Analysis of the Recorded Response of Lexington Dam During Various Levels of Ground Shaking

by F. Makdisi, C.Y. Chang, Z. Wang and C. Mok

Makdisi, F., C.Y. Chang, Z. Wang and C. Mok (1991). Analysis of the Recorded Response of Lexington Dam During Various Levels of Ground Shaking. SMIP91 Seminar on Seismological and Engineering Implications of Recent Strong-Motion Data, p. 10-1 - 10-10.

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Abstract

Lexington Dam, a 200-foot-high compacted earthfill embankment, was strongly shaken by the Loma Prieta 1989 earthquake (M_w 7) as well as by two smaller events (M_L 5) in June 1988 and August 1989. The dam was instrumented as part of the California Strong Motion Instrumentation Program. The recordings at Lexington Dam due to at least three different levels of ground shaking provided valuable data for examining the nonlinear strain-dependent behavior of the embankment materials due to earthquake shaking. This paper summarizes the results of analyses of the recordings at the dam crest and abutment for two of the three earthquakes described above. The analyses included Fourier spectral ratio computations (crest to abutment) to examine changes in the fundamental natural period of the dam due to different levels of shaking; and one- and two- dimensional dynamic response analyses to evaluate the nonlinear strain-dependent behavior of the embankment materials at two levels of earthquake shaking.