Investigation On Mechanical Behaviors Of Steel Reinforced Concrete T-shaped Section Columns Under Compression-flexure-shear-torsion Actions

Because of the large number of section steel inside steel reinforced concrete(SRC)special-shaped columns,the mechanical behaviors and structural applicability are significantly improved than those of reinforced concrete special-shaped columns.At present,researches at home and abroad mainly focus on the investigation of bearing capacity and seismic performance of SRC special-shaped columns under eccentric compression,bending and shear actions.However,there is a lack of investigation on the mechanical of under compression-flexure-shear-torsion actions.Thus,the research objective is exterior columns(T-shaped columns)of bottom frame in SRC structures with special-shaped columns in this paper extracted,and the parameters are shaped-steel layout,axial compression ratio,torsion-bending ratio and limb height-thickness ratio.The mechanical behaviors of SRC T-shaped columns was studied by experiments,numerical simulation and theoretical analyses.The influences of the parameters on the mechanical behaviors of SRC T-shaped columns was analyzed.The failure mechanism and seismic performance indices of SRC T-shaped columns were revealed.The main results are as follows:(1)The experiments of fifteen SRC T-shaped columns were conducted under compression-flexure-shear-torsion actions,using a self-developed spatial torsion loading device.The failure process and modes of SRC T-shaped columns were obtained subjected to compression-flexure-shear-torsion actions.It is shown that The failure modes of SRC T-shaped columns with full web or hollow web were similar,and the main failure modes of the specimens were web compression failure and concrete failure in the flange shear stress superimposed zone.With the increase of torsion-bending ratio,the failure modes of SRC T-shaped columns gradually transited from bending failure to torsion failure.Under the same loading conditions,the failure modes of SRC T-shaped columns with hollow web were more serious than those with full web.(2)The column-top load-displacement(P-Δ)curves and torsion-rotation(T-θ)curves of SRC T-shaped columns were obtained under compression-flexure-shear-torsion actions.The influence of the parameters on the hysteretic loops and skeleton curves of SRC T-shaped columns was analyzed.The mechanical properties indices of SRC T-shaped columns was studied,such as degradation of strength and stiffness,ductility displacement and rotation,rotation of lateral displacement,lateral energy dissipation,rotational energy dissipation and comprehensive energy dissipation,ultimate load and residue deformation.The bearing capacity of SRC T-shaped columns was analyzed by standardized calculation method.The results showed that the horizontal bearing capacity of steel reinforced concrete T-section columns is in the order of full web,hollow T-shaped web and hollow channel web from high to low.(3)The increase of torsion-bending ratio,the lateral bearing capacity and deformation of the specimens under compression-flexure-shear-torsion actions decreased while the torsion bearing capacity and torsion deformation increased.The reduction of lateral bearing capacity and deformation and the growth of torsion bearing capacity and deformation of SRC T-shaped columns with hollow web were larger than those with full web,indicating that the torsional-bending ratio had a slightly impact on the SRC T-shaped columns with full web.Increasing the axial compression ratio properly was beneficial to the lateral bearing capacity and deformation of SRC T-shaped columns with full web but contrary to those with hollow web.It was better for the energy dissipation of SRC T-shaped columns to properly increase the axial compression ratio and reduce the limb height-limb thickness ratio.The energy dissipation capacity of SRC T-shaped columns with full web was better than those with hollow web.(4)The shear and torsion bearing capacity analyses model of SRC T-shaped columns under compression-flexure-shear-torsion actions was proposed.On the basis of the experimental data,the numerical simulation analysis method of SRC T-shaped columns was built using Abaqus,and the analytical results were validated with the experimental data.The numerical simulation results were in good agreement with the experimental results.Then,the parameters of axial compression ratio and torsion-bending ratio were extended,and the law of mechanical behaviors of SRC T-shaped columns under compression-flexure-shear-torsion actions was obtained,which provided a basis for the calculation and analysis of the torsion bearing capacity of SRC T-shaped columns under compression-flexure-shear-torsion actions.(5)The relativity of compression,shear and torsion as well as bending and torsion was introduced based on variable angle space truss theory and plastic theory.Considering the compression-flexure-shear-torsion combined actions,the calculation formula of the torsional bearing capacity of SRC T-shaped columns under compression-flexure-shear-torsion actions was established.