Éva Lublóy

54941360800

Publications - 11

Rolling Contact fatigue Defects and a New Approach to Rail Material Management

Éva Lublóy Zoltán Major Szigeti Cecília Róbert Horváth

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2025-01-01

Volume: 22

Issue: 4

Page Range: 227-246

Description:

This article describes the current method of calculating the Hertzian contact stress and the corresponding shear stress occurring in the rail head at the rail-wheel contact and highlights the false sense of security that this approach creates among experts. The authors then present a method that is easy to implement in spreadsheet software and provides realistic results. In light of the results obtained, it is shown that it is not possible to prevent defects induced by the occurring stresses but only to keep them within limits by means of rail machining, which is a realistic objective, without significantly limiting the throughput capacity of the railway track. The combined effects of rail machining and natural wear cause the cross-sectional area and inertia and thus, the load-bearing capacity of the rails to decrease continuously. If the limit is exceeded, the rails may be installed again in less heavily used track sections and continue functioning. At the end of their service life, the track owner sells them as used rail scrap. If possible, recasting them as electro-steels, can significantly reduce the production costs and the amount of CO2 emitted during production.

Open Access: Yes

DOI: DOI not available

Analysis of the Heating of Steel Structures During Fire Load

Dániel Balázs Merczel Éva Lublóy Zoltán Major J. Szép László Bodnár

Publication Name: Emerging Science Journal

Publication Date: 2024-02-01

Volume: 8

Issue: 1

Page Range: 1-16

Description:

During the preparation of our article, we present in detail the changes in the thermotechnical parameters of carbon steel and corrosion resistance during fire. After that, we present in detail the calculation of the heating of steel structures without fire protection. We feel this is important because it is not possible to provide stainless steel with fire protection for aesthetic reasons, and it is also not typical for thin-walled galvanized structures. We also present the calculation of structures with fire protection in detail and present the background for editing commonly used nomograms. Such a nomogram is also available in the literature, but it can be considered true with significant simplifications. During the practical planning, the applied fire protection regulations were highly standardized. Realizing that there is no design nomogram for these types of solutions, we created and published them in our article. The advantage of these is that the applicable design can also be found as the optimum of the designs considered to be potentially good. With this solution, we can save time during planning, and we can also get a more cost-effective solution for the fire protection cover. The advantage of the presented method is that, if required, the editing of the nomograms can be extended to other designs by knowing the material characteristics and the layer thickness. Another option of the presented method is that the solution can also be applied to special fire loads, and nomograms can be produced for them as well (e.g., hydrocarbon fires).

Open Access: Yes

DOI: 10.28991/ESJ-2024-08-01-01

Change in Stiffness of Reinforced Concrete Tunnel Walls and Its Effect Under Fire Load

Edina Koch Éva Lublóy Zoltán Major

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 342-350

Description:

This article uses the knowledge gained from tunnel fires to address the structural analysis of tunnel walls during fire exposure. The designing at normal temperature and its theoretical background are discussed in the literature. As these books did not yet deal with the issue of fire protection designing, we tried to supplement the existing theoretical knowledge with the knowledge provided by the relevant standards for reinforced concrete tunnel walls. In addition, we have tried to add our own individual ideas to the theory where we felt that there were gaps. The theoretical summary has been compiled in such a way that it can be easily transferred and applied to everyday practice. In this article, we discuss in detail the calculation of the internal forces in tunnel walls during fire exposure. Due to space constraints, the issue of designing at normal temperatures is only touched upon in this article, limiting it to the knowledge available in the literature. Since finite element modelling has become a commonly used technique in tunnel design since the 1970s, we use its potential to investigate the effects of earth pressure and surface loads on the tunnel walls during fire and their changes, using specific software for geotechnical design. In accordance with the limitations of the scope, the determination of the equivalent thickness and the modulus of elasticity of the tunnel wall is also presented in order to determine the internal forces during the fire action.

Open Access: Yes

DOI: 10.3233/ATDE240565

Calculation of Heating of Reinforced Concrete Tunnel Wall During Fire

Éva Lublóy Zoltán Major J. Szép

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 366-374

Description:

In this article, we present the thermal parameters of reinforced concrete tunnel lining materials and their changes during fire exposure. After describing the material properties, we present a test method to investigate the heating of reinforced concrete tunnel linings. As the presented method can only be considered as partially standard, we validate it on the basis of the available literature and our Excel program based on the presented theory. During the validation, it has been demonstrated that the method is suitable for solving practical professional tasks and that it is able to provide sufficiently accurate results. Since the results presented can be used not only for design purposes but also as an initial step in fire diagnostics to determine the extent of damage in fire-loaded tunnel walls, we also construct novel curves for the analysis of reinforced concrete walls, which can be used effectively for fire curves with cooling phase, where the accumulated temperature inside the wall further heats the zones inside and further residual strength loss may occur due to chemical processes in the zones. Based on the results of the model presented in this paper, designers can take into account the changes in the temperature distribution of the reinforced concrete tunnel wall, which have a decisive influence on the evolution of the internal forces due to external influences, and can calculate the magnitude of the stresses due to inhibited thermal expansion by using approximate models.

