AD.2007-1001.1.5 In-Plane Area Loads on Plates
STAAD.Pro can now apply plate loads in the local X and Y directions to represent in plane friction loads.
As shown in the next figure, pressure on the full element can now be applied along local X and Y axes.
Thus a -2 kip/ft2 load applied to an element that is 3 ft2 will result in -6 kips being applied in the plane of the element.
This applies only to Pressure on Full Plate.