The bridge was designed by amateurs. Nobody designs all reinforced concrete truss bridges, especially those with a long span to shallow depth ratio. Concrete cannot carry the shear forces through the diagonal joints. Concrete cannot transfer the top chord forces either across a cold joint at brace top or into a brace cap, and deliver that load into a concrete diagonal. Bridges like this can only be designed by using steel wide flange struts that are welded together at all of the joints. and have massive embedments into the concrete roof and floor slabs, in order to transfer huge forces. The initial failure occurred at the roof slab to upper brace intersection at the first intersection in from the north end. The post tensioning in the diagonals was for crack control only and not strong enough to handle the tension loads in the highly stressed diagonal tension members at each end of the bridge. The two most likely failure mechanisms were a shear failure through the cold joint on top of the end diagonal compression brace, or a vertical shear failure in the middle of the joint between the two end diagonal braces. Whomever designed this bridge never checked shear stresses through the joints.
I am a in the UK. I can see the bridge failed when the cable they were tightening snapped. You can see the typical hydraulic tensioner sticking out on the end of the cable over 2 meters long on the north end. When that cable went slack with a noise that happened a few hours earlier making the crack appear in the bridge the road should have been closed. When a hydraulic tensioner fails it had hundreds of foot pounds of torque on it and shoots out like a bullet. In the UK no cars are allowed to travel under a bridge that is under construction. As an additional point the top section was part of the structure not just a decorative section it was the section that made the bridge stable it would have been attached to the tops of the bridge and connected to the bottom section via the cables they were tightening at the time of the failure. I feel for the victims of this tragedy.
I get that they have said that but I dont believe that this is true. This is partially due to the fact that a tensioned I beam constructed bridge like that over that length this bridge is needs more then 2 high tension wires one in each side of the centre of the I beam. The other reason that the "top" decorative section would need to also be hurricane proof. for that to be hurricane proof it would have to be tensioned otherwise it would just fall over in hurricane weather. Would you trust hollow metal tubes attached to an upright concrete without it being part of the structure. That is like building a house with a flat roof then putting some roof tiles in a peak on top but not making them part of the structure and expecting them to hold up to 200 mile per hour winds, or making a car with windows and a roof thats not actually part of the car. so its just resting on top with a couple of bolts. Also the original plans show it as structural wires. He also says "as I understand it the top is just cosmetic" and "as we understand it" The at this time" and the as we understand it" They dont even admit a crack in the bridge, he says "We dont, I dont think we know factually that there was a crack in the bridge " but he falls over on his words by saying "I know the crews were out there inspecting it" and "I dont know if thats related to the cracks they discovered" so they do know that they discovered cracks. The bridge was installed and technically if it was just one half of the walkway that was missing they could have allowed people to go across as soon as it was installed. with a temporary bridge on the other side then once the top "Cosmetic section" could have been built and placed in place after. The last thing is that the cables are all left at the top ready to attach to the wires coming from the "cosmetic top" strange that the design and the original plans show the structure as a Suspension bridge design when they could have just made a simple bridge it was for safety after all not for making the a height statement. they could have just made it Interesting without a big sail on top not actually part of the strength.. Concrete works well under compression pressure, it does not work well when being stretched. it breaks easily when stretched. thus making it strong requires additional support through wires across the bottom section compressing the bridge base and compressing the trusses otherwise they would break within seconds of being built... Dont believe if you have people saying two opposite contradictory facts. you cant have two facts saying two opposite things. you can have no cracks and cracks. you cant make something hurricane proof then add a 100 foot metal and concrete decoration to the top and not make it structural.
I wonder who did the ORM on the day when the bridge collapsed? As in who thought it was a good idea to be doing adjustments to the bridge without closing the roadway?
The questions are painful ! ... nobody asked anything about the investigation process. Instead they mostly asked questions nobody could possibly answer at the start of an investigation... basically all asking: "tell me what failed, so I can publish it?"
He (guy in ntsb hat)states he's not a bridge engineer or a bridge expert but He's the one in charge of the investigation. Wouldn't you want a bridge EXPERT in charge of the investigation to make sure it's investigated accurately? The other guy couldn't even remember what the question asked was 30 seconds after it was asked. One reporter asked "what is the normal procedure or type of tests they do to make sure the bridge is safe to have traffic under?" He answered as if she had asked what they did. She was asking for bridges like this what would be the tests they should perform and were those done and passed in order for traffic to pass under.
