Abstract
Despite the clear cost, ease of installation, and construction schedule advantages of confinement of concrete structural elements with fibre-reinforced polymers (FRPs) for strength and deformability enhancement, concerns as to their performance at elevated temperature, or in fire, remain. The results of a series of elevated temperature experiments on FRP and textile reinforced mortar (TRM) strengthening systems for confinement of circular concrete columns are presented. The behaviour and effectiveness of the respective confining systems is studied up to temperatures of 400 °C. A total of 24 concrete cylinders were wrapped in the hoop direction with different amounts of FRP or TRM, heated to steady-state temperatures between 20 and 400 °C, and loaded to failure in concentric axial compression under a steady-state thermal regime. The results indicate that the effectiveness of the FRP confining system bonded with epoxy decreased considerably, but did not vanish, with increasing temperatures, in particular within the region of the glass transition temperature of the epoxy resin/adhesive. Conversely, the TRM confining system, bonded with inorganic mortar rather than epoxy, demonstrated superior performance than the FRP confining system at 400 °C as compared against tests performed at ambient temperature.
Highlights
Introduction and backgroundA popular application of fibre reinforced polymers (FRPs) is strengthening concrete columns by confinement with FRP in the hoop direction [1]
In an effort to develop strengthening systems with enhanced performance at elevated temperatures, this paper investigates, for the first time, the performance and effectiveness of both FRP and textile reinforced mortar (TRM) confining materials of concrete at elevated temperatures, such as would be experienced during a fire, when the confining system is active under sustained load; this was done by testing concrete cylinders with different amounts of FRP or TRM confinement at various temperatures
Considerable loss of effectiveness of the FRP wrap system occurred at temperatures exceeding the Tg of the epoxy adhesive used
Summary
A popular application of fibre reinforced polymers (FRPs) is strengthening concrete columns by confinement with FRP in the hoop direction [1]. In an effort to develop strengthening systems with enhanced performance at elevated temperatures, this paper investigates, for the first time, the performance and effectiveness of both FRP and TRM confining materials of concrete at elevated temperatures, such as would be experienced during a fire, when the confining system is active under sustained load; this was done by testing concrete cylinders with different amounts of FRP or TRM confinement at various temperatures. The investigated parameters considered include, the use of inorganic mortar versus resin-based matrix material for the textile reinforcement (TRM vs FRP), the number of textile layers (one or three) and the increase of temperature (from ambient to 400 °C, with the tests performed under a steady-state thermal regime at elevated temperature).
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