Global P-Delta effects in seismic demand evaluation of vibration controlled steel frames

Abstract

The goal of the research was to investigate the effect of global P-Delta on the seismic response of structures. A SAC II three story structure and a reduced order portal frame were the focus of study. The motivation to carry out the research was to look at a reduced order model and determine how the various parameters affect the response. In addition, the suitability of using reduced order model for seismic response evaluation was considered. SAP 2000 was used for modeling and MATLAB 5.3 was used for the dynamic analysis. Pushover analysis was used to obtain a reduced order model, i.e. the portal frame model whose structural properties matched with the SAC II structure. Responses of three different types of control systems were also studied by adding supplemental control devices to the structure. The following conclusions were drawn from the study and are: 1) P-Delta was determined to be critical and affects the response of the system; 2) addition of control devices reduces the effect of P-Delta; 3) an isolation control system performed the best in reducing the drift demands below the negative stiffness range.