State of the Art - Hold down bolt, chair design

[bertfourie]

Several studies have shown that the standard chair design creates a stress concentration, which may lead to tank failure in an earthquake situation. I was wondering what the latest design evolution look like? What is current best practice?

 

[MJCronin]

There is no single "standard chair design" ..... Can you refer to a published national standard ?

Are you talking about tank anchor bolts ? if so say so....

Please give examples of these "Several studies" .... Are they on the internet ?

Are you asking about the best seismic practices for flat-bottomed tank design ?...... I can't tell

MJCronin
Sr. Process Engineer

 

[JStephen]

I would say the "standard chair design" is that in the AISI book:

https://www.scribd.com/doc/255157098/AISI-Anchor-Chair-Design

"the standard chair design creates a stress concentration, which may lead to tank failure in an earthquake situation"- the chair evaluation mentioned above checks stresses in the shell at that point. If it's considerably in error, that's an issue, otherwise, the stress concentration is what you're checking. And I would think stress concentration is somewhat unavoidable. Note that current tank standards call for an increased load for seismic evaluation, not sure if that's the solution to the issue mentioned or what.

Anyway, short answer, no, I haven't seen any new or improved configurations or analysis. You could of course do finite element analysis if the situation warranted it.

 

[MJCronin]

There is a document published by FEMA defining earthquake anchorage methods for mechanical equipment.

https://www.fema.gov/media-library-data/20130726-1455-20490-6434/fema412.pdf

http://weldedsteeltanks.com/index-1.html

This document is a comparative evaluation of various types of anchorage.

https://ascelibrary.org/doi/full/10.1061/(ASCE)CF.1943-5509.0000628

The "Aboveground Storage Tank Handbook" contains a chapter on seismic design of tanks.

https://www.researchgate.net/public..._for_Seismic_Analysis_of_Liquid-Storage_Tanks

MJCronin
Sr. Process Engineer