Seismic Evaluation of Frame with Belt Truss by Incremental Modified Pushover Analysis (IMPA)

Abstract

Nowadays, nonlinear static and dynamic analyses methods are rapidly expanding to evaluate the seismic performance of structures. Nonlinear dynamic analyses methods require a large amount of computations and are relatively time consuming. This fact has led to the emergence of novel methods based on the concepts of nonlinear static and dynamic analyses. One of the most widely used structures in tall buildings is a combination of the two popular building structures: Bundled tube frame and belt truss. This structural form is effective in reducing the structure responses to lateral loadings. In this paper, two 20-story Steel buildings with different arrangement of resistant rigid belt truss in the 19th and 20th stories have been evaluated under 7 pairs of far and near-field scaled ground motion. Incremental dynamic (IDA), Incremental modified Pushover (IMPA), modal pushover (MPA), and dynamic time history analyses have been conducted to evaluate the seismic response of the structures. The accuracy of the IMPA method has been compared to that of the Incremental Dynamic Analysis (IDA), and a comparison has been also made between nonlinear behavior of the studied models, with and without the belt truss. Results indicate the significant difference in the story drift in the three aforementioned structural configurations under high-amplitude speed pulses. Structures stiffened with belt truss at higher levels of PGA have collapsed and the seismic capacity of the frame has been increased in the upper floors. Maximum relative displacement has been occurred in the inelastic response area near the middle stories.

Keywords

• nonlinear analysis
• incremental dynamic analysis
• incremental modified nonlinear static analysis
• seismic performance
• belt truss