scholarly journals Rigorous Estimates for Effective Creep-coefficients of Microcracked Masonry Accounting for Cracks Interactions

2020 ◽  
Author(s):  
Amna Rekik
Keyword(s):  
Finite Elements ◽  
Effective Properties ◽  
Crack Density ◽  
Homogenization Method ◽  
Masonry Wall ◽  
Creep Function ◽  
Proposed Model ◽  
Brick And Mortar ◽  
Fracture Theory ◽  
Homogenization Scheme

Based on the association of finite elements homogenization method and a rigorous homogenization scheme accounting for crack interactions, this paper provides rigorous predictions for the local and effective properties of microcracked viscoelastic masonry with or without creep of bricks. For the sake of simplicity, viscoelastic brick and mortar are assumed to follow the Generalized Maxwell rheological model and to be respectively safe and microcracked. In the mortar, the distribution of microcracks orientations is assumed to be random. Two steps are followed. The first one is based on the identification at the short and long terms of an approximate analytical creep function for the mortar. This step relies on the coupling between the Griffith’s brittle fracture theory and a rigorous homogenization scheme - the Ponte Castañeda & Willis model - accounting for crack interaction instead of the dilute scheme adopted previously in Rekik et al. Two cases are considered: open and closed cracks. The first step allows to avoid recourse to 'heavy' numerical inversion of the Laplace-Carson transform. The second one provides overall creep coefficients of masonry by means of periodic homogenization carried out by finite elements method. For open cracks state, time-dependent crack density is investigated. The proposed model is validated by comparison with an analytical one available for a compressed masonry wall with "standard" viscoelastic mortar joints. Effect induced by microcracks is also highlighted by comparison with uncracked masonry. At last, results provided by the proposed model can be considered to be rigorous solution improving on dilute estimates for the creep behavior of microcracked mortar and demonstrating the interest to not neglect both cracks interactions and creep of bricks units. 

Convergence–confinement analysis of a bolt-supported tunnel using the homogenization method

2006 ◽  
Vol 43 (5) ◽  
pp. 462-483 ◽  
Author(s):  
Henry Wong ◽  
Didier Subrin ◽  
Daniel Dias
Keyword(s):  
Input Parameter ◽  
Uniaxial Stress ◽  
Homogenization Method ◽  
External Input ◽  
Proposed Model ◽  
Homogenization Approach ◽  
Parametric Studies ◽  
Perfect Bonding ◽  
The Moment ◽  
Grouted Bolts

The behaviour of tunnels reinforced with radially disposed fully grouted bolts is investigated in this paper. Perfect bonding and ideal diffusion of bolt tension are assumed, so that the bolt tension can be assimilated to an equivalent uniaxial stress tensor. An analytical model of the convergence–confinement type is proposed that accounts for the delayed action of bolts due to ground decompression prior to bolt installation. This factor leads to nonsimultaneous yielding, and more generally, a different stress history for each constituent, requiring special treatments in the incremental elastoplasticity calculations. Nonetheless, the resulting model remains sufficiently simple, and an analytical solution is still accessible. Charts are provided to allow for parametric studies and quick preliminary designs. Comparisons with 3D numerical calculations show that the model gives precise results if the correct convergence at the moment of bolt installation is used as an "external" input parameter, validating the homogenization approach. An approximate methodology based on previous works is proposed to determine this parameter to render the proposed model "self-sufficient." Its predictions are again compared to 3D numerical computations, and the results are found to be sufficiently accurate for practical applications.Key words: reinforcement, anisotropy, analytical, lining, yield, elastoplasticity.

scholarly journals Numerical Estimation of Effective Properties of Periodic Cellular Structures using Beam and Shell Finite Elements with CAE Fidesys

2019 ◽  
Vol 20 (2) ◽  
pp. 528-541
Author(s):  
Vladimir Anatolyevich Levin ◽  
Konstasntin Moiseevich Zingerman ◽  
Maksim Yakovlevich Yakovlev ◽  
Ekaterina Olegovna Kurdenkova ◽  
Diana Vladimirovna Nemtinova
Keyword(s):  
Finite Elements ◽  
Effective Properties ◽  
Cellular Structures ◽  
Numerical Estimation

