Testing trusses: a powerful education for CET students
CHALLENGE: How can trades working in the construction industry quickly and effectively gain working knowledge of proper hole placements in I-joist truss systems so they never compromise truss performance?
I-joists are strong, lightweight, “i”-shaped, engineered wood products developed for and used extensively in residential floor and roof framing.
Because of their strength and because they successfully resist the bending, twisting or warping often seen with dimensional (natural) lumber, I-joists are good for straight, true, long spans. Their design also makes it possible to hide most of the heating, plumbing and electrical inside the floor systems. However, holes drilled in the wrong places can lead an I-joist to fail, costing the building industry dearly in repairs and lost time.
SOLUTION: By testing the load-bearing performance of I-joist trusses drilled with holes placed in both incorrect and correct locations, SAIT's Civil Engineering Technology (CET) students are learning first-hand the implications of hole placement in I-joist systems.
According to Carlo Velcic (CVT ’78), instructor with SAIT’s School of Construction, I-joist testing isn’t complicated, nor will it uncover anything new. But he’s confident the testing — a final, or Capstone, project for CET students — will have powerful and lasting implications.
“Even though we have hole charts to explain where the holes have to go, no one really understands why. So we want to do the actual testing and capture on video what happens when you put a hole in the wrong spot,” says Velcic. “Once students see that, they’ll understand and remember!”
Producers of I-joists — such as Weyerhaeuser, the industry partner supplying I-joists for testing — all create hole charts for trades to follow. However, according to Velcic, charts get lost, are confusing, aren’t on the job site or simply aren’t convenient to consult.
Correct hole placement isn’t necessarily intuitive. One student suggested the best place to drill is at the end of an I-joist and the worst place is the centre. In fact, Velcic says, it’s the opposite — the largest hole you can drill is at the centre of the joist and the smallest is at the bearing end.
For their part, Weyerhaeuser’s decision to provide I-joists for the project was an easy one. Kent Drescher, Territory Manager with Weyerhaeuser, says attracting students to the forest products industry is competitive and projects such as this help.
“If we offer these kinds of initiatives where students can work with wood — touch it, feel it, see what happens to it — it adds to the interest in wood and generates some excitement for them as they choose a career post-graduation.”
Velcic, a long-time building construction professional and a one-time truss manufacturer, says the idea for this project has been on his mind a long time. He hopes what students capture on video this term will help persuade industry to fund a future capstone to professionally film a training video that will help all trades understand I-joist hole placement.
“Once they see it, they’ll never forget — it’s impressive enough for people to really understand where you can put the holes and why. It’s not earth shattering — it’s just good, common sense stuff.”
Written by Christie Simmons