Download Frame Story Shear – Multi-Level Braces

Frame Story Shear – Multi-Level Braces
When the program calculates the shear at a particular level, it does so by adding up all of the horizontal components of
all of the lateral members at the given level. For every node that appears on that level, the forces are tallied.
When a brace is modeled such that it bypasses a level, it will not have any nodes at that intermediate level. Thus, when
the program sums all of the loads for that level, the forces within those braces are not accounted for. The net force
given in the report is therefore low, and the change in shear may appear as negative.
As you can see, the story shear is correctly reported for the Roof level and the 2 nd level where the braces have nodes. At
the mezz. Level, however, the braces have no nodes, so the forces within those braces are not included. The only shear
in the frame in that case is the shear in the columns, which in this case is null. So the total shear that the program
recognizes at the mezzanine level is 0, which is a loss of 24k from the level above.
Obviously, this information is not helpful. In those cases, it is recommended that you strike out the intermediate levels
from the frame story shear report altogether, and recalculate the "change in shear" value manually.