BOX GIRDER BRIDGE DIAPHRAGMS WITH OPENINGS

The diaphragms considered in this study are of the type frequently met in box girder bridges supported on single slender piers. The outside loads are assumed to be transmitted from the bridge main girders to the inclined (or vertical) surfaces of the diaphragms in the form of uniform shearing forces. Three locations are considered for the prestressing forces applied to resist the tensile stresses and forces due to load. Other variables are: height, ratio of opening width to diaphragm span, width of supporting column, and slope of the sides of the diaphragm. The normal and shear stress distributions along horizontal zontal and vertical sections are plotted for a few typical cases. Nomographs have been developed for determining the critical stresses and resultant forces due to external loads and due to prestressing forces acting at various locations.