Dániel Harrach
57219947503
Publications - 12
Laboratory and Numerical Investigation of Pre-Tensioned Reinforced Concrete Railway Sleepers Combined with Plastic Fiber Reinforcement
Szabolcs Fischer
Mykola Sysyn
Zoltán Major
Sarah Khaleel Ibrahim
Dmytro Kurhan
Vivien Jóvér
Szabolcs Szalai
Hanna Csótár
Klaudia Madarász
András Pollák
Dániel Harrach
Bálint Molnár
L. Gaspar
Bence Hermán
Szabolcs Kocsis Szurke
Attila Németh
I. Fekete
Richárd Nagy
Gusztáv Baranyai
Miklós Kuczmann
M. Movahedi Rad
Publication Name: Polymers
Publication Date: 2024-06-01
Volume: 16
Issue: 11
Page Range: Unknown
Description:
This research investigates the application of plastic fiber reinforcement in pre-tensioned reinforced concrete railway sleepers, conducting an in-depth examination in both experimental and computational aspects. Utilizing 3-point bending tests and the GOM ARAMIS system for Digital Image Correlation, this study meticulously evaluates the structural responses and crack development in conventional and plastic fiber-reinforced sleepers under varying bending moments. Complementing these tests, the investigation employs ABAQUS’ advanced finite element modeling to enhance the analysis, ensuring precise calibration and validation of the numerical models. This dual approach comprehensively explains the mechanical behavior differences and stresses within the examined structures. The incorporation of plastic fibers not only demonstrates a significant improvement in mechanical strength and crack resistance but paves the way for advancements in railway sleeper technology. By shedding light on the enhanced durability and performance of reinforced concrete structures, this study makes a significant contribution to civil engineering materials science, highlighting the potential for innovative material applications in the construction industry.
Open Access: Yes
ADVANTAGES OF USING CONCRETE CANVAS MATERIALS IN RAILWAY TRACK CONSTRUCTION
Publication Name: Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu
Publication Date: 2024-01-01
Volume: Unknown
Issue: 1
Page Range: 50-57
Description:
Purpose. Justification of the feasibility of using new types of drainage materials, such as Concrete Canvas (CC), under the upper structure of the railway permanent way. Methodology. The tasks were solved by a complex research method, including analysis and generalization of literary and patent sources, analytical, experimental studies, using computer and mathematical modeling methods. Tests were conducted with and without the CC layer in a multi-level shear box. After the shear test, the specimens were also tested for load-bearing capacity (E2 , according to the Hungarian standard) and particle breakage. The contact surface between the bottom of the ballast and the CC was measured using a precision 3D laser scanner (GOM ATOS) and visualized graphically using AutoCAD software. Findings. Experimental testing of the vertical load during connection and analysis compared with the test results of geocomposite/geogrid structures, internal shear resistance, and other parameters proved the structure’s higher load-bearing capacity with the CC layer. Based on the results, the Concrete Canvas structure provides higher reinforcement than the average geogrid type. Originality. The advantages of using new Concrete Canvas materials in the structure of a railway track have been demonstrated for the first time to provide greater internal shear resistance than the average for geogrids. Practical value. These results may provide primary data for using Concrete Canvas in railway tracks and superstructures in the future.
Open Access: Yes
Elasto-plastic analysis and optimal design of composite integral abutment bridge extended with limited residual plastic deformation
Publication Name: Scientific Reports
Publication Date: 2023-12-01
Volume: 13
Issue: 1
Page Range: Unknown
Description:
Due to the growing significance of structural theories concerning the composite structure analysed and designed plastically, this paper introduces a new optimisation method for controlling the plastic behaviour of a full-scale composite integral abutment bridge by employing complementary strain energy of residual forces that existed within the reinforcing rebars. Composite bridges are structures made of components such as steel and concrete, which are frequent and cost-effective building methods. Thus, various objective functions were used in this work when applying optimum elasto-plastic analysing and designing the composite integrated bridge structure that was tested experimentally in the laboratory. In contrast, the plastic deformations were constrained by restricting the complementary strain energy of the residual internal forces aiming to find the maximum applied load and the minimum number of steel bars used to reinforce the concrete column part of the structure. The numerical model employed in this paper was validated and calibrated using experimental results, which were considered inside ABAQUS to produce the validated numerical model, using concrete damage plasticity (CDP) constitutive model and concrete data from laboratory testing to solve the nonlinear programming code provided by the authors. This paper presents a novel optimization method using complementary strain energy to control the plastic behaviour of a full-scale composite integral abutment bridge, with the original contribution being the incorporation of residual forces within reinforcing rebars to limit plastic deformations. Following that, a parametric investigation of the various optimisation problems revealed how models performed variously under different complementary strain energy values, which influenced the general behaviour of the structure as it transitioned from elastic to elasto-plastic to plastic; also results showed how the complementary strain energy value is connected with the amount of damaged accrued in both concrete and steel.
