On seismic vulnerability assessment by means of limit analysis of frames with progressive damage.

In this study a simplified bilinear capacity curve of a frame structure is reconstructed by means of a limit analysis strategy based on the implementation of genetic algorithms. The proposed procedure takes into account the second order effects considering a post-yielding softening branch. In order to consider the progressive damage in the frame, the pre-yielding branch is determined with reference to a linear model where rotational springs are introduced in some critical sections of the frame. The calibration of the stiffness of each rotational spring is performed considering the bending moments at the corresponding section when the first plastic hinge in the frame opens. The results obtained through the proposed simplified strategy are validated with well-established approaches based on nonlinear static analyses, showing the reliability and the computational efficiency of this methodology. [ABSTRACT FROM AUTHOR]