FRP for Infrastructure Applications: Research Advances

Driven by the incentive to break the infrastructure corrosion cycle, fiber reinforced polymers (FRP) composites were introduced as potential materials to produce corrosion-free infrastructure [1]. FRP were also sought to create a new generation of smart infrastructure where performance monitoring can be integrated in structural design and construction [2]. The widespread production of synthetic fibers, including glass fibers, carbon fibers and Kevlar fibers, enabled the creation of FRP composites with much improved mechanical and durability performances for infrastructure applications compared with classical construction [3]. Research and development over the past 40 years has addressed practical challenges for enabling the use of FRP materials in infrastructure applications [4]. In this Special Issue of Fibers , nine publications are dedicated to reporting progress in research examining the use of FRP in infrastructure applications. The reported papers can be classified into four categories addressing: innovative structural systems using FRP, improving energy dissipation in infrastructure using FRP, methods for computational simulation of structural elements using FRP and finally new FRP materials synergies for infrastructure applications. The first group of papers in the Special Issue reported innovative FRP structural systems. Rasheed et al. [5] investigated failure modes and flexural capacity in concrete T and rectangular beams with transverse U-wrapped carbon fiber reinforced polymer (CFRP) anchorage in addition to externally bonded sheets of flexural CFRP. Results showed that this combination shifted the failure mode from the original debonding to flexural failure and, thus, provided higher flexural capacity by delaying delamination and debonding in the flexural CFRP sheets and by providing anchorage through shear friction. Moreover, Al-Rahmani and Rasheed [6] proposed covering rectangular concrete columns with FRP wrap. The authors showed that the pairing of FRP confinement with steel ties confinement required nonlinear analysis for the determination of axial systems for the repair of concrete structures. Toughness, flexural and compressive strengths, resistance to salt-frost scaling, penetrability, and drying shrinkage were investigated for different fiber types (including polypropylene, basalt, and steel). The results revealed that the use of nano-silica improved the compressive strength of beams, the flexural strength at 14 days, toughness, and the resistance to salt-frost scaling in NFRM. The use of nano-silica showed up to 10% higher flexural strength at 14 days compared with control beams. Furthermore, the addition of 2% nano-silica increased toughness by up to 53% compared with control specimens. On the other hand, Jabr studied the effect of a fiber-/fabric-reinforced cementitious matrix (FRCM), consisting of a fiber mesh or grid encased in a cementitious bonding material, on the flexural strength of steel-reinforced concrete beams. The results showed that FRCM strengthened with polybenzoxazole (PBO) fibers significantly increased the ultimate capacity of the beams compared to glass and carbon FRCM. Increases in ultimate capacity of 33% and 25% were observed for beams with low and moderate steel reinforcement ratios, respectively, when compared to an un-strengthened beam. Post-crack and post-yielding stiffnesses were increased, and the axial stiffness ratio decreased with the use of PBO in FRCM.