SBCRI: Discovering a Building's DNA?
Qualtim & SBCRI Team Up to Disprove Product Defect Claims
Jobsite photo shows spot where truss pulled out from nails. Qualtim and SBCRI’s challenge was to construct a set-up that precisely replicated the scenario on the jobsite.
A2 fails when the truss pulls out from the two end nails girder during Test 1. No hanger is present.
Without Qualtim’s forensic testing expertise, the outcome of this case could have been much different.
Truss collapses and the accidents that result from them can have devastating consequences. Proving negligence can become a matter of one expert opinion versus an opposing expert opinion. Thankfully, technology help us generate data to make compelling cases to either prove or disprove allegations in a court of law. In the same way the medical field uses DNA testing, clients in building industry have a resource with proven forensic engineering and testing experience—Qualtim.
Imagine that a member of a framing crew falls from the ridge of a roof truss manufactured by your company when the truss suddenly collapses. He hits his head on the concrete foundation below and dies on impact. The owner of the framing company sues your company on four counts of negligence; he seeks damages totaling more than $2 million. Gah. You don’t believe your product caused the accident, but how will you prove it in court?
One Qualtim client didn’t have to imagine this scenario; it happened to his company just a few years ago. He called Qualtim for advice on how to build a case that would prove his company wasn’t liable for the accident. After reviewing the details of the case, Kirk Grundahl, P.E. told the client that SBCRI could recreate the accident and use the results to refute the negligence claims in the trial. Grundahl has 25? years of experience as an expert witness in numerous of lawsuits involving building components, combined with his strong foundation in structural engineering.
Using Qualtim’s forensic engineering and SBCRI’s testing services, Grundahl helped the client build its case. The negligence claim asserted that the bottom chord of the fallen truss had failed. It further asserted that knots in the bottom chord weakened the truss, and the weakening was likely what caused the failure. Studying jobsite photos taken directly after the accident, Grundahl noticed a detail that led him to believe the collapse was caused by an entirely different occurrence. As shown [left?], it appears that the collapsed truss pulled out of the girder truss it was nailed to. You will also notice that the trusses on both sides of the missing truss are not resting in hangers. Grundahl surmised that the truss fell straight down to the ground as a result of the absence of a hanger securing it to the girder truss.
Qualtim recreated the conditions on the jobsite in SBCRI’s testing facility using a 100% scale roof truss assembly. They conducted two tests. The first test was set up to demonstrate how the truss fell. The truss was end nailed into a girder and was not secured with a hanger, just as it was in the field. SBCRI staff took many pictures documenting the set-up and prepared a video camera to record the tests. When loads were simulated, the truss fell straight down from the girder truss. It was then clear exactly what had happened on the jobsite—the wood at the heel of the truss had split due to nail edge distance, and then pulled away from the 3-16d girder nails. The truss failed just like it failed in the field. The test showed that the failure occurred because of the missing hanger that should have been used to attach truss to girder.
The purpose of the second test was to show that if the trusses had been installed properly—with hangers installed before end-nailing the trusses to the girder—there was no possible way the truss could have fallen as a result of a lumber knot or two breaking in the bottom chord.
To disprove the expert’s testimony, the bottom chord of the truss was “modified” in two places, each representing a knot in the original truss. A hole was cut to simulate the broken knot areaand five men climbed on top of the truss to represent about double the load of the worker on the original truss at the time of the accident. The truss did not fail. Next, a cut was made all the way through the hole, and the same five men mounted the truss. It still did not fail.
The steps were repeated at a second location on the truss to show. When the same five men loaded it up, it still did not fail. The test had proven what the client and Grundahl hypothesized; knots in the bottom chord did not cause the failure.
Testing Results Like DNA
At the trial, the client’s attorneys presented video and pictures from the tests to the jury. The clear visuals from the tests and the summarized results created a very real-life picture of how the accident on the jobsite occurred.
The jury deliberated for less than 40 minutes before reaching their verdict: 11 to 1 in favor of Qualtim’s client. “The ability to recreate the accident in SBCRI quite frankly saved my company. Allowing the facts to speak for themselves was critical,” said the company’s owner. The jury found the Plaintiff and the Deceased each 50% at fault.
