The Embedded Through-Section (ETS) technique is a promising technique for the shear strengthening of\ud existing (RC) elements. According to this technique, holes are drilled through the beam section, and bars\ud of steel or FRP material are introduced into these holes and bonded to the concrete with adhesive materials.\ud An experimental program was carried out with RC T-cross section beams strengthened in shear\ud using the ETS steel bars and ETS CFRP rods. The research is focused on the evaluation of the ETS efficiency\ud on beams with different percentage of existing internal transverse reinforcement (qsw = 0.0%, qsw = 0.1%\ud and qsw = 0.17%). The effectiveness of different ETS strengthening configurations was also investigated.\ud The good bond between the strengthening ETS bars and the surrounding concrete allowed the yield initiation\ud of the ETS steel bars and the attainment of high tensile strains in the ETS CFRP rods, leading to\ud significant increase of shear capacity, whose level was strongly influenced by the inclination of the ETS\ud bars and the percentage of internal transverse reinforcement

a b s t r a c tA new shear strengthening technique, designated as embedded through section (ETS), has been developed to retrofit existing reinforced concrete (RC) elements. This technique calls for holes to be drilled through the beam section; then bars of steel or FRP materials are introduced into these holes and bonded with adhesives to the surrounding concrete. When concrete cover has not the bond and strength requisites to guarantee a strengthening effectiveness for the Externally Bonded and Near Surface Mounted techniques, ETS strategy can be a competitive alternative since it mobilizes the beam's concrete core which is, generally, free of damage. To explore the potentialities of the ETS technique for the shear strengthening of RC beams, an experimental program was carried out, composed of RC T-cross section beams shear strengthened by using steel bars. The influence on the shear strengthening efficiency of the inclination and shear strengthening ratio of ETS configurations was evaluated; the study also examined the interaction of ETS bars and existing steel stirrups. An increase of shear capacity up to 109% and 136% in the beams with and without internal stirrups, respectively, was obtained. Inclined ETS bars provided higher increase of shear resistance than vertical ones.

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.

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Reinforced concrete (RC) structures such as concrete box-girder highway bridges may suffer fatigue damage due to cyclic loads. Externally bonded (EB) carbon fibre reinforced polymer (CFRP) strips can be used to increase the fatigue (and static) load bearing capacity of such elements and to increase the service life of the elements. The EB CFRP strips under the asphalt layer can reach elevated temperatures of up to 50°C during summer when the asphalt is directly exposed to solar radiation. Therefore, in this study, the fatigue behaviour at an elevated temperature of RC slabs strengthened with EB CFRP strips is evaluated. The focus is on the strengthening of lateral cantilevers of deck slabs of concrete box-girder highway bridges. The fatigue behaviour of RC elements is a complex phenomenon that is influenced by many parameters such as the maximum load, stress oscillation level on the longitudinal steel reinforcement, shear span-to-depth ratio, and quality of concrete. This phenomenon becomes even more complicated when elevated temperatures are considered. Majority of the existing experimental works on fatigue behaviour of EB-strengthened RC structures showed that the typical fatigue failure at room temperature is caused by fatigue failure of the longitudinal steel reinforcement followed by strip debonding. In this study, it was investigated if a different type of failure can be observed at elevated temperatures owing to the changes in epoxy properties.