جامعة بلاد الرافدين - Bilad Alrafidain University - م.م محمد جلال عبدالله

م.م محمد جلال عبدالله

Asst. Lect. Mohammed Jalal Abdullah

تدريسي : قسم الهندسة المدنية

Teaching : DEPARTMENT OF CIVIL ENGINEERING

دكتوراه في الهندسة

PhD. in engineering

mohammedjalal@bauc14.edu.iq

Eng.mj96@hotmail.com

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	2025	Buildings
Blast damage to structural members poses serious risks to both buildings and people, making it important to understand how these elements behave under extreme loads. Columns in reinforced concrete (RC) structures are especially critical, as their sudden failure can trigger progressive collapse, unlike beams or slabs that have more redundancy. This state-of-the-art review brings together the current knowledge of the blast response of RC columns, focusing on their failure patterns, dynamic behavior, and key loading mechanisms. The studies covered include experiments, high-fidelity numerical simulations, emerging machine learning approaches, and analytical models for columns of different shapes (square, rectangular, circular) and strengthening methods, such as fiber reinforcement, steel-concrete composite confinement, and advanced retrofitting. Composite columns are also reviewed to compare their hybrid confinement and energy-absorption advantages over conventional RC members. Over forty specific studies on RC columns were analyzed, comparing the results based on geometry, reinforcement detailing, materials, and blast conditions. Both near-field and contact detonations were examined, along with factors like axial load, standoff distance, and confinement. This review shows that RC columns respond very differently to blasts depending on their shape and reinforcement. Square, rectangular, and circular sections fail in distinct ways. Use of ultra-high-performance concrete, steel fibers, steel-concrete composite, and fiber-reinforced polymer retrofits greatly improves peak and residual load capacity. Ultra-high-performance concrete can retain a significantly higher fraction of axial load (often >70%) after strong blasts, compared to ~40% in conventional high-strength RC under similar conditions. Larger sections, closer stirrups, higher transverse reinforcement, and good confinement reduce spalling, shear failure, and mid-height displacement. Fiber-reinforced polymer and steel-fiber wraps typically improve residual strength by 10–15%, while composite columns with steel cores remain stiff and absorb more energy post-blast. Advanced finite element simulations and machine learning models now predict displacements, damage, and residual capacity more accurately than older methods. However, gaps remain. Current design codes of practice simplify blast loads and often do not account for localized damage, near-field effects, complex boundary conditions, or pre-existing structural weaknesses. Further research is needed on cost-effective, durable, and practical retrofitting strategies using advanced materials. This review stands apart from conventional literature reviews by combining experimental results, numerical analysis, and data-driven insights. It offers a clear, quantitative, and comparative view of RC column behavior under blast loading, identifies key knowledge gaps, and points the way for future design improvements.

	2025	Buildings
A touch-off explosion on concrete slabs is considered one of the simplest yet most destructive forms of adversarial loading on building elements. It causes far greater damage than explosions occurring at a distance. The impact is usually concentrated in a small area, leading to surface cratering, scabbing of concrete, and even tearing or rupture of the reinforcement. Studies available on the behavior of reinforced concrete (RC) slabs under touch-off (contact) and standoff explosions commonly indicate that the maximum damage occurs when the blast is applied to the center of the slab. This observation raises an important question about how the position of an explosive charge, especially relative to the free edge of the slab, affects the overall damage pattern in slabs supported on only two sides with clamped supports. This study uses a modeling strategy combining Eulerian and Lagrangian domains using the finite element tools of Abaqus Explicit v2020 to examine the behavior of a square slab supported on two sides with clamped ends subjected to blast loads at different positions, ranging from the center to the free edge and beyond, under touch-off explosion conditions. The behavior of concrete was captured using the Concrete Damage Plasticity model, while the reinforcement was represented with the Johnson–Cook model. Effects of strain rate were included by applying calibrated dynamic increase factors. The developed numerical model is validated first with experimental data available in the published literature for the case where the explosive charge is positioned at the slab’s center, showing a very close agreement with the reported results. Along with the central blast position, five additional cases were considered for further investigation as they have not been investigated in the existing literature and were found to be worthy of study. The selected locations of the explosive charge included an intermediate zone (between the slab center and free edge), an in-slab region (partly embedded at the free edge), a partial edge (partially outside the slab), an external edge (fully outside the free edge), and an offset position (250 mm beyond the free edge along the central axis). Results indicated a noticeable transition in damage patterns as the detonation point shifted from the slab’s center toward and beyond the free edge. The failure mode changed from a balanced perforation under confined conditions to an asymmetric response near the free edge, dominated by weaker surface coupling but more pronounced tensile cracking and bottom-face perforation. The reinforcement experienced significantly varying tensile and compressive stresses depending on blast position, with the highest tensile demand occurring near free-edge detonations due to intensified local bending and uneven shock reflection.

