# Design Spectrum Reduced by Respose Modification (4.4.1)

**By** using the parameters determined in **2.3.4** and **4.2.1** , the Reduced Design Spectral acceleration, S _{aR} (T) is determined automatically according to **Equation 4.8** .

**Symbols**

* S _{DS} =* Short period design spectral acceleration coefficient [dimensionless]

*Design spectral acceleration coefficient for a period of 1.0 seconds [dimensionless]*

**S**_{D1}=*Natural vibration period [s]*

**T =***Horizontal elastic design acceleration spectrum corner period [s]*

**T**_{A}=*Horizontal elastic design acceleration spectrum corner period [s]*

**T**_{B}=*Transition period to constant displacement region in horizontal elastic design spectrum [s]*

**T**_{L }=*Horizontal elastic design spectral acceleration [g]*

**S**_{ae}(T) =*Reduced design spectral acceleration [g]*

**S**_{aR}(T) =*Strength Excess Coefficient*

**D =***Building Importance Coefficient*

**I =***Structural System Behavior Coefficient*

**R =***Predicted ductility capacity and Seismic Load Reduction Coefficient depending on the period*

**R**_{a}(T) =The reduced design spectral acceleration * S _{aR} (T),* which is the ordinate of the reduced design acceleration spectrum for a given natural vibration period

*T*, used to determine the reduced earthquake loads in the horizontal direction

*,Horizontal Design Response Spectrum ,*

**, is that of Sae (T)***'toDetailed Explanation (Appendix-4A) is obtained by dividing the Earthquake Load Reduction Coefficient.*

**R (TA)**On the Analysis Settings Wizard - Design Spectra tab, the spectral acceleration coefficients obtained from AFAD based on the coordinates and the horizontal elastic design spectrum * Sae (T) are* calculated according to the formula below . Horizontal Design Response Spectrum , it is represented by a total of 4 functions, different in each region, and shown with the graph below.

According to the carrier system type, using the R and D coefficients obtained from Table 4.1, * R (Ta)* is calculated as follows:

The reduced design spectral acceleration * S _{aR} (T)* is represented by the graph: