Academic literature on the topic 'Wall macro-deformations'

The dynamic behavior of the lung in health and disease depends on its viscoelastic properties. To better understand these properties, several mathematical models have been utilized by many investigators. In the present work, we present a new approach that characterizes the dynamics of gas flow into a viscoelastic porous medium that models the lung structure. This problem is considered in terms of the lung input impedance on a macro level and parenchymal tissue impedance on the level of an alveolar wall. We start from a basic theoretical analysis in which macroscopic tissue deformations are represented in accordance with the linearized Navier-Stokes equations. This approach has strong theoretical underpinnings in other situations but has not been applied to analyze the impedance of the inflated lung. Our analysis provides a theoretical basis for analyzing the interaction between flow into the lungs as a biophysical diffusion process and parenchymal viscoelasticity described phenomenologically, within the frameworks of standard viscoelasticity and structural damping. This lung impedance incorporates parameters of porosity, permeability, and viscoelasticity on micro and macro levels of parenchymal tissue. The analysis shows the theoretical basis of the transformation from the impedance of alveolar walls or isolated tissue strips to that of the intact parenchyma. We also show how the loading impedance at the lung boundary may have a significant impact on the dynamic behavior of whole lung viscoelasticity. Our analysis may be useful in directing specific tests of different models and for analyzing experimental measurements of viscoelastic parameters of lung material under normal and pathological conditions.

A full scale slice of a 7 story reinforced concrete building was tested on the shake table at the UCSD Engelkirk Structural Research Centre in 2006. As part of the research project, a blind prediction contest was sponsored to assess the capability of currently available analysis procedures to predict the seismic response of cantilever reinforced concrete shear wall structures. This paper describes an entry based on a nonlinear finite element model, using macro elements to represent both the shear and the flexural modes of behaviour. A comparison of the predicted response with the test results showed that the analysis procedure produced reasonable predictions of deformations for the lowest and highest of the four earthquakes but under-estimated response for the two moderate earthquakes by approximately 30%. For all earthquakes, the analysis base moment was much lower than the test value. Modifications to the procedure to improve the correlation were identified and implemented but did not remedy the deficit in base moments. Detailed results of the test program revealed that the causes for this discrepancy were the contribution to overturning results of gravity columns and the flange wall, neither of which had been included in the model. When these were incorporated the average error between test and analysis results was less than 10% for all earthquakes, well within acceptable limits for a design office type of model. The correlation of tests and analysis also provided useful information on design aspects for shear walls, such as the influence of secondary components and dynamic magnification factors.

The practise of single-point incremental forming (SPIF) is an advanced flexible manufacturing process initiated during the early 2000s, and since then, extensive research has been conducted in this area. Sheets can be formed incrementally, which not only reduces the amount of energy needed and raw materials, but also allows for multiple products types to be made using the same set of resources. Investigations existed have helped provide a thorough understanding of the macro SPIF deformation mechanism. In the present paper the following aspects have been highlighted: the execution accuracy of the incrementally formed part; determining the part surface roughness; ANOVA analysis of the factors influence on precision and surface roughness. The observed deformations in the shape of the part, can be attributed to the kinematics of the forming process. These deviations are evident in the curvature radius of the part side wall, the presence of a radius of connection between the wall and the bottom of the part, and the dimensional variations indicated by the forming depth. With regards to the surface smoothness, it was noticed that the TiN coated tool yielded the most favourable roughness outcomes. Key words: SPIF, Al 3003 sheet, ANOVA analysis, influence of tehnological parameters, TiN-coated tool.

