An evaluation of simplified techniques for estimating three-dimensional undrained ground movements due to tunnelling in soft soils

1992 ◽  
Vol 29 (1) ◽  
pp. 39-52 ◽  
Author(s):  
R. K. Rowe ◽  
K. M. Lee
Keyword(s):  
Plane Strain ◽  
Deformation Behaviour ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Cumulative Probability ◽  
Element Analysis ◽  
Cross Sectional ◽  
Soft Soils ◽  
Longitudinal Plane ◽  
Stress Changes

A number of simplified approaches have been used by various researchers to estimate the three-dimensional stress changes and ground deformations due to shallow tunnels in soft soils. The effectiveness of these simplified analyses, such as (i) axisymmetric analysis, (ii) longitudinal plane strain analysis, and (iii) empirical cumulative probability distribution approach, has been examined by comparison of results with those from a full three-dimensional elastoplastic finite-element analysis. For tunnels located at shallow depths, axisymmetric analyses are generally found to be unable to predict the correct magnitude of displacement around a tunnel heading. However, the trend of the three-dimensional deformation behaviour near the tunnel heading can be reasonably approximated by the average of the normalized displacement curves predicted by the two axisymmetric assumptions as described in this paper. The three-dimensional distribution of the displacement near the ground surface, on the other hand, can be approximately predicted by the cumulative probability approach, provided that the three empirical parameters required by the equations are reasonably estimated. In this paper, these parameters were estimated from the result of a two-dimensional plane strain cross-sectional analysis. Finally, it was found that modelling of three-dimensional deformations by a longitudinal plane strain analysis did not give good results for the cases examined. Key words : tunnelling, soft ground, analysis.

Three-dimensional analysis of soil – steel bridges

1995 ◽  
Vol 22 (6) ◽  
pp. 1155-1163 ◽  
Author(s):  
Youssef Girges ◽  
George Abdel-Sayed
Keyword(s):  
Plane Strain ◽  
Dimensional Analysis ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Middle Part ◽  
Steel Bridges ◽  
Steel Shell ◽  
Live Load ◽  
Two Dimensional ◽  
Element Analysis

The present design of soil–steel bridges is based on plane-strain analysis by considering a slice of a unit width of the conduit wall and the surrounding soil. This two-dimensional analysis neglects the third-dimensional effect of the steel shell and the soil continuum which could be significant especially when the load varies in the longitudinal direction, as in the case of live load acting over a shallow cover. The structure is also subjected to a varying dead load due to the variation in the depth of cover from maximum at the middle part of the conduit to zero at the conduit edges. A three-dimensional finite element analysis is presented in this paper to examine the actual three-dimensional behaviour of soil-steel bridges. The thrust and bending moment around the conduit walls as well as the stability of a single conduit are presented and compared with the results obtained from plane-strain analysis. Also, the live load dispersion in the soil above the conduit is examined and compared with some present codes. The study leads to evaluation of the degree of approximation inherited with the practical approaches of the two-dimensional analysis. Key words: conduit, corrugated steel, three-dimensional analysis, stability, soil–steel bridges.

Three-Dimensional Strain-Based Model for the Severity Characterization of Dented Pipelines

2018 ◽  
Vol 1 (3) ◽  
Author(s):  
Chike Okoloekwe ◽  
Muntaseer Kainat ◽  
Doug Langer ◽  
Sherif Hassanien ◽  
J.J. Roger Cheng ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Numerical Models ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Computation Time ◽  
Order Continuity ◽  
Element Analysis ◽  
The Mathematical Model ◽  
Derivatives Of

