# Linear Seismic Performance Analysis

**15.5.1. Calculation Methods**

Linear calculation methods to be used to determine the earthquake performance of buildings are Equivalent Earthquake Load Method defined in **4.7** and Mode Combination Method defined in **4.8.2** . The following additional rules will apply to these methods.

**15.5.1.1 -** Buildings for which Equivalent Earthquake Load Method can be applied are given in **Table 4.4** . Additional eccentricity will not be taken into account in the earthquake calculation of buildings. In the calculation of the total equivalent earthquake load (base shear force) according to **Equation (4.19)** and **Equation (4.8)** , R _{a} = 1 will be taken.

**15.5.1.2 - With the** Mod Combination Method, R _{a} = 1 will be taken in earthquake calculation according to **4.8.2** . In the calculation of the internal forces and capacities of the elements compatible with the applied earthquake direction and direction, the internal force directions obtained in the mode dominant in this direction will be taken as basis.

**TBDY Section 4.8.2. Earthquake Calculation with Mode Combination Method**

**4.8.2.1 - In the** Mode Combination Method, the maximum values of the response magnitudes in each vibration mode taken into account by using the earthquake design spectrum in the direction of a given earthquake are calculated by the modal calculation method. The largest asynchronous modal behavior magnitudes calculated for a sufficient amount of vibration modes are then combined statistically to obtain approximate values of the largest behavior magnitudes. Details of the method are given in Annex 4B.