Observed and calculated load-settlement relationship in a sandy gravel

2000 ◽  
Vol 37 (2) ◽  
pp. 333-342 ◽  
Author(s):  
Fernando Rodríguez-Roa
Keyword(s):  
Finite Element ◽  
Constitutive Relations ◽  
Load Test ◽  
Triaxial Tests ◽  
Hyperbolic Model ◽  
Elastic Model ◽  
Stress Strain ◽  
Plate Load Test ◽  
Nonlinear Stress ◽  
Calculated Load

The purpose of this research was to obtain a better understanding of the nonlinear stress-strain behavior of the typical gravel of Santiago, Chile, due to the increasing needs for construction of high-rise buildings, multilevel underground constructions, and new subway lines to be built under historical city landmarks. A finite-element computer program to perform incremental stress-strain analyses of soils was developed on the basis of a modified version of the hyperbolic elastic model. The changes herein proposed to this well-known constitutive model were based on triaxial tests carried out on 150 mm diameter specimens of compacted sandy gravels which involved various stress paths. A comparison was performed between the observed and calculated load-settlement relationship in a plate-load test that included unloading-reloading cycles. From the good agreement obtained it is concluded that the modified version of the hyperbolic model proposed represents reasonably well the behavior of the Santiago gravel.Key words: constitutive relations, finite-element model, laboratory tests, field tests, soil properties, case history.

Implementation of the tangent modulus – vertical stress (Et–σv) model for flexible pavements analysis

2006 ◽  
Vol 43 (11) ◽  
pp. 1131-1143
Author(s):  
J -M Konrad ◽  
Ph D Nguyen
Keyword(s):  
Finite Element ◽  
Granular Material ◽  
Vertical Stress ◽  
Load Test ◽  
Tangent Modulus ◽  
Quebec City ◽  
Elastic Model ◽  
Loading Test ◽  
Test Plate ◽  
Plate Load Test

A recently developed nonlinear elastic model of granular material, referred to as the tangent modulus – vertical stress (Et–σv) model, was implemented into a finite element numerical solver FlexPDE. The FlexPDE program was used to compare deflection predictions with actual plate-load test data from a site near Québec City. The proposed Et–σv model performed well and led to excellent predictions for load levels of 40, 50, and 70 kN. Comparison with predictions using the Uzan model suggests that constitutive models of granular materials are best expressed in terms of vertical stress rather than mean stress for the prediction of elastic pavement response for field conditions.Key words: granular material, resilient modulus, triaxial test, plate-loading test, finite element.

Evaluation of a simplified small-strain soil model for analysis of excavation-induced movements

2007 ◽  
Vol 44 (6) ◽  
pp. 726-736 ◽  
Author(s):  
Gordon Tung-Chin Kung ◽  
Evan Cheng-Liang Hsiao ◽  
C Hsein Juang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Small Strain ◽  
Triaxial Tests ◽  
Case Histories ◽  
Stress Strain ◽  
Wall Deflection ◽  
Soil Model ◽  
Nonlinear Stress ◽  
Element Method

A simplified small-strain soil model, referred to herein as the modified pseudoplasticity (MPP) model, developed based on the small-strain behavior of clay measured from the triaxial tests is evaluated in this study. The simulation of the small-strain triaxial tests by the MPP model shows that nonlinear stress–strain characteristics of clays can be adequately accounted for at small strain, including the characteristic of high initial Young's modulus. Two well-documented excavation case histories are used to assess the MPP model. Satisfactory predictions are obtained of the excavation-induced wall deflection and ground surface settlement by finite element method (FEM) that incorporates the MPP model. The lateral soil deformation behind the wall can also be reasonably predicted. The simplified MPP model is shown to be effective for modeling the excavation-induced wall and ground movements.Key words: braced excavation, wall deflection, ground settlement, finite element method, stress-strain relationship, case histories.

