Structural Performance of Concrete-Filled GFRP Tube Slender Columns in Ambient and Standard Fire Conditions.

Concrete-filled glass fiber-reinforced polymer (GFRP) tube (CFFT) columns benefit from significant concrete confinement effects that enhance its structural performance compared to conventional internally reinforced concrete members. CFFTs are currently utilized mostly for exterior applications, as the uncertainty of their performance in fire situations has slowed their adaptation in buildings. To address this uncertainty, a series of ambient temperature and fire tests were conducted on CFFT columns with slenderness ratios (KL/r) ranging from 6.9 to 62.4, using GFRP tubes of 113 mm outer diameter and 3.8 mm wall thickness. The strength increase provided by the GFRP tubes as compared to plain concrete columns was reduced from the initial 214% increase at a KL/r of 6.9 to 104% at a KL/r of 62.4. The fire tests revealed that unprotected CFFT columns with KL/r = 57.4 were able to sustain the applied design service loads (44% of ultimate capacity) for up to 108 min in a standard fire. However, it was determined that the unprotected GFRP tubes lost their structural integrity after approximately 10 min of fire exposure, when the temperature on the inside of the tube reached 350°C, thereby only providing thermal protection to the concrete core after the 10-min mark. The unique outcomes of this new study indicate that CFFT columns can be a viable design option in fire situations. [ABSTRACT FROM AUTHOR]