Experimental Research On Compression-Bending-Torsion Mechanical Behavior Of Square Concrete Filled CFRP-Steel Tube

Nowadays,concrete-filled steel tube(CFST)components are very popular in the construction industry.But at the same time because of the aging of the structure and the deterioration of the components can not be avoided,using new materials to implement strengthening technology and other actions to solve this problem is very important.Carbon fiber reinforced ploymer(CFRP)has good performance and excellent mechanical properties.In this case,concrete-filled CFRP-steel tube,as a new type of composite structure,emerged in the construction industry.In actual engineering,the stress of structural components is complex and diverse,and most of them are in the state of complex stress.For example,the corner columns in the frame structure and the wind power tower will not only bear the action of pressure load and bending moment,but also produce the action of torque under the action of horizontal load,such as wind load and earthquake action.In addition,the node form of the square section member is simple,convenient to connect the beam and column at the node,and convenient for construction.Therefore,this paper mainly studies the compression-bending-torsion static behavior of square concrete-filled CFRP-steel tube,the main contents include:(1)A total of 9 specimens were tested,and the test parameters contain axial compression ratio,bending moment ratio and number of longitudinal CFRP layers.The research results indicate that the torsional bearing capacity of the specimens is obviously improved with the increase of axial compression ratio.When the axial compression ratio is 0.2,the torsional strength of specimens can be improved by increasing the bending moment ratio.Increasing the number of longitudinal CFRP layers can slightly enhance the torsional bearing capacity of specimens.(2)The model of compression-bending-torsion static behavior square concrete filled CFRP-steel tube is established by using the finite element software ABAQUS,and the accuracy of the model is verified by the test results.(3)Based on this FE model,the influence law of axial compression ratio,bending moment ratio,concrete strength and steel strength on the bearing capacity of members was analyzed.The researchs show that axial compression ratio,concrete strength,steel strength and the number of transverse CFRP layers have significant effects on the torsional bearing capacity of the members compared with other parameters.Increasing the number of longitudinal CFRP layers can slightly enhance the torsion strength of members.When the axial compression ratio is small(n=0.2),the increase of bending moment ratio has no significant effect on the torsional bearing capacity of square concrete-filled CFRP-steel tube members.However,when the axial compression ratio is relatively large(n=0.4),the torsional bearing capacity of the member decreases with the increase of the bending moment ratio.