I believe the concrete was pre-cast off site. Maybe i'm wrong. The quality control of off site pre-cast is usually very good due to the controlled concrete quality & cure conditions. I'm not saying the concrete quality (in this case) in the deck was totally within specifications, but materials prior to failure will experience a progression thru the materials stress-strain and will exhibit considerable deformation before failure. In other words, you'll see concrete softening (stretching) after it reaches it's ultimate strength then transition into failure.
The bridge won't experience sudden "explosion" failing, like a wooded baseball bat cracking in half.
The main structural strength of the deck was induced thru the post tensioning of the cables.
When I first heard of the collapse I assumed it was a cable stayed structure. As more information was released that evening, I immediately figured it was a post-tension problem wrt the cables thru the concrete slab.
I'll refer to one of the comments in the article:
Paulo Roberto3 days ago
"I am a civil engineer and I would like to express some points. These actual super duper structures are based on calculations of advanced mathematic techniques, These computer programs take in consideration so many variables that it makes almost impossible to control in construction sites. Every element is affecting the next one and so on, the stress and shear forces are dynamically calculated in the computer model . As already mentioned, a structural collapse is a sum of multiple failures, and it's very hard to manipulate those structures in situ.
Once you make a change in one support, you are changing the whole model, affecting the tensions in all elements, the tensions tend to travel to less stressed elements that are not supposed to handle it. If the model is supposed to be supported with on only 2 nodes, when you put another support in the middle, it start to act like a continuous beam.creating all kinds of different tensions in the element. It's an unfortunate case of mishandle the the tensions on the site. Once one or more? rods were subject to tensions above the limit, the steel would break after passing the fluidity limit ( when it loose it's traction capacity ). And I guess that they were already working almost on the limit of their capacity, the security loads for this kind of elements are very high."
