Seismic performance evaluation of Egyptian code-designed steel moment resisting frames

Abstract

Despite the fact that steel is a ductile material, the significant damage, during earthquake events, highlighted the need to thoroughly investigate the seismic performance of steel structures. Seismic design procedures have been developed to enable structures to achieve specific acceptable level of damage under dynamic loads in accordance with particular levels of ductility. The ductility of steel moment resisting frames is developed through flexural yielding of beams, shear yielding of column panel zones, and flexural yielding of columns. Meanwhile, the frame must develop the required ductility without failure in the beam-to-column connection. The observations on panel zone behavior revealed that it can afford high ductility; however, localized deformations at corners of panel zone may increase the likelihood of fracture in vicinity of beam flange welds. On the other hand, the observations on flexural yielding behavior of columns reported potential soft story collapse. Consequently, counting on ductility due to shear yielding of panel zone and flexural yielding of columns is not recommended. Hence, the focus of this study has been directed toward flexural yielding of frame beams. The effect of beam profile slenderness (according to the Egyptian code design limits) has been examined against ductility, over-strength and redundancy with numerical assessment for the anticipated seismic force reduction factor. The reduction factor has been evaluated using both the N2-method and the time history analysis method. Accordingly, a guideline has been established for the Egyptian code provisions to enable professionals to assign the steel moment resisting frame between adequate-ductility, intermediate-ductility and limited-ductility.