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Three-dimensional finite difference analysis of shallow sprayed concrete tunnels crossing a reverse fault

Masoud RANJBARNIA, Milad ZAHERI, Daniel DIAS

《结构与土木工程前沿(英文)》 2020年 第14卷 第4期   页码 998-1011 doi: 10.1007/s11709-020-0621-8

摘要: Urban tunnels crossing faults are always at the risk of severe damages. In this paper, the effects of a reverse and a normal fault movement on a transversely crossing shallow shotcreted tunnel are investigated by 3D finite difference analysis. After verifying the accuracy of the numerical simulation predictions with the centrifuge physical model results, a parametric study is then conducted. That is, the effects of various parameters such as the sprayed concrete thickness, the geo-mechanical properties of soil, the tunnel depth, and the fault plane dip angle are studied on the displacements of the ground surface and the tunnel structure, and on the plastic strains of the soil mass around tunnel. The results of each case of reverse and normal faulting are independently discussed and then compared with each other. It is obtained that deeper tunnels show greater displacements for both types of faulting.

关键词: urban tunnel     sprayed concrete     reverse fault     normal fault     finite difference analysis    

Application of random set method in a deep excavation: based on a case study in Tehran cemented alluvium

Arash SEKHAVATIAN, Asskar Janalizadeh CHOOBBASTI

《结构与土木工程前沿(英文)》 2019年 第13卷 第1期   页码 66-80 doi: 10.1007/s11709-018-0461-y

摘要: The design of high-rise buildings often necessitates ground excavation, where buildings are in close proximity to the construction, thus there is a potential for damage to these structures. This paper studies an efficient user-friendly framework for dealing with uncertainties in a deep excavation in layers of cemented coarse grained soil located in Tehran, Iran by non-deterministic Random Set (RS) method. In order to enhance the acceptability of the method among engineers, a pertinent code was written in FISH language of FLAC2D software which enables the designers to run all simulations simultaneously, without cumbersome procedure of changing input variables in every individual analysis. This could drastically decrease the computational effort and cost imposed to the project, which is of great importance especially to the owners. The results are presented in terms of probability of occurrence and most likely values of the horizontal displacement at top of the wall at every stage of construction. Moreover, a methodology for assessing the credibility of the uncertainty model is presented using a quality indicator. It was concluded that performing RS analysis before the beginning of every stage could cause great economical savings, while improving the safety of the project.

关键词: uncertainty     reliability analysis     deep excavations     random set method     finite difference method    

Lamb wave propagation modeling for structure health monitoring

Xiaoyue ZHANG, Shenfang YUAN, Tong HAO

《机械工程前沿(英文)》 2009年 第4卷 第3期   页码 326-331 doi: 10.1007/s11465-009-0045-6

摘要: This study aims to model the propagation of Lamb waves used in structure health monitoring. A number of different numerical computational techniques have been developed for wave propagation studies. The local interaction simulation approach, used for modeling sharp interfaces and discontinuities in complex media (LISA/SIM theory), has been effectively applied to numerical simulations of elastic wave interaction. This modeling is based on the local interaction simulation approach theory and is finally accomplished through the finite elements software Ansys11. In this paper, the Lamb waves propagating characteristics and the LISA/SIM theory are introduced. The finite difference equations describing wave propagation used in the LISA/SIM theory are obtained. Then, an anisotropic metallic plate model is modeled and a simulating Lamb waves signal is loaded on. Finally, the Lamb waves propagation modeling is implemented.

关键词: Lamb wave     modeling     LISA/SIM theory     finite difference equation     finite element    

Flow, thermal, and vibration analysis using three dimensional finite element analysis for a flux reversal

