SEISMIC ANALYSIS OF RECTANGULAR HOLLOW SECTION RC PIERS INCLUDING FLEXURE-SHEAR COUPLING BEHAVIOR

Reinforced concrete (RC) high bridges with hollow section pier are commonly in the mountains of sourthwesten China. The seismic hazard level of sourthwesten China is high and has drawn more and more attention after 2008 Wenchuan earthquake. Many flexure-shear coupling damage phenomenons of piers have been observed in recent earthquakes. Hollow section member may perform flexure-shear coupling behavior and undergo strongly nonlinear responses when the pier subjecting severe earthquakes. Some analysis models accounting flexure-axial coupled effects were proposed, however, few model is proposed for RC hollow section piers mainly impact by the flexure-shear coupling situation including geometric nonlinearity. In this paper, a multi-dimensional fiber-based section model, which can be used in either Timoshenko or flexibility-based element formulation considering shear deformation with no distinction, is proposed. The cyclic soften membrane model (CSMM) bi-axial constitutive relationship is introduced into the fiber model and implemented into the finite element program, OpenSees. The calculation procedure is illustrated on the section level (implemented as TimoshenkoSection class), fiber level (BiaxialFiber class) and membrane material level (CSMM material class). One directional lateral cyclic static experiment carried on scaled hollow section piers are simulated in this paper. The result deduced from the numerical model is compared with the experiment results, and it shows good agreements for the strength degradation and pinching effect. This fiber-based section model provides sufficient accuracy and computational efficiency hollow section RC member nonlinear issues. And further researches will focus on the flexure shear induced damage and collapse for bridge structures.