The British Columbia Building Code | Notes to Part 4 | Structural Design Pt 1

Division B: Acceptable Solutions Notes to Part 4 Structural Design
British Columbia Building Code 2018 Division B
Notes to Part 4
Structural Design
A-4.1.1.3.(1) Structural Integrity. The requirements of Part 4, including the CSAdesign standards, generally provide a
satisfactory level of structural integrity. Additional considerations may, however, be required for building systems made of components
of different materials, whose interconnection is not covered by existing CSAdesign standards, buildings outside the scope of existing
CSAdesign standards, and buildings exposed to severe accidental loads such as vehicle impact or explosion. Furtherguidance can be
found in the Commentary entitled Structural Integrity in the “User’s Guide – NBC2015, Structural Commentaries (Part 4 of
Division B).”
A-4.1.1.3.(2) Serviceability. Information on serviceability can be found in the Commentary entitled Deflection and
Vibration Criteria for Serviceability and Fatigue Limit States in the “User’s Guide – NBC2015, Structural Commentaries (Part 4 of
Division B).”
A-4.1.1.5.(2) Structural Equivalents. Sentence4.1.1.5.(2) provides for the use of design methods not specified in Part 4,
including full-scale testing and model analogues. This provision is usually used to permit the acceptance of new and innovative
structures or to permit the acceptance of model tests such as those used to determine structural behaviour, or snow or wind loads.
Sentence4.1.1.5.(2) specifically requires that the level of safety and performance be at least equivalent to that provided by design to
Part 4 and requires that loads and designs conform to Section4.1.
Sentence4.1.1.5.(2) and the provision for alternative solutions stated in Clause1.2.1.1.(1)(b)of DivisionA are not intended to allow
structural design using design standards other than those listed in Part4. The acceptance of structures that have been designed to other
design standards would require the designer to prove to the appropriate authority that the structure provides the level of safety and
performance required by Clause1.2.1.1.(1)(b)of DivisionA. The equivalence of safety and performance can only be established by
analyzing the structure for the loads and load factors set out in Section4.1. and by demonstrating that the structure at least meets the
requirements of the design standards listed in Sections4.3. and4.4.
A-4.1.2.1. Loads and Effects. Information on the definitions can be found in the Commentary entitled Limit States Design
in the “User’s Guide – NBC2015, Structural Commentaries (Part 4 of Division B).”
A-4.1.2.1.(1) Temperature Changes. Information on effects due to temperature changes can be found in the Commentary
entitled Effects of Deformations in Building Components in the “User’s Guide – NBC 2015, Structural Commentaries (Part 4 of
Division B).”
A-4.1.2.1.(3) Major Occupancies. In a building containing more than one major occupancy and classified in more than one
Importance Category, the classification of each independent structural system shall be the same as for any part of the building that is
dependent on that structural system and for the highest usage group according to Table4.1.2.1.
A-Table 4.1.2.1. Importance Categories for Buildings.
Low Importance Category Buildings
Low human-occupancy farm buildings are defined in the National Farm Building Code of Canada 1995 as having an occupant
load of 1 person or less per 40 m
2
of floor area. Minor storage buildings include only those storage buildings that represent a
low direct or indirect hazard to human life in the event of structural failure, either because people are unlikely to be affected
by structural failure, or because structural failure causing damage to materials or equipment does not present a direct threat to
human life.
Buildings Containing Hazardous Materials
The following buildings contain sufficient quantities of toxic, explosive or other hazardous substances to be classified in the
High Importance Category of use and occupancy:
petrochemical facilities,
fuel storage facilities (other than those required for post-disaster use), and
manufacturing or storage facilities for dangerous goods.
Effective December 10, 2018 to December 11, 2019
Notes to Part 4 – Structural Design Division B: Acceptable Solutions
Division B British Columbia Building Code 2018
The following types of buildings may be classified in the Normal Importance Category: buildings that are equipped with
secondary containment of toxic, explosive or other hazardous substances, including but not limited to, double-wall tanks, dikes of
sufficient size to contain a spill, or other means to contain a spill or a blast within the property boundary of the facility and
prevent the release of harmful quantities of contaminants to the air, soil, groundwater, surface water or atmosphere, as the case
may be.
A-4.1.3. Limit States Design. Information on limit states design can be found in the Commentary entitled Limit States
Design in the “User’s Guide – NBC2015, Structural Commentaries (Part4 of DivisionB).”
A-4.1.3.2.(2) Load Combinations.
Load Combination Equations
The load combinations in Tables4.1.3.2.-A and4.1.3.2.-B apply to most situations for loadbearing building structures.
Guidance on special situations such as load combinations for fire resistance and building envelopes is given in the Commentary
entitled Limit States Design in the “User’s Guide – NBC2015, Structural Commentaries (Part 4 of Division B).”
Load Cases and Crane Load Effects
The load combinations in Table4.1.3.2.-A are to be evaluated for structures with crane load effects for the scenario where the
crane loads are zero, and for structures without crane loads. The load combinations in Table4.1.3.2.-B are to be evaluated for
structures with crane loads for the scenario where the crane load effects are other than zero.
Crane Loads
Crane-supporting structures that have cranes in multiple parallel bays should be designed for the maximum vertical crane load
with the cranes positioned for the most critical effect in conjunction with a lateral load with each crane in turn positioned for the
most critical effect. For load combinations that include crane loads, additional guidance can be found in CISC/ICCA 2013,
“Crane-Supporting Steel Structures: Design Guide.”
A-4.1.3.2.(4) Effects of Lateral Earth Pressure, H, Pre-stress, P, and Imposed Deformation, T, in Design
Calculations.
