Refined Analysis On Structural Behavior And Experimental Study Of Axial Compressed Sleeved Member

The instability of compressive steel members is one of the most important issues that should be considered in the process of analysis and design of steel structures. As one form for stability improving of compressive steel members, the sleeved member is taken seriously more and more because of the advantage of its clear theory, simple details, obvious effects. The sleeved member is composed of an inner tube and an outer tube, and with gap between them. The inner tube bears the axial compression, while the outer component restrains the inner tube from buckling and improves its post-buckling behavior, thus enhancing its load-carrying capacity. Currently, there are still some problems to be solved in the project application and theory analysis. On one hand, the previous form of sleeved members is difficult to be used in the compressive members existing structure. On the other hand, the performance of the inner tube needs further analysis after the inner tube being plastic with the axial compressive load increasing. And the research of energy dissipation capacity and dynamic response of the sleeved member should be still studied.To solve these problems, this paper intended to improve the details of the sleeved member by using two semi-circular and constant-section steel tubes instead of a seamless circular tube, and setting ear-plate connections at the ends and middle of the steel tubes, each pair of ear-plates is linked with bolts. This form of sleeved members is convenient for stability reinforcement of compressive members in a structure, and solves the installation problem of the outer tubes. Then, this paper made deeply research on load-carrying capacity of sleeved members. Considering the perfect elasto-plasticity material model, structural behavior of the sleeved member was analyzed by theoretic deduction, which could be divided into three states:the elastic inner tube contacts the outer sleeved tube, only the inner tube becomes plastic and both the inner and outer sleeved tubes become plastic. Curves between axial compressive loads and lateral displacements of the middle sections and axial displacements of the inner tubes were obtained respectively. Then four sleeved members were analyzed through FEM, and the numerical results were consistent with the theoretic formulas. Finally, experiments of full-scale sleeved members were performed. The theoretical and experimental results are shown that when the inner tube contacts the sleeved tube, there will be inflection points in curves between axial compressive loads and lateral displacements, and the trends of curves are consistent. The sleeved tube improves load-carrying capacity of the inner tube. And then the table of compressive carrying capacity of the commonly cross-section sleeved member are displayed upon the theoretic analysis.This paper utilized the sleeved members instead of the compressive members with the great pressure in truss and space grid structure. The result shows that the sleeved members can effectively ameliorate the local stress situation, and improve the ultimate load-carrying capacity of the whole structure. Then, the paper calculated the energy dissipation capacity of the sleeved member and the inner tube, under the cyclic reciprocating load through FEM simulation. The calculated results are compared and show that energy dissipation of the sleeved member is obviously superior to that of the inner tube. Futhermore, this paper simulated two single spherical reticulated shell structures, which are respectively with the sleeved member and without, and analysed the action of dynamic response under the earthquake by the finite element program. The results demonstrate that the sleeved members can appropriately improve the dynamic properties of the shell structure. This paper provides theoretical basis for application of the sleeved members in reinforcement engineering.