higher Mode Factor, Mv, and Base Overturning Reduction Factor, J
(1)(2)(3)(4)
Forming Part of Sentence 4.1.8.11.(6)
S(0.2)/S(5.0) M
v
for T
a
≤ 0.5 M
v
for T
a
= 1.0 M
v
for T
a
= 2.0 M
v
for T
a
≥ 5.0 J for T
a
≤ 0.5 J for T
a
= 1.0 J for T
a
= 2.0 J for T
a
≥ 5.0
Moment-Resisting Frames
5111
(5)
1 0.97 0.92
(5)
20111
(5)
1 0.93 0.85
(5)
40111
(5)
1 0.87 0.78
(5)
65 1 1 1.03
(5)
1 0.80 0.70
(5)
Coupled Walls
(6)
51111
(7)
1 0.97 0.92 0.80
(8)
20 1 1 1 1.08
(7)
1 0.93 0.85 0.65
(8)
40 1 1 1 1.30
(7)
1 0.87 0.78 0.53
(8)
65 1 1 1.03 1.49
(7)
1 0.80 0.70 0.46
(8)
Braced Frames
5111
(5)
1 0.95 0.89
(5)
20111
(5)
1 0.85 0.78
(5)
40111
(5)
1 0.79 0.70
(5)
65 1 1.04 1.07
(5)
1 0.71 0.66
(5)
Walls, Wall Frame Systems
51111.25
(7)
1 0.97 0.85 0.55
(8)
20 1 1 1.18 2.30
(7)
1 0.80 0.60 0.35
(8)
40 1 1.19 1.75 3.70
(7)
1 0.63 0.46 0.28
(8)
65 1 1.55 2.25 4.65
(7)
1 0.51 0.39 0.23
(8)
Other Systems
5111
(5)
1 0.97 0.85
(5)
20 1 1 1.18
(5)
1 0.80 0.60
(5)
40 1 1.19 1.75
(5)
1 0.63 0.46
(5)
65 1 1.55 2.25
(5)
1 0.51 0.39
(5)
Notes to Table4.1.8.11.:
(1) For intermediate values of the spectral ratio S(0.2)/S(5.0), M
v
and J shall be obtained by linear interpolation.
(2) For intermediate values of the fundamental lateral period, T
a
, S(T
a
)M
v
shall be obtained by linear interpolation using the values of M
v
obtained in accordance with Note (1).
(3) For intermediate values of the fundamental lateral period, T
a
, J shall be obtained by linear interpolation using the values of J obtained in accordance with Note (1).
(4) For a combination of different seismic force resisting systems (SFRS) not given in Table 4.1.8.11. that are in the same direction under consideration, use the highest M
v
factor of all the SFRS and the corresponding value of J.
(5) For fundamental lateral periods, T
a
, greater than 2.0 s, use the 2.0 s values obtained in accordance with Note (1). See Clause 4.1.8.11.(2)(b).
(6) A “coupled” wall is a wall system with coupling beams, where at least 66% of the base overturning moment resisted by the wall system is carried by the axial tension and
compression forces resulting from shear in the coupling beams.
(7) For fundamental lateral periods, T
a
, greater than 4.0 s, use the 4.0 s values of S(T
a
)M
v
obtained by interpolation between 2.0 s and 5.0 s using the value of M
v
obtained in
accordance with Note (1). See Clause 4.1.8.11.(2)(a).
(8) For fundamental lateral periods, T
a
, greater than 4.0 s, use the 4.0 s values of J obtained by interpolation between 2.0 s and 5.0 s using the value of J obtained in
accordance with Note (1). See Clause 4.1.8.11.(2)(a).
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
8) The structure shall be designed to resist overturning effects caused by the earthquake forces determined in
Sentence(7) and the overturning moment at level x, M
x
, shall be determined using the following equation:
where
J
x
=1.0 for h
x
≥ 0.6h
n
, and
J
x
= J + (1 - J)(h
x
/ 0.6h
n
) for h
x
< 0.6h
n
where
J = base overturning moment reduction factor conforming to Table4.1.8.11.
9) Torsional effects that are concurrent with the effects of the forces mentioned in Sentence(7) and are caused
by the simultaneous actions of the following torsional moments shall be considered in the design of the structure
according to Sentence(11):
a) torsional moments introduced by eccentricity between the centres of mass and resistance and their dynamic
amplification, and
b) torsional moments due to accidental eccentricities.
10) Torsional sensitivity shall be determined by calculating the ratio B
x
for each level x according to the following
equation for each orthogonal direction determined independently:
where
B = maximum of all values of B
x
in both orthogonal directions, except that the B
x
for one-storey penthouses
with a weight less than 10% of the level below need not be considered,
max
=maximum storey displacement at the extreme points of the structure, at level x in the direction of the
earthquake induced by the equivalent static forces acting at distances ±0.10D
nx
from the centres of
mass at each floor, and
ave
= average of the displacements at the extreme points of the structure at level x produced by the
above-mentioned forces.
