scholarly journals An Improved Numerical Model of Shield Tunnel with Double Lining and Its Applications

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Qi-xiang Yan ◽  
Chao-fan Yao ◽  
Wen-bo Yang ◽  
Chuan He ◽  
Ping Geng
Keyword(s):  
Numerical Model ◽  
Contact Surface ◽  
Abrupt Change ◽  
Numerical Models ◽  
Bending Moment ◽  
Shield Tunnel ◽  
Similar Model ◽  
Secondary Lining ◽  
Improved Model ◽  
Node Displacement

Based on the existing numerical models of shield tunnel with double lining, an improved numerical model is developed and its rationality is verified by a similar model test. In the improved numerical model, lining, joint, and junction surface, respectively, are simulated by beam, spring, and a combination of compression bar and spring. Through the comparison of the numerical analysis results of the improved model and existing models, it turns out that the defects or problems in the existing numerical models are resolved; tension appearance on the contact surface and junction surface and the abrupt change of bending moment in linings are solved in the improved model because the compression bar element and the coupling technology of node displacement in the junction surface is applied. Therefore, the improved numerical model could be applied to analyze double lining with waterproof on the junction surface and separation of the junction surface under an unfavorable load. In this paper, the parameter formulas of element stiffness, applicable to the junction surface and contact surface of double lining, are given definitely, and the influence of the element amount of junction surface on the analysis results is discussed. Based on the improved numerical model, the mechanical behavior of the double lining of the Huangpu River Tunnel in China is studied, and some conclusions are obtained as follows. (1) The thickness increase of the double lining will clearly increase its bending moment, but it has little influence on its axial force. (2) The allocation proportion of the bending moment between the segment lining and secondary lining has no linear relationship with the ratio of the lining thickness.

scholarly journals Numerical analysis of reducing tunneling effect on viaduct piles foundation by jet grouted wall

2021 ◽  
Vol 15 (1) ◽  
pp. 75-86
Author(s):  
Kamel Asker ◽  
Mohmed Tarek Fouad ◽  
Mohamed Bahr ◽  
Ahmed El-Attar
Keyword(s):  
Numerical Model ◽  
Interaction Mechanism ◽  
Back Analysis ◽  
Bending Moment ◽  
Pile Group ◽  
Tunneling Effect ◽  
Shield Tunnel ◽  
Pile Groups ◽  
Perfectly Plastic ◽  
Jet Grouting

Purpose. The target of this study is divided into two parts. The first part is concerned with capability of numerical model to simulate the tunneling process. The second part is related to studying the interaction mechanism between the tunnel, protection technique, and soil. This study themes are investigated by analyzing different protection technique configuration, considering different stiffness of the grouted wall, and applying different interface coefficient between the wall and the soil. Methods. The method used in this study to check the accuracy of the proposed numerical model is 4-D ABAQUS program. The typical excavation of a tunnel is simulated step by step with an assumed rate of tunnel advancement (0.5 to 1.5 m/hr). The soil material utilized in this model is elastic perfectly plastic (the Mohr-Сoulomb criterion), while elastic material is modeled as solid element (S4R) adopted for lining, grouting, filling gaps, shielding, constructing piles, and jet grouted wall. Findings. Results showed that the closer jet grouting to the tunnel with embedded length of 1.5 times tunnel diameter, the better effect on reducing the lateral deformation and bending moment generated on piles. Otherwise, increasing wall thickness more than double grouted column diameter would not affect its shielding efficiency. Furthermore, either increasing or decreasing friction coefficient even if rough between the grouted wall and soil had no effect on the pile behavior. Additionally, applying Mohr-Coulomb criteria for grouted wall with high stiffness allowed realistic response of the pile group. Originality.Capability of the proposed model is verified by back analysis of Changsha Subway Line 1 project, where the shield tunnel would be constructed near existing pile groups of L off-ramp of the Xinzhong Road viaduct. Practical implications. Increasing grouted wall configuration is more effective than mechanical properties or its interface coefficient with surrounded soil in mitigating tunneling effect on nearby piles. Keywords: tunneling, jet grouting, gield measurements, ABAQUS, Changsha Subway Line 1

