Nonlinear Finite Element Analysis of RC Beams Strengthened with Steel Fiber-Reinforced Concrete (SFRC) overlays

Abstract

The behavior of RC beams strengthened with steel fiber-reinforced concrete (SFRC) overlays was studied by Finite Element Analysis software ANSYS. Four beams, three of them were experimentally tested in previous research were considered. The first beam was considered as a control beam made of ordinary concrete, while the second one was modeled using SFRC material properties. The third one is a beam with two material properties, the original part, which is made of ordinary concrete that needed to be strengthened and the overlay, which is made of SFRC material. The fourth beam is the same as the third one, except the SFRC, part is at bottom as an underlay. To ensure a monolithical behavior, a weld-bond strengthening techniques were used. Ordinary concrete, as well, Steel Fiber-Reinforced Concrete was modeled using the multilinear isotropic hardening constants where it is assumed to have a linear behavior up to 30% of compressive strength. Afterwards, a multilinear stress-strain curve was defined. For reinforcing steel, a linear elastic-perfect plastic material model was used. Steel fiber reinforced concrete was modeled using two methods, the smeared model and the discrete model. The results obtained by FEA showed a good agreement with those obtained by an experimental program. For beams strengthened with SFRC overlays, results indicated a remarkable improvement in the load carrying capacity and ductility by 15% and 8%, respectively. While for beams strengthened with SFRC underlays, results indicated an improvement in both load carrying capacity and overall ductility by about 24% and 162%, respectively. In both cases, the welding of stirrups prevents diagonal cracks from proliferating into the compression zone. A parametric study indicated an improvement in load carrying capacity with higher SFRC compressive strength values, while increasing the fraction volumes in the SFRC overlay did not affect the results significantly. The results of this research indicated that it is possible to predict the behavior of beams strengthened with SFRC overlays and underlays using FEA without the need for costly experimental testing. While the importance of this research comes from the fact that if the use of numerical analysis can predict the behavior of beams with SFRC overlays, this will help researchers predicting the behavior of beams with different configurations without the need to go through the lengthy experimental programs.