Tests on FRP-retrofitted tension-controlled eccentric and biaxial high strength concrete columns

Abstract

Several studies investigated fiber reinforced polymers (FRP) to strengthen eccentric RC columns. However, little is known about the feasibility of FRP-retrofitting of eccentric and biaxial high strength concrete (HSC) columns, especially the tension-controlled ones. This study presents an experimental investigation on six HSC columns under large eccentric and biaxial moments, strengthened using FRP. The objective is to evaluate the feasibility of a proposed stress-oriented and economic FRP strengthening scheme. The test parameters are the number of tension-side FRP layers and the load eccentricity condition, uniaxial vs. biaxial. The study proved the efficiency of the proposed FRP-strengthening in enhancing flexural strength and ductility of uniaxial columns; as flexural capacity increased by 54% although strength gain decreased with increasing tension-side FRP layers. Biaxial columns, however, lost ductility and gained no strength suggesting the need for heavy transverse FRP confinement to overcome stress concentration due to failure mode transformation to compression failure.