| Under the action of the earthquake,the eccentrically braced steel frame dissipates energy mainly through plastic deformation of the shear links.The link beam will inevitably undergo strain hardening during the plastic deformation process,so the internal force caused by strain hardening must be considered in the design of non-energy-dissipating components,which leads to larger design sections and higher construction costs.As a result,a design method of separating the link from the frame beam has emerged to form an independent energy dissipation link.By reducing the cross-sectional size,the link yields first and dissipates energy.However,this design method may cause the link to yield under the action of small earthquakes or even static loads,which affects the normal force transmission of the structure.Therefore,a design method of a replaceable shear link with web openings is presented based on the advantages of the separated link,which makes the structure easy to be repaired after the earthquake.That is,making a hole in the web that mainly bears the shear force to ensure that the flexural capacity of the energy dissipation shear link is basically unchanged,the shear strength of the energy dissipation shear link is weakened separately to enable the shear yielding occurs first under the earthquake action,dissipates the seismic energy and protects the frame safety.At the same time,this weakening method also further improves the rotation capacity and energy dissipation capacity of the link.To study the mechanical and seismic performance of web opening type replaceable shear links,six web opening type replaceable shear links were tested under the cyclic load,and 31 web opening type replaceable shear links with different parameters were analyzed by finite element numerical simulation under monotonic load and cyclic load.The mechanical properties and seismic performance of the web opening type replaceable shear links were obtained.(1)Six specimens with different web openings were tested subjected to the cyclic loading.The stress distribution,failure phenomenon,failure mode,hysteretic curve,energy dissipation coefficient,skeleton curve,and stiffness degradation curve were obtained.The mechanical properties and seismic performance of the web opening type replaceable shear links were analyzed.It was found that the web opening type replaceable shear links with stiffeners have better energy dissipation capacity and rotation capacity.(2)Based on the comparative analysis of the parameters of six specimens in the experimental study,the influence rules of the hole length,stiffener arrangement,and web thickness on the seismic performance of the web opening type replaceable shear links are obtained.It was found that these parameters have a great influence on the seismic performance of the replaceable web opening type replaceable shear links.(3)The finite element numerical simulation analysis of web opening type replaceable shear links with different parameters under monotonic loading was completed,and the loaddisplacement curve,bearing capacity,ductility coefficient,initial stiffness,and stress distribution of each shear link was obtained.The mechanical properties of the web opening type replaceable shear links under monotonic loading were discussed,and the influence of the opening type,opening length,web thickness,link length,section height,stiffener arrangement,and other parameters on the mechanical properties of the web opening type replaceable shear links were analyzed.It is found that the appropriate opening length can make the shear links lose less bearing capacity and obtain higher ductility.(4)The numerical simulation analysis of 31 web opening type replaceable shear links with different parameters under cyclic loading is completed.The stress distribution,plastic development,hysteresis curve,energy dissipation coefficient,skeleton curve,and stiffness degradation curve of each specimen were obtained.The seismic performance of the web opening type replaceable shear links under cyclic loading is discussed.The influence of the opening form,the length of the opening,the thickness of the web,the length of the shear links,the section height,and the layout of the stiffener on the seismic performance is analyzed.Three kinds of stress mechanisms of the web opening type replaceable shear links are summarized:When the web has a round hole,the web at the edge of the hole forms an obvious "arch" effect,the stiffness of the shear link increases,the bearing capacity increases,the plastic deformation capacity decreases,and the energy dissipation performance are relatively weakened;The length of web opening increases gradually,the web in the upper and lower regions of the long side of the opening is the first to yield,which causes stress redistribution,and finally the shear yield of the whole web,which fully displays the energy dissipation performance of the web;When the web opening is too long,the upper and lower parts of the section can not work together.Similar to the directional support formed by two parallel "chain rods",the shear stiffness of the end of the shear link is greatly reduced,and the bearing capacity and plastic deformation decrease.(5)By comparing the finite element results with the experimental results,the correctness of the finite element simulation is verified.Combined with finite element simulation and experimental research,it is proved that the web opening type replaceable shear links can make the structure have normal force transmission and better energy dissipation capacity. |
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