The biggest one being that it was a suspension bridge without any suspension.
That could certainly be a factor.
It SHOULD have held itself up until finished.
Hence the linked example from 1981.
“New self washing concrete”? Lack of adequate cure time for above? Hurried construction? Voids in concrete from lack of consolidation? Lack of compressive strength from segregation in concrete poured in a hurry with high slump? Design change during construction? Erection of structure prior to adequate cure of concrete? Lack of inspection for the interim condition?
Over-reinforced design of a concrete structure, weak concrete, or loads in excess of the compressive strength of the concrete as designed? .... You might be onto something.
Under reinforced design dictates that steel will fail slowly, instead of concrete collapsing. Over reinforced design results in catastrophic failure of concrete prior to steel giving an inch. Hence why a #8 bar in a concrete structure isn’t necessarily better than a #6. Under reinforced means steel will stretch WELL before concrete is in jeopardy.
“Minorities, homos, females, dykes, immigrants, liberal plants, affirmative action”, etc., or whatever anyone here hates, from the responses above, would be squarely off my list of causes.
The responses blamimg those causes are no more responsible than those blaming ARs for innocent civilian deaths.
The saddest thing is even square set timbering from a century and a half ago, set in the middle until they got things truly assembled would have prevented the collapse... unless of course it was just too far gone from the true cause of the failure...
It would have delayed traffic. Which probably wasn’t acceptable.
In the photos of the scene there is a lane in the middle that may not be for traffic???
Mark Begich, Joaquin Jackson, and Heller resistance... Three huge reasons to worry about the NRA.
Federally funded project, Pennsylvania design firm, local contractors... and tried and true construction procedures. to say that accidents will happen sounds harsh, should have been around (or remember what it was like) a few short decades ago, before all the regulations and safety procedures.
Something went fatyiltaly wrong, but as to the process of modular construction that has been proven time and time again to be the safest all around practice on smaller projects such as this, as to the steel used in a reinforced concrete structure... more than 90% of rebar used in the U.S. is made in the U.S.
Accident could have been caused by anything or a combination of things, a bad on-site desision with unseen consequences, flaw'd testing, on-site design change, a flaw in material or construction process at any given point which just wasn't caught... it's damn sure going to take time to find out and probably plenty of blame to pass around, doesn't help to second guess!
If you do any contract work for any government agency in Florida (and most other states) you can't even submit a bid unless you are a minority owned company.
Spec this spec that, engineers making pretty sets of plans and patting themselves on the back
Still....it's some high school dropout "Ernie" his dad got him a job at the concrete plant. He might be the one mixing the concrete and pushing the buttons. In between spits of copenhagen of course.
Federally funded project, Pennsylvania design firm, local contractors... and tried and true construction procedures. to say that accidents will happen sounds harsh, should have been around (or remember what it was like) a few short decades ago, before all the regulations and safety procedures.
Something went fatyiltaly wrong, but as to the process of modular construction that has been proven time and time again to be the safest all around practice on smaller projects such as this, as to the steel used in a reinforced concrete structure... more than 90% of rebar used in the U.S. is made in the U.S.
Accident could have been caused by anything or a combination of things, a bad on-site desision with unseen consequences, flaw'd testing, on-site design change, a flaw in material or construction process at any given point which just wasn't caught... it's damn sure going to take time to find out and probably plenty of blame to pass around, doesn't help to second guess!
Phil
I see what you are trying to get at but all of those things listed are negligence, not accidents. I have been running this through my mind since it happened to try and rationalize how in this day and age something like this is still possible, yes, we're all human but the checks and balances in a construction project of this magnitude should be plenty adequate.
I'd assume the bottom chord of the general truss shape has continuous steel through it, possibly post-tensioned. I'm not civil/struc, but I've seen sleeved coarse-stranded cable cast into an upper-story building slab before, and then grabbed from one end, stretched a couple feet, and then secured with a gripper collet. I'd assume that's a pretty typical way of tensioning concrete reinforcement. The guys I watched doing the stretching had stories to tell about cables letting go during tensioning...cable as a projectile! The post tensioning process is monitored by an inspector, measuring strain and applied load.
Point being, footage of the instant it let go seemed to show the bottom chord of the bridge's truss shape letting go...that chord should more or less be in pure tension, with easily calculated loads and correspondingly easily specified reinforcement. But, I assume there to be some reinforcement design nuance for managing loads in intersecting concrete truss members...
Over on The Hull Truth (THT) site (a boating and fishing site, lots of Florida news and members) there is a long thread detailing the collapse, photos, and likely cause. The failure reason (Or reasons, this accident is a cascade of things done wrong) is already known. Worth a read.
When you get to THT scroll down to "Dockside Chat" and look for the bridge thread.
