Cracking behavior and structural performance of ultra‐narrow <scp>UHPC</scp> wet joints in precast bridge decks

Abstract Precast concrete bridge decks require robust joints to replicate the structural performance of monolithic systems, yet conventional joint designs often prioritize load capacity over crack control and material efficiency. This study introduces ultra‐narrow UHPC wet joints (150 mm width), a 50% reduction from standard 300 mm joints, to address this gap. Three specimens, a monolithic panel and two precast panels with funnel‐ and wedge‐shaped UHPC joints were examined under four‐point bending to evaluate failure mechanisms, load‐deflection behavior, crack mechanisms, stress–strain behavior, and ultimate capacity. Results demonstrated that the 150 mm UHPC joints achieved comparable crack resistance to monolithic systems, with initial cracking loads of 65–75 kN for precast panels versus 70 kN for the monolithic panel. UHPC's superior bond strength prevented interfacial cracking, while staggered U‐shaped rebar lap splices minimized crack propagation, revealing that reinforcement arrangement critically governs crack height, spacing (100–128 mm), and width (≤0.48 mm). The narrow joints reduced material use by 30%–40%, achieved full reinforcement yield strength (2500–5000 με), and replicated monolithic stiffness through non‐contact staggered lap splices. The funnel‐shaped joint, with its optimized geometry, reduced crack spacing disparities by 20% compared to wedge joints and matched monolithic stiffness (34 GPa). These findings demonstrate that the ultra‐narrow joints reduced material use significantly while maintaining structural integrity, offering a sustainable, code‐compliant solution for precast bridge decks. These advancements redefine precast joint design, balancing performance, sustainability, and cost‐effectiveness.