Nonlinear Analysis of Reinforced Concrete Beams Strengthened by Prestressed CFRP Sheets under Static Loads

Abstract

A nonlinear finite element study has been conducted to evaluate the efficiency of the technique of strengthening reinforced concrete beams under static loads. No time-dependent effects (creep and shrinkage... etc.) are considered in this work. This concept is based on prestressing of CFRP sheets. In this research program, four reinforced concrete beams were tested to investigate the feasibility of such concept for flexural strengthening. One of the beams was retrofitted with non-prestressed CFRP sheet which was used as the control beam. The rest were retrofitted with prestressed CFRP sheet with three levels of prestressing. The static load was applied at the instant of full prestress load application. Prestress losses were ignored here. CFRP sheets have been simulated using two types of element (SHELL41 and LINK8). Prestressing effects have been represented using two models; the application as axial load and initial axial strain. The results showed that there is a good enhancement in performance of the beams strengthened using the prestressing technique in terms of the cracking loads and deflection occurs at such level of loading. The application of prestressing forces of 9 kN, 16 kN and 22 kN, was found to increase the cracking load by 57%, 106% and 170%, respectively.