Quantitative scalar damage evolution of fire-exposed reinforced concrete beam using ultrasonic pulses

Gabriel I. Gamana , Edgardo. S. Legaspi , Jordan. N. Velasco , John Lemar. M. Tirao

Abstract

Rapid urbanization worldwide drives the construction of numerous buildings and infrastructure, essential for both social and economic development. However, these structures face significant risks of partial or complete damage when exposed to accidental fires. While existing codes prioritize life safety measures, they often lack comprehensive guidelines for post-fire structural assessment and rehabilitation, potentially resulting in structural condemnation. This research study introduces an innovative approach utilizing the ultrasonic pulse velocity (UPV) test to develop a scalar damage model. This model correlates the damage parameter of reinforced concrete (RC) beams, both with and without fire exposure, to variables such as the nature and intensity of applied stresses, concrete strength, and steel ratio. The findings indicate a substantial reduction in initial UPV readings for RC beams exposed to fire, up to 20.51% compared to those without fire exposure, aligned with the existing literature suggesting a proportional loss in concrete strength. Moreover, the inclination angle of the elastic data trend is proportional to the damage accumulated by the concrete, notably higher for RC beams with fire damage, particularly under compression stress. Furthermore, this angle is also influenced by various factors, including the steel ratio and concrete strength, regardless of fire exposure. Additionally, RC beams subjected to fire damage exhibit reduced deflection, indicating a less ductile response compared to those without fire exposure. This reduced ductility is attributed to the decarbonization of the cement binder and the formation of crack networks in the concrete, leading to a decrease in overall response.

Key Words

fire damage; microcracks; scalar damage; ultrasonic pulses

Address

Gabriel I. Gamana, Edgardo. S. Legaspi — Department of Civil Engineering, Technological University of the Philippines, Manila, Philippines
Jordan. N. Velasco — Department of Electrical Engineering, Pamantasan ng Lungsod ng Valenzuela, Philippines
John Lemar. M. Tirao — Department of Civil Engineering, Pamantasan ng Lungsod ng Valenzuela, Philippines

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