# Instant bridge--just add disaster. **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [March 15, 2018, 7:11pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618 "2018-03-15T19:11:17Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [March 16, 2018, 4:37pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/41 "2018-03-16T16:37:45Z")
Did some more googling and I think this is one weird-ass bridge design. I had thought that the second “layer” was a roof to shelter pedestrians from weather (well, rain–snow is probably not high risk) but from concept [renderings](https://media.nbcmiami.com/images/1206*675/082217+fiu+bridge+sw+8th+street+rendering.JPG) and [models](https://news.fiu.edu/wp-content/uploads/bridge-model.jpg) I see that it covers only a fraction of the bridge and is there to anchor the suspension cables. Then I think of the [Liberty Bridge](https://en.wikipedia.org/wiki/Liberty_Bridge_at_Falls_Park_on_the_Reedy) in (nearby for me) Greenville, SC. Also a suspension pedestrian bridge with a single row of cables, but cost $4.5 million and has been in use for years. I don’t know how much it weighs, but the two “masts” [are 28 tons each](http://www.fallspark.com/175/The-Liberty-Bridge), and I really doubt that the rest of it adds up to an extra 900ish tons. And it actually [looks pretty cool](https://www.google.com/search?q=liberty+bridge+greenville&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjE7tCjo_HZAhUM7oMKHXYkBgcQ_AUICigB&biw=1056&bih=509). ---
**Author:** ![mikecurtis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mikecurtis/32/3284_2.png) [@mikecurtis](https://boards.straightdope.com/u/mikecurtis)\ **Post date:** [March 16, 2018, 4:39pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/42 "2018-03-16T16:39:42Z")
and now everybody’s looking at their bridges [Engineers behind collapsed Fla. bridge involved in East Chicago project](http://abc7chicago.com/engineers-behind-collapsed-fla-bridge-involved-in-east-chicago-project/3223988/) > [@](#): > > The same bridge engineers involved with the pedestrian bridge that collapsed in Miami, killing six, are also involved in engineering a bridge in Northwest Indiana. > > Figg Bridge Engineers have been involved in the construction of the new Cline Avenue Bridge in East Chicago, parts of which have already been constructed. The $140 million project will replace the old Cline Avenue Bridge, which was closed and condemned in 2009. > . . . > > Figg Bridge Engineers has been under fire legally in the past. IN one incident, the Virginia Department of Labor and Industry confirmed that Figg was fined for an incident in 2012. A bridge they designed collapsed onto a railway, injuring some workers. Figg was fined $28,000, but it was later reduced to $9,800. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [March 16, 2018, 4:41pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/43 "2018-03-16T16:41:08Z")
> [@jz78817](#): > > _"Construction on the South Norfolk Jordan Bridge was put on hold after a truss used to build the bridge shifted,_ > > doesn’t immediately identify the failure as a design flaw; could have been an error in assembling that segment or during construction. [This article](http://www.miaminewtimes.com/news/fiu-bridge-collapse-construction-firms-accused-of-unsafe-practices-10176596) says that for the South Norfolk Jordan Bridge accident, > [@](#): > > Figg was fined $28,000 by the Virginia Department of Labor and Industry, which found the company had violated several safety rules. It had failed to gain written consent from a manufacturer before modifying a girder used in construction. The company was also cited for not doing daily, weekly, and monthly inspections of the girder; not providing adequate training for using the equipment; and not having certain safety procedures in place for its maintenance and repair, according to the Virginian-Pilot. The article also talks about a makeshift walkway (for use during construction?) they built in Fort Lauderdale-Hollywood International Airport that collapsed and inured a TSA employee. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [March 16, 2018, 5:48pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/44 "2018-03-16T17:48:36Z")
Video of the bridge collapsing: > **[Surveillance video shows moment FIU pedestrian bridge collapsed](https://www.miamiherald.com/news/local/community/miami-dade/article205443304.html)** > > Update: New video posted to social media Friday shows the clearest view yet of collapse. , ---
**Author:** ![mcgato](https://avatars.discourse-cdn.com/v4/letter/m/ac8455/32.png) [@mcgato](https://boards.straightdope.com/u/mcgato)\ **Post date:** [March 16, 2018, 6:20pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/45 "2018-03-16T18:20:28Z")
> [@Machine\_Elf](#): > > That depends on who screwed up. If he had a solid design and assembly plan, but it wasn’t followed, then he’s off the hook. Something like that happened in Colorado in 2004, when [a bridge girder buckled and collapsed during construction](https://www.denverpost.com/2006/03/20/a-series-of-deadly-errors/), decapitating the occupants of a car on the highway below it. The design was fine, but the construction crew screwed up the installation. I used to be a programmer for an engineering company. An engineer told about a project that he worked on, a parking garage, that failed shortly after completion. He said everyone involved with the project was sued, including him as professional engineer. That was designer, engineer, suppliers, manufacturers, workers on site, etc. Then they worked through what happened in order to figure out which of the participants was to blame. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [March 16, 2018, 7:16pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/46 "2018-03-16T19:16:11Z")
> [@Mangetout](#): > > Seems to me as though they took the temporary supporting structures away before they added the permanent supporting stuff. [Removing temporary supports too soon brought down a partially constructed apartment building near here 45 years ago.](https://en.wikipedia.org/wiki/Skyline_Towers_collapse) ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [March 16, 2018, 7:58pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/47 "2018-03-16T19:58:31Z")
