Washington, Aug 26 (Inditop.com) Understanding how powerful earthquakes knock down tall buildings in mere seconds can help engineers design damage-proof buildings.
But the nature of collapse is not well understood. It hasn’t been well-studied experimentally because testing full-scale buildings on shake tables is a massive, expensive and risky undertaking.
Accordingly, researchers from the University at Buffalo (U-B) and Kyoto University (Japan) teamed up to try a “hybrid” approach to testing that may provide a safer, far less expensive way to learn about how and why full-scale buildings collapse.
“One of the key issues in earthquake engineering is how much damage structures can sustain before collapsing so people can safely evacuate,” explains principal investigator Gilberto Mosqueda, U-B assistant professor of civil, structural and environmental engineering.
“We don’t really know the answer because testing buildings to collapse is so difficult. With this hybrid approach, it appears that we have a safe, economic way to test realistic buildings at large scales to collapse.”
The building in the original full scale test weighed more than 200 tonnes. That kind of weight puts shake tables under enormous stress, Mosqueda explains. It not only forces them to operate at full capacity, there is the additional potential for the heavy structure to crash down on the equipment.
“But in this case, we simulated the load with high-performance hydraulic actuators so the specimen overall was actually pretty light,” explains Mosqueda.
“We completely did away with the hazard of having tonnes of weight overhead that could come crashing down. Here, we just shut off the hydraulics and the load disappeared.”
It took the US and Japanese researchers, communicating over the net, about two hours to subject the hybrid model to the powerful ground motions that represented approximately the first five seconds of the 1995 Kobe quake, says an UB-release.
The hybrid test paves the way for additional experiments that will allow researchers to more precisely learn about the nature of structural collapse, says Mosqueda.
