Innovative GFRP sections shape and proportions in civil engineering structures

Abstract

Although traditional materials (steel, concrete, timber and masonry) still dominate the building industry, new materials are constantly being explored by engineers and scientists. For instance, the use of the so-called FRPs (Fibre-Reinforced Polymers) is gradually spreading worldwide [1-4]. The main idea of FRPs is the combination, on a macroscopic scale, of two different long continuous fibres and a polymeric resin. More specifically, high strength fibres (glass, carbon, aramid or ultra-thin steel wires) provide strength and stiffness while the resin (polyester, vinylester or epoxy) protects the fibres and guarantees the stress transfer between them. As a result, enhanced final properties are obtained with respect to those exhibited by the individual constituents. Among several type of fibers, Glass Fibre Reinforced Polymers (GFRP) are widely used due to their relatively low cost, although glass fibres exhibit much lower elastic modulus and ultimate strength than carbon fibres. In addition, some additional issues emerge with regard to durability in alkaline environments and long-term response under sustained stresses. FRP pultruded beams take advantage of their principal features [5-6]. Since the late 1990s, among the FRPs elements, those frequently used in civil engineering are the pultruded ones. They are obtained by the pultrusion process that make possible to produce such profiles with both closed or open cross sections; the only limitation is that the same cross section is required over the length. Pultruded profiles reinforced with glass fibers (GFRP) present many advantages, including very high stiffness and strength to weight ratios, magnetic transparency, corrosion resistance, and an effective manufacturing process. For these features they can be qualified as non-corrosive, high mechanical strength and lightweight materials. In the last few years, they have been used in several different civil structures, acquiring a relevant role as primary bearing structural elements for applications such as cables, stands, truss members, footbridges, boardwalks, high voltage electricity poles, small buildings and emergency-oriented solutions...[edited by Author]