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geotechnical challenges in very high speed railway tracks. the numerical modelling of critical speed issues 9th

9th european conference on numerical methods in geotechnical engineering (NUMGE)

作者： Colaco, A. Alves Costa, P. Univ Porto Construct FEUP Porto Portugal

ISBN: (纸本)9780429446924;9781138332034

Recent railway tracks are being designed for traffic speed larger than 350 km/h. this amazing increase of the traffic speed leads to new geotechnical challenges, since the train speed can achieve values close to the wave propagation velocity in the ground, giving rise to the so called "critical speed problem". the present paper approaches this problem focusing on geotechnical engineering. the departing point is the theoretical formulation of the critical speed problem of a moving load on the surface of an elastic solid. From the usage of 2.5D detailed models it was possible to understand the influence of the embankment and of slab track properties on the critical speed.

关键词： geotechnical engineering

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Consideration of numerical methods in next generation Eurocode 7 (EN 1997)-current state of the amendment 9th

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9th european conference on numerical methods in geotechnical engineering (NUMGE)

作者： Lees, A. S. Walter, H. Tensar Int Nicosia Cyprus Geofem Ltd Nicosia Cyprus HTLuVA Salzburg Salzburg Austria

ISBN: (纸本)9780429446924;9781138332034

According to Mandate 515 of the european Commission "Mandate for amending existing Eurocodes and extending the scope of structural Eurocodes" and the response of CEN/TC250 "Towards a second generation of EN Eurocodes" Eurocode 7 should be extended, among other issues, to cover numerical methods in more detail. Among the tasks listed are: "Establish clear rules for using advanced numerical methods in day-to-day practice for inclusion in EN 1997-1. Such rules have been regularly sought during stakeholder feedback. this work would make use of the background research being undertaken by SC7/EG4. (...)" Currently the first part of EN 1997, EN 1997-1, is being redrafted. It will contain general aspects of geotechnical design, including sections about "Basis of geotechnical design", "geotechnical Analysis", "Ultimate limit states" etc. the third and, expected to be, final draft will be available in May 2018. this paper gives an overview over the goals of the updated version of EN 1997 and the steps and organisation of its development. the section "geotechnical analysis" - with focus on the subsection "numerical methods" - will be presented in more detail. For the verification of ultimate limit states a dual factoring approach will be recommended, requiring two analyses with different combinations of partial safety factors. Among other recommendations, the need for validation of the models will be highlighted with the recommended level of validation depending on the geotechnical category. the updated EN 1997-1 will be open to reliabilitybased analyses.

关键词： numerical methods

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Ground surface settlement analysis of shield tunneling under spatial variability of multiple geotechnical parameters

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HELIYON 2019年第9期5卷 e02495-e02495页

作者： Hu, Baolin Wang, Changhong Shanghai Univ Dept Civil Engn 333 Nanchen Rd Shanghai 200444 Peoples R China

this paper presents an efficient method of shield tunneling reliability analysis using spatial random fields. We introduced two stochastic methods into numerical simulation. the first one computes the maximal ground surface settlement using classical statistics, in which the response surface method is utilized to calculate the failure probability by first-order second moment. Cohesion, internal friction angle, Young's modulus and mechanical model factor are considered as random variables. the second method is the spatial random fields of aforementioned three key geotechnical parameters. Using these two methods, similar multiple soil layers are converted into a stationary random field by local regression as the first step, and then the process is followed by the spatially conditional discretization of multivariate. Failure probability of maximal ground surface settlement is calculated by a subset Monte-Carlo Algorithm. this approach is applied into the four-overlapping shield tunnels of the 5th and 6th metro lines intersecting at Huanhu W Rd station, Tianjin China. the failure analysis results indicated that classical statistics of geotechnical parameters showing higher variability than spatial random fields, which substantially support the complex shield tunneling project.

关键词： Civil engineering Structural engineering geotechnical parameter Ground surface settlement Reliability index Spatial variability Stochastic simulation Risk analysis Soil engineering Construction engineering Foundation engineering Computer-aided engineering

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A new online Bayesian approach for the joint estimation of state and input forces using response-only measurements 13

A new online Bayesian approach for the joint estimation of s...

