Damage Mechanism And Strength Calculation Of Steel Reinforced Concrete L-shaped Column Subjected To Combined Compression,Flexure,Shear And Torsion Loads

Technical specification for concrete structures with specially shaped columns(JGJ149-2006),expands the application scope of concrete specially shaped column structure,however,due to the low bearing capacity,poor seismic performance as well as more concentrated steel bars,some scholars have proposed that the steel is mainly distributed in the section of specially-shaped columns.The steel reinforced concrete specially shaped column structure,not only inherits all the advantages of specially shaped column structure,but also absorb the quality elements of steel reinforced concrete(SRC)structure,can overcome the defects of ordinary reinforced concrete specially-shaped columns and enlarge the application scope of specially-shaped columns.This kind of new structure has been studied both at home and abroad,but there are not many reports about the mechanical properties of the new structure under the combined compression,bending,shear and torsion.On the basis of previous studies,this paper makes a systematic study on the mechanical properties of SRC L shape columns subjected to compression,bending,shear and torsion loads.In order to reveal the seismic behavior of SRCL shape column under compression-flexure-shear-torsion combined action,18 specimens of SRCL shape columns were designed for the constant compress and reversed cycle flexure-shear-torsion loading test.The vary parameters of torsion-moment ratio,shaped-steel layout and ratio of section height to section thickness were considered.;The failure process and failure pattern were observed;the hysteretic curves of torque-torsion angle and loading-displacement,the character results of crack,yield,peak and failure point were obtained.Based on the test data,the seismic indexes,such as bearing capacity,ductility,energy dissipation,strength and stiffness degradation were analyzed deeply.The research results show that:the failure pattern of specimens ware flexural failure,flexural shear failure,crankle failure and torsion failure;small torsion-bending ratio specimen occurred flexural failure,while large torsion-bending ratio specimen occurred torsion failure.In this paper,finite element analysis of seismic performance of the specimens using ABAQUS software,and the compared results show that:the solid web steel test bending bearing capacity is better than that of hollow steel and hollow channel steel;the hollow channel steel test torsion bearing capacity is better than that of hollow steel and solid web steel.The full solid web SRCL shaped column,according to the calculation model of cantilever beam,can be calculated combined with the Technical specification for concrete structures with specially shaped columns(JGJ149-2006)and equilibrium(plastic)truss theory.The formula for the ultimate flexural capacity of hollow steel and hollow channel steel SRCL column is derived from the theory of equilibrium(plastic)truss theory.The calculated results of the formula of flexural bearing capacity are compared with the experimental results.The results show that:the axial compression ratio and the application of torque have a great influence on the ultimate bearing capacity of the specimen.Comparison of the specimens of the full solid,the hollow and the hollow channel steel style,under the axis pressure with the axial compression ratio of 0.15,the test ultimate bearing capacity values decreased by 27.4%,28.1%and 28.6%,respectively;comparison of the specimens of the full solid,the hollow and the hollow channel steel style,under the small torsion-moment ratio condition(0-0.3),the bearing capacity of the specimen gradually reduced by 26%,30%and 30%,respectively,with the increase of the torsion-moment ratio,while,under the high torsion-moment ratio condition(0.89),the bearing capacity of the hollow channel steel style specimen reduced greatly by 63.6%.