There were a series of issues with the Hyatt Regency walkways, and at this point I'd expect every structural engineer knows the story.
1) The engineer designed something that was not easily buildable. (The bridge had to be jacked 2 stories up along threaded rods that supported it, and nuts rotated up that distance)
2) The contractor modified the design in the shop drawings to make it more buildable, (split the threaded rod into two sections, with the lower half hanging from the upper walkway) but in doing so doubled the stress on a particular piece that itself was replaced by a less capable similar item. (box section vs welded C sections)
3) The Engineering firm signed off on the change to the shop drawings without realizing the significance of the changes.
Even before they made that sloppy change that halved its strength, their design only supported 60% of the minimum rated load required by the building code. It was bad engineering from start to finish, and the engineers involved lost their licenses as a result.
1) The engineer designed something that was not easily buildable. (The bridge had to be jacked 2 stories up along threaded rods that supported it, and nuts rotated up that distance)
2) The contractor modified the design in the shop drawings to make it more buildable, (split the threaded rod into two sections, with the lower half hanging from the upper walkway) but in doing so doubled the stress on a particular piece that itself was replaced by a less capable similar item. (box section vs welded C sections)
3) The Engineering firm signed off on the change to the shop drawings without realizing the significance of the changes.