anchor chair for the Flat bottom Tanks

[senthil83]

hi
i am designing a flat bottom tank as per AWWA spec, as per AWWA Spec we need to anchor chair as per AISI T192,

But We have designed the anchor chair as ordinary bracket plate and release with anchor chair height of
125mm

but as per code minimum 300mm height to be provided. calc as perr aisi T192 also shows 300mm required.

Instead of changing the Chair Height can i provide another two gusset in top of chair also to distribute force.

Regards

senthil kumar.B

 

[SAIL3]

sketch?

 

[SlideRuleEra]

This is a typical anchor chair for a flat bottom tank:

The height of the chair is to allow the anchor bolt to stretch over a calculated length without being overstressed as the nut is tightened. Here is a simple demonstration of the principle:

Take a rubber band that is 25 mm long and stretch it 25 mm... it may break.

Take a rubber band that is 50 mm long and stretch it 25 mm... no problem.

Since the calculations in the standard require a chair that is 300 mm high, do what it takes to meet the 300 mm requirement.

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[JStephen]

The height of the chair is to distribute stresses in the shell to an acceptable level. Anchor bolts are commonly installed with a base ring or base plate directly on or very near the bottom of the tank/vessel/column.

I've not seen the work behind the shell stress equation. I assume it is based on a rectangular load area, is approximate at that, and should be applicable to any attachment with a similar distribution of load.

 

[senthil83]

thanks for the reply