B. VIDHYA,K. N. SRINIVAS

《能源前沿(英文)》 2016年 第10卷 第4期   页码 424-440 doi: 10.1007/s11708-016-0423-9

摘要: This paper presents the simulation of major mechanical properties of a flux reversal generator (FRG) viz., computational fluid dynamic (CFD), thermal, and vibration. A three-dimensional finite element analysis (FEA) based CFD technique for finding the spread of pressure and air velocity in air regions of the FRG is described. The results of CFD are mainly obtained to fine tune the thermal analysis. Thus, in this focus, a flow analysis assisted thermal analysis is presented to predict the steady state temperature distribution inside FRG. The heat transfer coefficient of all the heat producing inner walls of the machine are evaluated from CFD analysis, which forms the main factor for the prediction of accurate heat distribution. The vibration analysis is illustrated. Major vibration sources such as mechanical, magnetic and applied loads are covered elaborately which consists of a 3D modal analysis to find the natural frequency of FRG, a 3D static stress analysis to predict the deformation of the stator, rotor and shaft for different speeds, and an unbalanced rotor harmonic analysis to find eccentricity of rotor to make sure that the vibration of the rotor is within the acceptable limits. Harmonic analysis such as sine sweep analysis to identify the range of speeds causing high vibrations and steady state vibration at a mode frequency of 1500 Hz is presented. The vibration analysis investigates the vibration of the FRG as a whole, which forms the contribution of this paper in the FRG literature.

关键词: flux reversal generator     air velocity     computation fluid dynamics     thermal analysis     vibration analysis     finite element analysis    

Uncertainty assessment in hydro-mechanical-coupled analysis of saturated porous medium applying fuzzyfinite element method

Farhoud KALATEH, Farideh HOSSEINEJAD

《结构与土木工程前沿(英文)》 2020年 第14卷 第2期   页码 387-410 doi: 10.1007/s11709-019-0601-z

摘要: The purpose of the present study was to develop a fuzzy finite element method, for uncertainty quantification of saturated soil properties on dynamic response of porous media, and also to discrete the coupled dynamic equations known as - hydro-mechanical equations. Input parameters included fuzzy numbers of Poisson’s ratio, Young’s modulus, and permeability coefficient as uncertain material of soil properties. Triangular membership functions were applied to obtain the intervals of input parameters in five membership grades, followed up by a minute examination of the effects of input parameters uncertainty on dynamic behavior of porous media. Calculations were for the optimized combinations of upper and lower bounds of input parameters to reveal soil response including displacement and pore water pressure via fuzzy numbers. Fuzzy analysis procedure was verified, and several numerical examples were analyzed by the developed method, including a dynamic analysis of elastic soil column and elastic foundation under ramp loading. Results indicated that the range of calculated displacements and pore pressure were dependent upon the number of fuzzy parameters and uncertainty of parameters within equations. Moreover, it was revealed that for the input variations looser sands were more sensitive than dense ones.

关键词: fuzzy finite element method     saturated soil     hydro-mechanical coupled equations     coupled analysis     uncertainty analysis    

Nonlinear finite element analysis of short-limbed wall

Zhi ZHANG, Qian GU, Shaomin PENG, Quanzhi CAI

《结构与土木工程前沿(英文)》 2009年 第3卷 第2期   页码 125-130 doi: 10.1007/s11709-009-0025-2

摘要: Combined with the actual project, this paper carries out a nonlinear finite element analysis on 2 groups, 6 short-limbed shear walls, through the finite element calculation software ANSYS. The stress-strain relation of the models, and the effects of the type of sections and the axial compression ratios on the models can be obtained, providing a reference for future design.

关键词: short-limbed wall (SLW)     nonlinear finite element     separate model     axial compression ratios    

Advanced finite element analysis of a complex deep excavation case history in Shanghai

Yuepeng DONG, Harvey BURD, Guy HOULSBY, Yongmao HOU

《结构与土木工程前沿(英文)》 2014年 第8卷 第1期   页码 93-100 doi: 10.1007/s11709-014-0232-3

摘要: The construction of the North Square Shopping Center of the Shanghai South Railway Station is a large scale complex top-down deep excavation project. The excavation is adjacent to several current and newly planned Metro lines, and influenced by a neighboring Exchange Station excavation. The highly irregular geometry of this excavation greatly increases the complexity in 3D Finite Element modeling. The advanced numerical modeling described in this paper includes detailed structural and geotechnical behavior. Important features are considered in the analysis, e.g., 1) the small-strain stiffness of the soil, 2) the construction joints in the diaphragm wall, 3) the shrinkage in the concrete floor slabs and beams, 4) the complex construction sequences, and 5) the shape effect of the deep excavation. The numerical results agree well with the field data, and some valuable conclusions are generated.

