Vehicle Surcharge on Basement Walls

[KootK]

For generic basement wall design, I've encountered three design philosophies regarding vehicle surcharge:

1) None at all unless there's a traffic surface nearby.
2) 50 psf so that folks could park cars on the lawn without having their basements collapse.
3) 250 psf so that a fire truck could pull up beside the house if necessary.

Three seems pretty punitive although it feels peculiar to suggest that fire truck couldn't pull up beside the house should the need arise.

What do others do in this regard? Can we safely assume that all fires will be fought from the street?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[JedClampett]

Unless the area is inaccessable, I put in the two foot (250 psf?) surcharge. Not only for fire vehicles, but for construction activity or change in use.

 

[manstrom]

1 for me.

If you look up ACI 332, which is the bare bare minimum for residential concrete, they don't add a surcharge. It's not like you see these things failing all over the place. I think it is reasonable. A car surcharge would easily be distributed over a longer section of the wall.

The thing you should be concerned about it how to brace the top of the basement wall from kicking in. Standard IRC details are kind of a joke. How much lateral restraint should you have at the top of a wall? 250 plf or so? IRC standard details only require a 1/2" bolt at 6' o.c. At one point they fixed the code, then they unfixed it. I don't design it that way, but plenty of people do and can get away with it per code.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[jayrod12]

In my general experience, if I've provided min. steel, my wall has the capacity to resist even a 250 psf surcharge.

Often your soil pressure can overtake that surcharge pressure by the 4 ft depth. In the end it only increases your total loads by a small portion.

 

[BUGGAR]

30 psi x 144 sq in = 4320 psf / 120 pcf = 36 ft of soil

 

[SteelPE]

This is an issue I have struggled with previously in commercial construction. If you are talking about residential construction I don't really see the fire department pulling their expensive rig next to a burning house. I think they would be far enough away such that the wall would see no additional load from the truck.

In commercial construction I have had arguments with other engineers in the past. I typically try to accommodate an additional 100psf next to the building to allow for equipment during construction and while in service. I know other engineers who do not provide any additional load. I think, depending on the type of project, this falls under engineering judgment.

 

[KootK]

Thanks for the recommendations guys. 2' of surcharge it is. This particular application is commercial. I'll have to get my hands on a copy of ACI 332. Somehow, I wasn't even aware of that document's existence.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[RFreund]

I would suggest snow load as a minimum rather than zero (assuming snow is applicable).
Residential usually 50psf min.
Comercial usually 100psf unless near a road or some other type of pavement then 250psf. Although in most cases 250psf is easy enough to achieve.

EIT

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