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13th International conference on Applications of Statistics and Probability in Civil engineering, ICASP 2019

作者： Teymouri, Daniz Sedehi, Omid Katafygiotis, Lambros S. Papadimitriou, Costas Dept. of Civil and Environmental Engineering Hong Kong University of Science and Technology Hong Kong Department of Civil Engineering Sharif University of Technology Tehran Iran Dept. of Mechanical Engineering University of Thessaly Volos Greece

In this paper, a recursive Bayesian-filtering technique is presented for the joint estimation of the state and input forces. By introducing new prior distributions for the input forces, the direct transmission of the input into the state is eliminated, which allows removing low-frequency error components from the predictions and estimations. Eliminating such errors is of practical significance to the emerging fatigue monitoring methodologies. Furthermore, this new technique does not require a priori knowledge of the input covariance matrix and provides a powerful method to update the noise covariance matrices in a real-time manner. the performance of this algorithm is demonstrated using one numerical example and compared it with the state-of-the-art algorithms. Contrary to the present methods which often produce unreliable and inaccurate estimations, the proposed method provides remarkably accurate estimations for both the state and input. © 13th International conference on Applications of Statistics and Probability in Civil engineering, ICASP 2019. All rights reserved.

关键词： Covariance matrix

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Assessment of measures to mitigate traffic induced vibrations by means of advanced validated 3D-Finite Element Analyses 9th

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9th european conference on numerical methods in geotechnical engineering (NUMGE)

作者： Meier, T. Walther, F. BAUGRUND DRESDEN Ingenieurgesell mbH Dresden Germany Landesamt Strassenbau & Verkehr Sachsen Dresden Germany

ISBN: (纸本)9780429446924;9781138332034

As part of environmental considerations vibrations caused by traffic infrastructure are of in-creasing importance. In this context there was for example an EU research and development project called RIVAS (Railway Induced Vibration Abatement Solutions). Together with Keller Holding, Offenbach, Germany as one of the members of this project, BAUGRUND DRESDEN together with the geotechnical Institute of the Technical University of Dresden conducted large-scale field tests and numerical investigations, to firstly demonstrate the applicability and effectiveness of an installation method developed by Keller in conjunction with available damping materials and to validate numerical models, such that they can be used in practice for feasibility studies and design purposes. these FE based analyses are described in the paper at hand together with an application example where the vibrations induced by train traffic are modelled by means of actually moving loads.

关键词： numerical methods

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A cost-effective retrofitting technique for URM buildings based on steel encirclements in openings: A case study 7

A cost-effective retrofitting technique for URM buildings ba...

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7th International conference on Computational methods in Structural Dynamics and Earthquake engineering, COMPDYN 2019

作者： Segovia-Verjel, M.L. Justo-Moscardó, E. Morales-Esteban, A. Requena-García-Cruz, M.V. Romero-Sánchez, E. de-Miguel-Rodríguez, J. Estêvão, J.M.C. Department of Building Structures and Geotechnical Engineering University of Seville Spain Av. Reina Mercedes 2 Seville41012 Spain Department of Civil Engineering ISE University of Algarve Faro Portugal Campus da Penha Faro8005-139 Portugal

ISBN: (纸本)9786188284456

A project named PERSISTAH is being developed to study the seismic vulnerability of primary schools in Huelva (Spain) and the Algarve (Portugal). this area has a moderate seismicity but this is affected by a nearby area where earthquakes of large magnitude (Mw≥6) and long-return periods happen. the seismic vulnerability of URM (UnReinforced Masonry) buildings has been observed and analysed in the last decades. the seismic retrofitting of these buildings is required in order to improve their seismic behaviour. Many retrofitting techniques have been developed for that purpose, most of them very complicated and expensive. therefore, these are not appropriate to retrofit a large number of buildings. this is especially relevant in areas of moderate seismicity where the cost-efficiency ratio must be carefully considered. the aim of this paper has been to develop a simple, effective and affordable technique to retrofit these buildings. these buildings are characterised by numerous openings which causes a great weakness in the URM walls. then, a technique that consists in installing a steel encirclement or a grille in the openings of the walls has been proposed. this is a specific retrofitting technique for URM walls since this technique substantially improves the seismic capacity of these structures. To test the technique a case study is proposed. the building under study is a primary school located in Huelva and built in 1961. Results have shown that the capacity of the building is notably increased. Also, the performance point and the damage level of the structure are decreased. © 2019 the authors.

