| Composite space truss (CST) is a kind of space structure composed of steel tubes and reinforced concrete ribbed slabs. It is a very practical structure which can not only make good use of the material character that the concrete is in compression and the steel is in tension, also can make the structure's load-bearing and surrounding functions come into integrity. The CST has great stiffness, light weight, applicability of resisting crack and earthquake effects. So that the CST is more adaptable to the structure which has larger span. It is a kind of structural style with promising development future. The research of the structure is mainly in elasticity at home. The yield mechanism and the failure mode of the CST are not well understood, and calculating theory and design method are not well developed. Therefore, it is significant for theory and practice to study ultimate load-carrying capacity of this type of space structure.The mechanics capability and yield mode of the CST based on a Monotonously Static Loading test have been researched deeply in this paper; By comparing the finite element method and experimental results, it is proved that the finite element theory and the method is reliable. The research of this article mainly manifests in the following aspects:Firstly, the paper introduces the research and application actuality of CST.Secondly, this article has conducted the experimental research on the overall model of CST. By the experiment, we have had comprehensive understanding about the deformation and force-bearing of rods, concrete plate and the entire structure. The load-bearing property of the whole structure in elasticity, yield and failure stages is gotten. The results of the test are analyzed, and the yield mechanism and the failure mode of the CST are discovered. It further verifies the features of CST being of great rigidity and high weight-bearing force. CST has large ultimate load-carrying capacity and it is about 1.5 times than its design one. The ultimate failure mode of the experimental model is overall bending failure. The specific process is the buckling of the bottom chords, redistribution of internal force and the large deflection. Analysis by test data reliability has proved that the data obtained in this experiment is reliable. Steel truss and reinforced concrete slab work well with each other. The structure has good ductility.Next, this article makes the systematical nonlinear finite elements analysis about CST. Finite element model involving geometric large deformation and materials nonlinear are presented, which has been carried out to simulate the ultimate behaviour of the simply supported CST experimental model with the aide of program of ANSYS.At last, by the comparison between the analysis results and the data of the test, it has proven their uniformity. It reveals that the supposition and parameter of the finite element analysis model can reflect the true situation of the structure. It is proved that the numerical model is quite reasonable. While it provides an accurate finite element model for analysis of parameters about CST.By making the analysis of CST elastic and plastic buckling strength, it was hoped that this paper can put forward some reference suggestions for the study of CST.
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