Hysteretic Behavior And Parametric Analysis Of Beam-Column Connection With Replaceable T-Stub With Expanded Flanges Of Steel Frame

According to the investigation report of American Northridge earthquake in 1994 and Japanese Kobe earthquake in 1995,many traditional steel frame beam-column connections have occurred brittle failure,which was contrary to the design concept of "strong column-weak beam and strong connection-weak member",and did not show the expected ductility and energy dissipation capacity.The most effective way to solve the brittle crack of the beam-column joint is to move the plastic hinge out.Generally,there are two ways:one is to weaken the beam section,the other is to strengthen the beam section.In this paper,the T-stub connection is taken as the research object,combined with the previous research results of the widened beam flange connection at beam-end of steel frame,the T-stub connection is improved to the expanded flange T-stub connection,on this basis,the hysteretic behavior of the expanded flange T-stub of steel frame beam-column connection is analyzed,and the optimization of T-stub connection is carried out based on the moment-rotation model of T-stub connection.The main research contents and achievements are as follows:(1)Experimental study and finite element analysis of T-stub connection:monotonic tensile experiment is carried out on four T-stub connections and corresponding nonlinear finite element models are established.By comparing the experiment results of load-displacement curves of T-stub connections with the finite element analysis results,the contact pair algorithm is more suitable for the finite element analysis in this paper,and then further analysis is carried out through the failure modes of T-stub connections and analysis of bolt tension to verify the validity of finite element analysis,which lays the foundation for the nonlinear analysis in the following research.(2)Hysteretic behavior analysis:the nonlinear finite element analysis models of the steel frame beam-column connection of the ordinary type and the expanded flange T-stub connection are established.The load-displacement curve,the skeleton curve,the bearing capacity,the ductility coefficient,the stiffness degradation rule,the energy dissipation capacity and the mechanical performance of the panel zone of the two kinds of joints are studied.The results show that the seismic performance indexes of expanded flange T-stub connection joint are significantly better than that of the ordinary connection,in which the ultimate displacement is increased by 33.1%,the ultimate load is increased by 11.1%,the ductility coefficient is increased by 29.4%,and the energy dissipation capacity is increased by 10.6%,which shows that the expanded flange T-stub connection has better seismic performance.(3)Parameter optimization analysis:based on the above nonlinear finite element analysis models of the expanded flange T-stub connection joints,the parameters such as the flange plate thickness of T-stub,the web plate thickness of T-stub,the length la of the strengthen of the expanded flange,the length lb of the transition section of the expanded flange and the width c of the strengthen of the expanded flange are considered,and the finite element analysis models with variable parameters are established.The mechanical performance indexes of bearing capacity,ductility coefficient and equivalent viscous damping coefficient are analyzed,and the reasonable range of the five parameters is given.Based on the initial stiffness and ultimate moment values of all finite element models,the moment-rotation curve formula of the three parameter power function model of the expanded flange T-stub connection is given.