Sarah Khaleel Ibrahim
57219208688
Publications - 14
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
Analytical Study of Steel-Polypropylene Hybrid Fibre-Reinforced Concrete Deep Beams with Different Shear Span-to-Depth Ratios
Publication Name: Advances in Transdisciplinary Engineering
Publication Date: 2024-01-01
Volume: 59
Issue: Unknown
Page Range: 406-414
Description:
This study explores the performance of steel-polypropylene hybrid fibrereinforced concrete deep beams across various shear span-to-depth ratio values. Combining the ductility of steel fibres with the crack control properties of polypropylene fibres, the research includes experimental work and numerical calibration using ABAQUS. Various parameters, including load locations and shear span-to-depth ratios (0.5 < a/d < 1.5), are considered alongside different steelpolypropylene fibre ratios. The results indicate that reducing the shear span-to-depth ratio enhances the shear strength of the deep beams and reduces deflection values. additionally, the steel-polypropylene fibres influence the overall behaviour, affecting the load-deflection behaviour and damage patterns highlighting insights for designing efficient deep beams in practical applications.
Open Access: Yes
DOI: 10.3233/ATDE240573
Reliability‑based probabilistic numerical plastically limited analysis of reinforced concrete haunched beams
Publication Name: Scientific Reports
Publication Date: 2023-12-01
Volume: 13
Issue: 1
Page Range: Unknown
Description:
This research proposes a novel method that considers the optimal reliability-based design of reinforced concrete haunched beams subjected to probabilistic concrete properties and complementary strain energy values. The theory is applied twice, once to evaluate a deterministic solution, where the plastic behaviour is constrained by the complementary strain energy of residual stresses induced within steel bars. Secondly, the same method is considered for a probabilistic solution where the concrete characteristics—compressive strength and modulus of elasticity—and complementary strain energy value vary randomly. The reliability index acts as a bound for the solution. It is important to mention that the model utilised in this publication is derived from recent research after being calibrated using Abaqus. This work represents an extension of that recent research that exclusively considered deterministic work. This research led deterministically to new estimates for the complementary strain energy, which will be interpreted as reflecting the behaviour of plastic thresholds and quantifying the associated loads. Afterwards, uncertainty is studied when probability interferes, showing various load values and damage in concrete and steel when the complementary strain energy and concrete properties are probabilistically evaluated, giving a less reliable solution as the load reduces. These effects are reflected in the varying plastic behaviour of the investigated haunched beams.
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
Optimal Plastic Reliable Design of Reinforced Concrete Beams Considering Steel Bars Volume Probability
Publication Name: Mathematics
Publication Date: 2023-05-01
Volume: 11
Issue: 10
Page Range: Unknown
Description:
This paper aims to investigate the plastic response of reinforced concrete tapered beams when subjected to random steel reinforcement volumes, using both deterministic and probabilistic analyses, with the complementary strain energy as a boundary in the first case, and the reliability index as a boundary in the second. The first step in this study was to use a previously studied model and perform a deterministic analysis, assuming that the complementary strain energy is a limiting factor and controller of the plastic behaviour. Next, a probabilistic analysis is applied, with the reliability index as a limitation. At the same time, the volume of the reinforcement steel used, and the complementary strain energy were treated as probabilistic variables with mean values and specific standard deviations. This novel method highlighted the plastic behaviour limiting procedure and provided results that highlighted the nature of the model’s changed behaviour when the complementary strain energy was controlled and when applying probabilistic properties with reliability index limitation.
Open Access: Yes
DOI: 10.3390/math11102349
Experimental and Numerical Analysis of Steel-Polypropylene Hybrid Fibre Reinforced Concrete Deep Beams
Publication Name: Polymers
Publication Date: 2023-05-01
Volume: 15
Issue: 10
Page Range: Unknown
Description:
This work experimentally and numerically explored how varied steel-polypropylene fibre mixtures affected simply supported reinforced concrete deep beams. Due to their better mechanical qualities and durability, fibre-reinforced polymer composites are becoming more popular in construction, with hybrid polymer-reinforced concrete (HPRC) promising to increase the strength and ductility of reinforced concrete structures. The study evaluated how different combinations of steel fibres (SF) and polypropylene fibres (PPF) affected beam behaviour experimentally and numerically. The study’s focus on deep beams, research of fibre combinations and percentages, and integration of experimental and numerical analysis provide unique insights. The two experimental deep beams were the same size and were composed of hybrid polymer concrete or normal concrete without fibres. Fibres increased deep beam strength and ductility in experiments. The calibrated concrete damage plasticity model in ABAQUS was used to numerically calibrate HPRC deep beams with different fibre combinations at varied percentages. Based on six experimental concrete mixtures, calibrated numerical models of deep beams with different material combinations were investigated. The numerical analysis confirmed that fibres increased deep beam strength and ductility. HPRC deep beams with fibre performed better than those without fibres in numerical analysis. The study also determined the best fibre percentage to improve deep beam behaviour where a combination of 0.75% SF and 0.25% PPF was recommended to enhance load-bearing capacity and crack distribution, while a higher content of PPF was suggested for reducing deflection.
