How to calculate moment, shear and floor with equivelent cooper E loadings for a GE C40-8 locomotive. I need to build a table for bridge spans up to 100 feet.
The specs for C40s are well documented online.
I cannot find my AREMA books with the practical formulae, its been years since I’ve even thought about this stuff.
Randy
Perhaps Private Mail to Overmod. I will ask our Physics /Math guy tomorrow see what he says. He is a P. Eng
Would be like trying to teach surgery on-line - needs a least 1, possibly 2 semesters of 3-credit courses in Statics and Simple Structures.
Moreover, those loads depend on the length of each span- i.e., is a 80’ span a single span or 2 of 40’? - and if a truss, the configuration/geometry of each of the triangles of that truss. That kind of information is necessary to calculate the “influence line” for those loads in each member. Without that info, there are so many combinations that it’s not practical to do so. Even with it, there will be a different E-rating for each member - all will have to be checked, because the lowest rating will control. Note too that these loads are just the ‘external’ ones for each memeber, and don’t take into account the ‘internal’ loads and stresses which depend on the shape and materials of each member as well.
Nevertheless, here are a few links froma quick Google search that may be useful. Note the scheme of the Cooper’s loading, and that a rough approximation may be obtained by comparing the axle loads and spacings of the E-10 loading with the axle loads and spacings of the C40-8. Also note how the frame and truck centers of the C40 act as kind of a superimposed bridge across several of the Cooper’s axles.
https://www.trainorders.com/discussion/read.php?1,706188
https://en.wikipedia.org/wiki/Theodore_Cooper#Coopers_Loading_System
http://www.dot.ca.gov/des/techpubs/manuals/bridge-memo-to-designer/page/section-17/17-130.pdf
Don’t look to those that built the pedestrian bridge at FIU for advice.
Suspicion is that it is material supplier/buyer that will have 'splainin to do. Forensic engineering on this one will be interesting to see if design vs. construction vs. materials can be separated in the final analysis. (Something went terribly wrong in the post tensioning process)
Wise counsel from PDN. Something still missing.
I have not looked at the ‘accelerated’ construction methodology carefully, but I immediately thought of the lesson taught by the flying-buttress failure at Beauvais Cathedral. This bridge was, I understand, intended to be cable-stayed. But before even starting to erect the pylon, let alone string and tension the cables that will suspend the beam of the deck with gravitational stabilization … they start cranking up the longitudinal tension in that long, slender deck, not stopping when cracking and then spalling is observed? With traffic passing below?
Eerie similarity with that answering-machine business to Theodore Cooper’s letter about the Quebec Bridge signs of failure in 1907, perhaps a similar case of improperly-diagnosed massive overstrain out of expected planes.
Interesting dashcam video of the collapse showing what appears to be a buckling about 30-40 feet south of the north support of the span, which wouldn’t have been my guess originally. The forensics on this one will be interesting.
I downloaded the NBS report on the 1981 walkway collapse in Kansas City and the investigative findings, beyond the obvious engineering errors (designing something that was unreasonably difficult to implement then approving a design change without realizing that the load on critical elements was doubled by the change) into more subtle errors of design and construction.
This all goes back to a wonderful quote by a high-rise structural engineer who opined that the difference between conservative engineering and rabid paranoia was barely detectable. That’s not limited to structural engineering, by the way.
I’ve run across several oopsie’s in my career as an EE which I attributed as being due to “insufficient paranoia”, i.e. not taking some time into thinkng what could go wrong. This is even more important when an oopsie could lead to serious injury or loss of life (which can happen with electronic equipment).
I’d also am interested in seeing a forensics report on the FIU bridge collapse.
I’d also second MC’s comment about Paul’s post. I know enough about structural engineering to know that I don’t have a clue about to properly due a Cooper’s E-loading rating.
I think maybe all of us who have some serious work in EE or other fields have seen that. I always loved the phrase “mission critical” as defining the level of concern required. I worked with a software engineer who epitomized my paranoia statement, in that any time he made even a one-line correction would spend some time agonizing over how the change could bite us. When he came up empty, he would release the change for testing. We were rarely bitten by anything he did.
I know enough about structures from statics and solids to appreciate the complexity of the problems involved and I guess I’m glad that I went the EE path with its own complexity problems. An appreciation of Professor Rube Goldberg is nonetheless a good thing to have.
