Wyniki wyszukiwania - BazTech

1

Probabilistic finite element analysis of failures in concrete dams with large asperities in the rock-concrete interface

Ulfberg Adrian, Gonzalez-Libreros Jaime, Das Oisik, Bista Dipen, Westberg Wilde Marie, Johansson Fredrik, Sas Gabriel

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e109, 2023

EN

Common analytical assessment methods for concrete dams are unlikely to predict material fracture in the dam body because of the assumption of rigid body behavior and uniform- or linear stress distribution along a predetermined failure surface. Hence, probabilistic non-linear finite element analysis, calibrated from scale model tests, was implemented in this study to investigate the impact of concrete material parameters (modulus of elasticity, tensile strength, compressive strength, fracture energy) on the ultimate capacity of scaled model dams. The investigated dam section has two types of large asperities, located near the downstream and/or upstream end of the rock-concrete interface. These large-scale asperities significantly increased the interface roughness. Post-processing of the numerical simulations showed interlocking between the buttress and the downstream asperity leading to fracture of the buttress with the capacity being determined mainly by the tensile strength of the buttress material. The capacity of a model with an asperity near the upstream side, with lower inclination, was less dependent on the material parameters of the buttress as failure occurred by sliding along the interface, even with inferior material parameters. Results of this study show that material parameters of the concrete in a dam body can govern the load capacity of the dam granted that significant geometrical variations in the rock-concrete interface exists. The material parameters of the dam body and their impact on the capacity with respect to the failure mechanism that developed for some of the studied models are not commonly considered to be decisive for the load capacity. Also, no analytical assessment method for this type of failure exists. This implies that common assessment methods may misjudge the capacity and important parameters for certain failure types that may develop in dams.

2

Sliding of spherical ball on solid lubricating coating combined with wear process

Białas Marcin, Maciejewski Jan, Kucharski Stanisław

Welding Technology Review

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2021

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R. 93, nr 1

39--50

EN

In present paper we show results of ball-on-disk wear experiment of MoS2 film deposited on Ti6Al4V substrate. The ball material is aluminium oxide. The tests are performed for different surrounding temperature conditions: 20°C, 200°C and 350°C. It is shown that depth of the wear groove increases with increasing surrounding temperature. A finite element modelling approach is next developed to mimic the experimental observations of ball-on-disk wear process. It is based on the assumption of steady state condition developed during short time scale at contact region. The steady state results can next be applied to long time scale in which wear process is numerically simulated. Model results are compared with experimentally obtained wear groove and show satisfactory agreement.

PL

Artykuł prezentuje wyniki testu zużycia powłoki samosmarującej MoS2 nałożonej na podłoże wykonane z materiału Ti6AI4V. Powłoka obciążona jest kulką szafirową w ruchu rotacyjnym. Badania wykonano w trzech różnych temperaturach otoczenia: 20°C, 200°C oraz 350°C. Wykazano, że głębokość rowka zużyciowego wzrasta wraz ze wzrostem temperatury otoczenia. Zaproponowano model metody elementów skończonych za pomocą którego zasymulowany został proces zużycia warstwy. Punktem wyjścia dla tej części pracy było założenie stanu ustalonego, powstającego w obszarze kontaktu pomiędzy kulą a warstwą. Warunki odpowiadające temu stanowi przyjęto do matematycznego opisu procesu zużycia z wykorzystaniem równań Archarda. Na zakończenie eksperymentalny profil zużycia porównany został z wynikami otrzymanymi metodą elementów skończonych.

3

Finite Element Modeling of Self-Compacting Concrete Beams Under Shear

Hosseinimehrab lham, Sadeghi Abbasali, Noroozinejad Farsangi Ehsan

Civil and Environmental Engineering Reports

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2021

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Vol. 31, no. 4

1--16

EN

Development of self-compacting concrete (SCC) is a very desirable achievement in the reinforced concrete (RC) structures for overcoming issues associated with many problems such as congestions of steel reinforcement. This non-vibrating concrete is not affected by the skill of workers, and the shape and amount of reinforcing bar arrangement of a structure. Due to the high fluidity and resisting power of reinforcing of SCC, it can be pumped longer distances. In this study, the finite element (FE) modeling of three SCC beams in shear while taking into account, the flexural tensile strength of concrete is computed and the results are compared with the available experimental tested reinforced SCC beams. The stirrups are located at 75 mm apart from the end of beams up to the loading point. The electrical strain gauges (ESGs) have been embedded on the stirrups and their strain readings are taken for every step of load increment. For modeling longitudinal steel reinforcing bars and concrete, the 3-D elements with 2-node and 8-node, are used respectively. The comparison of results obtained by two methods is indicated that a good satisfactory agreement is achieved.

