NIST Time|NIST Home|About NIST|Contact NIST

HomeAll Years:AuthorKeywordTitle2005-2010:AuthorKeywordTitle

Determination of the Ultimate Capacity of Elastomeric Bearings Under Axial Loading.


pdf icon Determination of the Ultimate Capacity of Elastomeric Bearings Under Axial Loading. (11042 K)
Bradley, G. L.; Chang, P. C.; Taylor, A. W.

NISTIR 6121; 150 p. February 1998.

Available from:

National Technical Information Service
Order number: PB98-133531

Keywords:

building technology; compression testing; earthquake engineering; elastomeric bearings; seismic base isolation; ultimate load tests; nonlinear finite elements; Valanis-Landel Function; rubber modeling

Abstract:

Elastomeric bearings are used as base isolation systems in order to reduce the response of buildings to earthquake ground motions. In order to facilitate the use of this technology, the National Institute of Standards and Technology (NIST) has published guidelines for testing base isolation systems. NIST seeks to improve the current guidelines for determining the capacity of bearings under axial loading. Very few full-scale bearings have been tested to failure because the capacity of a typical bearing is often beyond the loading capacity of existing testing facilities. This research has sought to determine if tests to failure under axial loading on scale models can be used to predict the axial failure load of a full-scale bearings. However, there were dissimilarities in steel shim thickness, cover layer, and the central alignment hole. The stress-strain responses were similar, but not identical. Nonlinear finite element analysis conclusively demonstrates that similarity in shim and rubber thickness is most important. The dissimilarities in the cover layer and central alignment holes, separately considered, had less effect on the bearing response than shim thickness dissimilarities, and offset each other in this particular case. Tests indicate that the mechanical properties of the 22-gage shims (0.762 mm thick) for the 1/4-scale bearing may be slightly modified, possibly due to sandblasting and/or the cold rolling processing of the steel.