11) Torsional effects shall be accounted for as follows:
a) for a building with B ≤ 1.7 or where I
E
F
a
S
a
(0.2) is less than 0.35, by applying torsional moments about a
vertical axis at each level throughout the building, derived for each of the following load cases considered
separately:
i) T
x
= F
x
(e
x
+ 0.10 D
nx
), and
ii) T
x
= F
x
(e
x
- 0.10 D
nx
)
where F
x
is the lateral force at each level determined according to Sentence(7) and where each element of the
building is designed for the most severe effect of the above load cases, or
b) for a building with B > 1.7, in cases where I
E
F
a
S
a
(0.2) is equal to or greater than 0.35, by a Dynamic Analysis
Procedure as specified in Article4.1.8.12.
12) Where the fundamental lateral period, T
a
, is determined in accordance with Clause(3)(d) and the building is
constructed with more than 4 storeys of continuous wood construction and has a timber SFRS consisting of shear
walls with wood-based panels or of braced or moment-resisting frames as defined in Table4.1.8.9., the lateral
earthquake force, V, as determined in accordance with Sentence(2) shall be multiplied by 1.2 but need not exceed the
value determined by using Clause(2)(c). (See NoteA-4.1.8.10.(4).)
4.1.8.12. Dynamic Analysis Procedure
1) Except as provided in Articles4.1.8.19. and4.1.8.21., the Dynamic Analysis Procedure shall be in accordance
with one of the following methods:
a) Linear Dynamic Analysis by either the Modal Response Spectrum Method or the Numerical Integration
Linear Time History Method using a structural model that complies with the requirements of
Sentence4.1.8.3.(8) (see NoteA-4.1.8.12.(1)(a)), or
n
M
x
J
x
兺
F
i
(h
i
– h
x
)
ix
B
x
max
/
ave
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
b) Non-linear Dynamic Analysis, in which case a special study shall be performed (see NoteA-4.1.8.12.(1)(b)).
2) The spectral acceleration values used in the Modal Response Spectrum Method shall be the design spectral
acceleration values, S(T), defined in Sentence4.1.8.4.(9).
3) The ground motion histories used in the Numerical Integration Linear Time History Method shall be
compatible with a response spectrum constructed from the design spectral acceleration values, S(T), defined in
Sentence4.1.8.4.(9). (See NoteA-4.1.8.12.(3).)
4) The effects of accidental torsional moments acting concurrently with the lateral earthquake forces that cause
them shall be accounted for by the following methods:
a) the static effects of torsional moments due to (± 0.10 D
nx
)F
x
at each level x, where F
x
is either determined
from the elastic dynamic analysis or determined from Sentence4.1.8.11.(7) multiplied by R
d
R
o
/I
E
, shall be
combined with the effects determined by dynamic analysis (see NoteA-4.1.8.12.(4)(a)), or
b) if B, as defined in Sentence4.1.8.11.(10), is less than 1.7, it is permitted to use a three-dimensional dynamic
analysis with the centres of mass shifted by a distance of –0.05 D
nx
and + 0.05 D
nx
.
5) Except as provided in Sentence(6), the design elastic base shear, V
ed
, shall be equal to the elastic base shear,
V
e
, obtained from a Linear Dynamic Analysis.
6) For structures located on sites other than Class F that have an SFRS with R
d
equal to or greater than 1.5, the
elastic base shear obtained from a Linear Dynamic Analysis may be multiplied by the larger of the following factors
to obtain the design elastic base shear, V
ed
:
7) The design elastic base shear, V
ed
, shall be multiplied by the importance factor, I
E
, as determined in
Article4.1.8.5., and shall be divided by R
d
R
o
, as determined in Article4.1.8.9., to obtain the design base shear, V
d
.
8) Except as required by Sentence(9) or(12), if the base shear, V
d
, obtained in Sentence(7) is less than 80% of
the lateral earthquake design force, V, of Article4.1.8.11., V
d
shall be taken as 0.8V.
9) For irregular structures requiring dynamic analysis in accordance with Article4.1.8.7., V
d
shall be taken as the
larger of the V
d
determined in Sentence(7) and 100% of V.
10) Except as required by Sentence(11), the values of elastic storey shears, storey forces, member forces, and
deflections obtained from the Linear Dynamic Analysis, including the effect of accidental torsion determined in
Sentence(4), shall be multiplied by V
d
/V
e
to determine their design values, where V
d
is the base shear.
11) For the purpose of calculating deflections, it is permitted to use a value for V based on the value for T
a
determined in Clause4.1.8.11.(3)(d) to obtain V
d
in Sentences(8) and(9).
12) For buildings constructed with more than 4 storeys of continuous wood construction, having a timber SFRS
consisting of shear walls with wood-based panels or braced or moment-resisting frames as defined in Table4.1.8.9.,
and whose fundamental lateral period, T
a
, is determined in accordance with Clause4.1.8.11.(3)(d), the design base
shear, V
d
, shall be taken as the larger value of V
d
determined in accordance with Sentence(7) and 100% of V.
(SeeNoteA-4.1.8.10.(4).)
4.1.8.13. Deflections and Drift Limits
1) Except as provided in Sentences(5) and(6), lateral deflections of a structure shall be calculated in accordance
with the loads and requirements defined in this Subsection.
2) Lateral deflections obtained from a linear elastic analysis using the methods given in Articles4.1.8.11.
and4.1.8.12. and incorporating the effects of torsion, including accidental torsional moments, shall be multiplied by
R
d
R
o
/I
E
and increased as required in Sentences4.1.8.10.(6) and 4.1.8.16.(1) to give realistic values of anticipated
deflections.
