scholarly journals Parallel Finite Element Model for Multispecies Transport in Nonsaturated Concrete Structures

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2764 ◽  
Author(s):  
Okpin Na ◽  
Yunping Xi
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Model Prediction ◽  
Concrete Structures ◽  
Ionic Transport ◽  
Ionic Species ◽  
Chloride Ions ◽  
Moisture Movement ◽  
Parallel Finite Element ◽  
Saturated Concrete

The chloride-induced corrosion of steel reinforcement embedded in concrete is undoubtedly one of the most important durability problems of reinforced concrete structures. The chloride ions as well as other ionic species (Na+, Ca2+, K+, OH−) come from various deicing salts and they are transported from the environment into concrete. To investigate the transport mechanism of the multispecies, complex scientific methods and accurate mathematical models are needed. The purpose of this study is to develop a more robust mathematical model and better computational technique to characterize the coupled effect of ionic transport mechanisms as well as the influence of interaction of ionic species. The new mathematical model was developed based on the Nernst–Planck equation and null current condition to solve the ionic-induced electrostatic potential, and the model was implemented by a parallel finite element algorithm. The verification of mathematical model was done by comparing the model prediction with experimental results for ionic transport in saturated concrete. The comparisons showed good results. The model prediction of the multispecies transport in partially saturated concrete demonstrated that the ionic species dissolved in pore solution could be carried by the moisture movement and pressure gradient. Therefore, the multispecies transport model based on the parallel finite element method is effective, accurate, and can be used for solving the partial differential equations for ionic species transport in concrete.

Simulation of the Effect of Solar Radiation on Hardening and Hardened Concrete Wall

2010 ◽  
Vol 163-167 ◽  
pp. 1489-1494
Author(s):  
Dong Hui Huang ◽  
Sheng Xing Wu ◽  
Hai Tao Zhao
Keyword(s):  
Mathematical Model ◽  
Finite Element Method ◽  
Finite Element ◽  
Thermal Stress ◽  
Solar Radiation ◽  
Numerical Models ◽  
Concrete Structures ◽  
Heat Of Hydration ◽  
Hardened Concrete ◽  
Concrete Wall

The purpose of the present study is to assess the effect of solar radiation on the development of thermal stress in hardening and hardened concrete structures. A mathematical model for solar radiation is investigated. A finite element method program is developed for the temperature and thermal stress analysis including the heat of hydration, creep, shrinkage, and ambient temperature, especially the solar radiation. Meanwhile, the effect of solar radiation on the concrete wall during its service life is considered. The results obtained from the numerical models show that for the hardening concrete wall, solar radiation reduce the stress at the first 36 hours on surface and first 48 hours in the center of the wall, after that the stresses both on surface and in the center of the wall increases quickly; for the hardened concrete wall, solar radiation increase the stress in the center of the wall. This program is useful to estimate the stress development and the effect of the solar radiation on the hardening and hardened concrete structures.

scholarly journals A Research About One-dimensional Chloride Ion Erosion In Concrete Under Drying-wetting Cycles

2021 ◽  
Vol 272 ◽  
pp. 01020
Author(s):  
Hang Shen ◽  
Jinyuan Li ◽  
Changyuan Chen ◽  
Yongli Li ◽  
Wenjun Ji
Keyword(s):  
Concrete Structures ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Marine Resources ◽  
One Dimensional ◽  
Service Environment ◽  
Tidal Stream ◽  
Saturated Concrete ◽  
The One ◽  
Ion Erosion

Reinforced concrete structures are now widely used in China, and with the exploitation of marine resources, many concrete structures are in a relatively harsh service environment. Concrete in wave and tidal stream areas is in a dry and wet cycle state. When unsaturated concrete is in a dry and wet cycle state, chloride ions will invade the concrete by diffusion and convection, which accelerates the erosion of the reinforcement within the concrete and degrades the concrete performance. Therefore, the study of chloride ion erosion in concrete under dry and wet cycles is particularly important. Fick’s law is a good predictor of the diffusion of chloride ions in saturated concrete with stable boundaries, but it is difficult to obtain satisfactory results for concrete under dry and wet cycles. There are many difficult parameters in the microscopic model that make programming the calculations more difficult. In this paper, we propose to use the radial basis function matching point method to solve the problem. It is found that the error is within acceptable limits and can be used to calculate the one-dimensional erosion of chloride ions under dry and wet cycles through solving the validation algorithm.

