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Gutter Spread: Different results in Express vs Storm Sewers

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Message 1 of 3
nickgriffin
372 Views, 2 Replies

Gutter Spread: Different results in Express vs Storm Sewers

I noticed a discrepancy when checking the gutter spread results between Express and Storm Sewers. See attached files. The issue appears to be in the longitudinal slope data entry. The output almost matches when I enter the longitudinal slope in the same format in both programs (Either in ft/ft or %). If I calculate manually using the formula for depth in the computational methods (using % for all slopes) I get the same answer as Express when entering in ft/ft?????

 

Which program is correct? Why does the output not match exactly between the programs?

 

Please help!

 

AutoCAD Civil 3D 2015 SP2

 

Please note I am attempting to change the file extensions to .doc so they will upload...

 

-Nick

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Message 2 of 3
nickgriffin
in reply to: nickgriffin

After spending more time on this I decided to model an inlet in SSA. All results agree if longitudinal slope is entered as follows:

 

Express: enter as shown in dialog; %

Storm Sewers: enter as %, not as ft/ft as shown in dialog.

hand calc check using formula: enter as ft/ft.

 

Conclusion: Storm Sewers gives incorrect results if you enter longitudinal slope as ft/ft.

 

Can someone verify? 

Message 3 of 3
Zach
in reply to: nickgriffin

Good Day,

Did you enter the road and gutter cross slopes in %, as well, in Storm Sewers even though the dialog box units are ft/ft?  Did you also notice any discrepancies for inlets in sag for spread results since it doesn't take into account longitudinal slope? Or is the discrepancy related to spread results between programs and hand calcs only observed with the inlets on grade due to the longitudinal input in Storm Sewers needing to be in percent format vs. ft/ft? 

 

Do you have a preferred method for calculating inlet capacities and spread based on your experience?

 

Thank you for your help. Your input is greatly appreciated.

-Zach

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