Externally post-tensioned steel tendons with GFRP longitudinal reinforcement in concrete beams: a brief review of materials, design rationale and serviceability

Abstract

Glass-fiber-reinforced polymer (GFRP) bars offer corrosion resistance and low mass but have an elastic modulus on the order of 30–50 GPa, far below that of steel. When used alone as longitudinal reinforcement, the low stiffness often leads to large crack widths and excessive deflection under service loads. This brief review examines a composite solution in which GFRP bars are combined with externally post-tensioned steel tendons. The post-tension introduces precompression to counter tensile stresses, while the GFRP bars provide durable tensile capacity after cracking. We summarize material roles, core design rationale for selecting tendon force levels and profiles, essential detailing at anchor zones and deviators, and long-term effects relevant to effective prestress retention. The review frames a compact workflow for practice and research: define serviceability targets, choose an external post-tension profile and force consistent with anchorage and compression checks, and verify crack width and deflection under sustained and variable loading. The combined system directly addresses the crack-control limitation of GFRP-only beams and provides a pragmatic path to improved service performance in aggressive environments.