The meister has spoken. Very good.
Thinking back to my structural engineering courses:
1) Although a well-designed truss is very strong, if any single component of the truss is weakened (such as rust) or fatiqued (cracked plate or bolt due to overloading), the truss becomes more prone to failure.
2) And although the load on this bridge was not heavy (thankfully) at the time of its' catastrophic failure, the loads that I-35W have experienced in the past couple of decades are certainly beyond the scope for which it was initially designed.
The latter is true for most older bridges in America though, and through no fault of the engineering. Many advances and comforts of the modern age have contributed to this additionally loading:
1) Rather than having an average 1 car per family as we did in the '60's when this bridge was designed, we now have an average 2.5;
2) Rather than walking to the grocery store, school, church, etc. as we commonly did in the '60's, we now drive almost everywhere, and often; and,
3) Trailer loads have increased with more hp and suspensions.
There are scores of other variables that contribute to additional loading. Sometimes understanding these things helps us cope with the catastrophy...
I didn't realize that you were a p.e. Meister...that changes everything. You're the man!
