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Common practice for evaluating the seismic performance of earth dams uses design ground motions selected to be consistent with a target design response spectrum, which are subsequently used in dynamic analyses that estimate seismically induced displacements as an index of performance. This approach involves selecting the probability of exceedance of a ground-motion parameter rather than the probability of exceeding the seismically induced displacements. This implicitly assumes that the different response spectra levels (e.g., different SA hazard levels or 50th percentile versus 84th percentile ground motions) is correlated to the different levels of seismically induced displacement. This may not always be the case and can be particularly problematic when evaluating earth structures located in a tectonic setting with multiple source types (e.g., subduction and shallow crustal earthquakes). This can lead to high variability in the estimated displacements, making the selection of a representative overall displacement computed from the different source types not immediately clear. In this study, we propose simplified approaches to select representative displacements for dams affected by earthquakes from multiple source types and we evaluate their performance by constructing displacement hazard curves that rely on the conditional scenario spectra (CSS) framework. We illustrate the application of the proposed procedures for a fictitious dam located in Vancouver, British Columbia, and offer recommendations for using the proposed procedures in practice. Finally, we propose a new procedure for selecting a subset of ground motions for use in complex dynamic analyses [e.g., FEM or finite-difference methods (FDM)] based on the deaggregation from displacement hazard curves rather than the deaggregation from elastic response spectra hazard curves. [ABSTRACT FROM AUTHOR]

Performance-based probabilistic approaches (PBPAs) for estimating seismically-induced slope displacements (D) provide hazard-consistent estimates through the evaluation of D hazard curves (DHCs), and hence, its use in practice is appealing. Importantly, the epistemic uncertainty to develop a DHC needs to be considered, which is typically done using a logic tree approach with discrete branches for the system properties and seismic displacement models (SDM). However, the few existing SDMs, do not allow one to accurately capture the full epistemic uncertainty range. This study uses the polynomial chaos (PC) theory to develop a computationally efficient framework for propagating the epistemic uncertainty in the median D , associated with alternative SDM models. PC expansions allow one to account for the epistemic uncertainty distribution in DHCs in a computationally efficient manner, which cannot be possible using the traditional logic tree approach. The necessary steps for the implementation of the proposed framework are discussed, and an illustrative example of its application in engineering practice is presented. [ABSTRACT FROM AUTHOR]

Earthquake ground motions in the near-fault region frequently have intense, double-sided pulses in the velocity-time series that can be very damaging to structures. Many of these velocity pulses are attributed to the effects of forward directivity, which occurs when a fault ruptures toward a site. However, pulses are not always observed in the forward directivity region, and some pulses cannot be explained by forward directivity. The relative contribution of pulse-type motions to the overall seismic hazard should be considered when selecting records in a suite of design ground motions for a site in the near-fault region. This study uses a new scheme to classify records from an enhanced database of records from shallow crustal earthquakes that have the closest site-to-source distances less than 30 km with moment magnitudes greater than 6.0 as either pulse or nonpulse motions. The resulting database of 673 records from 52 earthquakes contains 141 pulses, including 74 explained well by forward directivity. Logistic regression is used to develop a simple model to estimate the proportion of pulse motions as a function of closest site-to-source distance and epsilon of the seismic hazard. The resulting relationship can be used to estimate the number of pulse-type motions that should be included within a suite of ground motions to represent the proper contribution of pulse motions to the seismic hazard. Guidance is also provided for selecting pulse records. [ABSTRACT FROM AUTHOR]

Regression models are presented for the dynamic properties of highly organic soils. The models are based on a database of triaxial and resonant-column/torsional-shear cyclic loading tests on thin walled tube samples mainly retrieved from the Sacramento-San Joaquin Delta. The soils in this database range from highly fibrous peat to amorphous organic clays with organic contents (OC) ranging from 14–81%, water contents ranging from 88–495%, total densities (ρ) ranging from 1.056–1.450 Mg/m3, and effective consolidation stresses (σvc′) ranging from 11–135 kPa. The secant shear modulus (G) and equivalent damping ratio (ξ) were modeled as variables dependent on the shear strain amplitude (γc), consolidation stress (σvc′), and OC. The residuals of the regression models were analyzed against other predictor variables including undisturbed density (ρ), loading frequency (f), and number of loading cycles (N). A regression model for ρ was developed, and conditional probabilities were used to improve the estimation of G and ξ when ρ measurements were available. The database of in situ measurements of shear wave velocity (Vs) was used to adjust the regression model for in situ conditions. Variances and correlations in the regression models are presented. [ABSTRACT FROM AUTHOR]

Presents a study which developed empirical relationships between magnitude, site-source distance, site condition and factors representing near-fault rupture directivity effects for soil liquefaction analysis. Description of the database used in the study; Procedures for computing number of cycles from accelerograms; Evaluation of cyclic resistance ratio factors.

Describes the frequency content of earthquake ground motions for earthquake engineering. Characteristics of a strong earthquake ground motion; Examination of the three simplified frequency content parameters; Identification of the mean period as the best simplified frequency content characterization parameter.

Investigates the dynamics of solid waste landfills through finite element analyses. Characterization of strain-dependent shear modulus reduction and material dumping relationships by medium plasticity clay; Usage of the statistical evaluation procedure for comparison of dynamic analysis results.