Analytical Evaluation of RC Beams Strengthened with Near Surface Mounted CFRP Laminates

Abstract

Synopsis: To assess the strengthening efficiency of near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) laminates according to their groove depth and disposition, 4-point bending tests were performed on 4 specimens strengthened with NSM CFRP. A structural model for the finite element method (FEM) able to simulate accurately the experimental results was determined to analyze the strengthening efficiency of the NSM technique analytically. Applying the model, parametric analysis was performed considering the groove depth and spacing of CFRP laminates. Analytical study on the groove depth revealed the existence of a critical depth beyond which the increase of the ultimate load becomes imperceptible. In other words, this means that there exists a limit of strengthening efficiency where it remains in a definite level even if the groove depth is increased. Analytical results regard to the spacing of the CFRP laminates showed that comparatively smooth fluctuations of the ultimate load were produced by the variation of the spacing and the presence of an optimal spacing range for which relatively better strengthening efficiency can be obtained. Particularly, a spacing preventing the interference between adjacent CFRP laminates and the influence of the concrete cover at the edges as well as allowing the CFRP laminates to behave independently was derived. Using the analytical results, various strengthening schemes could be established with different numbers of CFRP laminates, groove depths and dispositions of the reinforcements for a determinate quantity of reinforcements.