Title: Nonlinear Finite Element Modeling of Continuous RC Beams Strengthened with Near Surface Mounted FRP Bars
Author(s): Majid M.A. Kadhim, Akram Jawdhari, and Mohammed Altaee
Publication: Symposium Paper
Appears on pages(s): 327-346
Keywords: bond-slip, concrete, continuous beams, FRP, finite element, near surface mounted, numerical analysis, retrofit
One of the successful techniques utilizing fiber reinforced polymer (FRP) reinforcement in concrete retrofit is by embedding bars or strips in pre-cut grooves, forming what is collectively known as near surface mounted (NSM). While a great deal of research and attention has been devoted to evaluating NSM-FRP in retrofitting statically determinate members, limited work is given to indeterminate structures. In this study, a three-dimensional finite element (FE) model is developed to evaluate the behavior of continuously reinforced concrete (RC) beams strengthened in the negative and positive moment regions with NSM-FRP bars. The model included robust features such as concrete damage plasticity (CDP), FRP failure, and slipping and debonding of FRP bars and was calibrated with tests on 6 m long two-span continuous beams. It was able to predict load-deflection and load strain responses, for different FRP reinforcement ratios and lengths, with a maximum 8% deviation for the loads at steel yielding and at ultimate. Failures observed in tests, namely, concrete cover separation, cracking and crushing, and FRP bar debonding from adhesive, at both the hogging and sagging regions, were also reasonably simulated. The model will be used next in examining behavioral aspects in detail, evaluating the effects of multiple geometric and material parameters, and assisting in developing design recommendations for NSM FRP-strengthened continuous RC beams.