Experimental investigation of longitudinal shear transfer in insulated concrete wall panels with notched insulation

Abstract Precast concrete sandwich panels are usually comprised of two concrete layers surrounding rigid insulation. The most commonly used insulation types are extruded (XPS) and expanded (EPS) polystyrene or polyisocyanurate (PIR). Studies have shown that walls with EPS insulation develop higher composite action than walls with XPS insulation because of EPS's surface roughness. In this study, notched insulation is investigated using double shear push-through tests on 24 specimens (18 notched and 6 un-notched). Specimens were constructed with X-shaped GFRP bar shear connectors . Test parameters include GFRP bar diameter (9.5 and 16.0 mm), insulation type (XPS, EPS, PIR), and notch type (trapezoidal, rectangular). Notches allow XPS to reach higher capacities since bond failure is mechanically prevented. On average, when the 9.5 mm connector was used with XPS, adding rectangular notches resulted in 37% and 50% increase in the connection proportional limit and peak load respectively, while trapezoidal notches gave lesser respective increases of 21% and 27%. These increases were not apparent in samples made with larger (16 mm) connectors since stiffer connectors attract more proportion of the load nor in samples with EPS or PIR insulation where the foam's surface roughness combined with stress concentrations at notches promoted diagonal shear failure.