4

Dynamic crushing behavior of closed-cell aluminum foams based on different space-filling unit cells

Talebi S., Hedayati R., Sadighi M.

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

231--245

EN

Closed-cell metal foams are cellular solids that show unique properties such as high strength to weight ratio, high energy absorption capacity, and low thermal conductivity. Due to being computation and cost effective, modeling the behavior of closed-cell foams using regular unit cells has attracted a lot of attention in this regard. Recent developments in additive manufacturing techniques which have made the production of rationally designed porous structures feasible has also contributed to recent increasing interest in studying the mechanical behavior of regular lattice structures. In this study, five different topologies namely Kelvin, Weaire–Phelan, rhombicuboctahedron, octahedral, and truncated cube are considered for constructing lattice structures. The effects of foam density and impact velocity on the stress–strain curves, first peak stress, and energy absorption capacity are investigated. The results showed that unit cell topology has a very significant effect on the stiffness, first peak stress, failure mode, and energy absorption capacity. Among all the unit cell types, the Kelvin unit cell demonstrated the most similar behavior to experimental test results. The Weaire–Phelan unit cell, while showing promising results in low and medium densities, demonstrated unstable behavior at high impact velocity. The lattice structures with high fractions of vertical walls (truncated cube and rhombicuboctahedron) showed higher stiffness and first peak stress values as compared to lattice structures with high ratio of oblique walls (Weaire–Phelan and Kelvin). However, as for the energy absorption capacity, other factors were important. The lattice structures with high cell wall surface area had higher energy absorption capacities as compared to lattice structures with low surface area. The results of this study are not only beneficial in determining the proper unit cell type in numerical modeling of dynamic behavior of closed-cell foams, but they are also advantageous in studying the dynamic behavior of additively manufactured lattice structures with different topologies.

5

Coupled FEM-microstructural X-ray examination of a controlled internal damage approach for concrete samples

Sidiq Amir, Robert Dilan, Gravina Rebecca, Giustozzi Filippo

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

350--369

EN

One of the critical factors that govern the technology of concrete self-healing evaluation at laboratory scale is the crack induction pattern within the concrete sample. Within the various techniques of inducing artificial cracks, such as the flexural testing or splitting testing methods, there are limitations of inducing the microcracks homogenously throughout the entire volume of the concrete sample. In this study, an innovative technique is utilised to induce the microcracks at a controlled damage level to further study the self-healing phenomena in concrete at the laboratory scale. By placing a concrete sample into an ad-hoc fabricated steel mould and applying fractional compressive strength, the axial-circumferential pressure induces microcracks in the concrete sample, homogenously. A Finite Element Model was also built to investigate the hypothesis on the cracking pattern at various damage levels; jointly, experimental work was conducted with X-ray µCT images to reconstruct the three-dimensional sections at the various damage levels. Qualitative analyses in relation to the two test methods were conducted. Furthermore, quantitative analyses on the individual-artificially generated-cracks were conducted in terms of the crack size crack geometry variation and the orientation of the newly formed cracks. Results revealed that the proposed crack-inducing methodology is highly efficient to induce uniform cracks in the sample, assisting for the evaluation of concrete self-healing process. The novel method can be adapted to identify the optimised strategies for enhancing the structural performance of concrete, thus facilitating the safe operation of concrete infrastructure.

6

A crystal plasticity finite element-based approach to model the constitutive behavior of multi-phase steels

Liu Hongguang, Shin Yung C.

