Chase Placement In Floor Trusses
Is there a general rule of thumb to follow on chase placement within a top-chord bearing floor truss? In other words, how close to the bearing point of the truss can the chase occur?
From a design perspective, the best place to put a chase in a floor truss is at the center of the span. It is there that the shear forces will be at a minimum and the interruption of the webbing pattern will not have a significant impact. As a rule of thumb, you should try to place chases somewhere within the middle third of the truss span. While it is sometimes possible to design chases into the outer third of the span, it may be problematic. If you plan to violate the middle third convention, you should contact a manufacturer to find out whether what you are planning is practical.
You should also note that this rule of thumb assumes that the truss is simply supported and uniformly loaded. If interior bearings or non-uniform loads are present, the convention is no longer valid.