Renforcement des poutres en béton armé par torons d’acier en utilisant la technique NSM

Abstract

The main objective of this work is to study the performance of prestressing steel (AP) bars as reinforcements in the reinforced concrete (RC) elements strengthened by the near-surface mounted method (NSM). First, some mechanical properties of smooth prestressing steel bars (AP) and then, in order to improve the mechanical adhesion of these bars, the surface of the smooth AP bars is modified by a sand coating. Second, direct pull-out tests are performed in order to study the bond performance between PS reinforcement and concrete. The influences of groove sizes and PS surface conditions (smooth and sand coated) are evaluated. The results show that the sand coated AP (AP-Sc) reinforcement has the best adhesion behavior compared with the smooth bar. Afterwards, the global behaviour of beams strengthened using this technique (AP-Sc-NSM) and subjected to a four-point bending is investigated, we perform an important study of several parameters. A comparison between the experimental results and analytical calculations of the main limit states is performed. The experimental results indicate that strengthening concrete structural members with the Near Surface Mounted reinforcement technique using the sand coated AP (AP-Sc) reinforcement gives very satisfactory results.