culvert guard rail 1

[kipfoot]

I'm working on a single family residence (in the US) that has a culvert over a stream. The owner would like to put a guardrail on each side of the driveway.

Am I correct to believe that this guardrail may be designed as a pedestrian restraint (IRC) - not as a vehicle barrier (AASHTO)?

 

[bridgebuster]

Check with the local authorities; even though you're on private property you may have to design it for traffic loads. Also, your state DOT probably has a detail for your condition.

 

[ztengguy]

I would say you are correct that you dont have to design for impact.

 

[ACtrafficengr]

What size culvert is it? Box or pipe? Is it a vertical drop-off at the edge of the driveway or is there a clear zone?

Assuming a vertical drop-off, I'd want more than a handrail if it were my driveway. I wouldn't insist on Test Level 4 bridge rail. TL-1 rail is designed for impacts up to 31 mph and should be more than adequate.

Could you extend the culvert to provide a sufficient clear zone and avoid the need for rail entirely? The AASHTO Guidelines for Geometric Design of Very Low Volume Local Roads (ADT < 400) says a 6 ft clear zone is adequate for new low volume roads. That should suffice for a residential driveway.

 

[ChipB]

I've actually come across this before. I used two courses of Redi-Rock wall to form the barrier. It was relatively inexpensive, and decorative.

http://www.redi-rock.com

Absolutely no affiliation.

 

[TehMightyEngineer]

Great idea chip, retaining wall and guardrail all in one. Easy for a inexperienced contractor as well.

Maine EIT, Civil/Structural.

 

[cvg]

except that the redi rock does not form a vehicle barrier. any impact at all would damage it and not prevent a vehicle from going through. you would need a separate guard rail or reinforced concrete wall to actually function as the barrier with rock facing to look pretty.

redi rock guardrail

http://www.redi-rock.com/documents/retainingwalls/Guardrail Detail.pdf

redi rock concrete barrier

http://www.redi-rock.com/documents/retainingwalls/Guard Rail - Precast Barrier Block Details.pdf

 

[ACtrafficengr]

cvg, do you think a vehicle would penetrate a wall made of 1500 lb blocks at driveway speeds? To be conservative, say 20 mph and a 25 degree impact angle.

StoneStrong also has double-faced units. These are hollow and usually filled with gravel, but if needed they could be filled with reinforced concrete to lock them into the course below. On the other hand, that would make replacing damaged units even more difficult.

 

[kipfoot]

thanks to all for your thoughts.

@ACtrafficengineer, I think a TL-1 rail is what the owner wants to replace with something prettier. The civil engineer designed the culvert and existing rail but the owner has turned to the architect, and by extension me, to replace it with some weathering steel plates with water-etched lettering. I think the attachment answers your questions. Thanks for the terminology and reference. As a building structural, I'm not familiar with that realm.

 

[precast78]

How much soil cover does the culvert have? If it has enough soil on the top of it, you can just follow a typical standard of your DOT for guardrail. No calc necessary if you follow the standard. If the culvert barely has soil cover, you may be able to drive the posts each side of the span if it is a small culvert. If a car hit this barrier, it will not damage the culvert because it is not connected.

 

[ACtrafficengr]

Two thoughts regarding weathering steel:
[ul] [li]It will cause streaky rust stains on the concrete, which probably isn't the look the owner wants. There is an outfit that shows up at our annual E-week conference that powder-coats guiderail.[/li]
[li]Don't use it if the driveway will be salted in the winter. Salt rots weathering steel. But then again, you shouldn't salt gravel drives anyway.[/li] [/ul]

I don't think the Redirock or Stone Strong blocks will fit.

 

[ChipB]

Yeah..... No. It doesn't look like Redi-Rock would fit.

Agree with AC on the weathered steel.

Currently, it looks to be about 2 feet tall.

Architect is thinking too much, trying to make your job more difficult.
Here's what I see:
You've got a built up boulder embankment.
You've got what appears to be a split face CMU pilaster holding the gate.
You've got a tree that doesn't look as healthy as it should, probably got its root system in construction. Might need to go or it could fall on their new decorative "guardrail"

My thoughts:
Split face CMU Pilaster at both ends.
Split face CMU wall between the pilasters, turned driveway side along the top of the wall.
Back face of the CMU lined up with the concrete creek side.
Fuax rock veneer creekside
2" Capstone at the top of the wall (and pilasters.)
Drill and epoxy in the vertical reinforcing (Hilti HY 200)
First bond beam in second coursing (16") then every 16" thereafter
Hook the bond beams into the pilasters
4 courses would put you at 32" which is higher than it is currently
Provide an expansion joint, maintaining the horizontal steel, at the joint of the wall to pilaster. Pilaster will be on its own footing and will not settle at the same rate as the head wall.

The faux rock veneer will blend in nicely with the rocks of the boulder embankment. While this won't give then the wrought iron, weathered steel look of their gate, it will give them the look of their gates' pilasters

Just my thoughts,
Chip

P.S. They need to pressure wash their pilaster.