Engineering news
Researchers are testing a six floor lightweight steel-frame building on the world’s largest outdoor seismic shake table to better understand how cold-formed steel structures withstand earthquakes and the fires that may follow.
The shake table, at the University of California (UC) San Diego, is the largest in the world and the structure the tallest cold-formed steel-frame structure to ever undergo such tests.
The building will undergo a series of increasingly intense earthquake simulations over three weeks. Motions recorded from actual 6.7, 7.2 and 8.8 -magnitude earthquakes in California and Chile will be recreated. The building will then be set on fire by researchers and drones will be used to fly in and around the building to map the structure and assess the damage.
Researchers have installed more than 250 sensors, over 40 video cameras, and a GPS system in the building. Some sensors are sensitive enough to detect movements caused by the wind.
Principal investigator for the project and structural engineering Professor Tara Hutchinson from UC San Diego said: “We are giving the building the equivalent of an ECG [electrocardiogram] to see how it performs after an earthquake and a post-earthquake fire.”
Engineers expect the building should perform well because it is lighter than a concrete building of the same height and as a result has less mass to generating damaging forces.
At the end of the testing, the building will be subjected to a simulated earthquake that is stronger than the structure was designed to withstand, in an effort to better understand how it might fail and to validate computer models of structural response that can be used to predict performance during different earthquakes.
Researchers will ignite pans of a liquid fuel called heptane throughout the building to raise the building’s temperature to 1000 degrees Celsius within seismically damaged rooms. Temperature probes and video cameras will then provide data to assess how damage from the simulated earthquakes affects the ability of the passive fire protection systems to contain fires and prevent the spread of smoke.
Falko Kuester, a structural engineering professor at the Jacobs School of Engineering at UC San Diego, will deploy unmanned aerial vehicles (UAVs) during both the seismic and fire testing to create a 3D model and video of observed damage. Data from the fire tests will allow the researchers to capture the thermal profile of the building.
The exercise aims to determine whether drones equipped with heat-detection cameras could be used to find survivors and assess damage after earthquakes and the fires that often follow them.
The largest building of this construction type tested before today on a shake table was a two-story residential structure in 2013.