Experimental And Theoretical Study On Semi-rigid Beam-to-column Composite Joints With Flush End-plate Connection

Bolted end-plate connection is one of the main connection for the steel structures, which is with high resistance ability, large stiffness, and convenient for construction. The beam-to-column joints are assumed to be rigid or pinned in the traditional method for designing and analysis. But in fact, most of the connections are semi-rigid, whose characters are between the pinned and rigid, because it is very difficult to realize full pinned and rigid. In the composite frames, a new type connection called semi-rigid composite connection, composed of.bare steel joint and composite slab is achieved.This dissertation, supported by the Natural Science Foundation of China for Outstanding Young Scholars (No.50225825) and Open Project of National Key Lab of Civil Engineering Hazard Resistant, is concerned with the characters of the composite beam-to-column joints with flush end-plate connection, including as follows:(1) Founded on the lots of the references, the experimental and theoretical research in the recent decades is summarized, including classification of connections, mathematic models of moment-rotation curves of connections, etc.(2) The cyclic loading tests on the beam-to-column composite joints with flush end-plate connection are carried out. One bare steel joint and two cruciform composite joint specimens were tested under low cyclic loading at the top of columns so that one side of the beam-to-column connections was under negative moment and the other side under positive moment. The moment-rotation relationships for the connections were obtained experimentally. Detailed test observations and results were reported.(3) Two composite joint specimens with same type of connection were tested under pseudo dynamic loading. The Ispara earthquake record with different peak values is used to load the specimens. The acceleration response, displacement response, hysteretic characters, stiffness and energy dissipation capacity are analyzed. Detailed test observations and results were reported.(4) Based on the experimental results and current available research, a method has been developed for predicting the moment capacities of flush end-plate composite connections by plastic analysis method. In this method, the effects of both negative moment and positive moment are taken into account, as well as the effects of non-symmetrical moments, shear acting on the connections, prying forces of high-strength bolt, etc. If the reinforcement ratio is set as zero without considering the effect of the composite slab, then the moment capacity of bare steel connections can also be predicted by using this method.(5) The stiffness of column web in compression, tension and shear, reinforcement in tension, column flange and end-plate in moment, bolts in tension, concrete slab in compression, are given. A method has been developed for predicting the initial rotational stiffness of flush end-plate composite connections in both negative and positive moment by the component method.