It is important to investigate strong-motion time series recorded at dams to understand their complex seismic responses. This paper develops a strong-motion database recorded at existing embankment dams and analyzes correlations between dam dynamic responses and ground-motion parameters. The Japan Commission on Large Dams database used here includes 190 recordings at the crests and foundations of 60 dams during 54 earthquakes from 1978 to 2012. Seismic amplifications and fundamental periods from recorded time series were computed and examined by correlation with shaking intensities and dam geometries. The peak ground acceleration (PGA) at the dam crest increases as the PGA at the foundation bedrock increases, but their ratio gradually decreases. The fundamental period broadly increases with the dam height and PGA at the foundation bedrock. The nonlinear dam response becomes more apparent as the PGA at the foundation bedrock becomes >0.2 g. The prediction models of these correlations are proposed for estimating the seismic response of embankment dams, which can inform the preliminary design stage.
In a seismic hazard analysis (SHA), the earthquake loading level should be predicted for one or more ground motion intensity measures (IMs) that are expected to relate well with the engineering demand parameters (EDPs) of the site. In this study, the goal was to determine the IMs that best relate to embankment dam deformations based on nonlinear deformation analysis (NDA) results of two embankment dams with a large suite of recorded ground motions. The measure utilized to determine the “best” IM was standard deviation in the engineering demand parameter (e.g., deformation) for a given IM, also termed “efficiency.” Results of the study demonstrated that for the NDA model used, Arias intensity (AI) was found to be the most efficient predictor of embankment dam deformations. In terms of pseudo-spectral acceleration (PSA)-based IMs, the PSA at short periods and then in the general range of the natural period of the dams was seen to be the most efficient IM, but was in almost all cases not as efficient as AI.
It is essential to obtain shear modulus reduction and damping ratio curves to perform dynamic analyses of earth-cored embankment dams. Many studies have been performed for dynamic properties of clayey soils, but they have been limited for earth core materials of dams. This study conducted resonant column tests to obtain shear modulus reduction (G/Gmax) and damping ratio (D) curves for 31 specimens (17 undisturbed and 14 remolded specimens) from 13 earth-cored embankment dams. Empirical G/Gmax and D curves are proposed for dynamic properties of clayey earth core materials. Fitting curves are provided by using the functional forms of the Ramberg–Osgood and Darendeli models. The observation shows that the undisturbed earth cores yield relatively higher G/Gmax and lower D curves than the remolded cores. G/Gmax curves of compacted earth cores are relatively higher than those of Vucetic and Dobry curves for a similar level of plasticity index. Uncertainty and bias are calculated by performing residual analysis, which shows that there is no clear bias in predicting G/Gmax and the uncertainties between undisturbed earth core materials and natural deposits are at a similar level. A proposed empirical relationship of G/Gmax and D curves for earth core materials can be utilized for dynamic analyses of embankment dams for cases where there is insufficient in situ data.
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