Study On Catenary Effect And Resistance To Continuous Collapse Of Steel Frame With Direct Circular Arc Extension Joint

In recent years,the number of progressive collapse accidents of buildings due to accidents is increasing gradually.The research on structural progressive collapse resistance has attracted extensive attention of many scholars at home and abroad.The direct circular arc-extended wing joint can improve the structural resistance to progressive collapse by exerting its catenary effect,which has a strong engineering application value.In this study,the catenary effect of the extended wing joint and the progressive collapse resistance of the steel frame structure based on the extended-wing joint are studied through the numerical simulation method from the joint and the frame with the extended-wing joint.In this paper,the finite element models of the steel frame joint substructure and the overall steel frame structure are established.The finite element software is used to simulate the low-cycle reciprocating load of the node sub-structure and the Pushdown nonlinear static analysis and linear static analysis of the steel frame based on the demolition member method.The calculation formula of catenary effect of steel beam is modified based on joint ductility.The main findings are as follows:(1)Using finite element software,six direct arc-expanded nodal models with different lengths and widths and one common nodal model are established.The finite element simulation under low-cycle reciprocating load is carried out.The correctness of the element model is verified by the test results.Both the finite element results and the test results show that the extended-wing joint can effectively move the plastic hinge outward.From the aspects of hysteretic performance,skeleton curve,ultimate bearing capacity and ductility,it is quantitatively proved that the extended-wing joint has better ductility performance and energy dissipation capacity than the ordinary joint.(2)Base on the previous studies,it is found that the ductility of nodes plays a very important role in the formation and delivery of catenary effect.According to the analysis and research of this paper,the calculation formula of catenary effect of steel beam is modified based on the ductility of joints,which makes the modified formula more accurate.In addition,the calculation error is smaller and the calculation accuracy is improved by comparing with the calculation results of the modified formula with the test results of the steel frame made by predecessors,which verifies the accuracy and effectiveness of the formula.The formula shows that the catenary effect of the joint depends on the ductility of the joint to a great extent,and the catenary capacity provided by the extended-wing joint is higher than that of the ordinary joint.(3)By using the finite element software,the steel frame models based on direct extended-wing joints and ordinary joints are built respectively,and the failure conditions of corner column,long side middle column,short side middle column and internal middle column were selected respectively to conduct linear static and nonlinear static analysis.The simulation results show that the direct arc-expanded nodal frame can play the catenary effect better than the ordinary nodal frame and has a good resistance to continuous collapse.Based on the modified formula,the catenary effect on the structure of continuous collapse resistance coefficient ? is proposed.Through the quantitative evaluation of ? value,it is found that the catenary effect to the coefficient of improvement against collapse of the expanded-wing joint is higher than that of the ordinary joint.