Shear walls are very efficient structural elements to resist lateral seismic disturbance. Despite the aforementioned seismic performance, recent investigations report that they have suffered from significant structural damage after recent seismic activity, even for those complying with seismic provisions. These deficiencies in resistance and deformation capacities need to be explored. This study considers the influence of plastic length Lp, concrete compressive strength f_c28, longitudinal reinforcement ratio ρl, transverse reinforcement ratio ρsh, reduced axial load ν, confinement zone depth CS and focusing on the geometric slenderness λ. The parametric study has been conducted through NL pushover analysis using Peform3D software. The chosen coupled shear-flexure fiber macro model was calibrated with well-known cyclic experimental specimens. The paper points out the discrepancy between the two well-known codes EC8 and ASCE/SEI 41-13. In fact, the value of the slenderness ratio (λ) that trigger the beginning of a purely flexural behaviour recommended by EC8 (λ>2) is very different from the value of the ASCE/SEI 41-13 (λ>3) without accounting for the effect of the reduced axial force. Finally, it was found that RCW capacities are very sensitive to f_c28, ν, ρl, Lp and less sensitive to ρsh and CS. However, (λ) is the most decisive factor affecting the NL wall response. A new limit of slenderness and appropriate deformations of rotations are recommended to provide an immediate help to designers and an assistance to those involved with drafting codes. Doi: 10.28991/cej-2021-03091777 Full Text: PDF

Abstract Masonry churches, which are one of the cultural heritages, show the historical background, cultural and religious characteristics of the cities and material properties. Churches in the earthquake zone, which are different from each other in terms of typology and have a special importance, are at risk. The aim of this study is to examine the earthquake behavior of a church sample in Turkey and to provide a guide for structures with similar typology. The building was modeled and subjected to dynamic loads using macro modeling technique. Free vibration mode shapes were determined by modal analysis, and it was determined that these modes were mainly in the form of translation of the upper part of the structure. In the time history analysis, the stress and deformation values were determined. It has been observed that the stresses take high values at the supports and top of the main columns and in the arches connecting these columns to the side walls. It was concluded that the deformations reached their maximum values at the apex of the triangular gable walls in the upper part of the building. The results obtained are consistent with the damage the church received in past earthquakes.

The Artificial Ground Freezing (AGF) method, which is widely used in tunnel excavations, significantly affects the properties of geotechnical materials in frozen walls under extremely low temperatures. In order to simulate the AGF process, the freezing treatment with a temperature of −30°C and thawing treatment temperature of 25°C were performed on natural specimens of granite residual soil (GRS). Subsequently, triaxial (TRX) tests were conducted to evaluate mechanical properties and Nuclear Magnetic Resonance Image (NMRI) tests were applied to detect pore distributions of GRS. To clarify variations of microstructure after freezing-thawing, the relaxation time (T2) distribution curves and T2-weighted images from NMRI results were thoroughly analyzed from the perspective of quantization and visualization. Results show that the shear strength as well as the cohesion of GRS are reduced sharply by the AGF process, while the internal friction angle decreases gently. The pore size distribution (PSD) converted from the T2 curve is constituted of two different peaks, corresponding to micro-pores with diameters from 0.1 to 10 µm and macro-pores with diameters from 10 to 1,000 µm. Under the AGF impact, the expansion in macro-pores and shrinkage in micro-pores simultaneously exist in the specimen, which was verified from a visualized perspective by T2-weighted images. The frost heaving damage on shear strength is attributed to the microstructural disturbance caused by the presence of large-scale pores and uneven deformations in GRS, which is subjected to the AGF impact under an extremely low temperature.

It is believed that the Yılanlı or Leylekli Bridge (bridge with stork or snake figures) in Tokat, a city with high seismicity, was built during the Roman or Byzantine period. Although no structural damage was found on the bridge, which is still open to pedestrian traffic, it is very important to determine the seismic behaviour of the bridge considering the possible earthquakes the structure will be exposed to. This paper presents the seismic response of the historical Yılanlı (Leylekli) Bridge, which has been subjected to unfavourable man-made changes in geometric shape over time. The original and modified shapes of the bridge were modelled using the macro modelling approach in ANSYS finite element software. The structural performance of the models was evaluated in terms of stresses, deformations, and especially cracks on the arch and spandrel walls using nonlinear static and time history analyses. The results of the analysis show that the change in shape, which is not desirable from an architectural and aesthetic point of view, adversely affects the seismic performance of the historical bridge and makes it more vulnerable to possible earthquakes. In addition, the analyses clearly showed that both models are subject to serious structural damage that could lead to a collapse in the event of a potential large magnitude earthquake.