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

707--720

EN

Steels are the most commonly used multi-phase materials in the industry, and their mechanical behaviors depend on the microstructure, composition, and phase fractions. Generally, the material behaviors need to be measured by experiments like a tensile test or split Hopkinson bar test, which is very time-consuming and expensive. Once the heat treatment and phase fractions are changed, it needs to be tested again, and, to avoid this, a better method is required to obtain the material behavior quickly and easily. In this study, a novel multi-scale approach is described to predict the material behaviors of multi-phase steels based on the phase fractions. A crystal plasticity finite element method is used to obtain the material behavior of each phase at a micro-scale with elevated strain rates, which is validated with experimental data or theoretical models at static or quasi-static conditions. Then a homogenization procedure with the rule of mixture method, which is based on the phase fractions measured from the microstructure characterization, is used to get the macro-scale constitutive behavior, and it is then implemented into the commercial software Abaqus/Standard to simulate the process of tensile test and compared with the experimental data. Good agreements are obtained between simulation and experimental results.

7

Seismic Behavior of Earth Dams With Different Reservoir Water Levels Under Near-Field and Far-Field Earthquakes

Asadi Masoud, Soltani Fazlollah, Sinvandi-Pour Abbas, Noroozinejad Farsangi Ehsan

Civil and Environmental Engineering Reports

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2020

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Vol. 30, no. 4

125--141

EN

The height of reservoir water is one of the important factors affecting the seismic behaviour of earth dams. A large number of earth dams have been constructed in different countries that are sometimes located in a high-risk geographical zone. The studies on the seismic behaviour of earth dams have been conducted for several decades. However, this study, considering the importance of the subject, it investigates the seismic behaviour of Sumbar rock-fill embankment dam under near- and far-field earthquakes with variation in the water level behind the dam. The ratio of water height of the dam to dam height is considered as an important indicator to investigate the seismic performance of these structures. The analyses were performed using the ABAQUS finite element platform, under 7 near-field and 7 far-field earthquake records. In this research, the changes in dam stresses, displacements, and failure of the dam have been discussed. The results indicated that the effect of near-field earthquakes on the seismic behaviour of earth dams is more significant than far-field earthquakes.

8

Numerical simulations of ductile fracture in steel angle tension members connected with bolts

Bernatowska Edyta

Civil and Environmental Engineering Reports

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2020

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Vol. 30, no. 2

32--54

EN

Numerical simulations of ductile fracture in steel angle tension members connected with bolts

9

Microstructure evolution and property analysis of commercial pure Al alloy processed by radial-shear rolling

Gamin Yu. V., Akopyan T. K., Koshmin A. N., Dolbachev A. P., Goncharuk A. V.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

674--683

EN

The features of microstructure formation and properties of commercial pure aluminum alloy (Al 99.5%) obtained by radial-shear rolling (RSR) method at the different heating temperatures of 25, 200, 250, 300 and 350 °C were examined. In this paper, the rods with diameter of 14 mm were obtained from initial billet with diameter of 60 mm in five passes. The microstructure analysis with electron backscatter diffraction (EBSD), measurements of microhardness HV over cross-section, and tension test for determination of mechanical properties were carried out for these rods. The FEM simulation of RSR process and calculation of Zener–Hollomon parameter (Z) were carried out with Software QFORM. The obtained rods have the gradient microstructure typical of RSR characterized by surface layer with ultrafine grain structure (UFG) and grain size from 0.3 to 5 µm. In the central part of rod, the fiber deformed structure with minimal fraction of recrystallized grains (< 5%) is formed. This combination is optimal for simultaneous achievement of high strength (UTS ~ 107–110 MPa; YS ~ 100–109 MPa; ~ 35–40 HV) and ductility (El ~ 15–30%). The most intensive growth of plastic properties is observed at rolling temperatures close to the temperature of the onset of recrystallization, it is associated with additional deformational heating of surface layers and the formation of partially recrystallized structure. The obtained distribution dependences of average size of dynamic recrystallized grain on Zener–Hollomon parameter showed that the decrease in parameter Z leads to the increase in size of recrystallized grain for RSR process.

10

Novel shearhead reinforcement for slab-column connections subject to eccentric load and fire

Al-Hamd Rwayda Kh. S., Gillie Martin, Cunningham Lee S., Warren Holly, Albostami Asad S.

