APPLICATION OF GFRP SHEET FOR STRENGTHENING OF YIELDED REINFORCED CONCRETE BEAMS

Abstract

The use of fiber reinforced polymer (FRP) by the civil engineering community spans more than two decades. It has been applied to many purposes for civil engineering structures not only for new structures but also for strengthening of the deteriorated structures. Many researches have been done to apply the FRP materials for strengthening, particularly due to an increase on load requirement, a change of use or due to a degradation problem or some design/construction defects. However, it is still very rarely studies on application of the FRP materials for strengthening of the yielded reinforced concrete members. This study presented the results of the application of GFRP sheet for strengthening of yielded reinforced concrete beams. A series of specimen of reinforced concrete beams with dimension of 15 cm x 20 cm x 270 cm were casted. All casted specimens were pre-load to the yielding of steel reinforcement before application of GFRP sheet. The specimens of the strengthened yielded beams using GFRP sheet were divided into four types which were: type FH-1 was specimen with 1 layer on full length of the beam span, type FH-12 was specimen with 1 layer on full length of the beam span added 1 layer with length of half of the beam span patched at the beam centre, type FH-3 was specimen with 3 layer on full length of the beam span and type FH-32 was specimen with 3 layer on full length of the beam span added 2 layer with length of half of the beam span patched at the beam centre, respectively. The results indicated that the flexural capacity of beams strengthened with one layer (type FH-1) and two layers (type FH-2) of GFRP sheet on overall length of beam were 26 kN and 35 kN, respectively. On the FH-12 beams with one layer on full length added with two layer of GFRP with the length of half of the beam span at the beam centre indicated higher capacity which was 30 kN. Furthermore, on the FH-32 beams with three layers of full length added with two layer of GFRP with the length of half of the beam span at the beam centre indicated higher capacity which was 42 kN. For the comparison, it was noted that the ultimate flexural capacity of strengthened concrete beams beyond that of original beam (ultimate capacity of original beam (BN) was 16.5 kN). The presence of cracks influenced to the prematurely debonding of the GFRP laminate. This caused the limitation of the experimental ultimate capacity