Miami Pedestrian Bridge, Part X 50

[JAE]

A continuation of our discussion of this failure. Best to read the other threads first to avoid rehashing things already discussed.

Part I
thread815-436595

Part II
thread815-436699

Part III
thread815-436802

Part IV
thread815-436924

Part V
thread815-437029

Part VI
thread815-438451

Part VII
thread815-438966

Part VIII
thread815-440072

Part IX
thread815-451175



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[Earth314159]

The opening statement of the OSHA Report extended its thanks to a number of entities, including the NTSB. Shearing of the PT Rod may be one of those points that was lost in translation. If a PT Rod did shear, it sheared when the canopy fell and pinned/sliced the PT Rod. The Lower PT bar did, after all, extrude from the blister.

I don't buy that the PT shear during collapse. As the deck fell, the lower PT rod ripped through the bottom of #11 and all the ties in #11. The post collapse curvature suggests the bar would have been mainly in tension. There also wasn't enough concrete left above the bar in the deck to react against the rod to shear it.

The extrusion is far more likely to be from the shorter distance between the #11/#12 joint and #11#10 joint before and after the collapse.

 

[saikee119]

What is the date of the markup in red of the drawing that you attach to your post above? Is that pre-collapse or post-collapse ? How do you know the answer ?

The information you asked took place on Sep 15 2016

NBC did an excellent job to pool all the vital information together called

Interactive: The Path to the FIU Bridge Disaster in

https://www.nbcmiami.com/investigations/Timeline-The-Path-to-the-FIU-Bridge-Disaster-507172431.html

It was a member of this Forum who alerted us to it.

The diagonal crack is a common mode of failure if the truss is push out of the deck. The actual crack is smaller than FDOT's mark-up. Nevertheless FIGG was alerted by an experienced engineer what could go wrong with its design.

FDOT also told FIGG to put PT rod inside Member 11 when it was known during the SPMT haul the span would not be supported the two end points. I totally agreed with FDOT because Member 11 was designed as a compression member in the bridge but during construction it was part of a cantilever so tension reinforcement, over and above the compression reinforcement became necessary.

 

[JAE]

Please discontinue posting in this thread. Go to Part XI thread815-454998 for any further posts.

This topic is broken into multiple threads due to the long length and many images creating longer load times for some. If you are NEW to this discussion, please read the following threads prior to posting to avoid rehashing old discussions.

Part I
thread815-436595

Part II
thread815-436699

Part III
thread815-436802

Part IV
thread815-436924

Part V
thread815-437029

Part VI
thread815-438451

Part VII
thread815-438966

Part VIII
thread815-440072

Part IX
thread815-451175

Part X
thread815-454618

Part XI
thread815-454998


Check out Eng-Tips Forum's Policies here:
faq731-376