Stories
Slash Boxes
Comments

SoylentNews is people

SoylentNews is powered by your submissions, so send in your scoop. Only 18 submissions in the queue.
posted by CoolHand on Monday March 19 2018, @07:15PM   Printer-friendly

An "instant" pedestrian bridge at Florida International University in Miami collapsed on March 15, killing a number of motorists. A 174-foot, 950-ton span of the bridge was installed on Saturday, March 10 over a busy portion of Tamiami Trail called Southwest Eighth Street. The incomplete bridge suddenly collapsed on Thursday:

The bridge gave way suddenly while the traffic light for motorists on Tamiami Trail was red, so that the concrete span fell on top of a row of stopped vehicles. A woman stopped at the light who was heading westbound said the structure fell without warning. The woman, who asked that her name not be used, said it was immediately clear to her that several people were dead.

[...] The bridge crashed across six lanes of heavily traveled Tamiami Trail, crushing a still undetermined number of cars and killing a still unclear number of people. Police on the scene said at least six people could be dead.

From an earlier article:

The rapid span installation was the result of months of preparation. The bridge's main 174-foot span was assembled by the side of the Trail while support towers were built at either end. The 950-ton span was then picked up, moved and lowered into place by special gantry cranes at the intersection of Southwest 109th Avenue in an operation that lasted several hours Saturday morning.

[...] The innovative installation method significantly reduced risks to workers, pedestrians and motorists and minimized traffic disruptions, FIU said. The architecturally distinctive, cable-supported bridge is the product of a collaboration between MCM Construction and FIGG Bridge Design, the firm responsible for the iconic Sunshine Skyway Bridge over Tampa Bay.

[more...]

The news stories about the Miami Bridge follow the common pattern of containing almost no technical information and a massive focus on the horror. The comments section to the news articles are almost equally horrific. So I started looking for civil engineering forums, ran across this one: http://www.eng-tips.com/viewthread.cfm?qid=436595 and in one of the links in one of the comments, ran into a link to the proposal from MCM and FIGG: https://facilities.fiu.edu/projects/BT_904/MCM_FIGG_Proposal_for_FIU_Pedestrian_Bridge_9-30-2015.pdf It runs 173 pages and is a mixture of marketing and an explanation of the phases of construction. Very nice renderings

I have none of the requisite knowledge to comment on the collapse, but the reading is finally interesting. I'd be interested in other people's finds as well.

https://www.nytimes.com/2018/03/17/us/florida-bridge-collapse-crack.html

Hours before the collapse of a pedestrian bridge at Florida International University on Thursday, the engineering company for the bridge met with the construction manager and representatives from the university and the Florida Department of Transportation to discuss a crack on the structure, according to a statement from the university released early Saturday.

The engineering company, Figg Bridge Engineers, delivered a technical presentation on the crack, the statement said, and "concluded there were no safety concerns and the crack did not compromise the structural integrity of the bridge."

Six vehicles remain trapped under the bridge, with four of them very difficult to extract, Maurice Kemp, deputy mayor of Miami-Dade County, said.


Original Submission #1Original Submission #2Original Submission #3

 
This discussion has been archived. No new comments can be posted.
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
  • (Score: 2) by Runaway1956 on Tuesday March 20 2018, @02:30AM (2 children)

    by Runaway1956 (2926) Subscriber Badge on Tuesday March 20 2018, @02:30AM (#655231) Journal

    The whole concept of frefabricating and prestressing concrete is about saving money. That's it in a nutshell. Concrete is expensive. Engineers and contractors want to save all the concrete possible, because an extra yard of concrete eats into their profit.

    Anyone who has worked in industrial construction has seen these things damaged during installation. As noted several times, concrete is brittle. When you start moving a concrete structure around, you can expect some impacts, and some bending, flexing, or warping.

    I just never learned to trust prefab concrete. It's much better to pour in place, and to not worry excessively about some extra yards of concrete.

    Watching the sales pitch video, it's obvious that there are suspension cables supporting a portion of the bridge's weight. There are no suspension cables in sight, at any stage during construction. Just how many field modifications were made? When a standard suspension bridge is built, it is obvious to all that the suspension cables are integral to the bridge's design. In this case, the sales video shows suspension cables, but we don't even see attachment points for any such cables. We see no tower or platform from which to hang any suspension cables. Who authorized the changes, and when?

    Nothing about this bridge, or it's construction inspires confidence. Seriously - nothing.

    We can all be happy that we weren't involved at any stage in this project.

    Starting Score:    1  point
    Karma-Bonus Modifier   +1  

    Total Score:   2  
  • (Score: 0) by Anonymous Coward on Tuesday March 20 2018, @05:29PM

    by Anonymous Coward on Tuesday March 20 2018, @05:29PM (#655508)

    In this case, the sales video shows suspension cables, but we don't even see attachment points for any such cables. We see no tower or platform from which to hang any suspension cables. Who authorized the changes, and when?

    The "cables" you mention were not structural members of this bridge. It was a truss bridge, not a suspension or cable-stayed bridge. Apparently they would have served to dampen vibrations but were not essential to support the design load of this bridge.

    Obviously a serious fuckup happened somewhere but I am sure the plan was entirely reasonable to bridge experts. The final investigation results should be interesting.

  • (Score: 0) by Anonymous Coward on Tuesday March 20 2018, @06:37PM

    by Anonymous Coward on Tuesday March 20 2018, @06:37PM (#655547)

    "There are no suspension cables in sight, at any stage during construction. Just how many field modifications were made? "

    This sounds like projects i've been on. Incompetent morons trying to get people killed.