The basic rule is that cars are designed to crush at about 6000 lbs with
a lot of ductility. That means at lower speeds the impact is 4 to 6 k
with little damage to the car. The higher the speeds result in the same
force but more car damage.
Another interesting fact is that the Calif. Highway Dept have officially
recognized that curbs are only to control water run-off. They do not
work to stop cars. The curb causes more injuries in fall accidents than
protects from cars jumping the curb.
The new official plan is to not use bollards and rails and not allow
curbs, using other methods to control water run-off.
I found that a bollard in sandy clay will need about a ten foot deep
hole if one were to allow more than 1/2" movement and increase soil
capacity by a factor of 1.33.
Is the seismic factor of 1.33 for soil strength usable for auto impact
loads?
The steel pipe needs to be more than a 6 inch diameter to extend down to
he center of soil resistance. These holes can not be drilled close
enough to stop a car passing between them, so the only solution is to
build multiple bollards on a concrete mass, like grade beam, with
horizontal steel and stirrups. The pipe size can be reduced but probably
needs be tied into the grade beam steel.
David Merrick, SE
Sacramento
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