Conventional analysis and design of steel frames are usually carried out under the assumption that connections joining the beams and columns are either fully rigid or ideally pinned. In fact,as evident from experimental observatiops,all connections used in current practice possess stiffness which fall between the extreme cases of fully rigid and ideally pinned. And the end-plate connection is a typically kind of semirigid connection. This paper presents the normal types of the semirigid connections used in multistory steel frames. Using the initial connection stiffness and the moment-rotation (M-Φ) curve,obtained from both experiment and finite element method,and taking the semirigid end-plate connection as a spring element,a FEM model is set up by ansys to calculate and analyze. The internal forces and deformations of the steel frames with semirigid connections and rigid connections are discussed, and the influence of semirigid connections on the multistory steel frames design is studied in this paper. The result shows that the steel frames with semirigid connections are different from that with rigid connections. The semirigid connection can decrease the negative end moment of beams and increase the positive moment at the mid-span of beam, and increase the deformations on the top and between the stories,and make enlargements of shear deformation. The flexibility of the connections affects the behavior of the frames, and their influences can not be ignored in the steel frames design and analysis.
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