Moment and shear envelopes for live load are developed in two phases:

The truck load comprises the axle loads and preceding/trailing uniform loads acting together. When performing live load analysis, the program first considers the lane load (including associated concentrated loads) acting alone. Then, it considers the truck load acting alone. At each section, comparing these two envelopes and taking the critical value obtain the values of the live load envelopes. This process is done for each of the trucks selected on the Loads screen; the final envelope covers each of these envelopes.

Note that the values of the moments and shears are calculated at the tenth points of the pier-to-pier distances. However, when an individual beam is designed, a point of interest along the beam may not fall exactly on a tenth point. For such a case, the moment or shear is approximated by parabolic interpolation between adjacent known values. The use of parabolic interpolation, instead of a straight-line interpolation used in previous versions of Precast/Prestressed Girder, should give slightly different and more precise results, especially near the supports where the curvature of the moment diagram increases.