TEHD Lubrication of Mechanical Face Seals in Stable Tracking Mode: Part 1—Numerical Model and Experiments

2003 ◽  
Vol 125 (3) ◽  
pp. 608-616 ◽  
Author(s):  
Noe¨l Brunetie`re ◽  
Bernard Tournerie ◽  
Jean Fre^ne
Keyword(s):  
Numerical Model ◽  
Thermal Behavior ◽  
Stokes Equations ◽  
Numerical Models ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Computer Code ◽  
Three Dimensional Model ◽  
Face Seals ◽  
Improved Model

After a short presentation of state-of-the-art experimental studies on the thermal behavior of non-contacting face seals, the literature about numerical models for thermal effects is investigated. Next, the geometry, kinematics and dynamics of a steady state three-dimensional model are developed. Simplified Navier-Stokes equations, a generalized Reynolds equation and an energy equation with proper boundary conditions are established for flow regimes, varying from laminar to turbulent. The numerical computer code for solving the governing equations is presented and representative results are shown. It is demonstrated that face distortions strongly modify the seals’ thermal behavior. An original test rig has been developed in order to ensure full fluid film conditions. This apparatus and the experimental procedure are described. The ability of the numerical model to simulate real configurations is also illustrated. Theoretical and experimental results are in good agreement. Yet an improved model of heat transfer on boundaries is still needed.

scholarly journals Monopile foundation under lateral cyclic action. Numerical modelling

2019 ◽  
Vol 85 ◽  
pp. 08008
Author(s):  
Andrei Valentin Drăguşin ◽  
Loretta Batali
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Numerical Models ◽  
Lateral Displacement ◽  
Large Diameter ◽  
Bending Moment ◽  
Small Scale ◽  
Design Elements ◽  
Pile Diameter ◽  
Starting Point

Foundation of an off-shore wind mill is submitted throughout its existence to a very high number of cycles coming from lateral actions such as waves or wind. These actions have a strong aleatory character which makes them very hard to predict, quantify and analyse. Therefore, in current design practice, these actions are being considered as pseudo-static force at their maximum values, with the cyclic phenomenon being neglected. This can lead to an inappropriate design of the foundation, which could have a negative impact on the future structure. This type of structure is generally built on a monopile foundation, a single, large diameter pile, which will be submitted to thousands lateral cycles. The pile diameter plays an important role, influencing the behaviour of the entire structure. Centrifuge experiments on small-scale models are very useful to study such complex problem as piles under lateral cyclic loads. Several researches have been carried out internationally and the results can be used for calibrating numerical models, which is obviously a more accessible method of design, compared to an experimental approach. This has been precisely the starting point of this paper. The purpose of the present paper is to analyse the influence of the pile diameter, by using a FEM a numerical model, previously calibrated based on centrifuge experiments carried out at IFSTTAR Nantes. For the numerical modelling the software CESAR-LCPC 3D has been used. Several pile diameters have been considered, as follows: 0.72 m, 1.08 m, 1.44 m, 1.80 m, 2.16 m and 2.52 m. The results are taking into account the lateral displacement and bending moment of the piles, for static and cyclic loading. The main objective was to determine the stabilisation rate of the most important two design elements (pile head displacement and maximum bending moment) after “n” cycles and to eventually conclude the diameter value beyond which no more influence of cycles is recorded. The numerical model considered 15 cycles and the results have been used extrapolated in order to determine the cycle “n” of stabilisation (for displacement and bending moment).

scholarly journals Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 14
Author(s):  
Gianluca Zitti ◽  
Nico Novelli ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
Offshore Structures ◽  
Fish Farm ◽  
Maximum Displacement ◽  
Drag Forces ◽  
Real Size ◽  
Lift And Drag ◽  
Mesh Grid

Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.

scholarly journals Development of Detailed FE Numerical Models for Assessing the Replacement of Metal with Composite Materials Applied to an Executive Aircraft Wing

