scholarly journals Analysis of Undrained Seismic Behavior of Shallow Tunnels in Soft Clay Using Nonlinear Kinematic Hardening Model

2020 ◽  
Vol 10 (8) ◽  
pp. 2834
Author(s):  
Mohsen Saleh Asheghabadi ◽  
Xiaohui Cheng
Keyword(s):  
Finite Element ◽  
Kinematic Hardening ◽  
Soft Clay ◽  
Hysteresis Loops ◽  
Stiffness Degradation ◽  
Triaxial Tests ◽  
Embedment Depth ◽  
Ground Acceleration ◽  
Cyclic Shear ◽  
Hardening Model

In this study, a soil–tunnel model for clay under earthquake loading is analyzed, using finite element methods and a kinematic hardening model with the Von Mises failure criterion. The results are compared with those from the linear elastic–perfectly plastic Mohr–Coulomb model. The latter model does not consider the stiffness degradation caused by imposing cyclic loading and unloading to the soil, whereas the kinematic hardening model can simulate this stiffness degradation. The parameters of the kinematic hardening model are calibrated based on the results of experimental cyclic tests and finite element simulation. Here, two methods—one using data from cyclic shear tests, and the other a new method using undrained cyclic triaxial tests—are used to calibrate the parameters. The parameters investigated are the peak ground acceleration (PGA), tunnel lining thickness, tunnel shape, and tunnel embedment depth, all of which have an effect on the resistance of the shallow tunnel to the stresses and deformations caused by the surrounding clay soils. The results show that unlike traditional models, the nonlinear kinematic hardening model can predict the response reasonably well, and it is able to create the hysteresis loops and consider the soil stiffness degradation under the seismic loads.

scholarly journals Investigation of Seismic Behavior of Clay-Pile Using Nonlinear Kinematic Hardening Model

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Mohsen Saleh Asheghabadi ◽  
Xiaohui Cheng
Keyword(s):  
Seismic Behavior ◽  
Kinematic Hardening ◽  
Bending Moment ◽  
Pile Group ◽  
Triaxial Tests ◽  
Model Parameters ◽  
Elastic Model ◽  
Cyclic Shear ◽  
Hardening Model ◽  
Calibration Methods

In geotechnical mediums where the bearing capacity of upper layers of soil is not suitable for use of the shallow foundations, piles are usually used as deep foundations to transfer loads to the stronger lower layers. Here, the seismic behavior of single pile and pile group constructed in saturated soft kaolin clay under three different earthquakes using Abacus 3D software is investigated. The aluminum material considering the linear elastic model has been used for the piles, and the nonlinear kinematic hardening model with Von Mises failure criterion has been considered for clay. This model can consider the soil stiffness degradation by increasing the number of cyclic loading. Three different methods have been used to calibrate the model parameters, two of them are new methods. In all calibration methods, the cyclic shear and undrained cyclic triaxial tests are used. The results obtained from the numerical analysis of the soil-pile model are in relatively good agreement with the centrifuge model results. According to the results, the variation of earthquake frequency and intensity affects the bending moment created along the pile and also the distance between piles in a pile group affects the amount of the interaction between them.

Energy-Consistent Finite Element Modelling of Ferromagnetic Hysteresis

2012 ◽  
Author(s):  
Christophe Geuzaine ◽  
Laurent Stainier ◽  
Francois Henrotte
Keyword(s):  
Finite Element ◽  
Magnetic Energy ◽  
Kinematic Hardening ◽  
Hysteresis Loops ◽  
Macroscopic Model ◽  
Dissipated Energy ◽  
Internal Variables ◽  
Incremental Formulation ◽  
Ferromagnetic Hysteresis ◽  
Electromagnetic Models

In this article we propose a macroscopic model for ferromagnetic hysteresis that is well-suited for finite element implementation. The model is readily vectorial and relies on a consistent thermodynamic formulation. In particular, the stored magnetic energy and the dissipated energy are known at all times, and not solely after the completion of closed hysteresis loops as is usually the case. The obtained incremental formulation is variationally consistent, i.e., all internal variables follow from the minimization of a thermodynamic potential. This variational approach is directly inspired from the kinematic hardening theory of plasticity, which opens the door for novel energy-consistent coupled mechanical/electromagnetic models.

