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Due to the need for site-specific analysis for site class F, the design spectrum isn’t determined automatically. The reduced design spectrum needs to be imported as a .txt file.
Tip
  • Using the coefficients obtained from the map, the spectrum curve given in

Figure 11.4-1 with Equation 11.4-5 - 11.4-7
  • Codes is automatically determined by the programme.

Info

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İnternational Design Codes

ASCE 7-16 : 11.4.6 Horizontal Elastic Design Spectrum

TSC 2018 : Horizontal Design Response Spectrum

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SYMBOLS

Fa = Short-Period Site Coefficient
Fv = Long-Period Site Coefficient for a period of 1.0 seconds
SMS = Short-period design spectral response acceleration parameter [dimensionless]
SM1 = Design spectral response acceleration parameter for a period of 1.0 seconds [dimensionless]
SS = 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 seconds
SD1 = Design spectral response acceleration parameter for a period of 1.0 seconds
SDS = Design earthquake spectral response acceleration parameters at short periods
T = Natural vibration period [s]
T0 =Horizontal elastic design acceleration spectrum corner period [s]
TS   = Horizontal elastic design acceleration spectrum corner period [s]
TL = Transition period to constant displacement region in horizontal elastic design spectrum [s]
Sa = Horizontal elastic design spectral acceleration [ g]

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Horizontal elastic design spectral accelerations Sa, 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, horizontal elastic design spectrum Sa isdetermined according to the formula below. It is represented by a total of 4 functions, different in each region. It’s shown in the graph below.

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In the Analysis Settings - Response Spectrum Function tab, the horizontal design spectrum is determined and showed by using the design spectral response acceleration parameters., The function of the Design Response Spectrum curve is specified in seismic design codes and spectral response acceleration parameters are used to create this function. In the Design Response Spectrum curve, the spectral accelerations corresponding to 1-s period and corner periods are used to determine these parameters.

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Horizontal Design Response Spectrum is used to consider earthquake effects that results in the largest maximum response to horizontal ground motions.

A standard response spectrum curve defined in seismic codes is defined as follows.

  • For periods less than smaller Tcorner, the design spectral response acceleration, S, shall be taken as as a linear function.

  • For periods greater than or equal to small Tcorner value and less than or equal to greater Tcorner value the design spectral response acceleration, S, shall be taken as equal to maximum spectral response acceleration.

  • For periods greater than or equal to graeter Tcorner value the design spectral response acceleration, S, shall be taken as a fuction of T and spectral response acceleration parameters.

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