scholarly journals Macroscopic response of regular masonry from homogenization: comparison of isotropic and orthotropic damage models

2020 ◽  
Vol 310 ◽  
pp. 00052
Author(s):  
Tomáš Krejčí ◽  
Tomáš Koudelka ◽  
Vasco Bernardo ◽  
Michal Šejnoha
Keyword(s):  
Reinforced Concrete ◽  
Constitutive Model ◽  
Effective Properties ◽  
Damage Model ◽  
Masonry Structure ◽  
The Other ◽  
Homogenization Problem ◽  
Material Parameters ◽  
Damage Models ◽  
The One

This paper outlines prediction of macroscopic effective properties of a regular masonry from homogenization. It focuses on the derivation of nonlinear macroscopic stress strain curves adopting either classical isotropic or more advanced orthotropic damage model. The response resulting from both tensile and compressive uniaxial loading is examined in the light of strain and stress loading regimes. A masonry structure typical of ”Placa” buildings (mixed masonry- reinforced concrete buildings) built in Portugal is selected as one particular example to illustrate the differences in the predictive capabilities of the two constitute models on the one hand and the formulation of the homogenization problem on the other hand. It is suggested that the mixed loading conditions are essentially required when estimating all macroscopic material parameters needed in the corresponding macroscopic constitutive model

scholarly journals Extension of Flow Behaviour and Damage Models for Cast Iron Alloys with Strain Rate Effect

2020 ◽  
Author(s):  
Chuang Liu ◽  
Dongzhi Sun ◽  
Xianfeng Zhang ◽  
Florence Andrieux ◽  
Tobias Gerster
Keyword(s):  
Cast Iron ◽  
Constitutive Model ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Damage Model ◽  
Iron Alloys ◽  
Strain Rate Range ◽  
Strain Rates ◽  
Damage Models ◽  
Rate Dependent

Abstract Cast iron alloys with low production cost and quite good mechanical properties are widely used in the automotive industry. To study the mechanical behavior of a typical ductile cast iron (GJS-450) with nodular graphite, uni-axial quasi-static and dynamic tensile tests at strain rates of 10− 4, 1, 10, 100, and 250 s− 1 were carried out. In order to investigate the effects of stress state, specimens with various geometries were used in the experiments. Stress–strain curves and fracture strains of the GJS-450 alloy in the strain-rate range of 10− 4 to 250 s− 1 were obtained. A strain rate-dependent plastic flow law based on the Voce model is proposed to describe the mechanical behavior in the corresponding strain-rate range. The deformation behavior at various strain rates is observed and analyzed through simulations with the proposed strain rate-dependent constitutive model. The available damage model from Bai and Wierzbicki is extended to take the strain rate into account and calibrated based on the analysis of local fracture strains. The validity of the proposed constitutive model including the damage model was verified by the corresponding experimental results. The results show that the strain rate has obviously nonlinear effects on the yield stress and fracture strain of GJS-450 alloys. The predictions with the proposed constitutive model and damage models at various strain rates agree well with the experimental results, which illustrates that the rate-dependent flow rule and damage models can be used to describe the mechanical behavior of cast iron alloys at elevated strain rates.

Consistent Hashin-Shtrikman Bounds on the Effective Properties of Periodic Composite Materials

1999 ◽  
Vol 66 (4) ◽  
pp. 858-866
Author(s):  
P. Bisegna ◽  
R. Luciano
Keyword(s):  
Composite Materials ◽  
Saddle Point ◽  
Variational Principles ◽  
Effective Properties ◽  
The Other ◽  
Constitutive Behavior ◽  
Homogenization Problem ◽  
Numerical Examples ◽  
Periodic Composites ◽  
Periodic Composite

In this paper the four classical Hashin-Shtrikman variational principles, applied to the homogenization problem for periodic composites with a nonlinear hyperelastic constitutive behavior, are analyzed. It is proved that two of them are indeed minimum principles while the other two are saddle point principles. As a consequence, every approximation of the former ones provide bounds on the effective properties of composite bodies, while approximations of the latter ones may supply inconsistent bounds, as it is shown by two numerical examples. Nevertheless, the approximations of the saddle point principles are expected to provide better estimates than the approximations of the minimum principles.