3-D Elastic-Plastic Constitutive Relationship of Mixed Hardening

2012 ◽  
Vol 249-250 ◽  
pp. 927-930
Author(s):  
Ze Yu Wu ◽  
Xin Li Bai ◽  
Bing Ma
Keyword(s):  
Finite Element ◽  
Constitutive Relation ◽  
Kinematic Hardening ◽  
Constitutive Relationship ◽  
Isotropic Hardening ◽  
Element Analysis ◽  
Hardening Model ◽  
Elastic Plastic ◽  
Mixed Hardening ◽  
Advantages And Disadvantages

In finite element calculation of plastic mechanics, isotropic hardening model, kinematic hardening model and mixed hardening model have their advantages and disadvantages as well as applicability area. In this paper, by use of the tensor analysis method and mixed hardening theory in plastic mechanics, the constitutive relation of 3-D mixed hardening problem is derived in detail based on the plane mixed hardening. Numerical results show that, the proposed 3-D mixed hardening constitutive relation agrees well with the test results in existing references, and can be used in the 3-D elastic-plastic finite element analysis.

Seismic Performance of Concrete-Filled-Tube Column to RBS Beam Connections with Crossing Diaphragm - Finite Element Analysis

2011 ◽  
Vol 71-78 ◽  
pp. 1495-1498 ◽  
Author(s):  
Cheng Yu Li ◽  
Rui Li
Keyword(s):  
Finite Element ◽  
Tensile Force ◽  
Plastic Hinge ◽  
Hysteresis Loops ◽  
Steel Tube ◽  
Stiffness Degradation ◽  
Element Analysis ◽  
Distribution Rules ◽  
H Beam ◽  
Core Concrete

For studying seismic behavior of concrete filled steel tube (CFST) column to RBS beam connections with crossing diaphragm under cyclic loading, Base on 3-D nonlinear finite element models which were used to analyze the mechanical properties using ANSYS, compared with CFST column to H-beam connections with exterior concentric annular, the finite element analyses were conducted to investigate the influences of hysteresis loops, the stress distribution rules, stiffness degradation and failure mechanism. It found that this connection not only transfers a plastic hinge from the root of beam end to the reduce section, but it little affects stiffness degradation. In addition, due to the crossing diaphragm that is beneficial to transfer shear to core concrete and provides the tensile force to beam, it improves the deformation of column. Consequently, this joint has a better seismic capability.

Application of Elastic-Plastic Design Data in the New ASME B&PV Code Section VIII Division 2

2010 ◽  
Author(s):  
David J. Dewees
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Plastic Material ◽  
Kinematic Hardening ◽  
Strain Curve ◽  
Design Data ◽  
Hardening Model ◽  
Elastic Plastic ◽  
Section Viii ◽  
Division 2

The updating and re-writing of the ASME Boiler and Pressure Vessel Code, Section VIII Division 2 (2007) [1] has introduced several new and unique features. One of these features is the inclusion of specific materials data for use in elastic-plastic analysis of pressure vessel components. Both monotonic and cyclic stress strain curve models are provided, with supporting constants for a range of materials and temperatures. The elastic-perfectly plastic material model has been used in commercial Finite Element (FE) codes for many years to perform limit load and ratcheting analyses. The new material models and data of Section VIII Division 2 (S8D2) include strain hardening and are intended for use in deformation assessments, and for determining cyclic plastic strain ranges in fatigue evaluations. This paper presents one possible implementation of the Code models and data into a standard cyclic hardening model; the multiple backstress, nonlinear kinematic-hardening model of Chaboche, as implemented in the commercial Finite Element program Abaqus, versions 6.8 and later.

scholarly journals Cyclic Loading Test for the Small-Strain Shear Modulus of Saturated Soft Clay and Its Failure Mechanism

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhende Zhu ◽  
Cong Zhang ◽  
Jun Wang ◽  
Peng Zhang ◽  
Duan Zhu
Keyword(s):  
Shear Stress ◽  
Shear Modulus ◽  
Effective Stress ◽  
Soft Clay ◽  
Small Strain ◽  
Triaxial Tests ◽  
Loading Test ◽  
Cyclic Shear ◽  
Small Strain Shear Modulus ◽  
Saturated Soft Clay

Small-strain shear modulus, G max , is a key evaluation index to study the dynamic characteristics of soil in geotechnical engineering. It is widely adopted to evaluate the stiffness of soft soil in soil dynamic engineering. In this paper, the cyclic triaxial tests and resonance column tests were carried out to explore the variation of G max of soft clay with respect to various confining stresses, cyclic shear stress ratios, pore pressures, and effective stress paths. Test results indicated that the effective stress decreased gradually with the increase of the cycle shear stress ratio. The failure points were mainly concentrated in a rectangular area, defined by the normalized effective stress from 0.56 to 0.64 and the normalized shear modulus from 0.72 to 0.78. Additionally, a short pause caused a small increase of 1-2% in G max as well as pore pressure. This study demonstrates that G max can be effectively used to characterize the failure of saturated soft clay in a more intuitive and convenient way, compared to the commonly used strain failure standards.