Oil and gas pipelines traverse long distances and are often subjected to mechanical forces that result in permanent distortion of its geometric cross section in the form of dents. In order to prioritize the repair of dents in pipelines, dents need to be ranked in order of severity. Numerical modeling via finite element analysis (FEA) to rank the dents based on the accumulated localized strain is one approach that is considered to be computationally demanding. In order to reduce the computation time with minimal effect to the completeness of the strain analysis, an approach to the analytical evaluation of strains in dented pipes based on the geometry of the deformed pipe is presented in this study. This procedure employs the use of B-spline functions, which are equipped with second-order continuity to generate displacement functions, which define the surface of the dent. The strains associated with the deformation can be determined by evaluating the derivatives of the displacement functions. The proposed technique will allow pipeline operators to rapidly determine the severity of a dent with flexibility in the choice of strain measure. The strain distribution predicted using the mathematical model proposed is benchmarked against the strains predicted by nonlinear FEA. A good correlation is observed in the strain contours predicted by the analytical and numerical models in terms of magnitude and location. A direct implication of the observed agreement is the possibility of performing concise strain analysis on dented pipes with algorithms relatively easy to implement and not as computationally demanding as FEA.

C-Specimen Fracture Toughness Testing: Effect of Side Grooves and η Factor

2003 ◽  
Author(s):  
Y. Kim ◽  
Y. J. Chao ◽  
M. J. Pechersky ◽  
M. J. Morgan
Keyword(s):  
Fracture Toughness ◽  
Plane Strain ◽  
Crack Front ◽  
Testing Effect ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
J Integral ◽  
Η Factor

Elastic-plastic crack front fields in arc-shaped tension specimens (C-specimens) were analyzed by a three-dimensional finite element method. The effect of side grooves on the ductile fracture behavior was investigated by studying the J-integral distribution, plane-strain constraint parameter, and development of plastic zones and comparing to experimental data. The applicability of the η factor (derived for use with compact tension specimens) for the calculation of J-integral values for the C-specimen was also investigated. The results show that side grooves promote and establish near plane strain conditions at the crack front in sub-size specimens. It was also found that a two-dimensional plane-strain analysis in conjunction with the standard American Society for Testing and Materials (ASTM) tests was sufficient to determine the fracture toughness values from side-grooved C-specimen. The results indicate the η factor for compact tension specimen as specified in the ASTM standards appears to produce reliable results for the calculation of J of C-specimens.

C-Specimen Fracture Toughness Testing: Effect of Side Grooves and η Factor

2004 ◽  
Vol 126 (3) ◽  
pp. 293-299 ◽  
Author(s):  
Y. Kim ◽  
Y. J. Chao ◽  
M. J. Pechersky ◽  
M. J. Morgan
Keyword(s):  
Fracture Toughness ◽  
Plane Strain ◽  
Crack Front ◽  
Testing Effect ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
J Integral ◽  
Η Factor

Elastic-plastic crack front fields in arc-shaped tension specimens (C-specimens) were analyzed by a three-dimensional finite element method. The effect of side grooves on the ductile fracture behavior was investigated by studying the J-integral distribution, plane-strain constraint parameter, and development of plastic zones and comparing to experimental data. The applicability of the η factor (derived for use with compact tension specimens) for the calculation of J-integral values for the C-specimen was also investigated. The results show that side grooves promote and establish near plane strain conditions at the crack front in sub-size specimens. It was also found that a two-dimensional plane-strain analysis in conjunction with the standard American Society for Testing and Materials (ASTM) tests was sufficient to determine the fracture toughness values from side-grooved C-specimen. The results indicate the η factor for compact tension specimen as specified in the ASTM standards appears to produce reliable results for the calculation of J of C-specimens.

