CFCivil
Civil/Environmental
- Jun 17, 2005
- 1
The local fire department has established a standard that sets the maximum approach/departure angle at 10.5%. I understand this to mean that I can not have an instantanious grade change of more than 10.5%. Lets say I need to transition between 2% and 15% grade at a residential driveway. I will no doubt need a vertical curve of some length. It is the determination of that length that I am wanting help with. It would seem that the mimimum limit of the VC length would be equal to a distance greater than the wheelbase of the longest wheelbase fire engine that the department would expect to fight a residential structure fire with. If the wheelbase were to be assumed to be 30', then a fire truck "centered" on a vertical curve g1=2% g2=15% with a VC length of 30'would be at a grade of (15-2)/2 = 6.5%. If the max rate of grade change of a VC is at the Midpoint of the VC then that would be the "worst case". 15%-6.5% = 8.5% comfortably under the 10.5%.
Does any of this hold water? Sorry for being so long winded?
Thanks for your thoughts,
CFCivil
Does any of this hold water? Sorry for being so long winded?
Thanks for your thoughts,
CFCivil