Compressive behavior of wood I-joist under elevated temperature

Abstract

Wood composite I-joists are commonly used in residential construction and light commercial buildings, particularly in floor and roof assemblies. These assemblies are often fire-rated, based on building design, to meet specific safety standards. Fire-rated assemblies are constructed using manufacturer-specified materials such as gypsum board and fire-retardant plywood. While I-joists may not be directly exposed to flames, they can still experience significant thermal exposure. This study investigates the effects of elevated temperatures on the compressive strength and modulus of elasticity (MOE) of I-joists, with 90 specimens tested across various temperatures and two exposure durations. Results indicate that significant degradation in mechanical properties occurs around 190°C, with OSB web buckling identified as the primary failure mechanism. A Sigmoidal model was applied to capture the temperature-dependent degradation, revealing critical property decline near 200°C and higher. This research provides insights into the thermal behavior of I-joists, with implications for maintaining structural integrity in high-temperature environments, and highlights the need for further studies on long-term exposure and temperatures above 200°C.