| In recent years,cold-formed thin-walled steel buildings have developed in China,many boards are often used as the cladding of this kind of buildings,such as oriented strand board(OSB),plasterboard,bamboo plywood,lightweight concrete board,etc..At the same time.paper strawboard-a new type of ecological board-has entered the domestic market.Paper strawboard has the advantages of heat insulation,flame retardant,sound insulation and noise reduction.Its production process is environmentally friendly,and the recycling cycle of its raw materials is short.Therefore,using paper strawboard as the cladding of the walls in cold-formed thin-walled steel buildings can improve the insulation performance of the walls and make full use of abandoned agricultural resources.In this paper,the seismic performance of cold-formed thin-walled C-channel steel-paper strawboard composite walls are studied by experiment and finite element analysis method,which can provides reference for the engineering application of this composite wall.Four full-scale cold-formed thin-walled C-channel steel-paper strawboard composite walls and one non-clad steel frame were tested under low-cycle reciprocating loading to study the effects of different vertical loads,paper strawboard cladding and diagonal bracing on the seismic bearing capacity.The seismic performance indexes such as bearing capacity characteristic value,stiffness,ductility coefficient and energy dissipation coefficient of each specimens were obtained from the analysis.The test results show that covering the strawboards on both sides can increase the bearing capacity of the steel frame by 7-8 times.Diagonal bracing can not improve the bearing capacity of walls significantly.The bearing capacity of wall decreases linearly with the increase of vertical load.The seismic bearing capacity of such walls are 13.81kN/m?19.75 kN/m.The ductility and the energy dissipation capacity are well.The lateral stiffness of the composite wall is slightly insufficient,and the main failure modes are connection failure between paper strawboard and steel or local buckling at the bottom of the end columns.These issues can be improved.Finite element analysis is carried out by using finite element software ANSYS.The material nonlinearity and geometric nonlinearity are fully considered in the modeling process.And the coupling operation and spring units are used to simulate the function of the self-tapping screws.According to the actual stress conditions of the specimens in the test,reasonable boundary conditions are applied to the model.The results of the finite element analysis are basically consistent with the experimental results,it indicates that the finite element analysis method is feasible.On this basis,the influences of section size,steel strength,column spacing,peripheral self-tapping screw spacing and height-width ratio on walls bearing capacity are studied by finite element parameter analysis.The analysis results show that appropriate reduction of column spacing and peripheral self-tapping screw spacing are economical and effective methods to improve wall bearing capacity.But the column spacing should not be less than 400 mm,and the peripheral self-tapping screw spacing should not be less than 100 mm.On the basis of the above research,the equilibrium equation is established according to the failure mode of composite walls and the formulas for seismic bearing capacity of cold-formed thin-walled C-channel steel-paper strawboard composite walls with different height-width ratio and vertical loads are derived.And approximate partial coefficient of bearing capacity for seismic design of this kind of composite wall is obtained by using similar literature for reference.Compared with other cladding walls,it is verified that this kind of composite walls can be used as load-bearing walls.And some design suggestions are putting forward according to the problems encountered in the experiment and the conclusions drawn from the research. |
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