Temperature effect on the bond behaviour of a transversely compressed mechanical anchorage system

Abstract

Nowadays the strengthening of reinforced concrete (RC) structures using FRP composites is a viable reality, consolidated by many studies and practical applications. One of the most common methods used to apply the FRP is the externally bonded reinforcement (EBR) technique. However, the development of stresses at the anchorage zones of the EBR-FRP composite might cause premature debonding. To delay or avoid premature failure, mechanical systems were successfully developed. This works aims to assess the performance of a mechanical system: the metallic anchorage plate commercially distributed by S&P Clever Reinforcement Company, typically used for pre-stressed EBR-FRP systems. For that purpose, an experimental program composed by fourteen concrete blocks (200500800 mm3) strengthened with EBR-CFRP laminates mechanically anchored to the concrete was executed. Each metallic plate was fixed to the concrete element through six prestressed bolts, creating a confinement stresses in the anchorage region. All specimens were tested up to failure under two types of pull-out configurations: the steady-state temperature, where the laminate was pulled from the block with increasing force and constant temperature (20 ºC, 60 ºC and 80 ºC); and the transient temperature, where the laminate was pulled with constant force (0.5% and 0.6% of strain) and the temperature was gradually increased. Besides temperature and test configuration, the influence of the laminate width and level of transverse compression in the metallic plate were also studied. Results showed that the debonding process and failure are highly influenced by the temperature, laminate width and confinement level.