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9th european conference on numerical methods in geotechnical engineering, NUMGE 2018

作者： Bourgeois, E. Moreno Regan, O. Colas, A.S. Chatellier, P. Douroux, J.F. Desbordes, A. Université Paris Est IFSTTAR Marne la Vallée France Setec tpi Paris France Université Paris Est IFSTTAR Marne la Vallée France RATP Fontenay sous Bois France

ISBN: (纸本)9781138544468

Most of the Paris subway tunnels comprise a masonry vault built between 1900 and 1960. In order to identify potential cracking areas and to predict the deformations resulting from loads associated to the construction of new infrastructures, RATP and IFSTTAR have developed a constitutive model specifically aimed at representing the main features of the masonry lining. the approach consisted of adapting an existing model combining a homogenization procedure with damage. the differences between the approach adopted and the original model are highlighted. the resulting model makes it possible to account for a global heterogeneous anisotropic elastic behavior including damage. It has been implemented in the finite element code CESAR-LCPC. As a first step, the model has been used to simulate tests, taken from the literature, performed on semicircular masonry vaults. © 2018 Taylor & Francis Group, London, UK.

关键词： Railroads

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numerical evaluation of fragility curves for earthquake liquefaction induced settlements of a levee using gaussian processes 9th

Numerical evaluation of fragility curves for earthquake liqu...

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9th european conference on numerical methods in geotechnical engineering, NUMGE 2018

作者： Lopez-Caballero, F. Laboratoire MSS-Mat CNRS UMR CentraleSupélec Paris-Saclay University France

ISBN: (纸本)9781138544468

the major cause of earthquake damage to an embankment is the liquefaction of the soil foundation that induces ground level deformations. It is well known that the liquefaction appears when the soil loses its shear strength due to the excess of pore water pressure. the aim of this paper is to assess numerically the effect of the liquefaction-induced settlement of the soil foundation on an embankment due to real earthquakes. For this purpose, a 2D Finite Element (FE) model of a levee founded on a layered soil/rock profile was considered. An elastoplastic multi-mechanism model was used to represent the soil behaviour. the crest settlement of the embankment was selected as the quantifiable damage variable of the study. Fragility functions were drawn to give the probability exceedance of some proposed damage levels as function of a seismic severity parameter. However, FE analysis can be expensive due to very large number of simulations needed for an accurate assessment of the system failure behaviour. this problem is addressed by building a Gaussian Process (GP) emulator to represent the output of the expensive FE model. A comparison with the FE reference results suggests that the proposed GP model works well and can be successfully used as a predictive tool to compute the induced damage on the levee. © 2018 Taylor & Francis Group, London.

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Boundary stress distribution in silos filled with granular material 9th

Boundary stress distribution in silos filled with granular m...

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9th european conference on numerical methods in geotechnical engineering, NUMGE 2018

作者： To, P. Sivakugan, N. College of Science and Engineering James Cook University Australia

ISBN: (纸本)9781138544468

Silo, a very popular structure in powder and mining industry, is a vertical container with an open outlet at the bottom and an optional inlet at the top. the design of silo requires a deep under-standing of stress distribution at boundaries in both static and dynamic condition. Prior numerical studies use Finite Element Method or Finite Difference Method which shows an increase of vertical stress before it is leveled out by friction at a shallow depth. this is understandable for continuous media because the settlement caused by vertical stress must stop at some level. Nevertheless, experimental studies show that the vertical stress of the granular and porous media still increases with a constant rate even at a much greater depth. Although the Discrete Element Method (DEM) can simulate granular materials, it has some difficulties in determination of stress distribution because it is based on contact force, not the stress. this paper employs DEM with sphero-polyhedra shapes to simulate the behaviour of granular materials in silos. the stress distribution is calculated as average values. this requires a significant number of particles. therefore, the paper focuses on narrowly graded materials. Some correlation with experimental data has been found. © 2018 Taylor & Francis Group, London.

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Soil parameter identification for excavations: A falsification approach 9th

Soil parameter identification for excavations: A falsificati...

