Equipment Anchorage - Seismic

[LSPSCAT]

When calculating anchorage forces for mechanical equipment, is the total design lateral seismic force, Fp, the actual numerical value to be used to determine the anchorage forces?

No other inclusion of Fp into load cases needs to be included. Now this is an ultimate load; so using LRFD provisions we could consider this a factored load? What about ASD provisions?

 

[JAE]

The Fp represents the "E" in the required load combinations. Use this in each combination along with other applicable loads such as Dead Load, Live Load, etc.

It also is an ultimate load so if you are using ASD procedures you would use ASD load combinations which have a 0.7 factor on E to bring it down to unfactored status.

 

[LSPSCAT]

I am basically just looking at the tension forces from the overturning moment and the horizontal shear forces in the anchorage.

In this case I do not have any additional live loads or dead loads other than the equipment weight. I would also use 0.6D in determing the resisting moment from the self weight of the equipment.

Simliarly if working with the ultimate load Fp the resisting moment would be based on a factored dead load (1.2)

 

[JAE]

Sounds like you got it.

 

[wannabeSE]

If you are anchoring the equipment to masonry or concrete, look at ASCE 7-05 section 13.4.2. You may need to multiply the seismic force by 1.3. Also, if the anchors are not prequalified for seismic, you may need to reduce Rp to 1.5.