Projected Area

With the use of a check box you can choose to model roof masses by means of the projected area load on the roof rather than the actual self-weight of the building materials. You might want to do this…

• Because this method creates a simpler model with fewer loads, and is sufficiently accurate in most circumstances
• Because you are accustomed to specifying roof loads as projected area loads.

If the projected area is chosen for self-weight the building mass generation is simple – area load is multiplied by half the depth of the roof block, including overhangs, to determine the line loads that are placed on the shear lines closest to where the roof meets the block walls. The line loads start and end at the ends of the block in the perpendicular direction.