scholarly journals Influence of Load Plates Diameters, Shapes of Columns and Columns Spacing on Results of Load Plate Tests of Columns Formed by Dynamic Replacement

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4868
Author(s):  
Sławomir Kwiecień
Keyword(s):  
Numerical Models ◽  
Constitutive Models ◽  
Isotropic Hardening ◽  
Load Testing ◽  
Perfectly Plastic ◽  
Replacement Method ◽  
Dynamic Replacement ◽  
Modified Cam Clay ◽  
Load Tests ◽  
Elastic Perfectly Plastic

The dynamic replacement method is used to strengthen the subgrade of objects, usually up to 5 to 6 m thick. After the improvement process, acceptance tests in the form of load testing are carried out. Interpretation of the test results can cause some difficulties. Dynamic replacement results in a situation where columns of different shapes, loaded with plates of diameters usually smaller than the head diameter and in the vicinity of adjacent columns, are subjected to load tests. In order to demonstrate the influence of these factors, a spatial model of soil strengthened by dynamic replacement, comprising four material zones, was calibrated on the basis of load testing. The following models were used in the analysis: linear-elastic, elastic–perfectly plastic (Coulomb–Mohr) and elastic–plastic with isotropic hardening (Modified Cam-Clay). This formed the basis for 105 numerical models, which took into account the actual shapes of the columns made at various spacings, subjected to load tests with plates of various diameters. The analyses of the settlements, calculated moduli and stress distribution in the loaded system showed how the results were significantly influenced by mentioned factors. This implies that the interpretation of the results of load tests should be based on advanced spatial numerical analyses, using appropriate constitutive models and including the considered factors.

scholarly journals The influence of loading plate diameter on the results of trial load tests of dynamic replacement columns

2017 ◽  
Vol 2017 (5) ◽  
pp. 1-9
Author(s):  
Sławomir Kwiecień
Keyword(s):  
Numerical Model ◽  
Bearing Capacity ◽  
Deformation Modulus ◽  
Isotropic Hardening ◽  
Replacement Method ◽  
Dynamic Replacement ◽  
Load Tests

The dynamic replacement method of soil strengthening consists in the constructing columns made of aggregate of various granularity. In order to form them, heavy pounders (weighing from 10 to 20 tonnes) are dropped from the height of 25 m. Considering the specificity of this technique, it is quite important to verify on site the assumptions of the project, such as diameter and length of columns, their compaction or stiffness. For that reason, a number of examinations are performed, including column excavations, various types of probing tests or trial loads. The latter consists in determining the “load-settlement” dependence - usually during initial and secondary loadings phase – and on their basis, indicating the value of deformation modulus. Therefore, a stiff plate is placed on the column head and the loading is realised using actuators leaning on the ballast. The diameter of the loading plate depends on diameter and length of column and on the predicted pressure under the plate. The diameter of the loading plate is often smaller than column's diameter. This paper tries to determine the influence of the diameter of the plate used in test loads on the result of the research presented as “load-settlement” dependence and on the values of deformation modulus determined on their basis. The calculations were performed using FEM on a spatial numerical model calibrated on the basis of column's bearing capacity tests. Two models were applied in calculations: elastic-ideally plastic and isotropic hardening elastoplastic.

scholarly journals Settlement analysis of friction piles in consolidating soft soils

DYNA ◽  
2015 ◽  
Vol 82 (192) ◽  
pp. 211-220 ◽  
Author(s):  
Juan Félix Rodríguez Rebolledo ◽  
Gabriel Y. Auvinet-Guichard ◽  
Hernán E. Martínez-Carvajal
Keyword(s):  
Mexico City ◽  
Numerical Models ◽  
Constitutive Models ◽  
Pile Group ◽  
Soil Consolidation ◽  
Soft Clays ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Anisotropic Yielding ◽  
Long Term Behavior

The paper shows how axisymmetric finite element numerical models can be used to optimize the design of friction piles foundations in an environment that is prone to regional subsidence. The study considers friction piles in typical Mexico City soft clays, that are subjected to external loads and soil consolidation due to variations in piezometric conditions. The constitutive models used to numerically simulate the behavior of the clays vary from a basic elastic perfectly-plastic model to a critical state model that is able to account for the anisotropic yielding behavior of Mexico City clay. The simulations consider the long term behavior of the internal piles within a large pile group.

