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Re: Base Isolator Types

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I'm not completely sure I understand your first question but offer this 
information and hope that it helps.

The only general type of isolator I would add to your list would be 
friction isolators. In this type of isolation system the energy dissipation 
comes friction between two sliding surfaces. These devices typically 
consist of some sort of teflon load bearing pad or articulated knuckle 
sliding on a stainless steel surface. The sliding surface can either be 
flat (no restoring force) or concave (constant period). If the sliding 
surface is flat then some other component must provide the restoring force 
in the isolation system.

Your second type represents a wide variety of elastomeric isolators. These 
all consist of layers of elastomer bonded to steel shims. In one type of 
this family the elastomer is a high damping compound meaning that the 
rubber dissipates energy as it is deformed in shear. In another, the 
lead-rubber isolator, the energy dissipation comes from the plastic shear 
deformation of a cylindrical lead plug inserted at the isolator center.

Isolation is not generally considered as a solution for wind loads. In fact 
the isolation system must incorporate some means to resist wind loads 
without significant movement or the occupants of the structure will be 
rather unimpressed.


Mark Sinclair
Dynamic Isolation Systems, Inc.

>To: <seaoc(--nospam--at)>
>From: hns(--nospam--at) (Ross Johnson)
>Subject: Base Isolator Types
>What are the types of base isolators, that are commercially available or
>patented but not available for building structures?
>I request info from this listserv regarding the general description of the
>types you know of and their working performance, especially the advantages
>and disadvantages of each.
>I know of only two general types and no brand names--I call them:
>1.  Ball-and-socket type, using two concave bearing surfaces, rigidly 
>to the building foundation and column bases, in contact with a rolling 
>2.  Viscious bearing plate type, with alternating lead and steel plates, 
>alternating polymeric and steel plates.
>Are there more?  Are either of the two types mentioned suitable for wind 
>well as seismic loads?
>Your replies will be greatly appreciated.
>Ross Johnson
>Idaho National Engineering and Environmental Laboratory (INEEL)
>Ross E. Johnson, A.I.A. Architect  Id. #AR-1463
>(208) 526-2431   org: 4130
>E-mail address:	hns(--nospam--at)
>Facility Engineering Unit  FAX(208) 526-2681
>Mechanical, Civil, & Industrial Engineering Department
>Lockheed Martin Idaho Technologies Co. (LMITCO)
>Idaho National Engineering & Environmental Laboratory (INEEL)
>Idaho Falls, Idaho 83415-3650