Shake-up in San Diego

Monday 23 Apr 2012

University of California tests seismic activity on purpose-built $5 million hospital

Last week, a team of engineers, scientists and earthquake safety experts began a year-long testing and analysis programme in San Diego to examine the internal and external affects of a series of quakes on a hospital building. Using a $5m dedicated facility at the University of California’s Englekirk Structural Engineering Center in San Diego, the team will shake the volume under various conditions to simulate past earthquakes around the world, examining how the building responds to changing variables.

This experiment differs from the majority of earthquake tests as it will look at how the quakes affect the interior space as well as the exterior. The building has been designed as a high-tech hospital facility, complete with computer servers, electrical equipment and wiring, functional sprinklers, heating and air conditioning systems, large and small laboratory equipment, modern ceiling systems and a surgery suite and intensive care unit at the top. The experts will be testing the effects of a range of earthquake intensities on all of these elements as well as working elevator systems and stairwells.

Throughout the five-storey, purpose-built facility are over 70 cameras and 500 high-fidelity sensors to record the movements of the entire volume and of smaller elements within the building. 230 of these sensors will measure how fast the building moves, 160 will decipher the relative displacement between two points and 50 strain gauges measure the deformation of the rebar that are buried in the building’s concrete foundations. The 80ft tall building is constructed from heavy precast concrete cladding and synthetic stucco which is regularly used in structures of this nature.

During the last week the building was rocked on four base isolators which meant that the mid-rise tower swung in the air ‘as if it were on a skateboard’ but that the exterior remained intact and the interiors largely unaffected. Professor Tara Hutchinson of the Jacobs School of Engineering at UC San Diego explained: “[The] test was really a success in the sense that the base isolators below the building protected the non-structural components from the damaging effects of ground motion. Had this building been occupied, it would remain operational after these earthquakes. We did observe some minor damage on the interior, in particular things that are quite sensitive or brittle elements, such a partition walls, in the form of cracking mud and tape…but these are cosmetic, easily and economically repairable.”

This week the base isolators will be removed and the shaking motions repeated in order to test the difference that these complex engineering elements can make. The onsite experts are expecting a drastic difference between the two test results. In May, fires will be lit to ascertain how a building damaged during a strong earthquake is affected by fire and how smoke moves through the volume. These are vital stages of the test process as fires often spark in urban developments post-quake.

The robust nature of public facilities such as hospitals and schools can be vital in the amount of time it takes for an earthquake-hit community to get back on its feet. In 1971, a 6.6Rs quake struck San Fernando taking out the Veterans Affairs Hospital and killing many of its patients whilst the newly opened Olive View Hospital partially collapsed. The state of California rewrote its building codes in 1976 and it is tests such as those currently being undertaken in San Diego that will help experts update these existing parameters. The scientists, engineers and quake experts involved will publish their findings from the government, National Science Foundation and industry agency-funded experiment within the next year.

Sian Disson
News Editor

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