The Ontario Building Code  Site Properties
4.1.8.4. Site Properties
(1) The peak ground acceleration (PGA) and the 5% damped spectral response acceleration values, S_{a}(T), for the reference ground conditions (Site Class C in Table 4.1.8.4.A.) for periods T of 0.2 s, 0.5 s, 1.0 s, and 2.0 s, shall be determined in accordance with Subsection 1.1.2. and are based on a 2% probability of exceedance in 50 years.
(2) Site classifications for ground shall conform to Table 4.1.8.4.A. and shall be determined using _{S} except as provided in Sentence (3).
(3) If average shear wave velocity, _{S}, is not known, Site Class shall be determined from energycorrected Average Standard Penetration Resistance, _{60}, or from soil average undrained shear strength, s_{u}, as noted in Table 4.1.8.4.A., _{60}and s_{u} being calculated based on rational analysis.
(4) Acceleration and velocitybased site coefficients, F_{a} and F_{v}, shall conform to Tables 4.1.8.4.B. and 4.1.8.4.C. using linear interpolation for intermediate values of S_{a}(0.2) and S_{a}(1.0).
(5) Sitespecific evaluation is required to determine F_{a} and F_{v} for Site Class F.
(6) 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_{a} and F_{v} may be determined as described in Tables 4.1.8.4.A., 4.1.8.4.B., and 4.1.8.4.C. by assuming that thesoils are not liquefiable.
(7) The design spectral acceleration values of S(T) shall be determined as follows, using linear interpolation for intermediate values of T:
S(T) = FaSa(0.2) for T≤0.2 s
= F_{v}S_{a}(0.5) or F_{a}S_{a}(0.2), whichever is smaller for T = 0.5 s
= F_{v}S_{a}(1.0) for T = 1.0 s
= F_{v}S_{a}(2.0) for T = 2.0 s
= F_{v}S_{a}(2.0)/2 for T ≥4.0 s
Table 4.1.8.4.A.
Site Classification for Seismic Site Response
Forming Part of Sentences 4.1.8.4.(1) to (3)
Item  Column 1  Column 2  Column 3  Column 4  Column 5 
 Site Class  Ground Profile Name  Average Properties in Top 30 m 
 


 Average Shear Wave Velocity, _{S} (m/s)  Average Standard Penetration Resistance, _{60}  soil Undrained Shear Strength, s_{u} 
1.  A  Hard rock^{(1) (2)}  _{S} > 1500  N/A  N/A 
2.  B  Rock^{(1)}  760<_{S} ≤1500  N/A  N/A 
3.  C  Very dense soil and soft rock  360<_{S} <760  _{60}> 50  s_{u} > 100kPa 
4.  D  Stiff soil  180<_{S} <360  15 ≤_{60} ≤50  50 kPa < s_{u} ≤100 kPa 
5.  E  Soft soil  _{S} <180  _{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 
 
6.  F  Other soils^{(3)}  Sitespecific evaluation required 

Notes to Table 4.1.8.4.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.
^{(2)} If_{S} has been measured insitu, the F_{a} and F_{v} values derived from Tables 4.1.8.4.B. and 4.1.8.4.C. may be multiplied by (1500/_{S})^{1/2}.
^{(3)} Othersoils 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.
Table 4.1.8.4.B.
Values of F_{a} as a Function of Site Class and S_{a}(0.2)
Forming Part of Sentence 4.1.8.4.(4)
Item  Column 1  Column 2  Column 3  Column 4  Column 5  Column 6 
 Site Class  Values of F_{a} 





 S_{a}(0.2)≤0.25  S_{a}(0.2)=0.5  S_{a}(0.2)=0.75  S_{a}(0.2)=1.00  S_{a}(0.2)≥1.25 
1.  A  0.7  0.7  0.8  0.8  0.8 
2.  B  0.8  0.8  0.9  1.0  1.0 
3.  C  1.0  1.0  1.0  1.0  1.0 
4.  D  1.3  1.2  1.1  1.1  1.0 
5.  E  2.1  1.4  1.1  0.9  0.9 
6.  F  ^{(1)}  ^{(1)}  ^{(1)}  ^{(1)}  ^{(1)} 
Notes to Table 4.1.8.4.B.:
^{(1)} See Sentence 4.1.8.4.(5)
Table 4.1.8.4.C.
Values of F_{v} as a Function of Site Class and S_{a}(1.0)
Forming Part of Sentence 4.1.8.4.(4)
Item  Column 1  Column 2  Column 3  Column 4  Column 5  Column 6 
 Site Class  Values of F_{v} 





 S_{a}(1.0)≤0.1  S_{a}(1.0)=0.2  S_{a}(1.0)=0.3  S_{a}(1.0)=0.4  S_{a}(1.0)≥0.5 
1.  A  0.5  0.5  0.5  0.6  0.6 
2.  B  0.6  0.7  0.7  0.8  0.8 
3.  C  1.0  1.0  1.0  1.0  1.0 
4.  D  1.4  1.3  1.2  1.1  1.1 
5.  E  2.1  2.0  1.9  1.7  1.7 
6.  F  ^{(1)}  ^{(1)}  ^{(1)}  ^{(1)}  ^{(1)} 
Notes to Table 4.1.8.4.C.:
^{(1)} See Sentence 4.1.8.4.(5)