When hurricanes howl, the greatest danger to people and property is flying debris. Researchers for the Wind Engineering Research Center at Texas Tech University have proof that concrete walls are strong enough to withstand flying debris from hurricanes and tornadoes. According to their findings, homes made of concrete are much more storm-resistant than houses constructed of wood and steel.
To duplicate hurricane-like conditions in the laboratory, researchers shot wall sections with 15-pound 2 x 4 lumber "missiles" at up to 100 mph, simulating debris carried in a 250 mph wind. These conditions cover all but the most severe tornadoes. Hurricane wind speeds are less than the speeds modeled here. Missile tests designed to demonstrate damage from hurricanes use a 9-pound missile traveling about 34 mph. Researchers tested 4 x 4-foot sections of concrete block, several types of insulating concrete forms, steel studs, and wood studs to rate performance in high winds. The sections were finished as they would be in a completed home: drywall, fiberglass insulation, plywood sheathing, and exterior finishes of vinyl siding, clay brick, or stucco.
All the concrete wall systems survived the tests with no structural damage. Lightweight steel and wood stud walls, however, offered little or no resistance to the "missile." The 2 x 4 ripped through them.
Reinforced concrete homes have proven their wind-resistance in the field during tornadoes and hurricanes. In Urbana, Illinois, a recently constructed insulating concrete form home withstood a 1996 tornado with minimal damage. In the Liberty City area of Miami, several concrete form homes survived Hurricane Andrew in 1992. In both cases, neighboring homes were destroyed.
Monolithic Domes, which are made of concrete and rebar, have proved especially strong. The sturdy concrete construction combined with the dome shape make these innovative homes nearly impervious to tornadoes, hurricanes, and earthquakes.
Points to Remember in Building a Home that can Withstand Storms
- Architectural plans should be checked to confirm that a two-story home has connections between the first and second story and that everything above the first floor is anchored securely to the foundation.
- Remove any metal, stone or large decorations from the exterior design. These will become projectiles in strong winds.
- The loss of the roof will mean severe damage to the home. Money spent on additional roof improvements will result in the most safety. Avoid long, heavy shingles and tiles in roof construction. Select flat, light shingles for roofing materials. Secure fastening is essential to keeping the roof attached to the walls of the home.
- For the most protection, select impact-resistant windows designed for hurricanes.
- Steel doors should be attached to a secure frame with at least three hinges. Commercial rated deadbolts are the strongest against winds. Install an additional bolt to the top door frame. Sliding patio doors are not safe in tornado winds. Install one door with plastic glazing and steel construction in place of a large slider door.
- A garage door ripped from the building will allow winds to create damage. Even with metal stiffeners, double garage doors will be at risk in tornado winds. Two heavy-duty, single-car garage doors are preferable to one large door.
- The foundation is the key to securing the house, and all bracing and anchoring should attach to it.
- A home built for tornado protection offers a basement, shelter, or other room below ground. A separate safe room is the safest place in a tornado. It must have at least a tornado strength metal door, thick ceiling and secure walls. Objects and debris may be hurled at the room from all sides, so all materials must be rated as tornado safe.
Understanding a Tornado
A tornado is a violently rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud. They are often referred to as twisters or cyclones. However, the word cyclone is used in a wider sense in meteorology for closed low pressure circulation. Tornadoes come in many shapes and sizes, but they are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust. The most extreme tornadoes can attain wind speeds of more than 300 miles per hour.
Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes occur in the Tornado Alley region of the United States, although they can occur nearly anywhere in North America. They also occasionally occur in south-central and eastern Asia, northern and east-central South America, Southern Africa, northwestern and southeast Europe, western and southeastern Australia, and New Zealand. Tornadoes can be detected before or as they occur through the use of Pulse-Doppler radar by recognizing patterns in velocity and reflectivity data, such as hook echoes or debris balls, as well as by the efforts of storm spotters.
Recently, a tornado, with peak winds estimated at 210 miles per hour struck Moore, Oklahoma and adjacent areas killing 23 people and injuring 377 others. The tornado was part of a larger weather system that had produced several other tornadoes over the previous two days. Despite the tornado following a roughly similar track to the even deadlier 1999 Bridge Creek–Moore tornado, very few homes and neither of the stricken schools had purpose-built storm shelters.
Though tornadoes can strike in an instant, there are precautions and preventative measures that people can take to increase the chances of surviving a tornado. Authorities such as the Storm Prediction Center advise having a pre-determined plan should a tornado warning be issued. When a warning is issued, going to a basement or an interior first-floor room of a sturdy building greatly increases chances of survival. In tornado-prone areas, many buildings have storm cellars on the property. These underground refuges have saved thousands of lives.
Some countries have meteorological agencies which distribute tornado forecasts and increase levels of alert of a possible tornado, such as tornado watches and warnings in the United States and Canada. Weather radios provide an alarm when a severe weather advisory is issued for the local area, though these are mainly available only in the United States. Unless the tornado is far away and highly visible, meteorologists advise that drivers park their vehicles far to the side of the road and find a sturdy shelter. If no sturdy shelter is nearby,getting low in a ditch is the next best option. Highway overpasses are one of the worst places to take shelter during tornadoes, as the constricted space can be subject to increased wind speed and funneling of debris underneath the overpass.