3) Based on the lateral deflections calculated in Sentences(2),(5) and(6), the largest interstorey deflection at any
level shall be limited to 0.01h
s
for post-disaster buildings, 0.02h
s
for High Importance Category buildings, and 0.025h
s
for all other buildings.
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4) The deflections calculated in Sentence(2) shall be used to account for sway effects as required by
Sentence4.1.3.2.(12). (See NoteA-4.1.8.13.(4).)
5) The lateral deflections of a seismically isolated structure shall be calculated in accordance with
Article4.1.8.20.
6) The lateral deflections of a structure with supplemental energy dissipation shall be calculated in accordance
with Article4.1.8.22.
4.1.8.14. Structural Separation
1) Adjacent structures shall either be separated by the square root of the sum of the squares of their individual
deflections calculated in Sentence4.1.8.13.(2), or shall be connected to each other.
2) The method of connection required in Sentence(1) shall take into account the mass, stiffness, strength,
ductility and anticipated motion of the connected buildings and the character of the connection.
3) Rigidly connected buildings shall be assumed to have the lowest R
d
R
o
value of the buildings connected.
4) Buildings with non-rigid or energy-dissipating connections require special studies.
4.1.8.15. Design Provisions
1) Except as provided in Sentences(2) and(3), diaphragms, collectors, chords, struts and connections shall be
designed so as not to yield, and the design shall account for the shape of the diaphragm, including openings, and for
the forces generated in the diaphragm due to the following cases, whichever one governs (see NoteA-4.1.8.15.(1)):
a) forces due to loads determined in Article4.1.8.11. or4.1.8.12. applied to the diaphragm are increased to
reflect the lateral load capacity of the SFRS, plus forces in the diaphragm due to the transfer of forces
between elements of the SFRS associated with the lateral load capacity of such elements and accounting for
discontinuities and changes in stiffness in these elements, or
b) a minimum force corresponding to the design-based shear divided by N for the diaphragm at level x.
2) Steel deck roof diaphragms in buildings of less than 4 storeys or wood diaphragms that are designed and detailed
according to the applicable referenced design standards to exhibit ductile behaviour shall meet the requirements of
Sentence(1), except that they may yield and the forces shall be
a) for wood diaphragms acting in combination with vertical wood shear walls, equal to the lateral earthquake
design force,
b) for wood diaphragms acting in combination with other SFRS, not less than the force corresponding to
R
d
R
o
=2.0, and
c) for steel deck roof diaphragms, not less than the force corresponding to R
d
R
o
=2.0.
3) Where diaphragms are designed in accordance with Sentence(2), the struts shall be designed in accordance
with Clause4.1.8.15.(1)(a) and the collectors, chords and connections between the diaphragms and the vertical
elements of the SFRS shall be designed for forces corresponding to the capacity of the diaphragms in accordance
with the applicable CSAstandards. (See NoteA-4.1.8.15.(3).)
4) For single-storey buildings with steel deck or wood roof diaphragms designed with a value of R
d
greater than 1.5
and where the calculated maximum relative deflection, ΔD, of the diaphragm under lateral loads exceeds 50% of the
average storey drift, ΔB, of the adjoining vertical elements of the SFRS, dynamic magnification of the inelastic
response due to the in-plane diaphragm deformations shall be accounted for in the design as follows:
a) the vertical elements of the SFRS shall be designed and detailed to any one of the following:
i) to accommodate the anticipated magnified lateral deformations taken as R
o
R
d
(Δ
B
+Δ
D
) - R
o
Δ
D
,
ii) to resist the forces magnified by R
d
(1 + Δ
D
/Δ
B
)/(R
d
+ Δ
D
/Δ
B
), or
iii) by a special study, and
b) the roof diaphragm and chords shall be designed for in-plane shears and moments determined while taking
into consideration the inelastic higher mode response of the structure.
(See NoteA-4.1.8.15.(4).)
5) In cases where I
E
F
a
S
a
(0.2) is equal to or greater than 0.35, the elements supporting any discontinuous wall,
column or braced frame shall be designed for the lateral load capacity of the components of the SFRS they support.
(See NoteA-4.1.8.15.(5).)
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
6) Where structures have vertical variations of R
d
R
o
satisfying Sentence4.1.8.9.(4), the elements of the SFRS
below the level where the change in R
d
R
o
occurs shall be designed for the forces associated with the lateral load
capacity of the SFRS above that level. (See NoteA-4.1.8.15.(6).)
7) Where earthquake effects can produce forces in a column or wall due to lateral loading along both
orthogonal axes, account shall be taken of the effects of potential concurrent yielding of other elements framing into
the column or wall from all directions at the level under consideration and as appropriate at other levels.
(SeeNoteA-4.1.8.15.(7).)
8) The design forces associated with the lateral capacity of the SFRS need not exceed the forces determined in
accordance with Sentence4.1.8.7.(1) with R
d
R
o
taken as 1.0, unless otherwise provided by the applicable referenced
design standards for elements, in which case the design forces associated with the lateral capacity of the SFRS need
not exceed the forces determined in accordance with Sentence4.1.8.7.(1) with R
d
R
o
taken as less than or equal to 1.3.
(SeeNoteA-4.1.8.15.(8).)
9) Foundations need not be designed to resist the lateral load overturning capacity of the SFRS, provided the
design and the R
d
and R
o
for the type of SFRS used conform to Table4.1.8.9. and that the foundation is designed in
accordance with Sentence4.1.8.16.(4).
