Full scale testing of precast concrete sandwich panels

This paper describes newly developed precast concrete sandwich panels. The panels use a new system of fiber reinforced plastic (FRP) connectors, developed at the University of Nebraska's Center for Infrastructure Research, for transferring shear forces from one concrete wythe to the other. The use of FRP as the connector material increases the thermal efficiency of the panels compared to panels that contain steel at concrete connectors. The geometry and material properties of the new connector provide sufficient strength and stiffness for a significant transfer of shear between the two concrete wythes. The results of structural tests are analyzed and design recommendations are presented. Description of an accompanying thermal performance testing of these panels is also included. Four full-scale specimens were tested in a vertical position. Two of the specimens contain the new FRP connectors, and two contain steel truss connectors. Measurements of load versus panel deflection and load versus connector stress are provided. The ultimate strength of the panels containing the new connector were found comparable to the strength expected of fully composite panels. The design of panels containing the proposed FRP connecting system can be undertaken in a manner similar to that of fully composite panels. Ultimate strength of the panels can be computed assuming full composite action between the concrete wythes, if sufficient shear connectors are provided and the panels are not over-reinforced.