Column Lateral Force Anchorage for Seismic

[pioneer09]

Have a pre-engineered metal building that is located in a seismic design category C area. Per the adopted code, IBC 2015 and ACI 318-14, I am having a hard time distributing the horizontal loads from the seismic bracing. I was utilizing Hilti's Profis software and can not get a pier on its own to work when implementing the 2.5 Omega factor route for this project. My thought was to tie the pier back with hairpins to next adjacent column to count on developmental length and dead weight to resist these forces.

Are there other typical ways this is usually accomplished?

 

[jayrod12]

Is there not a gradebeam between piers? Normally we'd use those as the tension ties for the longitudinal bracing between piers. Assuming it all gets detailed appropriately of course.

For transverse load (thrust) there are many a building built with tension ties in the floor slab, or alternately dedicated tension ties below the floor slab. Or the foundations get designed to resist the thrust.

 

[pioneer09]

Transverse direction I am not worried about as I am designing these as stand alone pier/footings.

For the longitudinal loading, as my sketch showed and you eluded to, it seemed like a tension system back to the adjacent pier/columns was the route to go. Based on the loads I have with the Omega factor, I need (2) sets of hairpins/tie rods. This seems very difficult to achieve and to properly detail to allow the anchor bolts to distribute the load properly.

This got me thinking based on something we did on a different project. I have marked up the prior detail; see attached. This would allow larger bars sizes to be used and not require unique detailing or ties within the pier/wall. Steel plate would fully engage all anchor bolts and be directly tied to the adjacent pier. Are there any other alternatives or ways that have been done to achieve this?

 

[jayrod12]

I feel like doing those types of ties are a bit redundant if you've already got a gradebeam at the outside face of the pilaster. Certainly additional closed ties are cheaper than dedicated tension ties welded to a plate.

 

[pioneer09]

So if I am understanding this correct, you typically do a thickened slab/grade beam running parallel with the exterior foundation frost wall? What are you then using for the tie mechanism for the anchor bolts from the grade beam?

 

[jayrod12]

I would be using the exterior frost wall as the tie. and then reinforce the pilaster with ties. Similar to the attached.