A new national web of research labs for studying materials and assemblies under complex seismic loading is beginning to revolutionize earthquake engineering research and deliver on sophisticated promises. The George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES), launched in late 2004, coordinates and administers National Science Foundation research grants. It has 15 “equipment sites” at universities around the country and a supercomputer center and management center at the University of California at San Diego. The “network” comes into play with NEES’s next-generation Internet data links that tie the labs’ monitoring systems together. That link lets researchers grab live data of tests in simulated earthquakes at any one lab and share the “quake” in real time with others. The network can turn the scattered facilities into one big super-laboratory capable of modeling complex interactions.
Some large-scale testing tools at the equipment sites are designed to mechanically simulate the forces of quakes and analyze the response of sensor-studded test objects. Much of the equipment is specialized for particular purposes and tests are often underwritten by engineering and design companies with ideas or products to evaluate.
At Cornell University’s School of Civil and Environmental Engineering in Ithaca, N.Y., for instance, researchers in the Lifelines Group, in collaboration with Rensselaer Polytechnic Institute in Albany, N.Y., and the Sciencenter Discovery Museum, Ithaca, with support from pipe suppliers and utilities, are studying the effects of large differential ground deformation on buried pipeline and conduit. Experiments are conducted in a braced box filled with 100 tons of soil that can be ripped by simulated slip strike or thrust faults to measure the effects on subterranean infrastructure. Cornell says it conducted the largest test of this sort ever on March 2, warping a 16-in.-dia., 40-ft.-length of high-density polyethylene pipe into an “S” curve and its section into a flattened oval in a 4-ft lateral shift of half the soil encasing it.
|Lifeline. Cornell’s heavily-braced test box simulates faults. (Photo by Tom Sawyer for ENR)|
Another NEES equipment site, at the University of Southern California at San Diego’s Jacobs School of Engineering, has the country’s largest outdoor shake-table. It rattles with the rolling ground motions recorded at a sensor-laden building during the 1994 Northridge Earthquake in late 2004. The test now on the table is a 275-ton, full-scale, seven-story steel and concrete segment of an apartment building undergoing trials of new designs for rebar placement, bolted connections and wing-walls. “Our computational analysis suggests shear walls could be designed with significantly less reinforcing steel and still protect life and property,” says José Restrepo, a professor of structural engineering and co-principal investigator of the project.
A map with links to activities at all the NEES sites can be found at www.nees.org.