关键词: advanced finite element analysis     deep excavations     case history     small-strain stiffness    

Finite element analysis of controlled low strength materials

Vahid ALIZADEH

《结构与土木工程前沿(英文)》 2019年 第13卷 第5期   页码 1243-1250 doi: 10.1007/s11709-019-0553-3

摘要: Controlled low strength materials (CLSM) are flowable and self-compacting construction materials that have been used in a wide variety of applications. This paper describes the numerical modeling of CLSM fills with finite element method under compression loading and the bond performance of CLSM and steel rebar under pullout loading. The study was conducted using a plastic-damage model which captures the material behavior using both classical theory of elasto-plasticity and continuum damage mechanics. The capability of the finite element approach for the analysis of CLSM fills was assessed by a comparison with the experimental results from a laboratory compression test on CLSM cylinders and pullout tests. The analysis shows that the behavior of a CLSM fill while subject to a failure compression load or pullout tension load can be simulated in a reasonably accurate manner.

关键词: CLSM     finite element method     compressive strength     pullout     numerical modeling     plastic damage model    

Total stress rapid drawdown analysis of the Pilarcitos Dam failure using the finite element method

Daniel R. VANDENBERGE

《结构与土木工程前沿(英文)》 2014年 第8卷 第2期   页码 115-123 doi: 10.1007/s11709-014-0249-7

摘要: Rapid drawdown is a critical design condition for the upstream or riverside slope of earth dams and levees. A new total stress rapid drawdown method based on finite element analysis is used to analyze the rapid drawdown failure that occurred at Pilarcitos Dam in 1969. Effective consolidation stresses in the slope prior to drawdown are determined using linear elastic finite element analysis. Undrained strengths from isotropically consolidated undrained (ICU) triaxial compression tests are related directly to the calculated consolidation stresses and assigned to the elements in the model by interpolation. Two different interpretations of the undrained strength envelope are examined. Strength reduction finite element analyses are used to evaluate stability of the dam. Back analysis suggests that undrained strengths from ICU tests must be reduced by 30% for use with this rapid drawdown method. The failure mechanism predicted for Pilarcitos Dam is sensitive to the relationship between undrained strength and consolidation stress.

关键词: rapid drawdown     finite element     total stress     slope stability    

Temperature difference-powered carbon nanotube bearings

Quanwen HOU, Bingyang CAO, Zengyuan GUO

《能源前沿(英文)》 2011年 第5卷 第1期   页码 49-52 doi: 10.1007/s11708-010-0111-0

摘要: Molecular dynamics simulations are conducted to study the motion of carbon nanotube-based nanobearings powered by temperature difference. When a temperature difference exists between stator nanotubes, the rotor nanotubes acquire a higher temperature, which arises from the interaction between phonon currents and nanotubes. The thermal driving force increases with the increase in temperature difference between the stators, an increase that is nearly proportional to the temperature difference. Confined by the minimum energy track, the (5, 5)@(10, 10) nanotube bearings only translate along the axis direction but without successive rotation.

关键词: temperature difference-induced motion     carbon nanotubes     nanobearing     molecular dynamics simulation    

Vibration analysis of a simply supported beam under moving mass based on moving finite element method

Zhuchao YE, Huaihai CHEN,

《机械工程前沿(英文)》 2009年 第4卷 第4期   页码 397-400 doi: 10.1007/s11465-009-0044-7

摘要: In this paper, a moving finite element (MFE) method is proposed to perform the dynamic analysis of a simply supported beam for a moving mass (MM). The MFE method treats the moving mass as a moving part of the entire system, so that the transverse inertial effects caused by the moving mass may easily be taken into account. The solution to the beam’s dynamic behaviors including its displacement is obtained via a Newmark-β method; the effects of the velocity and weight of the MM on the beam’s dynamic behaviors are further discussed. The numerical examples show that the inertial effects of the MM significantly affect the transverse responses of the simply supported beam.

