scholarly journals Nonlinear modelling of the seismic response of masonry structures: Calibration strategies

2021 ◽  
Author(s):  
Antonio Maria D’Altri ◽  
Francesco Cannizzaro ◽  
Massimo Petracca ◽  
Diego Alejandro Talledo
Keyword(s):  
Mechanical Properties ◽  
Numerical Models ◽  
Shear Stiffness ◽  
Model Material ◽  
National Standards ◽  
National Standard ◽  
Masonry Structures ◽  
Nonlinear Modelling ◽  
Various Boundary Conditions ◽  
Panel Stiffness

AbstractIn this paper, a simple and practitioners-friendly calibration strategy to consistently link target panel-scale mechanical properties (that can be found in national standards) to model material-scale mechanical properties is presented. Simple masonry panel geometries, with various boundary conditions, are utilized to test numerical models and calibrate their mechanical properties. The calibration is successfully conducted through five different numerical models (most of them available in commercial software packages) suitable for nonlinear modelling of masonry structures, using nonlinear static analyses. Firstly, the panel stiffness calibration is performed, focusing the attention to the shear stiffness. Secondly, the panel strength calibration is conducted for several axial load ratios by attempts using as reference the target panel strength deduced by well-known analytical strength criteria. The results in terms of panel strength for the five different models show that this calibration strategy appears effective in obtaining model properties coherent with Italian National Standard and Eurocode. Open issues remain for the calibration of the post-peak response of masonry panels, which still appears highly conventional in the standards.

scholarly journals Analysis and Harmonization of National and International Quality Standards for Compacted Graphite Cast Irons

2020 ◽  
pp. 88-95
Author(s):  
Alena Kropivna ◽  
◽  
Olexandr Kuzyk ◽  
Keyword(s):  
Mechanical Properties ◽  
Cast Iron ◽  
Chemical Composition ◽  
Quality Indicators ◽  
International Standards ◽  
National Standards ◽  
National Standard ◽  
High Quality ◽  
Foundry Industry ◽  
European Standards

Ensuring and coordination of high quality indicators of materials in the foundry industry is necessary in the development of Ukraine's economy. High quality products need to be enshrined in new national standards, harmonized with international and European standards. Thus, the purpose of this work is to analyze national and international standards for quality indicators of vermicular graphite iron and their harmonization with each other. The foundry industry of Ukraine has developed mainly with the use of interstate standards - GOST, which differ significantly from European and international and requires coordination and other approaches to the development of new standards. Today there are a number of international standards: ISO, SAE, CEN, VDG, ASTM, JIS, GB, STAS, which regulate the properties of cast iron with vermicular graphite. Most standards define the range of permissible content of spherical graphite (0… 20%) in the structure of cast iron with vermicular graphite, as well as determine the shape of samples to determine the properties and provide for the determination of graphite on surfaces formed after machining castings. In accordance with the needs of the automotive industry, the Society of Automotive Engineers (SAE) has created the standard SAEJ1887 JUL2002 for cast iron with vermicular graphite. The DSTU standard in force in Ukraine regulates only the temporary resistance to tensile and elongation laid down in the brand designation. Thus, the improvement, provision and harmonization of the national standard at the vermicular graphite iron by achieving high quality indicators of materials in the foundry industry, will ensure the stability of the technological production process, and further entry into international and European markets and a qualitatively new level of domestic engineering. An analysis of the current standards in Ukraine DSTU for cast iron with vermicular graphite is given, as well as its regulated mechanical properties and recommended chemical composition. The properties of similar international and European standards for cast iron with vermicular graphite according to ISO, SAE, CEN, VDG, ASTM, JIS, GB, STAS standardization are analyzed, as well as cross-references to ISO 16112 to other standard brands of the vermicular graphite iron. The conformity of brands of materials, depending on their chemical composition and mechanical properties given in GOST, international and European indicators is found out.

Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part IV: Laboratory Measurement of Mechanical Properties and Mechanical Actions of Tires Relating to Treadwear

1986 ◽  
Vol 14 (4) ◽  
pp. 264-291
Author(s):  
K. L. Oblizajek ◽  
A. G. Veith
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Contact Zone ◽  
Flexural Rigidity ◽  
Comprehensive Evaluation ◽  
Shear Stiffness ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Band Bending ◽  
Tread Rubber

Abstract Treadwear is explained by specific mechanical properties and actions of tires. Rubber shear stresses in the contact zone between the tire and the road become large at large slip angles. When normal stresses are insufficient to prevent sliding at the rear of the footprint, wear occurs at a rate that depends on test severity. Two experimental approaches are described to relate treadwear to tire characteristics. The first uses transducers imbedded in a simulated road surface to obtain direct measurements of contact stresses on the loaded, freely-rolling, steered tires. The second approach is developed with the aid of a simple carcass, tread-band, tread-rubber tire model. Various tire structural configurations; characterized by carcass spring rate, edgewise flexural band stiffness, and tread rubber shear stiffness; are simulated and lateral shear stress response in the contact zone is determined. Tires featuring high band stiffness and low carcass stiffness generate lower lateral shear stress levels. Furthermore, coupling of tread-rubber stiffness and band flexural rigidity are important in determining level of shear stresses. Laboratory measurements with the described apparatus produced values of tread-band bending and carcass lateral stiffness for several tire constructions. Good correlation is shown between treadwear and a broad range of tire stiffness and test course severities.

scholarly journals Study of biaxial mechanical properties of the passive pig heart: material characterisation and categorisation of regional differences

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Fulufhelo Nemavhola
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Computational Models ◽  
Heart Diseases ◽  
Interventricular Septum ◽  
Model Material ◽  
Biaxial Test ◽  
Material Behaviour ◽  
Material Parameters ◽  
Biaxial Tests

AbstractRegional mechanics of the heart is vital in the development of accurate computational models for the pursuit of relevant therapies. Challenges related to heart dysfunctioning are the most important sources of mortality in the world. For example, myocardial infarction (MI) is the foremost killer in sub-Saharan African countries. Mechanical characterisation plays an important role in achieving accurate material behaviour. Material behaviour and constitutive modelling are essential for accurate development of computational models. The biaxial test data was utilised to generated Fung constitutive model material parameters of specific region of the pig myocardium. Also, Choi-Vito constitutive model material parameters were also determined in various myocardia regions. In most cases previously, the mechanical properties of the heart myocardium were assumed to be homogeneous. Most of the computational models developed have assumed that the all three heart regions exhibit similar mechanical properties. Hence, the main objective of this paper is to determine the mechanical material properties of healthy porcine myocardium in three regions, namely left ventricle (LV), mid-wall/interventricular septum (MDW) and right ventricle (RV). The biomechanical properties of the pig heart RV, LV and MDW were characterised using biaxial testing. The biaxial tests show the pig heart myocardium behaves non-linearly, heterogeneously and anisotropically. In this study, it was shown that RV, LV and MDW may exhibit slightly different mechanical properties. Material parameters of two selected constitutive models here may be helpful in regional tissue mechanics, especially for the understanding of various heart diseases and development of new therapies.

scholarly journals Evolution of Meniscal Biomechanical Properties with Growth: An Experimental and Numerical Study

2021 ◽  
Vol 8 (5) ◽  
pp. 70
Author(s):  
Marco Ferroni ◽  
Beatrice Belgio ◽  
Giuseppe M. Peretti ◽  
Alessia Di Giancamillo ◽  
Federica Boschetti
Keyword(s):  
Mechanical Properties ◽  
Stress Relaxation ◽  
Developmental Stage ◽  
Mechanical Response ◽  
Numerical Study ◽  
Numerical Models ◽  
Mechanical Stimulus ◽  
Specific Response ◽  
Mechanical Parameters ◽  
Biochemical Analyses

The menisci of the knee are complex fibro-cartilaginous tissues that play important roles in load bearing, shock absorption, joint lubrication, and stabilization. The objective of this study was to evaluate the interaction between the different meniscal tissue components (i.e., the solid matrix constituents and the fluid phase) and the mechanical response according to the developmental stage of the tissue. Menisci derived from partially and fully developed pigs were analyzed. We carried out biochemical analyses to quantify glycosaminoglycan (GAG) and DNA content according to the developmental stage. These values were related to tissue mechanical properties that were measured in vitro by performing compression and tension tests on meniscal specimens. Both compression and tension protocols consisted of multi-ramp stress–relaxation tests comprised of increasing strains followed by stress–relaxation to equilibrium. To better understand the mechanical response to different directions of mechanical stimulus and to relate it to the tissue structural composition and development, we performed numerical simulations that implemented different constitutive models (poro-elasticity, viscoelasticity, transversal isotropy, or combinations of the above) using the commercial software COMSOL Multiphysics. The numerical models also allowed us to determine several mechanical parameters that cannot be directly measured by experimental tests. The results of our investigation showed that the meniscus is a non-linear, anisotropic, non-homogeneous material: mechanical parameters increase with strain, depend on the direction of load, and vary among regions (anterior, central, and posterior). Preliminary numerical results showed the predominant role of the different tissue components depending on the mechanical stimulus. The outcomes of biochemical analyses related to mechanical properties confirmed the findings of the numerical models, suggesting a specific response of meniscal cells to the regional mechanical stimuli in the knee joint. During maturation, the increase in compressive moduli could be explained by cell differentiation from fibroblasts to metabolically active chondrocytes, as indicated by the found increase in GAG/DNA ratio. The changes of tensile mechanical response during development could be related to collagen II accumulation during growth. This study provides new information on the changes of tissue structural components during maturation and the relationship between tissue composition and mechanical response.

