AutoCAD Civil 3D - Stormwater

Reply
New Member
CPeng78
Posts: 2
Registered: ‎12-27-2012
Message 1 of 4 (224 Views)

Bolted Manhole Rims and Closed Tank

224 Views, 3 Replies
12-27-2012 11:33 AM

Hello Everyone,

I need a little help. I had a chance to use the old StormNet software extensively in my previous company. This is my first time that I'm using it under AutoDesk. It appears to work simlarly. Please correct me otherwise. So now I'm trying to model a small but a bit of a complex system.

 

I have a modeling scenario where I have a storage tank with two orifices. The first orifice outlets to a 10 inch diameter pipe which eventually outfalls into a stormwater treatment area. This area will allow ponding. Due to site topography a portion of this pipe run will be pressurised with the outlet set just low enough below the 1st orifice elevation at the tank. The second orifice outlets to a 12 inch diameter pipe which connects to the underground storm drain system via gravity. This second pipe run will only take on water that exceeds the capacity of the first. With this scenario I have  a few questions:

 

1. In trying to model the bolted rims to make the portion of the system to work as a pressurrised system, my understanding is that I have to set the surcharge elevation (at the junction) high enough above the max rim elevation. I have set up the surcharge elevation high enough, trying different elevations and the max water elevation in all cases is exceeding the max rim elevation. What am I missing?

 

2. My storage tank is a close tank. Is there a way to ensure that is modeled as such or does the program assume is a storage node such as a detention pond?

 

Thanks in advance for your help!

 

Valued Mentor
fcernst
Posts: 1,088
Registered: ‎01-07-2011
Message 2 of 4 (215 Views)

Re: Bolted Manhole Rims and Closed Tank

12-28-2012 10:33 AM in reply to: CPeng78

1. In trying to model the bolted rims to make the portion of the system to work as a pressurrised system, my understanding is that I have to set the surcharge elevation (at the junction) high enough above the max rim elevation. I have set up the surcharge elevation high enough, trying different elevations and the max water elevation in all cases is exceeding the max rim elevation. What am I missing?

 

Nothing.

 

SurElev-MaxRimElev = pressure head uplift on manhole cover. Design restraints accordingly...

 

2. My storage tank is a close tank. Is there a way to ensure that is modeled as such or does the program assume is a storage node such as a detention pond?

 

Yes, set a high enough Maximum Elev to capture the max HGL expereienced in the tank for your system simulation.

 

 

Fred Ernst, PE
C3D 2015
Ernst Engineering
www.ernstengineering.com
New Member
CPeng78
Posts: 2
Registered: ‎12-27-2012
Message 3 of 4 (211 Views)

Re: Bolted Manhole Rims and Closed Tank

12-28-2012 11:42 AM in reply to: fcernst

Ernst and others,

Thank you for your response. In terms of these repsonses:

 

1. You stated "SurElev-MaxRimElev = pressure head uplift on manhole cover. Design restraints accordingly." - However, wouldn't the restraint desigm be based on "Max water Elevatiom (calcuated by model -  Max/Rim Elev"? If I use the Surcharge elevation as a starting point, this number will vary depending on what I enter. The help menu says pick "an elevation high enough.."...what is this elevation? 1ft 500 ft? 10,000 ft?

 

2. It appears that my follow up questions aboe apply to the tank as well. However the help menu also states that a piezpmetric tube ( 1 ft^2) may need to be included in the "storarge curve" definition starting at rood of the structure aup to the maximum elevation value specified to avoud numerical instability in the model. Any info you can shed on this variable setting. My tank is a 12 ft tall circular tank (constant area) above ground. So right now I have it model as a "functional" storage shape with a "constant area " of 443.53 and both the coefficient and exponent values set to 0.

 

By the way, my projection s otions have Hydrodynamic routing as the routing specification and the "enable overflow ponding at nodes" option is checked.

 

Thanks in adavance for your help!

 

Valued Mentor
fcernst
Posts: 1,088
Registered: ‎01-07-2011
Message 4 of 4 (208 Views)

Re: Bolted Manhole Rims and Closed Tank

12-28-2012 11:46 AM in reply to: CPeng78

Yes, of course the max (surcharged)water elevation, not just whatever you enter for the Max Surcharge property.

Fred Ernst, PE
C3D 2015
Ernst Engineering
www.ernstengineering.com

You are not logged in.

Log into access your profile, ask and answer questions, share ideas and more. Haven't signed up yet? Register

Announcements
Are you familiar with the Autodesk Expert Elites? The Expert Elite program is made up of customers that help other customers by sharing knowledge and exemplifying an engaging style of collaboration. To learn more, please visit our Expert Elite website.

Need installation help?

Start with some of our most frequented solutions to get help installing your software.

Ask the Community


Civil 3D Exchange Apps

Created by the community for the community, Autodesk Exchange Apps for AutoCAD Civil 3D helps you achieve greater speed, accuracy, and automation from concept to manufacturing.

Connect with Civil 3D

Twitter

Facebook

Blogs