×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Jobs

Tank design
2

Tank design

Tank design

(OP)
Hello,

I am new to this forum, so I am not sure how things work over here.


I have been working on a foundation for a tank ( 22' tall with a 12' diameter) but I am all stuck wiht the convective and impulsive components for the forces seismic design.

I am using the AWWA D100 standarts and also ASCE. ASCE doesn't have a lot equations to calculate all the varibles I need. AWWA has all the equations but its design method is complete different. Which standard should I use. Does anyone has a design guide that I can use?

I canvassed the internet but have not been very lucky with it.



Thanks.


Milene La Torre

RE: Tank design

I believe ASCE 7 sloshing requirements act as amendments to other codes like AWWA, API, ACI, etc. In other words, follow AWWA but substitute certain values as per ASCE 7. The tank chapter is kind of a mess and I've always struggled to sort it all out.

RE: Tank design

We usually request the calcs from the tank vendor, verify that their seismic design values are accurate, and use the reaction forces listed in their calcs.

At our firm, we always specify that the tank vendor shall provide calcs for approval prior to fabrication. In my experience, the vendors are in the best position to run the numbers because they have all the design criteria at their fingertips. Not to mention, software packages for designing tanks will automate the calcs and should provide more consitent results (in theory).

RE: Tank design

Follow primarily AWWA D100-11 (or API-650 as applicable).
Ss, S1, TL from the maps in ASCE 7, AWWA D100, or from ATC website.
Site Class from the soils report or assume Site Class D if not available.
Fa, Fv from tables in ASCE 7 or AWWA.
SMS, SM1 from Eq. 13-5 and 13-6 in AWWA (same as ASCE 7)
SDS, SD1 from Eq. 13-7 and 13-8 in AWWA (same as ASCE 7)
Ie, Ri, Rc from Table 24 and Table 28 in AWWA.
Tc from Eq. 13-22 in AWWA.
Take Sai as SDS per paragraph 13.2.9.2.
Ai and Ac from Eq. 13-17 and 13-18. In Eq. 13-18, that should be Rc, not Ri.
Wi and Wc from Eq. 13-24 through 13-27 in AWWA.
Xi and Xc from Eq. 13-28 though 13-30 in AWWA.
Ws, Xs, Wr, Ht from physical dimensions and weights of the tank.
Ms from Eq. 13-23.
wL from Eq. 13-37. The 1.28HDG will control for small tanks like yours.
Av from paragraph 13.5.4.3.
J from Eq. 13-36.
And that tells you if the tank is anchored or not. Unless subject to uncommonly high wind or seismic, a 22'x12' tank won't need anchor bolts.
And unless seismic loads are very high, seismic hoop stresses won't govern on a small tank and unless borderline on the J criteria, shell compression won't govern.
Check seismic freeboard required. For a slab-supported tank, there's an additional moment on tank bottom, calculated by using different values fro Xi and Xc.

Agreed with the poster above on ASCE 7 being a mess in the tank/vessel area, and that's been true through multiple revisions. Note that AWWA is service-level, not strength-level, so if you calculate moment per ASCE 7-10 or later, you also multiply by a 0.7 factor to compare to the AWWA values.

RE: Tank design

For a tank this small in diameter, impulsive forces predominate. I would not worry too much about the convective component.

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!


Resources

eBook – How to Choose the Correct Corrosion Testing Method
When designing a metal component, engineers have to consider how susceptible certain alloys are to corrosion in the final product’s operating environment. In a recent study by NACE (National Association of Corrosion Engineers), it was estimated that the direct and indirect costs of corrosion in the United States is approximately 6.2% of the GDP. In 2016, that cost exceeded $1 trillion dollars for the first time. 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