A Challenging Engineering Question For You!

[trainsdownunder]

A Challenging Engineering Question For You!

Conditions: A backhoe weighing 22 tons is on top of a low-loader trailer and heading east on the Trans-Canada Highway in Alberta. The extended shovel arm is made of hardened refined steel and the approaching overpass is made of commercial-grade concrete, reinforced with 1 inch steel rebar spaced at 6 inch intervals in a criss-cross pattern, layered at 1 foot vertical spacing.

     
Assumptions: No headwind effect and no braking by the driver.
     
Solve: If the shovel arm hits the overpass, how fast do you have to be going to slice the bridge in half?...
     
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    No? Well, I couldn't solve it either...but who cares; the pictures are great!

    P.S. The driver was on his cell phone...

[AndyGif]

seems they do this alot....  http://beaconnews.ca/calgary/2011/10/yellowhead-highway-closed-after-bridge-collapse-near-lloydminster/

more pics here http://www.oil-electric.com/2012/12/eleven-foot-eight-inches.html
just as well no rail traffic was about.....

[MikeDunn]

I'm struggling with the geometry on this one ...

The arm is way up, yes ?  The backhoe is (now) on the deck, so the elbow of the arm should now be lower than when it hit, yes ?

So why isn't there a great big hole at either one end or the other ...    It appears that it was driven upwards through the right-hand side, and not along ... 

{Edit}  Snopes reckons it's legit - but in Kansas, not Canada ... http://www.snopes.com/photos/accident/hoecrash.asp.  Still having probs with the geometry though !

[Edit 2] Well ... seems this took the bridge out of comission for 6 months !  They found more damage than expected, and removed the centre section entirely; recast a new piece in situ.  As to the geometry - found an answer  

"Damage occurred in two stages. First, the horizontal motion from right to left resulted in the arm cutting through the underside of the bridge only (the pedestrian guard rail was left untouched). At the same time, the impact rotated the backhoe CW until its tracks hit the underside of the bridge (see underside of bridge on the left). This CW rotation allowed the backhoe arm to pass under the right-hand edge of the bridge. Once in the middle of the bridge, the backhoe rotated CCW to settle into its normal horizontal position, and this rotation pushed its arm up through the middle of the bridge. Presumably, this surface is less strongly reinforced and easier to penetrate than the edges of the bridge."

[AndyGif]

hmm, geometry works fine for me.
cannucks drive on wrong side like the yanks and the rest of the uncivilised world.

Elbow of excavator (its not a backhoe, [jcb, to the rest of us]) hits the bridge side,
forcing the the ex down on the trailer.
trailer carries on, the arm is lifted and   forced back on to the engine bay of the ex.
It now cant go anywhere, truck and trailer carries on, dragging the now lifted arm through the bridge.
Damage on the other side of the bridge is from the bucket smashing in to the unside off the bridge on the initial hit.

As alexander the merecat would say "simples"

what we can infer from this:
is the tie down chains were strong and fitted well or the ex would have been shoved off the back of the trailer.
The pin on the fifth wheel(hitch) is bloody strong or it would have snapped off,  same can be said of the goose neck on the low loader trailer.
The Trucky was belting along the highway, lot of momentum.
The was a bloody loud clang......

[kaiwhara]

We had the same thing happen at Onewa Road bridge in Auckland about 4 years back. Caused major problems for ages that did!

[Geoff]

It looks like this is a regular event, the mind boggles wondering how fast the wagon was going to cause that kind of a gap, makes you wonder if it woke the wagon driver up lol.

[EtchedPixels]

I'm just trying to imagine what it looked like from the deck of the bridge seeing a backhoe smash through the tarmac and do shark impressions across the road

[Mustermark]

Wow... that would be one uncomfortable moment for the driver.

I can see the geometry.  The answer to the OP's question is 107.6 kmh.   

It's a heck of a mess.  Thanks for posting!