Experimental and Numerical Investigation of Fire Performance of Axially Loaded GFRP Columns

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Abstract
The fire performance of Glass Fiber Reinforced Polymer (GFRP) reinforced concrete columns represents a critical knowledge gap in contemporary structural fire engineering. This study presents a comprehensive experimental and numerical investigation that compares the fire behavior of GFRP-reinforced and steel-reinforced concrete columns at elevated temperatures. Six full-scale circular concrete columns with a diameter of 380 mm and height of 3660 mm with different reinforcement configurations were subjected to theISO-834 standard fire exposure while maintaining constant axial loads at 30% and 50%load ratios. Experimental results revealed that under high axial load ratios (50%), GFRP and steel reinforced columns exhibited comparable fire resistance durations (34 minutes vs. 35 minutes). However, under moderate loading conditions (30%), steel-reinforced columns demonstrated superior performance with a 73% longer fire resistance duration(142 minutes vs. 82 minutes). Sequential thermal-mechanical finite element models were developed in ABAQUS and validated against experimental data, enabling parametric studies examining the effects of axial compression ratios (10%-60%), various concrete cover thicknesses (20-40 mm), and boundary conditions. A critical axial compression ratio threshold of 30% was identified for both reinforcement types, beyond which fire resistance deteriorated significantly. GFRP-reinforced columns exhibited enhanced thermal compatibility with the concrete matrix, characterized by reduced differential thermal expansion and more gradual, ductile failure progression. The numerical analysis confirmed that under axial compression ratio (≤30% axial ratio) and adequate concrete cover (≥30mm), GFRP-reinforced columns can achieve fire resistance performance equivalent to conventional steel systems while providing superior deformation control and progressive failure characteristics. These findings establish design criteria for GFRP reinforcement in fire-critical applications and support performance-based fire engineering methodologies for advanced composite structural systems.

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