Study On Seismic Behavior Of Cold-formed Thin-walled Steel Composite Walls With Bracket

Cold-formed thin-walled steel architecture are developing rapidly at home and abroad because of their higher strength/weight ratio,energy conservation and environmental protection.Domestic and foreign scholars improve the mechanical performance of the structure through modify structural form and transmission mechanism to enhance the vertical and horizontal capacity and promote the wider engineering application of cold-formed steel structure.As the main horizontal lateral resisting unit of the cold-formed thin-walled steel buildings,its brace in the skeleton can effectively improve lateral performance and the damage of the wall with brace often occurs at the joint of the brace and the skeleton.Therefore,this paper proposes a kind of cold-formed thin-walled steel composite walls with bracket which adding bracket at the joint of the brace and skeleton to improve the shear capacity,so as to improve the seismic performance of cold-formed thin-walled steel structure.Because the ? section has better axial compression performance than the common C section,so the ? section of wall is used in column and brace to obtain better bearing performance of wall in this paper.In order to study the seismic performance of the cold-formed thin-walled steel composite walls with bracket,four composite wall specimens sheathed gypsum board or OSB board were tested under cyclic loading with vertical loading or not.The indexes of the composite wall,such as stiffness,shear capacity,ductility coefficient and energy consumption coefficient,were compared and analyzed.ABAQUS and SAP finite element software were used to simulate the test specimens,the results are in good agreement with the test results,which proves the accuracy and feasibility of the finite element analysis method.The influence of panel side number,angle brace length,height width ratio and vertical load on the seismic performance of composite walls were analyzed based on the method.Combined with the results of test and finite element calculation,the method of "equal safety degree" is used to compare the code of our country with the code of the United States,and the equivalent resistance partial coefficient used to calculate the design value of shear bearing capacity is calculated,and the design value of shear strength of corner braced reinforced composite wall under seismic condition is obtained.The test results show that:The common failure mode for the gypsum specimen was the separation of self-drilling screws and gypsum boards,as a result of local fragmentation in gypsum boards around the self-drilling screw hole.For the OSB specimen,self-drilling screws bent under the effect of the OSB boards,which followed by nut embedding in OSB boards,eventually self-drilling screws pull-out from steel frame with OSB boards.Due to the differences in the properties of the panels,the shear capacity of the gypsum board specimen WDG-1 is about 31.8%of the OSB board specimen WDO-1,and the stiffness K300 is about 30.6%.The shear capacity and stiffness of WDG-2 are 41.9%and 43.2%of the test specimen WDO-2.The vertical loading improved shear performance of cycle loading specimens,especially for the energy dissipation performance of double-sided gypsum board specimens,the range is about 166.7%.The finite element results show that:Under cycle loading,the shear capacity of cold-formed thin-walled steel double-sided boards composite walls with bracket was about twice that of the single-sided board composite walls minus the shear capacity of cold-formed thin-walled steel frames.For the composite wall with the projection length of 100 mm,150 mm and 200 mm,the wall with the projection length of 100 mm shows better seismic performance than the other two.The vertical load of 40kN,80 kN,120 kN and 160kN is applied to the cold-formed thin-walled steel composite walls with bracket sheathed gypsum board and OSB board.It is found that the seismic performance of the wall is better when the vertical load of 120kN is applied to the two kinds of panel walls.The height of corner braced reinforced composite wall increases from 2.4m to 2.7m and 3.0m,the shear bearing capacity,stiffness and energy dissipation capacity of the wall decrease,but for ductility,the higher the height of gypsum board without vertical load and OSB board with or without vertical load,the better the ductility,while for gypsum board wall with vertical load,the higher the height,the worse the ductility coefficient.In this paper,a kind of support form with better seismic performance is proposed.The shear capacity of the wall steel frame with this support form is effectively improved,it can be applied to practical projects.The partial coefficient of equivalent resistance of cold-formed thin-walled steel composite walls with bracket under earthquake is 1.5 when the wall is steel frame and single-sided board wall,and 1.45 when the wall is double-sided boards wall.The conclusion can also provide reference for the revision of the code.