Genghis:
I was a Civil Engineering student at the time of the walkway collapse at the Hyatt Regency Hotel in Kansas City, MO. There are many places on the web that you can find information about it. Here's one:
http://www.uoguelph.ca/~ajenney/webpage.htm
That collapse was quickly used as a case study in our classes. The web site shown above has sketches of the joint in question, with the original design and the as-built. There were two walkways, one above the other. The original design had both walkways supported by one 30' long (IIRC) rod. Quite rightly, the contractor did not like this design, because it would require threading the support beam for the upper walkway (and its nut) 20' feet up the rod. It was essentially unbuildable.
The as-built redesign had two rods: 1) one rod from the ceiling to the beam supporting the upper walkway, and 2) one rod from the beam supporting the upper walkway to the beam supporting the lower walkway. The box beams in the as-built design were basically unchanged from the original design.
Any structural engineer type (whether civil or mechanical) worth his or her salt will immediately recognize that the as-built places approximately double the load on the box beams supporting the upper walkway. In the original design, the upper beams support only the weight of the upper walkway itself (plus anyone standing on it) -- the load of the lower walkway is supported by tension in the rod. In the as built, the lower walkway is supported by the lower rods. The lower rods are supported by the upper box beams. Thus, in the as-built, the upper beams are now supporting both the upper walkway and the lower walkway.
And then there's the details of the joint itself...
Yes, a number of engineers lost their licenses. There was plenty of blame to go around, however. The original design wasn't great. The redesign was done by the structural fabricators, who should have caught the problem. The designers should have caught the problem when reviewing the redesign. The constructors should have recognized the problem with the redesign as well.
My point ("yes, get to the point!" I hear you say...) is that this was an incredibly obvious error, immediately obvious to most junior year undegraduates.
OFBSLF
(who is no longer a civil engineer and now drives keyboards for a living)