How safe would you feel, going back into a multi-story building that had just been through an earthquake? A new sensor system could allay your fears, as it optically measures how much a building has swayed, and thus how damaged it may be.
Some buildings already incorporate accelerometers on multiple floors, which are used to determine the extent to which those floors move from side-to-side. According to scientists at California’s Lawrence Berkeley National Laboratory, though, such systems can be costly, plus processing the data from them can be a complex and time-consuming process.
With that in mind, the Berkeley Lab researchers teamed up with colleagues from Lawrence Livermore National Laboratory and the University of Nevada-Reno, creating what is known as the Discrete Diode Position Sensor (DDPS).
In development for the past four years, it consists of a laser mounted on one floor, that shines a beam down onto a rectangular array of light-sensitive photodiodes on the floor below. As the building sways in an earthquake, the laser beam moves back and forth across the array, providing an electronic record of how much the two floors have moved laterally relative to one another.
Once the earthquake is over, centrally-located authorities can consult that wirelessly-transmitted record in order to instantly determine if the building exceeded its maximum structural tolerance. If it didn’t, then it can be safely reoccupied.
The DDPS has already been shown to provide accurate readings when subjected to shake table testing, and is now about to be installed in an actual multi-story building – on the Berkeley Lab campus – for the first time. Because the campus is situated adjacent to the highly-active Hayward Fault, the system should see a lot of action.
“Until now, there’s been no way to accurately and directly measure drift between building stories, which is a key parameter for assessing earthquake demand in a building,” says Berkeley geoscientist David McCallen, who is leading the research project. “We are excited that this sensor technology is now ready for field trials, at a time when post-earthquake response strategies have evolved to prioritize safe, continued building functionality and re-occupancy in addition to ‘life safety’.”