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Advances in Concrete Construction   Volume 9, Number 1, January 2020, pages 23-31
Evaluation of moment amplification factors for RCMRFs designed based on Iranian national building code
Alireza Habibi, Mehdi Izadpanah and Sina Rohani

Abstract     [Full Text]
    Geometric nonlinearity can significantly affect load-carrying capacity of slender columns. Dependence of structural stability on columns necessitates the consideration of second-order effects in the design process of columns, appropriately. On the whole, the design codes present a simplified procedure for second order analysis of slender columns. In this approximate method, the end moments of columns resulted from linear analysis (first-order) are multiplied by the recommended moment amplification factors of codes to achieve magnified moments of the second-order analysis. In the other approach, the equilibrium equations are directly solved for the deformed configuration of structure, so the resulting moments and deflections contain the influence of slenderness and increase more rapidly than do loads. The aim of this study is to evaluate the accuracy of moment amplification factors of Iranian national building code whose provisions are similar to the ACI requirement. Herein, finite element method is used to achieve magnified end moments of reinforced concrete moment resisting frames, and the outcomes are compared with the moments acquired based on the proposed approximate method by Iranian national building code. The results show that the approximate method of Iranian code for calculating magnified moments has significant errors for both unbraced and braced columns.
Key Words
    geometric nonlinearity; slender columns; design process; linear analysis; reinforced concrete
Alireza Habibi: Department of Civil Engineering, Shahed University, Tehran, Iran
Mehdi Izadpanah: Department of Civil Engineering, Kermanshah University of Technology, Kermanshah, Iran
Sina Rohani: Department of Civil Engineering, University of Kurdistan, Sanandaj, Iran

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