> [@enipla](#): > > Reminds me of this - [Hyatt Regency walkway collapse](https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse). 115 dead. Seems a sort of seat of the pants last minute design change was the cause. We looked at it in a class I took. What happened was the threaded support rods for the two walkways were originally designed as a single long rod. This made for construction problems as the nuts supporting the top beam had to be turned all the way up the threaded rod. The construction people proposed cutting the support rods in two, so instead of a long rod with one nut supporting the top walkway and a second lower nut supporting the bottom one they’d have two offset rods, with one supporting the top walkway and one supporting the bottom. They were well within the load factors for the rods, but failed to consider that this modification meant the nuts and beams supporting the top walkway were now also supporting the bottom one. The engineers took a real beating on that one, and deserved it. Gross negligence, misconduct and unprofessional conduct in the practice of engineering, loss of licenses; the whole works. See, that’s why engineers are so freaking cautious. If you try a last minute design change and it fails, it’s deaths and injuries and destruction of property in the millions; loss of licenses and civil and criminal charges, but if the last minute design change works, you get a certificate of appreciation in a handsome plastic frame. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [March 16, 2018, 9:24pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/48 "2018-03-16T21:24:39Z")
> [@Darren\_Garrison](#): > > [Here](https://facilities.fiu.edu/projects/BT_904/FIU-Pedestrian-Bridge-Design-Criteria-2015-05-06_REV.pdf) is an 80 page PDF on the proposal for the bridge. This appears to be a solicitation for proposals - it’s titled “Design Criteria” and lists requirements for the bridge. It doesn’t show any specific design. It contains 18 pages of pictures showing “Design Concept Precedents.” I guess these are what they were hoping to get - they’re all prettier than the one they ended up with. Also, almost half of this 80-page document seems to be talking about an elevator. 😕 ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [March 16, 2018, 9:38pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/49 "2018-03-16T21:38:41Z")
There is an interesting comment on [this](https://www.nytimes.com/2018/03/16/us/miami-bridge-collapse.html) NYT article: > [@Some guy called "mekonahe sangnarnahi" in an NYT article](#): > > It seems to me that the structure as constructed was okay to support it’s own weight. The cables would be needed at a later stage when the rest of the bridge was constructed, prior to opening the bridge for pedestrian loads. The very fact that the structure was fine for five days indicates that there were no issues with the structure itself. Any issues in the strength of the structure would have been conspicuous. Typically in concrete structures strength issues manifest as excessive sagging and/or cracks in the concrete. I haven’t seen any reports detailing such issues. I have seen the footage of the actual collapse. The suddenness with which the structure collapsed leads me to believe that there was a sudden loss in capacity, also referred to as a brittle failure. Loss of steel reinforcement leads to brittle failure in concrete structures. Reports seem to indicate that the structure was post-tensioned (PT). PT provides tremendous tensile capacity to concrete. However, loss of PT can lead to a sudden catastrophic reduction in strength as concrete by itself has virtually no resistance to tensile stresses. Based on Sen. Rubio’s tweet, I think they were working on adjusting the PT on this bridge when the failure initiated. There are several photos that show a strand jack attached to a PT bar on the collapsed bridge (I believe failure initiated here). It’s quite possible that the PT bar was overstressed or there was a failure of the PT anchor leading to a sudden, brittle failure. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [March 16, 2018, 10:38pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/50 "2018-03-16T22:38:06Z")
PT slabs can be scary for construction workers. I was warned many times to never cut or drill into a PT house slab. You can get badly hurt. The slab is usually stamped with a clear warning (in the garage) or they’ll be a sign posted on the wall. PT slabs are used on land with poor structural support. Like a low lying area with fill dirt. The load is spread across a wider area in a PT slab. I can easily see a bridge failing if one of those rods snapped. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 16, 2018, 11:21pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/51 "2018-03-16T23:21:46Z")
> [@Darren\_Garrison](#): > > There is an interesting comment on [this](https://www.nytimes.com/2018/03/16/us/miami-bridge-collapse.html) NYT article: > > > [@Some Guy](#): > > > > It seems to me that the structure as constructed was okay to support it’s own weight. The cables would be needed at a later stage when the rest of the bridge was constructed, prior to opening the bridge for pedestrian loads IANACivil Engineer, but this bit seems unlikely to me. Pedestrians aren’t _that_ heavy - how could there be a structure where the design tolerances are such that it’s strong enough to stand alone, but requires an enormous superstructure of supporting cables when a few hundred pounds of people are added as a load. Doesn’t make sense. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [March 16, 2018, 11:59pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/52 "2018-03-16T23:59:49Z")
Fifteen people can easily be a ton. The bridge goes between the school and a residential area. It is pretty easy to imagine two or three tons of humanity crossing it at some times. And each one of those people is pounding the deck repeatly with their weight. It takes a little more than a few hundred pounds capacity for a pedestrian bridge. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [March 17, 2018, 12:32am UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/53 "2018-03-17T00:32:20Z")
