Optimum performance-based design of unsymmetrical 2D steel moment frame

The most commonly used analysis method in performance-based design (PBD) is nonlinear static (NSA). In unsymmetrical 2D frames, unlike for the symmetrical state, NSA should be performed two lateral loading directions. This complicates process of achieving a feasible optimal addition to increasing volume calculations. this study, overcoming issue, two-step approach proposed PBD steel moment-resisting frames (SMRFs). approach, independent steps, structure analyzed with pattern based on first mode shape positive and negative implementation second step conditional satisfactory completion step. objective function takes into account differences between successful unsuccessful steps. constraints considered are acceptance criteria SMRF according FEMA-356 at each performance level. effectiveness has been investigated by employing four meta-heuristic optimization algorithms determine optimum case studies structures having three nine stories.