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RE: Underground Structures

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Title: RE: Underground Structures

Vinod:

About 20 years ago, while still a mere youth, I wrote the seismic design criteria for Northwest Energy's proposed Trans Alaskan Gas Pipeline Project.  This project, which ultimately was cancelled, involved a very long, large-diameter buried gas pipeline with a construction cost of about $14 Billion.  Because the mass or the surrounding soil far exceeded the mass of the gas pipeline, the seismic design was not driven by acceleration.  Relative displacement controlled the design. 

I suspect that you will also find that your buried structure is not inertially driven, and cannot be seismically designed on the basis of acceleration.  Depending on the specific characteristics of your structure, either velocity or relative displacement will govern the seismic design.  As noted by others, a lot of material has been published on this subject in recent years.

Good luck with your project!

Stan Caldwell in Dallas
   
-----Original Message-----
From: Vinod Sahni <SAHNIVK(--nospam--at)nv.doe.gov>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Monday, August 07, 2000 10:08 AM
Subject: Underground Structures


>Harold Sprague and James Lutz :
>Thanks for your response which was very helpful.
>Regarding the question as to the nature of structure.......following is a
>brief description for information.
>It involves a hemisphere dome 100' diameter on top of concrete walls
>which are 50' high.  The top of the dome is located about 40' below
>ground. Tthe dome is surrounded by a covered concentric gallery about
>60' width.  Roof of gallery is about 125' below ground.  24 - 20' diameter
>semicircular tunnels coming towards the dome meet and stop at  the
>gallery in radial fashion.  All construction will be concrete. Other than
>tunnels which will be drilled,  it will be open excavation construction.
>For the conceptual design, I came up with 3' thick concrete with lots of
>reinforcement for the hoop stress.  Walls are 3' thick. The gallery has
>closely spaced 4'x4' columns with girders and beams (48"x60" or less)
>and a 12" roof slab. The tunnels will be precast other than the bulkhead
>entrance wall. 
>By the way the seismic zone is more like 2B and not 4 as I had given
>before.
>
>Thanks again for the response you gave.
>
>Vinod Sahni, SE