My vague recollection from my first year engineering course, that I dropped before failing, almost 20 years ago (caveat train! Choo choo!) is a failure critical

My vague recollection from my first year engineering course, that I dropped before failing, almost 20 years ago (caveat train! Choo choo!) is a failure critical component is a component that if failing would trigger a complete structure failure. There are parts of bridges where any failure would be expected to cause complete collapse, like the cracked beam on the Hernando de Soto bridge (happily that span turned out to not actually be critical). But as the Hernando de Soto bridge showed you can have a complete failure of a major structural element without a collapse (in this case we’re lucky that accidentally happened). So if the report says that none of the instant fail section were responsible I’m going to trust that.