Hold down bolt torque for foundation bolts

[paddy1385]

Hi,

I have been asked to provide hold down torque for foundation bolt of gr.8.8, HD galvanized. So I have below queries.
1. Presuming that its a tightening torque, do we need it for foundation bolt as we either use foundation pockets or an expansion bolt?
2. If yes, there are various standard torque values for zinc plated & lubricated bolts. Here bolt is both HD galvanized & Molykote G-Rapid Spray lubricated. Please advise on how to calculate the particular torque value for this?
3. How it will relate to the binding strength of concrete.

 

[CoryPad]

2. Perform your own testing to determine the correct values. A Skidmore-Wilhelm machine is a common one used for this purpose in the structural industry.

 

[Tmoose]

I'd expect the expansion anchor manufacturer has some recommendations , for a starting point.

Are the foundation loads dynamic, from rotating machinery etc?

 

[desertfox]

Hi paddy1385

Go to this site and see the link it gives maximum loads you can place on anchor bolts in concrete.

https://www.hilti.co.uk/medias/sys_...r_Technical_information_ASSET_DOC_2331133.pdf

So you can work backwards to obtain the maximum torque on the anchor before it starts to pull out from the concrete, however the frame your holding down also needs clamping so it doesn't move during service, so you need to calculate what holding down force you need for the frame, then check that the torque you put on the anchor to achieve this this holding down force is less than that quoted be the manufacturer.

 

[Illbay]

I need to do this kind of things frequently for unguyed vertical vessels or stacks bolting into the foundations.

I prefer to use DTI washers such as the "Squirter" washers provided by Applied Bolting:

http://www.appliedbolting.com/squirters.html

In particular, the "sandwich":

http://www.appliedbolting.com/dti-sandwiches.html