Who in the name of safety approved this bridge type engineered design? Why would they not have used preformed, prestressed concrete? Looks like a poorly engineered and designed structure! It has too many assembly flaws! Where the alleged (non suspension of the structured walkway) cables tie into the pretension cables of the angled structure spanned crossbraces, the angle of which these are pulling is perpendicular to the crossbraces and there tension devices! It may be sumwhat copeasthetic if both sides where using the same span cable. Given during assembly this was not occurring from your video indication. There is so many issues, its almost as if the Whitestar Titanic is being built again! It was doomed before it was being laid out and drafted! Then it being the first of this design that you were aware of? Does anyone ever test these situations out, and follow protocol applying safety guidelines during assembly and building phases while they were being evolved and composed? Boy, what a sad, sad, situation as well as a tragic travesty!!! Best of luck fellas! I will bet they over tensioned a cable to aggressively as well as not doing all pretension and suspension devices that applied to the phase sections. Were laser deflection measuring devices used to monitor changes in structural integrity? How warm was it when the forms were poured and how warm was it at the time the neglegent incident occurred? How much time had transpired in the curing process? Was the pours tested for proper component measurements as well as proper strength? I could go on and on. Yet, this whole project looks like a trainwreck! A man would have been foolish to have taken a ride! Be safe!
G'day, Maybe yes..., and maybe no...; And maybe Baby, we dun' 'no...! But before you bust y'r Foofoo-Valve with all that there huffin' & puffin' about y'r suspiscions regardin' the Contractors bein' so foolish as to have recklessly overtensioned yonder Tension-Bolt...; ye may want to spare a moment to ponder what was the actual Metalurgy of the Steel in the Bolt and what did the Architect specify...? Y'see, a point which has occurred to me is that for the past 5 years at least there have been a steady flow of stories being reported concerning several Asian Nations (particularly China) having introduced some extremely sub-standard Steel Sheet, Bar, and preformed Beams...; one case involved a pre-painted 20-ft I-Beam in which the Web had only been Tack-Welded into place, with a dab of welding every 3 ft along it's Length, and the gaps covered-over with Silastic... Apparently it's an example of what they call "Chinese Silicon-Welding" (!). As the story comes off a Radio Doccumentary covering difficulties faced by the Steelmaking Industry broadcast by Australia's ABC Radio National Network, I assume it's a genuine report of an actual incident...; that being the case, what are the odds that the Steel in the Tension-Rod may have been made of Reject-Quality, or made of the Right Stuff but wrongly tempered..., but supplied as being The Real Thing...? If something like that had occurred, then the Crew may have experienced a catastrophic Failure at well below the amount of Tension which the Plans told them to wind it up to...(?). Just(ifiably ?) sayin', Take it easy... ;-p Ciao !
You are asking a huge amount of questions and it seems that all of them will be answered in the NTSB report that will be released at the end of the investigation. Yes it seems that there were some issues that came up for which measures were taken to try and rectify them. However saying that this bridge was doomed to fail or something of the sort seems very naive since we do not have an in depth report yet. If anything, it was not poorly engineered but it seems the mechanisms used to move the structure into place were modified from the original design and that required multiple changes. One of which was applying further post tensioning of internal cables. A cable was over tensioned and snapped causing catastrophic failure. You are at risk of sounding delusional due to your incoherent ranting.
WarblesOnALot always let others take the first bite of your food. Do not let yourself down. It is never the other guys fault. Yes weve sold our souls to the cheapest bidder for our greed of the highest price! Gday!
WarblesOnALot: Good point on Steel quality .. there are many possible defects & failure modes .. and with many catastrophic fails, more than one defect or error is usually involved in a perfect storm of horror. It's not clear to me whether the crew was tightening or loosening tension in the Post Tension Rod, when the bridge collapsed. the plans called for over tensioning those the PT Rods in the end most beams for the transportation process, to compensate for lifting the structure at points inboard from the intended pylon support locations at each extreme end..... then the plans called for Loosening those PT Rods once the bridge was on the pylons, to reduce the tension to the intended post tension spec level. This whole failure could be something stupid, like the crew tightening that PT Rod when they were supposed to be loosening it.
In my opinion, NTSB Chairman Robert Sumwalt is the best public servent that we have.
