Please help with this engineering problem!

Birdjaguar

Birdjaguar

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I'd appreciate any help you math smart guys can give me on this...

Situation: A trackhoe weighing 20 tons is on top of a flatbed trailer and heading east on Interstate 70 near Hays, Kansas. The extended shovel arm is made of
A36 steel and the approaching overpass is made of commercial-grade concrete, reinforced with 1 1/2 inch steel rebar on 6-inch centers in a crisscross pattern layered at 1 foot vertical spacing.

Problem to Solve: When the shovel arm hits the overpass, how fast does the vehicle have to be traveling to slice the bridge in half? (Assume no effect for headwind and no braking by the driver...)

Extra Credit: Solve for the time and distance required for the entire rig to come to a complete stop after hitting the overpass at the speed calculated above.

Thanks.
 
These illustration may help: :mischief:
 
warpus said:
Not enough information.
Click to expand...
Well, you could look at the pics then round to nearest 10 mph. :p
 
Actually fairly simple...

mv(final) = mv (initial) - dmv (collision)
where dmv can be derived from the shear strength of the bridge (unfortunately comprised of complicated material and structure so I havne't a clue ) Assuming the cargo on the flatbed has enough static friction to overcome the impact let alone retain enough momentum to slice through a width unknown section of concrete, which I highly doubt, I'd have to assume there's something fishy about this problem.

As for the special credit portion, I'd assume it would be dependent on how quickly the driver notices the crash and twisted wreckage bouncing around behind him.

Good luck. :lol:
 
Birdjaguar said:
Well, you could look at the pics then round to nearest 10 mph. :p
Click to expand...
Why do I get the feeling that the "engineering problem" doesn't really matter, and you just wanted us to look at the pics? :)
 
heh, come on, we've all been there. driving normally with a 20 ton piece of equipment on the back of your truck and you see an overpass and go "heh, yeah I'm gonna cut that in two..... but first, what speed much I reach"

I bet the driver just couldn't explain that one to his boss
 
malclave said:
Why do I get the feeling that the "engineering problem" doesn't really matter, and you just wanted us to look at the pics? :)
Click to expand...


doh hehehe... I never even looked at those lol. :crazyeye:
 
Perfection said:
How fast was that guy going?
Click to expand...
Yes, that was the original question. :D
 
Why calculate from scratch, when you can eyeball it and say "about double whatever that guy's speed was about 20ft back from where he's at now"?
 
malclave said:
Why do I get the feeling that the "engineering problem" doesn't really matter, and you just wanted us to look at the pics? :)
Click to expand...
:hatsoff: ...
 
I am confused by the pics. In all three pics, the angle of crane arm is the same; that is, we are looking at all three views from the same side of the road, and not looking from the opposite side.

In the first pic, the direction of travel is ambiguous, but note the pedestrian railing on the right side of the bridge is not broken, implying the the crane came from our left. The side of the road that it is on would imply it came from our right.

In the second pic, we are still looking from the same side of the crane, but we can now see the left side of the pedestrian railing, which is also not broken, which would imply that the crane came from our right.

In the third pic, we cannot tell whether the rubble on the bridge is a groove carved by the crane boom, or detritus thrown forward from the collision, but it does confirm that the pedestrian railing on the right is still intact.

It almost looks like the crane boom came up through the bridge during impact, so as not to break the pedestrian railing on either side. Or, of course, the pictures are fakes.
 
You had me all confused then:confused: . I think they are fakes but not for the reason you gave, I don't think the truck could ever of gone fast enough to go through concrete like that. I've never seen trucks like that doing any more than 55. But they are limited by law in this country I believe not sure about US.

I think your getting confused in your perspectives there not all on the same side of the road.
 
The driver of a semi-tractor trailer that was hauling a track hoe excavator on a flatbed misestimated the clearance at an overpass, and the boom of the hoe collided with the overpass and knocked a 45-foot gap through the deck of the bridge.


Some misestimation!

Maybe he's a creationist.
 
Padma said:
NOT faked.

;)
Click to expand...

Wow... That is a very surprising thing. I applaude the guy for actually doing that kind of thing. A real pioneer for us idiots. :)
 
So which way was he going into the bridge? With the boom leaning into the bridge, or with the boom leaning away from the bridge?
 
Veritass said:
I am confused by the pics. In all three pics, the angle of crane arm is the same; that is, we are looking at all three views from the same side of the road, and not looking from the opposite side.

In the first pic, the direction of travel is ambiguous, but note the pedestrian railing on the right side of the bridge is not broken, implying the the crane came from our left. The side of the road that it is on would imply it came from our right.

In the second pic, we are still looking from the same side of the crane, but we can now see the left side of the pedestrian railing, which is also not broken, which would imply that the crane came from our right.

In the third pic, we cannot tell whether the rubble on the bridge is a groove carved by the crane boom, or detritus thrown forward from the collision, but it does confirm that the pedestrian railing on the right is still intact.

It almost looks like the crane boom came up through the bridge during impact, so as not to break the pedestrian railing on either side. Or, of course, the pictures are fakes.
Click to expand...

I agree! I'm confused too, which side of the bridge was hit?
 
It doesn't look like he made it through the bridge. Instead, what you're seeing is cracking/debris forward of the impact point.
 
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