Development of a Novel Integrated Strengthening and Sensing Methodology for Steel Structures Using CNT-Based Composites

Strengthening of deteriorating structural members by fiber-reinforced polymers (FRPs) is an increasingly common and validated technique; however, concerns over means to evaluate the long-term durability of these retrofits exist. This paper explores a novel approach to overcome this concern through the use of a novel self-sensing composite material. Specifically, the objective of this paper is to provide a proof of concept for an integrated strengthening and sensing methodology for structural steel members achieved via infusing more-traditional composites with carbon nanotubes (CNTs). To assess the strengthening and sensing capabilities of the CNT-based composite, a set of unidirectional tensile tests were conducted. The experimental results show stiffness increases and strain reductions due to the application of the CNT-based sensing composites that were in close agreement with both analytical and finite-element models. The sensing aspect was also validated by a corresponding linear change in resistance of the CNT-based sensor with increasing load up to the point at which debonding of the adhesive layer occurred. The nanotube sensing layer is able to capture the strain in the member as well as the onset and extension of interfacial debonding. (C) 2016 American Society of Civil Engineers.