Structural Evaluation of Notched Insulation in Precast Concrete Sandwich Panels

Abstract

AbstractSandwich wall panels are typically comprised of two concrete layers (or wythes) that surround a layer of rigid insulation. The most common insulation types used in precast wall panels are Expanded (EPS) and Extruded (XPS) polystyrene. Previous work showed that walls with EPS insulation have higher in-plane shear strength compared to an XPS system. This increase is due to the surface roughness of EPS but is often neglected in design as this bond is expected to fail over time. In this study, the use of notched insulation is investigated. The notches allow XPS to achieve higher capacities since bond failure is prevented as well as prevents bond degradation from reducing the insulation contribution to shear resistance in the long term. Direct shear push-through tests were completed on 15 specimens, with 9 notched and 6 un-notched samples. All specimens were constructed with GFRP bar shear connectors arranged in an X-shape. Test parameters include GFRP bar diameter (9.5 and 16.0 mm), while using XPS, and notch type (no notch, trapezoidal, rectangular). Deformation over the course of the push-through tests was tracked using displacement transducers. When the 9.5 mm connector was used, the the inclusion of rectangular notches resulted in 26.7% and 33.3% increase in the initial stiffness and peak load respectively, while the trapezoidal notches only gave respective increments of and 17.1 and 21.1%. The benefits in the placement of notches trend are not seen between samples made of 16 mm connectors were the respective parameters only saw −10.8 and 10.5% boost.