Semi-empirical models based on in situ geotechnical tests have been the standard-of-practice for predicting soil liquefaction since 1971. More recently, prediction models based on free, readily ...available data were proposed. These “geospatial” models rely on satellite remote-sensing to infer subsurface traits without in situ tests. Using 15,223 liquefaction case-histories from 24 earthquakes, this study assesses the performance of 23 models based on geotechnical or geospatial data using standardized metrics. Uncertainty due to finite sampling of case-histories is accounted for and used to establish statistical significance. Geotechnical predictions are significantly more efficient on a global scale, yet successive models proposed over the last 20 years show little or no demonstrable improvement. In addition, geospatial models perform equally well for large subsets of the data—a provocative finding given the relative time- and cost-requirements underlying these predictions. Through this performance comparison, lessons for improving each class of model are elucidated in detail.
•An innovative approach for dynamic response reconstruction is proposed.•It is applicable to reconstruct structural responses under extreme loading conditions.•This approach is based on Segment based ...Generative Adversarial Network (SegGAN).•Numerical and experimental investigations are conducted to validate the approach.•Good structural response reconstruction results are obtained, even with nonlinearities.
Reconstruction of lost responses under external loads, e.g. ambient and seismic loading conditions, is important for structural health monitoring to evaluate the safety of structures. This paper proposes a Segment based Conditional Generative Adversarial Network (SegGAN), which is a powerful deep learning model for solving pixel-to-pixel tasks, to conduct structural dynamic response reconstruction. The proposed network consists of a bottlenecked generator and a segment based discriminator. Generator features skip and dense connections to improve feature extraction, and segment based discriminator uses conditioned input to facilitate generator to learn detailed and robust features. Numerical studies on a steel frame structure model are conducted to evaluate the accuracy and noise immunity of using SegGAN for structural response reconstruction. The feasibility of using the reconstructed response for damage detection is also investigated. Numerical study on a nonlinear building model is performed to validate the capability and accuracy of using the proposed approach in nonlinear response features extraction and response reconstruction. Experimental studies on a laboratory steel frame structure are conducted to investigate the effectiveness and robustness of the proposed approach with limited training data from noisy and operational conditions, and a few sample data from earthquake loads for testing. The reconstruction results of using the proposed approach are compared with those generated by a densely connected network (DenseNet) with the same configuration as the generator and a traditional convolutional neural network (CNN). Responses from available and unavailable sensors are selected as input and output of these three networks, respectively. SegGAN outperforms the other two networks and produces outstanding reconstruction results in both time and frequency domains.
The suction bucket foundation is considered as an effective option for offshore wind turbines because of its advantages in rapid installation and recyclability. However, the depth of the suction ...bucket inserted into the seabed is shallower compared to the monopile. Earthquakes and liquefaction threaten the safety and stability of suction bucket foundations in the North Sea of Europe and the Chinese offshore where earthquakes are active and the seabed is prone to liquefaction. This paper investigated the behavior of the suction bucket foundation located in the liquefiable sand under earthquakes using an advanced liquefaction model. The FE-FD method with the cyclic mobility constitutive model for soil was used to carry out the nonlinear dynamic analyses. Responses of the excess pore water pressure ratio, acceleration, displacement, and rotation were studied under different earthquake magnitudes and sand density. The distribution of excess pore water pressure of the suction bucket foundation from the results show strong space-time characteristics. The failure mechanism of the suction bucket foundation after liquefaction was revealed. The numerical results indicate that offshore wind turbines will be subjected to permanent displacements and tilt to reach 40% of the safety threshold due to earthquakes and liquefaction. Thus, seismic load and liquefaction of the foundation must be considered in the design.
•Suction bucket foundation response under earthquakes was investigated using an advanced liquefaction model.•The excess pore water pressure ratio, acceleration, displacement, and rotation were studied.•The failure mechanism of the suction bucket foundation after liquefaction was revealed.•Seismic load and liquefaction of foundation are important items in the design.
Interest in renewable and clean energy over the past decade has motivated immense research on wind energy. The main issues in design of offshore wind turbines in regions of recent development have ...been aero- and hydro-dynamic loads; however, earthquake is a design concern in seismic areas such as East Asia and Western United states. This paper reviews the state of practice in seismic design of offshore wind turbines. It is demonstrated that wind turbines are in particular vulnerable to vertical earthquake excitation due to their rather high natural frequencies in vertical direction; however, inclusion of the radiation damping could contribute considerably reduce the earthquake loads. Moreover, it is demonstrated how soil nonlinearity could lead to settlement and permanent tilting of offshore wind turbines on caisson foundations or tripods. Using these cases, the paper demonstrates that the design of offshore wind turbines for earthquake loading is driven by performance-based considerations.
•Effect of combined environmental and earthquake loads on offshore wind turbines, highlighting the issue of permanent tilt.•Nonlinear foundation springs with reduced/controlled hysteretic damping for soil-structure interaction analysis.•Rigorous modelling of radiation damping and its role in reduction of vertical seismic response of wind turbines.•Harmonization of earthquake hazard requirements in design of wind turbines.•Review of key issues in earthquake design of offshore wind turbines.
Surface transportation systems are an essential part of urban transportation infrastructure and are susceptible to damage from earthquakes. This damage, along with the lack of prior warning of ...earthquake events, may lead to severe and unexpected disruption of normal traffic patterns, which may seriously impair post-disaster response. Accordingly, it is important to understand the performance of urban transportation systems immediately following an earthquake, to evaluate their capability to support emergency response, e.g., the movement of firefighters, search and rescue teams and medical personnel, and the transportation of injured people to emergency treatment facilities. For this purpose, a scenario-based methodology is developed to model the performance of a transportation network immediately following an earthquake using an agent-based model. The model accounts for the abrupt changes in destination, irrational behavior of drivers in the chaotic aftermath of a severe earthquake, unavailability of traffic information and impairment in traffic capacity due to bridge damage and building debris. An illustration using the road network of Tangshan City, China shows that the method can capture the traffic flow characteristics immediately after an earthquake and can determine the capability of the transportation network to transfer injured people to hospitals. Thus, it can provide rational support for evaluating the performance of the surface transportation system under immediate post-disaster emergency conditions.
