Study On The Behavior And Design Of High-strength Bolted Endplate Connections In Light-steel Gabled Frames

Having high efficiency in design and construction of steel structures, the bolted endplate connections were adopted widely as a kind of beam-to-column connection in light-steel gabled frames.Having only some limited experimental and analytical studies carried out, current design codes give little guidelines on the design and behavior of connections. This also limits the effective use of numerical models to simulate the structural global behavior, since in these models the characteristics of the actual semi-rigid connections is idealized as fully rigid / pinned.The main objective of this thesis was to establish nonlinear finite element analysis procedures capable of predicting the behavior of bolted endplate connections and to develop both an analytical design method and a practical expression regarding the moment-rotation characteristics of extended endplate connections that can be incorporated in the global analysis of structures.To investigate the structural behavior and failure mechanism, one configuration of high-strength bolted extended endplate connections, interior beam-to -column splice connection, was considered. Three-dimensional finite element technique to investigate the structural behavior of bolted endplate connections was developed.Nine FE numerical cases were performed with a variation of the following parameters: thickness of endplate, diameter of bolt, preload of bolt, thickness of column flange . And the influence of these parameters was presented. In the FE model, SOLID45, 8-node solid elements were used to discretize the endplate, column, beam, bolts and related stiffeners. Pretensions in bolts were simulated by defining the pretension section and generating PRETS179 elements in the meshed bolt shanks. Contact elements, both TARGE170 and CONTA173, were also employed to model all contact problems in the connection including the contact between column flange and endplate, the contact between column flange and bolt shanks, the contact between endplate and bolt shanks, the contact between column flange and bolt nuts, and the contact between endplate and bolt heads.Further more, based on the design method of endplate connections given in EC3 , the initial stiffness and the ultimate moment capacity of the connections were calculated. The validity and reliability of the FEM were checked against the results from those simplified analytical method of EC3.It was found that the EC3 calculation has the high precision about the ultimate moment capacity of the connections. But regarding the gabled frames has the column web stiffened generally , which the column web stiffness in compression and bending were considered infinit in EC3, the computation error in the initial rotation stiffness of the connections were to a little large more than the Finite element method.