GFRP-sheet strengthened RC beams after seawater immersion under monotonic and fatigue loads

Abstract

This study aims to analyse glass fibre reinforced polymer (GFRP) reinforcement on reinforced concrete beams under fatigue and monotonic loads influenced by sea water. The research was conducted in the laboratory on flexural concrete beams with the quality of f´c= 25 MPa. One normal concrete flexural beam (BN) with repetitive load was without seawater and no reinforcement. One flexural beam was without sea water immersion but with GFRP-reinforcement. Another flexural beam reinforced by GFRP sheets is immersed in a pond containing seawater with time variations up to 12 months. The test was performed with a fatigue load of 1.25 Hz frequency to failure. The results showed an increase in capacity due to 58.3% for GFRP-reinforcement. There is a decrease in the capacity of GFRP sheet influenced by seawater immersion. The same trend with the decrease in ductility occurred in the flexural beam to 14% due to seawater immersion. Maximum beam failure repetition occurred at 1,230,000 cycles on beam with reinforcement (BF). The failure occurring in the flexural beam was preceded by the failure of the attachment between the concrete and the GFRP sheet at the load centre (mid of span) slowly to the support until failure (debonding) initialized. The GFRP-S bonding capacity to the concrete skin has decreased in 12 months by 15%. Therefore, there is a significant effect of decreasing strength due to fatigue loads and seawater immersion.