Practical Engineering: Permanent Bracing for Piggyback Trusses

I recently gave a class on bracing of metal-plate-connected roof trusses, attended by about 50 structural engineers. What I learned there about bracing piggyback trusses literally left me sleepless that night. In case you’re not familiar with the term, piggyback trusses are used when the height of a required roof truss exceeds the width limit allowed by a state’s transportation department for transport on the back of a truck. Depending on the state, the limit is usually around 12 to 14 feet. So say you need a 12/12 gable roof truss for a 40-foot span. The 20-foot ridge height will force the truss manufacturer to provide the truss in two parts — a bottom truss with a