10) Foundation displacements and rotations shall be considered as required by Sentence4.1.8.16.(1).
4.1.8.16. Foundation Provisions
1) The increased displacements of the structure resulting from foundation movement shall be shown to be within
acceptable limits for both the SFRS and the structural framing elements not considered to be part of the SFRS.
(SeeNoteA-4.1.8.16.(1).)
2) Except as provided in Sentences(3) and(4), foundations shall be designed to have factored shear and
overturning resistances greater than the lateral load capacity of the SFRS. (See NoteA-4.1.8.16.(2).)
3) The shear and overturning resistances of the foundation determined using a bearing stress equal to 1.5times
the factored bearing strength of the soil or rock and all other resistances equal to 1.3times the factored resistances
need not exceed the design forces determined in Sentence4.1.8.7.(1) using R
d
R
o
= 1.0, except that the factor of 1.3
shall not apply to the portion of the resistance to uplift or overturning resulting from gravity loads.
4) A foundation is permitted to have a factored overturning resistance less than the lateral load overturning
capacity of the supported SFRS, provided the following requirements are met:
a) neither the foundation nor the supported SFRS are constrained against rotation, and
b) the design overturning moment of the foundation is
i) not less than 75% of the overturning capacity of the supported SFRS, and
ii) not less than that determined in Sentence4.1.8.7.(1) using R
d
R
o
= 2.0.
(See NoteA-4.1.8.16.(4).)
5) The design of foundations shall be such that they are capable of transferring earthquake loads and effects
between the building and the ground without exceeding the capacities of the soil and rock.
6) In cases where I
E
F
a
S
a
(0.2) is equal to or greater than 0.35, the following requirements shall be satisfied:
a) piles or pile caps, drilled piers, and caissons shall be interconnected by continuous ties in not less than two
directions (see NoteA-4.1.8.16.(6)(a)),
b) piles, drilled piers, and caissons shall be embedded a minimum of 100mm into the pile cap or structure, and
c) piles, drilled piers, and caissons, other than wood piles, shall be connected to the pile cap or structure for a
minimum tension force equal to 0.15times the factored compression load on the pile.
7) At sites where I
E
F
a
S
a
(0.2) is equal to or greater than 0.35, basement walls shall be designed to resist earthquake
lateral pressures from backfill or natural ground. (See NoteA-4.1.8.16.(7).)
8) At sites where I
E
F
a
S
a
(0.2) is greater than 0.75, the following requirements shall be satisfied:
a) piles, drilled piers, or caissons shall be designed and detailed to accommodate cyclic inelastic behaviour when
the design moment in the element due to earthquake effects is greater than 75% of its moment capacity
(see Note A-4.1.8.16.(8)(a)), and
b) spread footings founded on soil defined as Site ClassE or F shall be interconnected by continuous ties in not
less than two directions.
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
9) Each segment of a tie between elements that is required by Clauses(6)(a) or(8)(b) shall be designed to carry
by tension or compression a horizontal force at least equal to the greatest factored pile cap or column vertical load in
the elements it connects, multiplied by a factor of 0.10 I
E
F
a
S
a
(0.2), unless it can be demonstrated that equivalent
restraints can be provided by other means. (See NoteA-4.1.8.16.(9).)
10) The potential for liquefaction of the soil and its consequences, such as significant ground displacement and
loss of soil strength and stiffness, shall be evaluated based on the ground motion parameters referenced in
Subsection1.1.3., as modified by Article4.1.8.4., and shall be taken into account in the design of the structure and its
foundations. (SeeNoteA-4.1.8.16.(10).)
4.1.8.17. Site Stability
1) The potential for slope instability and its consequences, such as slope displacement, shall be evaluated based
on site-specific material properties and ground motion parameters referenced in Subsection1.1.3., as modified by
Article4.1.8.4., and shall be taken into account in the design of the structure and its foundations.
(See Note A-4.1.8.17.(1).)
4.1.8.18. Elements of Structures, Non-structural Components and Equipment
(See NoteA-4.1.8.18.)
1) Except as provided in Sentences(2),(7) and(16), elements and components of buildings described in
Table4.1.8.18. and their connections to the structure shall be designed to accommodate the building deflections
calculated in accordance with Article4.1.8.13. and the element or component deflections calculated in accordance
with Sentence(9), and shall be designed for a lateral force, V
p
, distributed according to the distribution of mass:
where
F
a
= as defined in Sentence4.1.8.4.(7),
S
a
(0.2) = spectral response acceleration value at 0.2 s, as defined in Sentence4.1.8.4.(1),
I
E
= importance factor for the building, as defined in Article4.1.8.5.,
S
p
=C
p
A
r
A
x
/R
p
(the maximum value of S
p
shall be taken as 4.0 and the minimum value of S
p
shall be taken
as 0.7), where
C
p
= element or component factor from Table4.1.8.18.,
A
r
= element or component force amplification factor from Table4.1.8.18.,
A
x
= height factor (1 + 2 h
x
/ h
n
),
R
p
= element or component response modification factor from Table4.1.8.18., and
W
p
= weight of the component or element.
V
p
0.3 F
a
S
a
(0.2) I
E
S
p
W
p
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
Table 4.1.8.18.