Aerospace ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 178
Author(s):  
Valerio Acanfora ◽  
Roberto Petillo ◽  
Salvatore Incognito ◽  
Gerardo Mario Mirra ◽  
Aniello Riccio
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Numerical Model ◽  
Numerical Models ◽  
Structural Performance ◽  
Aircraft Wing ◽  
Resin Infusion ◽  
Effectiveness Analysis ◽  
Liquid Resin Infusion ◽  
Process Constraints

This work provides a feasibility and effectiveness analysis, through numerical investigation, of metal replacement of primary components with composite material for an executive aircraft wing. In particular, benefits and disadvantages of replacing metal, usually adopted to manufacture this structural component, with composite material are explored. To accomplish this task, a detailed FEM numerical model of the composite aircraft wing was deployed by taking into account process constraints related to Liquid Resin Infusion, which was selected as the preferred manufacturing technique to fabricate the wing. We obtained a geometric and material layup definition for the CFRP components of the wing, which demonstrated that the replacement of the metal elements with composite materials did not affect the structural performance and can guarantee a substantial advantage for the structure in terms of weight reduction when compared to the equivalent metallic configuration, even for existing executive wing configurations.

A physically-based soil surface model and its combination with numerical models for predicting bare-soil evaporation rates

2021 ◽  
Author(s):  
Xiaocheng Liu ◽  
Chenming Zhang ◽  
Yue Liu ◽  
David Lockington ◽  
Ling Li
Keyword(s):  
Numerical Model ◽  
Surface Resistance ◽  
Numerical Models ◽  
Soil Column ◽  
Soil Surface ◽  
Bare Soil ◽  
Water Vapor Transport ◽  
Surface Model ◽  
Vapor Flow ◽  
Physically Based

<p>Estimation of evaporation rates from soils is significant for environmental, hydrological, and agricultural purposes. Modeling of the soil surface resistance is essential to estimate the evaporation rates from bare soil. Empirical surface resistance models may cause large deviations when applied to different soils. A physically-based soil surface model is developed to calculate the surface resistance, which can consider evaporation on the soil surface when soil is fully saturated and the vapor flow below the soil surface after dry layer forming on the top. Furthermore, this physically-based expression of the surface resistance is added into a numerical model that considers the liquid water transport, water vapor transport, and heat transport during evaporation. The simulation results are in good agreement with the results from six soil column drying experiments.  This numerical model can be applied to predict or estimate the evaporation rate of different soil and saturation at different depths during evaporation.</p>

scholarly journals Timber frame houses resistant to dynamic loads - seismic analysis

2018 ◽  
Vol 219 ◽  
pp. 01001
Author(s):  
Marcin Szczepański ◽  
Wojciech Migda
Keyword(s):  
Polyurethane Foam ◽  
Considerable Increase ◽  
Seismic Analysis ◽  
Numerical Models ◽  
Mineral Wool ◽  
Seismic Excitations ◽  
Timber Frame ◽  
Frame Building ◽  
Frame Buildings ◽  
Node Displacement

The aim of the article is to present results of seismic analysis results of two real-sized timber frame buildings subjected to seismic excitations. The first model was insulated with mineral wool, the second one with polyurethane foam. Technology and specifications involved in both models construction is based on the previously conducted experimental research on timber frame houses, including wall panels tests, wall numerical models and study on material properties and precisely reflect results of the those research. During the seismic analysis reference node located in buildings were selected. In selected node displacement values were measured and compared between two analyzed models. The results of the numerical analysis presented in the article indicate that the application of polyurethane foam for a skeleton filling of the timber-frame building leads to the increase in stiffness as well as damping of the whole structure, which results in a considerable increase in the seismic resistance of the structure.

