Flexural response of double-wythe insulated ultra-high-performance concrete panels with low to moderate composite action

摘要

This paper presents a flexural experimental investigation of a new double-wythe panel design using ultra-high-performance concrete. Very thin (25 mm [1 in.]) wythes were used with a layer of extruded polystyrene core ranging from 50 to 150 mm (2 to 6 in.) in thickness, a design that is significantly lighter in weight than conventional panels. A total of eight 3000 x 600 mm (120 x 24 in.) panels, including one with steel fibers and seven with polyvinyl alcohol (PVA) fibers, were tested in four-point bending. Six of the eight panels with PVA fibers included additional mesh reintbrcement in the wythes. The reinforcement was made of 4.2 min (0.17 in.) diameter glass-fiber-reinforced polymer (GFRP) reinforcing bars with spacing that provided a longitudinal reinforcement ratio ranging from 0.28% to 0.92%. Two panel designs were considered in this study: a very low-composite design intended for minimal thermal bowing and a design with moderate composite action for enhanced flexural performance. The low-composite design used 4.2 mm GFRP transverse ties with only a 0.0145% rein torcement ratio, while the moderate-composite design used a heavier (0.048%) tie reinforcement ratio of the same reinforcing bars but oriented in diagonal configurations. The panel with PVA fibers achieved 48% of the flexural strength compared with the panel with steel fibers. Panels with mesh reinforcement achieved on average 78% higher strength than the panel with fibers only, regardless of reinforcement ratio. As insulation tripled in thickness, flexural strength increased 2.4 times. The calculated degree of composite action in panels with transverse ties was 5% to 15%, while that of the panel with diagonal ties was 32%.