Experimental And Theoretical Study Of The External Steel - Concrete Composite Truss Performance

Steel-concrete composite truss structure is a new structure applied in recent years. Its joint is the most important component and it is also the stress and load transfer centre of the truss. The performance of the joint direct determines the practicability and reliability of the whole truss structure. The joint structure in this thesis belongs to the circumscribed steel-concrete composite truss joint, which links the reinforced concrete chord member with steel web members by the gusset. This joint enables the truss structure to work through supporting the horizontal shear and transferring the trust of the chord member to the web member. The major content and findings of this thesis are listed as follows:(1) Two groups of experiments have been carried on to test the monotonous mechanical behavior of the circumscribed steel-concrete composite truss joint model with 1/3 scale. With the strain gauge and displacement measurement equipment on the sample, the experiments have yielded the stress strain of each parts and the load-displacement curve of the sample. Besides, the deformation situation, fracture strike and destruction forms of the joint have been obtained from the observation during these experiments. With these acquired data, a simple mechanical analysis of the samples is finished. It was concluded that the samples show an obvious sign before damage and have good ductility with the maximum bearing capacity of 260 T to 300T.(2) Based on the experiments above, the thesis also has made a nonlinear analysis with the FEA program ABAQUS. Through the finite element analysis of the steel-concrete composite truss joint, the load-displacement curve, deformation pattern and stress map can be acquired. By comparing the analysis conclusion with the experiments results, it turns out that they are accordant with each other.(3) In order to research each parameter's effect on the joint, a paramedic analysis with the FEA program has been carried out on the basis of the previous studies. This analysis tries to test the effect of four parameters which are the concrete intensity, the diameter of the PBL connecting key, the gusset plate thickness and the steel strength. According to the analysis, it is found that the steel strength has a great influence on the sample's maximum bearing capacity while the other three have little impact. As for other performance indicators of the joint components, for instance the maximum stress of the gusset, maximum stress of the steel support and other, they vary monotonically with the change of the parameters.