Community Chat

[ROMARY]

My very first thought was: Was it or the steel 'Made in C' (?).

I recall one of the bridges over in SF:  A small section had to be replaced.  Took several (5 or possibly more) years.  Made you know where.

Not very successful, from what I heard.  Something about the steel screws or whatever rusting out, steel allegedly 'snapping', etc.  All allegedly.  It's been a long time re: facts, etc.

In the meanwhile, during that time, a 26 mile over-the-water bridge was made 'over there' in C. in only a couple of years or so.  Very impressive.  Take a look.  

[missy1]

It needed suspension wires,  and a middle support column.

[nomless]

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@missy1wrote:

It needed suspension wires,  and a middle support column.

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There were cables (somewhere in the structure) that has loosened. They were tightening the cables when the collapse occurred. A middle support was to be installed soon. Sadly, not soon enoigh.

[missy1]

I am talking about these cables/wires. This is what it was supposed to look like.

@nomless

[missy1]

The reason for the bridge being built, because a 18 year old FIU student is now deceased,  due to a car hitting her on the busy 8th street in August 2017.

sad

[ROMARY]

It's easy to see that those cables (in the photo) would have kept the bridge roadway stable and upright.  Not a chance that it could collapse with those (if properly installed) cables holding the bridge roadway up. 

[ROMARY]

RIP.   Hopefully there weren't more injured/deceased underneath the rubble.

Who would have thought that this could/would happen in this day and age of permits, inspections, etc., etc.

In General: Would be nice to have someone/some (independent or gov) agency 'oversee' the manufacturing of bolts, steel, etc.  If the building industry itself can't seem to do it, well, then, looks as though some sort of intervention is needed.  (Said from someone who normally isn't crazy about gov interference to begin with. But when something tragic like this happens, I tend to change my mind.) 

An independent agency would be my first choice. 

[sidsmom]

This reporter from the Miami Herald has an excellent Twitter feed

updates for the bridge collapse.  She posted a video of the 2 cars

being extracted today...completely flattened.

Also on Twitter, there was a dash cam video of the bridge

actually falling.  Stunning video.  And to see a school bus sitting

yards away, narrowly missing the collapse, just makes it chilling. 

Also...contracted firm to build this bridge is getting more unflattering

news. They have lots & lots of governmental contracts & 

rub elbows with many politicos. This could develop into a

story bigger than the actual collapse. Just sayin’.

[gardenman]

Modern concrete projects often use tensioned cables or rods to provide additional strength. There are pretensioned systems where the cables/rods are tensioned before the concrete is poured and the concrete sets locking everything in place. There are also post-tensioned systems where hollow tubes are cast in the concrete and then after the concrete sets, the cables/rods are threaded through and then tensioned. 

This bridge was a post-tensioned design. The design called for it to be tensioned for the move, then have that tension reduced after the move. It looks like they were adjusting the tension when the bridge failed. In one of the photos you can see the hydraulic tensioner still attached to one of the rods that appears to have broken. When a tensioned rod breaks, it sends shock waves through the concrete that likely led to the collapse. We'll know more over time, but the general view of the online engineering community is that it was a tensioning failure.

Those failures shouldn't happen, but the only way to truly know how strong something is, is to stress it until it breaks. Once it breaks you know how strong it was. You can estimate the strength of a cable/rod based on how strong you know similar cables/rods were, but you don't absolutely know the strength of that specific cable/rod. An undetected flaw in the cable/rod, or damage to it at some point, can drastically change the strength. It looks like one of the remaining rods failed causing this collapse.

[MorningLover]

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@missy1wrote:

The reason for the bridge being built, because a 18 year old FIU student is now deceased,  due to a car hitting her on the busy 8th street in August 2017.

sad

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An 18 year old FIU student dies in bridge collapse. 

The bridge that was intended to give FIU

students a safe way to cross the busy street.

Alexa was driving past FIU with her friend, who was in

the passenger seat, when the bridge collapsed. The

passenger was able to get out of the car, but was

unable to get Alexa out.  

The victims of the FIU pedestrian bridge collapse..

 http://www.miamiherald.com/news/local/community/miami-dade/article205680019.html