Effect of Nonlinear Kinematic Hardening Constants on Cyclic Spherical Indentation Test

2010 ◽  
Author(s):  
A. Nayebi
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Applied Load ◽  
Kinematic Hardening ◽  
Hysteresis Loops ◽  
Indentation Test ◽  
Material Behavior ◽  
Spherical Indentation ◽  
Displacement Curve ◽  
Residual Displacements

In the last decade, instrumented indentation test has been widely used to determine the mechanical properties of different materials and especially for metals. The mechanical properties such as Young modulus, yield stress, hardening exponent, and stress-strain curve were determined with the help of the load–displacement curve of the continuous indentation test. The method consists of pushing an indenter in a material sample and the applied load and the indenter displacement are measured. In this research the load on the indenter was considered as cyclic and varied from zero to Fmax. Because of the Bauschinger effect, the hysteresis loops were formed. With the help of these hysteresis loops, nonlinear kinematic hardening parameters of the Armstrong–Freiderick (A-F) model can be determined. Spherical indenter was used and the sample was considered isotropic. The material behavior was modeled by the A-F rule. The test was modeled by the finite element method. An axi-symmetric mesh was used. The A–F model constants, C and γ, were varied to obtain their effects on the hysteresis loops. Maximum applied load was considered constant for different finite element modeling and the maximum and residual displacements were calculated from the simulations results. The normalized maximum and the residual displacements were increased as a function of the cycles. It was shown that these parameters value and their rate are dependent on the material model constants. These dependences were shown for different examples which can help to characterize the A-F model constants by the cyclic spherical indentation tests.

Stability Analysis of the Semi-Circular Guiding Dike

2014 ◽  
Vol 638-640 ◽  
pp. 1270-1273
Author(s):  
Zhong Xiao ◽  
Yuan Zhan Wang ◽  
Ke Li Sun ◽  
Li Qiang Sun
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Yield Criterion ◽  
Soft Clay ◽  
Wave Load ◽  
Obvious Effect ◽  
Cyclic Shear ◽  
Finite Element Software ◽  
Soft Foundation ◽  
Before And After

A quasi static finite element method for assessing cyclic bearing capacity of semi-circular guiding dike on natural or reinforced soft clay foundation is developed by combining the concept of cyclic shear strength with D-P yield criterion. Then the proposed method is numerically implemented in the framework of the large universal finite element software. Combining with a practical engineering, the stability of semi-circular guiding dike before and after foundation reinforcement is analyzed. The results showed that the foundation bearing capacity decreases obviously when cyclic weakening effect of soft foundation was considered, so cyclic weakening effect of soft foundation under cyclic wave load should be considered in practical design. Moreover, foundation reinforcement has an obvious effect to increase foundation bearing capacity.

scholarly journals Finite-Element Analysis of Keying Process of Plate Anchors in Three-Layer Soft-Stiff-Soft Clay Deposits

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Tugen Feng ◽  
Huajiao Xu ◽  
Jian Song ◽  
Jian Zhang ◽  
Mi Zhou ◽  
...  
Keyword(s):  
Finite Element ◽  
Soft Clay ◽  
Soil Layer ◽  
Three Dimensional ◽  
Embedment Depth ◽  
Element Analysis ◽  
Clay Deposits ◽  
Local Soil ◽  
Plate Anchors ◽  
Stiff Soil

This paper presents the results from numerical modeling of the keying process of plate anchors in three-layer soft-stiff-soft clay deposits. Three-dimensional large deformation finite-element analyses were carried out, and the results were firstly validated by the centrifuge test data and the previous numerical results. The soil flow mechanism during the keying process of plate anchors was examined, and a series of parametric studies were performed to investigate the factors affecting the rotation characteristics of plate anchors with an emphasis on the presence of the interbedded stiff soil layer. The results indicate that the loss of embedment depth of plate anchors decreases with the increase of the thickness of the first soil layer when the anchor is initially located at the middle of stiff soil layer. The flow velocity of soil around the anchor that is initially embedded at the first layer and adjacent to the underlying interbedded stiff soil layer is generally larger, resulting in a smaller embedment depth loss compared with the traditional normally consolidated soil layer. The interbedded stiff soil layer affects the keying process of plate anchors embedded 1.0B above and 2.0B below the interbedded stiff soil layer (B is the width of the square plate anchors). The increase of the strength of local soil around the plate anchors leads to the increase of the embedment depth loss, but the increase of the strength of soil slightly away from the plate anchors leads to the decrease of the embedment depth loss.

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