Survivor of the 13th Original Colony, I escaped on December 17, 1968.
Never heard of a non negligent accident before, there's always some degree of negligence in one or more areas that cause every accident... limiting such causes results in safety.
The buzz on the thread at thehulltruth.com indicates major issues with post-tensioned reinforcement in the bottom chord of the truss/girder that is the bridge. It is not clear to me if the center column and suspension cables are structural components or window dressing. It is clear to me that folks across the land: politicians, media and joe sixpack are confusing the suspension cables with the concrete reinforcement cables in that bottom chord.
If it had been determined before collapse that a.) there was an issue, any issue, with tension in the bottom chord reinforcement, be it loosening or failure to apply proper tension or overstrain and b.) the roadway wasn't blocked off in response, then someone's going to jail.
Any hype related to this sort of construction being revolutionary or forward thinking is indicative of galactic ignorance on the part of those doing the hyping...there's nothing special about prefabrication of very large stuff.
Originally Posted by Vek
I'd assume the bottom chord of the general truss shape has continuous steel through it, possibly post-tensioned. I'm not civil/struc, but I've seen sleeved coarse-stranded cable cast into an upper-story building slab before, and then grabbed from one end, stretched a couple feet, and then secured with a gripper collet. I'd assume that's a pretty typical way of tensioning concrete reinforcement. The guys I watched doing the stretching had stories to tell about cables letting go during tensioning...cable as a projectile! The post tensioning process is monitored by an inspector, measuring strain and applied load.
Point being, footage of the instant it let go seemed to show the bottom chord of the bridge's truss shape letting go...that chord should more or less be in pure tension, with easily calculated loads and correspondingly easily specified reinforcement. But, I assume there to be some reinforcement design nuance for managing loads in intersecting concrete truss members...
Condolences and prayers to those still alive who lost souls they cared for as a result of the failure.
Whatever the cause.
This.
There is video on the Internet of the actual collapse, but it is from a distance and appears to be digitally zoomed, so the resolution isn't all that great.
There is a traffic cam that is in close proximity to the bridge, but that footage has not been released yet.
Meanwhile the recovery folks try to recover the deceased. Once that has been done, the engineers try to sort out what happened, and then the righteous indignation will be appropriate.
Whining, bitching, and running off at the mouth (or keyboard in this instance) like a bunch of high school girls is par for the course here on the 'Fire these days.
Carry on.
Ed
"Not in an open forum, where truth has less value than opinions, where all opinions are equally welcome regardless of their origins, rationale, inanity, or truth, where opinions are neither of equal value nor decisive." Ken Howell
Never heard of a non negligent accident before, there's always some degree of negligence in one or more areas that cause every accident... limiting such causes results in safety.
Phil
I get it but the tone of the post is that "accidents happen" in this day and age, with the tools, training, and technology available the bottom line is someone screwed up and they should not have. There is a scary trend in the industry involving "innovative" practices for a myriad of reasons but few if any are the right ones.
I'd assume the bottom chord of the general truss shape has continuous steel through it, possibly post-tensioned. I'm not civil/struc, but I've seen sleeved coarse-stranded cable cast into an upper-story building slab before, and then grabbed from one end, stretched a couple feet, and then secured with a gripper collet. I'd assume that's a pretty typical way of tensioning concrete reinforcement. The guys I watched doing the stretching had stories to tell about cables letting go during tensioning...cable as a projectile! The post tensioning process is monitored by an inspector, measuring strain and applied load.
Point being, footage of the instant it let go seemed to show the bottom chord of the bridge's truss shape letting go...that chord should more or less be in pure tension, with easily calculated loads and correspondingly easily specified reinforcement. But, I assume there to be some reinforcement design nuance for managing loads in intersecting concrete truss members...
As a structural engineer, I'd say you're pretty close on what happened. Watching the news video of the collapse, you can see the bridge failed as you described, top chord crushing in compression as bottom cord snapped in tension. This is indicative of a bending failure. The bridge failed near a support, which ironically is a low bending stress location. Usually shear failures are common near/at the supports. Like you mentioned, figuring out the tension loads due to bending in the bottom slab isn't an overly challenging computation. My guess, based on what I've seen so far, and given the location and suddenness of the failure, is that some material failed, could be a post/pre tension cable as you mentioned. Could have been engineered wrong, spec'd wrong, installed wrong, constructed wrong, etc. But I'd guess probably a means and methods or material quality issue. Bottom line is anyone and everyone who had their name on this project is getting a certified letter and will have an insurance claim, even if they weren't at fault. Insurance companies would rather settle than fight, it's just a $ game to them. It's a very sad day in our profession any way you look at it.
A good principle to guide me through life: “This is all I have come to expect, standard lackluster performance. Trust nothing, believe no one and realize it will only get worse…”
