The compression behavior of CFRP-repaired damaged square RC columns

Abstract

A small number of experimental studies have investigated the compression behavior of damaged concrete repaired with carbon fiber reinforced polymer (CFRP) composites. As a result, only a few stress-strain models have been proposed for CFRP-repaired plain concrete to date. In practice, most of the concrete in structural elements is confined by transverse steel reinforcement, so understanding the axial compressive behavior of CFRP-repaired damaged steel-confined concrete (CRDSCC) is of great significance for implementing rapid yet reliable repair work after a severe earthquake. The main purpose of the present research was to explore the effectiveness of repairing pre-damaged square RC columns with externally wrapped CFRP sheets. Pre-damage levels and quantities of internal transverse stirrups and of externally wrapped CFRP sheets were chosen as test variables in this experimental investigation. A total of 27 square RC columns were fabricated and concentrically stressed to five specified axial deformation levels. After being repaired with CFRP sheets, the damaged RC columns were reloaded up to failure under monotonic or cyclic loading. The test results show that the application of external CFRP wrapping is highly effective for enhancing/restoring the strength and strain capacity of pre-damaged steel-confined concrete although the damage has adverse effects on the initial elastic modulus, ultimate strength, and ultimate strain of CRDSCC. A stress-strain model for CRDSCC is also proposed, and the close agreement between the prediction and the test results shows that the proposed model can well capture the effect of pre-damage on the behavior of CRDSCC.