A simplified plane strain analysis of lateral wall deflection for excavations with cross walls

2012 ◽  
Vol 49 (10) ◽  
pp. 1134-1146 ◽  
Author(s):  
Pio-Go Hsieh ◽  
Chang-Yu Ou ◽  
Chiang Shih
Keyword(s):  
Plane Strain ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Lateral Wall ◽  
Diaphragm Wall ◽  
Beam Model ◽  
Two Dimensional ◽  
Wall Deflection ◽  
Dimensional Plane ◽  
Proposed Model

Previous studies have shown that installation of cross walls in deep excavations can reduce lateral wall deflection to a very small amount. To predict the lateral wall deflection for excavations with cross walls, it is necessary to perform a three-dimensional numerical analysis because the deflection behavior of the diaphragm wall with cross walls is by nature three dimensional. However for the analysis and design of excavations, two-dimensional plane strain analysis is mostly used in practice . For this reason, based on the deflection behavior of continuous beams and the superimposition principle, an equivalent beam model suitable for two-dimensional plane strain analysis was derived to predict lateral wall deflection for excavations with cross walls. Three excavation cases were employed to verify the proposed model. Case studies confirm the proposed equivalent beam model for excavations with cross walls installed from near the ground surface down to at least more than half the embedded depth of the diaphragm wall. For the case with a limited cross-wall depth, the proposed model yields a conservative predicted lateral wall deflection.

Three-Dimensional Reconstruction of Three Real Roots Included Periodontal Ligament and Implant Study

2014 ◽  
Vol 575 ◽  
pp. 931-934
Author(s):  
Qi Wang ◽  
Ling Chen ◽  
Zhong Zhang ◽  
Xing Hua Niu
Keyword(s):  
Finite Element ◽  
Periodontal Ligament ◽  
Three Dimensional ◽  
Element Model ◽  
Imaging Method ◽  
Element Analysis ◽  
Cross Sectional ◽  
The Real ◽  
Engineering Software ◽  
Ct Data

To investigate the periodontal ligament contains the real root of the three model cases, a combination of different implant and tooth variation of the stress distribution for the subsequent three root implant biomechanics analysis provides digital models. Methods: Mimics and Geomagic reverse engineering software for digital imaging method to obtain CT data processing. And the use of UG assembled in ANSYS workbench in finite element analysis. Results: A consistent with the real situation of three tooth root finite element model which contains periodontal ligament, and found that with the dental implant junction with the cross-sectional area decreases, where the stress amplitude fluctuations increases.

scholarly journals An Analytical Formulation for the Lateral Support Stiffness of a Spatial Flexure Strip

2015 ◽  
Author(s):  
Marijn Nijenhuis ◽  
J. P. Meijaard ◽  
Just L. Herder ◽  
Shorya Awtar ◽  
Dannis M. Brouwer
Keyword(s):  
Three Dimensional ◽  
Beam Element ◽  
Element Analysis ◽  
Cross Sectional ◽  
Flexure Mechanism ◽  
Stiffness Properties ◽  
Spatial Beam ◽  
Discrete Nature ◽  
Stiffness Characteristics

A flexure strip has constraint characteristics, such as stiffness properties and error motions, that limit its performance as a basic constituent of flexure mechanisms. This paper presents a framework for modeling the deformation and stiffness characteristics of general three-dimensional flexure strips that exhibit bending, shear and torsion deformation. The formulation is based on a finite strain discrete spatial beam element with refinements to account for plate-like behavior due to constrained cross-sectional warping. This framework is suited for analytical calculations thanks to the accuracy of the beam element, while its discrete nature allows for easy implementation in numeric software to serve as calculation aid. As case study, a closed-form parametric analytical expression is derived for the lateral support stiffness of a parallel flexure mechanism. This captures the deteriorating support stiffness when the mechanism moves in the intended degree of freedom. By incorporating relevant geometric nonlinearities and a warping constraint stiffening factor, an accurate load-displacement and stiffness expression for the lateral support direction is obtained. This result is verified by nonlinear finite element analysis.

