Ah! Behold the masterful work of the Soviet Corps of Engineers!

Posted by Guest on Sat Jan 18 12:08:59 2014

I like how at the end you can see a pile of wooden planks that would've been far better to use.

Posted by Guest on Sat Jan 18 12:53:22 2014

Slavs.

Posted by Guest on Sat Jan 18 16:20:12 2014

Scratches head

Posted by Guest on Sat Jan 18 22:13:23 2014

Worked perfectly

Now there are three easy to carry pieces.

Posted by Guest on Sat Jan 18 23:28:36 2014

Of all the 7 billion people on Earth, these guys know the least about concrete.

Posted by Guest on Sun Jan 19 01:28:04 2014

All three of them shrug, legitimately wondering how that did not work.

Posted by Guest on Sun Jan 19 03:50:44 2014

cement

I know the fourth least about cement: Why doesn't this work, and what would be better?

Posted by guest (guest) on Mon Jan 20 03:23:41 2014

"Why doesn't this work, and what would be better?"

Easy question, not quite as easy to answer.

Why should you not drop an egg from three feet onto the floor? Because it would break, as anybody who knows the least thing about eggs could tell you. But why would it break? Because its shell can't withstand the forces that act upon it when it hits the floor. But why can't it? What happens in the shell that makes it break? Well, how deep do you want to delve into physics and material science? You can look closer and closer, but once your're on the level of quarks and gluons, you might decide that you're past what's relevant for your everyday concrete pipe handling.

That pipe, laying on its side, can bear its own weight, but not a terrible lot more. Dropping it from several feet means that it will get squished under a multiple of its own weight when it hits the ground. What should they have done? Pretty much anything that doesn't involve dropping the thing onto its side (crane, ramp, or whatever else that was apparently not available). ...

Easy question, not quite as easy to answer.

Why should you not drop an egg from three feet onto the floor? Because it would break, as anybody who knows the least thing about eggs could tell you. But why would it break? Because its shell can't withstand the forces that act upon it when it hits the floor. But why can't it? What happens in the shell that makes it break? Well, how deep do you want to delve into physics and material science? You can look closer and closer, but once your're on the level of quarks and gluons, you might decide that you're past what's relevant for your everyday concrete pipe handling.

That pipe, laying on its side, can bear its own weight, but not a terrible lot more. Dropping it from several feet means that it will get squished under a multiple of its own weight when it hits the ground. What should they have done? Pretty much anything that doesn't involve dropping the thing onto its side (crane, ramp, or whatever else that was apparently not available). Apart from the two tires being too close to the truck, that little bit of rubber and steel carcass isn't gonna be of too much help with breaking the 3.5 ft fall of what appears to be a ~1.5 ton pipe. The pipe reaches a speed of ~4.5 m/s; that equals driving your car into a wall with 10 mph.

The tensile strength of concrete is only about a tenth of its compressive strength, meaning that it you can stress it in a way that pushes the material together, but not in a way that pulls it apart. Pull it, twist it or bend it and it will easily break. That's why you rebar concrete with steel to hold it together. Steel can withstand the kind of forces that would break concrete.

Imagine a one inch thick steel plate. Maybe you could deform it with a sledgehammer, but you could never break it. But if that plate was made from concrete, you could not deform it, neither elastically nor plastically, but you could break it with not much more than a gentle tap of the hammer.

Dropping the concrete pipe like in the GIF means that there are bending forces - imagine the pipe being made from thin sheet metal and you see how the pipe would tend to be squished (both under its own weight and much more when dropped onto its side). When you bend something, there are regions with pulling and with pushing forces. Imagine bending a tree. On one side, the wood is being pushed together, on the other side, it's being pulled apart (which is where it will fail first). Concrete can't deal with being deformed and pulled apart.

Every physical property of a material can be measured and expressed in numbers. Knowing the exact type of concrete, one could, for example, calculate from what height the pipe would survive a fall.

Posted by Guest on Mon Jan 20 15:34:32 2014

Concrete has interesting properties

Concrete (that is not reinforced) has insanely high compressive strength, but is very brittle and has zero tensile strength. You can squeeze it all day long and do almost no damage, but the second it takes a sudden jolt or is stretched, it breaks. When it connects with the tire, the material would try to deform to an oblong shape. However, that requires stretching the material, with the most force at 0, 90 180 and 270 degrees. As the concrete is not reinforced, and is forced to stretch, it breaks at those points until the tension is relieved. (Which is why it breaks into 3 pieces not four).

Posted by Guest on Mon Jan 20 16:36:15 2014

Gravity's the biggest reason this doesn't work; there's probably some bounce directed onto a small area on the surface of the pipe, but the rest of the thing is still affected by the potential energy and is going to essentially sheer off (I'm simplifying things, but that's, TMK, the gist of it).

As to what would work better... a crane? A ramp? One of them hydraulic lifts you see at the back of some trucks? There are many options to consider before "throwing it off the end and hoping for the best."

Posted by Guest on Mon Jan 20 17:01:27 2014