Title: Effect of Hinge Zone Tie Spacing on Ductility of Concrete Tilt-Up Frame Panels
Author(s): Michael Dew, Robert Sexsmith, and Gerry Weiler
Publication: Structural Journal
Appears on pages(s): 823-833
Keywords: buckling; concrete, reinforced; ductility; shear; tie; tilt-up.
Reinforced concrete tilt-up panels provide a variety of functions in modern buildings. One of these is to resist in-plane shear forces due to wind or seismic loads. With architectural trends requiring increasingly larger openings, the panels will sometimes behave more like frames than shear walls. The mode of failure for frame panels subjected to large in-plane lateral loads is expected to be flexural hinging of the frame members. The research reported in this paper investigated the effect of hinge zone tie spacing on the ductility of concrete tilt-up frame panels. The results of tests carried out on six quarter frame panels with three different tie spacings are presented. It was found that hinge zone tie spacing can affect the mode of failure and have a significant influence on panel ductility. The hinge zone tie spacings tested were 100, 200, and 300 mm (4, 8, and 12 in.). The mode of failure for the 200 mm and 300 mm (8 and 12 in.) tie spacing specimens was buckling of the longitudinal steel reinforcement in compression after the cover concrete had spalled. The 100 mm (4 in.) tie spacing was observed to be adequate to prevent buckling of the longitudinal reinforcement after loss of the cover concrete. The100 mm tie spacing specimens failed via either local out of plane buckling of the entire hinge zone reinforcement cage, or by pullout of the longitudinal beam reinforcement resulting from bond loss within the hinge zone. The full frame displacement ductilities achieved for the 100 and 200 mm (4 and 8 in.) tie spacings were 5.7 and 3.9, respectively. The 300 mm (12 in.) tie spacing specimens failed to maintain the full design flexural strength beyond the yield displacement.