	2025	Discover Sustainability
Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) represents one of the most advanced construction materials, characterized by extremely high strength, compact microstructure, and higher resistance to environmental degradation. With optimized particle packing and fiber reinforcement, UHPFRC commonly achieves compressive strengths of 150–200 MPa and tensile strengths of 10–35 MPa. Autoclave curing or heat treatment can further increase the compressive strength to above 250 MPa. The dense matrix, typically with porosity below 6% and water absorption under 1%, provides exceptional durability against chloride ingress, freeze–thaw cycles, and sulfate attack. Increasing the fiber volume fraction from 1 to 3% generally enhances post-cracking toughness and flexural strength by 40–80%. Conversely, an excessively low water-to-binder ratio (< 0.18) or improper curing can increase autogenous shrinkage by up to 30%. Despite these achievements, widespread application remains constrained by high initial cost, limited codified guidance, and inadequate field experience. This review critically analyzes the mechanical, durability, and constitutive behavior of UHPFRC, the influence of mix design and curing parameters, existing codes and standards, and representative case studies. It further identifies the gaps in current design frameworks and proposes directions for future research aimed at facilitating the large-scale use of UHPFRC in durable and resilient infrastructure.

	2025	IOS Press Ebooks
Explosions, regardless of their origin, have a significant impact on building structures, with the severity and spread of blast pressures being influenced by several factors. Among these, the orientation of the explosive, in addition to its mass, geometry, and direct or indirect interaction with the target, plays a critical role in determining the extent of the damage. Existing literature has primarily focused on blast tests involving explosives placed horizontally, leaving the effects of vertical alignment, particularly with brick-shaped charges, largely unexplored. The increasing frequency of hostile attacks, advanced warfare techniques, and explosive incidents accentuate the need for a comprehensive analysis that accounts for varying explosive orientations to better predict structural responses and enhance resilience. The present study aims to numerically investigate the impact of vertical tilting (from 0° to 75°) of Trinitrotoluene (TNT) explosives on the blast behavior of one-way slabs. To ensure accuracy of employed Abaqus software, the study’s findings are validated through comparison with experimental data found in existing literature. The findings revealed that when the TNT charge was laid flat, the resulting pressure wave moved outward in a mainly tangential or slanted manner, causing a broader yet shallower impact across the slab surface. However, as the orientation of the explosive shifted upward from horizontal to nearly vertical (0° to 75°, at 15° intervals), the pressure front began striking the surface more directly. This led to significantly amplified reflected pressure, overshadowing the initial compression effects. These findings have significant implications for improving safety protocols and structural design strategies in regions vulnerable to explosive threats.

	2025	Discover Materials
Using plant-based fibers in concrete composites has significantly contributed to the eco-friendliness and sustainability of the construction sector. However, the vulnerability of natural-fiber reinforced concrete (NFRC) to elevated temperatures is a critical concern as its global usage continues to increase. It is crucial to recognize the residual characteristics of NFRC to establish safe design standards and ensure its suitability for various applications. While studies have extensively reviewed the behavior of manufactured and steel-fiber concrete subjected to fire, there is a notable absence of research systematically addressing the performance of NFRC under high-temperature conditions. This review bridges that gap by synthesizing findings from over 120 studies, providing the first comprehensive evaluation of NFRC degradation patterns, thermal cracking behavior, spalling mitigation mechanisms, and the influence of fiber type, treatment, and hybridization on fire performance. The work offers a comparative framework with synthetic and steel fiber-reinforced concretes, delivering actionable insights for fire safety design and material selection. The findings indicate that the critical temperature range for NFRC is between 350 °C and 450 °C, beyond which spalling can lead to catastrophic damage to surrounding structures. Notably, including 15 mm long jute fibers effectively mitigated thermal spalling. Exposing steel rebars to fire can reduce concrete density, strength, and permeability while increasing stiffness and contributing to spalling. However, incorporating hybrid fibers (steel or synthetic + natural fibers) into high-strength concrete reduced thermal spalling by 43% compared to individual additions of steel or synthetic fibers and natural fibers. Additionally, the review highlights that coconut fibers exhibited the most improved compressive strength among all-natural fibers under heating conditions. Lignocellulosic fibers (such as sisal, hemp, coconut, and jute) were observed to effectively mitigate micro-cracking and violent spalling in ultra-high-performance, high-strength, and high-performance concrete, in contrast to concrete without natural fibers.

