Horizontal Elastic Design Spectrum per ASCE 7-16 with ideCAD

How does ideCAD define horizontal elastic design spectrum, according to ASCE 7-16?

Using the coefficients obtained from the map, horizontal elastic design spectrum curve is automatically determine according to ASCE 7-16.

Due to the need for site-specific analysis for site class F, short-period and long-period site coefficient F_a and F_v are defined by user.

SYMBOLS

F_a = Short-Period Site Coefficient
F_v = Long-Period Site Coefficient for a period of 1.0 seconds
S_MS = Short-period design spectral response acceleration parameter [dimensionless]
S_M1 = Design spectral response acceleration parameter for a period of 1.0 seconds [dimensionless]
S_S = the mapped MCER spectral response acceleration parameter at short periods as determined in accordance with Section 11.4.2,
S₁ = the mapped MCER spectral response acceleration parameter at a period of 1 s as determined in accordance with Section 11.4.2
S_D1 = Design spectral response acceleration parameter for a period of 1.0 seconds
S_DS = Design earthquake spectral response acceleration parameters at short periods
T = Natural vibration period [s]
T₀ =Horizontal elastic design acceleration spectrum corner period [s]
T_S = Horizontal elastic design acceleration spectrum corner period [s]
T_L = Transition period to constant displacement region in horizontal elastic design spectrum [s]
S_a = Horizontal elastic design spectral acceleration [ g]

Horizontal elastic design spectral accelerations S_a are defined in terms of gravity [g] depending on the natural vibration period.

With the spectral response acceleration parameters obtained from USGS depending on the coordinates, the horizontal elastic design spectrum S_a is determined according to the formula below. It is represented by a total of 4 functions, different in each region. It is shown in the graph below.

It’s determined with the equation 11.4-5 from T=0 to T₀.

It’s equal S_DS from T₀to T_s.
It’s determined with the equation 11.4-6 from T_s to T_L.

It’s determined with the equation 11.4-7 for periods greater than T_L.

In the Analysis Settings - Response Spectrum Function tab, the horizontal design spectrum is determined and shown using the design spectral response acceleration parameters.

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