Nonlaminated FRP Strap Elements for Reinforced Concrete, Timber, and Masonry Applications

Advances in material technology allow for the exploration of new structural forms and systems. In recent years, fiber-reinforced polymers (FRPs) have emerged as candidate materials for civil engineering applications, and the use of FRPs in construction has been an area of growing interest. Unidirectional high-strength FRPs are well-suited for use as tensioning elements, but anchorage details present a challenge. An alternative is to self-anchor the FRP tensioning element by winding thin layers of material around supports and then laminating all the layers together (a laminated strap) or by securing only the outermost layer to form a closed outer loop while the inner layers remain nonlaminated (a nonlaminated strap). Nonlaminated FRP straps have been found to have higher efficiencies than equivalent laminated straps, which is advantageous in high-tension applications. The suitability of nonlaminated FRP straps for use as unbonded tension elements provides scope for use in new construction and for the strengthening of existing structures. A review of nonlaminated carbon FRP strap system properties and applications in the context of reinforced concrete, timber, and masonry structures is presented.