Structural Behaviour of Preflex Beams in Bridges during Concrete Repair and Maintenance

Preflex beams are composite structural members that combine a steel universal beam with reinforced concrete, enabling longer spans with reduced deflection. Their strength and stiffness rely on a preflexion process, where the bottom flange is initially placed in tension and later compressed by the surrounding concrete. Despite their advantages, repairing preflex beams, particularly the bottom flange concrete, presents challenges due to its role in load distribution and deflection control. This study investigates the structural behaviour of preflex beams when the bottom flange concrete, an integral component of the load distribution mechanism, is altered during concrete repairs, addressing the need for a reliable repair methodology that ensures structural integrity. The research primarily aims to develop a robust repair methodology, specifically addressing the bottom flange concrete in preflex beams. Through a comprehensive literature review, this study examines the historical development, key attributes, and existing repair strategies for these beams. The findings reveal that while the bottom flange concrete plays a crucial role in limiting excessive deflection, its contribution to the ultimate strength of the beam is relatively minor. Consequently, the repair approach must consider the interaction of the bottom flange with other structural elements. Based on these insights, this research proposes a structured repair philosophy adaptable to various bridge configurations, facilitating the long-term maintenance and durability of preflex beam structures.