Keith Pedersen his press conference skills are very impressive
I so have to agree with this
The bridge was designed by amateurs. Nobody designs all reinforced concrete truss bridges, especially those with a long span to shallow depth ratio. Concrete cannot carry the shear forces through the diagonal joints. Concrete cannot transfer the top chord forces either across a cold joint at brace top or into a brace cap, and deliver that load into a concrete diagonal. Bridges like this can only be designed by using steel wide flange struts that are welded together at all of the joints. and have massive embedments into the concrete roof and floor slabs, in order to transfer huge forces. The initial failure occurred at the roof slab to upper brace intersection at the first intersection in from the north end. The post tensioning in the diagonals was for crack control only and not strong enough to handle the tension loads in the highly stressed diagonal tension members at each end of the bridge. The two most likely failure mechanisms were a shear failure through the cold joint on top of the end diagonal compression brace, or a vertical shear failure in the middle of the joint between the two end diagonal braces. Whomever designed this bridge never checked shear stresses through the joints.
and you are 100% correct...they just released the design flaws...the re bar reinforcing was only 4 sq inches....the load capacity needed 18...
I am a in the UK. I can see the bridge failed when the cable they were tightening snapped. You can see the typical hydraulic tensioner sticking out on the end of the cable over 2 meters long on the north end. When that cable went slack with a noise that happened a few hours earlier making the crack appear in the bridge the road should have been closed. When a hydraulic tensioner fails it had hundreds of foot pounds of torque on it and shoots out like a bullet. In the UK no cars are allowed to travel under a bridge that is under construction. As an additional point the top section was part of the structure not just a decorative section it was the section that made the bridge stable it would have been attached to the tops of the bridge and connected to the bottom section via the cables they were tightening at the time of the failure.
I feel for the victims of this tragedy.
I get that they have said that but I dont believe that this is true. This is partially due to the fact that a tensioned I beam constructed bridge like that over that length this bridge is needs more then 2 high tension wires one in each side of the centre of the I beam. The other reason that the "top" decorative section would need to also be hurricane proof. for that to be hurricane proof it would have to be tensioned otherwise it would just fall over in hurricane weather. Would you trust hollow metal tubes attached to an upright concrete without it being part of the structure.
That is like building a house with a flat roof then putting some roof tiles in a peak on top but not making them part of the structure and expecting them to hold up to 200 mile per hour winds, or making a car with windows and a roof thats not actually part of the car. so its just resting on top with a couple of bolts. Also the original plans show it as structural wires.
He also says "as I understand it the top is just cosmetic" and "as we understand it" The at this time" and the as we understand it"
They dont even admit a crack in the bridge, he says "We dont, I dont think we know factually that there was a crack in the bridge " but he falls over on his words by saying "I know the crews were out there inspecting it" and "I dont know if thats related to the cracks they discovered" so they do know that they discovered cracks.
The bridge was installed and technically if it was just one half of the walkway that was missing they could have allowed people to go across as soon as it was installed. with a temporary bridge on the other side then once the top "Cosmetic section" could have been built and placed in place after.
The last thing is that the cables are all left at the top ready to attach to the wires coming from the "cosmetic top" strange that the design and the original plans show the structure as a Suspension bridge design when they could have just made a simple bridge it was for safety after all not for making the a height statement. they could have just made it Interesting without a big sail on top not actually part of the strength..
Concrete works well under compression pressure, it does not work well when being stretched. it breaks easily when stretched. thus making it strong requires additional support through wires across the bottom section compressing the bridge base and compressing the trusses otherwise they would break within seconds of being built... Dont believe if you have people saying two opposite contradictory facts. you cant have two facts saying two opposite things. you can have no cracks and cracks. you cant make something hurricane proof then add a 100 foot metal and concrete decoration to the top and not make it structural.
I wonder who did the ORM on the day when the bridge collapsed? As in who thought it was a good idea to be doing adjustments to the bridge without closing the roadway?
It's blamed on a rush to not disrupt traffic :/
The questions are painful ! ... nobody asked anything about the investigation process. Instead they mostly asked questions nobody could possibly answer at the start of an investigation... basically all asking: "tell me what failed, so I can publish it?"
They keep asking the same questions over and over
He (guy in ntsb hat)states he's not a bridge engineer or a bridge expert but He's the one in charge of the investigation. Wouldn't you want a bridge EXPERT in charge of the investigation to make sure it's investigated accurately? The other guy couldn't even remember what the question asked was 30 seconds after it was asked. One reporter asked "what is the normal procedure or type of tests they do to make sure the bridge is safe to have traffic under?" He answered as if she had asked what they did. She was asking for bridges like this what would be the tests they should perform and were those done and passed in order for traffic to pass under.