Open Access: Yes

DOI: 10.3233/ATDE240568

Calculation of Thermal Stresses of Cast Iron Tubbings Under Fire Effect

Éva Lublóy Zoltán Major J. Szép

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 431-437

Description:

This article builds on our existing knowledge of the heating of cast iron tunnel linings and deals with the structural analysis of tunnel linings under fire exposure. Due to space constraints, we do not address the issue of sizing for earth pressure and surface loads. Since the analysis of thermal stresses due to restrained deformations is insufficient in the available literature, we will try to complement the existing theoretical knowledge with the knowledge provided by the relevant standards for cast iron lining of tunnels. In addition, we will try to add our own individual reflections to the theory where we have identified gaps. The theoretical summary is compiled in such a way that it is easily transferable and applicable to everyday practice. Our finite element analysis shows that the value of the embedding factor has a small effect on the development of the axial constraint stresses in the tunnel direction, while in the ring direction has a significant effect. In all cases, stiffer embedding results in higher stress values. In all cases, the ring direction compressive stresses are lower than the longitudinal stresses due to the deformation of the tunnel ring. There is no literature data available on the value of the compressive stresses, so we have tried to provide some indicative data in tabular form for the profession. The solution adopted and the values proposed are based on the authors' individual ideas and are not the result of an accepted professional consensus. In all cases where more precise data are required, it is recommended that a more detailed study be carried out. Finite element modelling can provide the necessary support for designers and experts.

Open Access: Yes

DOI: 10.3233/ATDE240576

Calculation Possibilities of the Local Fire Effect for the Examination of Bridge Superstructures

Éva Lublóy Zoltán Major J. Szép

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 382-388

Description:

For the examination of bridge superstructures, there is no single standard method in the literature for the design of structures, and possibility for their diagnosis after fire damage. Designers often overcome this problem by examining the fire curves used for tunnel fires, as the materials feeding the combustion are considered to be very similar. In contrast, in some articles, the use of localised fires in design and control is suggested by the authors. This is a standard method used in Eurocode. To solve the problem, two methods must be applied. Heskestad's method describes the case where the flame does not reach the superstructure of the bridge, while Hasemi's method describes the case where the flame does. Heskestad's method is presented in the standard in a way that can be used by practising engineers. The great advantage of Hasemi's method is that it can quantify the effects of several localised fires, each one separate from the other. This feature is very useful for the fire design of, for example, covered car parks and bridge structures. In such a test, the total heat flow on the lower plane of the slab or superstructure can be interpreted as the sum of the heat flows from each local fire. The standard, on the other hand, it does not provide additional assistance to designers in solving the problem. That is way, he should be able to determine the temperature of the structural element, a method which is not provided for in the standard. This problem leads to a fourth degree equation, which again leaves the designer on his own to solve. There is no formula for solving the fourth degree equation. In this case, it becomes more useful to find a sufficiently accurate approximate solution (Newton's method) rather than an exact solution. In this article, we present in detail the possibilities of solving the local fire effect in order to enable practising engineers to use it.

Open Access: Yes

DOI: 10.3233/ATDE240570

The Impact of Cement Aggregates on the Fire Resistance Properties of Concrete and its Ecological Footprint

Éva Lublóy Zoltán Major J. Szép Szigeti Cecília

Publication Name: Chemical Engineering Transactions

Publication Date: 2023-01-01

Volume: 107

Issue: Unknown

Page Range: 337-342

Description:

The strength properties of concrete are significantly influenced by the type of binder used. In the case of cement, the use of cement-containing admixtures (CEM II) is becoming increasingly popular from a durability and environmental point of view. The first question was how cements containing different admixtures behave and how their compressive strength changes under high temperatures (fire). First, the experiments were carried out with the cement tests, and then the concrete specimens were checked for the extent to which the addition of admixtures modifies the favourable effect measured for cement. Under thermal loading, the value of the residual compressive strength of the cement paste increased with the addition of the admixture content. The results of the compressive strength test and the developed crack patterns were consistent with each other. The most severe cracking was observed in the Portland cement specimens, and the decrease in strength was also the most significant. Based on the results of the cement tests, several types of cement were used for the concrete tests. The second research question was: Which concrete recipe has the lowest specific ecological footprint? Therefore, for each formulation, the specific ecological footprint is crucially influenced by the type and amount of substitute used, as their specific CO2 emissions are typically lower than those of Portland cement. Based on our previous studies, a reduction in the specific ecological footprint of up to 10 % can be achieved by using substitutes. The novelty of our research lies in the combined use of fire resistance and ecological aspects, which helps to select a formulation with better technical properties and, at the same time, more sustainable.