	2025	International Journal of Low-Carbon Technologies
To address the limitations of conventional concrete, such as low ductility and toughness, high-performance fiber-reinforced concrete (HPFRC) incorporates fibers into a cementitious matrix. However, traditional HPFRC production using natural aggregates and industrial fibers depletes resources and increases environmental impact. This study explores a sustainable alternative by developing high-performance coconut fiber-reinforced concrete with 35% and 70% coarse recycled aggregates (RA) as partial replacements for natural aggregates, combined with 0%, 1.5% and 3% coconut fibers (CFs) by binder volume. The addition of 0.6% polycarboxylate ether-based superplasticizer significantly enhanced mechanical and durability properties. Compressive strength increased by 14.3%, splitting tensile strength by 19.2% and shear strength by 41.4%. Durability against freeze–thaw cycles and acid attacks improved, with an 18.6% increase in residual compressive strength and 18.5% enhancement in acid resistance. While CFs and RA initially increased water absorption and chloride ion permeability, superplasticizers mitigated these effects, improving overall durability. The synergistic use of CFs and superplasticizers enhanced resistance to environmental degradation, enabling RA to perform effectively under harsh conditions. This approach demonstrates the potential of integrating recycled aggregates and waste coconut fibers to produce eco-friendly, high-performance concrete for modern construction. The study highlights the balance between mechanical performance, durability and sustainability, offering a cost-effective solution that reduces the carbon footprint and promotes circular economy principles in construction.

	2025
The use of lightweight concrete is gaining prominence in civil engineering because of its effectiveness in minimizing dead loads. However, the increased reliance on concrete has accelerated the depletion of natural resources, raising environmental concerns. This challenge has led to a growing interest in finding sustainable alternatives within the field of civil engineering. This study focuses on the enhancement of bottom ash (BA) to develop a well-graded version (BAW). It examines the impact of replacing fine aggregates with BAW on the mechanical and thermal characteristics of lightweight concrete. The research experimented with different BAW incorporation levels, ranging from 5 % to 35 % by volume. The results showed a consistent decrease in concrete density with increasing BAW replacement, as well as varying changes in mechanical and thermal performance across the tested range of 0–35 % by volume. Mechanical and thermal properties peaked at 15 % before falling. Compressive strength peaked at 36.7 MPa at 15 % and dropped to 26.9 MPa at 35 %. Flexural strength increased to 2.85 MPa at 15 % and 2.57 MPa at 35 %. Split tensile strength increased to 0.76 MPa at 15 % and decreased to 0.63 MPa at 35 %. Ultrasonic pulse velocity reached a maximum speed of 3.86 km/s at 15 % and 3.18 km/s at 35 %. Thermal conductivity increased to 1.67 W/m·K at 15 % and dropped to 1.06 W/m·K at 35 %. The 15 % BAW level optimizes performance, whereas higher replacement rates increase porosity. These findings indicate that well-graded BA enhances the properties of concrete, offering reliable and sustainable material for use in modern construction.

