231 publications from this institution
This study investigates the behavior of fiber-reinforced polymer-strengthened reinforced concrete beams under static and impact loads. The experimental program includes six beams tested in static loads and seven beams tested against impact loads. Longitudinal fiber-reinforced polymer strips and fiber-reinforced polymer U-wraps were used to strengthen these beams. The section of four beams was modified to have a curved soffit in order to reduce the stress concentration of fiber-reinforced polymer U-wraps and provide confinement effect on longitudinal fiber-reinforced polymer strips. The experimental results showed that the proposed modification significantly increased the beam capacities as compared to their rectangular counterparts strengthened with the same amount of fiber-reinforced polymer material. In addition, this article also provides explanations and discussions on the phenomenon of shifting of the flexure failure mode under static loads to the shear–flexure failure mode under impact loads of all the beams tested in the study, as well as the proper interpretations of the measured impact forces in the tests. From the experimental results, it is recommended that the impact force and inertial force at the very early stage of an impact event should be used to design the impact resistance.
This study investigates the impact behavior of fiber-reinforced polymer (FRP)-strengthened reinforced concrete (RC) beams and FRP contribution to shear strength. Thirteen RC beams (1,500×150×250 mm) were tested against static and impact loads. The beams were strengthened with FRP U-wraps and 45°-angle wraps to investigate the effectiveness of different wrapping schemes. The experimental results show that the debonding strain of FRP under impact loads is slightly smaller than that under static loads. The FRP contribution to shear strength is discussed and verified against a design code. In terms of using the same amount of FRP, 45°-angle FRP wraps provide better performance than the FRP U-wraps in terms of both the load capacity and displacement. Fully wrapping a RC beam with FRP is more efficient than wrapping distributed FRP strips. The impact behavior and failure modes of FRP strengthened RC beams are also discussed.
This study investigates the impact resistance of fiber-reinforced polymer (FRP) confined concrete. Concrete cylinders were wrapped with carbon FRP (CFRP) or glass FRP (GFRP) with a varied number of layers and wrapping schemes. The impact tests were conducted by using drop-weight apparatus at different impact velocities. Dynamic behavior of the specimens has been investigated. The experimental results have shown that the failure modes are very different than those from static tests. Identical specimens experienced different damage as the impact velocities changed. The dynamic rupture strain of FRP was found to be substantially lower compared with that under static loads. As a result, the FRP efficiency factors were 0.17 and 0.56 for CFRP and GFRP, respectively. Interestingly, although GFRP has lower tensile strength and elastic modulus, it showed much better performance against impact compared with CFRP in terms of both the strength and ductility. The higher rupture strain of GFRP compared with CFRP results in higher confinement efficiency of GFRP under impact loads. A confinement model is proposed to predict the confined concrete strength under impact.
In the open literature, there is no investigation into the impact behaviour of prefabricated segmental concrete beams (PSCBs) cast with low CO2-emission fibre-reinforced geopolymer concrete (GPC), reinforced with non-corrodible basalt fibre-reinforced polymer (BFRP) reinforcement, and post-tensioned with carbon FRP (CFRP) tendons. This research, hence, aims to close this existing gap of knowledge. The primary goals are to investigate the effect of dispersed fibres on the impact response of PSCBs and to compare the performance of CFRP versus steel tendons. The experimental results reveal that the PSCBs fail due to excessive joint openings that lead to concrete spalling and flying concrete debris. The inclusion of dispersed fibres in the concrete postpones crack development, reduces reinforcement strain, and effectively mitigates concrete spalling and stiffness degradation of the beams. While fibres show limited influence on the deflection response of PSCBs, as the deformation of segmental beams is predominantly governed by joint openings with no fibres bridging across the joints, they play a crucial role in preventing severe damage during impact events. The impact response of beams post-tensioned with CFRP tendons is analogous to those with steel tendons. Notably, both the CFRP tendon and BFRP reinforcement remain intact even when the beam fails under impact loads. This implies that CFRP tendons and BFRP reinforcement can be successfully employed in constructing durable and sustainable segmental GPC beams capable of withstanding impact loading. A high-fidelity numerical model of PSCBs made of GPC and FRP tendons and reinforcement subjected to impact loads is also developed, for the first time, to supplement the discussions of experimental findings.
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