scholarly journals A FEM analysis of the settlement of a tall building situated on loess subsoil

2020 ◽  
Vol 10 (1) ◽  
pp. 519-526
Author(s):  
Krzysztof Nepelski
Keyword(s):  
Fem Analysis ◽  
Actual Process ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Modified Cam Clay ◽  
Linear Behaviour ◽  
Subsequent Calculation ◽  
Elastic Perfectly Plastic ◽  
Subsoil Model ◽  
Storey Building

AbstractIn order to correctly model the behaviour of a building under load, it is necessary to take into account the displacement of the subsoil under the foundations. The subsoil is a material with typically non-linear behaviour. This paper presents an example of the modelling of a tall, 14-storey, building located in Lublin. The building was constructed on loess subsoil, with the use of a base slab. The subsoil lying directly beneath the foundations was described using the Modified Cam-Clay model, while the linear elastic perfectly plastic model with the Coulomb-Mohr failure criterion was used for the deeper subsoil. The parameters of the subsoil model were derived on the basis of the results of CPT soundings and laboratory oedometer tests. In numerical FEM analyses, the floors of the building were added in subsequent calculation steps, simulating the actual process of building construction. The results of the calculations involved the displacements taken in the subsequent calculation steps, which were compared with the displacements of 14 geodetic benchmarks placed in the slab.

On instability of constitutive models for isotropic elastic-perfectly plastic material behaviour at finite deformations

2020 ◽  
pp. 095440622092068
Author(s):  
Marina Trajković-Milenković ◽  
Otto T Bruhns ◽  
Andrija Zorić
Keyword(s):  
Plastic Material ◽  
Constitutive Relations ◽  
Relevant Literature ◽  
Constitutive Models ◽  
Constitutive Law ◽  
Elastoplastic Deformations ◽  
Perfectly Plastic ◽  
User Subroutine ◽  
Shear Problem ◽  
Elastic Perfectly Plastic

The main goal of this work is to test the possibility of a newly introduced constitutive law to model the behaviour of the isotropic elastic-perfectly plastic material which is exposed to large elastoplastic deformations. The proposed constitutive relation is based on the hypo-elastic relation and the inelastic INTERATOM model. The verification of the model is done by its implementation into the commercial software ABAQUS/Standard via the user subroutine UMAT. For that purpose, the large simple shear problem is studied where selected objective corotational rates, i.e. the logarithmic rate, the Jaumann rate and the Green-Naghdi rate, are individually implemented in the aforementioned constitutive relations. The obtained results are compared mutually and with the relevant literature. The proposed constitutive model is also used to test the behaviour of the part of a real engineering structure, i.e. a seismic isolator, in order to obtain the correct input data for further analysis of superstructure behaviour due to seismic excitation.

scholarly journals Numerical analysis of settlement of a high-rise building using two constitutive soil models

2019 ◽  
Vol 262 ◽  
pp. 04002
Author(s):  
Leszek Chomacki
Keyword(s):  
Numerical Analysis ◽  
Constitutive Models ◽  
Soil Parameters ◽  
Geotechnical Parameters ◽  
High Rise ◽  
High Rise Building ◽  
Perfectly Plastic ◽  
Calculation Process ◽  
Elastic Perfectly Plastic ◽  
Key Parameter

One of the basic roles of foundations is to safely transfer loads from the structure to the subsoil in a controlled manner. Often a key parameter in deciding whether the foundation was designed correctly is the value of settlement of the building and the ground around it. This paper attempts to numerically reproduce the measured settlement of a high-rise building using geotechnical parameters already available. For this purpose, numerical calculations were carried out using two constitutive soil models: the elastic-perfectly plastic model with Mohr-Coulomb plastic criteria (MC) model and the Hardening Soil (HS) model. The resulting settlement values were compared with surveying measurements taken during and after the building’s construction. In the summary the results obtained with the use of different constitutive models, the calculation process and the adopted soil parameters are analysed and discussed.

