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A storm shelter or storm cellar is a type of underground bunker designed to protect the occupants from severe weather, particularly tornadoes. They are most frequently seen in the Midwest ("Tornado Alley") and Southeastern ("Dixie Alley") United States where tornadoes are generally frequent and the low water table permits underground livings.
An average storm cellar for a single family is built close enough to the home to allow instant access in an emergency, but not so close that the house could tumble on the door during a storm, trapping the occupants inside. This is also the reason the main door on most storm cellars is mounted at an angle rather than perpendicular with the ground. An angled door allows for debris to blow up and over the door, or sand to slide off, without blocking it, and the angle also reduces the force necessary to open the door if rubble has piled up on top. The floor area is generally around eight by twelve feet (2.4 by 3.7 m), with an arched roof like that of a Quonset hut, but entirely underground. In most cases the entire structure is built of blocks faced with cement and rebar through the bricks for protection from the storm. Doing so makes it nearly impossible for the bricks to collapse. New ones are sometimes made of septic tanks that have been modified with a steel door and vents. Some new shelters are rotationally molded from polyethylene.
Most storm cellars are accessible by a covered stairwell, and at the opposite end of the structure there can be conduits for air that reach the surface, and perhaps a small window to serve as an emergency exit and also to provide some light. Storm cellars, when connected to the house, may potentially compromise security. [1]
Fully enclosed underground storm shelters offer superior tornado protection to that of a traditional basement (cellar) because they provide separate overhead cover without the risk of occupants being trapped or killed by collapsing rubble from above. For this reason they also provide the only reliable form of shelter against "violent" (EF4 and EF5) tornadoes which tend to rip the house from its foundation, removing the overhead cover which was protecting the occupant.[ citation needed ]
There are several different styles of storm cellars. There are the generic underground storm/tornado cellar, also called storm or tornado shelters, as well as the new above-ground safe rooms. A "cellar" is an underground unit, but for the sake of the specified use of a "storm cellar" to protect one from high-wind storms, it seems relevant to mention saferooms. There are two basic styles of underground storm cellars. One is the "hillside" or "embankment" and the other is the "flat" ground.
One other style of shelter is the under garage. [2] While similar to other underground shelters, its main difference is that it is installed in a garage rather than outside. Having it installed in the garage allows access to it without having to go outside during a storm. It is sometimes not an option to have a shelter installed outside either due to insufficient space, or local ordinances.
Hillside or embankment models are usually installed in one of two ways. It can be installed in an existing hill/embankment or dirt is built up around a freestanding unit, forming a hill around it. The door can be set at an angle or vertically. There can be steps leading into the unit, or it can be installed to where the floor is level with the ground outside. The embankment storm cellar can be made from concrete, steel, fiberglass, or any other structurally sound material or composite and is usually installed in a hill or embankment, leaving only the door exposed. In some situations, they can hold an entire neighborhood or town as with a community shelter. More often, they are built to hold one or two families, specified as a residential shelter. All underground "storm or tornado" shelters must be properly anchored.
Above ground shelters are used in many areas of the country and by a wide variety of homeowners and businesses. Groundwater tables may make it impossible to install or build a shelter below ground, elderly or people with limited mobility may be unable to access a below ground shelter, or people may have significant phobias pertaining to below ground sheltering. FEMA P-320, Taking Shelter from the Storm: Building a Safe Room for Your Home or Small Business (2014) [3] and ICC/NSSA Standard for the Design and Construction of Storm Shelters [4] provide engineering and testing requirements to ensure that above ground shelters manufactured to the published specifications will withstand winds in excess of 250 mph (400 km/h) (EF5 tornado). Above ground shelters may be built of different materials such as steel reinforced concrete [5] or 1/8" 10 ga. hot rolled steel and may be installed inside a home, garage, or outbuilding, or as a stand-alone unit. These types of shelters are typically prefabricated and installed on a home site or commercial location. Walls can be provided which form a deflector baffle entry so that the path of the storm debris must touch two impact resistant surfaces before it penetrates into the protected area of the occupants. [6] [7]
Wind engineering specialists from Texas Tech University's National Wind Institute have done extensive research that concludes that sheltering in an above ground storm shelter that meets the engineering criteria outlined in FEMA Pub. 320 and 361 and ICC/NSSA Standard for the Design and Construction of Storm Shelters is as safe as seeking below ground shelter during massive EF4 and EF5 tornadoes. TTU engineer Joseph Dannemiller presented the research findings at a TEDxTexasTechUniversity symposium in February 2014. [8]
The below-ground shelters are designed so that the door is flat with the ground and can be made from any one of the materials previously described. This unit is put in a hole deep enough to cover the bottom section, and then the excavated dirt is filled in around the top and packed down. Storm shelters must be designed, built, tested, and installed properly for them to meet any of the US FEMA-320, [3] FEMA-361, [9] ICC-500, [10] NPCTS (National Performance Criteria for Tornado Shelters), or ICC/NSSA Standards.