Open Access: Yes
Numerical Investigation of Pre-Stressed Reinforced Concrete Railway Sleeper for High-Speed Application
Publication Name: Infrastructures
Publication Date: 2023-03-01
Volume: 8
Issue: 3
Page Range: Unknown
Description:
The current paper deals with the numerical investigation of a unique designed pre-stressed reinforced concrete railway sleeper for the design speed of 300 km/h, as well as an axle load of 180 kN. The authors applied different methodologies in their research: traditional hand-made calculations and two types of finite element software. The latter were AxisVM and ABAQUS, respectively. During the calculations, the prestressing loss was not considered. The results from the three methods were compared with each other. The hand-made calculations and the finite element modeling executed by AxisVM software are adequate for determining the mechanical inner forces of the sleeper; however, ABAQUS is appropriate for consideration of enhanced and sophisticated material models, as well as the stress-state of the elements, i.e., concrete, pre-stressed tendons, etc. The authors certified the applicability of these methodologies for performing the dimensioning and design of reinforced concrete railway sleepers with pre-stressing technology. The research team would like to continue their research in an improved manner, taking into consideration real laboratory tests and validating the results from FE modeling, special material models that allow calculation of crackings and their effects in the concrete, and so that the real pattern of the crackings can be measured by GOM Digital Image Correlation (DIC) technology, etc.
Open Access: Yes
Examination of Concrete Canvas under Quasi-Realistic Loading by Computed Tomography
Publication Name: Infrastructures
Publication Date: 2023-02-01
Volume: 8
Issue: 2
Page Range: Unknown
Description:
The current paper concerns the investigation of CC (Concrete Canvas), a unique building material from the GCCM (geosynthetic cementitious composite mat) product group. The material is suitable for trench lining, trench paving, or even military construction activities, while the authors’ purpose is to investigate the application of the material to road and railway substructure improvement. This research was carried out to verify the material’s suitability for transport infrastructure and its beneficial effects. The authors’ previous study reported that the primary measurements were puncture, compression, and the parameters evaluated in four-point bending (laboratory) tests. However, based on the results, finite element modeling was not feasible because the testing of the composite material in a single layer did not provide an accurate indication. For this reason, the material characteristics required for modeling were investigated. A unique, novel testing procedure and assembly were performed, wherein the material was loaded under quasi-realistic conditions with a crushed stone ballast sample and other continuous particle size distribution samples in a closed polyethylene tube. In addition, the deformation of the material following deformed bonding was measured by computed tomography scanning, and the results were evaluated.
Open Access: Yes
Numerical Investigation of Glue Laminated Timber Beams considering Reliability-based Design
Publication Name: Acta Polytechnica Hungarica
Publication Date: 2023-01-01
Volume: 20
Issue: 1
Page Range: 109-122
Description:
Structural models and their related parameters, are most often considered as deterministic, in numerical analysis. However, according to test results, one can see the existence of uncertainties, in most cases, due to various reasons, such as, natural variabilities and ignorance. Thus, dealing with uncertainty has gained massive attention, due to its importance in structural analysis and anticipating the performance of models. In fact, in some cases of special structure components, like glue laminated timber beams, it appears to be, that there is an absence of information concerning uncertainties. Therefore, the main objective of this study is to inspect uncertainties that facing designers and their role in glue laminated timber beams behavior, by considering different material parameters as random variables. In addition, four-point bending tests are conducted and finite element analysis is conducted, using ABAQUS software, to model the nonlinear behavior of GLT beams. For purposes of numerical model calibration, Hill yield criterion constitutive model is considered based on the obtained data from the experimental test. The results of this study provide a better outline for understanding the effect of uncertainties on glue laminated timber beams.