Numerical Simulation of Triaxial Test in Clayey Soil Using Different Constitutive Relations

2011 ◽  
Vol 243-249 ◽  
pp. 2973-2977 ◽  
Author(s):  
Mohammed Y. Fattah ◽  
Firas A. Salman ◽  
Bestun J. Nareeman
Keyword(s):  
Clayey Soil ◽  
Triaxial Compression ◽  
Constitutive Relations ◽  
Triaxial Tests ◽  
Elastic Model ◽  
Residual Soils ◽  
Stress Strain ◽  
Linear Elastic ◽  
Modified Cam Clay ◽  
Cam Clay

The stress paths to which specimens are subjected in triaxial tests together with the yield surfaces, which may be exercised in different models of such a test are simulated. A laboratory testing on undisturbed clay soil samples was performed in order to characterize the stress-strain behaviour of the residual soils in Sao Paulo sedimentary deposit. The sample is tested under isotropically consolidated drained triaxial compression. Strain controlled procedure was used to simulate stress-strain relationships of the soil. Seven models are used; namely: linear elastic, Duncan-Chang hyperbolic, Mohr-Coulomb, Cam clay, modified Cam clay, new Mohr-Coulomb and Cap model. It was concluded that the results of Cam clay and Duncan Chang models are the closest to the experimental data under low confining pressures; 49 and 98 kPa. Both models exhibit parabolic stress-strain relationships while the linear elastic model results are far away from experimental ones especially at large stress levels. At high confining pressure; 196 kPa, the modified Cam clay best correlates the stress and strain.

Cord/Rubber Material Properties

1985 ◽  
Vol 58 (4) ◽  
pp. 830-856 ◽  
Author(s):  
R. J. Cembrola ◽  
T. J. Dudek
Keyword(s):  
Finite Element ◽  
Material Model ◽  
Rubber Composites ◽  
Stress Strain ◽  
Element Analysis ◽  
Rubber Layer ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Interlaminar Shear ◽  
Mechanics Of Composite Materials

Abstract Recent developments in nonlinear finite element methods (FEM) and mechanics of composite materials have made it possible to handle complex tire mechanics problems involving large deformations and moderate strains. The development of an accurate material model for cord/rubber composites is a necessary requirement for the application of these powerful finite element programs to practical problems but involves numerous complexities. Difficulties associated with the application of classical lamination theory to cord/rubber composites were reviewed. The complexity of the material characterization of cord/rubber composites by experimental means was also discussed. This complexity arises from the highly anisotropic properties of twisted cords and the nonlinear stress—strain behavior of the laminates. Micromechanics theories, which have been successfully applied to hard composites (i.e., graphite—epoxy) have been shown to be inadequate in predicting some of the properties of the calendered fabric ply material from the properties of the cord and rubber. Finite element models which include an interply rubber layer to account for the interlaminar shear have been shown to give a better representation of cord/rubber laminate behavior in tension and bending. The application of finite element analysis to more refined models of complex structures like tires, however, requires the development of a more realistic material model which would account for the nonlinear stress—strain properties of cord/rubber composites.

scholarly journals Experimental Investigation on the Behavior of Iron Powder-Reinforced Sand under Electromagnetic Field

2018 ◽  
Vol 2018 ◽  
pp. 1-15
Author(s):  
Ying Lai ◽  
Bin Zhu ◽  
Xiangtian Xu
Keyword(s):  
Electromagnetic Field ◽  
Iron Powder ◽  
Soil Improvement ◽  
Triaxial Tests ◽  
Future Research ◽  
Initial Stiffness ◽  
Stress Strain ◽  
Practical Applications ◽  
Nonlinear Stress ◽  
Chang Model

Applications of soil improvement have proliferated in recent years. To date, we have limited studies on the quantitative analyses of the autoadaptive material and specifically to model its stress-strain relationship. This paper explored an autoadaptive material, iron-powdered Ottawa sand, which was temporarily solidified by applying an electromagnetic field. A series of compression triaxial tests were carried out with various relative densities of specimens (60% and 80%), in four electromagnetic fields (0 A, 0.5 A, 1 A, and 2 A) and under three confining pressures (103 kPa, 206 kPa, and 310 kPa). The test results indicate that the strength of specimens increased while initial stiffness and brittleness reduced by adding iron powder. Moreover, the strength of the specimens increased by increasing the magnitude of the applied electromagnetic field. The behavior of the iron-powdered sand was described by using a revised Duncan–Chang model. The revised model was evaluated by comparing the simulated results with the corresponding test data. The comparison showed that the revised model can better capture the nonlinear stress-strain behavior of the specimens. With the application of the revised Duncan–Chang model, the standard error of the estimate between the experimental and predicted results is lowered down to 0.39 from 4.7. Future research is geared towards practical applications for temporary solidification of soil.

