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Seismic Response Coefficient for Equivalent Lateral Force Method per ASCE 7-16 with ideCAD

How does ideCAD calculate the seismic response coefficient according to ASCE 7-16?

  • The seismic response coefficient Cs is determined automatically by Equation 12.8-2, 12.8-3, 12.8-4, 12.8-5 and 12.8-6.

  • R, Ie and TL coefficients in the equations are defined by user.

  • R and Ie coefficients are selected by the user in the analysis settings wizard and report results are checked automatically.


Cs = The seismic response coefficient
SD1 = The design spectral response acceleration parameter at a period of 1.0 s,
SDS = The design spectral response acceleration parameter in the short period range
R = The response modification factor in Table 12.2-1
Ie = The Importance Factor
T = The fundamental period of the structure (s)
TL = Long-period transition period (s)
S1 = The mapped maximum considered earthquake spectral response acceleration parameter Calculation of Seismic Response Coefficient

The seismic response coefficient, Cs, is determined by the following equation.

The value of Cs computed with Eq. (12.8-2) need not exceed the following:

for T ≤ TL

for T > TL

Cs should not be less than

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