Performance Enhancement of Bridge Bracing Under Service and Extreme Loads

摘要

The purpose of this study was to develop and demonstrate the concept of retrofitting bridge brace elements with fiber reinforced composites in order to provide restraint against buckling. The advanced materials consisted of a combination of fiber reinforced polymer (FRP) composite pultruded sections and wet lay-up wraps, intended to be applied in the field. A selected number of prototype retrofit bracing specimens were constructed and tested using reverse cyclic loading, and the performance of these specimens was characterized by their compressive strength and their overall hysteretic behavior. The results of this exploratory study have shown that slender bracing members retrofitted with FRP sections show an improved level of performance. All retrofitted specimens showed an improved compressive strength in the linear elastic and plastic deformation range of the slender bracing member. The cyclic behavior exhibited only a marginal improvement, however, due to failure modes at the bolted connections of the brace. Further modification of the brace had marginally improved the cyclic performance. Despite the challenges associated with the connection failures of the retrofitted members, the demonstration has shown that the developed concept of applying fiber reinforced composites has a potential to effectively restrain slender bracing members from buckling and improve the compressive resistance. Further testing needs to be conducted to evaluate a more optimal implementation for resisting cyclic loads.