Residential Parking Retaining Wall Barrier

[XR250]

A customer needs to replace a residential timber retaining wall adjacent to a concrete pad parking area.
It is a 4 foot drop from the parking area to grade below.
I am proposing replacing it with 12 inch CMU or 8" cast in place concrete, tying it to a new slab and running it long to provide a guard.
Is there any way around the 6,000 pound requirement on the guard rail? Would adding a curb a few feet back help?
Also, how wide of an area can I distribute the 6,000 pound point load? I have read 45°, but that seems a little conservative.

 

[structSU10]

The building code requires the guard if the drop is over a certain amount - IBC 406.4.2 requires it for anything more than a 1 ft step. I dont think there are any provisions related to this in the residential building code.

Not sure what else may govern or give you a different direction but I would provide for it myself.

 

[BridgeSmith]

The AASHTO bridge design spec, particularly section A13.2 and A13.3 may be of some help with the distribution length of the load.

You could also consider the use of a structural "moment slab" on top that's integral with the railing, allowing you to use the lateral thrust and overturning resistance provided by the weight of the vehicle.

That said, the loading, even the requirement for a guardrail at all, seems ridiculous for a residential parking area, since the vehicle impact speed expected should be <5 mph. A curb or parking block should be more than adequate. Of course, that's just common sense, which doesn't often find its way into design codes and specifications.

 

[AK4S]

How about using highway W-beam guardrail?

 

[XR250]

Thanks y'all. I have a call into the building official to get an interpretation.