Regular vs. Projected loading

Loading differs when applied to either Global Axes or Projected Global Axes in that Projected loading is distributed along the horizontal projection of an inclined member. In this case, loading is scaled by the cosine of the incline angle such that the gravity component is applied.

An example may involve an inclined element subjected to ice and snow loads. Here, a 1kN/m ice load is applied to Global Axes such that it acts along the element, and a 1kN/m snow load is applied to Projected Global Axes such that its gravity component is present. This is realistic in that snow loads align with the gravity direction regardless of incline, being dependent only upon the horizontal span. The left side of Figures 1 and 2 (Global Axes) show the load and reaction of this ice load on an inclined element released from flexure. The right side (Projected Global Axes) shows that of snow load. Differences are apparent.