Open Access: Yes
Optimal Elasto-Plastic Analysis of Prestressed Concrete Beams by Applying Residual Plastic Deformation Limitations
Publication Name: Sustainability Switzerland
Publication Date: 2023-04-01
Volume: 15
Issue: 7
Page Range: Unknown
Description:
This work introduces elasto-plastic analysis of prestressed reinforced concrete beams under different prestressing conditions by limiting the residual plastic behaviour inside the steel bars using complementary strain energy. A non-linear optimal method was used to limit residual plastic deformations in steel bars, including prestressed tendons, used to reinforce beams from two previous research investigations. This was considered by using an optimization approach with an objective function to find the maximum loading while applying constraints on the complementary strain energy of residual internal forces in steel elements to control residual plastic deformations. Thus, an elasto-plastic optimization programme was linked to models simulated by ABAQUS, as concrete was calibrated by the concrete damage plasticity (CDP) model. Some variables were considered regarding the force applied inside prestressed tendons and the number of tendons used inside the models. Thus, limits on complementary strain energy affected load values and model damage where an increase in the permissible strain energy value leads to an increase in the corresponding loading values produced; thus, this produces a higher stress intensity in steel and tension-damaged areas in concrete. Based on these data, many comparisons have been made to determine when beams behaved elastically and how they turned into plastic.
Open Access: Yes
DOI: 10.3390/su15075742
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
Limited Optimal Plastic Behavior of RC Beams Strengthened by Carbon Fiber Polymers Using Reliability-Based Design
Publication Name: Polymers
Publication Date: 2023-02-01
Volume: 15
Issue: 3
Page Range: Unknown
Description:
The plastic behavior of strengthened haunched beams utilizing carbon fiber-reinforced polymers (CFRP) was investigated using a probabilistic design that took into account random concrete properties, CFRP properties, and complementary strain energy values, with the reliability index serving as a limiting index, as the proposed method considers a novel method that deals with probabilistic parameters for models with limited plastic behavior designed based on the reliability index. The data used in this research were gathered and evaluated in a recent study on simply supported haunched beams reinforced with carbon fiber-reinforced polymers. The purpose of this research was to use the reliability limitation index for simulated strengthened haunched beams by taking into account randomness in concrete and CFRP properties and the complementary strain energy value, which is considered a plastic behavior controller that provides an illustration of the damage amount within the reinforcement steel bars. The results indicate how randomness affects the behavior of the presented models, which are chosen to have different numbers of CFRP strips. The variable randomness affects load and deflection values where the reliability index value increases as the corresponding load value decrease, reflecting the increased probability of failure in models subjected to higher loading conditions, while tension concrete damage percentages are reflected in the damage pattern presented in the results, showing that as the produced load increases, so does the damage intensity. It is also obvious that the reliability index served as a limitation index while taking concrete characteristics and complementary strain energy as random variables.
Open Access: Yes
Optimal Elasto-Plastic Analysis of Reinforced Concrete Structures under Residual Plastic Deformation Limitations
Publication Name: Acta Polytechnica Hungarica
Publication Date: 2023-01-01
Volume: 20
Issue: 1
Page Range: 45-62
Description:
In this study, an investigation regarding optimal elastic-plastic analysis method of different reinforced concrete (RC) structures is held by applying the residual plastic deformations limitations on the steel bars inside the reinforced concrete. Where different structures, including simple beam and slab, are selected as benchmarks and modelled numerically using ABAQUS in order to calibrate their experimental behaviour according to laboratory tests. Furthermore, concrete damage plasticity (CDP) constitutive model was applied to represent concrete behaviour in the numerical models considered. Then, an objective function was established for optimizing the applied plastic loads for each structure where the process of controlling plastic deformations was carried out by applying constraints on the complementary strain energy of the residual internal forces initiated inside the steel bars. This methodology was applied by authors by writing MATLAB code and linking it with ABAQUS to determine the corresponding applied plastic load for each entered complementary strain energy. Generally, applying optimization problem for each model showed that the complementary strain energy of the residual forces reflects the general behaviour of the structures and may be assumed as a constraint controlling the plastic behaviour of the structures whereas the obtained results indicated how structures acted differently when possessing different complementary strain energy values turning from elastic into elasto-plastic condition and then reaching plastic state.
