Evaluation of Ductility Reduction Factor for X-braced Steel Frames Which are Braced in Two End spans

Document Type : Research Article


Faculty of Civil Engineering, Urmia University of Technology, Urmia, Iran


In this study, the ductility reduction factor of Ordinary Concentrically Braced Frames
(OCBFs) and special concentrically braced frames (SCBFs) which are braced concentrically in two end
sides of frames, is evaluated. The results confirmed that, using SCBFs will reduce about 15 to 45 percent
of total used material for one to 16 story frames respectively. In addition, for all of the 16 ordinary
X-braced frames, which have 1 to 16 story height, calculated ductility reduction factor exceeds from
ASCE7’s proposed one, except for 16 stories frame. For studied frames, which are braced in two end
sides, using the X-bracing system, the results confirmed that ductility demand is achievable without any
significant problem. In addition, results indicated that although the response modification factor which is
proposed by Iranian seismic design code (2800 standard), is more logical than ASCE7’s one, for frames
which are braced in the end sides, the response modification factor should be taken less than 5.5.


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