**6. Results**

The increase of moment strength at point C is taken as the over strength factor computed by XTRACT, ignoring the strength softening effect. The actual moment strength at point C is the product of the factor and the yielding moment. FEMA 356 defines a 0.2 residual strength ratio before plastic hinge eventually fails. Figure 24 presents moment-rotation curves for one of the

**Figure 23.** Performance Level on Generalized Force-Deformation Relations for Concrete Elements (FEMA-356)

254 Engineering Seismology, Geotechnical and Structural Earthquake Engineering

**Generalized Displacement (D/ Dy)**

In-Ground Hinge

Top Column Hinge

columns.

**Generalized Moment (M/**

**Figure 24.** Moment-Rotation Relationship of the Columns

 **My)**

> The results of the pushover analysis are organized in the following pages. Each bent has two pages of results. The first page shows the general characteristics of the bent and the push over curve. The second page shows the results of the step by step push over analysis and the development of hinges. The first and the last bent on the plan are abutments, so they are not included in this report.

> Maximum displacement capacity exhibited is 3.9 inches by the fifth bent. The lowest bent capacity is 2.08 inches by the second bent. The reason for this low displacement capacity in bent number two is because of its shorter columns compared to other bents.

> Using two hinges per column creates a much lower capacity than using only one hinge at the top of the column. The shear force capacity stays almost the same, but the ductility reduces for all bents.
