Experimental study on anchoring of FRP-strengthened concrete beams

Abstract

This study aims at determining an effective technique for anchoring reinforced concrete beams strengthened using FRP composites. Fourteen reinforced concrete beams were cast and strengthened with FRP. Twelve of them were anchored using three different techniques: FRP anchor; bolted steel plates ancho, and FRP sheet and bolted steel plate’s anchors, and two beams were unanchored and left as a control. The beams then were tested under four-point bending to assess their structural performance in terms of failure modes, and load-displacement relations. The experimental results have clearly shown that the unanchored beams suffered from premature debonding failure, while the FRP-anchored beams experienced concrete cover separation failure, and the presence of end anchorages in the bolted steel plates and FRP sheet and bolted steel plate’s anchor's beams had shifted the failure mode to a less critical one. The anchored beams showed an increase in the ultimate load-carrying capacity accompanied by a reduction in mid-span deflection in different percentage with respect to the control beam. It was also observed that the FRP and/or steel U-jackets increase the shear capacity of the anchorage zone, therefore result in higher anchorage efficiency of FRP-strengthened concrete beams. The results also revealed that the FRP sheet and bolted steel plate’s anchors U configuration was the best anchorage system in terms of the structural performance factor. Developing an anchor system to prevent plate end debonding failure is vital for the successful design of strengthening systems using FRP composites.