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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

Towards Lateral Performance of CBF with Unwanted Eccentric Connection: A Finite Element Modeling Approach Seyed Mehdi Zahrai* and Hamed Bolandi** Received February 21, 2012/Revised January 12, 2013/Accepted March 28, 2013 ·································································································································································································································· Abstract This paper presents a parametric investigation into lateral performance analysis of Concentrically Braced Frames (CBFs) having in-plane eccentricities at the connection of their braces. Nonlinear behavior analyses of a single bay, two-story steel frames with single diagonal concentric braces are taken as numerical examples. Static pushover analyses is carried out to show the impact of eccentricity values (5, 10, and 15 cm), location of the meeting point of brace and frame member axes, and the angle of brace with respect to beam axis. Finite element modeling of the whole members is conducted. Fine meshes are used in regions where inelastic deformations are expected. Numerical results show that in-plane eccentricities can be acceptable within a safe region (max. 10 cm for this specific case). However, no safe region exists for in-plane eccentricity in columns since the strength loss may be significant. Stiffeners are recommended in column web to reduce the strength loss. Their impact is less in strength loss but high in plastic strain developed in the critical region. Eccentricities have positive or negative effects on seismic behavior depending on the geometric properties of the frame, type of eccentricity and bracing configuration. Keywords: in-plane eccentricity, bracing connections, lateral behavior of steel frames, push-over analysis KSCE Journal of Civil Engineering (2014) 18(5):1421-1428 Copyright ⓒ2014 Korean Society of Civil Engineers DOI 10.1007/s12205-014-0094-1 منبع: [Hidden Content] دانلود: [Hidden Content] 8nR6hYFn.pdf