Evaluating Buildings to Identify Best Possible Refuge Areas
I was fortunate to be able to attend a seminar given by the State of Missouri Emergency Management Agency (SEMA) and the Federal Emergency Management Agency (FEMA) on “Evaluating Buildings to Identify Best Possible Refuge Areas”. This was an all day seminar that culminated in breaking into small groups to complete an actual evaluation of a school in Wichita Kansas.
2 structural engineers from the east coast + one individual from SEMA gave the presentation. We began by reviewing damage caused by high winds/tornado’s from several recent storms. The graph of storm related damage from the past 50 years shows a significant upswing in storm related damage and injuries. We also reviewed test data from the labs at Texas Tech showing testing of various assemblies for their ability to stop storm debris (standard testing involves firing a 15 lb 2×4 from an air cannon). Assemblies designed to provide fire resistance, such as a metal stud/drywall 2 hour rated wall provide almost no resistance in this test. As one of our instructors said, “it’s like a hot knife through butter”.
There were several important takeaways from this course. The first would be to evaluate for “continuous load path”. In a high wind storm event, buildings are subjected to loading running counter to what is experienced normally. Where we architects are normally concerned with gravity loads (an wind loading – more on that later), during a tornado parts of the building are pulled upward. High winds moving over a roof cause uplift, tearing the roof off it’s frame. Pressure differentials can cause buildings to explode from the inside out. And that old wives tale about opening the windows to equalize the pressure is just that.
We also learned about FEMA’s guidelines for square footage per person in a refuge area (5SF/person – 10SF for wheelchair users) and briefly went over FEMA guideline 320 for design and construction of Safe Rooms.
This was an excellent presentation. If you have the opportunity, I would highly recommend attending