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 2

503--524

EN

Traditional means of reinforcing concrete flat slab-column connections against punching shear, such as increasing slab thickness, or provision of shear links, all have drawbacks. This paper proposes a novel type of punching shear reinforcement in the form of a shearhead to enhance connection strength and ductility. The structural behaviour of the connection is explored experimentally by testing nine specimens under various loading conditions including eccentric loads that produce combined axial and bending effects. Specimens with and without shearheads are compared. This is followed by a detailed numerical investigation using finite element analysis to obtain more in-depth insights into the connection behaviour when shearheads are present. The performance of the proposed system is also investigated under fire conditions for the first time. It is found that the proposed shearheads improve the performance of slab-column connections in all conditions and particularly under concentric loading and in fire conditions.

11

Simplified design equation for web tapered I-sections using finite element modeling

Rameshbabu C., Prabavathy S.

Archives of Civil Engineering

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2018

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Vol. 64, nr 3

57--66

EN

The web-tapered I-columns have the capacity to resist the flexural buckling and lateral torsional buckling at a particular location where as in the rest of the member the capacity is lower. There needs a focusing on the nonprismatic members, to find the buckling capacity and standard procedures are to be framed in Indian Code IS 800:2007. This exploratory research explores simulated finite element models covering a total of 60 web tapered column sections having taper ratios (h2/h1) from 1.0 to 3.0 using FEA software ANSYS17.2. With an elaborate Eigenvalue buckling analysis, this research has come up with newer design equation for calculating the buckling load of web tapered I columns. This novel equation could predict the buckling stress for any taper ratio of web tapered I column of any length.

12

Stability Problems of Compressed Thin-Walled Structures

Dębski Hubert

Advances in Science and Technology. Research Journal

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2018

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Vol. 12, no 4

190--198

EN

The object of this study involves thin-walled columns made of carbon-epoxy composite with open top-hat cross-section. The material used comprised a composite of epoxy matrix reinforced with carbon fiber (system HexPly M12, Hexcel). The M12 system is used above all in aircraft structures. It exhibits high fatigue durability and good maintenance properties at relatively low specific gravity. The research was carried out as the FEM numerical analyses and experimental tests in buckling and post-buckling state. The numerical tool used was the ABAQUS software.

13

Modifying the Shape of Blades of a Flexible Reed in a Vibration Beat-up Mechanism – Theoretical Investigation

Kuchar M.

Fibres & Textiles in Eastern Europe

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2017

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Vol. 25, no. 6 (126)

114--118

EN

The beat-up mechanism of a loom with exciters for vibrating motion of the reed is presented. With the placing of exciters at regular distances across the width of the reed, certain differences can be observed in the amplitudes of the vibratory motion of individual blades. Undercutting is proposed here as a method of reducing these differences. The permissible distance between the exciters was determined taking into account the undercut reed. The undulation of the reed in the process of thickening of the wefts is shown to be a consequence of undercutting. For a distance between the exciters of L = 200 mm and relative depth of the undercut h0/h = 0.8, differences in the amplitudes of individual blades do not exceed 10%.

PL

Przedstawiono mechanizm bidłowy krosna ze wzbudnikami ruchu wibracyjnego płochy. Umieszczając wzbudniki w regularnych odstępach na szerokości płochy istnieją różnice w amplitudach ruchu wibracyjnego poszczególnych trzcinek. Zaproponowano podcięcie trzcinek jako sposób na zmniejszenie tych różnic. Biorąc pod uwagę płochę podciętą określono dopuszczalną odległość pomiędzy wzbudnikami. Jako konsekwencje podcięcia ujawniono pofalowanie płochy podczas zagęszczania wątków. Biorąc po uwagę odległość pomiędzy wzbudnikami L = 200 mm oraz względną głębokość podcięcia h0/h = 0,8 różnice w amplitudach ruchu wibracyjnego poszczególnych trzcinek nie przekraczają 10%.

14

Modelling of delamination in composite shellsunder different temperature conditions

Soman R., Ostachowicz W.

