Full Session with Abstracts
Carbon fiber reinforced polymers (CFRP) materials can be used as an efficient technique for shear strengthening of reinforced concrete members due to its light-weight and high strength. Numerous data on shear strengthening of reinforced concrete beams using CFRP materials is available; however, most of the previous studies in shear strengthening were limited to the use of unanchored CFRP materials. In such strengthening systems, the interface bond between the CFRP materials and concrete surface is the main path to transfer shear forces from the beam to the bonded CFRP materials. Generally, the interfacial bond is the weakest element in the strengthening system and failure usually initiated due to debonding between CFRP materials and concrete surface at loads less than 40% of the ultimate tensile capacity of the CFRP material. A comprehensive experimental study was carried out to evaluate the performance of full-scale reinforced concrete T-beams strengthened in shear with anchored CFRP materials using CFRP anchors. The experimental program consists of 48-in. (1220 mm) deep T-beams with transverse steel ratios of 0.09% and 0.16% while flexural reinforcement was kept the same for all specimens. All specimens were designed to fail in shear and were strengthened with various CFRP layouts and CFRP reinforcement ratios. Test results show that specimens strengthened with anchored CFRP strips were able to resist loads that are 50%-90% higher than the non-strengthened specimens. All test developed a brittle shear failure mechanism due to the fracture of the CFRP strips. Test results demonstrate that CFRP anchors can be used as an effective anchorage system in shear strengthening of reinforced concrete beams. The use of CFRP anchors substantially enhance the shear performance of the strengthened beams and were able to develop the full tensile strength of the CFRP strips causing them to fracture at their ultimate capacity. The anchored CFRP system was found to be consistently reliable even in specimens with large amount of transverse steel reinforcement. Transverse steel reinforcement crossing the critical shear crack yielded before ultimate capacity is reached in all the tests. Strains in CFRP were found to be uniformly distributed over the full length of the CFRP strip after the complete debonding of the strips from the concrete surface causing a noticeable reduction in the shear stiffness of the specimens.