Anchored spiral jacketing: a novel approach to improve the elevated temperature resistance of FRP-confined concrete columns

The fire and thermal performance of fiber-reinforced polymer (FRP) materials and structures is a significant challenge in the context of rehabilitating civil structures. To address this problem, this paper proposes a novel strengthening scheme, known as anchored spiral jacketing (ASJ), to improve the suboptimal thermal performance of FRP-strengthened concrete columns. An experimental program is presented to examine the compressive behavior of concrete cylinders wrapped with spiral unidirectional FRP integrated with a mechanical anchoring system. This concept is based on using mechanical anchoring technology to prevent FRP-concrete debonding at elevated temperatures, thereby improving the thermal performance of FRP-confined concrete columns. The behavior and effectiveness of the confining system are tested after exposure to temperatures up to 380°C under steady-state conditions. It is demonstrated that this innovative ASJ strengthening scheme can provide the desired passive confinement along with an epoxy or inorganic matrix at elevated temperatures. This technique also emphasizes the idea of protecting only critical locations of the columns, significantly reducing the cost of passive fire protection (PFP), because using PFP is essential for such systems due to the thermal limitations of the materials involved.