Strengthening reinforced concrete girders with 'n' and 'T' cross-sections

The main aim of the programme of research described in this paper is the experimental validation of a design approach which is being put forward for the strengthening of reinforced concrete beams with channel (`n') and tee (`T') shaped cross-sections. The beams were strengthened by casting a concrete overlay on to their upper surfaces to act as a concrete compression zone within the structure of the strengthened beam. Each overlay was provided with closed links which were welded to the links in the original beam but only in the regions close to the supports. The programme of laboratory-based work consisted of tests on full-size beams, three with a channel-shaped cross-section and five with a tee-shaped cross-section. The test beams were loaded to destruction. The test results showed that the strengthened beams acted as a single unit, failed in flexure in a ductile manner and achieved their full flexural capacity. The load-carrying capacities of the strengthened beams were found to be as high as 163% of the capacity of the beams before strengthening. This approach is believed to have significant advantages over other comparable approaches to strengthening since there is less disruption to the original beam as the links in the concrete overlay are not required to extend down into the body of this beam.