Tornados Wreck Havoc in Mid-US, Building Material to Blame?

Originally published by the following source: SBC MagazineJune 3, 2019
by SBCA Staff with contributions by SBCA Professional Engineers

   

Tornado damage in Jefferson City, Mo. as seen on Thursday, May 23, 2019.

Tornado damage in Jefferson City, Mo. as seen on Thursday, May 23, 2019. Photo by David Carson, St. Louis Post-Dispatch.

In the past few weeks, weather systems throughout Texas, Oklahoma, Missouri, Indiana and Ohio have had a significant impact on the built environment. As is well known, tornados cause severe stress on buildings where the high localized wind loading conditions find the weak point of the structure quickly. This usually is at the location of a wood nail, wood connector or anchor bolt connection, or in our testing experience, a knot or slope of grain deviation in a lumber tension member. An interesting point is that most studs in wall systems are meant to see compression forces not tension, where studs in tension may also be a structural weak point.

As the pictures herein attest, finding the key building material weak point that caused the structural performance to be a debris field is challenging, if not impossible, to do.

Tornado damage in Jefferson City, Mo. as seen on Thursday, May 23, 2019.

Tornado damage in Jefferson City, Mo. as seen on Thursday, May 23, 2019. Photo by David Carson, St. Louis Post-Dispatch.

Tornado damage in Jefferson City, Mo. as seen on Thursday, May 23, 2019.

Tornado damage in Jefferson City, Mo. as seen on Thursday, May 23, 2019. Photo by David Carson, St. Louis Post-Dispatch.

Questions that need to be sincerely addressed follow, which include but are certainly not limited to:

  1. What were the as-built conditions?
  2. Was the building built to code?
  3. Which aspects of the structure were built to code?
  4. Which aspects of the structure were not built to code?
  5. What is the cause/effect analysis for each code compliant and each non-code compliant condition?

It is obvious that proper construction implementation is key to satisfactory building material performance. Paying close attention to all connecting systems that make up the load path is essential.

The most important outcomes of poor building performance in a high wind or seismic event are that no one gets hurt; the construction industry continues to learn and evolve; and design and installation best practices improve.

The entire construction industry can greatly benefit by staying focused on providing framer-friendly details that are easy to understand and implement. It’s critical that we come together with the goal of fostering innovation, using accepted engineering practice, creating installation best practices, working closely with professional framers and assisting building departments to focus inspections on key load path elements. We all are educators. By working together, we will significantly improve the built environment.   

The following drone footage, captured May 23, shows the stark aftermath of a tornado that hit Jefferson County, MO. 

For additional information on the performance of wood structural panels, please visit the following webpage on OSB as a Raw Material and the following articles on performance of building materials in high winds and as tested.