Seismic Behavior Of The Double-channel Steel Constrained All-steel Buckling Restrained Brace

The double-channel steel buckling restrained brace is a new type of buckling restrained brace.The core force-bearing member is composed by a circular tube and two loading ends.The loading end is welded by a trapezoidal loading plate and four right-angled trapezoids.The outer constraining member are welded by two channel steels and connecting plates with multiple T-sections.The buckling restrained brace not only has the advantages of light weight,convenient assembly,etc.,but also can be used to form an buckling restrained brace by adding an outer restraining member to the existing single-tube brace.Firstly,this paper introduces several common stability theories of bracing structures,The relevant dimensions of The double-channel steel buckling restrained brace are calculated according to the steel structure specifications.Because ABAQUS software is needed to be used for calculation,the theory and method of non-linear finite element analysis are introduced.A single-tube bracing model and a five-parameter model of The double-channel steel buckling restrained brace are established and calculated,and The stress-strain parameters of each model are obtained.Before studying The double-channel steel buckling restrained brace members,we need to study a simpler tube brace,which is simple in structure and calculation.It is convenient to compare with The double-channel steel buckling restrained brace.The sizes of single tube bracing members are the same as those of core members in The double-channel steel buckling restrained brace members,and the boundary conditions,loading modes and model sizes of the model are the same as those of core members in The double-channel steel buckling restrained brace.The results show that under small loading amplitude,large deformation will occur under compression and the initial geometric state cannot be restored under tension.The ultimate failure sign is the appearance of three plastic hinges.When studying the influence of different gap on The double-channel steel buckling restrained brace,the brace components with gaps of 1mm,2mm and 3mm were set up respectively.It was found that the maximum stress point appears on theside of the core component with gap of 3mm under small amplitude loading,and the stress point position of core members of The double-channel steel buckling restrained brace members was the same as that of the small amplitude loading,which indicated that the outer restrained member had the same stress position on the core component at this time.The restraint effect of outer restrained member is limited.The radius-to-thickness ratio of The double-channel steel buckling restrained brace is studied to control the outer diameter of core pipe unchanged and adjust the radius-to-thickness ratio by changing the thickness of core pipe.Under the small loading amplitude of the above five groups of members,after the cyclic tension and compression,the core members can restore the geometric initial state,and the bearing capacity of the members increases step by step.When 1% SDR is loaded under tension,necking occurs in the middle and lower parts of the core members,and the tensile bearing capacity decreases in turn,and the members are buckled under compression.In the components with different gaps,the larger the gap,the earlier necking occurs.Among the components with different radius-to-thickness ratio,the smaller the radius-to-thickness ratio,the earlier the material buckling occurs in the buckling position.Thus,damage occurs earlier.The material of the core bearing member and the external restraint member yielded at the buckling point under compression,and the member was destroyed.The gap of The double-channel steel buckling restrained brace has little effect on the bearing capacity and stiffness of members,and the difference is less than 5%.In this paper,the energy dissipation performance is reflected by the additional effective damping ratio.Under small loading amplitude,the additional effective damping ratio of components with different gaps is the same.Under large loading amplitude,the additional effective damping ratio of large gap structure is larger and its energy dissipation performance is better.The radius-to-thickness ratio of The double-channel steel buckling restrained brace has greater influence on the bearing capacity and stiffness,which is mainly proportional to the cross section of the core members.Under large loading amplitude,the bearing capacity and stiffness of components with small radius-to-thickness ratio decrease more,and the maximum effective damping ratio is added,which leads to better energy dissipation performance.Finally,we compare the seismic performance,cost and weight of the double channel steel buckling restrained brace with that of the concrete filled buckling restrained brace.It is found that the former has relatively small bearing capacity and stiffness values,but the former has better symmetry between the tensile and compressive bearing capacity and stiffness values,and the former has only 2.03%higher cost and 53.47% less weight than the latter.