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so interesting. thanks for sharing your expertise in this manner. I understand that they had made plans for building a center support. We are all wondering why that wasn’t at least partially built prior to moving bridge into place and then finished once positioned. prayers for all in this tragedy.
This is not even remotely relevant to the collapse of this bridge. Dr McGee and Mr Gomez both have it wrong. Please take another look at the drawings for this bridge and you will see two important facts. If you fail to acknowledge them now before it is too late, then you may lose your credibility perhaps permanently. I am trying to help you here, but you do what you want. You guys have jumped to a conclusion and are now embarrassing yourselves with your wild over-confidence.
1. The bridge section that fell was only HALF of the final bridge. The center support that you are so sure of yourself about is at the end of this first section across the road from FIU. There is a whole section left to be built over the canal, so yes at the end it will appear to have a center support, but in reality it will be two bridges.
2. The future “cable stays” are not stays at all and are cosmetic pipes mostly for show. The design details show a flat plate welded onto the end of 16″ pipe with a few anchors at the tower and on top of the bridge. Hardly a suitable connection for a cable or even a pipe stay, which would be some kind of heavy duty pinned connection.
We do not know what happened here and it will come out, but I’ll stake my reputation on the fact that this bridge is not “missing” a center support.
“… so yes at the end it will appear to have a center support” quoting you Bryan, as your statement here is the educational purpose of this article.
This article is not about definite rights or wrongs at all. How can it be written with all the facts still to be determined and the investigation still to be completed.
The article is for educational purposes only sir.
Continuous beam (bridge) analysis and design, which I have taught for decades, and which has been outlined in the original 19th century German writings of Mueller-Breslau, of which I own the only existing copies of to-date, and of which I specifically referenced alongside my wonderful students, particularly Mr. Gomez and Ms Reeves, stipulates every statement written inside this educational piece for my students to learn and observe.
I will defend this higher education purpose for future engineers and engineering education to the floor sir.
Sometimes education is presenting fundamental questions to discuss with the public and not just about answering those public questions with definitive right or wrong answers that tends to definitely shut down all further questions and answers and further discussions inside the public forum, and most specifically, inside the higher education classroom.
We have presented this piece for further Socratic discussions inside my spring semester classroom at Texas Tech University in which I am currently teaching Aircraft Structures, and Aircraft Jet Engines and Rocket Propulsion. In that delightful end, the higher purpose of this piece is immediate and is aimed specifically for future minds and capabilities of future civil, mechanical and aerospace engineers – of which I am each of these. I am only serving as a humble teacher here, and as an actively engaged science, technology, engineering and mathematics role model here – and not as a National Transportation Safety Board (NTSB) Member – of which I have not been called upon to serve as humbly speaking.
Thank you for your engagement of this article and my website.
I knew nothing about engineering until I read this article. It is very enlightening and well written. Now I have to question, if this information has been around for so many years, why did the companies involved in building it not follow the rules? Poorly trained engineers or just greedy for the money? Sad that people had to die for whatever the reason.
Andy, that remains to be seen as the investigation continues, who really knows until then. Me and my students were attempting to do an exercise to share with others to join in our conversation, and thank you for joining in. Above all else, this about encouraging and teaching kids to become fine engineers.
Speaking as a structural bridge engineer, this article reads as technical mumbo-jumbo. Lost beneath the factoids and anecdotes is the simple fact that engineers today are entirely capable of designing a bridge able to span the full distance of this bridge without a central support.
Until we know better whether there was an engineering design issue, a construction sequencing issue, or a material failure at FIU, the assertions here are speculative at best (and not particularly coherent at that).
Speaking as a Mechanical Engineer with a Master’s degree on the vibrations of three-dimensional structures, there is no such thing as a bridge without central support. Even suspension bridges, which do not have a physical central support tower, have central supports in the form of suspension cables. Or even arch bridges, which do not have a central support tower, provide central support by redistributing the dead weight loads horizontally. If you look at the FIU article below, you can see that the proposed design incorporated a type of suspension support. Before rotating the bridge 90 degrees onto the highway, they should have installed a temporary central support until the suspension cables were fully installed. Your statement of being a structural engineer is coming into question. I wouldn’t want you designing a doggy house. https://news.fiu.edu/2016/02/fiu-selects-mcmfigg-to-design-and-build-pedestrian-bridge-across-8th-street/97102
I am a retired structural engineer (35 years or work). ianebersole is absolutely 100% correct. Dr. McGee should be commended for showing his students the possible advantage of continuous span construction over simple span construction. But in the case of the FIU bridge the simple “truss” span could easily be designed to accomade the bridge dead load and construction live load until the mast and cable stays were completed. I suspect something went wrong when jacking additional tension in the post tensioned tendons.