	2025	Buildings
Blast damage to structural members poses serious risks to both buildings and people, making it important to understand how these elements behave under extreme loads. Columns in reinforced concrete (RC) structures are especially critical, as their sudden failure can trigger progressive collapse, unlike beams or slabs that have more redundancy. This state-of-the-art review brings together the current knowledge of the blast response of RC columns, focusing on their failure patterns, dynamic behavior, and key loading mechanisms. The studies covered include experiments, high-fidelity numerical simulations, emerging machine learning approaches, and analytical models for columns of different shapes (square, rectangular, circular) and strengthening methods, such as fiber reinforcement, steel-concrete composite confinement, and advanced retrofitting. Composite columns are also reviewed to compare their hybrid confinement and energy-absorption advantages over conventional RC members. Over forty specific studies on RC columns were analyzed, comparing the results based on geometry, reinforcement detailing, materials, and blast conditions. Both near-field and contact detonations were examined, along with factors like axial load, standoff distance, and confinement. This review shows that RC columns respond very differently to blasts depending on their shape and reinforcement. Square, rectangular, and circular sections fail in distinct ways. Use of ultra-high-performance concrete, steel fibers, steel-concrete composite, and fiber-reinforced polymer retrofits greatly improves peak and residual load capacity. Ultra-high-performance concrete can retain a significantly higher fraction of axial load (often >70%) after strong blasts, compared to ~40% in conventional high-strength RC under similar conditions. Larger sections, closer stirrups, higher transverse reinforcement, and good confinement reduce spalling, shear failure, and mid-height displacement. Fiber-reinforced polymer and steel-fiber wraps typically improve residual strength by 10–15%, while composite columns with steel cores remain stiff and absorb more energy post-blast. Advanced finite element simulations and machine learning models now predict displacements, damage, and residual capacity more accurately than older methods. However, gaps remain. Current design codes of practice simplify blast loads and often do not account for localized damage, near-field effects, complex boundary conditions, or pre-existing structural weaknesses. Further research is needed on cost-effective, durable, and practical retrofitting strategies using advanced materials. This review stands apart from conventional literature reviews by combining experimental results, numerical analysis, and data-driven insights. It offers a clear, quantitative, and comparative view of RC column behavior under blast loading, identifies key knowledge gaps, and points the way for future design improvements.

	2024	Buildings
Pultruded glass fiber-reinforced polymer (GFRP) materials are increasingly recognized in civil engineering for their exceptional properties, including a high strength-to-weight ratio, corrosion resistance, and ease of fabrication, making them ideal for composite structural applications. The use of concrete infill enhances the structural integrity of thin-walled GFRP sections and compensates for the low elastic modulus of hollow profiles. Despite the widespread adoption of concrete-filled pultruded GFRP tubes in composite beams, critical gaps remain in understanding their flexural behavior and failure mechanisms, particularly concerning design optimization and manufacturing strategies to mitigate failure modes. This paper provides a comprehensive review of experimental and numerical studies that investigate the impact of key parameters, such as concrete infill types, reinforcement strategies, bonding levels, and GFRP tube geometries, on the flexural performance and failure behavior of concrete-filled pultruded GFRP tubular members in composite beam applications. The analysis includes full-scale GFRP beam studies, offering a thorough comparison of documented flexural responses, failure modes, and structural performance outcomes. The findings are synthesized to highlight current trends, identify research gaps, and propose strategies to advance the understanding and application of these composite systems. The paper concludes with actionable recommendations for future research, emphasizing the development of innovative material combinations, optimization of structural designs, and refinement of numerical modeling techniques.

	2024	Results in Engineering
This study investigates the effect of continuous rectangular spiral shear reinforcement on reinforced concrete slabs under low-velocity conditions, crucial for scenarios such as landslides or vehicular collisions. By combining experimental and finite element analyses using ABAQUS, this research assesses the effectiveness of this reinforcement method. The experimental setup involves subjecting slabs to impact loading with consistent energy levels using a drop weight system. Various parameters, including acceleration time, strain-time in steel and concrete, and failure mode, are carefully monitored throughout the study. Results demonstrate a notable 216.13% improvement in energy absorption and a 43.70% increase in impact ductility compared to control specimens, reflecting higher rigidity and stiffness in spiral-reinforced specimens, as evidenced by elevated maximum acceleration values. Specimens with continuously rectangular spirals exhibit less severe surface damage upon complete failure, emphasizing their enhanced impact resistance. Diagonally arranged spiral reinforcements notably reduce damage, displacement, and stress. These findings highlight the significant potential of continuously rectangular spirals in improving the low-velocity behavior of reinforced concrete slabs, offering valuable insights for structural design and reinforcing systems. Additionally, using ABAQUS finite element analysis validates experimental findings, providing efficient insights into structural behavior under dynamic conditions.