关键词: simply supported beam     moving mass (MM)     transverse vibration     moving finite element (MFE)    

IPMC gripper static analysis based on finite element analysis

Hanmin PENG, Yao HUI, Qingjun DING, Huafeng LI, Chunsheng ZHAO,

《机械工程前沿(英文)》 2010年 第5卷 第2期   页码 204-211 doi: 10.1007/s11465-010-0005-1

摘要: Recently, a type of flexible grippers with low power supply (0–5 V) has been designed and developed for grasping small but precision parts. In previous work, the authors manufactured a soft gripper whose actuating components are made of ionic polymer-metal composite (IPMC) materials; however, there is not a comprehensive model to analyze the complete mechanics for this IPMC gripper. Therefore, this paper provides a finite element method for analyzing its static mechanics characteristics in the state with maximal stress and strain (i.e., the gripper opening largest, including the IPMC deformation, stress, and strain). Further, these electromechanical coupling relationships can be simulated by using the piezoelectric analysis module based on ANSYS software. The simulation results show that the maximal tip displacement of IPMC strips can nearly reach their own free length, the maximal stress is 54 MPa in the center of copper electrodes, and the maximal strain is 0.0286 on the IPMC strip. The results provide detailed numerical solutions and appropriate finite element analysis methodologies beneficial for further research on the optimization design, forecast analysis, and control field.

关键词: ionic polymer-metal composite (IPMC)     artificial muscles     actuator     flexible gripper     finite element analysis     electromechanical coupling    

Finite element analysis of creep for plane steel frames in fire

Hui ZHU, Yuching WU

《结构与土木工程前沿(英文)》 2012年 第6卷 第3期   页码 297-307 doi: 10.1007/s11709-012-0162-x

摘要: Steel is widely used for the construction of bridges, buildings, towers, and other structures because of its great strength, light weight, ductility, and ease of fabrication, but the cost of fireproofing is a major disadvantage. Therefore, the resistance of a steel structure to fire is a significant subject for modern society. In the past, for simplification, creep behavior was not taken into account in research on the resistance of a steel structure to fire. However, it was demonstrated that the effect of creep is considerable at temperatures that commonly reach 600°C and should not be neglected in this context. In this paper, a co-rotational total Lagrangian finite element formulation is derived, and the corresponding numerical model is developed to study the creep behavior of plane steel frames in fire conditions. The geometric nonlinearity, material nonlinearity, high temperature creep, and temperature rate of change are taken into account. To verify the accuracy and efficiency of the numerical model, four prototypical numerical examples are analyzed using this model, and the results show very good agreement with the solutions in the literature. Next, the numerical model is used to analyze the creep behavior of the plane steel frames under decreasing temperatures. The results indicate that the effect of creep is negligible at temperatures lower than 500°C and is considerable at temperatures higher than 500°C. In addition, the heating rate is a critical factor in the failure point of the steel frames. Furthermore, it is demonstrated that the deflection at the midpoint of the steel beam, considering creep behavior, is approximately 13% larger than for the situation in which creep is ignored. At temperatures higher than 500°C, the deformed steel member may recover approximately 20% of the total deflection. The application of the numerical model proposed in this paper is greatly beneficial to the steel industry for creep analysis, and the numerical results make a significant contribution to the understanding of resistance and protection for steel structures against disastrous fires.

关键词: creep     plane steel frame     fire     finite element method     geometric nonlinearity    

3D finite element analysis of composite noise barrier constructed of polyurethane products

Ben DAEE,Hesham El NAGGAR

《结构与土木工程前沿(英文)》 2017年 第11卷 第1期   页码 100-110 doi: 10.1007/s11709-016-0364-8

摘要: This paper presents a numerical investigation on the structural performance of an innovative noise barrier consisting of poly-block, rigid polyurethane foam (RPF) and polyurea. The mechanical characteristics of RPF as well as the flexural resistance of the proposed wall system (poly-wall) were established and presented in another study. The experimental results are used in the current study to develop, calibrate and verify 3D finite element (FE) models of the wall system. The components of the poly-wall including steel rebars, poly-blocks and RPF cores were simulated and then verified using the results of experiments conducted on the wall components. The results of numerical analysis exhibited a satisfactory agreement with the experimental outcomes for the entire wall system. The verified numerical models were then used to conduct a parametric study on the performance of poly-wall models under uniform wind load and gravity load. The findings of the current study confirmed that the structural performance of poly-wall is satisfactory for noise barrier application. Simulation techniques for improvement of the numerical analysis of multi-martial 3D FE models were discussed.