The Research of Energy Conversion and Heat Transfer in the Ceramic Foams of Solar Energy Converter

2011 ◽  
Author(s):  
Yangbo Deng ◽  
Fengmin Su ◽  
Chunji Yan
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Solar Radiation ◽  
Solar Energy ◽  
Numerical Models ◽  
Air Flow ◽  
Energy Converter ◽  
Ceramic Foams ◽  
Numerical Studies ◽  
Flow Through

The solar energy converter in Concentrated Solar Power (CSP) system, applies the solid frame structure of the ceramic foams to receive the concentrated solar radiation, convert it into thermal energy, and heat the air flow through the ceramic foams by convection heat transfer. In this paper, first, the pressure drops in the studied ceramic foams were measured under all kinds of flow condition. Based on the experimental results, an empirical numerical model was built for the air flow through ceramic foams. Second, a 3-D numerical model was built, for the receiving and conversion of the solar energy in the ceramic foams of the solar energy converter. Third, applying two aforementioned numerical models, the numerical studies of the thermal performance were carried out, for the solar energy converter filled with the ceramic foams, and results show that the structure parameters of the ceramic foams, the effective reflective area and the solar radiation intensity of the solar concentrator, have direct impacts on the absorptivity and conversion efficiency of the solar energy in the solar energy converter. And the results of the numerical studies are found to be in reasonable agreement with the experimental measurements. This paper will provide a reference for the design and manufacture of the solar energy converter with the ceramic foams.

scholarly journals Influence of foundation settlements in load redistribution on columns in a monitoring construction - Case Study

2010 ◽  
Vol 3 (3) ◽  
pp. 346-356 ◽  
Author(s):  
G. Savaris ◽  
P. H. Hallak ◽  
P. C. A. Maia
Keyword(s):  
Numerical Analysis ◽  
Numerical Model ◽  
Finite Elements ◽  
Load Distribution ◽  
Numerical Models ◽  
Normal Load ◽  
Finite Elements Method ◽  
Load Redistribution

The objective of this article is to present the results obtained in a study on the interaction between the behavior of the structure and the foundation settlements and verify the influence of normal load distribution on the columns. In this mechanism, known as structure soil interaction (SSI), as the building is constructed, a transfer of loads occurs from the columns which tend to settle more to those that tend to settle less. The study was conducted in a building which had its settlements monitored from the beginning of construction. For this purpose, a linear tridimensional numerical model was constructed and numerical analysis was performed, using the finite elements method. In these analyses, numerical models corre- sponding to the execution of each floor were used, considering the settlements measured in each stage of the construction. The results of analy- ses showed that the effect of SSI are significant for calculating the normal efforts on the columns, particularly on those located in the first floors.

scholarly journals THE USE OF ARRAY PROCESSORS FOR NUMERICAL MODELLING OF TIDAL ESTUARY DYNAMICS

1980 ◽  
Vol 1 (17) ◽  
pp. 142
Author(s):  
D. Prandle ◽  
E.R. Funke ◽  
N.L. Crookshank ◽  
R. Renner
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Hybrid Model ◽  
Numerical Models ◽  
Computer Time ◽  
Scale Model ◽  
Hybrid Modelling ◽  
Tidal Propagation ◽  
Physical Scale ◽  
Array Processors

The use of array processors for the numerical modelling of estuarine systems is discussed here in the context of "hybrid modelling", however, it is shown that array processors may be used to advantage in independent numerical simulations. Hybrid modelling of tidal estuaries was first introduced by fiolz (1977) and later by Funke and Crookshank (1978). In a hybrid model, tidal propagation in an estuary is simulated by dynamically linking an hydraulic (or physical) scale model of part of the estuary to a numerical model of the remaining part in a manner such that a free interchange of flow occurs at the interface(s). Typically, the elevation of the water surface at the boundary of the scale model is measured and transmitted to the numerical model. In return, the flow computed at the boundary of the numerical model is fed directly into the scale model. This approach enables the extent of the scale model to be limited to the area of immediate interest (or to that area where flow conditions are such that they can be most accurately simulated by a scale model). In addition, since the region simulated by the numerical model can be extended almost indefinitely, the problems of spurious reflections from downstream boundaries can be eliminated. In normal use, numerical models are evaluated on the basis of computing requirements, cost and accuracy. The computer time required to simulate one tide cycle is, in itself, seldom of interest except in so far as it affects the above criteria. However in hybrid modelling this parameter is often paramount since concurrent operation of the numerical and scale models requires that the former must keep pace with the latter. The earlier hybrid model of the St. Lawrence (Funke and Crookshank, 1978) involved a one-dimensional numerical model of the upstream regions of the river. However, future applications are likely to involve extensive two-dimensional numerical simulation.

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