STRENGTHENING OF RC SLABS WITH PRESTRESSED AND NON-PRESTRESSED NSM CFRP STRIPS

This paper presents the results of an experimental tests carried out on reinforced concrete (RC) slabs strengthened in flexure with prestressed near surface mounted (NSM) carbon fiber reinforced polymer (CFRP) strips. The main aim of the test was to define effectiveness of strengthening with narrow CFRP strips glued into slits made in a concrete cover in aspect of an influence of an internal steel reinforcement ratio. In order to improve serviceability limit state conditions of pre-tensioning of the NSM reinforcement has been proposed. According to the authors knowledge a number of studies on the pre-tensioned NSM FRPs is quite small. Until now only few laboratories all over the world have undertaken the subject of flexural strengthening with pre-tensioned strips and obtained very promising results. The innovation of this study is a novel prestressing device adapted to tension narrow CFRP strips proposed by the authors. The experimental program contained two RC slabs reinforced with different internal steel reinforcements. Obtained results indicated high effectiveness of this technique with flexural enhancement of 73 and 134% compared to non-strengthened specimens respectively with higher and lower steel reinforcement ratio. Introducing pre-tensioning of the CFRP strips upgrades the service conditions with decrease of existing deflections and reduction of crack width. Outcomes of the study presented herein motivated authors for further research and developed novel experimental program based on preloaded specimens to analyse the effect of prestressing on service conditions.