ASCE 7-10 section 4.5.3 Vehicle Barrier

[casasf]

Is the 6000 pounds listed in the section strength level or service load? Since this is an impact load, is there an increase in the stress allowable?

 

[mike20793]

Chapter 4 loads are service so you need to factor them appropriately based on your design methodology. I'm not aware of any material allowances for stress increases.

 

[casasf]

Thank you.

I have to change my anchors in Hilti Profis to strength level forces by applying 1.6 factor for live load, which will give me a shear of 9600 pounds and a moment of 259,200 in pounds.

My other weak link is going to be welding the post to the base plate.

Thanks again.

 

[MacGruber22]

Can I ask what you are protecting? That minimum load is essentially a bump load - a car striking the bollard at approximately 5 mph.

-Mac

 

[casasf]

What I have is a ramp going to the second floor of the parking garage. The slab is discontinuous at the ramp. We are trying to protect the cars from falling down into the ramp.

 

[RickyTickyTavi]

You may want to consider barrier cables or something that could actually stop a vehicle.

Like Macgruber stated, bollard design is basically a bumper. A 2000 lb car hitting at the specified height an any real appreciable speed is going to careen over the edge of that ramp along with any bollard that was meant to stop it

 

[casasf]

Thank you for your input.

 

[MrHershey]

You may want to consider barrier cables or something that could actually stop a vehicle.

For what it's worth, most barrier cable designs also result in about a 5 mph speed, so you're in the same boat there.

Most barriers are only designed for accidental bumps. If you want something heavier you'd really need to go to a concrete barrier or a heavier steel barrier similar to what is used for highways.

 

[casasf]

Thank you MrHershey.

 

[SEJohn]

You may want to check out this article from Structure Magazine on the topic.

https://www.structuremag.org/wp-content/uploads/2014/08/C-StructuralPractices-Iqbal-Oct081.pdf

 

[casasf]

Thank you SEJohn. Eye opener.

 

[MacGruber22]

For what it's worth, most barrier cable designs also result in about a 5 mph speed, so you're in the same boat there.

To be fair, when intermediate and end supports of PT cable barrier are building columns, it is not necessarily difficult to design for much higher impact forces. Cable strength is rarely a controlling limit, and concrete columns can take a ton of lateral force.

-Mac

 

[casasf]

Thank you Mac.
I have a condition where there is no column at one end. I have decided to go with steel HSS vertical and horizontal member. It is an old garage where the concrete strength is 2,620 psi. Using Hilti Profis anchor software, the anchors are working using HIT 500 v3 with A615 #4 bar

Regards,

Casasf.

 

[bones206]

If you can, you might want to design the anchors and welds to develop the yield strength of the barrier members increased by some factor like 1.2 or 1.5 to account for strain rate and higher than specified material strength. That way your barrier can hopefully absorb some impact energy without breaking off at the supports. It may not be feasible or economical to do so in your case.

 

[casasf]

Thank you Bones206.

 

[JLNJ]

You might give these guys a look. They seem to have some good testing and data to back up their numbers.

http://www.slowstop.com

 

[casasf]

Thank you JLNJ. Interesting product.

 

[MacGruber22]

In circumstances such as this, we have re-built the slab around the bollards, added fully-developed rebar, and thickened slab as needed.

If you can, you might want to design the anchors and welds to develop the yield strength

Yes. with adequate bolt tear out, the welds and anchor capacity are the most critical. Base plates are much more forgiving and should be able to act in a ductile manner as long as the bolts and welds have a capacity akin to Overstrength design. Mitigating rupture and conc breakout is the name of the game - yielding can be tolerated much easier.

It is not worth skimping on true barrier design. I have seen TWO cars fly through barriers on a parking garage 4th floor, and the forensics determined they were only accidentally accelerating from the stall right in front of the barrier. Also, the barriers were found to be sufficient to meet the minimum IBC requirements.



-Mac

 

[MacGruber22]

JLNJ - Based on their design tables, I wouldn't trust them for elevated floor barriers.

-Mac