Nonlinear Analysis Methods for Evaluating Seismic Performance of Multi-Story RC Buildings

ABSTRACT: A major challenge in performance-based earthquake engineering is to develop simple and practical methods for estimating capacity level and seismic demand on structures by taking into account their inelastic behavior. Researchers and engineers certainly prefer to use nonlinear static methods over complicated nonlinear time-history methods. However, in Nonlinear Static procedure both predetermined target displacement and force distribution pattern are based on a false assumption that the structural behavior and its responses are dominated by the fundamental vibration modes. Therefore, over the past decades, there have been a great number of studies on considering higher mode contribution in nonlinear static results. However, their major drawback is that these approaches are inevitably more complex and time consuming compared to a single-run pushover analysis. The primary aim of this work is to perform and compare different nonlinear analysis methods for evaluating the seismic performances of structures. For these purposes, three models are considered to represent low-rise, medium-rise and high-rise structures. This consist of a moment resisting reinforced concrete structures with no shear walls, located in a high-seismicity region of Turkey. They are designed according to Turkish Earthquake Code 2007 and TS 500-2000 codes, considering both seismic and gravity loads. The Displacement-based Adaptive Pushover Analysis (DAP), which was proposed by Antoniou and Pinho (2004), is one of the performance assessments tool for improving the accuracy of the obtained results of nonlinear static analysis in estimating the seismic demands of the structures. In this thesis, reliability of the DAP in estimating the seismic response of 3, 8 and 12-story moment resisting reinforced concrete frames responding in the inelastic range is demonstrated. Therefore, Incremental Dynamics Analysis (IDA), by applying a large set of natural records, and FEMA 440 static pushover procedure are performed for comparison. The capacity curves of the structures, as derived by both DAP and FEMA440 pushover curves are compared with the IDA envelopes by using SeismoStruct software. Performance levels of structures are also estimated and compared by performing DAP and Incremental Dynamic Analysis using SeismoStruct software and, FEMA440 pushover analysis using SAP2000 program. Results are presented and discussed for advantage and disadvantage of procedures. It is demonstrated that Displacement-based Adaptive Pushover Analysis is adequate for estimating seismic response of reinforce concrete frame and represents an alternative simpler procedure compared to IDA. The DAP method not only automates the pushover analysis, but also improves the accuracy of its results in estimating the seismic demands of the structure. Keywords: Multi-Mode Pushover Analysis, Incremental Dynamic Analysis, Displacement-based Adaptive Pushover Analysis, and Nonlinear Static Analysis. …………………………………………………………………………………………………………………………