The main objective of this study was to develop a new type of FRP rebar with focus on ductility and health-monitoring issues. One approach to provide ductility was the use of a hybrid FRP reinforcing bar consisting of different types of fibers, which fail at different strains during the load history of the rebar, thereby allowing a gradual failure of the rebar. The rebar was manufactured using pultrusion and filament winding techniques. These techniques have made it possible to embed fiber optic sensors within the reinforcement, for health monitoring, thus protecting the sensor from the harsh concrete environment. Pseudo-ductile behavior was validated through testing of coupon FRP rebar as well as RC beams. Testing of large-scale beams reinforced with the hybrid FRP rebar exhibited remarkable ductility behavior with ductility indices close to that of beams reinforced with steel rebar. Furthermore, the strain measured from the embedded fibers optics replicates the measurement of conventional LVDT and was reliable up to failure of the beams.

Increasingly, existing concrete structures are being assessed as having insufficient capacity in shear; the development of an efficient and durable means of upgrading such structures is becoming of utmost importance. An exciting solution is the use of tensioned non-laminated carbon fiber reinforced plastic (CFRP) straps as active (stressed) external shear reinforcement for concrete. The use of an active system has several advantages over a passive (unstressed) reinforcement system. In particular, the prestressed CFRP straps provide confinement and enhance the performance of the concrete. Details of a series of tests carried out on a concrete beam strengthened using these novel CFRP shear reinforcing elements are presented. The strain in each of the straps was measured during testing and valuable insight into the shear behaviour of the concrete beam was gained. It was found that the strengthened beam had a much higher shear capacity than the predicted resistance of an equivalent unstrengthened beam.

This paper presents an evaluation method of contribution of continuous fiber sheet to shear capacity of RC members. Different from mild steel, CF sheet is completely elastic up to breaking point without any yielding phenomena. CF sheet works effectively in shear strengthening of concrete members when it is glued on concrete. To evaluate shear contribution of CF sheet rationally, it is necessary to consider bonding and peeling-off behavior of CF sheet. In this paper, we formulate a constitutive model for the interfacial zone between CF sheet and concrete according to the uniaxial test results. Based on this computational model, we propose the evaluation system for shear capacity of RC member retrofitted with CF sheets. The applicability of the proposed method is verified with test results of RC beams.

This paper summarizes the recent research developments of a new structural concept for the design of the hybrid RC circular columns confined in aramid fiber reinforced polymer (AFRP) tube impregnated with epoxy. The AFRP tubes have the dual function of stay-in-place formwork and transverse reinforcement for the structural elements. Although the AFRP tube is not structural member by itself, it will turn into an important seismic resistance member by hybridizing the AFRP tube and the RC column. However, in this lateral cyclic loading test under a constant axial force the bond splitting failure happened on these specimens for lack of bond strength because high strength and large diameter longitudinal reinforcement were arranged excessively. If the hybrid RC columns confined in AFRP tube prevented the bond splitting failure from happening, their high seismic performance could be expected.

Many pretensioning prestressed concrete (PC) beams using the grid glass fiber reinforced polymer (GFRP) reinforcements as prestressing tendons were manufactured. The initial prestressing forces were selected at various levels, namely from 0 to 52.5 % of the tensile capacity of the grid GFRP reinforcement. Then, the PC beams were left outdoors for a long time, namely from seven to eight years. Thereafter, they were demolished to take the grid GFRP reinforcements out. First, the tests on tensile properties of the grid GFRP reinforcements were carried out. Their residual tensile capacities decreased only a little, and moreover, their residual tensile rigidities did not change. Then, the cross sections of the glass fibers of the grid GFRP reinforcements were observed with a scanning electron microscope (SEM). The cross sections remained real circular and the glass fibers were not attacked by alkali of concrete.