Vertical Clearance Above Roadway 1

[Hokie93]

I am working on a multi-story building project that includes a portion elevated above a roadway/drive aisle and I am seeking opinions as to the minimum clearance that should prudently be provided between the road surface and the overhead structure. The project is subject to IBC 2012 and I have not been able to find a specific requirement in IBC applicable to this condition. Likewise, the project architect and other colleagues I have queried have all pretty much shrugged their shoulders as to any "requirement". If AASHTO were applicable (I don't believe it is; or am I mistaken?), the minimum clearance would be 14'-0". This project is located in the eastern United States. The portion of the structure located above the roadway is several stories and an occupied structure (think office building). The roadway in question is public (not an interstate) but is a low-speed road/drive aisle within an office park. The road leads to an from a parking garage.

 

[SlideRuleEra]

The US Federal Highway Administration requires 17 feet clearance for pedestrian overpasses. That is the greatest clearance they list. Suggest going with at least 17 feet. As a bridge contractor we repaired a low highway bridge that had been stuck by a high load. This type collision does significant damage... do what it takes to avoid. Here is the link:
FHWA Vertical Clearance Requirements

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[bridgebuster]

Are there any state/local regulations regarding minimum clearances for this this type of road? I agree with SRE go with the FHWA policy of 17', it gives you something to hang your hat on. In NY we use 17'-6" for ped bridges (FHWA 17" + 6" for future paving).

This is a recent collision from a superstructure replacement project I'm finishing up. Very low clearance & trucks aren't allowed on the road but it's still been getting hit on average 15 to 20 times a year for as long as anyone can remember.

 

[BridgeEI]

I believe FHWA says 14' min for local/collectors. It would be covered in the AASHTO green book. However I agree with the guys above. When you get a vehicle impact things get messy and expensive real quick. I would imagine it would be even more expensive it were to hit a building.

A quick Google search comes up with this

http://safety.fhwa.dot.gov/geometric/pubs/mitigationstrategies/chapter3/3_verticalclearance.cfm

 

[LittleInch]

Probably depends if you can build a seriously strong structure just in front of it to take the inevitable impact damage.

Even then it depends on the speed of the vehicle.

A local railway bridge got hit a few years ago by one of those garbage trucks which have a front set of arms to lift industrial sized bins over the roof. Due to the speed of the truck the arms hit the substantial steel structure to prevent such things, went under that and wedged itself under the bridge, blew out the tyres(!) and they took all night to cut the thing to pieces to get it out.

what's 3 or 4 feet to prevent that happening?

The standard height in Europe is 5.1m (16.7 ft) so 17ft seems to to be the magic number.

Height of trailers seems to be going up - watching a 4.95m trailer go under a 5.1m motorway bridge is a little heart stopping at times....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Teguci]

If you can restrict the height of vehicles entering this road, then I suggest placing a headache bar at the entrance to this public road that posts the allowable vehicle clearance allowed on a brightly painted, concrete filled pipe set at the clearance height (after all, that's what they did at the parking garage - I hope). If you can't restrict the height of vehicles, then I suggest providing the highway clearance allowed by your state.

 

[bridgebuster]

Headache bar - Ouch!

The truck -or rather, what's left of it - that hit the bridge I cite.

 

[3DDave]

Eleven foot Eight - The can opener bridge.

http://11foot8.com/

It's a great way to spend a few minutes contemplating low bridge construction. Like this one - listed as #103.

http://11foot8.com/boxtruck-crashes-and-leaves-present-at-the-11foot8-bridge/

Technically, they don't hit the bridge, but a beam placed to protect the bridge, which apparently go hit a lot.

They have a 'Crash Art' store with fragments of vehicles and trailers that did not make it the entire way under the bridge.

 

[dicksewerrat]

There used to be a RR overpass in downtown Minneapolis. That thing caught and held many vehicles. I think the clearance was 11'9" but not sure. Many flat tires later they removed the overpass. No rail traffic there any more. Great for spectators though. Progress takes a lot of fun out of stupid drivers.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[IRstuff]

Wow! That protection beam was MANLY! That truck never stood a chance of damaging the overpass. That was barely a month ago.

TTFN
I can do absolutely anything. I'm an expert!
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[hokie66]

Policeman pulls up and questions truck driver stuck under bridge. "Had a bit of an accident, did you?" "Nah, just delivering this bridge."