If they fail later, it is because of unknown unknowns . . . which thereby become known unknowns that get incorporated into future engineering text books. Things like resonance [see above] which entrained the Tacoma Narrows Bridge until it bucketed itself to death by "Aeroelastic Flutter" [famous movie - good technical explanation]. Or, because engineers are fallible, they just forget to include something that, with 20/20 hindsight, elicits a big "duh!, I would never have done that" from the community of [smug] engineers who haven't [yet] made a similar mistake. The text-book example of this is the collapse of the skywalk in the lobby of the Hyatt Regency Hotel in 1981. A poorly thought through design modification put 2x pressure on a series of nuts holding up the stack of floors [detail L]. 2x is 100% an increase: well over the generous 50% for emergencies usually factored in. The design mod was driven by a desire to save costs by one of the sub-contractors; several people were found to be culpably negligent and stripped of their engineering epaulets.
At 3.30pm on 10 August 1966, after a day pouring 2,000 tonnes of concrete, the timber framing of one section of the bridge collapsed and flipped the other side of the structure on top of the debris. That debris included several dozen workers who fell 15m to the riverbed only to be slobbed with wet concrete, shafted by rebar , clonked by 4x4s and generally turned into a mess sandwich. Nine men died and 60 were admitted to hospital covered in setting cement, some with rebar sticking out both sides of limbs. Emergency services worked tirelessly into the small hours of the next day pulling people and bodies from the heap. In those days, the widows of the dead were pensioned by the company, but the injured gave thanks for their survival without thinking to lawyer up. Mike Lecuyer had only been on the job two days. George Davis was at the epicentre of the disaster minutes before the event but took himself for a short walk and quite randomly thereby finished up above one of the pillars in comparative safety.
You really don't want to over-think these things. Lecuyer and Davis are duly grateful to be alive but don't imagine that their survival is a message from God. If you believe that you have to accept that the deity had no use for Clarence Beattie, Lucien Regimbald and Joas Viegas who were among the dead. In the grand scheme of things we are all equally without value, except to ourselves and those we love. Trying to work out a reason for it all will just get you in trouble like Brother Juniper in The Bridge of San Luis Rey. He finishes up burned at the stake along with his report on that collapsed bridge because his accumulated evidence questions the omniscience and ultimate benevolence of God. The conclusion that "the wicked [were] visited by destruction and the good called early to Heaven" is not what we would call a testable hypothesis, that's for sure because both balck hats and white hats finish up dead. Maybe Charles Bowen is more realistic:
“The rain it raineth on the just
And also on the unjust fella;
But chiefly on the just, because
The unjust hath the just’s umbrella.”
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