A parametric study on the effectiveness of the NSM technique for the flexural strengthening of continuous RC slabs

Recent experimental research has shown that Near Surface Mounted (NSM) technique has high potential to increase the load carrying capacity of continuous reinforced concrete (RC) slabs. This flexural strengthening technique is based on the installation of rectangular cross sectional carbon fibre reinforced polymer (CFRP) laminates into thin slits opened onto the top concrete cover at the intermediate supports and in the bottom concrete cover in the tensile zones. However, the linear-elastic behaviour of the CFRP laminates, and the possibility of occurring premature detachment of the concrete cover that includes these laminates can compromise, not only the flexural strengthening effectiveness of the NSM technique, but also the moment redistribution and the ductility performance of this type of structures. To evaluate the influence of the concrete strength class, the percentage of existing longitudinal tensile reinforcement and the percentage of CFRP on the strengthening effectiveness, moment redistribution capacity and ductility performance, a parametric study was carried out by executing material nonlinear analysis with a FEM-based computer program, which predictive performance was calibrated using the results of a previous experimental program.The study reported in this paper forms part of the research program "PrePAM -Pre-Fabricated Thin Panels Using Advanced Materials For Structural Rehabilitation" supported by FCT, PTDC/ECM/114511/2009. The authors also wish to acknowledge the support provided by the S&P and Casais. The first author further wishes to acknowledge the Erasmus Mobility Program between the University of Minho (Portugal) and the University of Ferrara (Italy), which rendered this international cooperation possible. The third author would like to acknowledge the PhD grant SFRH/BD/69818/2010 supported by FCT