Lumped GFRP star connector system for partial composite action in insulated precast concrete sandwich panels

Abstract This paper introduces a novel composite shear connectors system used to transfer interface shear forces in a precast concrete sandwich panel. The shear connectors consist of non-proprietary non-composite commercial glass fiber reinforced polymer (GFRP) pin connectors that are laid out in a star pattern and clustered at the top and bottom of the panels. The testing program consisted of thirty-four push-off, twenty-three pullout, and eight full-scale flexural specimens was conducted to evaluate the structural performance of the new shear connectors. The effect of concrete wythe thickness, insulation wythe thickness, and concrete compressive strength was investigated throughout these tests. Additionally, the effect of bond between insulation and concrete wythes was investigated using push-off tests. The flexural test results were compared with predicted fully composite, non-composite, and partially composite values to evaluate the overall panel performance. The comparison showed satisfactory performance with a lower bound of 90% composite action for specimens with 100 mm thick insulation wythe and full composite action for most panels with 50 mm thick insulation. Idealized shear load-slip curves were also developed that account for various parameters to assist design engineers in designing insulated sandwich wall panels with the proposed shear connectors system.