Determination of the Ultimate Capacity of Elastomeric Bearings Under Axial Loading.
Determination of the Ultimate Capacity of Elastomeric
Bearings Under Axial Loading.
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
building technology; compression testing; earthquake
engineering; elastomeric bearings; seismic base
isolation; ultimate load tests; nonlinear finite
elements; Valanis-Landel Function; rubber modeling
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.