Seismic retrofitting of rectangular reinforced concrete columns using fiber composites for enhanced flexural strength

Abstract

This article introduces an improved method using fiber composites for seismic retrofitting of rectangular reinforced concrete columns with a large side aspect ratio. To retrofit an existing column, near-surface-mounted (NSM) glass fiber reinforced polymer (GFRP) bars were adopted to enhance flexural strength, and then the potential plastic hinge region was confined by carbon fiber reinforced polymer (CFRP) jackets and CFRP anchors to ensure a ductile behavior. To evaluate the effectiveness of the strengthening method, five rectangular reinforced concrete model columns with a cross-section of 200 mm × 360 mm were constructed and tested under simulated seismic loads. The effects of CFRP jackets, CFRP anchors and NSM-GFRP bars on seismic behavior of the retrofitted columns in terms of strength, ductility and failure modes were investigated. The test results validated the effectiveness of using CFRP jackets and CFRP anchors to improve the strength and ductility of rectangular reinforced concrete columns with a side aspect ratio of 1.8. The use of NSM-GFRP bars, especially NSM reinforcement with local confining jackets, was also proved to be a promising solution toward enhancing the flexural resistance of reinforced concrete columns. Furthermore, an analytical method, accounting for the effects of CFRP jackets, CFRP anchors and NSM-GFRP bars, was developed to predict the flexural strength of retrofitted reinforced concrete columns.