Miami pedestrian bridge collapse

[Industrial Toys]

 

[Streetcar]

There are different kinds of engineering firms. swines and I seem to have worked for large full service engineering firms. We hire only the best people and charge accordingly. New engineers quickly make 6 figures but we expect them to work whatever it takes to make the job successful. A lot of engineering is done by small firms with 5 or 10 engineers. They have some very good people but there is only so much capability in a small firm.

At least in the US, many local and federal government projects can only be awarded to small firms that are minority or women owned. That's fine but they are often smaller and less capable than large firms.

I don't know anything about the firms involved with the Florida bridge but while I was working full time we made a lot of money salvaging projects awarded to low priced small firms.

The Miami bridge was designed by the firm that originated much of the post tension concrete bridge work in us.
They have completed many signature bridges

 

[Industrial Toys]

My Dad worked for a company (Harris Group) that bought VSL who was (IS) a world leader and Pioneer in Post Tensioning. Got me several visits up the being constructed CN Tower. Not an easy task at age 13!

I'm still using an old spool of many thousand feet of plastic tubing used for the tensioning strand.

 

[California]

With pros like that involved then somebody's warning 'this is never going to work' got ignored, somewhere in the process. Like the Challenger o-rings.

My opinion is carrying the bridge into place without supporting at the end was the critical error, things got stressed that were never considered in designing it.

Have there been any subsequent statements from the principals, or critics, that improve our understanding?

 

[Streetcar]

Vsl was contractor on many of the figg designed bridges.

 

[kevin37b]

The problem was they backed it in supported by the ends . This unloaded the tension . 2 trucks instead of 4 . Before they recovered tension , snap .

 

[aczlan]

The problem was they backed it in supported by the ends . This unloaded the tension . 2 trucks instead of 4 . Before they recovered tension , snap .

Incorrect. The original plan was to drive it into place supported by the ends. That was changed partway through to move one of the platforms from the end to 1/4 of the way in from the end and remove the spreader plates.
It is suspected that they had to change the tension to accommodate this and they were re-adjusting the tension to where it needed to be as a bridge when it failed

Aaron Z

 

[kevin37b]

I guess I got the wrong info ? Thanks , Kevin .

 

[aczlan]

Eng-Tips has a whole lot of discussion, speculation, hypotheses by engineering professionals, that is more insightful than what we have in this thread.
Also much better photos.
Eng-Tips . com - Forums by Industry > Forensic Engineering > Engineering Failures & Disasters Forum
Miami Pedestrian Bridge, Part II - Engineering Failures & Disasters - Eng-Tips

I guess I got the wrong info ? Thanks , Kevin .

From California's link in post 86:

Just in case anyone is interested in a rough idea of the tension / compression loading of the trusses when:
A-In transit supported underneath in 2 places mid span
B-In Situ supported at either end of the span

These are not to scale or necessarily accurate, but give a general idea. Draw your own conclusions here.
A:

B:

Aaron Z

 

[Industrial Toys]

Is it not possible to tension such a structure that the whole thing is ridged, like a steel truss, and can carry at least it's own weight, regardless of support, or would this be considered wasteful for the end requirement?