| The K-type eccentrically braced steel frame combines the characteristics of high ductility of pure frames and high stiffness of centrally braced steel frames,and is highly favored in the construction industry.Its good performance depends on whether the energy dissipation connection can withstand non elastic rotation under strong earthquake action.However,the traditional seismic design method mainly involves designing the frame beams and energy dissipation connections of K-shaped eccentrically supported steel frames as a whole,yielding and dissipating energy by specifying the inelastic deformation of the components,while the design of other structural components should maintain basic elasticity and resist the loads generated by complete bending and strain hardening of the energy dissipation connection,which often leads to excessive design of the dimensions of other components beyond the connection,Therefore,it increases the construction cost and the difficulty of post earthquake repairs.The design concept of separating the replaceable energy dissipation connection from the frame beam compensates for the above shortcomings.It can be designed as a back to back double C-groove composite section,connected to the frame beam through web bolts,similar to a replaceable fuse,for easy replacement and repair after earthquakes.Usually,the section height of this type of energy dissipation connection is smaller than that of frame beams,aiming to concentrate the non elastic deformation of the structure on replaceable energy dissipation connections by weakening the section.However,the weakening of the section does not solve the problem of excessive strength caused by strain hardening of the connecting beam.However,energy dissipation connections with shear yield often experience severe shear strain under seismic loads due to their high plastic rotation ability,This leads to excessive cyclic hardening.This article proposes using aluminum alloy material as an energy dissipation connection.Compared to steel,aluminum alloy has a lower yield point and better ductility.Moreover,replacing the K-shaped eccentrically supported steel frame with aluminum alloy energy dissipation connection can effectively solve the problem of strain hardening in traditional steel energy dissipation connections.At the same time,this article adopts a web plate connection method to ensure that the aluminum alloy energy dissipation connection is easy to yield and better achieve the protective effect of energy dissipation connection on the overall frame.Using ABAQUS finite element software,55 models of K-shaped eccentrically braced steel frames with replaceable aluminum alloy energy dissipation connections were established.The effects of six parameters,including web height to thickness ratio,flange width to thickness ratio,material,length,stiffener spacing,and cross-sectional area,on mechanical properties and hysteresis behavior were analyzed and summarized.Then conduct 1/3 scale experimental research on some models,combining experimental phenomena and results with numerical simulation results to verify each other.The main research content is as follows:(1)Establish a finite element model of 55 K-shaped eccentrically braced steel frames with replaceable aluminum alloy energy dissipation connections with different parameters.Firstly,simulate and analyze them under unidirectional loading.Based on the obtained load displacement curves,analyze the influence of steel frame structures under different parameters.Then,it is subjected to cyclic loading,and based on the obtained hysteresis curve,stiffness degradation curve,and skeleton curve,the influence of changes in six parameters of aluminum alloy energy dissipation connection,including web height to thickness ratio,flange width to thickness ratio,material,length,stiffener spacing,and cross-sectional area,on the plastic angle of energy dissipation connection,steel frame stiffness,and bearing capacity,is analyzed,and the influencing rules are summarized.(2)Two experiments were completed on six 1/3 scale K-shaped eccentrically braced steel frames with replaceable aluminum alloy energy dissipation connections under low cycle reciprocating loading.Analysis of the energy dissipation coefficient and plastic rotation angle of the structure revealed that the structure had good energy dissipation and plastic rotation capabilities.During the entire loading process,the plastic deformation is mainly concentrated in the aluminum alloy energy dissipation connection,which is replaced when the interlayer displacement angle is 1/50.The frame beam does not have out of plane deformation or up and down misalignment,making the replacement process convenient and smooth.The aluminum alloy energy dissipation connection is lightweight,and can be replaced by a single person after the high-strength bolts are unscrewed.(3)The numerical simulation law is consistent with the experimental law,and the sensitivity to the length of the energy dissipation connection,the height to thickness ratio of the web,and the cross-sectional area is the same.The bearing capacity error between the two is within 20%.It is feasible to use numerical simulation to analyze the performance of the structure. |
