Finite elemet analysis of low-strength cylinder concrete element strengthened with FRP composites.

In this study, concrete elements with standard cylinder dimensions, with carbon and glass fiber reinforced polymer (CFRP and GFRP) composites were analyzed under the effect of axial load by finite element method. The cylindrical concrete samples have an average compressive strength of 6.7, 11 and 20.8 MPa. The axial force results of outer strengthened concrete with single direction transverse CFRP or GFRP were used in this study. The behavior of CFRP and GFRP reinforced concrete was modeled by Finite Element Method (FEM) program ABAQUS. The desired parameters for modeling in ABAQUS program has been obtained from experimental studies and some basic formulas commonly used in literature and modeling. Finite element model of low strength concrete was formed by determining the necessary parameters for modeling. As model parameters such as the size and shape of the mesh and the angle of dilution are significantly affect the concrete behavior, the suitable parameters for low strength concrete were determined first. After validating concrete model experimental results, analyzes were obtained for strengthened concrete with fiber reinforced polymers. FRP composites are defined as shell elements in finite element model and connected to concrete side surface. Parametric study was performed by changing the concrete strength and number of FRP layer in FEM model. In order to calculate the compressive strength and deformations of FRP strengthened concrete, the formulas in the literature were analyzed. According to the obtained results, behaviour of concrete samples and behaviour of strengthened concrete by FRP composites are confirmed with a good convergence using the proposed finite element model. Suitable model parameters have been determined for low strength concrete. By using the results obtained from FEM analyzes and results of the parametric study, formulas for stress and strain model are developed to calculate the compressive strengths and deformations more accurately for FRP retrofitted concrete with low compressive strength.