scholarly journals Applicability of a Three-Layer Model for the Dynamic Analysis of Ballasted Railway Tracks

Vibration ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 151-174
Author(s):  
André F. S. Rodrigues ◽  
Zuzana Dimitrovová
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Dynamic Analysis ◽  
Shear Stiffness ◽  
Shear Resistance ◽  
Railway Track ◽  
Fe Model ◽  
Inertial Effects ◽  
Layer Model ◽  
3D Finite Element

In this paper, the three-layer model of ballasted railway track with discrete supports is analyzed to access its applicability. The model is referred as the discrete support model and abbreviated by DSM. For calibration, a 3D finite element (FE) model is created and validated by experiments. Formulas available in the literature are analyzed and new formulas for identifying parameters of the DSM are derived and validated over the range of typical track properties. These formulas are determined by fitting the results of the DSM to the 3D FE model using metaheuristic optimization. In addition, the range of applicability of the DSM is established. The new formulas are presented as a simple computational engineering tool, allowing one to calculate all the data needed for the DSM by adopting the geometrical and basic mechanical properties of the track. It is demonstrated that the currently available formulas have to be adapted to include inertial effects of the dynamically activated part of the foundation and that the contribution of the shear stiffness, being determined by ballast and foundation properties, is essential. Based on this conclusion, all similar models that neglect the shear resistance of the model and inertial properties of the foundation are unable to reproduce the deflection shape of the rail in a general way.

American National Standard for Human Factors Engineering of Visual Display Terminal Workstations: A Report to the Society

1985 ◽  
Vol 29 (10) ◽  
pp. 987-987 ◽  
Author(s):  
Gene Lynch
Keyword(s):  
Human Factors ◽  
Text Processing ◽  
Data Entry ◽  
Visual Display ◽  
Measurement Methods ◽  
National Standards ◽  
National Standard ◽  
Human Factors Engineering ◽  
Visual Display Terminal ◽  
The Individual

The American National Standard for Human Factors Engineering of Visual Display Terminal Workstations, the first standard sponsored by the Human Factors Society, is in the final stages of acceptance as an American National Standard. This standard addresses the physical and perceptual aspects of the visual display terminal workstation as used in text processing, data entry, and data inquiry. Standards take on many different forms and fill a variety of needs. Basically a standard provides a reference. Some standards are written so that two systems may be designed to complement each other or fit together. Lightbulbs and fixtures designed to the same standard will work together. In the case of human factors standards one half of the system is already designed, the human. The variety of the design of this part of the system requires that human factors standards identify the parameters to be considered and the corresponding measurement methods needed to insure that the equipment is designed to fit the individual human. A good solution needs to be based on the particular set of circumstances at hand. The voluntary standards method, known as the American National Standards, provides a vehicle for specifying the appropriate parameters and measurement methods while incorporating the necessary flexibility required to insure good designs for individuals. The purpose of this panel session is to provide the society with an interactive session with representatives of the standards drafting committee. A brief history of the committee and its activities will be presented. The panelists will then describe the approach taken in each of the major sections, the mandatory requirements, and the elements the panelists consider to be of particular interest

Experimental Study of Adhesion between FRCM and Masonry Support

2014 ◽  
Vol 624 ◽  
pp. 189-196 ◽  
Author(s):  
Valeria Corinaldesi ◽  
Jacopo Donnini ◽  
Giorgia Mazzoni
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Bond Strength ◽  
Cement Matrix ◽  
Masonry Structures ◽  
Matrix Interface ◽  
Mechanical Interaction ◽  
Inorganic Particles ◽  
Ceramic Support

