On a recent plant visit, we came across a situation that is hopefully rare. The truss builders had hand-cut floor truss webs at the table in several places because the webs provided with the cutting were mis-cut. The result: a truss that might “look” okay but would not be safe to use.
In this case, the webs (on the left in Figure 1) were cut too short for the set-up. Instead of following the cutting information, however, the builders at the table took a short cut, literally. Instead of double-cutting the floor truss web as per the design, they single-cut the web to fit. [For images, See PDF or View in Full Issue.] Their skill cutting the web to a very tight fit was impressive, but unfortunately their single-cut rather than the design double-cut created a totally different design. (See Figure 2 for diagram of cut type terminology.) To run this web single-cut, the truss should have been redesigned accordingly, so the connectors and loads could be calculated properly.
The next photo (Figure 3) was another similar situation where the web was cut against the vertical and not the chord. [For images, See PDF or View in Full Issue.] Notice the tooth marks where the top plate was removed. These photos were taken as the truss was being built and was still in the jig. The top plate was about to be pressed with the second roll of the gantry. Although this happened on a floor truss, the rules are the same on a roof design. Always follow the engineering and cutting instructions. Catching the problem just in time, we were able to avoid having to completely disassemble the truss and rework the connections.
As you are reading this, you may be thinking: “But sometimes we square-cut webs?” “What about that?” The same rule applies. The software is there for a reason—you need to input the proper assumptions and then follow the plan.
Don’t let your haste create larger problems, not to mention the potential for more serious consequences.
An ANSI/TPI 1 3rd Party Quality Assurance Authorized Agent covering the Southeastern United States, Glenn Traylor is an independent consultant with almost four decades of experience in the structural building components industry. Glenn serves as a trainer-evaluator-auditor covering sales, design, PM, QA, customer service, and production elements of the truss industry. He also provides project management specifically pertaining to structural building components, including on-site inspections and ANSI/TPI 1 compliance assessments. Glenn provides new plant and retrofit designs, equipment evaluations, ROI, capacity analysis, and CPM analysis.