Video: U of Alabama Wood Panel Testing; Ductility Concerns

Originally published by the following source: SBC MagazineApril 17, 2019
by SBCA Staff with contributions by SBCA/SBCRI Professional Engineers

   

There is a wide array of promotional efforts taking place in the market every day, making discernment key for all of us as we consume information. As you read a promotion or view a video, consider asking yourself:

  1. Is there a goal, point of view or agenda being advocated?
  2. Is there any type of conflict of interest or bias?
  3. Is the data or article well referenced, and as such, credible?
  4. Are the facts presented fairly and are all points of view represented?

Shear wall performance tests by Clemson University and the University of Oklahoma have been promoted as authoritative sources of wood structural panel (WPS) performance testing.

Presumably, testing performed by University of Alabama’s engineering department, in its Large Scale Structures Laboratory, is equivalently credible. The two WSP seismic performance videos provide an interesting perspective on wood structural panel ductility under very small amounts of observable deflection.

Video 1: Small Scale Segmented WSP Seismic Testing in Rigid Test Frame

Video 2: 40 foot Perforated WSP Seismic Testing in Rigid Test Frame. Forward to just after three minutes to view the testing or watch this video to start at the testing section.

The videos provide a fascinating display regarding the:

  1. Rigidity of wood structural panels,
  2. Stress this rigidity places on nailed connections,
  3. Importance of fastening systems to overall performance of any product,
  4. Instant destruction testing can cause depending on how a test is performed and its objective.

Using photos and videos without a complete assessment of the underlying purpose and/or being allowed to evaluate the actual test data is an inadequate and restrictive method for determining actual product performance characteristics. For university, federal government and public non-governmental organizations, information transparency should be readily available. For protected intellectual property, the professional evaluation process exists via professional engineering and ANSI ISO/ISE 17065 accreditation.

As established by PhD thesis testing and accepted engineering practice, design values generated depend on the test method, gravity load applied and all load path connection systems. For more information on wall bracing design value variability, please review the following two articles: APA - IRC Allowable Design Values for OSB Wall Bracing = 175 PLF and OSB Bracing Design for IRC? APA & AWC Say “Not Sure”.  

Testing based on the scientific method is the only accurate way to create a fair comparison. In other words, hold the test apparatus, personnel, applied load, and all other variables/boundary conditions constant. To assess a hypothesis of equivalency one needs to compare the control sheathing to the new sheathing, where all else is identical from one test to the next. This will answer the hypothesis (e.g. new straw sheathing is equivalent to OSB or not).

The moral of this story is to treat university testing with great discernment especially in light of these two videos. It is often difficult to understand critical product performance aspects, good or bad, from general reports, photos and videos. It may not be obvious that the goal of the test was to:

  1. Stimulate controversy and generate more university test funding, or
  2. Provide credibility for a given point of view for promotional purposes, if the right testing answer is generated.

Fundamental principles, which can be used, to discern the credibility of testing and analysis include, but are not limited to, the following questions:

  1. Is the testing performed by an ISO/IEC 17025 accredited testing facility?
  2. Who is funding the testing?
  3. Does the group that owns the test facility also perform a marketing function for the products they are testing?
  4. Does the testing agency also market the product being tested and would that be a conflict of interest?

Finally, if you desire performance truth, have a professional engineer stand behind the testing and analysis by sealing and signing their work. This carries code compliance benefits and typically professional liability insurance, where legal costs are not unknowingly being shifted onto you.

For additional information on the performance of wood structural panel, please visit the following webpage on OSB as a Raw Material.