Who in the name of safety approved this bridge type engineered design? Why would they not have used preformed, prestressed concrete? Looks like a poorly engineered and designed structure! It has too many assembly flaws! Where the alleged (non suspension of the structured walkway) cables tie into the pretension cables of the angled structure spanned crossbraces, the angle of which these are pulling is perpendicular to the crossbraces and there tension devices! It may be sumwhat copeasthetic if both sides where using the same span cable. Given during assembly this was not occurring from your video indication. There is so many issues, its almost as if the Whitestar Titanic is being built again! It was doomed before it was being laid out and drafted! Then it being the first of this design that you were aware of? Does anyone ever test these situations out, and follow protocol applying safety guidelines during assembly and building phases while they were being evolved and composed? Boy, what a sad, sad, situation as well as a tragic travesty!!! Best of luck fellas! I will bet they over tensioned a cable to aggressively as well as not doing all pretension and suspension devices that applied to the phase sections. Were laser deflection measuring devices used to monitor changes in structural integrity? How warm was it when the forms were poured and how warm was it at the time the neglegent incident occurred? How much time had transpired in the curing process? Was the pours tested for proper component measurements as well as proper strength? I could go on and on. Yet, this whole project looks like a trainwreck! A man would have been foolish to have taken a ride! Be safe!
G'day,
Maybe yes..., and maybe no...;
And maybe Baby, we dun' 'no...!
But before you bust y'r Foofoo-Valve with all that there huffin' & puffin' about y'r suspiscions regardin' the Contractors bein' so foolish as to have recklessly overtensioned yonder Tension-Bolt...; ye may want to spare a moment to ponder what was the actual Metalurgy of the Steel in the Bolt and what did the Architect specify...?
Y'see, a point which has occurred to me is that for the past 5 years at least there have been a steady flow of stories being reported concerning several Asian Nations (particularly China) having introduced some extremely sub-standard Steel Sheet, Bar, and preformed Beams...; one case involved a pre-painted 20-ft I-Beam in which the Web had only been Tack-Welded into place, with a dab of welding every 3 ft along it's Length, and the gaps covered-over with Silastic...
Apparently it's an example of what they call "Chinese Silicon-Welding" (!).
As the story comes off a Radio Doccumentary covering difficulties faced by the Steelmaking Industry broadcast by Australia's ABC Radio National Network, I assume it's a genuine report of an actual incident...; that being the case, what are the odds that the Steel in the Tension-Rod may have been made of Reject-Quality, or made of the Right Stuff but wrongly tempered..., but supplied as being The Real Thing...?
If something like that had occurred, then the Crew may have experienced a catastrophic Failure at well below the amount of Tension which the Plans told them to wind it up to...(?).
Just(ifiably ?) sayin',
Take it easy...
;-p
Ciao !
You are asking a huge amount of questions and it seems that all of them will be answered in the NTSB report that will be released at the end of the investigation. Yes it seems that there were some issues that came up for which measures were taken to try and rectify them. However saying that this bridge was doomed to fail or something of the sort seems very naive since we do not have an in depth report yet.
If anything, it was not poorly engineered but it seems the mechanisms used to move the structure into place were modified from the original design and that required multiple changes. One of which was applying further post tensioning of internal cables. A cable was over tensioned and snapped causing catastrophic failure.
You are at risk of sounding delusional due to your incoherent ranting.
WarblesOnALot always let others take the first bite of your food. Do not let yourself down. It is never the other guys fault. Yes weve sold our souls to the cheapest bidder for our greed of the highest price! Gday!
WarblesOnALot the silastic welding comment is spot on. Ave much? He did a couple of great vidjayos about this tragedy.
WarblesOnALot: Good point on Steel quality .. there are many possible defects & failure modes .. and with many catastrophic fails, more than one defect or error is usually involved in a perfect storm of horror.
It's not clear to me whether the crew was tightening or loosening tension in the Post Tension Rod, when the bridge collapsed. the plans called for over tensioning those the PT Rods in the end most beams for the transportation process, to compensate for lifting the structure at points inboard from the intended pylon support locations at each extreme end..... then the plans called for Loosening those PT Rods once the bridge was on the pylons, to reduce the tension to the intended post tension spec level. This whole failure could be something stupid, like the crew tightening that PT Rod when they were supposed to be loosening it.