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9th european conference on numerical methods in geotechnical engineering, NUMGE 2018

作者： Ze-Zhou, Wang Huat, Goh Siang Ghee, Koh Chan Smith, Ian F. C. Department of Civil and Environmental Engineering National University of Singapore Singapore ETH Zurich Future Cities Laboratory Singapore-ETH Centre CREATE Singapore Lausanne Switzerland

ISBN: (纸本)9781138544468

Soil-parameter identification is a long-standing topic that has received considerable attention over the years. Traditional identification approaches usually follow the least-squares criteria. these approaches aim to find a single set of parameter values that produces the minimum absolute error between numerical predictions and measurements. However, these approaches have several drawbacks, particularly their inability to accommodate systematic modelling uncertainty. A recent data-interpretation methodology, Error-Domain Model Falsification (EDMF), is used to overcome these drawbacks. A key feature of EDMF is the explicit representation of systematic uncertainties originating from model simplifications. this paper presents the application and adaptation of this methodology in the area of soil parameter-identification. A synthetic excavation case is used as an illustration. Using EDMF, accurate soil properties can be identified with the inclusion of systematic uncertainties, which leads to improved predictions of the excavation performance. the residual minimization approach, however, returns inaccurate soil properties and biased predictions. the present study shows that EDMF offers a promising data-interpretation methodology that can yield multiple sets of admissible parameter values, which in turn help engineers to appreciate and understand the possible variations in soil properties and predictions that are compatible with field measurements. © 2018 Taylor & Francis Group, London, UK.

关键词： Forecasting

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Spudcan installation and post installation behaviour in soft clay: the press-replace method 9th

Spudcan installation and post installation behaviour in soft...

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9th european conference on numerical methods in geotechnical engineering, NUMGE 2018

作者： Ze-Zhou, Wang Huat, Goh Siang Department of Civil and Environmental Engineering National University of Singapore Singapore

ISBN: (纸本)9781138544468

the life cycle of a jack-up spudcan foundation consists of installation, operations and extraction. A proper simulation of the continuous installation process to capture the stress state of the soil can help provide a better understanding of spudcan-soil interaction response during the subsequent operational stage. this paper presents the application of the Press-Replace Method (PRM) to simulate (i) the continuous installation of a jack-up spudcan foundation into a single layer seabed using an undrained effective stress analysis and (ii) its post-installation consolidation behaviour during the operational stage. the simulated penetration resistance and excess pore pressures generated during the installation stage, and their subsequent pore pressure dissipation during the operational stage, are validated through comparisons with published data. In general, the PRM is able to replicate experimental observations quite well. A significant advantage of this technique is that it allows a better-integrated analysis of the spudcan-soil interaction mechanism incorporating both the undrained response during the installation process and the consolidation response during the operational phase. With the PRM, the use of an additional computer script to map the stress state at the end of installation stage to a separate file for consolidation analysis, which may be necessary for some techniques, is no longer needed. therefore, a dual stage analysis can be effectively simplified to a one-step analysis with minimum user intervention. © 2018 Taylor & Francis Group, London, UK.

关键词： Installation

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A numerical solution for addressing overturning phenomena of heritage assets 11

A numerical solution for addressing overturning phenomena of...

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11th National conference on Earthquake engineering 2018: Integrating Science, engineering, and Policy, NCEE 2018

作者： Domaneschi, M. Zamani Noori, A. Marasco, S. Cardoni, A. Cimellaro, G.P. Dept. of Civil Structural and Geotechnical Engineering Politecnico di Torino 10129 Italy Dept. of Civil and Environmental Engineering University of California BerkeleyCA94720 United States

ISBN: (纸本)9781510873254

Historical heritage represent a crucial aspect for societies and therefore it should be preserved from natural disasters such as earthquake. Base isolation systems are widely used to mitigate the horizontal effects of strong ground motions on important buildings and bridges, but there are also interesting applications on statues. However, such systems are characterized by properties that are quite different from the ones that belong to traditional civil structures. For this reason, national and international regulations are not exhaustive and actual dynamics of the system should be studied through numerical and experimental methods. Starting from analytical formulations, the paper investigates the sliding and rocking motion in details, being the typical one of statues under seismic loads. the presented numerical model describes the problem and is an alternative to the analytical formulation to perform several analyses automatically. In addition, it allows running parametric analyses to assess the influence of various parameters, such as eccentricity, stiffness, mass, geometric ratios, etc. Future work is geared to validate the numerical model trough performing experimental tests on shaking table. Copyright © NCEE 2018: Integrating Science, engineering, and *** rights reserved.

