An innovative prestressing system of prestressed carbon fiber sheets for strengthening RC beams under flexure

Abstract

An innovative prestressing system was developed in this study, which can effectively anchor the prestressed carbon fiber sheets as well as conveniently apply prestress to the carbon fiber sheets. Tensioning tests of the carbon fiber sheet-anchor assemblies were first conducted to verify the anchorage behavior of anchors. Then this prestressing system was used for strengthening reinforced concrete (RC) beams to further verify its feasibility and investigate the effect of the impregnation and curing conditions of the carbon fiber sheets on the flexural strengthening efficiency. The results indicated that the tested ultimate capacity of the carbon fiber sheet-anchor assembly reached 72.1∼97.9% of the theoretical ultimate capacity of the carbon fiber sheet based on different impregnation and curing conditions. The concrete crushing failure and rupture failure of prestressed carbon fiber sheets occurred in the strengthened RC beams. The cracking and yielding loads of the RC beams with prestressed sheets were increased by 56.7∼68.5% and 21.7∼30%, respectively, while those with non-prestressed sheets were increased by 27.3% and 13.7%, respectively. The ultimate load was significantly affected by the impregnation and curing conditions. The prestressed carbon fiber sheets with the uncured full impregnation condition were not superior to the non-prestressed sheets in terms of the ultimate load, whereas the cured full impregnation and partial impregnation conditions were more effective than the uncured full impregnation condition. Finally, theoretical equations were used to calculate the cracking, yielding, and ultimate moments of RC beams strengthened with prestressed carbon fiber sheets.