Research On Axial Compressive Performance Of High Strength Thin-walled Concrete-filled Double-skin Steel Tubular Short Columns With Longitudinal Stiffeners

Since the 1860 s,many scholars have carried out a relatively comprehensive study on traditional single concrete-filled steel tube column,but the research results on composite thin-walled concrete-filled steel tube members are relatively rare,and the research on multi-cavity and different stiffening rib forms is relatively rare.There are relatively few comparative studies,especially the research results on the concrete-filled double skin steel tube column made of high-strength steel Q690.Based on Q690 highstrength steel,this paper designs a series of composite thin-walled ribbed high-strength concrete-filled steel tubular specimens with different hollow ratios,different stiffening rib forms,different stiffening rib lengths,different concrete strengths,and different steel yield strengths as variables.And analyze the influence of these parameters on its axial compression performance.The main research contents and main conclusions of this paper are as follows:(1)Taking the hollow ratio,outer steel tube stiffener form and concrete strength as parameters,12 composite concrete-filled thin-walled ribbed high-strength steel tube short columns were made of 3mm thick Q690 steel plate for axial compression test,and it’s outer steel tube width-to-thickness ratio is 100,to study its mechanical properties such as failure mode,load-deformation curve,ductility and ultimate bearing capacity.The test results show that the structural measures of increasing the strength of the sandwich concrete and adding stiffeners on the outer steel pipe can effectively improve the ultimate bearing capacity of the specimen,but the difference between the two different forms of stiffeners is small,and with the increase of the hollow rate of the piece,its ultimate bearing capacity decreases.(2)The relevant mechanical properties of steel and concrete were determined by material property tests,and the finite element model of the composite concrete-filled thin-walled ribbed high-strength steel tube short columns was established with the help of the finite element calculation software ABAQUS2020,and its results were compared with the test results.The results show that due to the mismatch between the strength of the steel pipe and the concrete,the simulated value of the ultimate bearing capacity of the specimen with a large hollow ratio(χ=0.68)is quite different from the experimental value,while the series of specimens with a relatively small hollow ratio(χ=0.34),χ=0.51),the simulated value of the ultimate bearing capacity is in good agreement with the experimental value.(3)According to the conclusions drawn from the finite element simulation and verification analysis,the effects of hollow ratio,inner steel pipe yield strength,outer steel pipe yield strength,inner steel pipe stiffener length,outer steel pipe stiffener length and concrete strength on the composite thin-walled rib were further analyzed.Effects of high-strength concrete-filled steel tubular short columns on axial pressure properties.The results show that no matter the stiffeners of the same length are set on the inner steel pipe or the outer steel pipe,the influence on the overall ultimate bearing capacity of the specimen is basically the same;the influence of the yield strength of the outer steel pipe on the overall ultimate bearing capacity of the specimen is more obvious;the improvement of concrete strength can significantly improve the ultimate bearing capacity of the specimen.