Elements of Structures and Non-structural Components and Equipment
(1)
Forming Part of Sentences 4.1.8.18.(1), (2), (3), (6) and (7)
Category Part or Portion of Building
C
p
A
r
R
p
1 All exterior and interior walls except those in Category 2 or 3 1.00 1.00 2.50
2 Cantilever parapet and other cantilever walls except retaining walls 1.00 2.50 2.50
3 Exterior and interior ornamentations and appendages 1.00 2.50 2.50
4 Floors and roofs acting as diaphragms
(2)
–––
5 Towers, chimneys, smokestacks and penthouses when connected to or forming part of a building 1.00 2.50 2.50
6 Horizontally cantilevered floors, balconies, beams, etc. 1.00 1.00 2.50
7 Suspended ceilings, light fixtures and other attachments to ceilings with independent vertical support 1.00 1.00 2.50
8 Masonry veneer connections 1.00 1.00 1.50
9Access floors 1.00 1.00 2.50
10 Masonry or concrete fences more than 1.8 m tall 1.00 1.00 2.50
11
Machinery, fixtures, equipment and tanks (including contents)
that are rigid and rigidly connected 1.00 1.00 1.25
that are flexible or flexibly connected 1.00 2.50 2.50
12
Machinery, fixtures, equipment and tanks (including contents) containing toxic or explosive materials,
materials having a flash point below 38°C or firefighting fluids
that are rigid and rigidly connected 1.50 1.00 1.25
that are flexible or flexibly connected 1.50 2.50 2.50
13 Flat bottom tanks (including contents) attached directly to a floor at or below grade within a building 0.70 1.00 2.50
14
Flat bottom tanks (including contents) attached directly to a floor at or below grade within a building
containing toxic or explosive materials, materials having a flash point below 38°C or firefighting fluids
1.00 1.00 2.50
15 Pipes, ducts (including contents) 1.00 1.00 3.00
16 Pipes, ducts (including contents) containing toxic or explosive materials 1.50 1.00 3.00
17 Electrical cable trays, bus ducts, conduits 1.00 2.50 5.00
18 Rigid components with ductile material and connections 1.00 1.00 2.50
19 Rigid components with non-ductile material or connections 1.00 1.00 1.00
20 Flexible components with ductile material and connections 1.00 2.50 2.50
21 Flexible components with non-ductile material or connections 1.00 2.50 1.00
22
Elevators and escalators
(3)
machinery and equipment as per category 11
elevator rails 1.00 1.00 2.50
23 Floor-mounted steel pallet storage racks
(4)
1.00 2.50 2.50
24
Floor-mounted steel pallet storage racks on which are stored toxic or explosive materials or materials
having a flash point below 38°C
(4)
.
1.50 2.50 2.50
Notes to Table4.1.8.18.:
(1) See Note A-Table 4.1.8.18..
(2) See Sentence (8).
(3) See also the Elevating Devices Safety Regulation
(4) See Sentence (13) and Note A-Table 4.1.8.18.
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
2) For buildings other than post-disaster buildings, seismically isolated buildings, and buildings with supplemental
energy dissipation systems, where I
E
F
a
S
a
(0.2) is less than 0.35, the requirements of Sentence(1) need not apply to
Categories6 through 22 of Table4.1.8.18.
3) For the purpose of applying Sentence(1) for Categories11 and 12 of Table4.1.8.18., elements or
components shall be assumed to be flexible or flexibly connected unless it can be shown that the fundamental period
of the element or component and its connection is less than or equal to 0.06s, in which case the element or
component is classified as being rigid or rigidly connected.
4) The weight of access floors shall include the dead load of the access floor and the weight of permanent
equipment, which shall not be taken as less than 25% of the floor live load.
5) When the mass of a tank plus its contents or the mass of a flexible or flexibly connected piece of machinery,
fixture or equipment is greater than 10% of the mass of the supporting floor, the lateral forces shall be determined by
rational analysis.
6) Forces shall be applied in the horizontal direction that results in the most critical loading for design, except
for Category6 of Table4.1.8.18., where the forces shall be applied up and down vertically.
7) Connections to the structure of elements and components listed in Table4.1.8.18. shall be designed to
support the component or element for gravity loads, shall conform to the requirements of Sentence(1), and shall
also satisfy these additional requirements:
a) friction due to gravity loads shall not be considered to provide resistance to seismic forces,
b) R
p
for non-ductile connections, such as adhesives or power-actuated fasteners, shall be taken as 1.0,
c) R
p
for anchorage using shallow expansion, chemical, epoxy or cast-in-place anchors shall be 1.5, where
shallow anchors are those with a ratio of embedment length to diameter of less than 8,
d) power-actuated fasteners and drop-in anchors shall not be used for tension loads,
e) connections for non-structural elements or components of Category1, 2 or 3 of Table4.1.8.18. attached to
the side of a building and above the first level above grade shall satisfy the following requirements:
i) for connections where the body of the connection is ductile, the body shall be designed for values of C
p
,
A
r
and R
p
given in Table4.1.8.18., and all of the other parts of the connection, such as anchors, welds,
bolts and inserts, shall be capable of developing 2.0times the nominal yield resistance of the body of the
connection, and
ii) connections where the body of the connection is not ductile shall be designed for values of
C
p
= 2.0, R
p
= 1.0 and A
r
given in Table4.1.8.18., and
f) a ductile connection is one where the body of the connection is capable of dissipating energy through cyclic
inelastic behaviour.
