The various loadings applied to the box girder are ultimately reduced to loadings over the element and loadings at node points. Loadings that are over the length of the element are subsequently converted to element fixed-end forces (FEF) that are then summed into the system load vectors; node point loads are summed directly.

The loadings can be classified as either external or internal loadings. Typical external loadings are self-weight, applied point, and uniform loadings. Post-tensioning is considered an external loading with respect to analysis. Internal loadings are temperature, creep, shrinkage, relaxation, and the internal forces in cross section parts when they are removed from the system. Internal forces ultimately get converted to element FEF, but they also generate section and cross section part "restraining" forces that are used during cross section part force calculations.