NUMERICAL PREDICTION OF STIFFNESS DEGRADATION OF THIN-PLY CFRP LAMINATES UNDER FATIGUE LOADING

2021 ◽  
Author(s):  
RYOMA AOKI ◽  
RYO HIGUCHI ◽  
TOMOHIRO YOKOZEKI
Keyword(s):  
Composite Laminates ◽  
Damage Mechanics ◽  
Crack Density ◽  
Continuum Damage Mechanics ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Cfrp Laminates ◽  
Mechanics Model ◽  
Element Simulation ◽  
Proposed Model

This study aims to conduct a fatigue simulation for predicting the stiffness degradation of thin-ply composite laminates with several ply thicknesses. For the simulation, a fatigue evolution model of intra-laminar damage in thin-ply composite laminates considering the effect of ply thickness was proposed. The intra-laminar damage evolution was modeled using the continuum damage mechanics model and the static and fatigue evolution law were formulated by relating the transverse crack density to the damage variable. The finite element simulation using the proposed model was conducted to predict the stiffness degradation of the laminates as a function of the number of loading cycles. The simulation results show that the experimental data can be reproduced by using the proposed fatigue model.

Application of Continuous Thermodynamics Method to Fuel Droplet Evaporation

2012 ◽  
Author(s):  
Way Lee Cheng ◽  
Cai Shen ◽  
Chia-fon F. Lee
Keyword(s):  
Liquid Phase ◽  
Effective Properties ◽  
Liquid Mixtures ◽  
Droplet Evaporation ◽  
Distribution Functions ◽  
Homogeneous Groups ◽  
Novel Approach ◽  
Proposed Model ◽  
Complex Liquid

A finite diffusion droplet evaporation model for complex liquid mixture composed of different homogeneous groups is presented in this paper. Separate distribution functions are used to describe the composition of each homogeneous group in the mixture. Only a few parameters are required to describe the mixture. Quasi-steady assumption is applied in the determination of evaporation rates and heat flux to the droplet, and the effects of surface regression, finite diffusion and preferential vaporization of the mixture are included in the liquid phase equations using an effective properties approach. A novel approach was used to reduce the transport equations for the liquid phase to a set of ordinary differential equations. The proposed model is capable in capturing the vaporization characteristics of complex liquid mixtures.

scholarly journals Experimental and Numerical Study of Behaviour of Reinforced Masonry Walls with NSM CFRP Strips Subjected to Combined Loads

Buildings ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 103
Author(s):  
Houria Hernoune ◽  
Benchaa Benabed ◽  
Antonios Kanellopoulos ◽  
Alaa Hussein Al-Zuhairi ◽  
Abdelhamid Guettala
Keyword(s):  
Failure Modes ◽  
Numerical Study ◽  
Masonry Wall ◽  
Brick Masonry ◽  
Masonry Walls ◽  
Near Surface ◽  
Combined Loads ◽  
Reinforced Masonry ◽  
Brick And Mortar ◽  
Near Surface Mounted

Near surface mounted (NSM) carbon fibers reinforced polymer (CFRP) reinforcement is one of the techniques for reinforcing masonry structures and is considered to provide significant advantages. This paper is composed of two parts. The first part presents the experimental study of brick masonry walls reinforced with NSM CFRP strips under combined shear-compression loads. Masonry walls have been tested under vertical compression, with different bed joint orientations 90° and 45° relative to the loading direction. Different reinforcement orientations were used including vertical, horizontal, and a combination of both sides of the wall. The second part of this paper comprises a numerical analysis of unreinforced brick masonry (URM) walls using the detailed micro-modelling approach (DMM) by means of ABAQUS software. In this analysis, the non-linearity behavior of brick and mortar was simulated using the concrete damaged plasticity (CDP) constitutive laws. The results proved that the application of the NSM-CFRP strips on the masonry wall influences significantly strength, ductility, and post-peak behavior, as well as changing the failure modes. The adopted DMM model provides a good interface to predict the post peak behavior and failure mode of unreinforced brick masonry walls.

scholarly journals Key Factors for Online Branding Success in India: An ISM Approach

2020 ◽  
Vol 9 (1) ◽  
pp. 42-50
Author(s):  
Mandeep Kaur
Keyword(s):  
Success Factors ◽  
Future Research ◽  
Structural Modelling ◽  
Branding Strategy ◽  
Key Factors ◽  
Critical Success ◽  
Online Branding ◽  
Proposed Model ◽  
Brick And Mortar ◽  
Modelling Approach