关键词： numerical models

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Arching of granular flow under loading in silos 9th

Arching of granular flow under loading in silos

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9th european conference on numerical methods in geotechnical engineering, NUMGE 2018

作者： To, P. Sivakugan, N. College of Science and Engineering James Cook University Australia

ISBN: (纸本)9781138544468

Sublevel scheme is a major type of underground mining. At each sublevel, mine is blasted to form a silo, so that ore can be extracted from the bottom outlet of the silo. Due to the extraction, ground surface will have some significant subsidence, which can influence nearby infrastructure. To avoid this impact, a filling material might be stopped from upper sublevel during the extraction. this additional load creates spatial constraints for the granular flow and might stimulate the arching of this granular material. the research employs Discrete Element Method to simulate granular flow in silos under general vertical loadings. Particles are generated by Voronoi tessellation at a given porosity. the sample is shaken lightly so that particles can achieve a more random position and neutral contact. After that, they are released under gravity to form a granular flow. A parameter study is undertaken to find the condition of arching. A force is assigned to a top plane to simulate a top load, which increase stresses in force chains. the research draws out the influence of the geometry and top loads on arching probability in a silo. © 2018 Taylor & Francis Group, London.

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Localization of near-field sources based on linear prediction and oblique projection operator

Localization of near-field sources based on linear predictio...

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作者： Zuo, Weiliang Xin, Jingmin Liu, Wenyi Zheng, Nanning Ohmori, Hiromitsu Sano, Akira Institute of Artificial Intelligence and Robotics National Engineering Laboratory for Visual Information Processing and Applications School of Artificial Intelligence Xi'An Jiaotong University Xi'an710049 China Department of System Design Engineering Keio University Yokohama223-8522 Japan

this paper investigates the localization of multiple near-field narrowband sources with a symmetric uniform linear array, and a new linear prediction approach based on the truncated singular value decomposition (LPATS) is proposed by taking an advantage of the anti-diagonal elements of the noiseless array covariance matrix. However, when the number of array snapshots is not sufficiently large enough, the 'saturation behavior' is usually encountered in most of the existing localization methods for the near-field sources, where the estimation errors of the estimated directions-of-arrival (DOAs) and ranges cannot decrease with the signal-to-noise ratio. In this paper, an oblique projection based alternating iterative scheme is presented to improve the accuracy of the estimated location parameters. Furthermore, the statistical analysis of the proposed LPATS is studied, and the asymptotic mean-square-error expressions of the estimation errors are derived for the DOAs and ranges. the effectiveness and the theoretical analysis of the proposed LPATS are verified through numerical examples, and the simulation results show that the LPATS provides good estimation performance for both the DOAs and ranges compared to some existing methods. © 1991-2012 IEEE.

关键词： Mean square error

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Multi-disciplinary optimization in aeronautical engineering

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PROCEEDINGS OF thE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE engineering 2017年第12期231卷 2305-2313页

作者： Goetzendorf-Grabowski, Tomasz Warsaw Univ Technol Inst Aeronaut & Appl Mech Fac Power & Aeronaut Engn Warsaw Poland

Nowadays, optimization is a very popular tool used to improve existing projects. the optimization covers different disciplines by linking them into multidisciplinary process of design. Existing software tools allow to very effectively solve particular problems giving high quality solutions which were previously very hard to achieve. Aeronautical engineering is a domain/field which links many disciplines: aerodynamics, stability, control, structural analysis, materials, propulsion systems, avionics, etc. therefore, the multidisciplinary optimization results in very significant progress not only in aircraft design but also in air transport, which links technical aspects with economical questions. the paper presents selected aspects of using the multidisciplinary optimization in aeronautical engineering with special focus on multidisciplinary aircraft design.

关键词： Optimization aircraft design stability analysis aerodynamics numerical methods software architectures

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Out-of-plane dynamic response of a tuff masonry wall: Shaking table testing and numerical simulation 6

Out-of-plane dynamic response of a tuff masonry wall: Shakin...

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6th International conference on Computational methods in Structural Dynamics and Earthquake engineering, COMPDYN 2017

作者： Addessi, Daniela Cappelli, Enrico Gatta, Cristina Vestroni, Fabrizio Department of Structural and Geotechnical Engineering Sapienza University of Rome Via Eudossiana 18 Rome00184 Italy

ISBN: (纸本)9786188284418

the out-of-plane dynamic response of a masonry element is investigated, both experimentally and numerically. the results of shaking table tests on a tuff masonry wall, subjected to harmonic acceleration histories, are presented. An isotropic nonlocal damage-plastic model, accounting for the masonry strength-stiffness degrading and hysteresis mechanisms, is introduced in a finite element procedure to numerically describe the masonry structural response. A simplified scheme is analysed, where the wall is completely restrained at the base and free at the top. the measured top displacement history is compared with that numerically evaluated, obtaining a satisfactory agreement. Moreover, the effects of the onset and evolution of the degrading mechanisms in the masonry wall are highlighted.

关键词： Dynamic response

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