Design Optimization of the Flexural Behavior of a Novel UHPC–ECC–RC Composite Sandwich Panel

ABSTRACT To address the limited exploitation of the structural bearing capacity of precast concrete sandwich insulation panels (PCSPs) while achieving material emission reduction without compromising strength, stability, or durability, this study replaced part of the surface‐layer normal concrete with engineered cementitious composites (ECCs) and ultra‐high‐performance concrete (UHPC). Two new sandwich panels, an ECC–RC composite sandwich panel (ECSP) and a UHPC–RC composite sandwich panel (UCSP), were designed and fabricated, and their flexural performance was evaluated through four‐point bending tests and three‐dimensional finite element analysis. The experimental results showed that applying ECC or UHPC to the surface layer markedly suppressed crack initiation in PCSPs. With a 20‐mm replacement thickness on both the top and bottom wythes, UCSP exhibited 31% and 33% lower peak load and ductility, respectively, than ECSP, and ECC placed on the top wythe did not fully utilize its material advantages. Accordingly, the concept of a UHPC–ECC–RC composite sandwich panel (UE‐CSP) was proposed, and its applicability was validated through FE analysis. Compared with ECSP, UE‐CSP increased peak load and ductility by 37% and 41%, respectively; compared with UCSP, the increases were 46% and 65%, respectively. To support section optimization, finite element parametric analysis data were augmented using a generative adversarial network (GAN) and used to train a neural network prediction model for the peak load and ductility of UE‐CSP. Finally, employing the nondominated sorting genetic algorithm with an elitist strategy (NSGA‐II), the optimal UE‐CSP cross‐section was identified as 12‐mm UHPC in the top wythe and 28‐mm ECC in the bottom wythe.