Long-term behavior of precast, prestressed concrete sandwich panels reinforced with carbon-fiber-reinforced polymer shear grid

■ The applied fatigue testing did not affect the ultimate performance of the panels and had a minimal effect on the composite action between the wythes. Precast concrete sandwich panels are typically used to construct high-performance, energy-efficient building envelopes. These panels typically consist of two concrete wythes separated by rigid foam insulation, such as expanded polystyrene (EPS) or extruded polystyrene (XPS). The panels are designed to resist floor loads as well as wind or seismic lateral loads while providing efficient insulation to the structure. They are often fabricated with heights over 45 ft (13.7 m) and widths up to 15 ft (4.6 m). Wythe thickness commonly ranges from 2 to 6 in. (50.8 to 152.4 mm), and overall panel thickness may be from 6 to over 12 in. (304.8 mm). Longitudinal prestressing is normally provided in both concrete wythes to control cracks.