Evaluation of Kinetic and Viscosity Based Parameters for Fiber Reinforced Composite Rebars at Elevated Temperatures: A Parametric Study

Abstract

Fiber reinforced polymer (FRP) composites are high performing materials and offer a wide range of applications. This has led to an increased use of FRP rebars in new construction with concrete as an alternative to steel in buildings. In building applications, FRP rebars need to conform to fire endurance ratings. Unfortunately, there has been very limited effort for understanding the fire endurance of FRP rebars in concrete structures. This limited effort is only available for glass conversion (kinetic parameter) in the glassy state. There is none available for decomposed state (kinetic parameter) and viscosity based parameters influencing the fire endurance of FRP rebars. Moreover, understanding the fire endurance of FRP composite rebars through the standard fire tests is expensive and time consuming. Therefore, this research makes an attempt to develop models that incorporate various transition states of FRP rebars at elevated temperatures to study kinetic and viscosity based parameters. The kinetic parameter in the glassy state is compared with a limitedly available approach in literature. In addition, a parametric study involving decomposed state, and viscosity based parameters in rubbery and leathery states is also carried out to provide some understanding of rebars endurance in fire. A basic understanding is obtained. In order to highlight basic implications on design approaches, a design model is also developed that incorporates the useful transition states in predicting the creep behavior of FRP reinforced concrete structures. This model can serve as a first step in the future design approaches for the construction industry in an economical way.