By Alka Tripathy-Lang, Ph.D. (@DrAlkaTrip)
The Mw 7.1 earthquake on July 5, 2019, was the largest quake California has seen in 20 years. Part of the so-called Ridgecrest earthquake sequence, the Mw 7.1 event served as a reminder of the seismic hazard associated with living on the West Coast of the United States. Although these tremors struck a relatively sparsely populated region, significant damage was sustained, with the estimated economic impact in excess of $100 million. Determining the extent of damage to individual buildings is an arduous and time-consuming task. Now, engineers are testing a state-of-the-art laser-based system that could dramatically speed up post-earthquake damage assessments by accurately measuring displacement between floors of multistory buildings.
Is the building safe?
In the chaos immediately following a large, damaging earthquake, structural engineers have a massive workload in assessing the safety of affected buildings, especially critical infrastructure like hospitals and water treatment plants, and large buildings like multistory apartment or office buildings. “The post-event environment is overwhelming and confusing, and people need to know right away if they can go back to work or go home,” says Floriana Petrone, an assistant professor of structural engineering at the University of Nevada, Reno (UNR), visiting faculty scientist at the U.S. Department of Energy Lawrence Berkeley National Laboratory (LBNL), and lead author of a paper published in Engineering Structures that presents results from tests of the new laser-based system.
Structural engineers typically spend a day or two evaluating buildings that are under contract, says Ronald Hamburger, a senior principal at Simpson, Gumpertz & Heger, a company that designs, investigates and rehabilitates buildings and structures. Then the engineers respond to calls from other building owners wanting to determine if their buildings are safe for reentry immediately or if they need repairs first, in which case, the engineers develop repair plans. In a few cases, Hamburger says, the damage is obvious. But many buildings conceal their wounds within the walls, he says. This is particularly problematic for certain steel-framed buildings, where the only method to assess damage extent is to manually remove asbestos-based fireproofing. This potentially dangerous damage assessment process can take days to weeks.
Petrone and her UNR/LBNL colleague David McCallen, who first envisioned the technology, think their system could dramatically speed up post-event evaluation of building safety — allowing such evaluations to be completed in minutes instead of days.
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