pipe bollards
pipe bollards
(OP)
I have been asked to design a single pipe bollard to stop a 36 kip bus traveling at 4 miles and hour. My experience with pipe bollards has been for protection of dock doors and equipment. Usually 6" to 8" pipe embedded 3' to 6' in the ground encased in concrete creating a deadman, not really designed. I talked to a bridge engineer who said highway bridge rails are designed for a 10 kip load applied 2'-9" above the pavement and can be distributed over 5' of rail. I've looked back at old physics and dynamics books for equations. I know I will have a completely inelastic or plastic impact. I know that in the gravitation system the 36 kip bus must be converted to slugs. All of the conservation of momentum formulas and examples, that I've found, deal with movement after impact regardless of whether one was stationary before impact. Looking for reference material, guide lines, or applicable physics formula.






RE: pipe bollards
RE: pipe bollards
If you need reference material, look and see if you can find anything on "pipe whip". Members at nuclear plants are designed to withstand a certain speed and weight of pipe that whipped loose.
Then the only question is whether "small deflection" mechanics apply.
RE: pipe bollards
- that'l stop the bus...
Mike McCann
McCann Engineering
RE: pipe bollards
OR
they are meant to be a sacrificial element intended to warn a truck backing up that it has hit something prior to actually hitting the more precious building beyond it.
AASHTO only knows how to create guardrails against impact through actual physical testing.
F = ma doesn't do you much good since you don't know the decelleration value of a to get F. The decelleration could be almost any value depending on the "hardness" of the elements of the truck - If it hits on a bumper "a" is different than if it hits on the bumper between bumper-struts, etc.
RE: pipe bollards
Anyway, here's a link to a site that will help you calculate the force.
http://