Evaluation and Comparison of Response Modification Factor of the Base-Isolated Steel Moment Frames by Incremental Dynamic Analysis versus Pushover Method
Subject Areas : Analysis of Structure and Earthquake
Hamid Reza
Sadrarhami
1
(Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran)
Farshid
Fathi
2
(Faculty Member, Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran.)
Keywords: Response modification factor, incremental dynamic analysis (IDA), steel structure, Base Isolator, nonlinear static analysis (pushover),
Abstract :
The Response Modification Factor (R), which represents the non-elastic performance of structures during severe earthquakes is widely utilized in Codes to determine the seismic demand and to design the structures. The closer the calculated value of R is to the reality, the more accurate the determination of the required resistance of the structure will be. The common analytical method for calculating the Response Modification Factor of ordinary buildings is the non-linear static analysis (Pushover) method. But the use of this method for buildings with base-isolation is doubtful. Incremental nonlinear dynamic analysis (IDA) is one of the new methods with wide application, which can be a suitable alternative for calculating the R of buildings with isolated bases. In the present research, the Response Modification Factor of the steel moment frame structure equipped with base isolation has been calculated and compared for 5-, 8-, and 12-steel story models by using two methods: the incremental nonlinear dynamic analysis (IDA) versus the Pushover analysis (conventional method). The results indicate that the incremental nonlinear dynamic analysis method is more accurate than the pushover analysis, due to the direct use of earthquake records, as well as considering all the dynamic characteristics of the structure, especially the dynamic characteristics of its base isolator. So that, the Response Modification Factor obtained from the IDA analysis compared to the pushover analysis, exhibits an increase of 2.8% in the 5-story, 16.61% in the 8-story, and 8.84% in the 12-story structures. The Response Modification Factors obtained from the above-mentioned analyzes have been compared with the values recommended in the FEMA P695 Code.
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