Experimental and theoretical analyses for flexural performance of reinforced concrete beams using ultra‐high‐performance concrete permanent formwork panels embedded with reinforcement grids

Abstract This study investigates the application of precast ultra‐high‐performance concrete (UHPC) panels as permanent formwork, enabling them to function as integral structural components of reinforced concrete (RC) beams. The proposed formwork incorporates embedded stainless‐steel grids and three distinct surface configurations to elucidate their roles in flexural performance. Experimental results demonstrate notable improvements: cracking loads were approximately doubled, stiffness was significantly enhanced, and flexural capacity increased by around 30% compared to conventional RC beams. Surface treatments, including ribs and shear keys, effectively enhanced the bond between the UHPC formwork and the cast‐in‐place concrete. To support design optimization, a theoretical model was developed to quantify the contributions of the UHPC formwork, embedded grids, and cast‐in‐place concrete across different flexural stages, enabling performance prediction under various design scenarios. The findings reveal that while grid characteristics predominantly influence yielding and ultimate flexural capacity, the thickness and material properties of the UHPC formwork mainly control crack initiation and early‐stage behavior. These insights provide a basis for advancing the design of UHPC permanent formwork in RC structures, aiming to improve structural performance while streamlining construction processes.