# 15.5.3.2

Values expressed as *impact/capacity ratio* (ECO) are used to control the application limits of linear performance analysis of existing structures . The ECO value is obtained by dividing the total section moment calculated by taking R _{a} =1 under the effect of vertical loads and earthquakes, by the section moment capacity.

ECO values scaled with the cutting force are calculated automatically according to

**Equation (15.1)**.

**ICONS**

**EKO** = Impact / Capacity ratio * R _{a }=* Earthquake Load Reduction Coefficient

*Shear force calculated in the i column*

**V**_{i }=The scaled ECO values with the shear force specified in the clauses** (c)** and** (d) in ****TBDY Article 15.5.3.2** are calculated with** Equation (15.1)** .

In the above equation, the column number on the relevant floor is indicated by the index "i". V _{i} is the shear force consisting of the vertical loads calculated in the i column and the earthquake loads ( loading cases ) taken as R _{a} = 1 , (EKO) _{i} is the Impact / capacity ratio calculated in accordance with **TBDY Article 15.5.2.3 in the** column i . Axial force and biaxial bending interaction are taken into account when calculating ECHO in columns. When creating the interaction diagram, __the current material strength is__ used __by considering the information level coefficient__ .

The line shown in red in the picture below shows the point in the P-M2-M3 three-dimensional system of axial force and biaxial bending consisting of vertical loads and earthquake loads ( load cases ) taken as R _{a} = 1 . It is the curved capacity curve shown with black lines. The length of the line drawn from the starting point to the point PM _{2} -M _{3 shows} the effect value, the length of the line from the starting point to the point that intersects the interaction diagram in the direction of the line drawn to the PM _{2} -M _{3} point shows the capacity value. ECO value is the ratio of these two values.

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