Jul 3rd 2018

Civil Engineers Build Resilience Into Disaster Mitigation Efforts

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Have you ever looked at a tall bridge or high rise building and thought, “I’d hate to be up there in an earthquake?” It turns out you might actually be safer on one of those structures than in your own home, thanks to new and evolving civil engineering technology focused on disaster mitigation.

Civil engineers focus on the design, construction, operation and maintenance of infrastructure projects such as roads, bridges and water delivery systems. Increasingly, they include disaster mitigation technologies in every project. Why? Because the less an earthquake, flood or fire affects a facility’s safe operation, the sooner emergency management officials can get it back in service.

Be Flexible, Enjoy the Ride

The U.S. government has invested heavily in networks designed to monitor indicators of potential natural disasters. Yet, it remains nearly impossible to know when the next disaster will strike, how strong it will be or how long it will last. As a result, civil engineers design structures to work “with” rather than “against” the forces of Mother Nature.

Building designers in California, for example, use shear walls and metal joint reinforcement brackets to make structures more resilient to earthquakes. “If you make a building an elastic, well-connected box, its major structural elements will move together,” explained John Schuricht, a structural engineer with Palos Verdes Engineering Corporation in Los Angeles. Without reinforcement, the building’s main elements will move in random ways during an earthquake, potentially pulling the structure apart.

The new San Francisco-Oakland Bay Bridge, opened in 2013, is a model of civil engineering technology that adapts to reality. Its self-anchored suspension bridge features a main tower, road deck and suspension cable that can bend and sway during an earthquake. The bridge also uses an innovative technology called hinge pipe beams — picture giant metal dowels and matching sleeves — installed under the road deck at junctions between its major sections. The beams allow road sections to slide back and forth as much as six feet without damaging the bridge.

Photo Source: Caltrans
(Caltrans)

The bridge’s adaptive technology proved itself on August 24, 2014, when the South Napa earthquake — a magnitude 6.0 temblor and the biggest earthquake to hit the Bay Area in 25 years — left the bridge unscathed.

Bend, Don’t Break

Disaster mitigation strategies also drive civil engineering technology used in public water storage and delivery systems.

“We pay particular attention to the seismic resiliency of our emergency water tanks” said Todd Peters, chief engineer for the California Water Service Company, San Jose, Calif. All piping attached to the tanks is flexible, he explained, and the tanks are anchored seismically. “We also include ‘head space’ in each tank to allow water to slosh around during an earthquake, which reduces stress on the tank’s structure,” Peters added.

The company has begun using pipes with flexible, earthquake-resistant joints to avoid breakage in areas with high seismic activity.

Learn From Nature’s Laboratory

For civil engineers, every natural disaster provides an opportunity to test and improve their disaster mitigation strategies.

California’s Department of Transportation (Caltrans), which manages and maintains the state’s highway system, has learned expensive lessons from each of the region’s last major quakes. The Sylmar earthquake in 1971, for example, demonstrated the need to reinforce the tops and bottoms of the concrete columns that support the state’s more than 12,000 bridges and overpasses. Freeways that collapsed during the 1994 Northridge earthquake taught Caltrans that all of the columns supporting a bridge should be approximately the same stiffness.

Freeway bridges that collapsed during the 1994 Northridge earthquake taught Caltrans that every column supporting a bridge had to have the same stiffness
(WikimediaCommons/U.S. Geological Survey)

“Today we’re building bridges with civil engineering technology that dissipates seismic energy at the ends of columns,” said Mark Mahan, chief of Caltrans’ Office of Earthquake Engineering, Analysis, & Research. “Either we form and pour the columns on site, adding reinforcing steel hoops at the ends of each column, or we build the bridge using precast concrete components integrated with reinforcing steel,” he said.

Drive Recovery With Data

Even if you’ve designed your bridge or water delivery system to survive the big one, you’d still like to verify its actual condition once the shaking stops. Caltrans’ new ShakeCast system can help.

Developed in collaboration with the U.S. Geological Survey (USGS), ShakeCast is a web-based application. Within minutes of detection of an earthquake by USGS sensors, it sends out estimates of earthquake shaking, by location, to Caltrans and other state, federal and local agencies. ShakeCast can’t tell you the condition of specific structures, but it can guide the deployment of structural inspection teams to areas most likely affected by an earthquake.

Civil engineers will never defeat natural disasters, but if they can force a draw through deployment of smart, adaptive technologies, everybody wins.

Northrop Grumman has engineers in many disciplines – including civil – who work on environmental projects as well as cyber, aerospace and other areas. Find out more about our engineering careers.

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