# 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 C

_{s}is determined automatically by**Equation 12.8-2, 12.8-3, 12.8-4, 12.8-5**and**12.8-6**.

R, I

_{e}and T_{L}coefficients in the equations are defined by user.

R and I

_{e}coefficients are selected by the user in the analysis settings wizard and report results are checked automatically.

**SYMBOLS**

**C _{s} **= The seismic response coefficient

**S**= The design spectral response acceleration parameter at a period of 1.0 s,

_{D1}**S**= The design spectral response acceleration parameter in the short period range

_{DS }**R**= The response modification factor in Table 12.2-1

**I**= The Importance Factor

_{e}**T**= The fundamental period of the structure (s)

**T**= Long-period transition period (s)

_{L}**S**= The mapped maximum considered earthquake spectral response acceleration parameter

_{1}**12.8.1.1 Calculation of Seismic Response Coefficient**

The seismic response coefficient, C_{s}, is determined by the following equation.

The value of C_{s} computed with Eq. (12.8-2) need not exceed the following:

for T ≤ T_{L}

for T > T_{L}

C_{s} should not be less than