GFRP strengthening of RC beams with tension lapsplices under fatigue loads

Lap splices are a common construction method for joining steel rebars in reinforced concrete beams because of their simplicity and low cost. The bond strength between the concrete and reinforcing bars in a splice is crucial to many aspects of the behaviour of a reinforced concrete member. Fatigue flexural loading imposes severe demands on the strength and ductility of the lap splice region in reinforced concrete structures. This study presents an experimental investigation of the effect of externally bonded glass fiber reinforced polymer (GFRP) sheet on the performance of reinforced concrete (RC) beams with lap-splices under fatigue loading. Different fatigue load ranges were applied for wrapped and unwrapped beams. The test matrix consists of ten large-scale rectangular RC beams (350 mm deep x 250 mm wide x 2200 mm long). The specimens were divided into two groups namely unwrapped beams as a control and GFRP-wrapped beams. In each group, one beam was monotonically loaded and four beams were tested in fatigue at different load ranges. Each beam contains two 20M rebars lap-spliced in the tension zone of a constant moment region, two 10M bars in the compression zone, and 10M stirrups in the shear zones. The beams were tested in four-point bending with a simply supported span of 1800 mm. Load vs. deflection response and load range vs. fatigue life were monitored up to failure. The test results showed that GFRP strengthening increases the bond capacity of a lap splice for both static and fatigue loading. In addition, unlike the sudden bond failure of unwrapped beams, the GFRP wrapped beams experienced a gradual increase in deflection as the number of cycle increased providing a warning sign before failure.