Building Materials are Key to Limiting Storm Deaths
The images have become all too familiar: houses and communities turned into piles of giant toothpicks by fierce tornadoes. Much of this kind of damage can be prevented by enacting stronger building standards.
The first week of March had an unprecedented 440 tornado warnings issued, and severe storms contributed to the deaths of 39 people in five states. A perfect blend of energy and turbulent winds has already made 2012 an especially active, and deadly, year for tornadoes. In early April, tornadoes tore through the Dallas-Fort Worth area and caused as much as $500 million in insured damage, according to the Southwestern Insurance Information Service.
Tornadoes cause an average of 70 fatalities and 1,500 injuries in the U.S. each year, according to the National Oceanic and Atmospheric Administration. Over the last decade, these numbers have steadily risen. In 2011 there were 1,897 tornadoes reported in the U.S., of which at least 1,706 were confirmed. It proved to be a destructive and deadly year for tornadoes, with 550 confirmed fatalities. If the first quarter of 2012 is an indicator of things to come, it will be as deadly a year as the last.
For cities and towns, the message is clear: Take steps now to ensure that new residential and commercial structures are built to withstand extreme weather conditions.
There is a reason why those photos and videos of tornado damage often look like giant piles of sticks. Wood-frame houses with weak veneer exteriors, such as wood siding, artificial wood siding and artificial stucco, are no match for severe windstorms. In fact, when struck by a tornado, the wood in these buildings becomes deadly airborne unguided missiles or flying debris, the main cause of deaths and injuries suffered during tornadoes.
Research at Texas Tech University and elsewhere has shown that only masonry or reinforced concrete walls can protect against lethal flying debris that might be encountered during a tornado with wind speeds up to 130 mph.
Masonry veneer provides better protection than non-masonry materials, but vertically reinforced masonry walls and total masonry construction, which is standard around the world, with the exception of the U.S., is even better. That is why public schools are often built with total masonry construction, consisting of reinforced concrete block interior walls and masonry exterior walls.
In severe windstorms, the weight of the masonry or reinforced concrete helps resist uplift and lateral loads, and heavy materials often stop windborne debris that could damage the building or injure and even kill people. To prevent failure during severe wind events, masonry walls must be securely tied to all other building components. They also are reinforced and/or grouted to create higher mass. Doing so provides increased resistance to uplift and lateral wind loads and allows the wall to serve as protection from flying debris.
With total masonry construction, there is no wood framing. The walls are solid masonry, one to two feet thick. This affords many advantages. And even with traditional wood framing that is covered with a masonry veneer such as brick, the structure is much safer in 130 mph winds, as demonstrated in the Texas Tech projectile tests.
In states such as Texas, Oklahoma and Kansas, extreme weather is a fact of life. Building safety is fast becoming the most important issue.
In Texas alone, more than 150 cities have recognized the many benefits that masonry exteriors provide and have incorporated masonry requirements into their zoning ordinances and construction standards. The right building materials are important, not only in terms of durability, but also to prevent loss of life and reduce injury during a severe weather event.
City planners, managers and elected officials can do more to safeguard their constituents. The facts are there. Cities across Texas must adopt masonry construction requirements now in order to help prevent injury and death in the future.
Resource: Mukaddes Darwish – Updated 08:30 p.m., Friday, May 11, 2012
Darwish is an associate professor of construction engineering and engineering technology at Texas Tech University.