Hysteretic Behavior Of Reinforced Concrete Columns Cons Idering The Effect Of Axial-Flexure-Shear Interaction

Reinforced concrete column is the main vert ical load bearing member in the RC frame structure, which is also the major member to withstand the horizontal force. The experimental research and the field reconnaissance have demonstrated that reinforced concrete columns with light or widely spaced tran sverse reinforcement are vulnerable to shear failure and subsequent axial failure during earthquake shaking. Although the traditional fiber model can simulate accurately the flexure failure of reinforced concrete members, but it cannot simulate flexure-shear failure and shear failure reasonably, which even cannot simulate the axial-flexure-shear coupling effect of columns. Without considering the axial-flexure-shear interaction effect, it will overestimate the ductility of reinforced concrete structures, and thus cannot take account of the later deterioration characteristics. Therefore, in order to assess vulnerability more reliably of reinforced concrete structures that under earthquake effects, the paper give full consideration to the axial-flexure-shear displacement response of reinforced concrete members and assess effectively to the strength and deformation capacity under different failure mechanisms of RC members. The main contents are as follows:(1)A fiber beam-column element in conjunction with shear spring and axial spring attached to its ends was proposed to simulate the axial-flexure-shear interaction of reinforced concrete columns. Fiber beam-column element is used to simulate flexure mechanism and shear spring and axial spring are used to simula te shear mechanism and axial mechanism respectively. And the Limit State Material models and the corresponding shear limit curve and axial limit curve are used to determine the shear and axial failure point. This model finally can define the axial-flexure-shear interaction effect from the element level.(2)To validate the reliability of this proposed numerical model, the reinforced concrete columns with different failure modes under axial and reversed horizontal static loading were modeled via Open Sees and their hysteretic behavior was analyzed. Wherein the calculation results of hysteresis curves, skeleton curves, ductility and energy dissipation coefficient are compared with the test results have less errors. The comparison of the numerical results and th e test results shows that the model considering the effect of axial-shear-flexure interaction provides a preferable estimation for the pinching, strength and stiffness degradation of the reinforced concrete columns. It can consider the changes in axial loa dings and lateral displacement, and it also simulate the mechanical properties of the reinforced concrete members under complex stress conditions.(3)It can obtain the destroy mode of columns effectively according to the displacement ductility values that calculated form the numerical model of RC columns with considering axial-shear-flexure interaction. Within a certain range of axial compression ratio, the ductility columns with low axial load ratio is better than the ductility of columns with high axial l oad ratio. The axial load ratio has a significant effect on the stiffness degradation of the columns in the post yield stage.In summary, the numerical model that considering the axial-flexure-shear interaction effect of reinforced concrete columns can sim ulate the hysteretic behavior of RC members, and using this model can simulate the parameter analysis of columns reasonably and accurately.