Case Studies

1994 Los Angeles earthquake –
University of Southern California Teaching Hospital

Univiversirsirsity of Southern Calialialiforniaia Teachiachiachiaching Hospitalal

The Lead Rubber Bearing (LRB) is world famous for successfully protecting this hospital from damage when ten nearby hospitals were so badly damaged that they had to be evacuated. Here are the interesting details:

  • This 7 storey hospital underwent ground accelerations of 0.49g, while the roof-top acceleration was only 0.21g
    – a reduction factor of 1.8
  • The Olive View Hospital, nearer to the epicenter of the earthquake underwent a top floor acceleration of 2.31g compared with base acceleration of 0.82g – a magnification factor of 2.8.
  • A comparison shows a net advantage factor of 1.8 x 2.8 ~ 5 in favour of the LRB-isolated hospital.

1995 Kobe (Japan) earthquake –
Ministry of Post and Telecommunications computer centre

Kobe (Japan)

Further support for the LRB isolation system came in the Great Hanshin earthquake:

  • The building survived with no damage or disruption to services
  • Maximum ground acceleration of 0.40g with the maximum sixth floor acceleration of 0.13g
  • LRB brought an attenuation factor of 3

New Seismic ISOlated Airport Hangar, Istanbul – October 2009

 

Airport Hangar, Istanbul

Earthquake Engineering NZ members Beca International Consultants Ltd (Beca) and Robinson Seismic Ltd have provided design and seismic bearings for the seismic isolation of the roof of the new aircraft hangar recently opened at Sabiha Gökçen Airport in Istanbul.

The seismic isolation solution to provide earthquake mitigation for a major airport hangar is a world first. Robinson Seismic Ltd were approached by their Turkish agent Em-Ke Construction Ltd (Istanbul) to provide a solution for the seismic isolation of the roof of this new hangar, and in turn brought in Beca for their specialist structural engineering and seismic isolation expertise.

Beca’s Dr David Whittaker joined Em-Ke’s Mehmet Özcanli at the opening ceremony. Typically, structures are isolated at their base (hence base isolation). However, due to the size and complexity of the structure under the hangar floor, that approach did not offer the best solution.

 

Robinson Seismic Ltd and Beca proposed the use of lead rubber bearings installed between the walls and roof of the hangar. The seismic isolation roof design solution saved US$250,000 in costs as well as providing high earthquake resistance.

The roof is 110 metres x 140 metres and weighs 2,000 tonnes. In total, thirty bearings were used, ten Lead Rubber Bearings for the reinforced concrete central points and twenty (ten each side) Rubber Bearings for the steel outer columns. Design displacement of the bearings is 300mm.

The joints of the spans are also movable in a horizontal direction. Design of the isolation system for the hangar roof also had to take into account thermal expansion of approximately 50mm and overall wind uplift of up to 1,500 tonnes. The following photos show views from the inside of the hangar showing the bearings on top of the columns and from the outside showing the size of the building.