Florida International University FIU post tensioned concrete pedestrian bridge collapse forensics

Submitted by Jeff Buster on Fri, 03/16/2018 - 11:30.
Florida International University  FIU post tensioned concrete pedestrian bridge collapse forensics

The dollys which moved the post tensioned concrete bridge were not located at the very ends of the bridge - consequently the dolly's put uplift into the bridge in locations where uplift was not intended. Did this crack the structure?

The end of the bridge which was to be next to the cable stayed tower is where the break took place - to the left in the above image.   

The outboard end of the bridge stayed up on the support pylon. The bridge shear bracing is not symmetrical. Since this structure was intended when completed to be a cable stayed bridge - how is it that the post tensioned concrete section was ever intended to be self supporting?

This is an analysis in progress.

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Pride goeth before destruction, and haughty spirit before fall

 Today's news reports that engineers had noticed active cracking of the concrete at the north end ofthe structure two days before the bridge collapsed.   They held a meeting and announced that the cracking "had to be addressed" but that the cracking was not a safety issue.  

Actually, the cracking of the post tensioned concrete is a spectacularly beneficial attribute of post tensioned concrete - failure was not immediate - the cracking failure announced itself visually and provided about four days warning time.   But nobody took the warning seriously because of "pride" - no one wanted to admit that there was a problem. 

 

 

https://news.fiu.edu/wp-content/uploads/IMG_4387-400x300.jpg

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Construction marvel to connect FIU to Sweetwater

On March 10, the main span of the FIU-Sweetwater UniversityCity Bridge was lifted from its temporary supports, rotated 90 degrees across an eight-lane thoroughfare, and lowered into its permanent position.

“FIU is about building bridges and student safety. This project accomplishes our mission beautifully,” said FIU President Mark B. Rosenberg. “We are filled with pride and satisfaction at seeing this engineering feat come to life and connect our campus to the surrounding community where thousands of our students live.”

From https://news.fiu.edu/2018/03/first-of-its-kind-pedestrian-bridge-swings-into-place/120385