Material-Efficient Selection of Externally Bonded Fiber-Reinforced Polymer Composites for RC Shear Strengthening Using a Literature-Based Database and Break-Even Criteria

Fiber-reinforced polymer (FRP) shear strengthening is generally selected on the basis of structural capacity, whereas the efficiency with which installed material contributes to shear resistance has received little quantitative attention. This study develops a literature-based material-efficiency framework from a database of 359 published tests compiled from 43 experimental programs covering carbon, glass, aramid, basalt, and PET-FRP systems. Material efficiency (ME) was defined as the experimentally attributed FRP shear contribution per unit mass of installed composite sheet. ME varied approximately 30-fold. Median ME was 303 kN·m·kg−1 for CFRP and 38 kN·m·kg−1 for GFRP, giving a CFRP:GFRP median-efficiency ratio of 8.1 (program-clustered 95% CI: 3.8–18.3; 2.8–21.3 when thickness-convention and density uncertainty were also propagated). This observational, database-level ratio, which is an association rather than a causal material effect, was translated into a sheet-level cradle-to-gate greenhouse-gas break-even screening criterion. A response-surface model based on XGBoost achieved random ten-fold out-of-fold R2 = 0.802, decreasing to 0.526 under program-grouped validation and 0.394 under leave-one-program-out validation; most of this loss reflected program-level offsets. Member geometry and transverse reinforcement carried greater predictive importance for the attributed FRP contribution than FRP-sheet properties under both random and program-grouped validation. Material efficiency generally decreased with increasing installed sheet rigidity, consistent with diminishing structural returns from additional FRP material. The framework compares code-compliant alternatives that satisfy the required FRP shear contribution, using material efficiency to identify lower-material-demand solutions before project-specific environmental and economic evaluation.