Structural engineers face many challenges in attempting to analyze and design structures that can withstand the devastating effects of earthquakes. The OpenSees software framework seeks to aid in this challenging task by letting earthquake engineers develop finite-element and finite-element-reliability applications for use in sequential, high-performance, and distributed processing environments.

OpenSees: A Framework for Earthquake Engineering Simulation

Modeling of cyclic mobility in saturated cohesionless soils

Computational modeling of cyclic mobility and post-liquefaction site response

The National Institute of Standards and Technology (NIST) funded a project to improve guidance to the earthquake engineering profession for selecting and scaling earthquake ground motions for the purpose of performing nonlinear response-history analysis. The project supported problem-focused studies related to defining target spectra for seismic design and performance assessment, response-spectrum matching, and near-fault ground motions. Recommendations are presented for target spectra, selection of seed ground motions, and scaling of motions to be consistent with different target spectra. Minimum numbers of sets of motions are recommended for computing mean component and systems responses, and distributions of responses. Guidance is provided on selection and scaling of ground motions per ASCE/SEI 7-10.

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Selecting and Scaling Earthquake Ground Motions for Performing Response-History Analyses | NIST

[1] The southernmost San Andreas fault has a high probability of rupturing in a large (greater than magnitude 7.5) earthquake sometime during the next few decades. New simulations show that the chain of sedimentary basins between San Bernardino and downtown Los Angeles form an effective waveguide that channels Love waves along the southern edge of the San Bernardino and San Gabriel Mountains. Earthquake scenarios with northward rupture, in which the guided wave is efficiently excited, produce unusually high long-period ground motions over much of the greater Los Angeles region, including intense, localized amplitude modulations arising from variations in waveguide cross-section.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005GL025472

Strong shaking in Los Angeles expected from southern San Andreas earthquake

In saturated clean medium-to-dense cohesionless soils, liquefaction-induced shear deformation is observed to accumulate in a cycle-by-cycle pattern (cyclic mobility). Much of the shear strain accumulation occurs rapidly during the transition from contraction to dilation (near the phase transformation surface) at a nearly constant low shear stress and effective confining pressure. Such a stress state is difficult to employ as a basis for predicting the associated magnitude of accumulated permanent shear strain. In this study, a more convenient approach is adopted in which the domain of large shear strain is directly defined by strain space parameters. The observed cyclic shear deformation is accounted for by enlargement and/or translation of this domain in deviatoric strain space. In this paper, the model formulation details involved are presented and discussed. A calibration phase is also described based on data from laboratory sample tests and dynamic centrifuge experiments (for Nevada sand at a relative density of about 40%).

Computational Model for Cyclic Mobility and Associated Shear Deformation

Soil-structure interaction may play a major role in the seismic response of a bridge structure. Specifically, soil layers of low stiffness and strength may result in permanent displacement of the abutments and foundations, thus imposing important kinematic conditions to the bridge structure. A study to illustrate such phenomena is undertaken based on three-dimensional nonlinear dynamic finite-element (FE) modeling and analysis (for a specific bridge configuration under a given seismic excitation). A bridge-foundation-ground model is developed based on the structural configuration and local soil conditions of the Humboldt Bay Middle Channel Bridge. The FE model and nonlinear solution strategy are built in the open-source software platform OpenSees of the Pacific Earthquake Engineering Research Center. Based on the simulation results, the overall system seismic response behavior is examined, as well as local deformations/stresses at selected critical locations. It is shown that permanent ground deformation may induce settlement and longitudinal/transversal displacements of the abutments and deep foundations. The relatively massive approach ramps may also contribute to this simulated damage condition, which imposes large stresses on the bridge foundations, supporting piers, and superstructure.

/pdf/three-dimensional-seismic-response-of-humboldt-bay-bridge-2fdsvkag5m.pdf

Three-Dimensional Seismic Response of Humboldt Bay Bridge-Foundation-Ground System

Permeability of a liquefiable soil profile may affect the rate of pore-pressure buildup and subsequent dissipation during and after earthquake excitation. Consequently, effective soil confinement a...

Zhaohui Yang

Papers

Computational Model for Cyclic Mobility and Associated Shear Deformation

Modeling of cyclic mobility in saturated cohesionless soils

Computational modeling of cyclic mobility and post-liquefaction site response

Three-Dimensional Seismic Response of Humboldt Bay Bridge-Foundation-Ground System

Influence of Permeability on Liquefaction-Induced Shear Deformation