A Systematic Review of Anchored and Unanchored EB-FRP Systems for Tension Strengthening of Concrete Structures

Abstract

Abstract

Externally bonded fiber-reinforced polymer (EB-FRP) systems have been extensively investigated for tension strengthening concrete structures. Interpretation of the available evidence remains challenging because experimental methods, specimen scales, material systems, anchorage configurations, and reporting practices vary substantially across the literature. This systematic review synthesized 174 peer-reviewed studies published between 1994 and 2026, comprising 3908 experimental test results and 42 analytical formulations addressing unanchored and anchored EB-FRP systems. Review findings showed that bond performance in unanchored systems is governed primarily by FRP stiffness, bond geometry, concrete properties, adhesive behavior, surface preparation, and environmental exposure. These parameters influence bond capacity, debonding strain, effective bond length, and failure mode. Anchored configurations consistently enhanced force transfer, delayed premature debonding, and improved load-carrying capacity relative to unanchored systems. Unanchored systems dominated the available evidence base with 3162 test results, whereas only 96 multi-anchor system tests were identified, highlighting limited understanding of anchor interaction and load redistribution mechanisms. CFRP represented the dominant material system, while substantially fewer studies investigated GFRP, BFRP, and AFRP systems. Existing strength models generally captured specific failure mechanisms within their calibration ranges but demonstrated limited transferability across different geometries, loading conditions, anchorage configurations, and environmental conditions. Limited evidence remains available for scale transfer, durability degradation, anchor strip interaction, and multi-anchor load sharing under field-representative conditions. Future research should focus on standardized benchmarking procedures, large-scale validation programs, durability-informed design approaches, experimentally validated numerical modeling, and unified design provisions for EB-FRP strengthening systems.