Investigation of Various GFRP Shear Connectors for Insulated Precast Concrete Sandwich Wall Panels: Fid-Bau Portal

Investigation of Various GFRP Shear Connectors for Insulated Precast Concrete Sandwich Wall Panels

Woltman, Greg / Tomlinson, Douglas / Fam, Amir

Glass fiber–reinforced polymer (GFRP) shear connectors provide much reduced thermal bridging in insulated concrete sandwich panels compared to steel connectors. In this study, 50 specimens with dimensions of $254 \times 254 \times 900 mm$ representing segments of a precast sandwich wall comprising two concrete wythes and a concrete stud surrounded by insulation foam have been tested in a double-shear configuration. Three types of GFRP connectors produced from available sand-coated and threaded rods were tested and compared to conventional steel and polymer connectors. GFRP connector diameters varied from 6 to 13 mm, and spacing varied from 80 to 300 mm. Both circular and rectangular cross sections were examined, along with various end treatments to compare with simple straight embedment. The shear strength of GFRP connectors, including the effect of friction between concrete and foam, ranged from 60 to 112 MPa, significantly higher than polymer connectors but lower than steel connectors. As the connectors bridged a small gab of insulation between concrete wythe and stud, their shear strength was lower than manufacturer-reported values. Varying the size, spacing, cross-section shape, or end treatment of connectors had insignificant effect on their strength. The connectors failed by longitudinal delamination then transverse shear but did not pull out of the concrete wythe. Adhesion bond between concrete and insulation was quite significant and contributed about 28%, but was quite random and variable. A model was developed to predict the strength of connectors and clearly demonstrated the reduction in strength as thickness of insulation layer increases.