Culvert design analysis

[livingwaterman]

I just got done reviewing the open channel chapter in the CERM for the PE exam. I thought it was ok until it got to the culverts. I thought that section was criptic and if you actually tried to use their methods to size a culvert you would take a lot more than 6 minutes even on the simpliest of designs. I would recommend you downlaod and print the following and become familar with it if you are anticipating culvert design/sizing problems:

http://isddc.dot.gov/OLPFiles/FHWA/012545.pdf

This is from FHWA and was last updated in 2005. Understanding the nomographs may be especially useful considering the press for time.

 

[IlPadrino]

I just got done reviewing the open channel chapter in the CERM for the PE exam. I thought it was ok until it got to the culverts. I thought that section was criptic and if you actually tried to use their methods to size a culvert you would take a lot more than 6 minutes even on the simpliest of designs. I would recommend you downlaod and print the following and become familar with it if you are anticipating culvert design/sizing problems:
http://isddc.dot.gov/OLPFiles/FHWA/012545.pdf

This is from FHWA and was last updated in 2005. Understanding the nomographs may be especially useful considering the press for time.

My advice is to ignore culverts... unless you're particularly fond of them. I don't think the juice is worth the squeeze. Of course, given this is free advice, it may be worth NOTHING (or worse, cost *YOU*)!

 

[jeb6294]

If your exam is like mine [SIZE=18pt]there will be culvert questions on the exam[/SIZE].

They especially like to throw a couple in there that ask for a minimum culvert size to carry XX cfs. They will even be so helpful to give you every little bit of information you will need to make it a simple plug-and-chug type question. The trick is, your answer may come out to be 6.15" so when your answer choices are 4", 6", 8", or 10" some people rush to pick 6" because that is obviously the closest to the answer you got. The correct answer would be 8" though because, while 6" is closer to what you got, according to the question you would have to bump that up to an 8" to actually get the correct flow.

 

[Daisy]

What I found is that in the 'real world' my culvert sizing did not match CERM, however, for the exam, I plan to size the culvert per CERM guidelines...not sure that makes a difference to anyone or not, but I've been told that on the exam, do problems how they are done in the CERM for the correct answer.

I just looked at the downloaded material...that should help on the exam, potentially for the non-quantitative questions. Thanks for the link.

 

[IlPadrino]

If your exam is like mine [SIZE=18pt]there will be culvert questions on the exam[/SIZE].
They especially like to throw a couple in there that ask for a minimum culvert size to carry XX cfs. They will even be so helpful to give you every little bit of information you will need to make it a simple plug-and-chug type question. The trick is, your answer may come out to be 6.15" so when your answer choices are 4", 6", 8", or 10" some people rush to pick 6" because that is obviously the closest to the answer you got. The correct answer would be 8" though because, while 6" is closer to what you got, according to the question you would have to bump that up to an 8" to actually get the correct flow.

But how long did it take you to work the problem? My point about the juice and the squeeze was that culverts represent some of the longest to solve.

 

[jeb6294]

But how long did it take you to work the problem? My point about the juice and the squeeze was that culverts represent some of the longest to solve.

Because the question is designed to make sure you pick a culvert that is actually large enough and not just the one that's closest to your answer, these questions are generally very easy. Probably looking for a pipe running full with every bit of information you'd need to put in the equation and get an answer in about 15 seconds.

I understand your point if you're not focusing on WR/Environmental, but at the same time I wouldn't say to ignore culverts completely...just make sure you know the basics.

 

[IlPadrino]

Because the question is designed to make sure you pick a culvert that is actually large enough and not just the one that's closest to your answer, these questions are generally very easy. Probably looking for a pipe running full with every bit of information you'd need to put in the equation and get an answer in about 15 seconds.
I understand your point if you're not focusing on WR/Environmental, but at the same time I wouldn't say to ignore culverts completely...just make sure you know the basics.

I agree with knowing the basics... I was talking about doing design work that requires you to determine if it's inlet control or outlet control, headwater elevation, etc. Yes... don't leave any easy "plug and chug" problems on the table!!!