关键词: 3D finite element     sound wall     rigid polyurethane foam     poly-wall     numerical model     calibration    

Soil seismic analysis for 2D oblique incident waves using exact free-field responses by frequency-basedfinite/infinite element method

《结构与土木工程前沿(英文)》 2022年 第16卷 第12期   页码 1530-1551 doi: 10.1007/s11709-022-0900-7

摘要: The seismic analysis of a viscoelastic half-space under two-dimensional (2D) oblique incident waves is carried out by the finite/infinite element method (FIEM). First, the frequency-domain exact solutions for the displacements and stresses of the free field are derived in general form for arbitrary incident P and SV waves. With the present formulation, no distinction needs to be made for SV waves with over-critical incident angles that make the reflected P waves disappear, while no critical angle exists for P waves. Next, the equivalent seismic forces of the earthquake (Taft Earthquake 1952) imposed on the near-field boundary are generated by combining the solutions for unit ground accelerations with the earthquake spectrum. Based on the asymmetric finite/infinite element model, the frequency-domain motion equations for seismic analysis are presented with the key parameters selected. The results obtained in frequency and time domain are verified against those of Wolf’s, Luco and de Barros’ and for inversely computed ground motions. The parametric study indicated that distinct phase difference exists between the horizontal and vertical responses for SV waves with over-critical incident angles, but not for under-critical incident angles. Other observations were also made for the numerical results inside the text.

关键词: oblique incident waves     critical angle     half-space     finite/infinite element approach     seismic response analysis    

标题 作者 时间 类型 操作

Three-dimensional finite difference analysis of shallow sprayed concrete tunnels crossing a reverse fault

Masoud RANJBARNIA, Milad ZAHERI, Daniel DIAS

期刊论文

Application of random set method in a deep excavation: based on a case study in Tehran cemented alluvium

Arash SEKHAVATIAN, Asskar Janalizadeh CHOOBBASTI

期刊论文

Lamb wave propagation modeling for structure health monitoring

Xiaoyue ZHANG, Shenfang YUAN, Tong HAO

期刊论文

Flow, thermal, and vibration analysis using three dimensional finite element analysis for a flux reversal

B. VIDHYA,K. N. SRINIVAS

期刊论文

Uncertainty assessment in hydro-mechanical-coupled analysis of saturated porous medium applying fuzzyfinite element method

Farhoud KALATEH, Farideh HOSSEINEJAD

期刊论文

Nonlinear finite element analysis of short-limbed wall

Zhi ZHANG, Qian GU, Shaomin PENG, Quanzhi CAI

期刊论文

Advanced finite element analysis of a complex deep excavation case history in Shanghai

Yuepeng DONG, Harvey BURD, Guy HOULSBY, Yongmao HOU

期刊论文

Finite element analysis of controlled low strength materials

Vahid ALIZADEH

期刊论文

Total stress rapid drawdown analysis of the Pilarcitos Dam failure using the finite element method

Daniel R. VANDENBERGE

期刊论文

Temperature difference-powered carbon nanotube bearings

Quanwen HOU, Bingyang CAO, Zengyuan GUO

期刊论文

Vibration analysis of a simply supported beam under moving mass based on moving finite element method

Zhuchao YE, Huaihai CHEN,

期刊论文

IPMC gripper static analysis based on finite element analysis

Hanmin PENG, Yao HUI, Qingjun DING, Huafeng LI, Chunsheng ZHAO,

期刊论文

Finite element analysis of creep for plane steel frames in fire

Hui ZHU, Yuching WU

期刊论文

3D finite element analysis of composite noise barrier constructed of polyurethane products

Ben DAEE,Hesham El NAGGAR

期刊论文

Soil seismic analysis for 2D oblique incident waves using exact free-field responses by frequency-basedfinite/infinite element method

期刊论文