TRM-to-concrete interface bond without anchors: Combined experimental, analytical, and numerical modeling approach

Abstract

Textile reinforced mortar (TRM) systems have emerged as an effective alternative to conventional FRP strengthening solutions due to their compatibility with concrete substrates and favorable performance under adverse environmental conditions. Experimental data on the combined effects of strip width, bond length, and concrete compressive strength on TRM–concrete bond behavior, however, remain limited. In this study, an experimental program comprising 12 specimens was conducted to investigate the bond–slip response of TRM systems bonded to concrete substrates with two compressive strength classes (15 and 30 MPa), two strip widths (50 and 100 mm), and three bond lengths (150, 300, and 450 mm). The results show that increasing the TRM strip width from 50 to 100 mm significantly enhanced the maximum load capacity by up to 61% in 15 MPa concrete and up to 50% in 30 MPa concrete, depending on the bond length. Increasing the concrete compressive strength from 15 to 30 MPa resulted in maximum load increases of up to 32%, accompanied by a pronounced improvement in stiffness, which increased by over 100% for specimens with 100 mm strip width and 300 mm bond length. Energy absorption capacity was strongly influenced by both strip width and concrete strength. For specimens with 100 mm strip width and 300 mm bond length, increasing the concrete strength from 15 to 30 MPa led to a 61% increase in energy dissipation, indicating improved damage control at the TRM–concrete interface. While increasing the bond length significantly improved load capacity and energy dissipation, diminishing gains were observed beyond a bond length of 300 mm, suggesting the presence of an effective bond length for TRM systems.Based on the experimental findings, empirical regression models were developed to describe the bond–slip behavior and to define the parameters required for cohesive zone modeling of the TRM–concrete interface. The presented results provide quantitative insights that can support experimental interpretation and numerical modeling of TRM-strengthened reinforced concrete elements.