![]() ![]() But engineers designed the buildings to stay in one piece if they slide down the hill in an earthquake, so the occupants would survive.īell said utilities recovered rapidly in Anchorage thanks to engineers studying soils. Some tests can be done on site, but Brennan’s team also brings core samples into the lab to determine its detailed physical properties.Ĭalculations based on those measurements determine the stability of a site and inform structural engineers how strong a building must be.īob Bell, retired from his own Bell and Associates engineering firm, said some buildings along bluffs downtown were constructed on soil known to liquefy when shaken. Geotechnical engineers do study sites of all commercial buildings. Brennan said geotechnical investigation is not required for single-family houses in Anchorage except in areas designated as having high risk of ground failure. Those houses that were damaged may have been unlucky with the soils underneath. Within the building safety area, few buildings sustained catastrophic damage. Shear walls must be specifically located and oriented and securely attached to the foundation with stout bolts. The need isn’t obvious unless you understand the physics. In Anchorage, prone to high winds and earthquakes, even modest homes need shear walls to stiffen against those forces. Inspectors then verify that work is done as shown in the plans. Anchorage plan reviewers check calculations on every house or commercial building to make sure the design accounts for lateral shaking forces, among other issues. “We’ve heard anecdotal evidence for years that the construction that was taking place outside the Building Safety Service Area was less than structurally code compliant,” Noffsinger said. ![]() ![]() Eagle River never opted into the Building Safety Service Area, where Noffsinger’s office has authority. Under Anchorage’s odd form of local government, areas can choose a menu of services. (It’s also possible more severe shaking was a cause.) I’ve also heard of damage in Mat-Su, which doesn’t have residential building codes. I doubt it is a coincidence that more housing damage occurred in Eagle River, where building codes are not enforced, than in the Anchorage Bowl. In other cases, however, construction probably should have been better, especially in damaged homes. Engineered facilities that failed may have been built to fail in a quake this strong. Construction that can withstand a strong earthquake may be too expensive for low-hazard infrastructure like roads, which are relatively easy to fix. In areas where roads cross wetlands, failure can occur when shaking liquefies soils underneath, said Kyle Brennan, who leads geotechnical engineers for Shannon & Wilson in Anchorage and is vice chair of the city’s Geotechnical Advisory Commission.īut that doesn’t necessarily mean anyone made a mistake. “Some of them, we can just look at the picture in the paper and say, ‘Yep, that’s why that failed,’” said Ross Noffsinger, the acting municipal building official - a job that puts him in charge of enforcing the building code. (Matt Tunseth / ADN)Įngineers can tell why certain roads and buildings collapsed in Friday’s earthquake without even going to visit. Logan Cushman was inside when the home collapsed, but was able to escape unharmed. This home on Dome Circle in Eagle River partially collapsed in Friday's earthquake. Updated: DecemPublished: December 4, 2018 ![]()
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