Lateral-Impact Behavior of Axially Preloaded RC Columns Strengthened with Large-Rupture-Strain FRP Wraps

Abstract

Strengthening using large-rupture-strain fiber-reinforced polymer (LRS-FRP) laminates can effectively enhance the deformation and energy absorption capacity of reinforced concrete (RC) components under static and seismic loads. This study explores the application of LRS-FRP, particularly polyethylene terephthalate FRP (PET-FRP), to increase the impact resistance of RC columns in instances wherein high deformability and energy absorption capacity are necessary. Six RC column specimens, preloaded axially with heavy blocks and laterally impacted using a pendulum apparatus, were wrapped with PET-FRP. The dynamic responses of the columns, including the impact force, axial force, and lateral and axial displacements, were carefully recorded. Local strengthening schemes applied at the impact points of the columns and ends effectively enhanced their anti-impact performance without transferring damage to unstrengthened areas. As regards middle-impact specimens, PET-FRP wrapping changed the failure mode from shear to flexure failure, thereby increasing the lateral-impact resistance and deformation recovery capacity and preventing collapse owing to the axial bearing capacity loss. In bottom-impact specimens, PET-FRP improved ductility in the shear failure mode and maintained a consistent trend in the damage degree of flexure and shear failure columns across varying axial compressive ratios. Within an axial compression ratio of < 0.32, the axial force reduced flexural and shear damages. However, excessive axial preloading (axial compression ratio = 0.64) increased the flexural deformation because of the P-delta effect and shear damage owing to the increased risk of FRP debonding.