Many storm shelter manufacturers include geolocation services or incorporate GPS technologies to assist in ensuring recovery from the shelter after a storm or other catastrophic event. In addition, shelter owners may opt to incorporate their own geolocation services in their shelter. Shelter owners can provide their shelter's GPS coordinates to an emergency response center that is linked to a nationwide severe weather notification system. If a storm occurs, the emergency response center places a phone call to the shelter owner and then secondary contacts, lastly contacting local emergency response if unable to contact the shelter owner. [11]
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Functionally underground bunkers, storm cellars are readily provisioned as bomb shelters and/or fallout shelters (although they are not usually dug as deeply or equipped with filtered ventilation, respectively). Too, since their underground construction makes them steadily cool and dark, storm cellars on farmsteads in the Midwest and elsewhere have traditionally used as root cellars to store seasonal canned goods for consumption during the winter.
A bunker is a defensive military fortification designed to protect people and valued materials from falling bombs, artillery, or other attacks. Bunkers are almost always underground, in contrast to blockhouses which are mostly above ground. They were used extensively in World War I, World War II, and the Cold War for weapons facilities, command and control centers, and storage facilities. Bunkers can also be used as protection from tornadoes.
Air raid shelters are structures for the protection of non-combatants as well as combatants against enemy attacks from the air. They are similar to bunkers in many regards, although they are not designed to defend against ground attack.
A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. Especially in residential buildings, it often is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, car park, and air-conditioning system are located; so also are amenities such as the electrical system and cable television distribution point. In cities with high property prices, such as London, basements are often fitted out to a high standard and used as living space.
A blast shelter is a place where people can go to protect themselves from blasts and explosions, like those from bombs, or in hazardous worksites, such as on oil and gas refineries or petrochemical facilities. It differs from a fallout shelter, in that its main purpose is to protect from shock waves and overpressure instead of from radioactive precipitation, as a fallout shelter does. It is also possible for a shelter to protect from both blasts and fallout.
The National Wind Institute (NWI) at Texas Tech University (TTU) was established in December 2012, and is intended to serve as Texas Tech University's intellectual hub for interdisciplinary and transdisciplinary research, commercialization and education related to wind science, wind energy, wind engineering and wind hazard mitigation and serves faculty affiliates, students, and external partners.
A safe room or panic room is a fortified room that is installed in a private residence or business to provide a safe shelter, or hiding place, for the inhabitants in the event of a break in, home invasion, tornado, terror attack, or other threat. Safe rooms usually contain communications equipment, so that law enforcement authorities can be contacted.
The term FEMA trailer, or FEMA travel trailer, is the name commonly given by the United States government to forms of temporary manufactured housing assigned to the victims of natural disaster by the Federal Emergency Management Agency (FEMA). Such trailers are intended to provide intermediate term shelter, functioning longer than tents which are often used for short-term shelter immediately following a disaster. FEMA trailers serve a similar function to the "earthquake shacks" erected to provide interim housing after the 1906 San Francisco earthquake.
Tornado intensity is the measure of wind speeds and potential risk produced by a tornado. Intensity can be measured by in situ or remote sensing measurements, but since these are impractical for wide-scale use, intensity is usually inferred by proxies, such as damage. The Fujita scale, Enhanced Fujita scale, and the International Fujita scale rate tornadoes by the damage caused. In contrast to other major storms such as hurricanes and typhoons, such classifications are only assigned retroactively. Wind speed alone is not enough to determine the intensity of a tornado. An EF0 tornado may damage trees and peel some shingles off roofs, while an EF5 tornado can rip well-anchored homes off their foundations, leaving them bare— even deforming large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler radar data, photogrammetry, and ground swirl patterns may also be analyzed to determine the intensity and assign a rating.
Tornado damage to human-made structures is a result of the high wind velocity and windblown debris. Tornadic winds have been measured in excess of 300 mph (480 km/h). Tornadoes are a serious hazard to life and limb. As such, people in tornado-prone areas often adopt plans of action in case a tornado approaches.
A tornado emergency is an enhanced version of a tornado warning, which is used by the National Weather Service (NWS) in the United States during imminent, significant tornado occurrences in highly populated areas. Although it is not a new warning type from the NWS, issued instead within a severe weather statement or in the initial tornado warning, a tornado emergency generally means that significant, widespread damage is expected to occur and a high likelihood of numerous fatalities is expected with a large, strong to violent tornado.
The 1999 Bridge Creek–Moore tornado was a large, long-lived and exceptionally powerful F5 tornado in which the highest wind speed ever measured globally was recorded at 321 miles per hour (517 km/h) by a Doppler on Wheels (DOW) radar. Considered the strongest tornado ever recorded to have affected the Oklahoma City metropolitan area, the tornado devastated southern portions of Oklahoma City, Oklahoma, United States while near peak intensity, along with surrounding suburbs and towns to the south and southwest of the city during the early evening of Monday, May 3, 1999. Parts of Bridge Creek were rendered unrecognizable. The tornado covered 38 miles (61 km) during its 85-minute existence, destroying thousands of homes, killing 36 people, and leaving US$1 billion in damage, ranking it as the fifth-costliest on record not accounting for inflation. Its severity prompted the first-ever use of the tornado emergency statement by the National Weather Service.