Buckle Propagation Analysis of Deep-Water Petroleum Transmission Pipelines with Axial Tension

2014 ◽  
Vol 1008-1009 ◽  
pp. 1134-1143 ◽  
Author(s):  
Sun Ting Yan ◽  
Yin Fa Zhu ◽  
Zhi Jiang Jin ◽  
Hao Ye
Keyword(s):  
Plastic Hinge ◽  
External Pressure ◽  
Isotropic Hardening ◽  
Rigid Plastic ◽  
Perfectly Plastic ◽  
Fitting Procedure ◽  
Plastic Materials ◽  
Buckle Propagation ◽  
Elastic Perfectly Plastic ◽  
Hinge Model

Quasi-static finite element simulation is carried out on buckle propagation phenomenon of offshore pipelines under external pressure. Arc-length method and volume-controlled static analysis by employing hydrostatic fluid element F3D4 are employed to calculate the steady buckle propagation pressure. After verifying the validity of numerical model, emphasis is on the influence of tension on propagation pressure considering isotropic hardening elastoplastic and elastic-perfectly plastic materials. Parametric study is conducted to include the effect of diameter-thickness ratio, after which two empirical equations are derived by curve fitting procedure. Finally, some comments on the results obtained through rigid-plastic hinge model are presented and a modified plastic hinge model including effect of material anisotropy is derived. The results can serve as a reference for more reasonable design of buckle arrestors.

An Improved Thermo-Ratcheting Boundary of Pressure Pipeline

2016 ◽  
Vol 725 ◽  
pp. 311-315
Author(s):  
Qian Hua Kan ◽  
Jian Li ◽  
Han Jiang ◽  
Guo Zheng Kang
Keyword(s):  
Mechanical Stress ◽  
Nuclear Power ◽  
Kinematic Hardening ◽  
Constitutive Models ◽  
Plastic Strain Increment ◽  
Perfectly Plastic ◽  
Axial Tensile ◽  
Thermal Ratcheting ◽  
Pressure Pipeline ◽  
Elastic Perfectly Plastic

The thermal ratcheting boundary of pressure pipeline is a popular topic in nuclear power engineering. The existed thermal ratcheting boundary based on the Bree diagram is conservative for structures subjected to the thermo-mechanically coupled loadings since it was obtained only from an elastic-perfectly plastic model. Therefore, it is necessary to improve the existed thermal ratcheting boundary based on a reasonable constitutive model. The Bree diagram was validated firstly by the linear relationship between the plastic strain increment and mechanical stress by finite element method. And then the influences of different constitutive models, such as elastic-perfectly plastic, multi-linear kinematic hardening, Chaboche and Abdel Karim-Ohno models, on the thermal ratcheting boundary of pressure pipeline were investigated numerically. It is found that the elastic-perfectly plastic and multi-linear kinematic hardening models provide the lower and upper bounds for the thermal ratcheting boundary, respectively. Finally, an improved thermal ratcheting boundary by introducing the dimensionless axial tensile stress was proposed based on the Bree diagram, the improved thermal ratcheting boundary covered the present cases with different ratios of mechanical stress over thermal stress.

scholarly journals The influence of the soil constitutive models on the seismic analysis of pile-supported wharf structures with batter piles in cut-slope rock dike

2020 ◽  
Vol 42 (3) ◽  
pp. 191-209
Author(s):  
Lylia Deghoul ◽  
Smail Gabi ◽  
Adam Hamrouni
Keyword(s):  
Constitutive Models ◽  
Small Strain ◽  
Loose Sand ◽  
Cut Slope ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Soil Constitutive Models ◽  
Elastic Perfectly Plastic ◽  
Batter Piles ◽  
Hardening Soil Model