Finite element analysis of peak stress and stress gradient at an elliptical through-hole

2017 ◽  
Vol 52 (5) ◽  
pp. 277-287
Author(s):  
Kristine Klungerbo ◽  
Gunnar Härkegård
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Plane Strain ◽  
Stress Gradient ◽  
Three Dimensional ◽  
Peak Stress ◽  
Two Dimensional ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Through Hole

The peak stress and stress gradient (parameters required for fatigue strength assessment) at an elliptical through-hole in a wide plate under uniaxial tension have been studied by means of three-dimensional finite element analysis with high mesh density. Dimensionless variables have been used throughout the investigation. The accuracy of two-dimensional finite element analysis has been assessed by extrapolating peak stress at an elliptical hole to infinite plate width and mesh density and comparing the extrapolated value with the closed-form Kolosov–Inglis solution (deviation < 0.2%). First- and second-order elements with full and reduced integration have been employed. Methods for determining stress gradients, using a varying number of nodal stresses, have been investigated. The accuracy of three-dimensional finite element analysis has been assessed by comparing the plane-strain peak stress for an elliptical through-hole with the corresponding plane-strain value from two-dimensional analysis (deviation < 0.1%). Peak stresses at the apex of the elliptical through-hole have also been determined for this three-dimensional mesh assuming a free plate surface. In particular, beside the maximum peak stress and its location, peak stresses have been determined at the surface and at the mid-plane of the plate for thicknesses ranging from 0.2 to 10 times the axis of the elliptical hole. The stress gradients at these locations have been determined, too. The minimum stress gradient is observed at the location of maximum stress. For sufficiently thin and thick plates, the mid-plane stresses approach two-dimensional plane-stress and generalised plane-strain solutions, respectively.

Mechanical Performance of Tubular Microtruss Materials Reinforced With Nanocrystalline Sleeves

2011 ◽  
Vol 1304 ◽  
Author(s):  
Eral Bele ◽  
Mishaal Azhar ◽  
Glenn D. Hibbard
Keyword(s):  
Mechanical Performance ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Structural Performance ◽  
Element Analysis ◽  
Cross Sectional ◽  
Polymeric Scaffolds ◽  
Characteristic Features ◽  
Inherent Strength ◽  
Material Grain Size

ABSTRACTMicrotruss cellular materials are assemblies of struts with characteristic features in the μm to mm scale, arranged in a periodic, three-dimensional architecture. Compared to conventional cellular architectures (e.g. stochastic foams and honeycombs), they can possess improved structural efficiency, because externally applied loads are resolved axially along the constituent struts. We have recently fabricated composite microtruss materials by electrodepositing reinforcing nanocrystalline sleeves on tubular polymeric scaffolds. These materials can offer enhanced structural performance by exploiting advantageous properties along three length scales: the inherent strength of the electrodeposited material (grain size reduction to the nm scale), its location away from the bending axis of the struts (cross-sectional efficiency in the μm scale), and the spatial arrangement of the struts (architectural efficiency in the mm scale). This study uses finite element analysis and experimental methods to characterize the mechanical properties of these composite materials.

scholarly journals FLEXURAL STRESS ANALYSIS OF RIGID PAVEMENTS USING AXI-SYMMETRIC AND PLANE STRAIN FEM

2017 ◽  
Vol 24 (4) ◽  
pp. 443-451
Author(s):  
V.A. Sawant ◽  
M.S. Norazzlina
Keyword(s):  
Plane Strain ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Climatic Conditions ◽  
Finite Element Analyses ◽  
Flexural Stress ◽  
Rigid Pavement ◽  
Rigid Pavements ◽  
Pca Method ◽  
Portland Cement Association

The design of pavement involves a study of soils and paving materials, their response under load for different climatic conditions. In the present study, an attempt has been made to compare stresses predicted using two finite element analyses. First analysis is based on the twodimensional plane strain assumption where as in second approach axi-symmetric condition is assumed to consider three-dimensional behavior of rigid pavement. The results are compared with flexural stresses obtained from conventional Portland Cement Association method. The computed flexural stresses obtained from axi-symmetric condition are found to be in close agreement with PCA method. Results of plane strain analysis show a fair agreement after application of an appropriate multiplication factor  

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