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Project increases safety of building deep

3/12/2012 11:45:00 AM

Yeh Center
Yeh Center

Photos: Above, the Transbay Transit Center in San Francisco, where extensive underground structures will exist in close proximity to tall buildings (BusinessWire); Below, Youssef Hashash.

By Brian Kornell

As U.S. cities continue to expand, the sustainability of urban environments is a pressing concern. Cities are faced with providing more space for people to live and work. Often, the most efficient option in crowded urban areas is to build vertically, resulting not only in taller structures, but also in ones that take advantage of the more cost-effective underground space.
This necessity in areas that are seismically active brings particular challenges, says CEE Professor Youssef Hashash.
“With urban renewal, we are building very tall structures next to extensive underground structures in many U.S. cities, and we do not know how they will perform during large seismic events,” he said.
This question is the central focus of a study, funded by the Network for Earthquake Engineering Simulation (NEES), on which Professor Hashash is collaborating with colleagues from Colorado University (CU) Boulder and the San Francisco-based engineering firm, Arup. Since this is not only a U.S. concern, there is also a parallel study happening in Japan. Both arms of the project are focusing on how the need for more living space above-ground—for example taller buildings—and more underground transportation solutions—for example, subways—can be balanced with safe, sustainable design methods.
The biggest challenge of the project is that the issue of how underground structures will interact with taller structures during seismic events is simply not currently understood, Hashash says. In order to get a better sense of what happens to these structures during an earthquake, researchers at CU Boulder are carrying out physical experiments on models that simulate seismic events. Hashash and his team will use the information gathered in these tests to perform complementary computational modeling. The result will be a greater understanding of how buildings and underground structures interact when under stress from an earthquake. 
Given how complex underground structures are becoming, the study will not only be looking at stand-alone structures such as parking garages, but also other subterranean structures, including tunnels that run under buildings and/or criss-cross one another. Having a clearer picture of these interactions will lead to better design tools and information for engineering and design firms—“a product that is of immediate practical use to the profession,” Hashash says.
The inclusion of Arup, which focuses, in part, on innovative, sustainable infrastructure designs, as a project collaborator is key to ensuring the tools developed from the study are of effective use to the practitioner, Hashash says.
These new tools will make it safer and more sustainable to build up and down in close proximity—a growing necessity for urban environments, Hashash says.
“The use of the underground is part of the objective to have more sustainable, more livable cities,” Hashash says.