In this case the accelerated bridge construction means the concrete bridges was built on a nearby site. When finished it was transported like a pre-cast concrete element into its final position. Video: http://abcnews.go.com/US/explaining-accelerated-bridge-construction-technique-collapsed-miami-bridge/story?id=53777995
Yes, the bridge looks like a cable stayed bridge: http://www.mcm-us.com/sites/default/files/styles/project/public/slider/east_view.jpg?itok=h0vYI120
But I found a US Today online report that states that the bridge was a truss bridge. They pylon and the stays were just for show: https://www.usatoday.com/story/news/2018/03/16/miami-bridge-collapse-suspension-cables-support-tower/431418002/
Here are two quotes from the linked report: Cheryl Stopnick, an outside spokeswoman for FIGG Bridge Engineers, which designed the bridge, said the structure was “truss bridge with above-deck truss elements.”
Robert Accetta, the National Transportation Safety Board investigator in charge, said diagonal elements between the bridge’s canopy and deck worked like a truss bridge. But the cables designed to fan out from the column weren’t needed to support the bridge deck, he said. “As I understand it, these were cosmetic,” A
Now that is really stunning. Have any other bridges been built with large elements appearing to be standard functional structural components, but actually being just for syle and appearance?
Plenty of stuff out there with zero members and dead load. (usually at an architect’s insistance for aesthetics or weather protection purposes)…no big deal normally.
At the risk of flingin’ a polecat in the middle of the family choir practice; and someone who was almost victimized/mashed, by another engineering mistake , some years back. Paranoia, in the practice of engineering, can be a good thing at times. [ My close call was almost caused by six floors of ‘double-tee’s’ {precast/prestressed concrete beams} that were caused to fall,when a supporting point, sheared off, and caused the cascade of the entire six floors of parking garage,stair -well to collapse, above the point where we were eating lunch. [|(] ] Which, I guess is why, Engineering, like Medecine, is only ‘practiced’ by those IN the professions; done well by some, not so much by others.[:-^]
I am just surprised that a truss bridge would be built to look like a suspension bridge complete with a tower that looks to be 50-70 feet tall and array of suspension cables fanning out from the tower and connecting to the bridge trusses; -----when the tower and cables are not actully performing any support function, but are just there to make the bridge appear to be a suspension bridge.
Overall, there is just something about this bridge project that makes it seem like so much more than just a bridge.
I wouldn’t go so far. But respect for the task ahead and self-reflection are desirable.
With experience you learn were you have to do a double take. Some construction elements have internal reserves others like brackets don’t.
Regards, Volker
For us viewers of this thread that have almost no idea of bridge construction we have some questions. Forensics has much to follow thru . Suspect that this short list is only a sampling of problems that may have occured ?
Design – Not enough steel as one possible item
Materials not up to specification
continous pour or separate ?
Concrete used stale
placing finished bridge on transporter
placing on columns
Any pretensioning
What caused crack and location top or bottom maybe indicating compression or tension crack
Did failure of bridge start at crack
Did post tensioning close crack and cause failure
.
I have a question on a bridge with a flat floor (concrete), a vertical center truss above the floor and little arch to the floor. How does the tension to the floor address (handle) the vertical forces on the structure? At first look, the bending moments on that long span are asking for fracture. I would love to see the calculations. The stays had to be there to transfer the vertical loads from the span to the pylon. Also, how was the center truss connected to the floor? That could be a stress point leading to cracking.
I have a question on a bridge with a flat floor (concrete), a vertical center truss above the floor and little arch to the floor. How does the tension to the floor address (handle) the vertical forces on the structure? At first look, the bending moments on that long span are asking for fracture. I would love to see the calculations. The stays had to be there to transfer the vertical loads from the span to the pylon. Also, how was the center truss connected to the floor? That could be a stress point leading to cracking. I hope they have test cylinders of the concrete to prove it had the speciied strength.
2018…two thousand and eighteen.
Advanced computers and technology.
The Romans could have built this thing and it would still be there.
The truss consists of the bottom deck, the diagonal struts, and the top deck. The vertical load tends to sag the truss between its two end supports. The sagging force puts the lower deck into horizontal tension which is resisted by the tension cables embedded in the concrete of the lower deck.
