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

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.