Study On Seismic Performance Of RC Rectangular Hollow Bridge Columns Constrained With FRP

Bridge columns is one of the key parts in bridge seismic design, its seismicperformance should be highly regarded. The seismic response of the bridge is reducedby hollow columns, due to its high strength/quality ratio and high stiffness/mass ratio.Therefore, hollow column has been widely used in bridge engineering. The existinghollow columns were designed according to old seismic codes. And as bridgeperformance was degenerated in conditions of natural and vehicular, some hollowcolumns’ seismic performance couldn’t meet the requirements of current seismiccodes in western China.The fiber reinforced polymer (FRP) is one new reinforcement material. It’swidely used in bridge engineering reinforcement due to its advantages such as its highstrength and good corrosion resistance. However, the study on seismic retrofittingapplied techniques on reinforced concrete (RC) rectangular hollow bridge columns isless. So it’s necessary to study on RC rectangular hollow bridge columns constrainedwith FRP.In order to investigate the seismic performance of reinforced concreterectangular hollow bridge columns constrained with fiber reinforced polymer (FRP),12column specimens were designed with slenderness ratio is L/b=4and L/b=8,respectively. Cyclic tests and OpenSees finite element simulation under constant axialloads and uniaxial bending were carried out in this paper. Moreover, Using test fittingmethod, simplified load-displacement hysteretic model for bridge columns wasestablished.(1) The experimental results indicated:Under low axial compression load, FRP reinforced changed the failure modesand damage location of RC rectangular hollow columns.The ductility and dissipated energy of the RC rectangular hollow bridge columnsconstrained with FRP improved significantly. For the columns with L/b=8, the totalenergy dissipation and the displacement ductility coefficient mostly increased about32.6%and93.6%, respectively. For the columns with L/b=4, the total energydissipation and the displacement ductility coefficient mostly increased about25.8%and65.4%, respectively.(2) Numerical simulation result showed: Using hysteresis material model and considering the P-△effect, the simulationresults would be in good agreement with the test data. It has high efficiencycalculations and could be used in further parameter analysis.The parameter analysis showed: the ductility and dissipated energy of the RCrectangular hollow bridge piers constrained with FRP improved significantly. FRPlateral restriction force flchanging in range of2.74~6.84, the ductility and dissipatedenergy of the RC rectangular hollow columns were improved similarly. The lateralforce of the column specimens improved with the increasing of axial compressionratio n and concrete strength. But it decreased with the increasing of slenderness ratioL/b. The dissipated energy improved with the increasing of axial compression ratio n.The deformation and ductility improved with the increasing of slenderness ratio.(3) According to the destruction of the RC rectangular hollow pier constrainedwith FRP, and based on theoretical analysis and test fitting method, consideringstrength and stiffness degradation, two hysteretic model for slenderness ratio isL/b=4and L/b=8were established, respectively. Moreover, its unload stiffness andreload stiffness regression formulae were given.