Residual Performance and Damage Restorability of Reinforced Concrete Flexural Column after Earthquake

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The axial capacity of reinforced concrete columns during shear deterioration after flexural yielding was investigated. The restorability of the axial capacity after the deterioration was also studied. Five column specimens with the same dimensions, reinforcement and materials were tested. They were designed that the shear capacity was equivalent to the flexural capacity. They were subjected to lateral forces in a cyclic manner producing anti-symmetric bending moment distribution under a constant axial load equivalent to 0.2σ_B in the compressive stress level (σ_B : compressive strength of concrete). Each specimen was loaded in the axial direction after corrected the residual deformation by the lateral loading.The following conclusions were obtained.(1) It was observed that the deterioration of the axial strength was caused by dominant diagonal shear cracks in the mid-span of columns, and the deterioration was significantly large immediately after the shear cracks occurred.(2) The analysis based on truss and arch mechanisms well predicted the deterioration of axial strength, which related strongly the deterioration of concrete compressive stress of strut in truss mechanism(3) The injection of epoxy into the diagonal shear cracks was effective to recover the lateral and axial strength perfectly.