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Unbonded post-tensioned tendon in duct

Inertia force

Unbonded post-tensioned tendon in duct

Inertia force

Wall

Foundation

Elevation

Energy dissipater absorbs energy as wall surfaces slide past each other

Wall

Foundation

Elevation

▲ 14.21 Damage avoidance precast concrete shear wall system.

Detail area

Column Mild steel bar

Unbonded post-tensloned tendon

Bar unbonded over this length

Elevation of central joint when frame drifts sideways due to seismic forces

▲ 14.22 Damage avoidance detailing in a precast concrete moment frame beam-column joint.

Unbonded post-tensloned tendon

Bar unbonded over this length

Elevation of central joint when frame drifts sideways due to seismic forces

Although in 1998 more than twenty buildings in Japan had active computer-controlled systems to reduce wind vibrations, only four systems continue to work during an earthquake. Akira Nishitani sums up the state-of-the-art in Japan:

... active control still has a long way to go to achieve the highest goal: to have reliable active control systems which could ensure structural safety even during strong earthquake. To do this, several problems have to be solved, eg. how to supply the external power which is needed or how to make systems with less reliance on external power, and how to increase the reliability and robustness of active control systems.8

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