Effects of Lateral Earth Pressure, H, in Design Calculations
For common building structures below ground level, such as walls, columns and frames, 1.5 H is added to load combinations
2 to 4. For cantilever retaining wall structures, see the Commentary entitled Limit States Design in the “User’s Guide –
NBC2015, Structural Commentaries (Part 4 of Division B).”
Effects of Pre-stress, P, and Imposed Deformation, T, in Design Calculations
For structures and building envelopes designed in accordance with the requirements specified in the standards listed in
Section4.3., with the exception of Clauses 8 and 18 of CSAA23.3, “Design of Concrete Structures,” P and T need not be
included in the load combinations of Table4.1.3.2.-A. For structures not within the scope of the standards listed in Section4.3.,
including building envelopes, P and T must be taken into account in the design calculations. For recommended load
combinations including T, see the Commentary entitled Limit States Design in the “User’s Guide – NBC 2015, Structural
Commentaries (Part 4 of Division B).”
A-4.1.3.2.(5) Overturning, Uplift or Sliding. Information on overturning, uplift and sliding can be found in the
Commentary entitled Limit States Design in the “User’s Guide – NBC2015, Structural Commentaries (Part4 of Division B).”
A-4.1.3.3.(1) Failure due to Fatigue. Failure due to fatigue of building structures referred to in Section4.3. and designed for
serviceability in accordance with Article4.1.3.6. is, in general, unlikely except for girders supporting heavily used cranes, on which
Article4.1.5.11. provides guidance.
A-4.1.3.3.(2) Vibration Effects. Guidance on vibration effects can be found in the Commentary entitled Deflection and
Vibration Criteria for Serviceability and Fatigue Limit States in the “User’s Guide – NBC 2015, Structural Commentaries (Part 4 o
f
Div
ision B).”
Effective December 10, 2018 to December 11, 2019
Division B: Acceptable Solutions Notes to Part 4 Structural Design
British Columbia Building Code 2018 Division B
A-4.1.3.4.(1) Loads and Load Combinations for Serviceability. The loads and load combinations for serviceability
depend on the serviceability limit states and on the properties of the structural materials. Information on loads and load combinations
for the serviceability limit states, other than those controlled by deflection, can be found in the Commentary entitled Deflection and
Vibration Criteria for Serviceability and Fatigue Limit States in the “User’s Guide – NBC 2015, Structural Commentaries (Part 4 of
Division B).”
A-4.1.3.5.(1) Deflections. Serviceability criteria for deflections that cause damage to non-structural building components can
be found in the standards listed in Section4.3. Information on deflections can be found in the Commentary entitled Deflection and
Vibration Criteria for Serviceability and Fatigue Limit States in the “User’s Guide – NBC 2015, Structural Commentaries (Part 4 of
Division B).” Information on loads and load combinations for calculating deflection can be found in the Commentary entitled Limit
States Design in the “User’s Guide – NBC 2015, Structural Commentaries (Part 4 of Division B).”
A-4.1.3.5.(3) Lateral Deflection of Buildings. The limitation of 1/500 drift per storey may be exceeded if it can be
established that the drift as calculated will not result in damage to non-structural elements. Information on lateral deflection can be
found in the Commentary entitled Wind Load and Effects in the “User’s Guide – NBC2015, Structural Commentaries (Part 4 of
Division B).”
A-4.1.3.6.(1) Floor Vibration. Information on floor vibration can be found in the Commentary entitled Deflection and
Vibration Criteria for Serviceability and Fatigue Limit States in the “User’s Guide – NBC 2015, Structural Commentaries (Part 4 of
Division B).” Information on loads and load combinations for the calculation of vibration can be found in the Commentary entitled
Limit States Design in the “User’s Guide – NBC 2015, Structural Commentaries (Part 4 of Division B).”
A-4.1.3.6.(2) Dynamic Analyses of Floor Vibrations. Information on a dynamic analysis of floor vibrations from
rhythmic activities can be found in the Commentary entitled Deflection and Vibration Criteria for Serviceability and Fatigue Limit
States in the “User’s Guide – NBC 2015, Structural Commentaries (Part 4 of Division B).”
A-4.1.3.6.(3) Lateral Vibration Under Wind Load. Information on lateral vibrations and accelerations under dynamic
wind loads can be found in the Commentary entitled Wind Load and Effects in the “User’s Guide – NBC 2015, Structural
Commentaries (Part 4 of Division B).”
A-4.1.4.1.(6) Counteracting Dead Load Due to Soil. Examples of structures that traditionally employ the dead load of
soil to resist loadings are pylon signs, tower structures, retaining walls, and deadmen, which resist wind uplift and overturning in
light structures.
A-4.1.5.1.(1) Loads Due to Use of Floors and Roofs. In many areas of buildings, such as equipment areas, service rooms,
factories, storage areas, warehouses, museums, and office filing areas, live loads due to their intended use may exceed the minimum
specified loads listed in Table4.1.5.3. In these instances, the probable live load shall be calculated and used as the specified live load for
the design of that particular area.
A-Table 4.1.5.3. Considerations for Live Loads.
Arenas, Grandstands and Stadia
The designer should give special consideration to the effects of vibration.
Attics – Limited Accessibility
Attic live loading is not required when the ceiling below the attic consists of removable panels that permit access to the ceiling
space without loading the ceiling supporting members. Attic live loading is not required in any area of the attic where the lea
st
dim
ension of the attic space is less than 500 mm.
Corridors, Aisles and Rows of Seats
The spaces between rows of seats are typically designed for the loads of the occupancy they serve. Rows of seats typically discharge
into aisles that are designed for the loads used for the rows of seats. Corridors have a minimum width of 1100 mm and may serve
as collectors for aisles; they are therefore part of the exit system and are required to be designed for a minimum live load of
4.8 kPa.
Effective December 10, 2018 to December 11, 2019