Questionable Engineering Design
Questionable Engineering Design
(OP)
From the internet headlines today:
"TODAY - May 01, 2010
(picture)
Deadly tornadoes rip through Arkansas Twisters hit central Arkansas, injuring dozens, destroying homes, and taking down power lines. Details
Arkansas tornadoes
Derby forecast improves
Your local weather"
There was a picture here I could not post of a collapsed fire station with a fire truck inside. It was a CMU building with a wood roof.
Personally, other than money, I cannot understand the logic for allowing this type of construction in a tornado prone region. Now, in the emergency condition it was designed for, the fire truck cannot do it's job.
In my opinion, it should have been constructed of CIP concrete walls with a CIP concrete roof, and blow out windows to relieve the pressure. The outcome should have been much better. To me, it's just irresponsible engineering design with a lack of forethought.
Thoughts?
"TODAY - May 01, 2010
(picture)
Deadly tornadoes rip through Arkansas Twisters hit central Arkansas, injuring dozens, destroying homes, and taking down power lines. Details
Arkansas tornadoes
Derby forecast improves
Your local weather"
There was a picture here I could not post of a collapsed fire station with a fire truck inside. It was a CMU building with a wood roof.
Personally, other than money, I cannot understand the logic for allowing this type of construction in a tornado prone region. Now, in the emergency condition it was designed for, the fire truck cannot do it's job.
In my opinion, it should have been constructed of CIP concrete walls with a CIP concrete roof, and blow out windows to relieve the pressure. The outcome should have been much better. To me, it's just irresponsible engineering design with a lack of forethought.
Thoughts?
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask






RE: Questionable Engineering Design
Or could it read "Concrete roof collapses and destroys fire trucks". just a thought?
RE: Questionable Engineering Design
) for instrumentation (aerospace industry). About 2 weeks later there was an accident becuase of a gas leak.
The cloud of hydrogen over the building ignited. The pressure blew the wood frame roof in and created over $1,000,000 in damage. The building was designed well above all the standards for pressure and exposure. The walls survived with a problem. Several "explosion proof/bullet proof windows" that were 4" thick where blown in and steel door was also destroyed, but he CMU walls had no problems.
It is not a question of the materials but the judgement of the professional in determining the possible load conditions for the building use. - At the time, I had only been out of school for 1 month, but I should have learned after seeing rocket test stand total destroyed on my first observation.
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Questionable Engineering Design
Good point. Here in Florida we have certain buildings that are designed way beyond the code requirements....hurricane shelters, emergency service centers (including SOME fire stations, but not all), emergency communications facilities and towers,etc. I've done strengthening design on two hurricane shelters taking them from code (120-130 mph) to Cat 5 hurricane (155 mph +).
In my opinion, certain emergency services and shelters should be taken beyone typical code requirements in areas where the probability is high of such an event (Hurricane prone area, tornado alley, etc.).
Ron
RE: Questionable Engineering Design
It's no different from the fact that my parent's house, which is only 84 yrs old is grandfathered to the electrical code of the time, which didn't require grounding wires, and didn't preclude aluminum wiring, and didn't preclude fusible link fuses. Likewise, the house has no sprinkler system. To retrofit would require gutting the house, and spending probably $100k for only a potential problem.
I've had similar thoughts every spring, when regions of the south and midwest experience flooding; why don't they build on stilts? Obviously, the cost, evne though the houses are relatively inexpensive there, compared to SoCal, but when compared to the standard of living, a retrofit would essentially might require a complete demo and rebuild.
TTFN
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RE: Questionable Engineering Design
Garth Dreger PE
AZ Phoenix area
RE: Questionable Engineering Design
I'm not saying that it _shouldn't_ be used.
Mike Halloran
Pembroke Pines, FL, USA
RE: Questionable Engineering Design
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Questionable Engineering Design
Garth Dreger PE
AZ Phoenix area
RE: Questionable Engineering Design
RE: Questionable Engineering Design
Heck, we even have an occasional F1 in the Puget Sound area, but never anything higher. I guess I was thinking more of those regions regularly seeing F3 and above.
I still think though that these emergency structures should be at least partly bermed at the first story, with an earth cover over if only one story. To me, it just seems prudent.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Questionable Engineering Design
RE: Questionable Engineering Design
RE: Questionable Engineering Design
The building codes do not specify tornado loads, since doing so would be unnecessarily burdensome. Should a tornado occur, an EF1 will decommission a fire truck in the station just about as certainly as an EF5. If we mapped the probably that our homes and businesses would be hit by any tornado, the probability would be nearly zero.
In a system safety analysis, we would assess the combination of probability and severity for foreseeable events. In this case, one would project a severity of "critical" to "catastrophic" occurring with probability of "remote" to "improbable", for a risk assessment which requires acceptance at the lowest level, but little else.
If you live in tornado alley, you may or may not consider such things when buying a house. With the virtual absence of tornado-resistant housing, it is apparent that we simply accept that something might happen, but we figure it won't happen to us.
RE: Questionable Engineering Design
RE: Questionable Engineering Design
RE: Questionable Engineering Design
RE: Questionable Engineering Design
Plate connected wood trusses are an adequate construction material, but as with many things we are asked to design and build, they are typically built to the least strength necessary. This is a function of the designer, and the overall structural system design, and can easily be overcome by better selection of loading schemes, and better selection of structural features to increase structural toughness.
As for the cost of building more robust structures, public projects (and most commercial projects) typically require an engineer, so that cost should be there using any material. Reinforced concrete is not significantly more expensive than other materials, when the entire envelope is considered, but it does require the right contractors. As you point out, wood structure is easy to build to a level good enough for most users. And most "local builders" are familiar with wood, but not with proper construction methods for engineered structures.
RE: Questionable Engineering Design
RE: Questionable Engineering Design