OK City Data Center Built To Withstand Winds Up To 310 MPH, Says Contractor 139
dcblogs writes "The area around and to the southwest of Oklahoma City, where more tornadoes were striking Friday night, 'has perhaps the greatest frequency of tornadoes in the U.S.,' said John Snow, a professor of meteorology at the University of Oklahoma. About 95% of all tornadoes are below EF3 intensity, and only 0.1% achieve EF5, which is what hit Moore earlier this month. To build a data center capable of surviving an EF3, Perimeter Technology in Oklahoma City surrounded the raised floor portion of the data center with 8.5-in. reinforced concrete walls. The data center is in the middle of the building, and around it are offices protected by another 8.5-in. exterior wall. But there's another data center in Oklahoma City that may be able survive 310 MPH winds. The company, Devon Energy, isn't talking about its data center or even confirming that it has one capable of handling these winds. But a contractor has disclosed details."
Not that impressive. (Score:5, Informative)
Go google for FEMA P-361 or P-320 and you'll get all the data and construction drawings.
There are two aspects of design here: the first, particularly for smaller structures like safe rooms in houses, is resistance to projectiles. The standard projectile for testing is a 15 lb 2x4 going 100 mi/hr. Texas Tech has a cannon that shoots them for testing. They've done a lot of analysis and review of actual tornadoes and have determined that this is the appropriate projectile: resist that, and you'll resist almost anything else from storms bigger than any actual recorded. Big stuff goes slower, small stuff goes faster, but it's all about momentum and impact pressure, and just like medieval knights, a heavy long skinny thing going fast is an effective projectile.
the second aspect is the force of the wind pushing the wall over, which is a big deal for larger structures (think gymnasiums, auditoriums, etc.). There, you design for the 250/300/350 mi/hr wind or whatever. 250 mi/hr = 160 lb/square foot. Note that in states like California, you probably already have this for free, because you have to design for seismic loads, which are comparable.
As to the school that was destroyed. It was built a long time ago. Retrofits of big structures are expensive. It takes a series of disasters to motivate compliance. In California, the Long Beach quake of 33 resulted in the Field Act (no unreinforced masonry in schools) but still, Sylmar in the 71 resulted in several catastrophic failures of things like hospitals. So the laws were updated to apply to more things. Loma Prieta and Whittier prompted even more.. in fact, I think Whittier is when they really started cracking down on reinforcing masonry, and not allowing existing structures to be grandfathered. Northridge in 94 also resulted in some changes, particularly for things like bolting houses to foundations.
But the point here is that it took 80 years from the first laws about earthquake resistance to the present day, where most stuff is just built to take it. A Civil Engineer being interviewed in Joplin MO commented that making a new hospital tornado resistant only added about 3% to the cost. Doing it as a retrofit is a lot more expensive. Consider an elementary school with 500 students: their annual budget is around $3.7M (http://www2.census.gov/govs/school/11f33pub.pdf, $7600/student) A very tiny fraction of that is available for construction projects, I'd be surprised if it's 1%. You're not going to retrofit a school built in the 60s out of concrete blocks and no rebar for $40k, or even $400k. FEMA estimates that a single family shelter would cost about $5000 to build. Building something to hold 500 students plus 60 staff is a big project: at 5 square feet/person, that's several thousand square feet, and you need to have enough doors for getting those 600 people in and out. And that's 3000 square feet that has to be kept fairly open: no using it for storage. (multipurpose rooms and cafeterias are popular). The other problem is that safe rooms are, by nature, kind of depressing places to be in: they have no windows and limited doors.
Re:Domes (Score:5, Informative)
That's a myth. Both of those things can be overcome [npr.org] quite easily (yeah their example links to a business site but it doesn't make it untrue). It's perpetuated by the old, 'well everyone says so' bullshit. The reality is that builders don't have to dig deep because the frost line is not deep there and building codes say you don't have to dig deep. So it makes it cheaper to build if you don't dig a deep foundation like a properly built basement, with rebar reinforced concrete walls and floors and well drained gravel backfill outside like is done in more northerly parts of the country.
Southern Ontario has a lot of heavy red clay. I don't know anyone growing up, who didn't have a basement (I don't live there now). A lot of places have it. And you want to talk about expansion and contraction, look at Manitoba and Saskatchewan (with similar great plains/prairie soil). Especially Winnipeg which is build in a flood plain along the banks of a large (the Red) river. Talk about potential for water. The frost line is around 10 or 12 feet deep. That is a lot of depth for expansion and contraction (it's called frost heave). Every home practically has a basement there. And they have a technology called 'water proofing' now. It works on basements too. Seriously, only a retard would build a new house in Oklahoma (and the rest of tornado alley) without a basement that has at least a part with a cement cover. FWIW the 'showme' part of my nick comes from the fact I used to live in Missouri. I know the sound of the siren. And they have a lot of places without basements there too. Ridiculous.