A linear viscoelastic model for interfacial long-term behavior of FRP–concrete interface

The long-term serviceability of FRP-strengthened structures is a huge concern because of the lack of long-term performance data and suitable models, which can adequately represent this performance. This study aims at presenting a viscoelastic model to describe the long-term behavior of the adhesive layer bonding FRP sheet to concrete, the FRP–concrete interface. The proposed model is an important modification and an extension of the generalized Maxwell constitutive model. The parameters of the proposed model have been investigated based on the results from a two-dimensional FE analysis presented by the 1990 European CEB-FIP code. Afterward, the validity of the proposed model and its parameters was confirmed by previous experimental results. Subsequently, it is used to study the design parameters that may affect the creep of adhesive bonding FRP sheets to concrete under service loads.