scholarly journals Uniaxial Compressive Test of High Ductile Fiber-Reinforced Concrete and Damage Constitutive Model

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Mingke Deng ◽  
Jiaojiao Pan ◽  
Xingwen Liang
Keyword(s):  
Reinforced Concrete ◽  
Constitutive Model ◽  
Damage Model ◽  
Engineering Application ◽  
Strain Curve ◽  
Damage Threshold ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Uniaxial Compressive Test ◽  
Damage Constitutive Model

It has been widely recognized that the constitutive model plays an essential role in engineering application of high ductile fiber-reinforced concrete (HDC). In this research, uniaxial compressive tests were conducted on nine groups of HDC specimens with different mixture ratios and one group of mortar matrix specimens as comparison, discussing the effect of fiber content, water-cement ratio, fly ash content, and sand-binder ratio. According to the characteristics of stress-strain curve of HDC under uniaxial compression, a damage constitutive model was proposed by introducing two damage threshold parameters and then was compared with other existing models. Results indicated that the damage model curves suggested in this paper were best consistent with experimental curves and substantially demonstrate the damage evolution process as well as the cracking resistance effect of fiber bridging stress.

scholarly journals Simplified damage models applied in the numerical analysis of reinforced concrete structures

2012 ◽  
Vol 5 (1) ◽  
pp. 26-37 ◽  
Author(s):  
J. J. C. Pituba ◽  
M. M. S. Lacerda
Keyword(s):  
Reinforced Concrete ◽  
Structural Engineering ◽  
Damage Model ◽  
Concrete Structures ◽  
Numerical Analyses ◽  
Anisotropic Damage ◽  
Reinforced Concrete Structures ◽  
Damage Models ◽  
Tension And Compression ◽  
Elastic Responses

This work presents one and two-dimensional numerical analyses using isotropic and anisotropic damage models for the concrete in order to discuss the advantages of these modeling. Initially, it is shortly described the damage model proposed by Mazars. This constitutive model assumes the concrete as isotropic and elastic material, where locally the damage is due to extensions. On the other hand, the damage model proposed by Pituba, the material is assumed as initial elastic isotropic medium presenting anisotropy, plastic strains and bimodular response (distinct elastic responses whether tension or compression stress states prevail) induced by the damage. To take into account for bimodularity two damage tensors governing the rigidity in tension and compression regimes, respectively, are introduced. Damage activation is expressed by two criteria indicating the initial and further evolution of damage. Soon after, the models are used in numerical analyses of the mechanical behavior of reinforced concrete structures. Accordingly with comparison of the obtained responses, considerations about the application of the isotropic and anisotropic damage models are presented for 1D and 2D reinforced concrete structures modeling as well as the potentialities of the simplified versions of damage models applied in situations of structural engineering.

scholarly journals Damage Model of Reinforced Concrete Members under Cyclic Loading

2018 ◽  
Vol 38 ◽  
pp. 03057
Author(s):  
Bo Chen Wei ◽  
Jing Shu Zhang ◽  
Yin Hua Zhang ◽  
Jia Lai Zhou
Keyword(s):  
Growth Rate ◽  
Reinforced Concrete ◽  
Cyclic Loading ◽  
Small Amplitude ◽  
Damage Model ◽  
Damage Index ◽  
Displacement Amplitude ◽  
Damage Models ◽  
Concrete Members ◽  
Increasing Function

Based on the Kumar damage model, a new damage model for reinforced concrete members is established in this paper. According to the damage characteristics of reinforced concrete members subjected to cyclic loading, four judgment conditions for determining the rationality of damage models are put forward. An ideal damage index (D) is supposed to vary within a scale of zero (no damage) to one (collapse). D should be a monotone increasing function which tends to increase in the case of the same displacement amplitude. As for members under large displacement amplitude loading, the growth rate of D should be greater than that of D under small amplitude displacement loading. Subsequently, the Park-Ang damage model, the Niu-Ren damage model, the Lu-Wang damage model and the proposed damage model are analyzed for 30 experimental reinforced concrete members, including slabs, walls, beams and columns. The results show that current damage models do not fully matches the reasonable judgment conditions, but the proposed damage model does. Therefore, a conclusion can be drawn that the proposed damage model can be used for evaluating and predicting damage performance of RC members under cyclic loading.

