Nonlinear finite-element analysis for the behavior prediction and strut efficiency factor of GFRP-reinforced concrete deep beams

The recent experimental results and proposed strut-and-tie model (STM) for deep beams reinforced entirely with glass-fiber-reinforced polymer (GFRP) bars have suggested that a comprehensive examination is required to improve the strut efficiency factor and its affecting parameters. This study uses nonlinear finite-element analysis (FEA) to perform an in-depth investigation. FEA response was compared against the experimental results in terms of crack patterns, failure modes, strains in reinforcement and concrete, and load-deflection relationships. The results show that the simulation procedures employed were stable and compliant, and that they provided reasonably accurate simulations of the behavior. FEA was used to confirm some hypotheses associated with the experimental investigations. A comprehensive parametric study was conducted to investigate the effect of web reinforcement and loading-plate size on the strut efficiency factor. It was shown that vertical web reinforcement has no clear effect on the strength, but it is required for crack control. On the other hand, horizontal web reinforcement should be accompanied with vertical reinforcement. Loading-plate size showed a clear effect on the deep-beam strength. Based on the numerical simulation results, a modification to a recently proposed STM is suggested. The modified STM was compared to available STMs in design codes and provisions, yielding better correlation with experimental results.