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Unbonded
brace frames at work in Osaka |
The Osaka
International Convention Centre in Nakanoshima, Osaka, Japan,
opened to the public in March 2000. Osaka is in a region of high
seismicity and the safety of the structure in strong earthquakes
was a key design requirement.
In Japan, the seismic performance of tall buildings has to be
demonstrated explicitly using non-linear time history seismic
response analysis. Arup Advanced Technology Group developed the
seismic concept and performed the analytical justification for
this project.
Unbonded brace frames
The design incorporates the newly developed ‘Unbonded Brace’
components to absorb seismic energy by plastic deformation. Each
brace comprises a core of low-yield steel plate, debonded from a
concrete ‘jacket’ cast around it in a steel tube. The two ends
of the steel core are connected to the structure as for a
conventional brace. The concrete filled tube is not connected to
the rest of the structure but provides lateral restraint to
prevent the brace core from buckling. This results in an element
that yields and absorbs energy equally well in tension and
compression. The incorporation of these elements enabled this
unusual building to achieve a high degree of seismic tolerance
with reasonable overall steel weight. |