In today’s digital age it is essential to analyse the factors that influence the success of online branding. Pure play e-tailer, Brick and mortar, click and mortar companies are required to follow online branding strategy. As online branding is the need of the hour companies are moving on the track where the ultimate destination is to adopt online branding as the strategy to stay ahead. Online branding is moving at the pace of the light. To keep up, companies need a robust foundation with the judgment to think precariously about the critical success factors for online branding. The purpose of the paper is to identify factors that influence the success of online branding, interrelationship among those factors and categories them in line with its driving and dependence power. These factors will help to prepare the model for companies who are planning to go for online branding strategy. Interpretative Structural Modelling approach is used to construct this model. The result found that both online factors and offline factors influence the success of online branding. Future research may endeavour to statistically validate the proposed model and may also expand the model by suggesting other factors that are influencing the success of online branding. Little research has investigated the interrelationship among factors which are affecting the success of online branding and thereby inducing companies to go for online branding. In addition the present paper contributed insights developed from the model that would help companies in taking decision related to online branding.

An equivalent stress method to account for local buckling in beam finite elements subjected to fire

2019 ◽  
Vol 10 (3) ◽  
pp. 340-353 ◽  
Author(s):  
Chrysanthos Maraveas ◽  
Thomas Gernay ◽  
Jean-Marc Franssen
Keyword(s):  
Finite Elements ◽  
Constitutive Model ◽  
Yield Stress ◽  
Equivalent Stress ◽  
Local Buckling ◽  
Bernoulli Beam ◽  
Content Type ◽  
Model Based ◽  
Proposed Model ◽  
Practical Implications

Purpose The purpose of this paper is to present an improved temperature-dependent constitutive model for steel that accounts for local instabilities of slender plates using an effective stress-based method. This model can be easily implemented for use with Bernoulli beam finite elements (FEs) in the fire situation. Design/methodology/approach The constitutive model is derived by calibration on parametric numerical analysis on isolated plates subject to buckling at different elevated temperatures. The model is implemented in the FE software SAFIR and validation is performed against experimental and shell element analysis results. Findings A constitutive model based on an equivalent stress method is proposed as an efficient way to consider local buckling in steel members exposed to fire. The proposed stress–strain–temperature relationship is asymmetric and is modified in compression only, by reducing the proportional limit, the yield stress and the strain at yield stress. The reduction of these parameters depends on the plate’s boundary conditions, slenderness and temperature. The validation of the proposed model shows good agreement over a range of profile dimensions, temperatures and steel grades. Research limitations/implications The model is still giving conservative results for large compressive load eccentricities. An enhanced model is under development to improve the predictive capability under large eccentricities. Practical implications The proposed model, easily implemented into any finite element software, allows using fibre type (Bernoulli) beam FEs for modelling structures made of slender sections. This has major practical implications as beam elements are the workhorse used for simulating the behaviour of structures in fire. This model, thus makes it possible to simulate large structures with slender steel sections at a limited computational cost. Originality/value The paper presents a novel steel constitutive model based on an innovative approach to capture local buckling at the material level using an equivalent stress approach. The theoretical development, validation and perspectives for future improvements are presented.

An innovative method to simulate stress-induced velocity changes in anisotropic rock

2021 ◽  
Vol 11 (4) ◽  
pp. 1-18
Author(s):  
Q. Bai ◽  
H. Konietzky
Keyword(s):  
Seismic Velocity ◽  
Numerical Models ◽  
Crack Density ◽  
Bedding Plane ◽  
Anisotropic Rock ◽  
Proposed Model ◽  
Isotropic Structure ◽  
Velocity Changes ◽  
Induced Velocity ◽  
Stress Dependent

This contribution proposes a numerical microstructural modeling approach to investigate stress-induced seismic velocity changes on anisotropic rocks. By introducing pre-existing cracks with preferential orientations in bonded-particle assemblies, the transverse isotropic structure of the Whitby Mudstone is simulated. Using power-law distributed aperture and calibrated micro-properties, we successfully reproduce stress-dependent velocity changes on Whitby Mudstones with different anisotropic angles in relation to the applied loads. The proposed model also duplicates the directional dependence of wave speed with respect to the bedding plane as expected theoretically. The numerical models show that velocity increase results from the closure of pre-existing cracks due to load increase. Direct relations are established between velocity changes and opened crack density (or crack closure), which displays a similar tendency compared with theoretical predictions. This relation can be used to quantify the micromechanisms behind the velocity changes. The proposed model provides the ability to directly examine the micro-processes underlying velocity changes.

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