I wholeheartedly agree with you Tom and thank you for getting the point of our educational piece for my students. They are wonderfully energetic kids and they deserve our engagement from the experts like you in structural engineering, kind sir. We so appreciate your reading our piece and your online engagement inside our structural engineering classroom. Our five dozen kids now know you herein and are extremely pleased to meet you, Tom! I am pleased to have you join our social media classroom here – as this website is an online media forum for my Aircraft Structures and Aircraft Jet Engines and Rocket Propulsion classes I am teaching this spring semester at Texas Tech University. Our kids look forward to reading more about your experiences, and what you may further want to offer here, as further investigation continues on the FIU Bridge Collapse.
You’re wrong. The bridge did not break in the middle. The video of the actual collapse shows that the bridge first broke at the bottom of the last angled roof support on the right end of the bridge in the last picture. All of the angled roof supports were of similar angle except that the angle of the support where the bridge broke was more vertical than the others.
I was a registered designer of industrial systems(Wisconsin).I agree with Mr McGee’s analysis.
There is no doubt this collapse could have been easily avoided if QUALIFIED engineers had reviewed the methods planned for this installation.
On behalf of our fine young engineers at Texas Tech (who’s basketball athletes have just made the NCAA Sweet 16 in Basketball), Thank you so much, Peter.
My above replies to others gives the purpose(s) of offering this piece to a wanting public wanting to discuss this publicly tragic accident, as they naturally would. We are humbly only one such article among so many others in which similar discussions and learning are taking place. Warmly, Oliver
The original design shows a central support tower with cable stays with the angled web members being in Tension. (You can see the substantial attachment points on the roof.) The section was installed as a “simple span” Without the cable suspension. Wouldn’t that put the top and bottom “flanges” (roof and deck) in excessive and possible opposite stress forces? Seems it would be more difficult/ costly to design a structure both ways?
I also disagree with the narrator in the collapse video who stated the bridge was a “bad design” when it appears the more likely cause to be an Incorrect installation sequence? I’m sure this case will be extensively studied in Civil Engineering classes from now on. So sad at the loss of innocent lives. Details Matter!
We so appreciate your thoughtful comments, your fine questions raised and your suggestive contributions to our discussion here, J.W. Jones! Thank you, Oliver
No plans? Unprofessional. Confused analysis. Incorrect “true deflection” curve. Given that it was designed as a cable stayed bridge and I suspect the stresses were high in the interim and a center support is an easy way out. Without plans I would not draw any conclusions. I love Mueller but he was all about deflection and your curve is discontinuous for a continuous beam. Brian Blum PE, MSME MSCE former aircraft stress analyst.
Not an easy way out Brian, the safest way! Construction and installation and retrofitting America’s Crumbling Infrastructure must always be about safety first at all cost always, sir.
“your curve is discontinuous for a continuous beam”
I beg to differ here Brian, and so does the original 19th Century German works of Mueller-Breslau, which I own inside my library, sir.
Continuous beam (bridge) analysis and design, which I have taught for decades, and which has been outlined in the original 19th century German writings of Mueller-Breslau, of which I own the only existing copies of to-date, and of which I specifically referenced alongside my wonderful students, particularly Mr. Gomez and Ms Reeves, stipulates every statement written inside this educational piece for my students to learn and observe.
I This question is directed to Dr. McGee-
The bridge was to be supported by cables linked to a vertical”post” located at “curb” side . The length of the section supported over the street is approximately 2x the length towards the curb.
Would the support post eventually fail due to greater stresses on the street side?
so interesting. thanks for sharing your expertise in this manner. I understand that they had made plans for building a center support. We are all wondering why that wasn’t at least partially built prior to moving bridge into place and then finished once positioned. prayers for all in this tragedy.
