Wow, it's a sad fact that inferior materials are used by some contractors for personal gain, I thought those times would have been long gone!
No implying it's the cause of the one today.
I don't know if that is the case either.
Most likely it was just ignorance.
The problem could be in the design itself.
People are the ones that draw up those designs.
Consider that even if the design was faulty, the bridge could not be built over a public domain without approval.
Was it ignorance or complacency during the approval?
Was it a material fatigue?
A contruction mistake?
An application overload?
It could be that the material was sufficient but installed in the wrong alignment for its maximum strength.
Like a 2x4 laying flat where it should have been verticle.
A truss that was too short to support the load.
I'm sure there will be an investigation.
Who know what the cause will be determined to be?
Maybe it wasn't the bridge at all.
Wind took out the Tacoma Narrows bridge.
There were design defects that would not have mattered except they forgot to account for the winds.
Perhaps it was the vibration from the traffic?