A probabilistic model for the evaluation of strong column-weak beam provision for flexible-base buildings subjected to pulse-like ground motions

Abstract

The main objective of this study is to employ a probabilistic approach to determine the appropriate value of the strong column-weak beam ratio (SCWBR) for three mid-to highrise moment frames. These buildings are subjected to pulse-type ground motions. The nonlinear soil-structure interaction (SSI) is also involved as another seismic energy dissipation mechanism. A set of incremental nonlinear dynamic analyses are performed for 91 pulselike ground motions. The proposed approach includes global and local performance criteria. Park-Ang damage index is utilized as the damage measure for columns. In this regard, simple mathematical equations are also derived to quantify the impact of the SCWBR. This framework introduces an upper bound on the SCWBR beyond which further increase of this parameter would not be required to limit the damage of columns. The results indicate that for the 4-story building, the applicability of the SCWBR extends to values as large as 2.4, while for the 8 and 12-story buildings, this is restricted to 1.8 and 1.6, respectively. However, these values substantially depend on the pulse period in such a way that the SCWBR of 1.2 would be sufficient when the pulse period is approaching the fundamental period of structures. The SSI may improve the collapse probability of high-rise structures to a larger extent compared to SCWBR. Nevertheless, its effect can be diminished by more damage of columns at the lower portion of buildings.