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By using the coefficients obtained from the map by the program, the spectrum curve given in Figure 11.4-1 with Equation 11.4-3 - 11.4-3 is automatically obtained. |
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
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]
Horizontal elastic design spectral accelerations Sa, which are the ordinates of the horizontal elastic design spectrum for any earthquake ground motion level considered, are defined in terms of the gravitational [ 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 iscalculated according to the formula below . It is represented by a total of 4 functions, different in each region, or the horizontal elastic design spectrum. It’s shown in the graph below.
It’s calculated with the equation 11.4-5 from T=0 to T0 .
It’s equal SDS from T0 to Ts .
It’s calculated with the equation 11.4-6 from Ts to TL .
It’s calculated with the equation 11.4-7 for periods greater than TL.
In the Analysis Settings Wizard - Design Spectrums tab, the horizontal design spectrum is calculated and graphed by using the design spectral response acceleration parameters determined with online and offline options depending on the coordinates.
| Note |
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In Analysis Settings Wizard - Design Spectrums tab, horizontal design spectrum is calculated by using design spectral acceleration coefficients determined with online and offline options depending on the coordinates and its graph is created automatically. |
| Info |
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Due to the need for site-specific analysis for site class F, the calculation is not made in the above way. The reduced design spectrum needs to be imported as a .txt file. |
Example
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Parameters: Ss and S1 values have been taken from ideCAD Wizard Turkey Map (ideCAD İstanbul office location). Other values have been calculated from above equations.
TL has been taken 6 s for this calculation. According to ASCE 7-16, TL is taken from USA Earthquake Hazard Maps.
