old_jim, I think, the bottom deck may have dragged #11 and #12 back in. The PT tendon that is securely attached to the bottom deck had a snag with the bottom most ties and reinforcement of #11, and crumbled(#11 base).
jrs87, those are shims, not teflon as shown on the proposal drawing below, unless there was a change on the final drawing.
The slide side is on the south side, the south side View C-C were mistakenly posted numerous times in part IV.
Post Edit Addition, likely the anchors had been tightened...
No information on the crack, however, gwideman, has posted in Part IV the possible location which is likely the shear critical location.
Either de-tensioning or tensioning of PT would be detrimental to this.
Meerkat007, your comparison between bridge collapse movie and theoretical simulation of truss without member #11 looks similar. It tells that the diagonal #11 crumbles at the base first, otherwise, it would have pushed out #12 a great distance based on the geometry as shown below, before the...
Meerkat007, the simulation clearly showed the movement of the roller support, akin to the tore out. I am newly registered here, and found this discussion really interesting, with lots of great responses. Thanks a lot.
gwideman's summary above, I believe, likely captures what happened. As the diagonal member 11 pushes in compression, the bottom slab has to tore away from 11 and 12 first in order for a significant deflection to occur. Since a large portion of the bottom deck is still resting on the pylon, it...