	2023	PERTANIKA JOURNAL OF SCIENCE AND TECHNOLOGY
Concrete is the most widely used construction material in the world. It is now possible to construct structures out of concrete because this durable compound that consists of water, aggregate, and Portland cement not only gives us many scopes of design but also has a very high compressive strength at a low cost. This paper deals with alternative materials for the most common construction material, cement-based concrete and polymer concrete (PC), containing waste tin fibres. The study covers the fabrication of polymer concrete and the execution of three tests: compressive strength, flexural tensile, and splitting tensile. Tests were conducted to determine the mechanical properties of the PC, and the results were analysed and evaluated on several PC specimens with different ratios of waste tin fibre. The results showed that using waste tin as fibre reinforcement in PC would substantially enhance the overall mechanical performance. Specifically, the optimum amount of waste tin as reinforcement in PC was 0.16% for compressive and splitting tensile strengths, while 0.20% was the optimum fibre loading for the flexural tensile strength. In this case, a positive outcome was found at a constant resin-to-filler ratio of 40:60 by volume and a matrix-to-aggregate ratio of 1:1.35 by weight.

	2022	Construction and Building Materials
Bottom ash (BA) is a hazardous waste material from power plant. The well-graded BA can be a good sand replacement material in concrete. This study presents strength and thermal properties of concrete containing high calcium and water absorptive fine aggregate from well-graded BA as partial sand replacement (control mix (CM) 0%, BM5: 5%, BM10: 10%, BM15: 15%, and BM20: 20%). The workability of fresh concrete mixes was tested via slump test. The strength of the hardened concrete was assessed based on compressive strength, split tensile strength, and flexural strength. The thermal property was evaluated based on thermal conductivity test. The optimization of these model parameters was conducted via I-Optimal design. The workability of concrete mixes was reduced with an increase of well-graded BA due to high water absorption effect. The compressive strengths of all mixes reached more than 50% on 28th curing days with maximum strength by BM15 (49.0 MPa). The split tensile strengths showed one quadratic curve combining all mixes with maximum strength reached by BM10 (2.7 MPa). The flexural strength has slow growth exponential pattern with maximum strength by BM20 (6.0 MPA). The thermal conductivity values were steadily increased up to BM15 (2.44 W/mK) and reduced at BM20 (2.15 W/mK). The well-graded BA proportions (5 to 20%) were not showing any significant effect on the thermal properties. The optimised model of compressive strength has the highest accuracy with percentage errors below 5% compared to other parameters. The optimal well-graded BA as sand replacement material was BM10 giving 47 MPa compressive strength, 2.7 MPa split tensile strength, 5.3 MPa flexural strength, and 2.1152 W/mK thermal conductivity. The highest positive correlation coefficients were obtained between compressive strength and thermal conductivity (R2: 0.921). Thus, the well-graded BA improved the strength properties providing a sustainable supply in concrete technology.

	2023	Composite science
Concrete is brittle; hence, it is incredibly likely that concrete buildings may fail in both local and global ways under dynamic and impulsive stresses. An extensive review investigation was carried out to examine reinforced concrete (RC) slab behavior under low-velocity impact loading. Significant past research studies that dealt with experimental and numerical simulations and analytical modeling of the RC slabs under impact loading have been presented in this work. As a result, numerous attempts to define failure behavior and to assess concrete structures’ vulnerability to lateral impact loads have been made in the literature. Based on analytical, numerical, and experimental studies carried out in previous research, this article thoroughly reviewed the current state of the art regarding the responses and failure behaviors of various types of concrete structures and members subjected to low-velocity impact loading. The effects of different structural and load-related factors were examined regarding the impact strength and failure behavior of reinforced concrete slabs reinforced with various types of strengthening procedures and exposed to low-velocity impact loads. The reviews suggested that advanced composite materials, shear reinforcement, and hybrid techniques are promising for effectively strengthening concrete structures