8) Floors and roofs acting as diaphragms shall satisfy the requirements for diaphragms stated in Article4.1.8.15.
9) Lateral deflections of elements or components shall be based on the loads defined in Sentence(1) and lateral
deflections obtained from an elastic analysis shall be multiplied by R
p
/I
E
to give realistic values of the anticipated
deflections.
10) The elements or components shall be designed so as not to transfer to the structure any forces unaccounted
for in the design, and rigid elements such as walls or panels shall satisfy the requirements of Sentence4.1.8.3.(6).
11) Seismic restraint for suspended equipment, pipes, ducts, electrical cable trays, etc. shall be designed to meet
the force and displacement requirements of this Article and be constructed in a manner that will not subject hanger
rods to bending.
12) Isolated suspended equipment and components, such as pendent lights, may be designed as a pendulum
system provided that adequate chains or cables capable of supporting 2.0times the weight of the suspended
component are provided and the deflection requirements of Sentence(10) are satisfied.
13) Free-standing steel pallet storage racks are permitted to be designed to resist earthquake effects using rational
analysis, provided the design achieves the minimum performance level required by Subsection4.1.8.
(SeeNoteA-4.1.8.18.(14).)
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
14) Except as provided in Sentence(15), the relative displacement of glass in glazing systems, D
fallout
, shall be
equal to the greater of
a) , where
D
fallout
= relative displacement at which glass fallout occurs, and
D
p
= relative earthquake displacement that the component must be designed to accommodate, calculated in
accordance with Article4.1.8.13. and applied over the height of the glass component, or
b) 13mm.
(See NoteA-4.1.8.18.(15) and (16)(c).)
15) Glass need not comply with Sentence(14), provided at least one of the following conditions is met:
a) I
E
F
a
S
a
(0.2) < 0.35,
b) the glass has sufficient clearance from its frame such that D
clear
≥ 1.25 D
p
calculated as follows:
where
D
clear
= relative horizontal displacement measured over the height of the glass panel, which causes initial
glass-to-frame contact,
C
1
= average of the clearances on both sides between the vertical glass edges and the frame,
h
p
= height of the rectangular glass panel,
C
2
= averages of the top and bottom clearances between the horizontal glass edges and the frame, and
b
p
= width of the rectangular glass panel,
c) the glass is fully tempered, monolithic, installed in a non-post-disaster building, and no part of the glass is located
more than 3m above a walking surface (see NoteA-4.1.8.18.(15) and (16)(c)), or
d) the glass is annealed or heat-strengthened laminated glass in a single thickness with an interlayer no less than
0.76mm and captured mechanically in a wall system glazing pocket with the perimeter secured to the frame
by a wet, glazed, gunable, curing, elastomeric sealant perimeter bead of 13mm minimum glass contact width.
16) For structures with supplemental energy dissipation, the following criteria shall apply:
a) the value of S
a
(0.2) used in Sentence(1) shall be determined from the mean 5% damped floor spectral
acceleration values at 0.2s by averaging the individual 5% damped floor spectra at the base of the structure
determined using Non-Linear Dynamic Analysis, and
b) the value of F
a
used in Sentence(1) shall be 1.
4.1.8.19. Seismic Isolation
1) For the purposes of this Article and Article4.1.8.20., the following terms shall have the meanings
stated herein:
a) “seismic isolation” is an alternative seismic design concept that consists of installing an isolation system with
low horizontal stiffness, thereby substantially increasing the fundamental period of the structure;
b) “isolation system” is a collection of structural elements at the level of the isolation interface that includes all
individual isolator units, all structural elements that transfer force between elements of the isolation system,
all connections to other structural elements, and may also include a wind-restraint system, energy-dissipation
devices, and a displacement restraint system;
c) “seismically isolated structure” includes the upper portion of the structure above the isolation system, the
isolation system, and the portion of the structure below the isolation system;
d) “isolator unit” is a structural element of the isolation system that permits large lateral deformations under
lateral earthquake design forces and is characterized by vertical-load-carrying capability combined with
increased horizontal flexibility and high vertical stiffness, energy dissipation (hysteretic or viscous),
self-centering capability, and lateral restraint (sufficient elastic stiffness) under non-seismic service
lateral loads;
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
e) “isolation interface” is the boundary between the isolated upper portion of the structure above the isolation
system and the lower portion of the structure below the isolation system; and
f) “wind-restraint system” is the collection of structural elements of the isolation system that provides restraint
of the seismically isolated structure for wind loads and is permitted to be either an integral part of the isolator
units or a separate device.
2) Every seismically isolated structure and every portion thereof shall be analyzed and designed in
accordance with
a) the loads and requirements prescribed in this Article and Article4.1.8.20.,
b) other applicable requirements of this Subsection, and
c) appropriate engineering principles and current engineering practice.
(See NoteA-4.1.8.19.(2))
3) For the analysis and modeling of the seismically isolated structure, the following criteria shall apply:
a) a three-dimensional Non-linear Dynamic Analysis of the structure shall be performed in accordance with
Article4.1.8.12. (see NoteA-4.1.8.19.(3)(a)),
b) unless verified from rational analysis, the inherent equivalent viscous damping – excluding the hysteretic
damping provided by the isolation system or supplemental energy dissipation devices – used in the analysis
shall not be taken as more than 2.5% of the critical damping at the significant modes of vibration,
c) all individual isolator units shall be modeled with sufficient detail to account for their non-linear
force-deformation characteristics, including effects of the relevant loads, and with consideration of variations
in material properties over the design life of the structure, and
d) except for elements of the isolation system, other components of the seismically isolated structure shall be
modeled using elastic material properties in accordance with Sentence4.1.8.3.(8).