Duncan-Chang Nonlinear Elastic Model Considered Loess Structure

2011 ◽  
Vol 90-93 ◽  
pp. 176-181
Author(s):  
Chang Lu Chen ◽  
Sheng Jun Shao ◽  
Lin Ma
Keyword(s):  
Nonlinear Model ◽  
Stress Ratio ◽  
Structural Parameters ◽  
Strain Curve ◽  
Triaxial Tests ◽  
Model Parameters ◽  
Elastic Model ◽  
Stress Strain ◽  
Nonlinear Elastic ◽  
Intact Loess

Duncan-Chang nonlinear model has been modified and applied to the structural loess calculation. Based on structural studies and conventional triaxial tests, this paper has analyzed the mechanical properties of intact loess and the relationship between the stress ratio structural parameters and the strain, then the expression of generalized shear strain and stress ratio structural parameters are given to facilitate the engineering applications. On this basis, the stress-strain curve of intact loess was corrected by the use of the stress ratio structural parameters. The form of the intact loess stress-strain curves which have been revised has changed hardening from the softening or weak softening. The results show that the modified stress-strain curves of intact loess can apply Duncan- Chang nonlinear model to calculate and the model parameters are reasonable and effective. This method provides Duncan-Chang nonlinear model which is widely used in engineering with a new ways and means in intact structural loess application.

Parametric Variational Principle for Bi-Modulus Materials and Its Application to Nacreous Bio-Composites

2016 ◽  
Vol 08 (06) ◽  
pp. 1650082 ◽  
Author(s):  
Liang Zhang ◽  
Huiting Zhang ◽  
Jian Wu ◽  
Bo Yan ◽  
Mengkai Lu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Variational Principle ◽  
Principal Stress ◽  
Stress Strain ◽  
Element Analysis ◽  
Parametric Variational Principle ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Nonlinear Stress

Bi-modulus materials have different moduli in tension and compression and the stress–strain relation depends on principal stress that is unknown before displacement is determined. Establishment of variational principle is important for mechanical analysis of materials. First, parametric variational principle (PVP) is proposed for static analysis of bi-modulus materials and structures. A parametric variable indicating state of principal stress is included in the potential energy formulation and the nonlinear stress–strain relation is evolved into a linear complementarity constraint. Convergence of finite element analysis is thus improved. Then the proposed variational principle is extended to a dynamic problem and the dynamic equation can be derived based on Hamilton’s principle. Finite element analysis of nacreous bio-composites is performed, in which a unilateral contact behavior between two hard mineral bricks is modeled using the bi-modulus stress–strain relation. Effective modulus of composites can be determined numerically and stress mechanism of “tension–shear chain” in nacre is revealed. A delayed effect on stress propagation is found around the “gaps” between mineral bricks, when a tension force is loaded to nacreous bio-composites dynamically.

scholarly journals Stress–Strain Behavior of FRC in Uniaxial Tension Based on Mesoscopic Damage Model

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 689
Author(s):  
Weifeng Bai ◽  
Xiaofeng Lu ◽  
Junfeng Guan ◽  
Shuang Huang ◽  
Chenyang Yuan ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Uniaxial Tension ◽  
Damage Evolution ◽  
Constitutive Relations ◽  
Damage Mechanism ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Stress Strain ◽  
Strain Behavior ◽  
Nonlinear Stress

