Structural Identification: Opportunities and Challenges

Civil engineeringmaster builders havebeen constructingmasterpieces for millennia, long before the recent advent of systems engineering. However, since the 1950s, the planning, financing, design, construction, operation, and maintenance of civil engineered constructed systems, e.g., buildings, bridges, airports, plants, tunnels, dams, antenna towers, storage tanks, power transmission towers, highways, railroads, and pipelines, became the elements of highly complex, intertwined, and interdependent systems in dense urban areas. Such highly complex and multidomain systems, termed infrastructures, include government, education, healthcare, transportation, water, communication, and energy [U.S. Department of Homeland Security (DHS) 2010]. As urban populations grew, demands for infrastructure services increased. Meanwhile, the engineered elements of infrastructures aged and deteriorated, and their operational and structural capacity started to fall short of the demands. Their fragility was recognized as the failure of one infrastructure element that precipitated cascading consequential failures of additional elements from different infrastructures. Failures of critical infrastructure because of natural or manufactured hazards reiterate this connectivity. For example, on January 2, 1998, “a century-oldwatermain ruptured under lower FifthAvenue in New York City, creating a car-swallowing, curb-to-curb sinkhole andwatery chaos in a bustling neighborhoodwhose streets resembled Venice for a few hours. Then, as the rivers receded, a gas main broke and the crater spewed forth a tower of orange flames. No one was injured . but water damaged scores of lobbies, storefronts, and basements for blocks around, 40 residents were evacuated, hundreds of offices and businesses were closed, subways were halted, traffic was rerouted, and gas, water, electric, steam heat, and telephone services were disrupted for many” (McFadden 1998). Three infamous 21st century examples further demonstrate the unexpected cascading consequences of infrastructure failure: • In the case of the World Trade Center collapse on September 11, 2001, while airplane impact was a design consideration for the Towers, the consequential explosion and fire associated with an airplane impact were neglected in the design. Catastrophic and disproportionate collapse of the Towers because of fire in the upper floorswas completely unexpected. TheNIST investigation (NIST 2005) into the collapses led to new code provisions. • In the city of New Orleans on August 31, 2005, the storm surge because of Hurricane Katrina caused more than 50 breaches in drainage canal levees and navigational canal levees and precipitated the worst engineering disaster in the history of the United States. Such an event had been expected, but neither the consequences nor the preparation needed for effective emergency response were properly estimated (ASCE 2007). • An hour after the March 11, 2011 Tohoku earthquake off the coast of Japan, the tsunami wave breached the protective walls at the Fukushima Nuclear Power Plant and destroyed backup diesel power systems, leading to partial meltdowns at several reactors. The diesel generators were situated in a low spot on the assumption that the tsunami walls were high enough to protect against any likely tsunami. Subsequently, ancient stone markers indicating higher tsunami events were reported (Associated Press 2011).