The use of composites with cement matrix seems to acquire an increasing interest in applications to masonry structures, due to their low impact, and a deeper understanding of the mechanical interaction between support and reinforcement is certainly necessary. The effectiveness of these interventions strongly depends on the bond between strengthening material and masonry, on the fibers/matrix interface, as well as on the mechanical properties of the masonry substrate [1]. In this work the attention was focused on the possible improvement of the bond between FRCM and masonry by means of an inorganic primer, which can be spread on the ceramic support before the application of FRCM reinforcement. Two different kinds of brick were tested, in order to simulate more or less porous masonry supports. Results obtained showed that, independently on the kind of brick used (more or less porous) the presence of an inorganic primer always improves bond between masonry support and the cementitiuos matrix of FRCM. In fact, the cementitous matrix of FRCM has been studied and optimized in order to guarantee the best fibers/matrix interface, while it is not necessarily the best option for improving the adhesion with the masonry support. In particular, very effective seems to be the use of very fine inorganic particles (at nanometric scale), which proved to be able to assure the best results in terms of bond strength. Also the fresh consistence of the primer seemed to influence the final result.

Discussion on Determination of Non-Methane Hydrocarbons

2014 ◽  
Vol 1073-1076 ◽  
pp. 562-566
Author(s):  
Zhe Min Li
Keyword(s):  
International Standards ◽  
National Standards ◽  
National Standard ◽  
Measure Methods

This paper summarized the measure methods which include both Chinese national standards and international standards of how to determine the concentration of Non-methane Hydrocarbons (NMHC).Some problems and suggestions were discussed in this paper to improve the level of the measure methods and prompt the establishment of relative Chinese national standard.

scholarly journals Numerical and experimental evaluation of masonry prisms by finite element method

2017 ◽  
Vol 10 (2) ◽  
pp. 477-508 ◽  
Author(s):  
C. F.R. SANTOS ◽  
R. C. S. S. ALVARENGA ◽  
J. C. L. RIBEIRO ◽  
L. O CASTRO ◽  
R. M. SILVA ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
High Strength Concrete ◽  
Numerical Models ◽  
High Strength ◽  
Experimental Tests ◽  
Experimental Results ◽  
Concrete Blocks ◽  
Micro Modeling ◽  
Modeling Strategy

Abstract This work developed experimental tests and numerical models able to represent the mechanical behavior of prisms made of ordinary and high strength concrete blocks. Experimental tests of prisms were performed and a detailed micro-modeling strategy was adopted for numerical analysis. In this modeling technique, each material (block and mortar) was represented by its own mechanical properties. The validation of numerical models was based on experimental results. It was found that the obtained numerical values of compressive strength and modulus of elasticity differ by 5% from the experimentally observed values. Moreover, mechanisms responsible for the rupture of the prisms were evaluated and compared to the behaviors observed in the tests and those described in the literature. Through experimental results it is possible to conclude that the numerical models have been able to represent both the mechanical properties and the mechanisms responsible for failure.

scholarly journals ADSORPTION OF NANOWOLLASTONITE ON CELLULOSE SURFACE: EFFECTS ON PHYSICAL AND MECHANICAL PROPERTIES OF MEDIUM-DENSITY FIBERBOARD (MDF)

CERNE ◽  
2016 ◽  
Vol 22 (2) ◽  
pp. 215-222 ◽  
Author(s):  
Hamid Reza Taghiyari ◽  
Roya Majidi ◽  
Asghar Jahangiri
Keyword(s):  
Mechanical Properties ◽  
Density Functional ◽  
Medium Density Fiberboard ◽  
Physical And Mechanical Properties ◽  
Mechanical Tests ◽  
National Standard ◽  
Medium Density ◽  
Wood Fibers ◽  
Strong Adsorption ◽  
Cellulose Surface

ABSTRACT Effects of nanowollastonite (NW) adsorption on cellulose surface were studied on physical and mechanical properties of medium-density fiberboard (MDF) panels; properties were then compared with those of MDF panels without NW-content. The size range of NW was 30-110 nm. The interaction between NW and cellulose was investigated using density functional theory (DFT). Physical and mechanical tests were carried out in accordance with the Iranian National Standard ISIRI 9044 PB Type P2 (compatible with ASTM D1037-99) specifications. Results of DFT simulations showed strong adsorption of NW on cellulose surface. Moreover, mechanical properties demonstrated significant improvement. The improvement was attributed to the strong adsorption of NW on cellulose surface predicted by DFT, adding to the strength and integrity between wood fibers in NW-MDF panels. It was concluded that NW would improve mechanical properties in MDF panels as a wood-composite material, as well as being effective in improving its biological and thermal conductivity.

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