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Don’t Forget! You Saw it in the
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April 2021 #13261 Page #116
Understanding Ply-To-Ply Girder Nailing Failures ou probably wouldn’t ignore a “warning sign” on the highway, as you can easily imagine the consequences of doing so. We can face By Christopher Gould similar situations when designing trusses, and the end result is that whatever we do in the software can end up in the real world somewhere on a jobsite.
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Because of the nature of this job as a designer, it is common to lose touch with the reality of the rest of the process. A component designer can be jumping from one job to another during the day and be involved in several projects at the same time. We may fail to see or, worse, may ignore some warning signs along the way (either in an office or a remote location). Sometimes the result is that we simply are unaware of some warning messages. One of these “warning signs” is the PLY-TO-PLY-NAILING issue. In MiTek, this message is oftentimes simply overlooked, as VersaTrus does not give you the Red “X” symbolizing a failed truss. Some designers think of it as just a warning and, in a rush, could overlook it. Some facilities do not assemble plies in the plant and leave that responsibility up to the General Contractor or Framer. Some do assemble. This does not mean a designer can overlook it. Additionally, in recent versions of MiTek, ply-to-ply nailing is considered a failed truss and obligates the designer to correct it. This happens most often on roof girders which could require 3 or 4 plies. Do we, as designers, truly understand what this “failure” means though? If our truss has a Green “check” next to it, then it works, right? Actually, trusses work as a single entity of themselves as they apply to a truss system. These factors are totally contingent upon what settings are selected based on the reality of materials to be applied on the job site. However, when multi-ply trusses are combined, each single ply of a truss entity becomes joined together. Multi-ply trusses are commonly known as “girders.” A girder is a truss that carries another truss (or carries some type of load or framing on the project). What this error message is telling you is that: 1. The connection of the plies as they attach to each other is what is failing. 2. The truss itself may work to carry the loading that attaches to it, but the fasteners of the
ply attachment are inadequate. 3. The total number of fasteners (nails/screws) is insufficient to be applied based on the
selected chord and/or web size.
4. The fasteners are shearing and must be upgraded. Continued next page
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