An Analytical Study on the Impact of Beam Axial Forces on the Structural Response of Braced-Connected Columns in Steel Concentrically Braced Frames
Subject Areas : Seismic Analysis and Designsasan mehdinejad 1 , alireza faroughi 2 , faridreza asgharifar 3
1 - Department of Civil Engineering, NT.C., Islamic Azad University, Tehran, Iran.
2 - Assistant Professor, Department of Civil Engineering, ET.C., Islamic Azad University, Tehran, Iran
3 - Department of Civil Engineering, ET.C., Islamic Azad University, Tehran, Iran
Keywords: Special concentrically braced frame (SCBF), Chevron bracing, Beam unbalanced force, Pushover analysis. ,
Abstract :
In steel braced structures, different bracing configurations have a direct impact on the distribution of internal forces. Due to the presence of unbalanced forces in the bracing system, the axial forces developed in the beams of braced bays V and inverted V-(chevron) can significantly affect the seismic behavior of the structure. This axial force may increase the in-plane bending moments in the columns and compromise their stability. Accordingly, the present study investigates the effect of axial forces generated in the beams of special concentrically braced frames (SCBFs) and their impact on the connected columns. Structural models were developed for three building frames with 5, 10, and 15 stories using SAP2000 software, incorporating bracing configurations in bays V and inverted V-(chevron). Nonlinear pushover analysis has been employed as a method for evaluating the seismic behavior of these structures, and the results concerning axial force distribution in the beams and the resulting moments in the braced frame columns have been analyzed and compared. The findings indicated that, at the target displacement, the axial forces in the braced bay beams can increase the moments in the columns by up to 5% of their flexural capacity, in addition to the existing axial loads.
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