Open Access: Yes
Comprehensive Laboratory Test Series for Timber-Concrete Composite Structures
Publication Name: Acta Polytechnica Hungarica
Publication Date: 2023-01-01
Volume: 20
Issue: 1
Page Range: 231-250
Description:
Timber-concrete composite structures are not as widespread as traditional steel-concrete fabrications; this structural design still has many critical points that require tests on laboratory specimens. This paper presents the complex testing process of timber-concrete composite structures, which must be followed from the investigation of the possibilities of connecting timber and concrete to each other, through the tests of bended beams acting as timber-concrete composites, to the laboratory tests of full-scale custom-designed timber-concrete composite bridge structures subjected to both concentrated and distributed loads. In this study, to improve the flexural properties of timber beams, carbon fiber-reinforced polymer (CFRP) laminates are attached externally to timber elements. To verify the behavior of the designed structure, we built a full-scale experimental structure and performed a load test. In the laboratory tests, the serviceability limit states, standard loads and load arrangements were investigated. The results of the loading experiments were evaluated. The bridge structures in this article will be placed outdoors after completion of the tests, where they will be used as pedestrian-bicycle bridges. In the case of the examined structures, it was an important aspect, to use elements that are commercially available and suitable for use in the Hungarian design and regulatory systems.
Open Access: Yes
INNER SHEAR RESISTANCE INCREASING EFFECT OF CONCRETE CANVAS IN BALLASTED RAILWAY TRACKS
Publication Name: Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu
Publication Date: 2023-01-01
Volume: Unknown
Issue: 2
Page Range: 64-70
Description:
Purpose. To prove that the GCCM (geosynthetic cementitious composite mat) – type Concrete Canvas (CC) – is an adequate supplementary layer on the top of the subgrade. As its drainage function is known, this article tries to prove the reinforcement possibility. This layer is relatively thin; nevertheless, it can behave like the geogrids. It is the main path to finding out the opportunity of the interlocking effect and its impact on the railway ballast’s inner shear resistance. Methodology. The laboratory measurements were performed in a multilevel shear box, which allows simulating the multilevel shift of the ballast layer. The tests were planned with and without the CC layer. After shearing, the samples were also tested for loadbearing capacity (E2 ; according to the Hungarian Standard) and particle breakage. On the other hand, the contact surface between the lowest part of the ballast and CC was also measured by a sophisticated 3D laser scanner (GOM ATOS) and graphically by AutoCAD software. Findings. After the results of the laboratory experiments are analyzed, the following parameters are calculated and determined: 1) the reinforcement ratio as the tangent of the inner shear resistance curves in the 5–15 mm horizontal shearing interval as well as the area under graphs by integration in the 0–40 mm interval; 2) the change in loadbearing capacity of the layerstructure with and without CC; 3) the amount of the cement particles; 4) the amount of the broken particles; 5) contact surface between the lowest layer of ballast and CC; 6) flatness of CC sheets after shearing. Based on the results, the Concrete Canvas provides significant reinforcement to the railway ballast. Originality. Any other type of measurement with Concrete Canvas in a multilevel shear box is unknown. The topic is unique. Practical value. In the future, these results may provide baseline data to verify the suitability of the Concrete Canvas in the railway sub or superstructure for various types of transport.
