BEHAVIOR AND DESIGN OF REINFORCED-CONCRETE INVERTED T-BEAM LEDGES

The reinforced concrete inverted T-beam is a convenient structural form for supporting precast stringers. Concentrated reactions of stringers can create local shear, flexure and bar anchorage problems in the flange of an inverted T-beam. The flange or ledge of the inverted T-beam can be considered to function locally as a bracket which is supported at the face of the T-beam stem. The behavior of reinforced concrete inverted T-beam ledges was observed in two full-scale test specimens, each specimen being subjected to several different patterns of load applied to the bracket formed by the arms of the inverted T cross-section. Analytical studies were pursued with each test to understand stress and strength mechanisms. The major conclusions derived are: (1) the length of bracket that can be considered effective in flexure caused by a concentrated load should be no greater than the length of bearing plus five multiples of the distance between the face of the beam stem and the center of the bearing; and (2) the effective length of bracket for shear friction should be taken as no greater than the length of bearing plus four multiples of the distance between the face of the beam stem and the center of the bearing.