Behavior Study Of K Shape Eccentrically Braced Steel Frames Under Cyclic Load

Eccentrically braced steel frames have high strength and extensive good ductility. It is an effective lateral-resistant structure system which is appropriate for high seismic regions. At present, most of the research results in domestic and abroad on eccentrically braced frames are many for the monotonous load function or the links separates from the frame as an independent component carried on under the circulation load function in the research. As a result, the link's actual load-bearing circumstances have remarkable difference. Therefore, embarks from the frame's whole seismic-resistant performance, thoroughly and systematically studies the various parameters' infulence to the seismic-resistant performance of the K shape eccentrically braced steel frames, by even better coordinates the relationship between the structure's strength, rigidity and ductility has the extremely important practical significance regarding the instruction design work.This paper applies nonlinear (material and geometry) finite element method to systematically analyze the overall behaviors of K shape eccentrically braced steel frames under cyclic load for the first time. The load-bearing condition of K shape eccentrically braced steel frames in a variety of situations was really simulated. Through the calculation and analysis of 33 species of 8 series. The major parameters including links' length ,thickness of links' web, ratio of rise to span, section of brace, thickness of links' flange , distance of links' rib ,thickness of links' rib, axial loading of column and so on are studied. The main conclusions are: (1) The link's length which in the range of (1-1.26) M_p/V_p can make theframe's whole seismic-resistant performance fully developed; (2) The smaller ratio of the frame's height to span is, the larger its load-bearing capacity and rigidity, but the poorer its ductility and energy-dissipation. The larger ratio of the frame's height to span is converse. So the ratio should be restricted to 0.5⁰.7; (3) In order to ensure the shear-yielding of link prior to the buckling of brace, the increasing coefficient of brace's axial force η_br can be determined in the range of 1.4—1.6 according to different region's seismic-resistant level; (4)...