Finite element prediction of interfacial stresses in structural members bonded with a thin plate

The strength or stiffness of a reinforced concrete (RC), metallic or timber member can be increased by bonding a thin FRP or steel plate to its external surface. In such plated members, debonding of the thin plate from the original member is often the controlling failure mode, and such debonding depends strongly on the interfacial stresses in the adhesive layer between the member and the plate. This paper is concerned with the prediction of these interfacial stresses using the finite element method. The paper is primarily focused on simply-supported straight plated beams subjected to a uniformly-distributed load as a widely studied benchmark case. Five different finite element modeling approaches based on different assumptions for the deformations of the three components of such a plated beam (beam, adhesive layer and plate) are described. The predictions of the five models are then compared with each other and with analytical solutions of different levels of sophistication. These comparisons illustrate clearly how each assumption affects the predicted interfacial stresses and identify the beam-spring-beam (B-S-B) model as a relatively simple yet sufficiently accurate model for practical use in predicting interfacial stresses and debonding failure in more complex structural members bonded with a thin plate. To illustrate the versatility and power of the B-S-B type model, interfacial stresses in two more complicated structures (a plated flat panel and a plated curved panel) obtained from the same type of model are presented and discussed. These results provide useful insight into the risk of debonding in such plated panels.