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Scenario-based earthquake simulations at regional scales hold the promise in advancing the state-of-the-art in seismic risk assessment studies. In this study, a computational workflow is presented that combines (i) a broadband Green's function-based fault-rupture and ground motion simulation-herein carried out using the "UCSB (University of California at Santa Barbara) method", (ii) a three-dimensional physics-based regional-scale wave propagation simulation that is resolved at max = 11.2 Hz, and (iii) a local soil-foundation-structure finite element analysis model. These models are interfaced with each other using the domain reduction method. The innermost local model-implemented in ABAQUS-is additionally enveloped with perfectly matched layer boundaries that absorb outbound waves scattered by the structures contained within it. The intermediate wave propagation simulation is carried out using Hercules, which is an explicit time-stepping finite element code that is developed and licensed by the CMU-QUAKE group. The devised workflow is applied to a 80 × 40 × 40 km 3 region on the European side of Istanbul, which was modeled using detailed soil stratigraphy data and realistic fault rupture properties, which are available from prior microzonation surveys and earthquake scenario studies. The innermost local model comprises a chevron-braced steel frame building supported by a shallow foundation slab, which, in turn, rests atop a three-dimensional soil domain. To demonstrate the utility of the workflow, results obtained using various simplified soil-structure interaction analysis techniques are compared with those from the detailed direct model. While the aforementioned demonstration has a limited scope, the devised workflow can be used in a multitude of ways, for example, to examine the effects of shallow-layer soil nonlinearities and surface topography, to devise site-and structure-specific seismic fragilities, and for calibrating regional loss models, to name a few.

Utilizing an array of new diagnostics and simulation/modelling techniques, recent DIII-D experiments have elucidated a variety of energetic ion transport behaviour in the presence of instabilities ranging from large-scale sawteeth to fine spatial scale microturbulence. Important new insights include sawteeth, such as those of the ITER baseline scenario, causing major redistribution of the energetic ion population; high levels of transport induced by low-amplitude Alfvén eigenmodes can be caused by the integrated effect of a large number of simultaneous modes; and microturbulence can contribute to the removal of alpha ash while having little effect on fusion alphas. This paper provides an overview of recent and upcoming results from the DIII-D Energetic Particles research programme.

Numerous experiments and prior analyses have confirmed that the angle of incidence of a seismic wave can significantly affect ground response and dynamic soil-structure interaction (SSI) behavior. Realistically, obliquely incident waves will be generated due to the soil heterogeneity and stratigraphy, which can lead into complex wave propagation and scattering patterns. In this study, we propose a novel methodology that (i) utilizes the wave potential theory to derive the 3D time-domain analytical solutions for free-field response under obliquely incident SV waves in layered soil media; (ii) makes use of high-fidelity numerical tools-namely, the domain reduction method (DRM) and the perfectly matched layers (PMLs)-to inject the obliquely incident waves into the domain of interest and to absorb the outgoing scattered motions, respectively; (iii) enables nonlinear time-domain site response and SSI analyses that feature an advanced constitutive model for soil. Finally, a 3D 20-story steel building is modeled as a case study. The building rests on a two-layer half-space and is subjected to an obliquely incident seismic wave. The SV wave's angles of incidence are varied to investigate its effects on structural responses, such as horizontal, vertical, and rotational floor accelerations, as well as interstory drift ratios.

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Tuned mass dampers (TMDs) are widely implemented in many types of structures, such as tall buildings, wind turbines, towers, and bridges, to enhance the structural performance subjected to seismic and wind loading. In the present study, we aim to comprehensively investigate the effectiveness of TMD, by performing seismic vulnerability assessment of a 20-story steel building equipped with TMD and considering the soil-structure interaction (SSI) effects. A suite of high-fidelity three-dimensional nonlinear finite element simulations-in which nonlinear constitutive models are adopted for both structural components and soil, and Domain Reduction Method (DRM) and Perfectly Matched Layer (PML) are utilized to inject the seismic ground motions and represent the semi-infinite contents of the soil media, respectively-are conducted to obtain the structural responses. Finally, the performance of TMD is examined by comparing the fragility curves obtained under different conditions, i.e., with and without TMD, with and without SSI. It is observed that the TMD can notably decrease the structural demands, while the SSI effects can increase the fragility of structures, especially under strong earthquakes.

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Using results from 57 large‐scale physics‐based fault‐rupture and wave propagation simulations, this research aims to evaluate the seismic risk, loss, and resilience of more than 16,000 reinforced concrete buildings in the Zeytinburnu district of Istanbul, Turkey. For each building and under each earthquake scenario, the spatially varying site‐specific simulated ground motions were used for performing three‐dimensional nonlinear time‐history analyses. The resulting structural responses—such as peak story drift ratios (PSDR) and peak floor accelerations (PFAs)—were utilized to conduct three region‐scale tasks: (i) building‐ and site‐specific seismic fragility analysis for both structural and nonstructural components of each building; (ii) intensity‐based seismic loss assessment using the FEMA P58 methodology and Monte Carlo simulations; and (iii) resilience evaluation based on the expected time of recovery predicted through FEMA P58. Moreover, both inertial and kinematic soil–structure interaction (SSI) effects were considered using a substructuring method for all three tasks. Site‐specific soil properties were utilized to compute the coefficients of soil springs and dashpots, as well as the foundation input motions. The SSI effects were investigated by comparing the fragility, loss, and resilience indices obtained with and without considering SSI.