Behavior of CFRP-reinforced concrete columns at elevated temperatures

Abstract

Current design codes preclude FRP bars being used as main reinforcement in compression members because of the general recognition that the compressive strength of FRP bars is lower than their tensile strength and the lack of reliable data related to their performance at elevated temperatures. The present study evaluates the properties of CFRP bars as compression reinforcement in RC columns and investigates experimentally the structural performance after cooling of the columns reinforced with CFRP bars that were subjected to elevated temperatures. Twenty-four short columns specimens were fabricated considering the use of CFRP bars or steel bars as main reinforcement, the spacing of tie bar confinement and the exposure temperature (0, 150, 300 and 450 °C). The test members were subjected to concentric axial loading and the test results measured after cooling down to room temperature were compared with analytic results based on current standard for concrete columns. The investigation showed that, compared to the CFRP-reinforced columns let at room temperature, those exposed to elevated temperatures experienced compressive resistance that first improved by 3 % to 15.9 % at 150 °C, but degraded at higher temperatures by 7 % to 13.6 % at 300 °C, and by more than 50 % at 450 °C.