Research On Superposition Method Based On "Bearing Capacity Unit" For Axial Compression Bearing Capacity Of Cold-formed Steel Built-up Triple-limbs Half-open Short Columns

At present,the cold-formed thin-walled steel(CFS)structural system is widely used in the construction industry because of its many advantages,and it has gradually attracted many scholars at home and abroad to study it.However,the theory research on the calculation method of the composite column bearing capacity is still in its infancy,and the relevant domestic and foreign codes have not clearly given the calculation method for bearing capacity of split column,which cannot guide practical engineering problems scientifically and effectively.Therefore,this research group creatively proposed a general design method for bearing capacity based on the consideration of the stability of the screw split panel,the correlation of the split section panel group,and the overall mechanical performance of the component— "the superposition method based on the bearing capacity unit".In this paper,the CFS built-up triple-limbs half-open shot columns is the research objectives,and the part of the local buckling bearing capacity of the short column in the superposition method based on the bearing capacity unit is studied in detail.In this paper,the axial compression performance of the three bearing capacity units corresponding to the split column is studied,and on this basis,the calculation method of the local buckling bearing capacity of the split column is proposed.The main contents of this paper are as follows:(1)The local buckling axial compression performance of the CFS three-limb half-opening split column and its corresponding three load-bearing units,a total of 72 specimens,was tested.In the introduction to the test part,the mechanical performance,failure mode and deformation characteristics of the load-bearing unit specimen and the split column specimen are studied.(2)The ABAQUS finite element analysis software is used to establish an accurate model of the test specimen,and the simulation situation is compared with the actual test to verify the accuracy of the finite element analysis.On this basis,the variable parameter analysis of the variable height-thickness ratio and the screw spacing was carried out,and the influence of these two parameters on the local buckling ultimate bearing capacity of the load-bearing unit specimen was revealed.(3)On the basis of experimental research and finite element analysis,the calculation method model in this paper is proposed,and the ultimate bearing capacity calculation formula of each bearing capacity unit and built-up column is obtained by nonlinear regression of the data obtained from the variable parameter analysis.The data is verified,and finally the calculation formula of the local buckling ultimate bearing capacity in the bearing capacity element superposition method is obtained.Then,the calculation results according to the Chinese and American standards and the method in this paper are compared with the test results to verify the superiority and accuracy of the load-bearing element superposition method.