Research On Mechanical Property And Seismic Property Of Steel Truss Confined Concrete Columns

The complementary effect can improve the property of composite columns.Then composite columns have high bearing property,well ductility and well seismic property.For the materials components in composite columns,the core concrete is the most complex part.For the mechanical properties of composite columns,the sectional form is key influence factor.Therefore,the confined concrete was studied in detail at first.Meanwhile,based on the analysis of extensive researches,the angle steel truss(ST)confined concrete composite column was proposed.Furthermore,this paper studied the mechanical property and aseismic property of ST confined concrete composite columns.The main work of this paper could be concluded as follows:(1)This paper defined the main influencing factors of concrete under complex stress state.Then,three kinds of failure criterion of concrete under complex stress state were established,include the five-parameter A failure criterion(shear stress as the dominant factor),the five-parameter B failure criterion(hydrostatic stress as the dominant factor)and the six-parameter failure criterion(two factors considered).Based on the validation,the scope of application of three new failure criteria was determined.(2)Based on the uniaxial compressive performance of unconfined concrete,considering the lateral confining stress,this paper established the simplified constitutive model for confined concrete.For further theoretical research,the axial stress model is proposed based on the proposed failure criterion,the axial strain model is proposed based on the energy method.At last,the fine constitutive models are proposed for active confined concrete and passive confined concrete.(3)This paper tested the axial mechanical properties for eleven ST composite columns and one angle steel truss column.And the failure process,failure mode,bearing capacity and mechanical properties of core concrete are analyzed.Based on the analysis,this paper established the axial bearing model for ST composite columns and the practical constitutive model for core concrete in ST confined concrete composite columns.(4)The pseudo-static testing was completed for eight ST composite columns,the failure process,failure mode,lateral bearing capacity,deformation capacity and energy dissipation capacity are analyzed.The aseismic performance of ST specimens is defined.The influence of the combination mode of batten plate,the size of batten plate,the size of angle steel and the ratio of axial compression on the seismic performance of composite column is studied.(5)Based on finite element analysis software,this paper studied the seismic property of ST confined concrete composite columns.The effects of axial compression ratio,angle steel ratio and the combination mode of batten plates were studied.The analysis results showed that the content of angle steel is the most important factor,and confining effect can improve the fullness of hysteretic curve and critical axial compression ratio.(6)This paper established sectional analysis model of ST confined concrete composite columns under compression and bending.The practical computational model was proposed for axial force-bending moment relationship and moment-curvature relationship.At last,the moment curvature restoring force model was established.(7)Based on the sectional analysis model,the yield curvature model and the ultimate curvature model were fitted,and sectional ductility coefficient was proposed.Finally,the damage evaluation method of ST confined concrete composite columns was proposed.