• Advances in concrete construction
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• v.10 no.1
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• pp.61-69
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• 2020

This paper looks into how the shape of headed bars may influence the durability of reinforced concrete structures. Nowadays the only heads used in site works are cylindrical in shape. An alternative shape of head is studied in this piece of work. The new head reduces the concentration of stresses and so the appearance of cracks. In this work durability is studied based on both, first cracking and failure mode. An experimental campaign of 12 specimens and finite element modelling are described. The specimens were subjected to an accelerated corrosion process using an electrical current supply. Direct current was impressed on the specimens until breaking. Test results and the results obtained from numerical models are presented. Results are presented in term of comparison between the two shapes of heads studied. It was shown that the shape of the head has a significant influence on durability of reinforced concrete structures with headed reinforcing bars.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.157-164
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• 2006

This paper presents the durability characteristics of commercially available CFRP rebars under various environmental conditions. Two types of GFRP rebars were tested by using an accelerated aging method. A total of 264 rebar specimens were conditioned up to 132 days in the moisture, chloride. alkaline, and freeze-thaw environmental conditions. The durability characteristics of conditioned rebars were obtained by comparing the tensile strength, horizontal shear strength, and elastic modulus between the unconditioned and conditioned GFRP rebars. The test results indicated that the mechanical properties of GFRP were significantly reduced after conditioning. Long-term degradation of GFRP rebars was also estimated using the results of a short-term durability test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.127-133
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• 2002

The general requirements to achieve the structural integrity of the airframe are described in the military specification, MIL-STD-1530A. One of these requirements is the durability and damage tolerance of the airframe, which should be shown through the analysis and test based on the related specifications. This paper introduces the full scale durability test to evaluate the structural safety and durability of the basic trainer, KT-1. The test was performed according to the procedure in the military specification. The flight by flight load spectrum was developed by KT-1 fatigue load criteria and used for the durability test. The durability test had been performed for 4 service lives and was completed successfully. Therefore, it was shown that KT-1 airframe satisfied the durability requirements.

• International Journal of Highway Engineering
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• v.18 no.1
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• pp.63-72
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• 2016

PURPOSES : The use of roller-compacted concrete pavement (RCCP) is an environmentally friendly method of construction that utilizes the aggregate interlock effect by means of a hydration reaction and roller compacting, demonstrating a superb structural performance with a relatively small unit water content and unit cement content. However, even if an excellent structural performance was secured through a previous study, the verification research on the environmental load and long-term durability was conducted under unsatisfactory conditions. In order to secure longterm durability, the construction of an appropriate internal air-void structure is required. In this study, a method of improving the long-term durability of RCCP will be suggested by analyzing the internal air-void structure and relevant durability of roller-compacted concrete. METHODS : The method of improving the long-term durability involves measurements of the air content, air voids, and air-spacing factor in RCCP that experiences a change in terms of the kind of air-entraining agent and chemical admixture proportions. This test should be conducted on the basis of test criteria such as ASTM C 457, 672, and KS F 2456. RESULTS : Freezing, thawing, and scaling resistance tests of roller compacted concrete without a chemical admixture showed that it was weak. However, as a result of conducting air entraining (AE) with an AE agent, a large amount of air was distributed with a range of 2~3%, and an air void spacing factor ranging from 200 to $300{\mu}m$ (close to $250{\mu}m$) coming from PCA was secured. Accordingly, the freezing and thawing resistance was improved, with a relative dynamic elastic modulus of more than 80%, and the scaling resistance was improved under the appropriate AE agent content rate. CONCLUSIONS : The long-term durability of RCCP has a direct relationship with the air-void spacing factor, and it can be secured only by ensuring the air void spacing factor through air entraining with the inclusion of an AE agent.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.126-134
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• 2014

This study investigates the structural strength analysis due to rib thickness of lower arm. At structural analysis, model 1 has the most deformation by comparing three models. As most equivalent stress is shown at the part connected with wheel knuckle, the strength becomes weaker in cases of three models. At fatigue analysis, model 1 becomes most unstabilized among three models. Model 3 has most fatigue life and the next model is model 2. The range of maximum harmonic response frequencies becomes 140 to 175Hz in cases of three models. Because the critical frequency at model 3 becomes highest among three models but the stress exceeds yield stress, model 3 becomes most unstabilized at vibration durability. As models 1 and 2 has less than yield stress, these models become stabilized. Model 2 becomes most favorable by comparing three models at structural, fatigue and vibration analyses. This study result can be effectively utilized with the design of lower arm by investigating prevention against damage and its strength durability.

