A design-oriented solution for FRP-to-substrate bonded joints with a transversely compressed mechanical end anchorage

The strengthening of damaged concrete, steel or timber beams with carbon fibre-reinforced polymers (CFRP) has increased continuously. Usually, the CFRP composite is externally bonded (EB) to the soffit of the beam, and the adhesion between both surfaces is critical for the success of this strengthening technique. The FRP-to-substrate interfaces are prone to debond prematurely, so to delay or prevent this, additional anchorages are used. However, the performance of mechanically anchored FRP-to-substrate joints remains unclear due to the high diversity of existing anchorage systems. To mitigate this gap, an analytical model is developed to simulate the influence of a transversely compressed mechanical end anchorage on CFRP-to-substrate joints. The analytical model replaces the mechanical end anchorage with a nonlinear spring. A series of different generated cases is considered and simulated by the analytical model and validated by the Finite Element Method (FEM). Experimental data found in the literature are also simulated using the analytical model. The results showed that the transversely compressed end anchorage is efficient when a long anchorage is used rather than a shorter one. The analytical model can also predict the nonlinear load increment of the anchored bonded joints as experimentally reported in the literature. © 2025 The Author(s).