Nonlinear Finite Element Analysis of Concrete Columns Confined by Carbon Fiber Reinforced Polymer Sheets

Abstract

In the past few years, the area of structural retrofitting became a hot topic for research. Providing additional confinement to reinforced concrete columns will result in increasing their axial load capacity. In this paper, the axial behavior of rectangular reinforced concrete columns confined by Fiber Reinforced Polymer (FRP) sheets is investigated using Nonlinear Finite Element Analysis (NLFEA). Experimental studies from the literature dealing with rectangular reinforced concrete columns wrapped with FRP sheets tested under uni-axial load are used to build and verify two Finite Element (FE) models. The proposed FE model showed good agreement with experimental results. The models were used to conduct a parametric study to investigate the effect of FRP thickness, FRP sheets spacing, and core concrete strength on the behavior of both plain and reinforced concrete columns. Furthermore, a new empirical model to predict the behavior of confined rectangular concrete columns is developed. The results of the parametric study showed that the effect of FRP confinement decreases with the increase of the compressive strength of concrete used. Increasing the number of layers (i.e., thickness) will enhance the strength; however, after 4 layers there is no significant improvement in strength gain. Large spacing between FRP sheets in partial confining configuration results in nonsymmetrical damage in concrete.