Experimental Study and Numerical Modelling on Flexural and Shear Strengthening of RC Beam with Prestressed FRP Bars
Authors: Pradhan Spandan Swarup 
Published: May 2023

Abstract: The most prevalent and widely used building material in the world is reinforced concrete. The primary building material for the majority of constructions, including buildings, bridges, etc., is reinforced concrete. Because of various factors, some of these buildings or portions of them are failing to perform as designed. The best solution to increase the load carrying capacity and extend the useful life of these inadequate structures is to strengthen them because replacing them would need significant investments and not be an appealing alternative. Even though the effectiveness of other techniques is widely accepted,a new effective and promising technique of strengthening civil engineering structures externally is gaining popularity, where fibre-reinforced polymer (FRP) is used. One of the most popular strengthening methods recently is the use of carbon fibre reinforced polymer (CFRP) to strengthen reinforced concrete beams. It provides a desirable way to improve the shear and flexural strengths of RC beams. The manner in which these composites are bonded to the beam has a significant impact on the behaviour of reinforced concrete beams in shear and flexure. The purpose of this study was to present a three-dimensional nonlinear finite element analysis (FEA) of a reinforced concrete beam (RC beam) reinforced by prestressed carbon fibre plate (CFRP plate). While there are many commercial programmes available for three-dimensional nonlinear FEA, each one has a unique ability to represent complex behaviour of composite materials, such as RC beams strengthened with prestressed CFRP plate and the contact interaction. Because of its reputation for accuracy in simulating the behaviour of a range of materials, including concrete, and its potent contact algorithms, the ABAQUS finite element programme was chosen for this work. Steel reinforcements were modelled as elastic- perfectly plastic materials, while concrete was studied using the concrete damage plasticity (CDP) constitutive model. The CFRP plate was modelled as an entirely elastic substance that breaks under the highest tensile strain. Concrete and steel reinforcement were considered to have a perfect connection, and the behaviour of concrete and CFRP plate was represented using a contact model. The FEA's findings were verified against experiment findings that were published in the literature. In terms of load-deflection behaviour, crack patterns, and mode of failure, the results were compared. The proposed FEA model was able to accurately simulate the behaviour of RC beams strengthened with prestressed CFRP plate based on the validation. To find out the impact of the thickness, width, and length of the CFRP plate, as well as the prestressing levels and steel grades, a parametric research was done. In particular, the strength of the RC beam for the ultimate load was shown to be increased by increasing prestressing of the CFRP plate. However, as prestressing increased, the fracture of the CFRP plate altered the mechanism of failure, preventing the ultimate load from increasing further. The use of higher grade steel improved the ability to support additional weight. Although the general load carrying capability of the CFRP plate was increased by lengthening the plate, it was discovered that strengthening RC beams by 25% of their shear span was sufficient and cost- effective. The load-deflection curve, failure modes, and crack patterns from the experiments are fairly reflected in the FE model.