In 2011, the Center for Civil Engineering Earthquake Research (CCEER) at the University of Reno in Nevada began a project sponsored the California DOT. Because precast concrete decks and columns are integral to accelerated bridge construction (ABC), Caltrans wanted to see what happens to the connection between these elements and the rest of the bridge when the entire structure is subjected to a 7.5-magnitude earthquake. (Caltrans suffered through just such an event in 1994 with the Northridge earthquake in Los Angeles, which killed more than 60 people and caused $13 billion to $44 billion in damage.)
The study -- Seismic Performance of Next Generation Bridge Components for Accelerated Bridge Construction -- tested the connection between five half-scale model precast columns and footings using Caltrans seismic design criteria (SDC). You can get more details and download the test matrix for each model here.
Late last month, the center announced all connections performed as expected: four designed to be undamaged weren't damaged and the two designed to absorb the force of an earthquake by breaking did so. (Don't ask me where and how the sixth model connection came from.) The tests were conducted on a 70-ton, two-span, 70-foot-long bridge perched on hydraulically driven tables that were programmed to mimic an earthquake.
"I was very pleased with what we learned," said M. Saiid Saiidi, the project's principal investigator, a University of Reno civil and environmental engineering professor and director of the Center for Advanced Technology in Bridges and Infrastructure in a university article. "Not only do we have a better understanding of how the connections work together, but we have the data now to see how they react under extreme, off-the-charts conditions meaning we can prepare for more than what is expected."