Open Access: Yes
Limit design of reinforced concrete haunched beams by the control of the residual plastic deformation
Publication Name: Structures
Publication Date: 2022-05-01
Volume: 39
Issue: Unknown
Page Range: 987-996
Description:
In this paper, a novel computational (optimization) model is presented to control the plastic behaviour of reinforced concrete haunched beams using complementary strain energy of residual forces formed inside the steel reinforcing bars. For this purpose, a numerical model validation process was held and then two non-linear optimization problems were outlined. In these optimization problems, different objective functions were considered applying the optimal elasto-plastic analysis and design of haunched reinforced concrete beams aiming to find the maximal loading or the minimum volume of the steel used to reinforce the beams as the plastic deformations are controlled by using constraints on the complementary strain energy of the residual internal forces of the steel bars. Moreover, the effect of these constraints on different haunch angle beams is studied. The applied method is described in terms of nonlinear mathematical programming and providing solutions when the plastic reserves of the body are not fully exhausted. It is worth mentioning that in this study a concrete damage plasticity constitutive model is applied in the numerical problems and calibrated in accordance with the data gained from laboratory tests. The optimal solutions of the nonlinear mathematical problems were calculated by MATLAB programming codes written by the authors taking into consideration different objective functions and equality and inequality constraints for each case. Finally, by performing a parametric study, the different optimization problems showed how beams behaved differently under different complementary strain energy limit values shifting from elastic into elasto-plastic state and then reaches the fully plastic state where results showed different comparisons taking into consideration the effect of the different complementary strain energy limit values on the maximum applied load, geometry of the beam and steel volume used to reinforce the beams. Thus, complementary strain energy limit value is used to control the plastic deformation inside steel bars during loading progress where avoiding the formation of the plastic deformation in the steel bars would reflect on the general behaviour of the haunched reinforced concrete beams.
Open Access: Yes
Optimal plastic analysis and design of pile foundations under reliable conditions
Publication Name: Periodica Polytechnica Civil Engineering
Publication Date: 2021-07-13
Volume: 65
Issue: 3
Page Range: 761-767
Description:
In this research, in order to evaluate the plastic limit load and also plastic design parameters of the long pile foundations subjected to horizontal loads, shakedown method is applied. In carrying out shakedown analysis and design methods, large plastic deformations and residual displacements could develop in the pile foundation which might lead to the failure of the structure. For this reason, complementary strain energy of residual forces proposed as a limit condition to control the plastic deformation of the pile structure. Furthermore, considering the uncertainties (strength, manufacturing, geometry) the limit conditions on the complementary strain energy of residual forces are assumed randomly and the reliability condition was formed by the use of the strict reliability index. The influence of the limit conditions on the plastic limit load and design parameters of the long pile in cohesionless soil subjected to lateral load were investigated and limit curves for shakedown load factors are presented. The numerical results show that the probabilistic given limit conditions on the complementary strain energy of residual forces have significant influence on the load bearing limit and the design parameters of pile foundations. The formulations of the reliability based problems lead to mathematical programming which were carried out by the use of non-linear algorithm.
Open Access: Yes
DOI: 10.3311/PPci.17402
Numerical plastic analysis of non-prismatic reinforced concrete beams strengthened by carbon fiber reinforced polymers
Publication Name: Proceedings of the 2020 Session of the 13th Fib International Phd Symposium in Civil Engineering
Publication Date: 2020-01-01
Volume: Unknown
Issue: Unknown
Page Range: 208-215
Description:
The non-prismatic reinforced concrete (RC) beam considered a unique case in structural engineering as it has variable depth all over beam section and it doesn't have sufficient information in structural codes, this can put structural engineers in a challenge to predict how this beam will react under specific types of loads or with different geometrical variables and strengthening existence. In this research, concrete plastic damage constitutive model developed and used to explore the shear strength of non-prismatic RC beam structure. Furthermore, in order to improve the shear strength of existent RC beams, Carbon Fiber Reinforced Polymers (CFRP) strips are attached to the surface of the critical sections. For this aim, initially numerical model was calibrated according to the data obtained from laboratory tests then a series of numerical simulations with different variables are carried out to investigate the shear behavior and these variables were: haunch angle a value and CFRP strips existence (composite status). The numerical results show that changing beams geometry (haunch angle a value) can have an influence over shear strength, in addition, using CFRP strips has an obvious effect on the failure behavior of the non-prismatic RC beam structure. Finite element simulations are executed by using ABAQUS.
Open Access: Yes
DOI: DOI not available
Numerical plastic analysis of non-prismatic reinforced concrete beams strengthened by carbon fiber reinforced polymers
Publication Name: Fib Symposium
Publication Date: 2020-01-01
Volume: Unknown
Issue: Unknown
Page Range: 208-215
Description:
The non-prismatic reinforced concrete (RC) beam considered a unique case in structural engineering as it has variable depth all over beam section and it doesn’t have sufficient information in structural codes, this can put structural engineers in a challenge to predict how this beam will react under specific types of loads or with different geometrical variables and strengthening existence. In this research, concrete plastic damage constitutive model developed and used to explore the shear strength of non-prismatic RC beam structure. Furthermore, in order to improve the shear strength of existent RC beams, Carbon Fiber Reinforced Polymers (CFRP) strips are attached to the surface of the critical sections. For this aim, initially numerical model was calibrated according to the data obtained from laboratory tests then a series of numerical simulations with different variables are carried out to investigate the shear behavior and these variables were: haunch angle α value and CFRP strips existence (composite status). The numerical results show that changing beams geometry (haunch angle α value) can have an influence over shear strength, in addition, using CFRP strips has an obvious effect on the failure behavior of the non-prismatic RC beam structure. Finite element simulations are executed by using ABAQUS.
Open Access: Yes
DOI: DOI not available
