Experimental Study On Seismic Behavior Of Reinforced Concrete Column Strengthened With Ultra-high Performance Concrete

In order to improve the seismic behavior of RC columns under high axial load ratio,to improve small bias brittle failure of RC columns under high axial load ratio,decrease serious damage or even collapse of the frame structure,ultra-high performance concrete(UHPC)with the characteristics of super high strength,high toughness and low porosity,jacketing was proposed to strengthen the model column specimens,and experimental study on seismic behavior of the specimens was carried out.Based on the analysis of test results,design method of the bearing capacity,deformation calculation model of UHPC jacketed columns and quadrilinear recovery force model of RC columns are proposed.The main research contents are as follows:(1)Four UHPC jacketed columns,one concrete columns strengthened with UHPC steel mesh and two non-strengthened columns were designed.The specimen failure process and failure pattern,hysteretic property,deformation capacity and energy dissipation capacity are analyzed by low cycle reversed loading.The results indicated that the concrete column strengthened with UHPC,specimen failure changes from brittle small bias failure to large bias failure,component bearing capacity and energy dissipation capacity are improved significantly.The external UHPC jacketing can better solve the problem of frame columns with high axial load ratio in practical engineering.(2)Based on the plane-section assumption,the mechanical analysi were evaluated at crack state,yield state and peak state respectively.The calculation formulas for flexural capacity of the UHPC jacketed columns by combining the constitutive models of materials were proposed.By contrast,the calculated results agree well with the test results.It can provide a reference for practical engineering.(3)The deformations were calculated at crack state,yield state,peak state and ultimate state,respectively,and the simplified skeleton curves were then obtained by combining the bearing capacity results.Finally,a quadrilinear recovery force model of concrete column was proposed,by establishing the hysteresis rules and the numerical relations between the damage factor and unloading stiffness.