Computer Assisted Methods in Engineering and Science

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2017

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Vol. 24, no. 2

127--135

EN

Composite shells and panels are widely used in aerospace structures. These are often subjected to defects and damage from both in-service and manufacturing events. Delamination is the most important damage defect. This paper deals with the computational modelling of delamination in laminated composite shells. The use of three-dimensional finite elements for determining delamination of these structures is computationally expensive. Here combined double-layer and single-layer shell elements are employed to study the effect of delamination on the strain values in the sample under purely bending loads. The computational load and the accuracy of the modelling approaches are compared. It is shown that a through-the-thickness delamination can be modeled and analyzed effectively without requiring a great deal of computing time and memory. Some of the results are compared with the experimental results.

15

Finite Element analysis for Edge-to-Edge Technique to Treat Post-Mitral Valve Repair Systolic Anterior Motion

Zhong Q., Zeng W., Huang X., Zhao X.

Acta of Bioengineering and Biomechanics

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2014

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Vol. 16, no. 4

3--12

EN

Systolic anterior motion of the mitral valve is an uncommon complication of mitral valve repair, which requires immediate supplementary surgical action. Edge-to-edge suture is considered as an effective technique to treat post-mitral valve repair systolic anterior motion by clinical researches. However, the fundamentals and quantitative analysis are vacant to validate the effectiveness of the additional edge-to-edge surgery to repair systolic anterior motion. In the present work, finite element models were developed to simulate a specific clinical surgery for patients with posterior leaflet prolapse, so as to analyze the edge-to-edge technique quantificationally. The simulated surgery procedure concluded several actions such as quadrangular resection, mitral annuloplasty and edge-to-edge suture. And the simulated results were compared with echocardiography and measurement data of the patients under the mitral valve surgery, which shows good agreement. The leaflets model with additional edge-to-edge suture has a shorter mismatch length than that of the model merely under quadrangular resection and mitral annuloplasty actions at systole, which assures a better coaptation status. The stress on the leaflets after edge-to-edge suture is lessened as well.

16

Validation of Fe Modeling of Orthogonal Turning Process Using Cowper–Symonds Material Behavior Law

Gyliene V., Ostasevicius V.

Engineering Transactions

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2013

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Vol. 61, iss. 4

249–-263

EN

The article contains a literature review, experimental results, and a Finite Element Model (FEM) composition. Orthogonal turning tests were executed in the range of cutting speeds and feed rate, after every test chip was collected. Further investigation was done using FE model validation and experimentation, which uses results of the experimental zone in which the built-up edge did not form and the cutting itself is of even plastic deformation. The essence of this research is that the adequacy of the composed FE model to the real physical process should conform not only to the evaluation of cutting forces, but also to the evaluation of chip form, that is, segmentation frequency.

17

Thermo-mechanical model of a TIG welding process for the aircraft industry

Hojny M.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 4

1125--1130

EN

TIG welding is the most important process, which is used in the aircraft industry. A number of components of airplane are made using this method. Thermo-mechanical models are needed to understand better phenomena involved in this process. In the presented work thermo-mechanical simulations were performed and the possibilities of welding distortion in the investigated process were evaluated. Comparison of the results of numerical simulation with the experimental data confirmed good predictive capabilities of the model and quite good description of the phenomena involved in this process.

PL

Spawanie metodą TIG jest jedną z ważniejszych metod używanych w przemyśle lotniczym. Wiele komponentów samolotu powstaje dzięki tej metodzie. Model termo-mechaniczny wspomnianego procesu jest konieczny do dokładnej analizy zjawisk powstających podczas procesu. W prezentowanej pracy opracowano model termo-mechaniczny w kontekście analizy deformacji spawanych elementów. Porównanie otrzymanych wyników na drodze symulacji z wynikami eksperymentalnymi wykazało poprawne odwzorowanie zjawisk zachodzących podczas procesu spawania.

