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.

For example, take an inclined member which is subjected to ice and snow loads. Here, a 1kN/m ice load is applied to Global Axes such that it acts along the member, 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. The left side of Figures 1 and 2 (Global Axes) show the load and reaction of this ice load on an inclined member which is released from flexure. The right side (Projected Global Axes) shows that of the snow load. Differences are apparent.

Figure 1 - Global-Axes and Projected-Global-Axes loading

Figure 2 - Global-Axes and Projected-Global-Axes reactions