Research On The Behavior Of Spatial Steel Truss Confined Concrete Under Axial Compression

The spatial steel truss confined concrete composite column refers to a steel-concrete composite column formed by embedding the spatial steel truss into the concrete instead of the steel frame.The spatial truss is welded by angle steel and steel plates.During the loading process of this type of composite column,the angle steel mainly bears the vertical force,and also acts as a constraint on the internal concrete;the steel plates mainly produces tension on the angle steel,thereby improving the restraining effect of the angle steel,which has a similar effect to the stirrup;Due to the restraining effect of the spatial steel truss,the internal concrete is in a three-way compression state.The restraining effect of the spatial steel truss can not only improve the strength of the concrete,but also limit the cracking of the concrete,and ultimately lead to the composite column have a higher ultimate bearing capacity and better ductility.In this paper,the axial compression experiment of six spatial steel truss confined concrete composite column specimens was carried out firstly,the failure process of the specimens was described,and the mechanical performance of the confined concrete was analyzed.Afterwards,the constraint mechanism of the space steel truss to the core concrete is analyzed in depth on the basis of the axial compression experiment,and the effective lateral constraint stress calculation model of the spatial steel truss to the core concrete is proposed.Subsequently,the statistical regression analysis of this paper and relevant domestic experiment results,the formulas for calculating the peak stress and peak strain of the space steel truss-constrained concrete and the axial compression stress-strain relationship curve are established.Then,based on the stress-strain relationship model proposed above,the finite element software ABAQUS was used to establish the spatial steel truss confined concrete specimen model,and the stress mechanism of the whole process of the spatial steel truss confined concrete under axial load was described.Finally,the influence of parameters such as angle steel size,width of the steel plate,thickness of the steel plate,the spacing and arrangement of steel plate,and strength of the concrete on the axial compression mechanical performance and restraining effect of the spatial steel truss confined concrete are discussed.The research results show that the spatial steel truss can exert a good restraining effect on the core concrete.It has the strongest restraining effect on the concrete at the four corners of the cross section,and gradually decreases along the diagonal direction.The area near the steel plate in the middle of the four edges restraining effect is the weakest.At the same time,the steel plate is the key factor that affects the restraining effect of the spatial steel truss on the core concrete.In the case of the same volume steel ratio,the restraining effect on the core concrete from strong to weak is in order of decreasing the spacing of the steel plates,increasing the width of the steel plates,and increasing the thickness of the steel plates.