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The program uses the Equivalent Static Force Procedure from NBC 4.1.8.11 to generate seismic loads.
Information about the following aspects of this procedure is found under Site Information;
Full lists of the following are found in the Seismic Load Generation Details program output:
The symbols and equations are shown below:
Symbols:
V - lateral seismic design force at base W - total seismic dead load
Fx - lateral force applied to level analysed Wi - weight of level in sum
Wx - portion of W assigned to level analysed hx - height of level analysed
Ta - fundamental period of vibration in s hi - height of level in sum
F(T) - site coefficient for spectral acceleration hn - height of top level
Fa = F(0.2); used in IeFaSa(0.2) limit Ft - top floor force
S(T) - design spectral response acceleration Mv - higher mode factor
Sa(T) - 5% damped spectral response acceleration Ie - importance factor
Rd - ductility force modification factor PGA - peak ground acceleration
Ro - overstrength force modification factor PGAref - PGA used for F(T)
J - overturning reduction coefficient at base Jx - J at level analysed
Equations:
V = S(Ta) Mv Ie W / (Rd Ro) 4.1.8.11.(2)
V max = max(2/3 S(0.2),S(0.5)) Ie W / (Rd Ro) 4.1.8.11.(2)(c)
S(T) = Sa(T) F(T, PGAref, Site Class) 4.1.8.4.(5),(9)
Mv = Mv(Ta, SFRS, S(0.2)/S(5.0)) 4.1.8.11.(6)
Rd,Ro = Rd,Ro(Type of SFRS) 4.1.8.9
Ta = 0.05 hn^(3/4), unless over-ridden 4.1.8.11.(3)(c)
Ta max = 2.0 Ta calculated above 4.1.8.11.(3)(d)(iii)
PGAref = 0.8 PGA if Sa(0.2)/PGA < 2.0 4.1.8.4.(4)
Ft = 0.07 Ta V; Ft max = 0.25 V 4.1.8.11.(7)
Fx = (V - Ft) Wx hx / SUM(Wi hi) 4.1.8.11.(7)
J = J(Ta, SFRS, S(0.2)/S(5.0)) 4.1.8.11.(6)
Jx = J + (1 - J)(hx / 0.6 hn) if hx < 0.6 hn 4.1.8.11.(8)