Development of Analytical Solutions and Verification Experiments for Axially Restrained Reinforced Concrete Beams in a Fire

Abstract

Fire-induced structural failure in axially restrained reinforced concrete (RC) beams is a critical concern in structural fire engineering. Comparative analysis with Eurocode and ASTM E119 fire safety guidelines reveals discrepancies between theoretical predictions and real fire-induced failures, emphasizing the need for revised structural fire safety standards. Moreover, limited analytical solutions exist due to the complexity of fire behavior in axially restrained RC beams. This study develops an improved analytical model for axially restrained beams in fire, focusing on three critical points: (i) the peak axial compression force, (ii) the transition to zero axial force (bending limit), and (iii) the final failure point due to reinforcement fracture. A series of fire resistance experiments were conducted to obtain key structural parameters, including fire resistance time (FRT), axial force redistribution, and failure mechanisms. The experimental results were used to validate and refine the proposed model, enhancing its practical applicability. The original model underpredicts fire endurance by 11–14%, whereas the upgraded model is accurate to within ~2–4% of test results. This improved performance is attributed to the model’s consideration of stiffness degradation and early cracking. Overall, the study provides valuable insights for improving the fire-resistant design of restrained RC beams, particularly in critical infrastructure such as logistics centers.

Keywords

• axially restrained beams
• structural fire engineering
• fire resistance
• catenary action
• analytical model