Nonlinear Analysis Of Semi-Rigid Connection Of Steel Structure

Connection in steel structures is divides into rigid connection, semi-rigid connection, ideal pin connection. The traditional analysis and design of steel frame assume beam-column connections are fully rigid or ideal pin connection. In fact , all connections of the steel structures, in practice, are between to fully rigid and pin connections and belong to semi-rigid connection.From the Northridge earthquake in 1994 and the Kobe earthquake in 1995,it is found out that the rigid connections of beam-column have poor ductility and result brittle fractures easily. But the semi-rigid connections such as angle connections, extended end-plate bolted connections have an excellent energy dissipating mechanism to resist earthquake loads,and provide more capacity for yielding and ductility ..In the meantime, the semi-rigid connections can save steel capacity, and become a kind of not only enconomical.but also reliability connection.This paper, by means of full-size connection experimental study and finite element analysis, investigates the behavior of two-type connections under static loads. All parts of the connections include bolts and angle steels are analyzed and some design recommendations are proposed. The main scopes of this paper includes:I .iixperiments analysis: Five specimens with two types of connections, i.e. two kinds of angle connections and three kinds of extended end-plate bolted connections are tested. For every kind of connection, the relations between stress and strain and the P-A relations under static loads are analyzed and compared.2.Finite element analysis: Finite element models are established based on the profiles of the tested specimens and similar specimens. Elastic and elasto-plastic analyses are conducted with the general-purpose finite element package ANSYS. Also the analysis results are compared with the experimental data.The main conclusions are as follows:I. Based on the comparing of experiments and tested results, five failure models ofvthe connections are studied, and the properties of parts sustained load, the regulars P-A curves and elastic rigidity in different connections are analyzed.2.The studies of this paper reveal that: Extended end-plate bolted connection has not only larger rigidity but also has higher strength and better ductility, It is a perfect type of semi-rigid connection.3.Bolts of the semi-rigid beam-column connections are very important part . The sustained load of the end-plate connections is related to many factors, such as : the pretension loads, the bolt locations, the bolt diameters, the bolt materials, and so on. The sustained loads of the exterior bolts are changed nonlinear under pretension loads and external loads.The deep studies about the behavior of high-strength bolts have provided information to design connections of semi-rigid steel structure.The results described above have provided significant information to develop the theory of steel beam-column semi-rigid connections and their design.