• Journal of Korean Society for Quality Management
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• v.45 no.3
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• pp.365-377
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• 2017

Purpose: In the A rotorcraft, the division of a long yaw control rod was studied to improve the heat treatment capability. The purpose of this study was to analyze whether division of yaw control rod affects quality reliability in the A rotorcraft and analyze whether it secured flight safety. Methods: The structural static test and the vibration durability test on the split shape of yaw control rod were carried out in order to examine and verify the existing structural analysis results. Results: Structural static test results showed that there were no cracks and vibration durability test results showed that there was no damage or breakage on the split yaw control rod. Conclusion: This study showed that the quality reliability was confirmed and thus the flight safety of the A rotorcraft was secured. And it is expected that the split technique of the yaw control rod will contribute to the development of the rotorcraft industry in the future.

• Computers and Concrete
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• v.33 no.4
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• pp.385-398
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• 2024

As concrete dominates the construction industry, alternatives to traditionally used steel reinforcement are being sought. This study explored the suitability of carbon fiber-reinforced polymer (CFRP) as a substitute within rigid frames, focusing on its impact on section ductility and overall structural durability against seismic events. However, current design guidelines address quasi-static loads, leaving a gap for dynamic or extreme circumstances. Our approach included multiscale simulations, parametric study, and energy dissipation analyses, drawing upon a unique adaptation of modified compression field theory. In our efforts to optimize macro and microparameters to improve yield strength, manage brittleness, and govern failure modes, we also recognized the potential of CFRP's high corrosion resistance. This characteristic of CFRP could significantly reduce the frequency of required repairs, thereby contributing to enhanced durability of the structures. The research reveals that CFRP's durability and seismic resistance are attributed to plastic joints within compressed fibers. Notably, CFRP can impart ductility to structural designs, effectively balancing its inherent brittleness, particularly when integrated with quasi-brittle materials. This research challenges the notion that designing bendable components with carbon fiber reinforcement is impractical. It shows that creating ductile bending components with CFRP in concrete is feasible despite the material's brittleness. This funding overturns conventional assumptions and opens new avenues for using CFRP in structural applications where ductility and resilience are crucial.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.22-32
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• 2014

Durability is one of the most important and attractive subjects in concrete research field because not only durability of concrete is reduced by various degradation factors but also its reduction adversely influences the structural performance and service life of concrete structure. For this reason, a considerable amount of papers associated with concrete durability have been published and those researches were mainly focused on the changes of intrinsic properties of concrete due to chemicophysical degradations. However, the relationship between durability of concrete and structural behavior of concrete member has not been well established yet. In this study, calcium leaching degradation, a cause of concrete strength reduction, was dealt with. The experiments of compressive and flexural behavior of degraded concrete member were performed to evaluate the characteristics of structural behavior according to degradation level. Finally, the results from the experiments were compared with those obtained from nonlinear FEM analysis. The results from this study clearly showed that leaching degradation leads to decrease in compressive strength and compressive behavior evolves from brittle to ductile failure pattern during the degradation process. Load capacity and flexible rigidity of the degraded RC member decreased when the degradation level increased, in compressive zone. Additionally, it was found that the values from nonlinear FEM analysis, CDP model in ABAQUS, coincided well with the experimental results.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.191-196
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• 2020

In this study, the durability was analyzed as the models with three shapes depending on the length of the landing gear. Overall, the upper part of the landing gear produced a greater amount of deformation, but the equivalent stress was shown to be high in the upper part just above the lower part. Model 3 shows that the maximum equivalent stress is more than 4 times and the maximum total deformation is more than 24 times compared to model 2. Model 3 showed that the damage could occur beyond the yield stress at the lower end. Model 2 with the upper part longer than the lower part showed the lowest equivalent stress and total deformation among the three models. Therefore, from a structural standpoint, it was shown that model 2 was the most durable at landing and model 3 was the most degraded in terms of durability. The design and analysis results of this study can be effectively applied at grasping the structural durability of landing gear. By applying the structural durability analysis of landing gear, this paper is seen as the convergence study that conforms to aesthetic design.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.83-83
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• 2009

The automotive chassis components are structural assemblies that support the engine, suspension, and steering components of the vehicle. For the development of AHSS components, the durability analysis is important. In this paper, the low cycle fatigue property of AHSS was evaluated for the geometry complex and local plasticity in the base material. The GMAW optimization was implemented for the weld soundness using the moving least square method. And the weld S-N curves of AHSS were evaluated to access durability analysis for the weld region. For the verification, the durability analysis of the couple torsion beam axle (CTBA) was performed and compared to the rig test result. The durability analysis using the low cycle fatigue property and the evaluated weld S-N curve of AHSS met the good agreement with the test result.