Great question JED, which is why my students and I initiated this public conversation. Thank you for joining in with your fine question.
This is not even remotely relevant to the collapse of this bridge. Dr McGee and Mr Gomez both have it wrong. Please take another look at the drawings for this bridge and you will see two important facts. If you fail to acknowledge them now before it is too late, then you may lose your credibility perhaps permanently. I am trying to help you here, but you do what you want. You guys have jumped to a conclusion and are now embarrassing yourselves with your wild over-confidence.
1. The bridge section that fell was only HALF of the final bridge. The center support that you are so sure of yourself about is at the end of this first section across the road from FIU. There is a whole section left to be built over the canal, so yes at the end it will appear to have a center support, but in reality it will be two bridges.
2. The future “cable stays” are not stays at all and are cosmetic pipes mostly for show. The design details show a flat plate welded onto the end of 16″ pipe with a few anchors at the tower and on top of the bridge. Hardly a suitable connection for a cable or even a pipe stay, which would be some kind of heavy duty pinned connection.
We do not know what happened here and it will come out, but I’ll stake my reputation on the fact that this bridge is not “missing” a center support.
“… so yes at the end it will appear to have a center support” quoting you Bryan, as your statement here is the educational purpose of this article.
This article is not about definite rights or wrongs at all. How can it be written with all the facts still to be determined and the investigation still to be completed.
The article is for educational purposes only sir.
Continuous beam (bridge) analysis and design, which I have taught for decades, and which has been outlined in the original 19th century German writings of Mueller-Breslau, of which I own the only existing copies of to-date, and of which I specifically referenced alongside my wonderful students, particularly Mr. Gomez and Ms Reeves, stipulates every statement written inside this educational piece for my students to learn and observe.
I will defend this higher education purpose for future engineers and engineering education to the floor sir.
Sometimes education is presenting fundamental questions to discuss with the public and not just about answering those public questions with definitive right or wrong answers that tends to definitely shut down all further questions and answers and further discussions inside the public forum, and most specifically, inside the higher education classroom.
We have presented this piece for further Socratic discussions inside my spring semester classroom at Texas Tech University in which I am currently teaching Aircraft Structures, and Aircraft Jet Engines and Rocket Propulsion. In that delightful end, the higher purpose of this piece is immediate and is aimed specifically for future minds and capabilities of future civil, mechanical and aerospace engineers – of which I am each of these. I am only serving as a humble teacher here, and as an actively engaged science, technology, engineering and mathematics role model here – and not as a National Transportation Safety Board (NTSB) Member – of which I have not been called upon to serve as humbly speaking.
Thank you for your engagement of this article and my website.
Warmly,
Oliver
I knew nothing about engineering until I read this article. It is very enlightening and well written. Now I have to question, if this information has been around for so many years, why did the companies involved in building it not follow the rules? Poorly trained engineers or just greedy for the money? Sad that people had to die for whatever the reason.
Andy, that remains to be seen as the investigation continues, who really knows until then. Me and my students were attempting to do an exercise to share with others to join in our conversation, and thank you for joining in. Above all else, this about encouraging and teaching kids to become fine engineers.
Speaking as a structural bridge engineer, this article reads as technical mumbo-jumbo. Lost beneath the factoids and anecdotes is the simple fact that engineers today are entirely capable of designing a bridge able to span the full distance of this bridge without a central support.
Until we know better whether there was an engineering design issue, a construction sequencing issue, or a material failure at FIU, the assertions here are speculative at best (and not particularly coherent at that).
Respectfully, I disagree with you.
Speaking as a Mechanical Engineer with a Master’s degree on the vibrations of three-dimensional structures, there is no such thing as a bridge without central support. Even suspension bridges, which do not have a physical central support tower, have central supports in the form of suspension cables. Or even arch bridges, which do not have a central support tower, provide central support by redistributing the dead weight loads horizontally. If you look at the FIU article below, you can see that the proposed design incorporated a type of suspension support. Before rotating the bridge 90 degrees onto the highway, they should have installed a temporary central support until the suspension cables were fully installed. Your statement of being a structural engineer is coming into question. I wouldn’t want you designing a doggy house.
https://news.fiu.edu/2016/02/fiu-selects-mcmfigg-to-design-and-build-pedestrian-bridge-across-8th-street/97102
Awesome points Virgilio! Keep up your great work young man! Warmly, Doc M
I am a retired structural engineer (35 years or work). ianebersole is absolutely 100% correct. Dr. McGee should be commended for showing his students the possible advantage of continuous span construction over simple span construction. But in the case of the FIU bridge the simple “truss” span could easily be designed to accomade the bridge dead load and construction live load until the mast and cable stays were completed. I suspect something went wrong when jacking additional tension in the post tensioned tendons.
