# General Principles and Conditions for Seismic Analysis

The rules for earthquake calculation in linear performance analysis and nonlinear performance analysis applied in existing structures are defined in **TBDY 15.4** . While defining the earthquake effects in the performance analysis, the structural system behavior coefficient, the excess strength coefficient and the building importance factor are not applied (R=D=I=1). Component capacities are determined according to the existing material strengths and building information level coefficients. The building performance evaluation is made according to the results obtained with the existing material strengths calculated by taking into account the earthquake calculation made using rod and shell finite elements and the knowledge level coefficient, within the framework of the rules specified in **TBDY 15.4 .**

**15.4. GENERAL PRINCIPLES AND RULES ON EARTHQUAKE ACCOUNT**

**15.4.1 -** According to this section of the Regulation, the purpose of earthquake calculation is to determine the earthquake performance of existing or strengthened buildings. For this purpose **15.5** as defined in *linear* or **15.6** 'defined in a *non-linear* calculation method used. However, it should not be expected that performance evaluations to be made with these methods, which are theoretically based on different approaches, will give exactly the same result. The general principles and rules described below apply to both types of methods.

**15.4.2 - In** the definition of the earthquake effect, the horizontal elastic design spectrum given in **2.3.4** or **2.4.1** shall be used for earthquake ground motion levels determined according to **2.2** . Building Importance Factor defined in **3.1.2 will** not be applied in earthquake calculation *(I = 1.0).*

**15.4.3 -** Earthquake performance of the buildings will be evaluated under the combined effects of vertical loads and earthquake effects on the building. In the earthquake calculation, masses will be defined according to **4.5.9** .

**15.4.4 -** Earthquake forces will be exerted on the building in both directions and in both directions separately.

**15.4.5 -** The structural system model of the building will be prepared with sufficient accuracy to calculate the internal forces, displacements and deformations that will occur in the structural elements under the common effects of earthquake effects and vertical loads.

**15.4.6 - In** buildings where floors operate as a rigid diaphragm in the horizontal plane, two horizontal displacements on each floor and degrees of freedom of rotation around the vertical axis will be taken into account. Storey degrees of freedom will be defined at the center of mass of each floor, and additional eccentricity will not be applied.

**15.4.7 -** Uncertainties in the load-bearing systems of the existing buildings will be reflected in the calculation methods through the *information level coefficients* defined in **15.2** according to the scope of the data collected from the building .

Columns defined as short columns according to **15.4.8 - 7.3.8 shall** be defined with their real free lengths in the structural system model.

**15.4.9 -** Conditions for defining the interaction diagrams of reinforced concrete sections under one or biaxial bending and axial force are given below:

**(a) In the** earthquake calculation , the *current strengths of* concrete and reinforcement steel determined according to the knowledge level defined in **15.2** shall be taken as basis.

**(b)** The maximum pressure unit deformation of concrete can be taken as 0.0035, and the maximum unit deformation of reinforcing steel can be taken as 0.01.

**(c)** Interaction diagrams can be appropriately linearized and modeled as polyline or multiplanar diagrams.

**15.4.10 - In the** definition of element sizes of reinforced concrete systems, the joint zones can be considered as rigid end zones.

**15.4.11 -** Effective section stiffnesses of the cracked section shall be used in reinforced concrete elements under the effect of bending. Effective cross-section stiffnesses will be calculated according to **4.5.8** .

**15.4.12 - In the** calculation of the positive and negative plastic moments of the beams with reinforced concrete tray, the table concrete and the reinforcement inside can be taken into account.

**15.4.13 - In the** case of insufficient clamping or lap length in reinforced concrete elements, the yield stress of the relevant reinforcement in the calculation of the section capacity moment will be reduced by the ratio of the interlocking or lacking in lap length.

**15.4.14 - In** cases where deformations in the ground may affect the behavior of the structure, the soil properties will be reflected in the analysis model.

**15.4.15 -** Other principles given in **Chapter 3** , **Chapter 4** and **Chapter 5** regarding modeling apply.

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