Thermally efficient corbel connections for insulated sandwich wall panels

This paper investigates several in-service and alternative designs for corbel connections in partially composite load-bearing concrete sandwich wall panels. Current practice commonly uses one of two options: 1) creating a solid concrete section at the corbel location, or 2) creating an internal pilaster within the panel at the corbel location, which is done by local thickening of the wythe which results in a reduction in insulation thickness. Reducing insulation thickness reduces the thermal efficiency of the insulated wall panels at the corbel locations and can make fabrication difficult. This study involved testing twelve sandwich wall panel corbel specimens to quantify the strength of several designs and validate them through a modified strut-and-tie design method to enable future designs and the use of those presented. This paper illustrates nine successful alternative corbel-connections that reduce thermal bridging by using different materials to resist the tension tie force at the top of the corbel including GFRP U-bars, HK connectors, IconX GFRP and IconX CFRP connectors, and GFRP grating. Test results indicated that thermal bridging at the corbel connections can be reduced without large-area reduction of the insulation thickness. Additionally, results suggest that common, off-the-shelf sandwich wall panel connectors can be effectively used to transfer the tension tie force between the interior and exterior wythes. •Corbel connections can combine both thermal and structural efficiency.•Heat loss through corbel connections in concrete structures is avoidable.•Modified strut-and-tie method can adequately predict corbel failure.