Grade Change with out vertical curve 1

[2civil]

What is the max grade change with out a vertical curve?

We are reviewing a Parking Garage submittal by another engineering firm. The slope on a ramp is 13% with no vertical curve (one level to the next). We talked to the engineer and he said it was okay b/c the speed limit was 10 MPH. We told him that max would be 4-5% change in grade.

Is anyone familiar what criteria would govern?

 

[BigDog23]

Grade change in this case can vary, I don't think I would hold an algebraic difference as the determining criteria, because it holds more to street design than this circumstance, but rather think of this on the practical side. First, what are you using the parking for, is there parking on the ramp or handicap parking available on the ramp? If so ADA comes into play and the max grade cannot exceed 12:1. Usual maximum grades on parking do not exceed 5% because of convience to the user, no slamming doors, etc. However, it is understanble a ramp would exceed this due to limited space. Think of this regarding the 13% grade, most homebuilders create a maximum 15-18% slope on driveways for functionality.

Okay so practicality usually has no place in public entities and consultants want to hear cold hard reasoning if they have to change a design. What is the maximum allowable driveway grade in your area (even a commerical entrance driveway standard)? It would stand to reason that these were created using similar vehicular shapes (lengths, heights, clearence, etc) and vehicles in the parking garage should be able to attain those grades with out damage, and that criteria should be justifiable.

Something to remember if you are a public agency, and the garage is under private ownership, it would appear the PE consultant is under liabilty here to create a functional safe environment. I would be careful where you push him/her regarding design especially if there are no documented design criteria/standards.

Hope that Helps,

BD23

 

[snafuman]

If I understand you correctly, they are proposing going from 13% grade to 0% with no vertical curves or successive grade changes as a transition. Therefore vehicles with low undercarriage clearances would high-center on the grade break. My quick calc says that a vehicle with a 12'long wheelbase would need 0.8 feet of clearance not to hang up on this grade break, but only 0.3 feet for the 5% grade break you are proposing.
Have this other engineer measure a few cars (including his own). Unless he drives a pickup, this should convince him.

 

[2civil]

Yeah. We ended up compromising. I think he was in a sticky situation as the ramp was already poured.

I was referred to ULI parking garage criteria which states that grade changes up to 15% should be transitioned by half the grade change over at least 15ft.