Shear Behavior of Precast Prestressed Inverted-Tee Concrete Beams with Dapped Ends ;;
Two full scale precast pretensioned dapped ended rectangular beams designed by PCI design handbook for a major domestic live load of market and parking building - 500kgf/㎡ and 1,200kgf/㎡ were investigated experimentally. The bottom length of beams was 60cm which was same to the length of rectangular column in the base of five-story market or parking buildings. The height of dap was web hight plus half of the flange height within the allowable limit of PCI method. Shear tests were performed on four beam ends. Followings were obtained from the experimental study. All of the specimens were fully complied with the PCI design handbook. Two of four specimens which were designed for live load of 1,200kgf/㎡ showed crackings at the re-entrant corner of dap before the full service loadings, and failed by direct shear at the load level much less than their calculated nominal strength. The specimens designed for live load of 1,200kgf/㎡ failed at 772 tonf and 78.36tonf by direct shear crackings. This strength was less than PCI limit of 81.9 tonf and higher than ACI limit of 65.62tonf. Thus, the limit suggested by ACI seems more reasonable in regard of safety in view of this test results. According to load-strain curves, the strain of hanger reinforcement reached almost yield strain. It is recommended to use more inclined hanger reinforcement of improve the strength and serviceability.