关键词： Retrofitting

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numerical analysis of a foundation of a cooling tower in difficult geotechnical conditions 9th

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9th european conference on numerical methods in geotechnical engineering (NUMGE)

作者： Bogusz, W. Kociniak, M. Inst Tech Budowlanej Warsaw Poland BEROA Deutschland GmbH Ratingen Germany

ISBN: (纸本)9780429446924;9781138332034

Eurocode 7 offers general guidance on design of different foundation types and recognizes that foundations cannot be always considered in isolation from the structure. When a significant potential for stress redistribution exists, the exceedance of geotechnical ultimate limit state may become highly unlikely. However, it is often the geotechnical serviceability that guides the design as it may lead to a structural failure. the paper presents a case study with the results of a numerical analysis performed for a cooling tower of a conventional power plant, located in an area characterized by difficult geotechnical conditions. Firstly, a prediction of the settlement distribution has been conducted to assess the serviceability limit state and the behavior of the foundation. then, a detailed distribution of moduli of subgrade reaction has been proposed for structural analysis. the measurements of vertical displacements of the foundation, conducted during the construction, validated the assumptions of the design.

关键词： Fracture mechanics

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numerical modelling of limit load increase due to shear band enhancement 9th

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9th european conference on numerical methods in geotechnical engineering (NUMGE)

作者： Seitz, K. -F. Grabe, J. Hamburg Univ Technol Inst Geotech Engn & Construct Management Hamburg Germany

ISBN: (纸本)9780429446924;9781138332034

Strengthening of just the shear bands is a patented idea to prevent a critical failure mechanism in order to increase the capacity of a geotechnical system with a minimum of material. numerical modelling is used to examine this proposed method for limit load increase. Two basic geotechnical systems are analysed using OptumG2 for finite element limit analysis (fela): a shallow foundation with bearing failure and a retaining wall with horizontal wall movement resulting in the active earth wedge. An automated procedure identifies and enhances the shear band using a coupling of OptumG2 with MATLAB. the fela is performed with OptumG2 and run from a MATLAB script, which identifies the shear band based on the simulation result, sets the area of shear band enhancement and reruns the fela. the numerical simulations show that the shear band enhancement leads to a capacity increase for a simple geotechnical system.

关键词： Shear bands

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numerical analysis of an unsymmetrical railcar unloading pit and connection trench 9th

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9th european conference on numerical methods in geotechnical engineering (NUMGE)

作者： Pisco, G. Fartaria, C. Tomasio, R. Costa, J. Azevedo, J. JETsj Geotecnia Lisbon Portugal TECNASOL Fundacoes & Geotecnia Lisbon Portugal

ISBN: (纸本)9780429446924;9781138332034

A numerical analysis was performed simulating the deep excavation and dewatering effects on retaining walls of an unsymmetrical railcar unloading pit and trench. With a depth of 22 meters and an internal diameter of 45 meters the circular pit has a 12 meters width connecting with the trench, which is non collinear with the pit center. A 3D Finite Element Model using PLAXIS software was conducted in order to access both general and local effects in the design of the pit structural elements, due to singularities introduced by the trench opening on the west side of the pit wall and the trench excavation. Both geotechnical and hydrogeological characteristics of site were considered as well as the main construction stages covering the excavation sequence and the groundwater flow analysis.

关键词： Unloading

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numerical modelling strategy to accurately assess lining stresses in mechanized tunneling 9th

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9th european conference on numerical methods in geotechnical engineering (NUMGE)

作者： de Lillis, A. De Gori, V. Miliziano, S. Sapienza Univ Rome Dept Struct & Geotech Engn Rome Italy

ISBN: (纸本)9780429446924;9781138332034

the paper presents a 3-D numerical strategy developed to accurately simulate the soil-shield and the soil-grout-lining interaction processes associated with the gap closure in mechanized tunneling. the problem is particularly relevant for the structural design of pre-cast lining of very deep tunnels subjected to high stresses. the numerical model works in large strain mode and simulates the main features of the excavation and construction processes including face pressure, cutterhead overcut, shield conicity, annular tail void grouting and time-dependent hardening of the grout, installation of the lining inside the shield and jacks' forces. the proposed approach overcomes in a very simple and effective manner the numerical inaccuracies associated to the erroneous shape of the excavation profile numerically obtained due to non-symmetric pre-convergences.

关键词： numerical models

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