Piggyback wood trusses - connections.
Piggyback wood trusses - connections.
(OP)
When a wood prefab roof truss must be broken down into two pieces for shipping purposes, whose responsibility is it to provide the design for the piggyback truss to base truss connection? The structural EOR, or the truss designer?






RE: Piggyback wood trusses - connections.
RE: Piggyback wood trusses - connections.
I agree 100%. Thanks for the reply. Got in a little bit of an argument with a fellow engineer in our office with regards to this question.
RE: Piggyback wood trusses - connections.
And, if you think about this, it is the most efficient way, they design the components day in and day out - right down to the Gnat's A--!
RE: Piggyback wood trusses - connections.
If the vendor is expected to provide remedy for truss failure, they won't like the surprise of "Oh, we cut them in half for transport".
Be honest with the poor guy. Tell him upfront that the truss needs to be sectioned, and pay him what he asks.
I suspect this is all about extra costs. Am I correct?
RE: Piggyback wood trusses - connections.
RE: Piggyback wood trusses - connections.
"Why is the vendor not being advised of the need to section the truss?
If the vendor is expected to provide remedy for truss failure, they won't like the surprise of "Oh, we cut them in half for transport".
Be honest with the poor guy. Tell him upfront that the truss needs to be sectioned, and pay him what he asks."
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Huh!?
I am the engineer of record. Splicing the truss for transport is at the truss designer's discretion. As some of you have answered as I anticipated, this splice design is ultimately his responsibility. Yes, as the structural engineer, we provide the specifications, general truss layout, and the truss profile and support conditions to which the truss designer must adhere, but the ultimate design of the trusses is left up to him. After all, as someone alluded to, a roof truss is a component. I don't tell him what size gang-nail he needs for chord to web connections, so why would I specify and design a truss splice connection?
methinks you missed the point, Steve.
RE: Piggyback wood trusses - connections.
I detail the connection to the base truss. Usually this is some additional hurricane anchors. This is noted on the truss diagram. The roof diaphragm will also help with the anchoring but you don’t know the length of nailing of the overlapping panels so I don’t count on it at all.
RE: Piggyback wood trusses - connections.
RE: Piggyback wood trusses - connections.
The EOR is responsible for designing a product that works. That means the design can be built and put into service (I could design a monolithic precast concrete beam to span 500 ft. but no one would be able to get it from the casting yard to the construction site and there's probably no crane that could lift it into place).
I would say that the EOR is responsible if ALL of the following conditions were in fact:
1. The fabricator had no reasonable way to transport the truss as it was designed;
2. The plans, special provisions, or other contract documents did not include any statement, provision, or guidance with regard to breaking up the truss;
3. There are no industry standards, such as governing building codes, or trade associations (TPI - Truss Plate Institute) that provide sufficient guidance to allow any licensed fabricator to alter the truss design in a specific manner; and
4. The fabricator did NOT agree to provide truss design and documentation by a LICENSED AND QUALIFIED engineer.
If the fabricator DID agree to provide truss design and documentation by a LICENSED AND QUALIFIED engineer, then the fabricator is responsible for the truss "period". Furthermore, the owner (or his agent) should have received plans signed and sealed by the fabricator's engineer-in-charge.