Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


What appropriate load combination for tank leak test

What appropriate load combination for tank leak test

What appropriate load combination for tank leak test

Hi guys, i was designing a wastewater RC tank on ground. I am taking 1.4(D+F) for operation case, F as fluid load. My design basis calls for American Codes (ASCE. ACI350) and such operation load case is clearly defined. But i could not find in the codes on how to deal with leak test load combinations. Am i going to take such fluid as live load 1.2D + 1.6 Water Test? Some of my colleagues are suggesting to take alternative load comb 1.4D + 1.7Test, which i felt is too much for the situation. I'll be thankful for any help to enlighten me.

RE: What appropriate load combination for tank leak test

Since I design a lot of repairs on wastewater treatment tanks, by all means use the 1.4F and try to optimize the test case. We can always use the business.
Or you can do what we do and use 2.21 times the fluid loads for bending and 1.7 for shear to whatever you have as a passive overflow, like the tops of walls.

RE: What appropriate load combination for tank leak test

Thanks Jed. But could you guide me where how to get 2.21 for bending? is this about durability factor? Sorry im not good with tank design.

Also, as with this Sd, i read from ACI350 that Sd could be ignored when load combination is with seismic. I was thinking maybe the reason was that seismic load is only short term. If my intuition is correct, then i could also ignore Sd for wind and for test load, since they are not long term forces. I may be wrong, would be thankful to be enlightened

RE: What appropriate load combination for tank leak test

First of all, ACI 318 is wrong. Fluid loads, while potentially well defined, should have a much higher load factor than dead loads. ACI 350, some edition, somewhere, says to use a 1.7 factor and add a 1.3 factor to that for "durability" for bending. Shear requires a 1.7 factor, unless you need shear reinforcing, than you use the 2.21.
You're right, SD can be ignored when combined with seismic. But seismic is likely to not control vs. the overflow level on the vessel.
One last piece of advice; these tanks, full of wastewater or water, are not to be trifled with. I can't mentor you, but someone should be watching.

RE: What appropriate load combination for tank leak test

Thanks a lot for this guidance Jed

RE: What appropriate load combination for tank leak test

I think I'm following your logic, but please check me: Since these are test cases (not long-term operations), do you ignore seismic added stresses for the four-five hours of the static test for waste tanks? (I'm more familiar with the pipe and ASME type hydro tests, op tests.)

RE: What appropriate load combination for tank leak test

Leak tests last a lot longer than four to five hours, but the principle is basically what you stated. Based on the risk of a seismic event occurring during the leak test, it can be reasonably ignored.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


eBook - 10 Reasons to Choose CATIA on the Cloud
To compete in today’s fast-paced and competitive market, smaller and newer firms need a powerful platform that will enable them to compete with bigger players, without the heavy investments needed in computer hardware, software and personnel. Download Now
White Paper - Smart Manufacturing for Electronics
This white paper describes a transformative approach to electronics manufacturing made possible by the addition of Mentor Graphics to the Siemens family. It describes a completely digitalized strategy that supports both printed circuit board (PCB) and mechanical design and manufacturing, uniting the entire product lifecycle – from idea and production to customers and back. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close