Open Access: Yes
Reliability-based numerical analysis of glulam beams reinforced by CFRP plate
Publication Name: Scientific Reports
Publication Date: 2022-12-01
Volume: 12
Issue: 1
Page Range: Unknown
Description:
Most existed researches consider deterministic numerical analysis when dealing with structural models. However, the test results reveal that uncertainties are existing in most cases regarding some considerations such as material randomness and the lack of experience. Therefore, proposing a probabilistic design models have got attention of researchers according to its important role in predicting accurate performance of the structures. The aim of the proposed work is to consider reliability-based analysis in numerical modelling of glulam beams reinforced with CFRP plates as well as unreinforced glulam beams by considering the properties of used timber material as random variables having mean value and standard deviation taking into consideration that the findings of this study have shown that the reliability index is worked efficiently as a limit which controls the process. Hill yield criterion model is adopted with respect to the data which is obtained from the experimental tests in order to validate the models. Furthermore, a detailed comparison between the reinforced and unreinforced glulam beams are proposed to see the effect of introducing the CFRP plates as a reinforcement material. The results of this study have successfully given a deep understanding of how the uncertainties plays a crucial role on the resulted deformations and stresses in which it was founded by making a comparison between deterministic and probabilistic numerical analysis.
Open Access: Yes
Investigation of deformations of ballasted railway track during collapse using the Digital Image Correlation Method (DICM)
Publication Name: Reports in Mechanical Engineering
Publication Date: 2022-01-01
Volume: 3
Issue: 1
Page Range: 168-191
Description:
This paper summarizes the results of laboratory tests in which the authors investigated the effects of extremely high vertical load to a railway track segment. The segment consisted of a cut concrete sleeper (contact area: 290×390 mm) with a pair of direct-elastic rail fasteners; the sleeper pieces had a standard, full height; the structure had a typical 350 mm depth railway ballast, underneath approx. 200 mm sandy gravel supplementary layer. The whole assembly was built in a 2.00×2.20 m area wooden rack. The deformations due to the approx. 150 kN static concentrated vertical force were measured and recorded by Digital Image Correlation Method (DICM), ensuring the GOM ATOS technology. The 150 kN peak load meant 1326 kPa vertical stress at the sleeper-ballast interface. The 3D geometry was scanned before the loading and after the collapse. In this way, the comparison was able to be executed. The maximum vertical deformation was 115 mm. The DICM technique is a relatively new methodology in civil engineering; however, it has been applied for more than ten years in mechanical engineering. Therefore, the authors investigated the applicability of DICM in this field. As a result, the pre and the post-states were determined in 3D. The displacement of the ballast particles was able to be defined with the possibility of drawing the displacement trajectories of given points. The DICM can be a valuable methodology in railway engineering, e.g., laboratory tests and field test applications.
Open Access: Yes
Investigation of the effect of formwork shape on packing density of aggregates
Publication Name: Pollack Periodica
Publication Date: 2020-12-31
Volume: 15
Issue: 3
Page Range: 125-134
Description:
Packing density of aggregate influences greatly the properties of concrete. Maximization of packing density increases the flowing ability and segregation resistance of the fresh concrete and the compressive strength of the hardened concrete. The determination of maximum density is difficult experimentally; therefore several models have been developed for that purpose. However, these models do not take the size of the formwork into account. In this study, 20 different formwork shapes were examined with defined aggregate fractions. Results show that increasing the formwork size increases the packing density of aggregate, and the growth depends on the formwork size and compaction method.
Open Access: Yes
A Method for Measuring Normal and Shear Stiffness of Laminate Stacks of Electric Motors
Publication Name: Periodica Polytechnica Mechanical Engineering
Publication Date: 2023-01-01
Volume: 67
Issue: 2
Page Range: 110-117
Description:
Structural simulations of electric motors require precise material models. Laminate stacks that are made of several identical steel sheets are particularly challenging to simulate using FEA. The structural stiffness of laminate stacks usually follows transversal isotropic behavior. Measuring a complete laminate stack used in passenger cars is challenging due to its size and the high testing load needed to reach real loads experienced while in operation. A new method capable of performing such measurements is presented in this article, with the help of equipment normally used for testing structures used in civil engineering. Two sets of exemplary results are presented utilizing this measurement procedure, that were performed on a real automotive rotor laminate stack: axial compression stiffness from a cyclic test, and shear stiffness at various axial preload levels. In the axial compression load case, the loading and unloading curves form a hysteresis, that changes in every test cycle. Shear stiffness shows high dependance on the axial compression preload. After loading and unloading the stack with shear loads, significant plastic deformations remain.
Open Access: Yes
DOI: 10.3311/PPme.20505