> [@eschereal](#): > > Fifteen people can easily be a ton. The bridge goes between the school and a residential area. It is pretty easy to imagine two or three tons of humanity crossing it at some times. And each one of those people is pounding the deck repeatly with their weight. It takes a little more than a few hundred pounds capacity for a pedestrian bridge. According to the PDF I linked earlier, they were hoping for a bridge that would be Party Central: [QUOTE=That PDF I linked earlier] This structure should function as more than just a path for circulation; it should be a place to be and a place to be experienced, and the FIU campus and its students must be proud of it. It should be a destination in its own right where community members might linger, gather, and create an urban social space – a linear park. We expect that the bridge might even be used as an event venue. For those reasons, it should be equipped with furniture, shading, protection from the elements, and state of the art safety features such as LED lighting, video surveillance and emergency call boxes. [/QUOTE] ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [March 17, 2018, 1:09am UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/54 "2018-03-17T01:09:05Z")
> [@Darren\_Garrison](#): > > I had thought that the second “layer” was a roof to shelter pedestrians from weather (well, rain–snow is probably not high risk) but from concept [renderings](https://media.nbcmiami.com/images/1206*675/082217+fiu+bridge+sw+8th+street+rendering.JPG) and [models](https://news.fiu.edu/wp-content/uploads/bridge-model.jpg) I see that it covers only a fraction of the bridge and is there to anchor the suspension cables. When I look at that model, it looks to me like the cables are going through conduits to ultimately anchor to the main deck. So, yeah, I think they were intended to provide support to the whole structure. When I look at satellite view, I see that the street it was crossing is nine lanes wide (3W, 2LT, 4E) – they easily could have blocked half of that to place temporary support structures under the span until it had at least half of the suspension cables in place. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [March 17, 2018, 1:56am UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/55 "2018-03-17T01:56:15Z")
I feel very bad for the university. They had a serious problem with students from Sweetwater crossing that dangerous road. The problem won’t go away and now they have to start completely over. That’s assuming the school is even willing to restart the process. With all the lawsuits, students may be risking their lives crossing that road for many years to come. The easiest and quickest solution would be a pedestrian crossing light. That could get students across that road at predetermined times during the day. That won’t be popular with local drivers. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [March 17, 2018, 4:27pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/56 "2018-03-17T16:27:11Z")
Now [reports that the bridge was cracking](https://www.wsj.com/articles/bridge-engineers-gave-briefing-on-crack-hours-before-collapse-university-says-1521295470) for days before the fall. ---
**Author:** ![voltaire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voltaire/32/313_2.png) [@voltaire](https://boards.straightdope.com/u/voltaire)\ **Post date:** [March 17, 2018, 5:00pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/57 "2018-03-17T17:00:21Z")
I’m no structural engineer, but that special self-cleaning concrete with titanium dioxide (which was mixed on site, not premixed elsewhere and delivered in cement mixer trucks, as per usual) would be my guess as to the culprit. Though, another thing I’m wondering about is that temperatures in South Florida have been particularly cooler than usual and I wonder if that might have factored in somehow. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [March 17, 2018, 5:06pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/58 "2018-03-17T17:06:07Z")
[QUOTE=Some Guy] The cables would be needed at a later stage when the rest of the bridge was constructed, prior to opening the bridge for pedestrian loads. [/QUOTE] > [@Mangetout](#): > > IANACivil Engineer, but this bit seems unlikely to me. Pedestrians aren’t _that_ heavy… > [@eschereal](#): > > …It is pretty easy to imagine two or three tons of humanity crossing it at some times… In Florida, the bridge would need to withstand hurricane force winds. Wouldn’t that be a much more significant engineering consideration than pedestrian loads? My thought is that maybe the construction protocol allows it to be assembled outside hurricane season without the supporting cables, with the cables to be installed before the bridge is exposed to high winds. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [March 17, 2018, 6:14pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/59 "2018-03-17T18:14:10Z")
It gets worse. Long technical presentation that the bridge is sound. Then 3 hours later… How wrong can engineers possibly be? > **[Miami bridge: Meeting over crack held hours before collapse](https://www.bbc.com/news/world-us-canada-43440501.amp)** > > An engineer told officials there were no safety concerns about the bridge hours before it collapsed. > [@](#): > > Florida International University said a meeting on Thursday morning involved the engineering and construction companies, as well as Florida’s transport department. > > An engineer told officials it “did not compromise the structural integrity”. > > The bridge fell on eight vehicles about three hours later. > > In a statement, the university said the “engineer of record” from the contractor FIGG gave a technical presentation regarding the crack, in a meeting that lasted about two hours. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [March 17, 2018, 6:33pm UTC](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618/60 "2018-03-17T18:33:49Z")
Bear in mind that we don’t yet know for sure that the crack was connected to the failure. [Previous page](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618.md?page=2) [Next page](https://boards.straightdope.com/t/instant-bridge-just-add-disaster/810618.md?page=4)