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Evaluating Response Modification Factors of Concentrically Braced and Special Moment Steel Frames in Duplex Buildings Leila Kalani Sarokolayi; Sirous Gholampour dehkordib; Masoud Shafaghati sefidabc Response modification factor (R-factor) is one of the seismic design parameters to consider nonlinear performance of building structures during strong earthquake. Relying on this, many seismic design codes led to reduce earthquake loads imposed to the structure. The present paper tries to evaluate the R-factors of conventional concentric braced frames (CBFs) and special moment frames (MRFs) in duplex steel buildings with level difference in their floors. Since, the R-factor depends on ductility and over strength, the incremental nonlinear static analysis, push over analysis, has been performed on 4, 7 and 10 storey building models with three floor level differences and including CBFs and special MRFs systems in x and y directions of buildings respectively. The results showed that the R-factors for CBFs system in duplex buildings were higher than ones in conventional buildings without floor level differences while for MRFs system it was found that on 4 and 7 storey duplex buildings, the R-factors were decreased and with the increase in building height to 10 storey, they were increased compared to conventional models. منبع دانلود JSEG361427657400.pdf

Comparison of chevron and suspended-zipper braced steel frames Yigit Ozcelik a, Afsin Saritas b,⁎, Patricia M. Clayton a a Department of Civil, Architectural and Environmental Engineering, University of Texas at Austin, Austin, TX 78712, USA b Department of Civil Engineering, Middle East Technical University, Ankara 06800, Turkey a r t i c l e i n f o a b s t r a c t Article history: Received 22 June 2015 Received in revised form 14 November 2015 Accepted 8 December 2015 Available online xxxx a b s t r a c t Suspended-zipper braced frame is a modified configuration of chevron braced frame inwhich zipper columns are added between story beams and a hat truss is attached between top two stories in order to redistribute the unbalanced vertical forces emerging following the brace buckling to avoid the use of deep beams. In this study, three- and nine-story chevron and suspended-zipper braced frames are analyzed to compare their seismic performances. The beams, columns, braces and zipper columns are modeled using nonlinear force-formulation frame elements and nonlinear geometric effects are included by utilizing corotational transformation. Nonlinear static analyses are performed until reaching a roof drift ratio of 3% and a set of twenty ground motion records scaled to match a 10% probability of exceedance in 50 years is used for nonlinear time-history analysis. The results appear to indicate that the lateral load capacity and drift demands for both low-rise chevron and suspendedzipper braced frames are very similar; however, the mid-rise chevron braced frame has a better performance compared to the mid-rise suspended-zipper braced frame. © 2015 Elsevier Ltd. All rights reserved. Keywords: Steel structures Concentrically braced frames Chevron braced frames Suspended-zipper braced frames Nonlinear static analysis Nonlinear time-history analysis 10.1016_j.jcsr.2015.12.019-Comparison-of-chevron-and-suspended-zipper-braced-steel-frames.pdf