[Cryptography] Crypto Standards v.s. Engineering habits - Was: NIST about to weaken SHA3?

[Alan Braggins]

On 02/10/13 18:42, Arnold Reinhold wrote:
> On 1 Oct 2013 23:48 Jerry Leichter wrote:
>
>> The larger the construction project, the tighter the limits on this stuff.  I used to work with a former structural engineer, and he repeated some of the "bad example" stories they are taught.  A famous case a number of years back involved a hotel in, I believe, Kansas City.  The hotel had a large, open atrium, with two levels of concrete "skyways" for walking above.  The "skyways" were hung from the roof.  As the structural engineer specified their attachment, a long threaded steel rod ran from the roof, through one skyway - with the skyway held on by a nut - and then down to the second skyway, also held on by a nut.  The builder, realizing that he would have to thread the nut for the upper skyway up many feet of rod, made a "minor" change:  He instead used two threaded rods, one from roof to upper skyway, one from upper skyway to lower skyway.  It's all the same, right?  Well, no:  In the original design, the upper nut holds the weight of just the upper skyway.  In the mo
>   di
>> fied version, it holds the weight of *both* skyways.  The upper fastening failed, the structure collapsed, and as I recall several people on the skyways at the time were killed.  So ... not even a factor of two safety margin there.  (The take-away from the story as delivered to future structural engineers was *not* that there wasn't a large enough safety margin - the calculations were accurate and well within the margins used in building such structures.  The issue was that no one checked that the structure was actually built as designed.)
>
> This would be the 1981 Kansas City Hyatt Regency walkway collapse (http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse)

Which says of the original design: "Investigators determined eventually 
that this design supported only 60 percent of the minimum load required 
by Kansas City building codes.[19]", though the reference seems to be a 
dead link. (And as built it supported 30% or the required minimum.)

So even if it had been built as designed, the safety margin would not
have been "well within the margins used in building such structures".