An Eight-Node Hexahedral Finite Element with Rotational DOFs for Elastoplastic Applications

2019 ◽  
Vol 11 (1) ◽  
pp. 54-66
Author(s):  
Ayoub Ayadi ◽  
Kamel Meftah ◽  
Lakhdar Sedira ◽  
Hossam Djahara
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Plastic Zone ◽  
Displacement Vector ◽  
Small Strain ◽  
Benchmark Problems ◽  
Plasticity Model ◽  
Vector Approximation ◽  
Calculation Code

Abstract In this paper, the earlier formulation of the eight-node hexahedral SFR8 element is extended in order to analyze material nonlinearities. This element stems from the so-called Space Fiber Rotation (SFR) concept which considers virtual rotations of a nodal fiber within the element that enhances the displacement vector approximation. The resulting mathematical model of the proposed SFR8 element and the classical associative plasticity model are implemented into a Fortran calculation code to account for small strain elastoplastic problems. The performance of this element is assessed by means of a set of nonlinear benchmark problems in which the development of the plastic zone has been investigated. The accuracy of the obtained results is principally evaluated with some reference solutions.

Modal Analysis of the Axial Compressor Blade: Advanced Time-Dependent Electronic Interferometry and Finite Element Method

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Mykhaylo Tkach ◽  
Serhii Morhun ◽  
Yuri Zolotoy ◽  
Irina Zhuk
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Finite Element ◽  
High Reliability ◽  
Axial Compressor ◽  
Time Dependent ◽  
Experimental Setup ◽  
Vibration Modes ◽  
Compressor Blades ◽  
Isoparametric Finite Element

AbstractNatural frequencies and vibration modes of axial compressor blades are investigated. A refined mathematical model based on the usage of an eight-nodal curvilinear isoparametric finite element was applied. The verification of the model is carried out by finding the frequencies and vibration modes of a smooth cylindrical shell and comparing them with experimental data. A high-precision experimental setup based on an advanced method of time-dependent electronic interferometry was developed for this aim. Thus, the objective of the study is to verify the adequacy of the refined mathematical model by means of the advanced time-dependent electronic interferometry experimental method. The divergence of the results of frequency measurements between numerical calculations and experimental data does not exceed 5 % that indicates the adequacy and high reliability of the developed mathematical model. The developed mathematical model and experimental setup can be used later in the study of blades with more complex geometric and strength characteristics or in cases when the real boundary conditions or mechanical characteristics of material are uncertain.

Tissue necrosis and passage of fluid due to cold stress from the thermally damaged human body peripherals: A mathematical model

2015 ◽  
Vol 04 (02) ◽  
pp. 1550012
Author(s):  
M. A. Khanday ◽  
Fida Hussain ◽  
Khalid Nazir
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Heat Equation ◽  
Cold Stress ◽  
Human Body ◽  
Human Subjects ◽  
Diffusion Equations ◽  
Tissue Necrosis ◽  
Cold Temperatures ◽  
Element Technique

The development of cold injury takes place in the human subjects by means of crystallization of tissues in the exposed regions at severe cold temperatures. The process together with the evaluation of the passage of fluid discharge from the necrotic regions with respect to various degrees of frostbites has been carried out by using variational finite element technique. The model is based on the Pennes' bio-heat equation and mass diffusion equations together with suitable initial and boundary conditions. The results are analyzed in relation with atmospheric temperatures and other parameters of the tissue medium.

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