This paper presents the results of a study on the dynamic and seismic response of the support structures of three reference Offshore Wind Turbines (OWT) of increasing rated power, founded to the ...seabed through monopile foundations. Thus, the structural behaviour of the NREL 5 MW, IEA Wind 10 MW and IEA Wind 15 MW reference OWTs under seismic input is analysed. To do so, a model based on the aero-hydro-servo-elastic OpenFAST open-software code, modified to include dynamic Soil–Structure Interaction (SSI) and input ground motion, is employed. Dynamic SSI phenomena are incorporated through lumped parameter models fitted to the impedances computed using an advanced boundary elements–finite elements model of the soil–foundation system in which the monopile is discretized as a steel pipe buried in the unbounded seabed. The fore–aft and side-to-side responses of the systems are computed under power production, parked and emergency shutdown operating conditions considering different earthquakes and arrival times. It is found that even low and moderate intensity earthquakes can produce significant increases in the structural demands of large OWTs. There exists a clear tendency for SSI to be beneficial when the size of the OWT increases.
•The dynamic and seismic response of three large offshore wind turbines is studied.•The NREL 5 MW and the new IEA Wind 10 MW and 15 MW reference OWT are studied.•OpenFAST is modified to include soil–structure interaction and seismic input motion.•LPMs are used to incorporate soil–pile impedances from an advanced BE-FE model.•The time of arrival of the earthquake or the operating model are relevant parameters.
Abstract
Magnetorheological elastomer (MRE), as a field-dependent smart material, has been widely applied on base isolation for vibration reduction. However, the MRE isolation system often ...experiences large drift during a strong earthquake, which may cause mechanical failure. Additionally, its performance among the low-frequency range is still limited. To tackle these problems, this paper proposes a hybrid vibration isolation system which is composed of four stiffness softening MRE isolators and a passive ball-screw inerter. A simulation was developed to prove the effectiveness of the hybrid isolation system before the earthquake tests. A scaled three-storey building was developed based on the scaling laws as the isolated objective in earthquake experiments. Besides, a linear quadratic regulation controller was utilised to control the mechanical properties of the hybrid MRE isolation system. Finally, the evaluation experiments of the building under a scaled Kobe earthquake excitation were conducted. The experimental results show that the simulation and the experimental results were in agreement, validating that the hybrid isolation system could provide a better vibration mitigation performance, in the meanwhile, reduce the displacement amplitude of the isolation system.
•A multi-objective stochastic programming model is developed for pre-positioning and distributing emergency supply.•A new multi-objective particle swarm optimization algorithm is proposed to generate ...Pareto-fronts.•A new adaptive strategy based on Pareto-dominance concept is applied to set the inertia weight.•The effects of the equity measure on the facility location and distribution decisions are analysed.
The development of an efficient emergency response plan to provide critical daily supplies to affected people facilitates efficient relief operations. In this study, we propose a multi-objective stochastic programming model for developing an earthquake response plan, which integrates pre-and post-disaster decisions. This three-objective model attempts to maximize the total expected demand coverage, to minimize the total expected cost, and to minimize the difference in the satisfaction rates between nodes. We develop a new multi-objective particle swarm optimization (MOPSO) algorithm to solve this model. Genotype-phenotype-based binary particle swarm optimization (PSO) and continuous PSO are designed to deal with the binary location and other continuous decision variables, respectively. A new strategy is employed to select two types of guides in order to enhance the search ability. Furthermore, a new adaptive inertia weight strategy and two mutation operators are used to ensure that the diversity is sufficient and to regulate the exploration and exploitation capacities, respectively. We present an illustrative real-world case study and some randomly generated instances for computational applications. The results obtained by the proposed MOPSO algorithm were compared with those obtained using a modified time-variant MOPSO, the non-dominated sorting genetic algorithm, strength Pareto evolutionary algorithm, and the exact solution method where possible.
In this study, based on the random-vibration-theory (RVT) methodology, an earthquake response analysis of a nuclear facility with a rigid foundation on rock/soil sites is considered when incoherent ...seismic waves are incident on the system. Using the coherency function of seismic waves, the power spectral density (PSD) matrix for six-degree-of-freedom motions of the rigid foundation is calculated. The stochastic earthquake responses of the soil–structure interaction system are obtained, and the PSD function for the pseudo-acceleration of equipment on one floor of the structure is derived. Peak factors of random vibrations are employed to estimate the spectral acceleration or in-structure response spectrum (ISRS) of the equipment. The accuracy of the proposed RVT methodology is verified for nuclear power plant structures on hard rock, soft rock, and layered soil acted upon by coherent and incoherent seismic waves. Because the ISRS outcomes are found to decline at high frequencies, reduction factors due to incoherency are obtained from the proposed RVT methodology. These factors can be applied to earthquake responses to coherent ground motions to consider the effects of incoherent seismic waves.
•Earthquake responses of structural systems subjected to incoherent seismic waves.•Random-vibration-theory (RVT) methodology for earthquake analysis of structures.•Comparison with the response-history methodology for verification.•Reduction of earthquake responses at high frequencies due to the incoherency.•Reduction factors from the RVT methodology for seismic design of nuclear facilities.
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