Fiber-reinforced concrete (FRC) is widely used in the field of civil engineering. However, the research on the damage mechanism of FRC under uniaxial tension is still insufficient, and most of the constitutive relations are macroscopic phenomenological. The aim is to provide a new method for the investigation of mesoscopic damage mechanism of FRC under uniaxial tension. Based on statistical damage theory, the damage constitutive model for FRC under uniaxial tension is established. Two kinds of mesoscopic damage mechanisms, fracture and yield, are considered, which ultimately determines the macroscopic nonlinear stress–strain behavior of concrete. The yield damage mode reflects the potential bearing capacity of materials and plays a key role in the whole process. Evolutionary factor is introduced to reflect the degree of optimization and adjustment of the stressed skeleton in microstructure. The whole deformation-to-failure is divided into uniform damage phase and local failure phase. It is assumed that the two kinds of damage evolution follow the independent triangular probability distributions, which could be represented by four characteristic parameters. The validity of the proposed model is verified by two sets of test data of steel fiber-reinforced concrete. Through the analysis of the variation law of the above parameters, the influence of fiber content on the initiation and propagation of micro-cracks and the damage evolution of concrete could be evaluated. The relations among physical mechanism, mesoscopic damage mechanism, and macroscopic nonlinear mechanical behavior of FRC are discussed.

Constitutive modelling of the mechanical response of a polycaprolactone based polyurethane elastomer: Finite element analysis and experimental validation through a bulge test

2020 ◽  
pp. 030932472095833
Author(s):  
Nahuel Rull ◽  
Asanka Basnayake ◽  
Michael Heitzmann ◽  
Patricia M. Frontini
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanical Response ◽  
Strain Curve ◽  
Image Correlation ◽  
Bulge Test ◽  
Polyurethane Elastomer ◽  
Stress Strain ◽  
Element Analysis ◽  
Nonlinear Stress

The mechanical behaviour of a high performance polycaprolactone based polyurethane elastomer (PCL) up to large strain levels, cyclic loading and equibiaxial stress has been assessed. The PCL can be categorised as a rubber-like material, thus, showing nonlinear stress-strain behaviour. The materials elastic network is based on a high molecular weight PCL polyol which gives the material its elastomeric behaviour similar to polyurethanes. In this work, mechanical testing capturing the major features of the stress-strain curve under different loading conditions is performed. Both, uni-axial loading-unloading curves and bulge test are thoroughly studied through the addition of digital image correlation (DIC) to measure the strain field. Results show the presence of hysteresis and loading configuration dependence. Then, two well-known hyperelastic constitutive models, the Arruda-Boyce eight-chain and Bergström-Boyce, were fitted to the uni-axial monotonic and cyclic test data and compared to the bulge test experimental results through finite element analysis (FEA) in Abaqus.

A finite element study of the pressuremeter test in sand using a nonlinear elastic plastic model

1993 ◽  
Vol 30 (2) ◽  
pp. 348-362 ◽  
Author(s):  
Martin Fahey ◽  
John P. Carter
Keyword(s):  
Finite Element ◽  
Shear Modulus ◽  
Hyperbolic Model ◽  
Type Model ◽  
Model Parameters ◽  
Nonlinear Behaviour ◽  
Stress Strain ◽  
Pressuremeter Test ◽  
Strain Behaviour ◽  
Highly Nonlinear

The stress–strain behaviour of sands is highly nonlinear, even at stresses well below the peak strength of the sand. The hyperbolic model is a reasonable conceptual model for representing the stress–strain behaviour of sand, but some empirical curve fitting is required to obtain a more realistic model for calculation purposes. This can readily be performed for reconstituted samples of sand using laboratory tests. Recent evidence shows that the stiffness of natural sands is often much greater than that of the same sand when reconstituted at the same density and stress state in the laboratory, and it is therefore necessary to use in situ testing methods to determine the stress–strain behaviour of such sands. In this paper, the finite element method is used to simulate pressuremeter tests in a soil modelled using a hyperbolic-type model. It concentrates on the behaviour in unload-reload loops, which are often included in pressuremeter tests to measure shear modulus. The effect on the whole unload-reload loop of varying some of the model parameters is examined. The results are compared with a high-quality pressuremeter test in sand. It is concluded that, though the results to date are encouraging, some further experimental work is required to verify some of the features of the model. Key words : pressuremeter test, hyperbolic model, nonlinear behaviour, initial shear modulus, sand behaviour.

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