Tornado Season & Collapse, Are Building Materials to Blame?
In early 2014, a video of the Brier Creek Multifamily building collapse went viral. The cause for the collapse was straight-line wind gusts of approximately 86 mph. Not surprisingly, the video generated significant media attention.
In the last year, weather systems throughout Tornado Alley have had a significant impact on the built environment. Any natural disaster causes severe stress on buildings, so blaming specific building materials for a structural collapse is disingenuous at best, sensationalism for certain, and unprofessional at its worst.
Some of the questions that need to be honestly addressed follow; they include but are certainly not limited to:
- Was the building built to code?
- Is there any possibility of benchmarking building performance? For example:
- Does one building built identically to another perform differently?
- Why did it perform differently?
- Different weather conditions?
- Different methods of connections?
- Different building orientation?
- Different window and door conditions?
- Are there two similar houses in the wind zone to study, one that has performed well and another less well? Easier then to isolate why and potential remedies.
There will be numerous reports on high wind event damage in the forthcoming months. Some will be credible while others may use the situation to take a particular product or application to task, while promoting a point of view. Most of the time, a critical review of authorship provides insight into the goals and objectives driving articles, research reports and educational programs. In the process of discernment, it is reasonable to ask: is there a conflict of interest?
Using photos and videos without an appropriate onsite damage assessment is a poor and limiting method for determining the cause of a partial or total collapse. In most cases, engineers can point to one of several common weak links as the cause of structural failure. It's often found that structural failure following a high wind event is due to a lack of adequate connections. A continuous load path and accurate connections, from the roofs to walls and floors to walls and then to the foundation, must be provided for reliable building performance.
The most commonly observed reasons for failure include:
- Inadequate roof-to-wall connections
- Improper anchor bolt connections attaching walls to the foundation
- Poor sheathing fastening
- Use of the wrong nail type
- Breaches due to failure of windows, garage doors, or cladding/wall systems that result in wind pressure induced failure
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.