4) The ground motion histories used in Sentence(3) shall be
a) appropriately selected and scaled following good engineering practice,
b) compatible with
i) a response spectrum derived from the design spectral acceleration values, S(T), defined in
Sentence4.1.8.4.(9) for ground conditions of Site Classes A, B and C, and
ii) a 5% damped response spectrum based on a site-specific evaluation for ground conditions of
Site ClassesD, E and F, and
c) amplitude-scaled in an appropriate manner over the period range of 0.2T
1
to 1.5T
1
, where T
1
is the period
of the isolated structure determined using the post-yield stiffness of the isolation system in the horizontal
direction under consideration, or the period specified in Sentence4.1.8.20.(1) if the post-yield stiffness of the
isolation system is not well defined.
(See NoteA-4.1.8.19.(4).)
4.1.8.20. Seismic Isolation Design Provisions
1) The period of the isolated structure, determined using the post-yield stiffness of the isolation system in the
horizontal direction under consideration, shall be greater than three times the period of the structure above the
isolation interface calculated as a fixed base.
2) The isolation system shall be configured to produce a restoring force such that the lateral force at the TDD at
the centre of mass of the isolated structure above the isolation interface is at least 0.025W
b
greater than the lateral
force at 50% of the TDD at the same location, in each horizontal direction, where W
b
is the portion of W above the
isolation interface.
3) The values of storey shears, storey forces, member forces, and deflections used in the design of all structural
framing elements and components of the isolation system shall be obtained from analysis conforming to
Sentence4.1.8.19.(3) using one of the following values, whichever produces the most critical effect:
a) mean plus I
E
times the standard deviation of results of all Non-linear Dynamic Analyses, or
b) √IE times the mean of the results of all Non-linear Dynamic Analyses.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
4) The force-deformation and damping characteristics of the isolation system used in the analysis and design of
the seismically isolated structures shall be validated by testing at least two full-size specimens of each predominant
type and size of isolator unit of the isolation system, which shall include
a) the individual isolator units,
b) separate supplemental damping devices, if used, and
c) separate sacrificial wind-restraint systems, if used.
5) The force-deformation characteristics and damping value of a representative sample of the isolator units
installed in the building shall be validated by tests prior to their installation.
6) A diaphragm or horizontal structural elements shall provide continuity immediately above the isolation
interface to transmit forces due to non-uniform ground motions from one part of the structure to another.
7) All structural framing elements shall be designed for the forces described in Sentence(3) with R
d
R
o
= 1.0,
except
a) for structures with I
E
< 1.5, all SFRS shall be detailed in accordance with the requirements for R
d
≥ 1.5 and
the applicable referenced design standards, and
b) for structures with I
E
= 1.5, all SFRS shall be detailed in accordance with the requirements for R
d
≥ 2.0 and
the applicable referenced design standards.
8) The height restrictions noted in Table4.1.8.9. need not apply to seismically isolated structures.
9) All isolator units shall be
a) designed for the forces described in Sentence(3), and
b) able to accommodate the TDD determined at the specific location of each isolator unit.
10) The isolation system, including a separate wind-restraint system if used, shall limit lateral displacement due to
wind loads across the isolation interface to a value equal to that required for the least storey height in accordance with
Sentence4.1.3.5.(3).
4.1.8.21. Supplemental Energy Dissipation
1) For the purposes of this Article and Article4.1.8.22., the following terms shall have the meanings
stated herein:
a) “supplemental energy dissipation device” is a dedicated structural element of the supplemental energy
dissipation system that dissipates energy due to relative motion of each of its ends or by alternative means,
and includes all pins, bolts, gusset plates, brace extensions and other components required to connect it to
the other elements of the structure; a device may be classified as either displacement-dependent or
velocity-dependent, or a combination thereof, and may be configured to act in either a linear or non-linear
manner, and
b) “supplemental energy dissipation system” is a collection of energy dissipation devices installed in a structure
that supplement the energy dissipation of the SFRS.
2) Every structure with a supplemental energy dissipation system and every portion thereof shall be designed
and constructed in accordance with
a) the loads and requirements prescribed in this Article and Article4.1.8.22.,
b) other applicable requirements of this Subsection, and
c) appropriate engineering principles and current engineering practice.
(See NoteA-4.1.8.21.(2).)
3) Where supplemental energy dissipation devices are used across the isolation interface of a seismically isolated
structure, displacements, velocities, and accelerations shall be determined in accordance with Article4.1.8.20.
