The Design Theory And Method Of Semi Rigid Steel Frame

Along with the rapid development of steel structure industry in China, more and more structures are designed as steel frame. The beam-column connections are designed as hinged connections or rigid connections simply in process of steel frame design, whereas this is not in conformity with the actual situation. Any kind of beam-column connections are the semi-rigid connections in theory, and the mechanics properties of the semi-rigid connecitons must be studied clearly for simulating really the mechanics behavior of the real structures. The two stage design method is adopted in China code for design of steel structures(GB50017-2003), including structures analysis and member design, whereas the two stage design method has obvious deficiencies. The direct analysis design method can consider P-A and P-δ effections, the initial imperfections of the strcutures and the members and the connections stiffness, and can simulate elastic and plastic development of the material and simulate redistribution of internal force of the member. By the direct analysis design method, the force and displacement of structures are calculated with design load value and standard load value, and the members are directly design with the calculation results by the other codes.Two types of semi-rigid connections are selected as object of study, including top and seat angle semi-rigid connection and extended end-plate semi-rigid connection. Based on three-parameters-model theory, the semi-rigid connection steel frames are analyzed with the direct analysis method and are verified by test data. The research results show that the theory and calculation method in the paper is feasible to analyze the semi-rigid steel structures by the direct analysis method, and the theory and calculation method is practical in practical engineering.The main scopes of this paper include:(1) The initial stiffness, ultimate bearing moment and shape coefficient of the top and seat angle semi-rigid connection and of extended end-plate semi-rigid connections are deduced in this paper.(2) The 34 finite element models of top and seat angle semi-rigid connections and the 37 finite element models of extended end-plate semi-rigid connections are built in the paper with ANSYS software. The calculation formula of the ultimate bearing moment, initial stiffness and shape coefficient are verified by the results of the finite element models and the test data from the W.F.Chen data bank.(3) Based on the column curves from the current code for design of steel structures in China, the equivalent initial imperfections of the members is deduced by stability analysis theory of steel structures, and the equivalent initial imperfections include initial geometric imperfections and initial residual stress of the members. The initial imperfections of the members are imported in the software NIDA, and 600 examples are calculated with the software NIDA, including 28 cross sections. The limited load of the members from the software NIDA are comparatively analysis with the limited load of the members from the current the code for design of steel structures of China and the initial equivalent imperfections of the members are verified.(4) The direct analysis method principle is introduced in detail and the stiffness matrix of the pointwise equilibrating polynominal element (PEP element) is deduce to considering initial imperfections of the members, plastic hinge and semi-rigid connections. The two examples are calculated by the software NIDA with the direct analysis method and the calculations method and theory of the semi-rigid steel structures in the paper are verified.