Experimental thermal bowing response of precast concrete insulated wall panels with stiff shear connectors and simple supports

Precast concrete Insulated Wall Panels (IWP) are thermally and structurally efficient systems used in buildings. Although their flexural behaviour has been studied in detail, there is limited research on thermal bowing of IWP. Bowing causes undesirable deflection and stresses that are not well addressed in design guides. Four 6.1 m long panels with Glass Fibre Reinforced Polymer (GFRP) shear connectors were tested using a thermal enclosure that in duced temperature differentials over 20 degrees C. The stiffness of the 9.5-16 mm diameter shear connectors used in the full panels was found with 18 push-through tests on representative segments of the larger panels. The connector stiffness ranged between 26 and 59 kN/m and is stiff relative to other connector systems reported in the literature. Thermal load caused bowing that ranged between 39 and 44% of the Canadian concrete design standard (A23.3-14) acceptable service load deflection at a 20 degrees C temperature differential. Thermal load cracked the IWP and loaded connectors beyond their proportional limit. The amount of thermal bowing at a 20 degrees C temperature differential increased 16% with an 82% increase in connector stiffness. Results of these tests in dicate that bowing is significant in panels with high connection stiffness and may be a concern in long panels designed to carry axial loads.