Direct shear tests of glass fiber reinforced polymer connectors for use in precast concrete sandwich panels

The precast concrete sandwich panel (PCSP) is a popular structural type used for prefabricated construction. In this study, three kinds of glass fiber reinforced polymer (GFRP) connector, including a flat plate, a corrugated plate, and a hexagonal tube connector, were investigated for potential use in PCSPs. In-plane direct shear tests were conducted to evaluate the performance of the connectors based on a typical push-out configuration (i.e., three concrete wythes linked with connectors and two rigid foam layers in between). Twenty-five specimens were tested, and the parameters investigated consisted of GFRP laminate thickness, projected length, and shear force direction. The shear force vs. relative slip relationships and failure modes of all types of connector were compared and are discussed in detail in this paper. Meanwhile, finite element (FE) analysis was conducted to reproduce the test results. All three types of GFRP connector exhibited a progressive failure manner in spite of the linear brittle nature of the FRP materials; the corrugated plate connector achieved higher deformability than the flat plate connector, particularly when the GFRP laminate thickness was small; and the hexagonal tube connector exhibited similar behavior along two orthogonal directions, making them well suited for use as two-way connectors. The developed FE model was able to well predict the peak shear load and stiffness of all types of connector based on comparisons with the test results.