Open Access: Yes

DOI: 10.3303/CET23107057

The effect of macrostructure and stability on the flammability of non-woven fabrics

Éva Lublóy Katalin Kopecskó J. Szép Zsuzsanna Kerekes

Publication Name: Journal of Industrial Textiles

Publication Date: 2022-06-01

Volume: 51

Issue: 5_suppl

Page Range: 8472-8489

Description:

The most flame retardants and non-combustible non-woven fabrics are made of oxidized and carbon fibres due to their strong thermal stability. The burning of non-woven fabrics consists of complex combustion mechanisms: their surface, micro and macrostructures together define their combustion features. By microstructure, we mean oxidized polyacrylicnitrile fibres, which finally constitute the base material of the macrostructure. The macrostructure represents the different forms of the product, in which the material results during production. In this paper, the effect of the macrostructure of non-woven fabrics on flammability has been studied. It has experimentally shown that by defining the oxygen index, we can demonstrate the surface and thickness inhomogeneity, which is invisible or cannot be detected by mechanical tests. A feature of non-combustible non-woven fabrics is that their flammability depends on their thickness and area weight; however, the combustion phenomena of felt fabrics depend primarily on their macrostructure. Different oxygen contents have different combustion phenomena, thus an oxygen index can be assigned to each one. Thermoanalytical test results clearly showed the temperature at which the thermal decomposition of the fibres begins, which gives the surface flame when combusted.

Open Access: Yes

DOI: 10.1177/1528083720908803

Investigation of steel fibers bond strength in mortar matrix

Éva Lublóy Katalin Halvax

Publication Name: Pollack Periodica

Publication Date: 2013-12-01

Volume: 8

Issue: 3

Page Range: 101-110

Description:

In this paper the results of an investigation about steel fibers bond strength in mortar matrix are presented. Pull-out tests were made with four different types of fibers (hookedend, crimped, flat-end, anchoraged), the fibers were embedded individually into a cement based sample with three different embedded length (10, 15, 20 mm). Another variable parameter of the experiment was the strength of the matrix (three different mixture were used), and hooked-end fibers with higher tensile strength and zinc surface coating were tested also. During the tests pull-out force and displacement were measured.

Open Access: Yes

DOI: 10.1556/Pollack.8.2013.3.10

Conservative Method for the Calculation of Thermal Forces in Reinforced Concrete Tunnel Wall During Fire

Éva Lublóy Zoltán Major J. Szép

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 455-463

Description:

This article builds on the author's existing knowledge of the heating of reinforced concrete tunnel linings and deals with the structural analysis of tunnel linings under fire exposure. Due to space constraints, the issue of designing for earth pressure and surface loads is not address. Since the analysis of thermal stresses due to restrained deformations is insufficient in the available literature, we complement the existing theoretical knowledge with the knowledge provided by the relevant standards for reinforced concrete tunnel linings. In addition, we add our own individual reflections to the theory where we have identified gaps. In determining the additional stresses due to inhibited thermal expansion, we use a numerical model based on our own ideas. The reason for this is that the heating of reinforced concrete tunnel lining during fire is extremely uneven and it is almost impossible to take this into account in the finite element programs commonly used. The other important reason is that this uneven temperature change that causes the colder zones of the wall to inhibit deformation. Thus, a solution implemented in MS Excel environment is presented, which allows an approximate accurate determination of the force effects due to inhibited deformation. The solution used and the values proposed are based on the authors' individual ideas and are not the result of an accepted professional consensus. In all cases where more precise data are required, it is recommended that a more accurate test be carried out. Advanced finite element modelling can provide the necessary support for designers and experts.

Open Access: Yes

DOI: 10.3233/ATDE240579

The Ecological Footprint and Fire Resistance of Concrete Mixtures

Éva Lublóy Zoltán Major J. Szép Szigeti Cecília

Publication Name: Journal of Sustainable Development of Energy Water and Environment Systems

Publication Date: 2025-09-01

Volume: 13

Issue: 3

Page Range: 1-13

Description:

Different types of binders can significantly affect the strength properties of concrete. The use of cement-containing admixtures is becoming more widespread in the building industry when considering durability and environmental impact. This paper examines how different types of cement containing different admixtures behave. How the compressive strength of concrete changes under elevated temperature, and which concrete mixture has the lowest CO2 emission. To determine the strength parameters, test specimens of 150x150x150 mm and 70x70x250 mm were prepared from the concrete mixtures. After heating and cooling, they were broken, thereby determining the compressive and flexural-tensile strength values. The ecological footprint was calculated for each mixture, which is substantially influenced by specific parameters for example the type and amount of substitute materials. These materials typically have lower CO2 emissions than Portland cement. The novelty of this research lies in the combined investigation of the changing compressive strength of concrete at elevated temperatures and its sustainability. The change in the formulation resulted in a saving of the emission of ~10% (43.22 kgCO2e emissions) compared to the reference value. The importance of reducing the ecological footprint is demonstrated by the authors using a case study of the Gotthard tunnel.

Open Access: Yes

DOI: 10.13044/j.sdewes.d13.0597