Storm Shelter in Host Building 1

[WesternJeb]

Our firm is designing an ICC 500 storm shelter (250 mph zone) in the basement of a two story building. The shelter takes up roughly 60% of the building footprint (~100'x100'). Due to the large footprint and lack of floor space from the architect, our plan currently is to anchor in purely gravity columns to the top of the storm shelter for the floor and roof above the top of our shelter. The columns would ideally be above our shelter walls, and use some very shallow embed. anchors that would "rip out" in a major wind event.

We are in a high seismic region as well, so we have to detail the base of the gravity columns to withstand the loads imposed from seismic drift and not fail, but be able to rip out during a tornado. Does this seem possible?

Does anyone see an issue with putting gravity columns on the roof of a storm shelter and designing them to rip out during a major wind event? We are also designing for host building collapse using an energy dissipation theory from chapter 2 of Blodgett's Design of Welded Structures, because I feel like someone is going to mention it.

 

[WesternJeb]

That could work, and just make the projection length/strength long enough to facilitate any incidental rocking from seismic drift.

 

[WesternJeb]

After looking into the nut removal option, that is a no go. Some of these columns have 60 kips on the, so more than likely they wouldn't "pick up" in a tornado, but rather fall over and want to bring the anchor with it.

 

[bones206]

Can you describe the shelter structure in a little more detail? Are the columns above aligning with columns within the shelter, or is the shelter acting like a podium with transfer members? Just trying to picture how this is all coming together. Sounds like an interesting and challenging project for sure.

 

[WesternJeb]

It is very interesting and challenging; we are also being rushed to provide an early foundation package for the building.

Our storm shelter takes up 60% of the base floor plan. The plan is CMU bearing walls with composite steel deck on top for the shelter itself.

The primary building is a steel framed building utilizing special moment frames with special cmu shear walls. We have columns framing out the perimeter of the building (moment frames) with gravity columns scattered throughout the building interior. Some of these columns have to go on top of the storm shelter, since it is such a large footprint. We are trying to locate the columns along the CMU walls of the shelter below so that we can provide a masonry or concrete column / pier in the shelter wall to carry the gravity load down to the foundation.

We are comfortable with all of this, except for ensuring the said gravity columns remain safe after a seismic event, but do not cause our storm shelter to fail due to the anchorage.

 

[DanKile]

Would there be enough room to add support beams above the shelter? Adding bearing pads to keep the beam depth in check.

 

[WesternJeb]

DanKile, This would solve a lot of our issues but unfortunately there is not.

 

[bones206]

Since you have vertical members below the superstructure columns, you should be able to embed the anchors as deep as you need to lap/develop the anchor reinforcement. So I think you're in good shape as far as that goes.

One other reason I like the ductile approach over the break-away approach, is in case people didn't have time to get to the shelter before something hit, it might make the difference in buying a little more time before collapse.