18

Numerical analysis of thermal stresses in carbon films obtained by the RF PECVD method on the surface of a cannulated screw

Sawicki J., Dudek M., Kaczmarek Ł., Więcek B., Świątczak T., Olbrycht R.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 1

77-81

EN

For many years, research on carbon films has been stimulated by the need to simultaneously optimize their biological and mechanical properties and by the challenges related to their deposition on medical implants. The residual mechanical stress occurring inside deposited films is the most important mechanical parameter which leads to the total destruction of these films by cracking and peeling. In the present work, we systematically studied the effect of ion bombardment during the process of radio frequency plasma enhanced chemical vapor deposition (RF PECVD) by monitoring the temperature distribution on a cannulated screw using the infrared technique. The obtained experimental and finite element modeling (FEM) results show that stresses in carbon films deposited on a cannulated screw are quite inhomogeneous and depend on the geometry of the sample and the relative position of the studied contact area between the substrate/film interface and the surface of the film.

PL

Od wielu lat prowadzone są badania mające na celu zredukowanie naprężeń, w węglowych warstwach stosowanych na implanty medyczne, bez pogorszenia własności mechanicznych i biologicznych. Niemniej jednak poznanie mechanizmów wywołujących naprężenia wymaga szczegółowej analizy numerycznej. Wysoka wartość naprężeń mechanicznych występujących w osadzanych warstwach prowadzi poprzez pękanie i odwarstwienie do ich całkowitego zniszczenia, co znacząco organiczna praktyczne wykorzystanie warstw węglowych. W prezentowanej pracy, przeanalizowano wpływ bombardowania jonów podczas procesu plazmochemicznego (RF PECVD) na rozkład temperatury na powierzchni śruby ortopedycznej przy użyciu kamery termowizyjnej. Przeprowadzone eksperymenty i uzyskane rezultaty modelowania (MES) pokazały, ze naprężenia w warstwach węglowych osadzonych na śrubie ortopedycznej sa niejednorodne i zależą od rzeczywistej powierzchni styku pomiędzy podłożem a powłoka jak i geometrii samej próbki.

19

Finite element study on pinning retrofitting technique of masonry walls with opening subjected to in-plane shear load

Shrestha K., Nagae T., Araki Y.

Architecture Civil Engineering Environment

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2011

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Vol. 4, no. 4

81-96

EN

The paper focuses on finite element (FE) modelling of in-plane response of retrofitted masonry walls when subjected to quasi-static in-plane cyclic loading. The retrofit technique involves inserting inclined and horizontal stainless steel bars, already practiced in several historical masonry constructions in Japan. The strength of the pinning technique is ease of construction and it maintains the original appearance of the URM walls. This paper presents a 2D FE model for the retrofitted masonry walls, where continuum elements represent brick units, interface elements represent brick unit/mortar interface, and truss elements represent reinforcing bars. FE model with the proposed simplified equivalent vertical bar model, to represent the inclined inserted reinforcing bars, is validated by comparisons with the experimental results. It was found from the experimental and numerical results that retrofitted specimens showed substantial increment in both strength and ductility and showcased the applicability of the pinning retrofitting technique for historical masonry constructions.

PL

W artykule skoncentrowano się na modelowaniu elementami skończonymi naprawionych ścian murowych poddanych quasi statycznemu, płaskiemu obciążeniu cyklicznemu. Technika naprawy, zastosowana w Japonii w różnych obiektach historycznych o konstrukcji murowej, wymaga wkładania ukośnych i poziomych nierdzewnych prętów stalowych. Zaletą takiej techniki kołkowania jest łatwość wykonania oraz zachowanie niezmienionego wyglądu ścian bez zbrojenia. W artykule przedstawiono dwuwymiarowy model elementów skończonych dla naprawianych ścian murowych, gdzie elementy ciągłe przedstawiają poszczególne cegły, elementy kontaktowe odwzorowują powierzchnię styku cegły i zaprawy, a elementy kratownicowe przedstawiają pręty zbrojenia. Model elementów skończonych z zaproponowanym uproszczeniem zastąpienia prętów ukośnych elementami pionowymi został zweryfikowany przez porównanie z wynikami badań doświadczalnych. Na podstawie wyników badań doświadczalnych i numerycznych stwierdzono, że naprawione elementy wykazują znaczący wzrost wytrzymałości i plastyczności, co potwierdza możliwość stosowania tej metody naprawy w historycznych obiektach o konstrukcji murowej.