Seismic Performance Evaluation Of Reinforced Concrete Frame Based On Modal Incremental Dynamic Analysis

Incremental Dynamic Analysis(IDA) is considered to be the most accurate way to estimate seismic demand and structural capacities in Performance-based earthquake engineering(PBEE). This method involves performing multiple nonlinear dynamic analyses of a structural model under a suite of ground motion records, each scaled to several levels of seismic intensity, The scaling levels are appropriately selected to force the structure through the entire range of behavior, from elastic to inelastic and finally to global dynamic instability, where the structure essentially experiences collapse. However, the implementation of IDA is computationally extremely demanding and time consuming, which makes it difficult to perform in real design conditions. Scholars at home and abroad have carried out a large number of studies on these issues, but related methods that can ensure the accuracy of calculation and at the same time effectively solve the defects of IDA are not universal.Based on above reasons, a simplified approach based on modal incremental dynamic analysis(MIDA) was investigated in this paper. This new approach is a combination of IDA and modal pushover analysis(MPA), and takes advantage of both methods. In order to investigate the efficiency and reliability of this simplified method, Both IDA and MIDA were conducted in the evaluation of anti collapse performance of RC frame structures.The main contents of this paper are as follows:(1) Discuss the collapse mechanism of the RC frame structure under seismic load especially major earthquake effect. Explain the collapse patterns and the failure criteria of RC frame structure. Introduce the evaluation method of the ability of structural seismic collapse resistance;(2) Explain the basic principle and operating procedure of IDA in details. Illustrate the selection principle of ground motion records and various parameters. Establish an5-, 8- and 11-storey RC frame structure to perform IDA procedure and evaluate the seismic collapse resistance ability separately;(3) An 11-story reinforced concrete frame is taken as case study to investigate the efficiency of MIDA. Both IDA and MIDA under ground motion record were conducted respectively. Damage measures, which are important for the seismic vulnerability of buildings, such as maximum displacement and maximum drift ratio were considered. Then the collapse fragility curves from IDA and MIDA were compared, and the errors caused by MIDA are discussed.Numerical results show that MIDA method has good accuracy in seismic performance evaluation. It is reliable and effective to estimate the seismic performance from initial elastic behavior to final collapse globally. Furthermore, comparing to IDA results, the error decreases obviously with the consideration of higher mode effects. In conclusion, under the same accuracy limit, MIDA method reduces the computational effort efficiently, and has better application value and practical significance.