Flexural strengthening of prestressed I-beams using jointed and unjointed precast UHPC layers

This study introduces a novel, modular approach for the flexural strengthening of large-span prestressed reinforced concrete (PRC) I-beams using segmented precast layers of ultra-high-performance concrete (UHPC) reinforced with glass fibre reinforced polymer (GFRP) bars. This methodology addresses key constructability challenges associated with continuous, in situ strengthening of long bridge girders. The primary aim was to evaluate the effectiveness of this segmentation by considering parameters such as layer continuity and reinforcement overlap. Experimental findings from seven PRC beams demonstrated exceptional structural performance. The external precast UHPC layers yielded a substantial enhancement in load-carrying capacity (82%–112%) and initial stiffness (49%–61%). While the introduction of a joint caused only a marginal load reduction (4%–14%), it crucially provided a mechanism for controlled failure localisation, acting effectively as a plastic hinge. Furthermore, the study confirmed excellent bond integrity between the UHPC overlay and the concrete substrate, with no observed separation. These results validate the segmented precast UHPC overlay as a highly viable, efficient, accelerated and economically advantageous solution for the rehabilitation and performance upgrade of large-span structural members.