Retrofitting of faulty reinforced concrete frame structures using two strengthening techniques

Abstract

Experimental findings and detailed analyses of the overall structural performance of properly detailed and strengthened reinforced concrete (RC) frame structures with defects are presented. Two strengthening techniques were implemented on the faulty frame structures in order to restore lost capacity due to improper detailing of the main tensile steel for both closed- and open-jointed frame systems. The strengthening techniques implemented were near-surface mounted (NSM) steel bars and external un-bonded prestressed steel bars. Three defects were considered, two of them pertaining to frame structures with closed joints and one pertaining to open-jointed frame structures. In total, 11 RC frame specimens divided into four groups were configured, casted and then tested until complete collapse under monotonic incremental loading. It was found that strengthening based on external prestressed bars had a significant effect on both the ultimate capacity and developed ductility of strengthened open-jointed frame structures, while its effect on closed-jointed frame structures was small. For the closed-jointed frame structures, strengthening with NSM steel bars produced greater enhancement in ultimate capacity than the prestressed bar strengthening technique.