AASHTO Guardrail Impact Loads for H15 Truck

[Engrman]

Hi all, I have a Office/Warehouse project w/ truck docks in back as usual. The site requires an 1100 ft long retaining wall on the north, east and south property boundaries, which is also behind bldg's. Wall has a 3'-6" concrete guardrail on top. Truck access drive and loading docks are parallel to wall so if everyone is a good driver the wall should never be hit (yeah, right). '03 IBC indicates vehicle barrier systems for passenger vehicles shall be designed for a 6000 lb load acting 1'-6" above drive surface. I don't have an AASHTO code. What do they specify for a H15 truck?

 

[mjl23]

AASHTO LFD (last edition, 2002) shows P at the top of a 32" high barrier, where P = 10k per the footnotes. I don't see anything prescribed depending on the HS level. It shows P applied at the top of the barrier, so in your case, perhaps the barrier height should be used.

Current direction is to design per TL level (Test Level). Levels range from TL-1 (lowest) to TL-5 (highest).

Your situation doesn't sound like it would relate to AASHTO with respect to the expected speeds, which I would imagine should be lower than roadways. The height of your barrier is commensurate with TL-5 barriers, but areas with "low posted speeds" are applicable for TL-1.

 

[Engrman]

Thanks mjl. I agree it will be low speed. Barrier height is based on other requirements. I assume the 10k is unfactored. Since I don't possess an AASHTO code and I'm not a highway engineer, what are the requirements of TL-1 design?

 

[bridgebuster]

Take a look at this thread:

http://www.eng-tips.com/viewthread.cfm?qid=206304

 

[mjl23]

I don't know if bridgebuster's thread sorted you out or not.

The load I mentioned would be service (unfactored).

I don't really understand the intent of your question "what are the requirements of TL-1 design?"

Each level has a description.....and it actually goes up to TL-6 (my last post was incorrect). I think the way it works is, a DOT comes up with a barrier of whatever size/configuration, and then they test it against the specified loads to see if the barrier passes. Our DOT provides design forces (moment, horizontal shear, etc.) which are the design forces at the base of the barrier.

I'm not that familiar with IBC, but I don't know that applying AASHTO to your application in parts is appropriate.

You said something about a cantilever wall, so I suppose looking up your DOTs typical barrier isn't of much help?

Keep in mind, with the TL level loadings, they are designed for LRFD so called "extreme event", so a base phi factor of 1.0 is typically used. I say base because of the way phi factors are now adjusted when you check for max reinforcement requirements.