Sustained Loading and Temperature Response of Fiber-Reinforced Polymer-Concrete Bond

One aspect of long-term behavior of the bond of fiber-reinforced polymer (FRP) and concrete bond has received relatively little attention in the literature: bond stress redistribution and remaining (residual) pulloff strength after sustained loading. The relevance of this missing information is directly related to the expected reliability of FRP-strengthened structures when subjected to sustained loading and elevated temperatures over their life span. The objective of this investigation was to evaluate the effects of sustained loading and temperature on the time-dependent distribution of strain in carbon FRP bonded to concrete and on the pulloff strength of the carbon FRP at room temperature after the sustained loading period. Pulloff specimens were used to evaluate stress distributions during sustained loading tests at loads below ultimate and during tests to ultimate after sustained loading. Under sustained loading, the presence of temperature and a bond-line flaw increased the bond stress transfer length between the FRP and the concrete substrate. However, although the presence of higher temperatures resulted in increased pulloff strength, this beneficial effect was eliminated in the presence of sustained loading.