	2023	Results in Engineering
"Reinforced concrete flat solid slabs may experience explosive and impact loads. Reinforced concrete flat solid slabs have been studied under static and dynamic loads. Researchers have widely explored numerous reinforcing strategies to strengthen RC slabs exposed to impact loads, yet gaps remain. Internal anchorage stirrups (W-stirrups shear reinforcement) is still rarely used to strengthen slabs against impact loading. Consequently, this study emphasized the influence of W-stirrups shear reinforcement on the dynamic response and failure modes of RC slabs subjected to impact loads. The first part examined the impact behavior of fully fixed RC flat solid slabs reinforced with W-stirrups shear reinforcement experimentally. Slabs were impacted using portable drop-weight testing equipment. Six 800-x-800-x-90-mm RC slabs were made. Three samples were reinforced with a W-stirrups orthogonally oriented in two directions, whereas three controls were without any type of strengthening. The eccentric vertical displacement of slabs, strain at four points on the W-stirrups, two on main steel, and two on concrete, and acceleration at one point over a slab were measured; also, failure modes were monitored. In the second section, ABAQUS software was used to generate finite element models of slab study samples. Numerical model results matched experimental results. Thus, the suggested finite element model may assess reinforced RC slabs under low-velocity impact loads. Finally, a parametric study was conducted in the third part to address the issue of over-reinforced design in slabs with W-stirrups. The parametric study aimed to determine the optimal steel ratio of flexural and shear reinforcement and its influence on the behavior of RC flat solid slabs reinforced with W-stirrups shear reinforcement."

	2024	Arabian Journal for Science and Engineering
Reinforced concrete slabs can be exposed to explosive and impact loads, prompting extensive research into their behavior under various static and dynamic loading conditions. Researchers have explored numerous techniques to enhance the structural integrity of these slabs when subjected to impact loads, but certain knowledge gaps persist. Particularly, the application of shear reinforcement, such as conventional stirrup shear reinforcement, to strengthen slabs against impact remains relatively uncommon. This study aimed to investigate the impact of conventional stirrup shear reinforcement on the dynamic response and failure modes of reinforced concrete slabs when subjected to low-velocity impact loading. The first phase involved experimental evaluation, focusing on the influence of vertical conventional stirrups as shear reinforcement in two-way, fully fixed RC slabs. Portable drop weight testing equipment was used to subject six (800 × 800 × 90 mm) RC slabs, to impact testing. Three slabs were strengthened with stirrups in two directions orthogonally configuration, while three control slabs received no additional reinforcement. Various parameters, including vertical displacement, strain at multiple points on the stirrups, main steel, and concrete, as well as acceleration at a specific point on the slab, were measured. Additionally, the failure modes were closely monitored. In the second phase, finite element models of the slab study samples were created using ABAQUS software. The numerical model results aligned with the experimental findings, indicating that the proposed finite element model can effectively assess the structural behavior of reinforced concrete slabs subjected to low-velocity impact loads. The third part of the research involved a parametric study to investigate the effects of bar diameter and drop position on the structural response of the slabs. The outcomes of this study highlight the significant positive impact of shear reinforcement, particularly in the form of conventional stirrups, on the load-bearing capacity of reinforced concrete slabs. Slabs with stirrups exhibited noteworthy improvements in strength, stiffness, and ductility compared to control specimens without shear reinforcement. Specifically, the presence of conventional vertical stirrup shear reinforcement increased the slab's capacity by 29.5% under the total impact energy until complete failure.

	2023	PERTANIKA JOURNAL OF SOCIAL SCIENCES AND HUMANITIES
"The use of cement is expected to increase over the years as the infrastructure continues to develop, and the needs to repair or rehabilitate an old and deteriorated building are necessary. However, many investigations have been conducted to establish promising polymer concrete applications in the last few decades. Meanwhile, using concrete in the construction industry has led to environmental issues. It is because relying on cement production in concrete will contribute to about 7% of the world’s carbon dioxide emissions. Therefore, polymer concrete was introduced in this study to minimise the use of cement in the industry. This research investigated the influence of different amounts of polypropylene (PP) fibre content on polymer concrete (PC) properties by determining the compressive strength, flexural strength and indirect tensile strength. Furthermore, the results of PC failure characteristics have been discussed. The polymer concrete specimens in this study have been cast into cylinders and prismatic specimens using PVC pipe and plywood formwork to determine the compressive strength, splitting tensile strength and flexural strength. By reinforcing PP fibre in the polymer concrete with a specific percentage of fibre reinforced, the overall strength of the polymer concrete"

المؤلفات

	2026	IOS Press Ebooks

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