EFFECTS OF BANDED POSTTENSIONING IN PRESTRESSED CONCRETE FLAT SLAB

This study investigates strain distribution in regions immediately adjacent to the transverse post-tensioning bands in a new class of flat slab reinforced concrete bridges employing bidirectional post-tensioning. While longitudinal post-tensioning is uniform, transverse strands are concentrated in the vicinity of column lines. The currently applied design assumes that the transverse post-tensioning effect spreads along straight lines at a specified angle. Size of a laboratory model slab is chosen so that this assumption may be checked for validity. A load schedule is used to study strain distribution for a variety of tendon and load patterns. Values of strain at gage locations as predicted by a finite element analysis are compared to the actual data collected. Reasonably good correlation between laboratory data and the computer program allows increased confidence in numerical simulation. Following testing and analysis of elastic loads, the slab is loaded to impose a punch-through shear failure. Shear formulas recommended by the American Concrete Institute and other researchers are compared with experimental failure and reserve capacity loads.