Tornadoes, cyclones, and other storms with strong winds damage or destroy many buildings. However, with proper design and construction, the damage to buildings by these forces can be greatly reduced. A variety of methods can help a building survive strong winds and storm surge.
The term "tornado preparedness" refers to safety precautions made before the arrival of and during a tornado. Historically, the steps taken have varied greatly, depending on location, or time remaining before a tornado was expected. For example, in rural areas, people might prepare to enter an external storm cellar, in case the main building collapses, and thereby allow exit without needing rescue from the main building as in urban areas. Because tropical storms have spawned many tornadoes, hurricane preparations also involve tornadoes. The term "tornado preparedness" has been used by government agencies, emergency response groups, schools, insurance companies, and others.
The 2011 Joplin tornado was a large and devastating multiple-vortex tornado that struck Joplin, Missouri, United States, on the evening of Sunday, May 22, 2011. Part of a larger late-May tornado outbreak, the EF5 tornado began just west of Joplin and intensified very quickly, reaching a maximum width of nearly one mile (1.6 km) during its path through the southern part of the city. The tornado tracked eastward through Joplin, and then continued across Interstate 44 into rural portions of Jasper and Newton counties, weakening before it dissipated.
The 2013 El Reno tornado was an extremely large, powerful, and erratic tornado that occurred over rural areas of Central Oklahoma during the early evening of Friday, May 31, 2013. This rain-wrapped, multiple-vortex tornado was the widest tornado ever recorded and was part of a larger weather system that produced dozens of tornadoes over the preceding days. The tornado initially touched down at 6:03 p.m. Central Daylight Time (2303 UTC) about 8.3 miles (13.4 km) west-southwest of El Reno, rapidly growing in size and becoming more violent as it tracked through central portions of Canadian County. Remaining over mostly open terrain, the tornado did not impact many structures; however, measurements from mobile weather radars revealed extreme winds in excess of 313 mph (504 km/h) within the vortex. These are among the highest observed wind speeds on Earth, just slightly lower than the wind speeds of the 1999 Bridge Creek–Moore tornado. As it crossed U.S. 81, it had grown to a record-breaking width of 2.6 miles (4.2 km), beating the previous width record set in 2004. Turning northeastward, the tornado soon weakened. Upon crossing Interstate 40, the tornado dissipated around 6:43 p.m. CDT (2343 UTC), after tracking for 16.2 miles (26.1 km), it avoided affecting the more densely populated areas near and within the Oklahoma City metropolitan area.
A relatively widespread, damaging, and deadly tornado outbreak struck the central and southern United States in late April 2014. The storm complex responsible for the outbreak produced multiple long-track tornadoes – seven of which were deadly, causing 35 fatalities. One additional death occurred in Florida, due to severe flooding associated with this system.
The 2011 Philadelphia, Mississippi Tornado was an extremely powerful and fast-moving multi-vortex tornado that touched down in eastern Mississippi on the afternoon of April 27, 2011. Part of the historic 2011 Super Outbreak, the largest tornado outbreak on record, this was the first of four EF5 tornadoes to touch down that day and the first such storm in Mississippi since the 1966 Candlestick Park tornado. While on the ground for 30 minutes, it traveled along a 28.28-mile (45.51 km) path through four counties, leaving behind three deaths, eight injuries, and $1.1 million in damage.
Atomitat (1962) was an underground bunker-home in Plainview, Texas, designed by architect Jay Swayze. The name of the home came from the combination of the words "atomic" and "habitat". It was the first home in the U.S. to meet civil defense specifications for a nuclear shelter.
The 2011 El Reno–Piedmont tornado was a long-tracked and deadly EF5 tornado that struck central Oklahoma on the evening of May 24, 2011. The tornado impacted areas near or within the communities of El Reno, Piedmont, and Guthrie, killing nine and injuring 181. After producing incredible damage in several locations along a path of more than 60 miles (97 km), the El Reno–Piedmont tornado was given a rating of EF5, the highest category on the Enhanced Fujita scale, as well as being the highest rated tornado on the scale since its implementation in 2007, with estimated peak winds >210 mph (337 km/h). It was also the first tornado rated EF5 or F5 to strike Oklahoma since the 1999 Bridge Creek–Moore tornado. A mobile radar found that the tornado possessed possible wind speeds of up to 295 mph (475 km/h).
The 2011 Rainsville, Alabama tornado was a catastrophic EF5 tornado that struck parts of northeast Alabama on the late afternoon of April 27, 2011. It was the fourth and final EF5 of the historic 2011 Super Outbreak, the largest tornado outbreak ever recorded. The multi-vortex tornado remained on the ground for 36 minutes, carving a path of 36.63 miles (58.95 km) long through DeKalb County, causing 25 deaths, an unspecified yet sizable number of injuries, and an estimated $10+ million in damage. According to storm chaser Maximilian Hagen, this tornado produced some of the most violent damage ever surveyed.
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