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UB/MCEER Investigator Reports Damage to Eccentrically Braced Frames following the 2011 Christchurch New Zealand Earthquake

Michel Bruneau, Professor, Department of Civil, Structural and Environmental Engineering, University at Buffalo, visited New Zealand on behalf of MCEER to assess the damage caused by the February 21, 2011 (6:51 p.m. EST; 23:51 UTC) earthquake that struck near the city center of Christchurch. He surveyed the same area as part of the EERI team following the September 2010 Darfield earthquake, and is again focusing on damage to bridges and steel buildings. This earthquake is possibly the first time in modern history that a damaging earthquake has occurred in an urban area twice in the same year, with the second event producing significantly more damage than the first, and it is anticipated that new lessons will be learned as a result.

He was joined by Mark Yashinsky, Senior Bridge Engineer, California Department of Transportation, who represented PEER; Roberto Leon, Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology; Greg MacRae, Associate Professor, Civil and Natural Resources Engineering, University of Canterbury; and G. Charles Clifton, Associate Professor of Civil Engineering, Department of Civil and Environmental Engineering, The University of Auckland. He was in New Zealand from February 27 through March 4, 2011.

Preliminary Observations

Preliminary findings include valuable observations on the performance of steel eccentrically braced frame (EBF) structures. This is the first time that the level of excitation of an earthquake was at least as large as or has exceeded the design basis in an area where steel eccentrically braced frames were used. Many have performed very well, but a notable exception is shown in the accompanying photos, where undesirable fractures developed in the links of EBF frames. This is the first time that this type of damage has been observed following an earthquake. The earthquake provides the first opportunity to observe how these types of structures perform and/or fail in large earthquakes.

Global view of fractured Eccentrically Braced Frame (EBF)

Close up of fractured bottom flange EBF link (undesirable behavior)

EBF link that did not fracture but deformed substantially in the inelastic range (per intended design)

Preliminary Report

Field observations of the performance of selected steel structures are discussed by some members of the team and their colleagues in a preliminary paper. The paper, authored by Michel Bruneau, Professor, Dept. of Civil, Structural, and Environmental Engineering, University at Buffalo; Charles Clifton, Associate Professor in Structural Engineering, Dept. of Civil Engineering, University of Auckland; Greg MacRae, Associate Professor in Structural Engineering, Dept. of Civil and Natural Resources Engineering, University of Canterbury, Christchurch; Roberto Leon, Professor, Dept. of Civil Engineering, Georgia Tech; and Alistair Fussell, Senior Structural Engineer, Steel Construction, New Zealand; focuses on the performance of selected steel structures. The performance of concentrically braced frames, eccentrically braced frames, moment resisting frames, and industrial storage racks is of particular interest. The authors report that with a few notable exceptions, steel structures performed well during this earthquake, to the extent that inelastic deformations were less than what would have been expected given the severity of the recorded strong motions. Some hypotheses are formulated to explain this satisfactory performance.

--Submitted by Michel Bruneau, March 2, 2011

--Updated by Michel Bruneau, March 11, 2011

Additional Resources on the New Zealand Earthquake

Related Publications

Journal articles

Anagnostopoulou, M., Bruneau, M., Gavin, H., (2010). “Performance of Churches During the Darfield Earthquake of September 04, 2010”, New Zealand Society for Earthquake Engineering Bulletin, Vol.43, No.4, pp.374-381.

Bruneau M, Clifton C, MacRae G, Leon R, Fussell A.(2011). “Steel Building Damage from the Christchurch Earthquake Series of 2010/2011”, Journal of the Structural Engineering Society New Zealand (SESOC), Vol.24, No.2., pp.27 - 42.

Bruneau, M., Anagnostopoulou, M., MacRae, G., Clifton, C., Fussell, A., (2010). “Preliminary Report on Steel Building Damage from the Darfield (New Zealand) Earthquake of September 4, 2010", New Zealand Society for Earthquake Engineering Bulletin, Vol.43, No.4, pp.351-359.

Bruneau, M., Clifton, C., MacRae, G., Leon, R., Fussell, A., Martin, P.O., (2011). “Comportement des Bâtiments Métalliques lors du Séisme de Christchurch, Nouvelle Zélande, le 22 Février 2011,” Revue Construction Métallique, No.4, pp.3-25.

Clifton, C., Bruneau, M., MacRae, G., Leon, R., Fussell, A., (2011). “Steel Structures Damage from the Christchurch Earthquake of February 22, 2011, NZST,” Bulletin of the New Zealand Society for Earthquake Engineering, Vol.44, No.4, pp.297-318.

Palermo, A., LeHeux, M., Bruneau, M., Anagnostopoulou, M., Wotherspoon, L., Hogan, L., (2010). “Preliminary Findings on Performance of Bridges in the 2010 Darfield Earthquake”, New Zealand Society for Earthquake Engineering Bulletin, Vol.43, No.4, pp.412-420.

Palermo, A., Wotherspoon, L., M., Wood, J., Chapman, H., Scott, A., Hogan, L., Kivell, A., Camnasio, E., Yashinsky, M., Bruneau, M., Chouw, N., (2011). “Lessons Learnt from 2011 Christchurch Earthquakes: Analysis and Assessment of Bridges,” Bulletin of the New Zealand Society for Earthquake Engineering, Vol.44, No.4, pp.319-333.

Articles (Newsletters and web reports)

Comerio, M., Arendt, L., Bruneau, M., Dusicka, P., Gavin, H., Roeder, C., Turner, F., Lai., T., Williams, R., Boyd, O., Anagnostopoulou, M., Holmes, W., O’Rourke, T., (2010). “The Mw 7.1 Darfield (Canterbury), New Zealand Earthquake of September 4, 2010”, EERI Special Earthquake Report, EERI Newsletter, Vol 44, No.11, November 2010.

Comerio, M., Elwood, K., Berkowitz, R., Bruneau, M., Dismuke, J., Gavin, H., Gould, N., Jaiswal, K., Kirsch, T., Lai., T., Marshall, J., Mayes, R., Mitrani-Reiser, J., Morgan, T., Mote, T., Peek, L., Sritharan, S., Sutton, J., Turner, F., Wein, A., Yashinsky, M., O’Rourke, T., Fleischman, R., (2011). “The M 6.3 Christchurch, New Zealand, Earthquake of February 22, 2011" EERI Special Earthquake Report, EERI Newsletter, Vol 45, No.5, May 2011.