Jonathan D. Bray, PIUniversity of California, Berkeley

Tara C. Hutchinson, Co-PIUniversity of California, San Diego

Bruce L. Kutter, Co-PIUniversity of California, Davis

Robert K. Reitherman, Co-PIConsortium of Universities for Research in Earthquake Engineering (CUREE)

Andrew S. Whittaker, Co-PIUniversity at Buffalo, SUNY

Gregg L. Fiegel, Faculty AssociateCal Poly – San Luis Obispo

SEISMIC PERFORMANCE ASSESSMENT IN DENSE URBAN ENVIRONMENTS: EVALUATION OF STRUCTURE-SOIL-STRUCTURE INTERACTION SYSTEMS USING CENTRIFUGE TESTS

PROJECT TEAM In dense urban areas buildings are arranged in clusters (i.e., the city block). However, these buildings are designed assuming they respond independently of one another in earthquakes, thereby ignoring the complex effects of interactions between buildings that occur through the ground during earthquakes. This phenomenon is referred to as structure-soil-structure interaction (SSSI). SSSI effects can be both beneficial and detrimental with respect to the seismic response of soil-foundation-structure interaction (SFSI) systems. Currently, SSSI effects are poorly understood by engineers and are not considered in any modern design code, because of a dearth of field data, experimental data, and analytical research.

A series of dynamic centrifuge tests are being performed to examine the effects of SFSI in dense urban environments using the centrifuge-shaking table at the University of California at Davis Center for Geotechnical Modeling – a NEES equipment site. The ground motion selection focuses on a site in Los Angeles; where both near-fault and ordinary ground motions are considered.

PROJECT TESTS

Test-0 was conducted to develop a suite of appro-priate earthquake ground motions. The earth-quake motion influences significantly seismic site response, the dynamic response of a structure, SSI, liquefaction, and other earthquake engineer-ing related phenomena. With this in mind, the re-searchers selected and calibrated a suite of earth-quake motions for use in centrifuge experiments conducted at the Center for Geotechnical Model-ing at the University of California, Davis. These motions are appropriate for projects affected by shallow, crustal earthquakes in active plate mar-gins, such as in coastal California.

In Test-1 and Test-2, a prototype three-story steel, moment-frame building founded on spread footings and a nine-story steel, moment-frame building founded on a three-story basement were tested. In Test-1, the two structures were located as far apart as possible, and are thus considered to be essentially independent from one another. In Test-2, they were placed adjacent to each other.

Test-3 and Test-4 built upon information from prior tests, with continued emphasis on the study of building adjacency, structural and foundation nonlinearity, and inertial soil-structure interaction. In each of these tests model single story moment frame and rocking-dominated wall buildings were used. Test-4 incorporated a configuration to support the study of anti-plane SSSI as well as an L-shaped layout of three buildings. This more realistic ‘city block’ arrangement provided insight into more complex multi-axis aspects of SSSI.

www.nees-cityblock.org

STUDENT RESEARCHERS

Henry B. Mason Katherine C. JonesUniversity of California, Berkeley

ZhiQiang ChenNicholas W. TrombettaUniversity of California, San Diego

Benjamin Y. ChoyHamilton PuangnakUniversity of California, Davis

Jack MontgomeryRoshani J. PatelKyle MarshallClayton ProtoStefanie GilleJonathan LundJeannie TranPatrick BassalDaniel PaezCal Poly – San Luis Obispo

Chandrakanth BolisettiUniversity at Buffalo, SUNY

PROJECT UPDATE - February 7, 2013

The results of Test-5, the first of two experiments that included liquefiable foundation soils, are currently being analyzed. The next scheduled test date will be in May 2013. The reader is encouraged to track the project’s progress at: www.nees-cityblock.org.

PUBLICATIONS/PRODUCTS TO DATE

Trombetta, N.W., Hutchinson, T.C., Mason, H.B., Zupan, J.D., Bray, J.D., Bolisetti, C., Whittaker, A., Chen, Z., and Kutter, B.L., “Centrifuge modeling of structure-soil-structure interaction: seismic performance of inelastic building models”, (2012). Conference Proc., AcceptedCollection: 15th World Conference in Earthquake Engineering (WCEE) Bibliography: Lisbon, Portugal

Trombetta, N.W., Fiegel, G.L., and Mason, H.B., “Learning through Doing: Using Geotechnical Research to Prepare Undergraduates for Graduate School”, (2012). Conference, Published Collection: Proceedings: Shaking the Foundations of Geo-Engineering Education, ISSMGE Specialty Conf. Bibliography: Galway, Ireland

R. Reitherman, J. D. Bray, G. Fiegel, T. C. Hutchinson, B. L. Kutter, H. B. Mason, N. Trombetta, and A. Whittaker, “Understanding Soil-Structure-Foundation Interaction in a Dense Urban Environment”, (2011).

For a complete list, please visit www.nees-cityblock.org.

Sponsor:

George E. Brown, Jr. Network for Earthquake Engineering Simulation

(NEES) Research (NEESR-SG)

National Science Foundation

This material is based upon work supported by the National Science Foundation (NSF) under Grant No. CMMI-0830331 through the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES). The “Seismic Performance Assessment in Dense Urban Environments: Soil-Structure Interaction on the Scale of a City Block” project is a collaborative effort that includes the University of California, Berkeley (lead institution), University of Buffalo-SUNY, University of California, Davis, University of California, San Diego, California Polytechnic State University, San Luis Obispo, and the Consortium of Universities for Research in Earthquake Engineering. This project utilizes the NEES equipment site at the University of California, Davis. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF.