Contribution à l’étude de comportement des consoles courtes en béton armé renforcées ou réparées par matériaux composites.

Abstract

The present research provides a comprehensive investigation of the performance of reinforced concrete (RC) corbels that have been reinforced with carbon fiber reinforced polymer (CFRP) under different loading conditions. The study combines both experimental and numerical analysis to investigate the impact of monotonic, cyclic, and seismic loading on the behavior of RC corbels strengthened with CFRP. The research examines the crucial factors that influence the behavior of corbels, such as the number of CFRP layers, the compressive strength of the concrete, and the presence of horizontal reinforcing stirrups. Numerical results obtained under monotonic loading show that augmenting the thickness of CFRP layers has a substantial impact on both the shear strength and stiffness of the corbels, resulting in a 123% increase, although it may reduce their ductility. Increased concrete compressive strength significantly enhances the loadbearing capacity and stiffness. Incorporating horizontal stirrups significantly improves the shear capacity, ductility, and distribution of cracks. Under cyclic loading, the experimental analysis shows distinct phases of elastic and plastic deformation in both the steel reinforcement and CFRP strips. The behavior of the RC corbel exhibit elastic cycles in the beginning, followed by substantial reversible deformation and eventual pinching effects caused by localized damage. The main cause of failure in CFRP-strengthened corbels is the crushing of diagonal concrete struts and the delamination of CFRP strips. Abaqus numerical models effectively capture the behavior and and failure mechanisms of reinforced concrete corbels subjected to both monotonic and cyclic loading. Nevertheless, the models have a tendency to overestimate the amount of deformation that occurs under cyclic loading. This might be attributed to the difficulties in accurately predicting shear deformation and the slippage of reinforcement. Furthermore, the numerical analysis conducted under both reversed and non-reversed cyclic loading clearly shows that the use of CFRP strengthening greatly enhances the cyclic performance, load carrying capacity, and stiffness of RC corbels when compared to unstrengthened specimens, especially when the shear span-to-effective depth ratios are optimized, increasing the number of CFRP layers, increasing the concrete compressive strength, and including horizontal reinforcement stirrups. Moreover, the study determines that the impacts of factors such as the quantity of CFRP layers, the compressive strength of concrete, and the presence of horizontal reinforcing stirrups remain comparable in both monotonic and cyclic loading conditions. Nevertheless, CFRP strengthening exhibits much greater efficiency when subjected to monotonic loading compared to cyclic loading. The numerical simulation findings demonstrate that CFRP strengthening typically improves the seismic performance of RC corbels. However, the efficiency of this strengthening method differs depending on the specific seismic factors and reinforcement configurations. The use of both vertically and horizontally wrapped and combined CFRP strips yielded optimal outcomes under certain earthquake conditions. Nevertheless, inadequately designed CFRP strengthening techniques could compromise the performance of RC corbels, emphasizing the need for designing these reinforcements according to precise seismic characteristics. In addition, the external strengthening's efficiency is less noticeable when subjected to seismic excitation compared to its performance under monotonic and cyclic loading.