With the rash of tornadoes that swept through the south in the past two days, my memory takes me back to my days growing up in this country’s heartland – where severe weather and tornado warnings were a weekly occurrence every Spring. In fact, one of my earliest memories was being taken home from grade school in a rowboat after one of those sudden storms.
Flood in Paducah in 1964
About seven years ago, I was asked to do a very special project in that part of the country – to design a data center in Oklahoma that was capable of withstanding the impact of an F5 tornado. The site was on an open hill along Interstate 35 and visible for more than 5 miles in all directions. People who lived in the area said that from our site, we should expect to see a tornado about once each year.
Hidden within a large distribution center, this data room doubles as a tornado shelter for the 120 people who worked elsewhere in the building. To protect the people (and equipment), we could have no wall openings larger than a quarter, and the doors, walls, and concrete interior roof were highly reinforced. Working with RTB Engineers, the room was designed to withstand a near-vacuum pressure of 1 PSI – plus the impact from the adjacent 40-foot concrete walls which might fall.
This is certainly an extreme example of weather-related design and hopefully that design will never be field-tested. There are however many everyday weather issues with buildings that are important for architects to understand. Some weather elements can be harnessed and put to good use: natural ventilation, passive solar capture, controlled natural light, recycled rainwater, and panels that generate electricity or heat water. These should be part of any sustainable building strategy.
Weather can also be destructive. Ultra-violet waves in sunlight break down many materials we use in building. The sudden swings in Virginia temperatures require our attention in construction detailing. Excessive rain and snow can burden a roof to collapse. An unusually heavy downpour can flood a building if the path for the runoff isn’t considered properly.
Wind is usually the most important design consideration for architects and engineers. Roofs are the most vulnerable part of any building. The upward forces from high winds can literally peel a roof off and pull attached columns out of the ground.
Image of a ravaging tornado
Design-speeds vary by region but are typically higher along coasts because of hurricanes. Owner’s insurance companies will often require increased design to reduce liability. In non-coastal cities like Richmond, a 90 mile-per-hour wind design-speed is the standard. Since hurricanes or tornadoes can have winds in excess of 200 MPH, very little of what we build can resist that sort of force.
Human tragedy and loss of property follow these natural weather extremes. Our design standards do not match this level of power – nor should they. It is not practical or reasonable to design
for every possible circumstance.
Rather than live in bunkers, our society chooses to live within nature so we may enjoy its benefits and witness its beauty. In the end, we must accept some risks and the occasional tragedy that comes with that partnership.
- Mark Larson, AIA, principal