I wholeheartedly agree with you Tom and thank you for getting the point of our educational piece for my students. They are wonderfully energetic kids and they deserve our engagement from the experts like you in structural engineering, kind sir. We so appreciate your reading our piece and your online engagement inside our structural engineering classroom. Our five dozen kids now know you herein and are extremely pleased to meet you, Tom! I am pleased to have you join our social media classroom here – as this website is an online media forum for my Aircraft Structures and Aircraft Jet Engines and Rocket Propulsion classes I am teaching this spring semester at Texas Tech University. Our kids look forward to reading more about your experiences, and what you may further want to offer here, as further investigation continues on the FIU Bridge Collapse.
Warmly,
Oliver
You’re wrong. The bridge did not break in the middle. The video of the actual collapse shows that the bridge first broke at the bottom of the last angled roof support on the right end of the bridge in the last picture. All of the angled roof supports were of similar angle except that the angle of the support where the bridge broke was more vertical than the others.
And you are wrong too.
I was a registered designer of industrial systems(Wisconsin).I agree with Mr McGee’s analysis.
There is no doubt this collapse could have been easily avoided if QUALIFIED engineers had reviewed the methods planned for this installation.
On behalf of our fine young engineers at Texas Tech (who’s basketball athletes have just made the NCAA Sweet 16 in Basketball), Thank you so much, Peter.
My above replies to others gives the purpose(s) of offering this piece to a wanting public wanting to discuss this publicly tragic accident, as they naturally would. We are humbly only one such article among so many others in which similar discussions and learning are taking place. Warmly, Oliver
The original design shows a central support tower with cable stays with the angled web members being in Tension. (You can see the substantial attachment points on the roof.) The section was installed as a “simple span” Without the cable suspension. Wouldn’t that put the top and bottom “flanges” (roof and deck) in excessive and possible opposite stress forces? Seems it would be more difficult/ costly to design a structure both ways?
I also disagree with the narrator in the collapse video who stated the bridge was a “bad design” when it appears the more likely cause to be an Incorrect installation sequence? I’m sure this case will be extensively studied in Civil Engineering classes from now on. So sad at the loss of innocent lives. Details Matter!
We so appreciate your thoughtful comments, your fine questions raised and your suggestive contributions to our discussion here, J.W. Jones! Thank you, Oliver
No plans? Unprofessional. Confused analysis. Incorrect “true deflection” curve. Given that it was designed as a cable stayed bridge and I suspect the stresses were high in the interim and a center support is an easy way out. Without plans I would not draw any conclusions. I love Mueller but he was all about deflection and your curve is discontinuous for a continuous beam. Brian Blum PE, MSME MSCE former aircraft stress analyst.
“a center support is an easy way out”
Not an easy way out Brian, the safest way! Construction and installation and retrofitting America’s Crumbling Infrastructure must always be about safety first at all cost always, sir.
“your curve is discontinuous for a continuous beam”
I beg to differ here Brian, and so does the original 19th Century German works of Mueller-Breslau, which I own inside my library, sir.
Continuous beam (bridge) analysis and design, which I have taught for decades, and which has been outlined in the original 19th century German writings of Mueller-Breslau, of which I own the only existing copies of to-date, and of which I specifically referenced alongside my wonderful students, particularly Mr. Gomez and Ms Reeves, stipulates every statement written inside this educational piece for my students to learn and observe.
I This question is directed to Dr. McGee-
The bridge was to be supported by cables linked to a vertical”post” located at “curb” side . The length of the section supported over the street is approximately 2x the length towards the curb.
Would the support post eventually fail due to greater stresses on the street side?
Great question Peter! Tell us more about what you think?