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RE: journalist query - factors of safety

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By no means do I claim to be an expert in dams or levee design, but that seems low. A plain old retaining wall you see in someone’s back yard (3 feet or higher above ground) by code must have a safety factor of 1.5 for sliding and overturning.


In structural engineering, our codes have built in safety factors that attempt to take into account material quality, construction quality, and other factors. I’m sure if you do a google on safety factors in engineering design you should get a few hits.


If you can go to your local university library, you can pick up a steel design book that had both ASD and LRFD design. In the beginning, there should be discussion on how safety factors are arrived that may help or give better history than this attempt.





-----Original Message-----
From: John McQuaid [mailto:John.McQuaid(--nospam--at)]
Sent: Friday, November 04, 2005 7:34 AM
To: seaint(--nospam--at)
Subject: journalist query - factors of safety


Greetings. I’m trying to learn about factors of safety in general terms. In levees/floodwalls, documents show the standard FOS to be 1.3. We’ve had some engineers saying this was too low, at least for New Orleans, given the extreme risks involved with a breach during a hurricane. But I am trying to set this issue in context. What are typical safety factors for other kinds of structures – dams, highway overpasses, hospital buildings, etc. Are they prescribed by code or statute in some cases, or by some other means? How are extreme risks, loss of life, property, etc. taken into account? I won’t publish comments generated on this list. Just seeking input/perspective at this point.



John McQuaid

The Times Picayune, New Orleans

Washington bureau

1101 Connecticut Ave. NW s. 300

Washington, DC 20036