A one–dimensional elasto-viscoplastic macro-element model for creep analysis of shallow foundations on sand

2022 ◽  
Vol 142 ◽  
pp. 104561
Author(s):  
Bo Liu ◽  
Barry M. Lehane ◽  
Jianfeng Xue
2021 ◽  
Author(s):  
Sara Hamidpour ◽  
Hamzeh Shakib ◽  
Roberto Paolucci ◽  
António Correia ◽  
Masoud Soltani

Abstract This paper aims to introduce a simplified moment-rotation backbone model for exploring the nonlinear behavior of shallow foundations subjected to rocking. The model is developed based on parametric numerical investigations of rectangular footings on dense dry sand, taking advantage of a nonlinear macro-element model verified based on a set of experimental results. Empirical expressions are proposed for rocking stiffness degradation due to gravity loads and foundation rotation as a function of the factor of safety against vertical loads and aspect ratio of foundations. Similar to previous researches, the uplift reference rotation was introduced to explore a new closedform expression appropriate for normalizing the foundation response in a non-dimensional form. The proposed approach for stiffness degradation and nonlinear backbone model of rocking foundations aims to be simple, to minimize the dependence on the variable parameters, and to provide physically sound selections for engineering applications.


2021 ◽  
Vol 9 (2) ◽  
pp. 199
Author(s):  
Anderson Peccin da Silva ◽  
Andrea Diambra ◽  
Dimitris Karamitros ◽  
Shiao Huey Chow

This paper presents a new macro-element modelling framework for plate anchors which enables the effect of pore water pressure changes and the related evolution of soil strength during the process of cyclic loading and consolidation to be captured. The proposed modelling framework combines an advanced macro-element model for plate anchors, expanded to capture the cyclic loading behaviour, with a simple one-dimensional model of undrained shearing and consolidation for a soil element representative of the whole soil mass around the anchor. The representative soil element tracks the effects of changes in effective stress on the soil strength, which in turn governs the anchor capacity in the macro-element model. The two modelling components are linked through a mobilised capacity compatibility condition. It will be firstly shown that such modelling framework is able to capture the expected changes in an anchor’s capacity related to cyclic pore pressure generation and consolidation under one-dimensional cyclic loading of the anchor. Then, the model will be used to explore the plate anchor’s behaviour and failure mechanisms under loading conditions which mobilise its full three-dimensional cyclic loading capacity. The macro-element model will identify some conflicting mechanisms (i.e., the anchor’s kinematic/rotation and soil weakening/strengthening) governing the three-dimensional capacity of the anchor.


Author(s):  
Lun Qiu ◽  
John Zhang

The fluid barrier in an unbonded flexible pipe seals the pressure from the internal fluid. Since the barrier is usually made of polymer materials, it is unable to hold the pressure by itself. A metal reinforced hoop layer is usually needed outside the barrier layer in order to resist the pressure. The hoop layer is usually a steel bar with a cross-section of an irregular shape. It is helically wrapped at the outside of the barrier layer. When the pipe is pressurized, the barrier will be supported by the hoop reinforcement layer from outside. However, at the gap between the steel wraps where the barrier layer bridges, material of the barrier will be forced to extrude into the gap. The amount of the extrusion is a function of many parameters such as temperature, material property, and internal pressure and so on. In addition, it is time dependent. The creep effect needs be considered. It is critical to have a proper barrier design for a flexible pipe structure. This article presents a practical finite element method for evaluation of the barrier/gap design. The creep behavior of the polymers is multi-parameter related. Therefore, a series of material tests has been conducted under various stresses and temperatures for nylon, polyethylene and Polyvinylidene Fluoride. In this work a method is given to determine the creep behavior parameters through parameter matching based on the tests. The creep deformation of barrier was analyzed with a finite element model using these parameters.


2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Y. Alsaffar ◽  
O. Aldraihem ◽  
A. Baz

Abstract A comprehensive theoretical and experimental study is presented of the bandgap behavior of periodic viscoelastic material (VEM) composites subjected to impact loading. The composites under consideration consist of an assembly of aluminum sections integrated with periodic inserts which are arranged in one-dimensional configurations. The investigated inserts are manufactured either from VEM only or VEM with local resonators (LR). A finite element model (FEM) is developed to predict the dynamics of this class of VEM composites by integrating the dynamics of the solid aluminum sections with those of VEM using the Golla-Hughes-Mctavish (GHM) mini-oscillator approach. The integrated model enables, for the first time, the accurate predictions of the bandgap characteristics of periodic viscoelastic composites unlike previous studies where the viscoelastic damping is modeled using the complex modulus approach with storage modulus and loss factor are assumed constants and independent of the frequency or the unrealistic and physically inaccurate Kelvin–Voigt viscous-damping models. The predictions of the developed FEM are validated against the predictions of the commercial finite element package ansys. Furthermore, the FEM predictions are checked experimentally using prototypes of the VEM composites with VEM and VEM/LR inserts. Comparisons are also established against the behavior of plain aluminum rods in an attempt to demonstrate the effectiveness of the proposed class of composites in mitigation of the structural response under impact loading. Close agreements are demonstrated between the theoretical predictions and the obtained experimental results.


Author(s):  
Thomas Barilero ◽  
Thomas Le Saux ◽  
Ludovic Julien ◽  
Vincent Croquette ◽  
Pierre-Olivier Chapuis ◽  
...  

Ion beam etching (IBE) was used to microfabricate resistive heaters in indium-tin-oxide (ITO). The device was then closed with a microfluidic chamber and its thermal behavior was investigated using the 3ω method. Experiments and finite element model (FEM) simulations both satisfactorily agreed with a simple one-dimensional model for heat diffusion.


2019 ◽  
Vol 92 ◽  
pp. 16009
Author(s):  
Anderson Peccin Da Silva ◽  
Andrea Diambra ◽  
Dimitris Karamitros

This work presents a new macro-element model to predict the behaviour of Suction Embedded Plate Anchors (SEPLAs) for floating offshore structures during keying and loading stages. Differently from previously published models for anchors, this new model is characterised by (i) a non-associated plastic potential with the aim of improving the prediction of anchor trajectory for the whole displacement domain and for a large range of padeye offsets; and (ii) by a strain-hardening rule enabling to predict the force and displacement mobilisation from the early stages of the keying process. The model was calibrated against LDFE analyses and compared with a broad set of LDFE and centrifuge tests results. The model proves capable of reproducing anchor rotation and displacement with good accuracy for a wide range of padeye offsets and distinct studies from the literature.


2012 ◽  
Vol 529 ◽  
pp. 220-223 ◽  
Author(s):  
Jun Feng Wang ◽  
Kang Sun

With the rotor structure ofturbopump, using a one-dimensional finite element method, considering the mass of shaft, gyroscopic effect and influence of shearing deformation,establishedtheone-dimensional rotor dynamics finite element model, calculated its six rank of the critical speed, and compared the gyroscopic effect and mass of shaft to the influence of the critical speed turbopump, and the results show that, considering the mass of shaft there is a slight decrease of critical speed value, and gyroscopic effect on critical speed calculation has a significant effect, therefore, gyroscopic effect must be considered in the design of turbopumps.


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