- Engineering Question
Don’t know if it’s been done before, but I thought it would make an interesting question over Saturday morning coffee…
A backhoe weighing 22 tons is on top of a lowboy trailer and heading east on the Trans-Canada Highway near High River, 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.
When the shovel arm hits the overpass, how fast do you have to be going to slice the bridge in half? (Assume no effect for headwind and no braking by the driver.)
Posted 6 years agoMidlandTrailquestsGrahamMember
Interesting to speculate on what happened there…
The backhoe boom would have been facing forward and angled up slightly.
The fold in the boom hit the edge of the bridge just below the stepped out section.
The force of the impact flipped the boom back and up, through the deck of the bridge.
It also forced the machine downwards, crushing the trailer.
The sudden braking effect on the trailer sheared the truck to trailer coupling.
So, in answer to the original question, in a way, it hasn’t sliced the bridge in half, it’s punched a hole through from underneath.Posted 6 years ago
Still some impressive physics going on there though. 😀motivforzMember
Interesting! He’s got about half way through there. Looking at it purely in the energy form, kinetic energy = 0.5*mass*velocity^2. Mass remains constant so you want the velocity^2 term to be about double, to give twice the amount of energy to plough through twice as far. That speed would be 1.4 ish times the speed that he was going.
The list of assumptions for the above calc is quite long.Posted 6 years ago
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