AbstractIn coastal regions, earthquakes caused severe damage to marine structures. Many researchers have conducted numerical investigations in order to understand the dynamic behavior of these structures. The most frequently used model in numerical calculations of soil is the linear-elastic perfectly plastic model with a Mohr-Coulomb failure criterion (MC model). It is recommended to use this model to represent a first-order approximation of soil behavior. Therefore, it is necessary to accommodate soil constitutive models for the specific geotechnical problems.In this paper, three soil constitutive models with different accuracy were applied by using the two-dimensional finite element software PLAXIS to study the behavior of pile-supported wharf embedded in rock dike, under the 1989 Loma Prieta earthquake. These models are: a linear-elastic perfectly plastic model (MC model), an elastoplastic model with isotropic hardening (HS model), and the Hardening Soil model with an extension to the small-strain stiffness (HSS model).A typical pile-supported wharf structure with batter piles from the western United States ports was selected to perform the study. The wharf included cut-slope (sliver) rock dike configuration, which is constituted by a thin layer of rockfill overlaid by a slope of loose sand. The foundation soil and the backfill soil behind the wharf were all dense sand. The soil parameters used in the study were calibrated in numerical soil element tests (Oedometer and Triaxial tests).The wharf displacement and pore pressure results obtained using models with different accuracy were compared to the numerical results of Heidary-Torkamani et al.[28] It was found that the Hardening Soil model with small-strain stiffness (HSS model) gives clearly better results than the MC and HS models.Afterwards, the pile displacements in sloping rockfill were analyzed. The displacement time histories of the rock dike at the top and at the toe were also exposed. It can be noted that during the earthquake there was a significant lateral ground displacement at the upper part of the embankment due to the liquefaction of loose sand. This movement caused displacement at the dike top greater than its displacement at the toe. Consequently, the behavior of the wharf was affected and the pile displacements were important, specially the piles closest to the dike top.

STRAIN EFFICIENCY OF FRP JACKETS IN FRP-CONFINED CONCRETE-FILLED CIRCULAR STEEL TUBES

2012 ◽  
Vol 12 (01) ◽  
pp. 75-94 ◽  
Author(s):  
S. Q. LI ◽  
J. F. CHEN ◽  
L. A. BISBY ◽  
Y. M. HU ◽  
J. G. TENG
Keyword(s):  
Constitutive Models ◽  
Confined Concrete ◽  
Test Results ◽  
Hoop Strain ◽  
Steel Tubes ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Adhesive Model ◽  
Concrete Filled Steel Tubes ◽  
Rupture Strain

The confinement of concrete columns using fiber-reinforced polymer (FRP) jackets or wraps is a popular structural retrofitting technique. More recently, the benefits of FRP confinement of concrete-filled steel tubes have also been explored by researchers. Failure of such FRP-confined concrete-filled steel tubes is usually governed by the rupture of the FRP jacket in the hoop direction. However, the observed FRP hoop strain at failure (i.e. the hoop rupture strain) is typically lower than the ultimate tensile strain from a flat coupon test. Many factors may contribute to this phenomenon, one of which is the geometrical discontinuities at both the starting and finishing ends of the wrapping process commonly used to form an FRP jacket. This paper examines the effect of these geometrical discontinuities on the hoop rupture strain of FRP jackets in FRP-confined concrete-filled circular steel tubes. Detailed finite element (FE) analyses conducted using both linear elastic and elastic-perfectly plastic adhesive constitutive models are presented. Comparison between the FE predictions and available test results shows that the hoop rupture strains of FRP jackets predicted by FE analysis using an elastic-perfectly plastic adhesive model are in reasonable agreement with the test results. The influence of parameters such as the FRP thickness, FRP orthotropy, FRP elastic modulus, adhesive yield strength, adhesive thickness, and column size are examined.

Finite Element Based Unloading of an Elastic Plastic Spherical Stick Contact for Varying Tangent Modulus and Hardening Rule

2013 ◽  
Vol 1 (1) ◽  
pp. 13-32
Author(s):  
Biplab Chatterjee ◽  
Prasanta Sahoo
Keyword(s):  
Finite Element ◽  
Plastic Material ◽  
Kinematic Hardening ◽  
Tangent Modulus ◽  
Isotropic Hardening ◽  
Finite Element Software ◽  
Perfectly Plastic ◽  
Hardening Models ◽  
Qualitative Similarity ◽  
Elastic Perfectly Plastic

Loading-unloading behavior of a deformable sphere with a rigid flat under full stick contact condition is investigated for varying strain hardening. The study considers various tangent modulus using the finite element software ANSYS. Both the bilinear kinematic hardening and isotropic hardening models are considered. Numerical simulation reveals the qualitative similarity between kinematic and isotropic hardening regarding the variation of interfacial parameters during loading-unloading for various tangent modulus. It is found that the material with kinematic hardening dissipates more energy than the material with isotropic hardening during unloading. However for elastic perfectly plastic material, the loading-unloading behavior is insensitive to hardening model.

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