Miami Pedestrian Bridge, Part VI 31

[jrs87]

Time to go back to traffic camera video. Only 2 or 3 frames are useful. Clearest version:

https://www.youtube.com/watch?time_continue=7&v=YmqluABSn94

No obvious sign to me of 11/10 failure starting collapse, but this time I notice interesting ripple motion of banner on 11. It appears member 11 is shortening and bursting behind the banner early in the collapse. Or perhaps it's just being blasted by air? I still theorize a shear force found an unexpected path and destroyed 11 at the base precipitating collapse.

 

[3DDave]

I've come to suspect that #11 was released at the bottom, allowing rotation of the main span segments, which put a side load on #11 at the base, breaking it at the top, because of the semi-parallelogram action of the canopy and deck.

 

[dbill74]

With all the talk of tensionnig of cables and fancy graphics of stresses in the members and what not, there is one aspect of this bridge I have yet to see anyone address.

This was supposed to be a cable stayed bridge.

http://www.mcm-us.com/projects/road-bridges/road-and-bridges-fiu-pedestrian-bridge

Now, I'm not a structural engineer, but it seems to me that this span wasn't designed to be supported at just 2 points. Lacking the supporting cables along the length for a long period of time was simply unreasonable. It is also clear in the video of the collapse, there is no temporary support in the middle of the span.

A fan of engineering documentary TV shows, I've seen numerous examples of bridge construction projects. In every example, the supporting towers of suspended and cable stayed bridges are ALWAYS the first things to go up. This bridge's supporting tower had not been erected yet. Seems the cause of the collapse is more in the erection process than the actual "finalized" design or lack of tensioning and such.

Just saying. If this span wasn't designed to be self supporting, it never should have been left up as it was without additional support.

 

[LionelHutz]

This was supposed to be a cable stayed bridge.

No, it wasn't. Did you really think you were the first one to point that out after approximately 1000 posts have been make on the subject of the bridge collapse?

 

[JAE]

Please discontinue posting in this thread. Go to Part VII 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.

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




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