Structural Influencing Coefficient Of Concentrically X-braced Steel Frames

This paper generalizes the calculation of earthquake action and the value of structural influencing coefficient R. Compared with many codes for seismic design, Code for Seismic Design of Buildings (GB50011-2001) sets the same earthquake action and the same value of R coefficient (2.8125) without taking account of different structural systems. This is unreasonable. Steel structures have characteristic of good ductility and dissipative ability. So the Code (GB50011-2001) sets higher earthquake action and lower value of R coefficient for steel structures.Iteration method is utilized to determine suitable value of R for a concentrically X-braced steel frame. Detailed steps of this method are descripted and the difficulties and importance are mentioned.Based on the Code (GB50011-2001), 23 concentrically X-braced steel frames are designed and their structural coefficients are obtained. The result indicates earthquake actions of less than ten stories concentrically X-braced steel frame which is designed according to the Code (GB50011-2001) are higher. It is suggested to reduce earthquake actions, that is to say, R=3.5. According to statistical processing and analysis of 23 examples, variation regularities of structural coefficient, ductility coefficient, overstrength coefficient and displacement amplification coefficient are acquired.