Storage Container Conceptual Issue - uplift

[Materofact]

Building depts require steel storage containers be held down to the ground. We can make overturning and sliding work with just the weight of the unit itself. However, the vertical seismic that is reuqired (the ASCE v=0.2SDS x W) is where things get silly.
Lets just say that 600 pounds per corner is need of uplift anchorage (2400 lbs total uplift required).

Conceptually, if you have 4 blocks of concrete weighing 600lb each available(or whatever dead load reduction you are comfortable with) at each corner that you can anchor to... is the idea that the storage container itself gets thrust upwards in seismic, but the silly blobs of concrete are somehow immune to that same seismic upthrust equation (.2sdsW) and will hold the container down to the ground? they certainly dont have that much friction on the side walls to resist that upwards movement. It would seem that using isolated shallow concrete footings for uplift resistance is lacking common sense. What am I missing here? I suppose we do the same thing with large uplifts for structures and uplift anchors into the required concrete weight, but it just makes more sense in that instance, and there are usually more robust connected footing systems.

We usually spec out mobile home anchors which makes much more sense from a anchoring to the ground perspective, but occassionally we see square concrete footings installed (not a slab) already,which begs hooking up to them to comply with what seems to be a silly requirement in general.

So, to pour concrete weighing as much as needed for uplift? Or always use earth augers like mobile homes? Either one "works" according to code?

 

[HTURKAK]

My points;

- You did not mention the SDC . When you look clause 12.4.2.2 Vertical Seismic Load Effect;
(..2. The vertical seismic load effect, Ev, is permitted to be taken
as zero for either of the following conditions:
a. In Eqs. (12.4-1), (12.4-2), (12.4-5), and (12.4-6) for
structures assigned to Seismic Design Category B.)

- If you feel comfortable, you may choose the concrete weighing as much as needed for uplift. However, the container will not fly or topple with concrete weighs less than for uplift but may start rocking .


My opinion...







If you put garbage in a computer nothing comes out but garbage. But this garbage, having passed through a very expensive machine, is somehow ennobled and none dare criticize it. ( ANONYMOUS )

 

[Materofact]

Coastal California, Seismic Zone D / E weight of the unit alone can be determined to counter the lateral loads for wind and seismic. but the isolated uplift load presents a problem. rather silly IMO. are we supposed to apply .2sds to an entire house and pretend in actuality that if there was a vertical thrust upward that the foundation doesnt also get thrown up into the air>? perhaps its a requirement so there can never be any separation of the foundation from the sturcture so it remains "in tact" but with a metal storage containier, there needs be NO foundation(just gravel pack), so the tie down requirement is N/A.