Concrete Filled Pipe Bollards
Concrete Filled Pipe Bollards
(OP)
How do you analyze the bending capacity of a steel pipe filled with concrete? For example, I need to evaluate the capacity of an 8-inch double extra strong steel pipe filled with concrete that is 2'-8" tall, embedded in the ground. I thought of converting the steel pipe to concrete via transformation, but that didn't seem right.
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
This looks like a question for a highway design engineer.
RE: Concrete Filled Pipe Bollards
If you wanted, you could convert the compressive area of the concrete to an equivalent (small) steel area, but it should have minimal effect on the answer. You might also consider how you know the concrete is actually bonded to the wall of the pipe, which is what this assumes.
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
Most bollards are psychological barriers...not physical barriers. A 5000 lb object hitting a pipe at 30 mph - bollard loses.
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
Don't forget that the system doesn't need to be designed for repetitive occurances. If the cables yield, but stop the intruder, they can be replaced.
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
Also, the barrier you are talking about seems to be very similar to what highway designers use - AASHTO in the US, and these are usually set up as standards because they aren't usually designed with algorithums but trial and error field testing with real vehicles hitting the side barriers at set speeds. You might try AASHTO or associated sites for this.
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
Keep in mind that from a security standpoint, barriers are designed to either absorb or deflect a potential threat. That said, a barrier should be designed be deformed on impact. The owner or other governing authority should dictate what is acceptable.
I have worked on a number of security projects where barriers also created legal issues. For example, if you were to design a barrier to stop a vehicle dead in its tracks at 30 mph, there would be SEVERE injuries to the occupants (even with airbags). There have been similar lawsuits (some frivolous lawsuits) against various DOTs for highway barriers that resulted in injury, death, etc.
On the other hand, if the bollard is just for a store parking lot, any time spent designing a bollard would be a waste of time and money. Use your best judgement.
Good luck.
RE: Concrete Filled Pipe Bollards
FalsePrecsion, I agree with your sense of logic. However, we are also bound by aesthetics (this is for a location in the US, not overseas). The 8-inch pipe dimension is the agreed-upon standard that I must work with. There is this constant battle between the security guys who don't want anyone inside and the architects who want everything to look pretty. Us poor engineers get stuck in the middle.
RE: Concrete Filled Pipe Bollards
Locate a #11 or so rebar so that it goes down the whole length of bollard and into the concrete pier foundation. Use super-high strength, non-shrink grout at least in the bollard.
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
Read the info posted by vmirat, about half way up. Bollards at 10' on center. 2 wire ropes. End posts to take direct impact or tension in ropes. (I assume the end posts are something other than these 8" dia. pipes) Theory - would the vehicle deflect the ropes, to produce a catenary effect, thus absorbing a large amount of energy (the bollards would be "rotated" out of plumb by a large amount). The tension in the ropes would be very large, to produce a more gradual full deceleration of the vehicle. See the other posts above mentioning cables and energy absorption.
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
RE: Concrete Filled Pipe Bollards
Make it with solid steel then.
Ciao.