earthquake design

[jdbpe]

We are designing a three story 60,000 SF addition to an existing three story building of 200,000 SF. Code requirements dictate that the buildings be structurally independent so that only the addition need comply to seismic requirements for new buildings. The existing building and addition have basements 18 feet into the water table. The existing building has a mat to resist the water pressure below. The new building will also require a mat below for the same purpose.The mats need to be connected together with dowels, waterstops, waterproofing etc. to prevent water from entering the basement. Even though the upper floors will be separated by an expansion joint, are the buildings still independent with this condition in the basement?

 

[JAE]

I would think so. You need to make sure that the two buildings are separated (above the mats) far enough to avoid banging into one another.

 

[ERNESTOBARRERA]

You may need to make a computer model of both buildings and run a dynamic analysis to both to make sure that the buildings dont bang into one another...

 

[ishvaaag]

Obviously complete independence there's not since some restraint to ensure common position at the underground levels is enforced, I assume from use requirements; that would be an impossible, independenceand connection. However the only safe way to proceed would be to know what is the criteria by the reviewing party, who should not be bothersome if he is wanting to consider the surely reasonable requirements of designed use. Upon minor technical criteria some advice could be given, but I don't think so on such basic thing, more related to the policy of buildings than anything technical. To make this clear you and anyone could do the building "independent" by putting some distance between them...but it is this what the owner wants and asks and is (assumed) permitted? One must not say at the same time permitted and forbidden.