Numerical investigation of the flexural behaviour and composite action of reinforced concrete sandwich panels (RCSP) with EPS core: parametric study using FEA

Conventional unreinforced brick masonry walls pose significant sustainability and seismic vulnerability challenges due to excessive resource consumption and self-weight. Reinforced Concrete Sandwich Panels (RCSP) with Expanded Polystyrene (EPS) core present a promising alternative, offering similar functional benefits while being lightweight, sustainable, and exhibiting enhanced seismic performance. This study investigates flexural behaviour of RCSP using validated three-dimensional nonlinear finite element model developed in Abaqus/Explicit, demonstrating close agreement with experimental results in terms of ultimate load capacity, crack initiation and propagation, and failure mechanisms. A systematic parametric study evaluated the influence of shear connector type, spacing, diameter, Welded Wire Mesh (WWM) size, EPS core thickness, and longitudinal reinforcement. Among connector types, Double-Truss Shear Connectors (DSC) increased the ultimate load capacity by up to 12-18% and improved post-peak ductility compared to orthogonal and Single-Truss Shear Connectors (SSC). Reducing connector spacing from 150 to 75 mm enhanced the ultimate load capacity by approximately 8.9%, with negligible change in failure mode. Increasing WWM diameter from 3 to 6 mm resulted in significant increase in flexural strength of up to 102.8%, indicating strong dependence on reinforcement stiffness. Variations in EPS core thickness showed less than 3% change in flexural capacity, confirming its negligible structural contribution under bending. Inclusion of additional longitudinal reinforcement (6 mm Fe500 bars at 160 mm spacing) increased ultimate load capacity by 40.5% and significantly enhanced ductility. These findings provide critical insights into the governing parameters affecting composite action and offer design-oriented recommendations for optimizing RCSP systems as lightweight, sustainable, and seismic-resilient alternatives to conventional masonry walls.