L’efficacité énergétique des composants et systèmes thermiques, l’amélioration et le développement de nouvelles technologies sont des enjeux majeurs aujourd’hui. Dans ce contexte général, les travaux de cette thèse s’inscrivent dans une perspective d’amélioration des performances thermiques et de mélange d’échangeurs-réacteurs multifonctionnels qui, plus que jamais, sont des composants clés. Pour atteindre cet objectif, une technique d'intensification passive a été explorée. Elle implique l'application de deux types de macro-déformations pariétales sur les parois d'un tube annulaire en écoulement laminaire. L’étude s’est tout d'abord concentrée sur la caractérisation des écoulements secondaires créés par chacune des déformations appliquées séparément sur l’intensification des transferts. Ensuite, une combinaison de déformations radiales successives et alternées sur la paroi externe, associées à une géométrie engendrant un mouvement de swirl sur la paroi interne a permis d'augmenter significativement le mélange, grâce à l'apparition d'advection chaotique dans l'écoulement. La compréhension des mécanismes physiques mis en jeux s’est appuyée sur une analyse numérique des champs locaux thermiques et hydrauliques, sur l’identification des structures tourbillonnaires, sur les sections de Poincaré, ainsi que sur la détermination des performances thermo-hydrauliques et de mélange au niveau global et local. Une évaluation expérimentale du comportement hydraulique a été aussi effectuée par le biais de la méthode de distribution des temps de séjour, ce qui a permis de valider en partie le modèle numérique choisi dans cette étude. Enfin, la dernière partie de l'étude a été consacrée à l'application des concepts d'intensification étudiés au cas d'un capteur solaire thermique à concentration
The energy efficiency of thermal components and systems, as well as the improvement and development of new technologies, are major challenges today. In this general context, the work of this thesis is aimed at improving the thermal performance and mixing of multifunctional heat exchanger-reactors, which are more than ever key components. To achieve this goal, a passive intensification technique has been explored, involving the application of two types of macro-wall deformations on the walls of a laminar flow annular tube. The study initially focused on characterizing the secondary flows created by each of the deformations applied separately in order to enhance heat transfer.Subsequently, a combination of successive and alternating radial deformations on the outer wall, coupled with a geometry that induces swirl motion on the inner wall, significantly increased mixing by promoting chaotic advection within the flow. The understanding of the underlying physical mechanisms relied on numerical analysis of local thermal and hydraulic fields, identification of vortical structures, Poincaré sections, as well as the determination of thermo-hydraulic and mixing performance at both global and local levels. An experimental evaluation of hydraulic behavior was also conducted using the residence time distribution method, partially validating the chosen numerical model in this study. Finally, the last part of the study was dedicated to the application of the intensification concepts studied to the case of a concentrated solar thermal collector

Honeycombs are discrete materials at the macro scale level but their mechanical properties need to be calculated as a continuum material in order to simplify their design in engineering applications. The effective mechanical properties of honeycombs subjected to quasi-static loading were studied by analytical and numerical means and correlated with experimental results for aluminum honeycombs. In particular, the effective in-plane elastic moduli of honeycombs were studied as a function of their relative density and the full range for the relative density was divided into three regions. Beam models that account for bending, shear and axial deformations and finite element analyses (FEA) of the discrete structure composed of beam and two-dimensional solid elements were correlated with experiments of honeycombs with various relative densities for all regions. It was shown experimentally that the beam models describe well the material response in the direction of the double wall. However, it concludes that the behavior of honeycombs with high relative density can not be described by wall stretching as anticipated in previous reported studies.