Unconstrained Bollard Design Check

[Blackfairy]

Can someone check and see if I am doing it right.

I am designing a steel bollard that will take 6K impact at around 2.25ft from the ground. I am using the pole/embedded post design unconstrained. I am using 150 psf of lateral pressure and doubling it as per IBC 1806.3.4. Since it is unconstrained, my allowable lateral soil-bearing pressure will be 1/3 x depth x 150 psf. Using 1.5" diameter casing, I found that my depth is around 11 ft or so which is too deep not to mention that the allowable vertical bearing pressure will exceed the 2000 psf due to little area and high weight of the casing.

So I changed it to 2.5' diameter and got 9ft of embedment and my vertical bearing pressure capacity ratio is now less than 1. But looking at it, is it normal to have 2.5' of casing on bollards 9ft deep for a 6K impact? If that is the case I might have to reinforced it and not just fill it with grout since it's a huge diameter. For comparison, the other bollard that is constrained by a slab on grade, I calced it 1.5ft diameter 6ft deep. That 1/3 depth for allowable lateral pressure for unconstrained is what is really is the big difference between constrained and unconstrained.

 

[hemiv]

Is there a very special need for this bollard to remain in place after such an impact? If this is for a typical parking lot or warehouse bollard, it is normal to assume foundation failure in the event of a collision. Bollards tend to function primarily as visual warnings, and secondarily as a structural barrier. There will always be a big impact which could take one out, you just want to make the thing being protected is unharmed.

 

[Blackfairy]

Is there a very special need for this bollard to remain in place after such an impact? If this is for a typical parking lot or warehouse bollard, it is normal to assume foundation failure in the event of a collision. Bollards tend to function primarily as visual warnings, and secondarily as a structural barrier. There will always be a big impact which could take one out, you just want to make the thing being protected is unharmed.

It is just protecting electrical panels on the that controls a fish release system. The place is not public, the only thing that can hit the bollards are the trucks that carries the fish into the fish release pipes while backing up or maybe a electrical maintenance truck while they are checking the electrical panels.

If that is the case how should I design it though Should I just design it the same and just make non conservative assumptions?