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Offshore wind turbine (OWT) structures are subject to wave, wind, and seismic loading. Due to the cyclic nature of these loads, OWT foundations can be vulnerable to cumulative deformation and liquefaction triggered by waves and earthquakes. The effects of cumulative deformation and liquefaction on the monopile-supported OWT are not fully appreciated. This paper develops a three-dimensional numerical model for analyzing the seismic performance of large monopile-supported OWT under the long-term effect of cyclic loading. The numerical model was established employing FLAC3D and utilizing SANISAND constitutive model to simulate the soil behavior. The numerical model was validated by comparing its predictions with the results of dynamic triaxial tests and centrifuge tests. A simplified densification and subsidence site model was integrated into the numerical model to facilitate considering the long-term effect of cyclic loading. The numerical model was then used to conduct a comprehensive study to evaluate the influence of long-term cyclic loading on the natural frequency and seismic response of OWT structure. The results demonstrated that the densified subsidence zone around monopile increased the liquefaction resistance. However, the horizontal displacement of pile and the response acceleration of tower-top increased due to soil subsidence around monopile.

This paper seeks to develop a module for automated model construction of a pipeline network using geographical information system (GIS) of lifeline, for the sake of more rational seismic disaster assessment. The module is assigned a functionality which enables to generate two types of analysis models, a simple 2D model and a 3D model with high fidelity for pipe configuration. The module is coded in an objective oriented programming, so that it is easier to be extended to generate other types of analysis models. The module is applied to actual GIS, and the configuration of the generated model is verified. As an example, numerical analysis is made for the automatically constructed models by using a commercial finite element method package, and it is shown that these models are mechanically consistent and can be used for seismic disaster assessment.

A seismic response analysis of a reinforced concrete (RC) pier has been undertaken using seismic waves recorded at the Takatori station during the southern Hyogo perfecture earthquake in 1995 in Japan. Distinguishing characteristics of this analysis are as follows. First, the RC pier has been modeled using the finite element method with a solid mesh. The analysis model has been generated using tetrahedral elements with node connectivity, not only in the concrete but also in the reinforcement steel. Also, an analysis has been undertaken on fracture treatments in the concrete. Using PDS-FEM, a system of suitable fractures in the concrete resulting from the seismic event can be simulated. Ultimately, a finite element model is established with a fine tetrahedron mesh with about 20 million elements. We calculate a seismic response analysis using the K computer at the RIKEN Advanced Institute for Computational Science, and compare that result with a seismic experiment in E-Defense to confirm the computational approach.

In the present study, a large-scale seismic response analysis of a super-high-rise steel frame considering the soil–structure interaction is conducted. A high-fidelity mesh of a 31-story super-high-rise steel frame and the ground underneath it, which is made completely of hexahedral elements, is generated. The boundary conditions that are consistent with the solution of the one-dimensional (1D) wave propagation analysis are imposed on the side and bottom surfaces of the ground. The waves are assumed to propagate in the vertical direction. The 1D wave propagation analysis is conducted under the excitation of the JR Takatori record of the 1995 Hyogoken-Nanbu earthquake. The parallel large-scale analysis is performed using the K computer, which is one of the fastest supercomputers in the world. The results of the models with and without the ground are compared, which reveals that the results obtained by these two models are very similar because the ground is assumed be sufficiently hard in the present study.

This study investigated the applicability of a nonlinear analysis method that considers progressive failure to evaluating the stability of rock slopes, including post-earthquake residual displacement. The vibration step of the nonlinear analysis, which begins after residual displacement occurs, was found to match that of a dynamic centrifugal model test. The nonlinear analysis was concluded to be relatively conservative because it calculated a slightly larger residual displacement than that observed during the model test. A real-scale soft rock slope was analyzed, and the results showed that the proposed analysis method is useful for evaluating slope seismic stability, including post-earthquake residual displacements.

On May 12 2008, a great earthquake of magnitude 8.0 occurred in Wenchuan County of Sichuan Province, western China. The Zipingpu Concrete Face Rock-fill Dam (CFRD) with 156m height, which was 17km away from the epicenter, was considerably damaged by Wenchuan Earthquake. The site investigation showed that the maximum permanent settlement was about 100 cm and the horizontal displacement was about 60 cm as a result of the earthquake. It was estimated that the peak acceleration in the top the dam along the axial and vertical direction was about 2000gal, and the peak acceleration along the river was about 1600gal. It was calculated that peak acceleration of dam bedrock was more than 500gal and the seismic intensity was more than 9 degrees. The actual experience of the peak acceleration and seismic intensity of the Zipingpu CFRD in this earthquake was far ahead of the original design standards. Based on the in-situ investigation, 3D numerical model of the Zipingpu CFRD was established and the numerical simulation analysis on Wenchuan earthquake damage was carried out. The calculated results showed that the numerical analyses were consistent to the in-site investigation. The seismic performance of the Zipingpu CFRD during Wenchuan earthquake was reproduced in the numerical model. The acceleration response, permanent deformation and damage characteristics of the Zipingpu CFRD in Wenchuan earthquake were understood.