A novel non-linear cumulative fatigue damage model based on the degradation of material memory

2019 ◽  
Vol 29 (4) ◽  
pp. 610-625
Author(s):  
Jie Zhou ◽  
Hong-Zhong Huang ◽  
Miles V Barnhart ◽  
Guoliang Huang ◽  
Yan-Feng Li
Keyword(s):  
Experimental Data ◽  
Fatigue Damage ◽  
Residual Life ◽  
Damage Model ◽  
Loading History ◽  
Material Parameters ◽  
Life Estimation ◽  
Damage Models ◽  
Proposed Model ◽  
Cumulative Fatigue Damage

Many fatigue damage models have been investigated based on the S– N curve or modified S– N curve; however, a number of them require additional efforts to determine the material parameters or do not consider the loading history (loading interactions, loading sequences, loading levels, etc.). These limitations can result in extreme deviations for estimating the fatigue life in real-world scenarios. To address these limitations, a new fatigue damage model is developed based on the material memory, which can be described as the degradation of mechanical properties under cyclic loadings. Comparisons with three models are used to demonstrate the validity of the proposed model. Furthermore, four sets of experimental data under two-stress and four-stress levels are carried out to verify the validation of the proposed model, which improves the residual life estimation over the three existing models used for comparison.

A conceptual model for the estimation of flood damage to power grids

2021 ◽  
Author(s):  
Panagiotis Asaridis ◽  
Daniela Molinari ◽  
Francesco Ballio
Keyword(s):  
Conceptual Model ◽  
Damage Assessment ◽  
Flood Damage ◽  
Power Grids ◽  
The Other ◽  
Economic Losses ◽  
Damage Mechanisms ◽  
Damage Models ◽  
Other Hand ◽  
The One

<p>Flood damage assessment is a crucial component of any decision-making process on flood risk management and mitigation; for this reason, reliable tools for flood damage estimation are required, for all the categories of exposed elements. Despite networks can suffer high losses in case of flood, and in comparison with other exposed items, flood damage modelling to infrastructures is still a challenging task. This is due, on the one hand, to the complexity of networks as well as of their interconnections; on the other hand, to the lack of knowledge and data to investigate damage mechanisms and to calibrate and validate damage models. Grounding on the investigation of the state of art, this contribution presents a conceptualization of flood damage to power grids. The ultimate objective of the conceptual model is to be an operative tool in support of more comprehensive and reliable flood damage assessments to power grids, highlighting: (i) the different components of the damage (i.e. direct, indirect, and systemic, meaning damage due to the interdependencies among power grids and residential, commercial, industrial and other infrastructure sectors), (ii) their interconnections, (iii) the hazard, exposure and vulnerability variables on which they depend, (iv) the temporal and spatial scales for their assessment. The development of the model highlighted, on the one hand, the importance of dividing damage assessment in two steps: the estimation of damage in quantitative/physical units and the estimation of the consequent economic losses. On the other hand, the variety of damage mechanisms and cascading effects shaping the final damage figure arises, asking for an interdisciplinary and multi-scale evaluation approach. The development of the conceptual model is the first step of a PhD research on the development of flood damage models for infrastructures. Next steps will validate the model in real case studies and evaluate how the different damage components could be investigated in the Italian context.</p>

Constitutive Model Based on Damage Mechanics of Fiber Reinforced Concrete (FRC): A Review

2012 ◽  
Vol 238 ◽  
pp. 37-40
Author(s):  
Duo Xin Zhang ◽  
Qing Yun Wang
Keyword(s):  
Reinforced Concrete ◽  
Constitutive Model ◽  
Constitutive Modeling ◽  
Damage Mechanics ◽  
Damage Model ◽  
Constitutive Models ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Model Based ◽  
Historical Developments

In order to study the constitutive model of fiber reinforced concrete (FRC) for future, this paper emphasizes on three aspects. FRCs constitutive model based on damage mechanics has been reviewed. The knowledge and development of constitutive models is discussed based on its historical developments and logical relations. Damage model of FRCs which has been developed in recent years is summarized at macro and micro levels. The development trends of constitutive modeling for FRCs are suggested on the basis of our understanding of essential physical properties of FRC, e.g. its nonlinearity

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

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