Part 4 – Structural Design Division B: Acceptable Solutions
Division B Revision 2.01 British Columbia Building Code 2018
4) For the analysis and modeling of structures with supplemental energy dissipation devices, the following
criteria shall apply:
a) a three-dimensional Non-linear Dynamic Analysis of the structure shall be performed in accordance with
Article4.1.8.12. (see NoteA-4.1.8.21.(4)(a)),
b) for SFRS with R
d
> 1.0, the non-linear hysteretic behaviour of the SFRS shall be explicitly – with sufficient
detail – accounted for in the modeling and analysis of the structure,
c) unless verified from rational analysis, the inherent equivalent viscous damping – excluding the damping
provided by the supplemental energy dissipation devices – used in the analysis shall not be taken as more
than 2.5% of the critical damping at the significant modes of vibration,
d) all supplemental energy dissipation devices shall be modeled with sufficient detail to account for their
non-linear force deformation characteristics, including effects of the relevant loads, and with consideration of
variations in their properties over the design life of the structure, and
e) except for the SFRS and elements of the supplemental energy dissipation system, other components of the
structure shall be modeled using elastic material properties in accordance with Sentence4.1.8.3.(8).
5) The ground motion histories used in Sentence(4) shall be
a) appropriately selected and scaled following good engineering practice,
b) compatible with a 5% damped response spectrum derived from the design spectral acceleration values, S(T),
defined in Sentence4.1.8.4.(9), and
c) amplitude-scaled in an appropriate manner over the period range of 0.2 T
1
to 1.5 T
1
, where T
1
is the
fundamental lateral period of the structure with the supplemental energy dissipation system.
(See NoteA-4.1.8.21.(5).)
4.1.8.22. Supplemental Energy Dissipation Design Considerations
1) The values of storey shears, storey forces, member forces, and deflections for the design of all structural
framing elements and all supplemental energy dissipation devices shall be obtained from analysis conforming to
Sentence4.1.8.21.(4) using one of the following values, whichever produces the most critical effect:
a) mean plus I
E
times the standard deviation of the results of all Non-linear Dynamic Analyses, or
b) √I
E
times the mean of the results of all Non-linear Dynamic Analyses.
2) The largest interstorey deflection at any level of the structure as determined in accordance with Sentence(1)
shall conform to the limits stated in Sentence4.1.8.13.(3).
3) The force-deformation and force-velocity characteristics of the supplemental energy dissipation devices used
in the analysis and design of structures with supplemental energy dissipation systems shall be validated by testing at
least two full-size specimens of each type of supplementary energy dissipation device.
4) The force-deformation and force-velocity characteristics and damping values of a representative sample of
the supplemental energy dissipation devices installed in the building shall be validated by tests prior to their
installation.
5) Elements of the supplemental energy dissipation system, except the supplemental energy dissipation devices
themselves, shall be designed to remain elastic for the design loads.
6) All structural framing elements shall be designed
a) for an SFRS with R
d
=1.0, using the forces referred to in Sentence(1) with R
d
R
o
= 1.0, except that the SFRS
shall be detailed in accordance with the requirements for R
d
≥ 1.5 and the applicable referenced design
standards, or
b) for an SFRS with R
d
> 1.0, using the forces referred to in Sentence(1) with R
d
R
o
= 1.0, except that the SFRS
shall be detailed in accordance with the requirements for the selected R
d
and the applicable referenced design
standards.
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British Columbia Building Code 2018 Revision 2.01 Division B
7) Supplemental energy dissipation devices and other components of the supplemental energy dissipation
system shall be designed in accordance with Sentence(1) with consideration of the following:
a) low-cycle, large-displacement degradation due to seismic loads,
b) high-cycle, small-displacement degradation due to wind, thermal, or other cyclic loads,
c) forces or displacements due to gravity loads,
d) adhesion of device parts due to corrosion or abrasion, biodegradation, moisture, or chemical exposure,
e) exposure to environmental conditions, including, but not limited to, temperature, humidity, moisture,
radiation (e.g.,ultraviolet light), and reactive or corrosive substances (e.g.,salt water),
f) devices subject to failure due to low-cycle fatigue must resist wind forces without slip, movement, or
inelastic cycling,
g) the range of thermal conditions, device wear, manufacturing tolerances, and other effects that cause device
properties to vary during the design life of the device, and
h) connection points of devices must provide sufficient articulation to accommodate simultaneous longitudinal,
lateral, and vertical displacements of the supplemental energy dissipation system.
8) Means of access for inspection and removal for replacement of all supplemental energy dissipation devices
shall be provided.
Division B: Acceptable Solutions Part 4 – Structural Design
British Columbia Building Code 2018 Revision 2.01 Division B
7) Supplemental energy dissipation devices and other components of the supplemental energy dissipation
system shall be designed in accordance with Sentence(1) with consideration of the following:
a) low-cycle, large-displacement degradation due to seismic loads,
b) high-cycle, small-displacement degradation due to wind, thermal, or other cyclic loads,
c) forces or displacements due to gravity loads,
d) adhesion of device parts due to corrosion or abrasion, biodegradation, moisture, or chemical exposure,
e) exposure to environmental conditions, including, but not limited to, temperature, humidity, moisture,
radiation (e.g.,ultraviolet light), and reactive or corrosive substances (e.g.,salt water),
f) devices subject to failure due to low-cycle fatigue must resist wind forces without slip, movement, or
inelastic cycling,
g) the range of thermal conditions, device wear, manufacturing tolerances, and other effects that cause device
properties to vary during the design life of the device, and
h) connection points of devices must provide sufficient articulation to accommodate simultaneous longitudinal,
lateral, and vertical displacements of the supplemental energy dissipation system.
8) Means of access for inspection and removal for replacement of all supplemental energy dissipation devices
shall be provided.