• Wind and Structures
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• 제35권1호
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• pp.55-66
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• 2022

Tall buildings are often subjected to steady and unsteady forces due to external wind flows. Measurement and mitigation of these forces becomes critical to structural design in engineering applications. Over the last few decades, many approaches such as modification of the external geometry of structures have been investigated to mitigate wind-induced load. One such proven geometric modification involved the rounding of sharp corners. In this work, we systematically analyze the impact of rounded corner radii on the reducing the flow-induced loading on a square cylinder. We perform 3-Dimensional (3D) simulations for high Reynolds number flows (Re=1 × 105) which are more likely to be encountered in practical applications. An Improved Delayed Detached Eddy Simulation (IDDES) method capable of capturing flow accurately at large Reynolds numbers is employed in this study. The IDDES formulation uses a k-ω Shear Stress Transport (SST) model for near-wall modelling that prevents mesh-induced separation of the boundary layer. The effects of these corner modifications are analyzed in terms of the resulting variations in the mean and fluctuating components of the aerodynamic forces compared to a square cylinder with no geometric changes. Plots of the angular distribution of the mean and fluctuating coefficient of pressure along the square cylinder's surface illustrate the effects of corner modifications on the different parts of the cylinder. The windward corner's separation angle was observed to decrease with an increase in radius, resulting in a narrower and longer recirculation region. Furthermore, with an increase in radius, a reduction in the fluctuating lift, mean drag, and fluctuating drag coefficients has been observed.

• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.235-244
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• 2021

본 연구에서는 한계상태설계법에 기반한 교량 평가법을 개발하기 위하여, 공용 중인 교량의 실측실험을 반영하여 적용성을 분석하였다. 예제 PSC Beam 실 교량의 부재 실험 결과로부터 부재의 시험강도를 구하였으며, 재료 시험값으로부터 추정된 통계특성을 적용하여 산정된 저항강도와 시험강도를 비교하였다. 부재의 시험강도와 재료의 변동성을 고려한 저항강도는 동등한 수준으로 계산되어 실측실험의 적합성이 검증되었다. 차량재하시험으로부터 응답보정계수와 동적충격계수를 계산하였으며, 실측실험 결과를 반영한 내하율을 적용하여 현행 교량 평가법과 한계상태설계법 기반으로 산정된 내하율을 비교하였다. 재료 시험값의 통계특성으로부터 추정된 부재 저항강도의 통계특성을 적용하여 실 교량의 신뢰도지수를 계산하였다. 설계기준 개발에 적용한 저항강도 통계특성으로 구한 신뢰도지수보다 실측실험의 통계특성을 적용하는 경우 더 큰 값의 신뢰도지수를 얻었다.

• Steel and Composite Structures
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• 제41권5호
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• pp.697-711
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• 2021

In this work, a simple quasi 3-D parabolic shear deformation theory is developed to examine the bending response of antisymmetric cross-ply laminated composite plates under different types of mechanical loading. The main feature of this theory is that, in addition to including the transverse shear deformation and thickness stretching effects, it has only five-unknown variables in the displacement field modeling like Mindlin's theory (FSDT), yet satisfies the zero shear stress conditions on the top and bottom surfaces of the plate without requiring a shear correction factor. The static version of principle of virtual work was employed to derive the governing equations, while the bending problem for simply supported antisymmetric cross-ply laminated plates was solved by a Navier-type closed-form solution procedure. The adequacy of the proposed model is handled by considering the impact of side-to-thickness ratio on bending response of plate through several illustrative examples. Comparison of the obtained numerical results with the other shear deformation theories leads to the conclusion that the present model is more accurate and efficient in predicting the displacements and stresses of laminated composite plates.

• Advances in concrete construction
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• 제14권5호
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• pp.317-330
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• 2022

This paper investigated computationally and experimentally the interaction here between a notch as well as a micropore under uniaxial compression. Brazilian tensile strength, uniaxial tensile strength, as well as biaxial tensile strength are used to calibrate PFC2d at first. Then, uniaxial compression test was conducted which they included internal notch and micro pore. Experimental and numerical building of 9 models including notch and micro pore were conducted. Model dimensions of models are 10 cm × 10 cm × 5 cm. Joint length was 2 cm. Joints angles were 30°, 45° and 60°. The position of micro pore for all joint angles was 2cm upper than top of the joint, 2 cm upper than middle of joint and 2 cm upper than the joint lower tip, discreetly. The numerical model's dimensions were 5.4 cm × 10.8 cm. The fractures were 2 cm in length and had angularities of 30, 45, and 60 degrees. The pore had a diameter of 1 cm and was located at the top of the notch, 2 cm above the top, 2 cm above the middle, and 2 cm above the bottom tip of the joint. The uniaxial compression strength of the model material was 10 MPa. The local damping ratio was 0.7. At 0.016 mm per second, it loaded. The results show that failure pattern affects uniaxial compressive strength whereas notch orientation and pore condition impact failure pattern. From the notch tips, a two-wing fracture spreads almost parallel to the usual load until it unites with the sample edge. Additionally, two wing fractures start at the hole. Both of these cracks join the sample edge and one of them joins the notch. The number of wing cracks increased as the joint angle rose. There aren't many AE effects in the early phases of loading, but they quickly build up until the applied stress reaches its maximum. Each stress decrease was also followed by several AE effects. By raising the joint angularities from 30° to 60°, uniaxial strength was reduced. The failure strengths in both the numerical simulation and the actual test are quite similar.

• 대한족부족관절학회지
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• 제27권1호
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• pp.17-23
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• 2023

Purpose: Toe-in gait is defined as a style of walking in which the foot turns inward. It may be caused by an increase in femoral bone anteversion, tibia torsion, and metatarsus adductus. There are some conservative treatment approaches used to correct this condition. This review aimed to determine the effects of the toe-in gait on joint loading, kinematics, and kinetic parameters while walking. Moreover, it sought to determine the efficiency of various conservative treatments used to correct the condition. Materials and Methods: A literature search was conducted in the following databases: PubMed, Institute for Scientific Information (ISI), Web of Science database, EBSCO, and Embase, using the following keywords in toe, toe-in, toeing, in-toe, pigeon toe, and conservative treatment published between 1950 and 2021. The quality of the studies was evaluated using the Down and Black tool. Results: A total of 13 papers on the impact of toe-in gait on joint contact force, kinematics, kinetic parameters, and conservative approaches to management were found. The quality of the studies varied between a score of 11 and 22. The toe-in gait influences the joint contact forces and kinematics of the joints, especially the hip and pelvis. The effects of conservative treatment on the toe-in gait appear to be controversial. Conclusion: As the toe-in gait influences the joint contact force, it may increase the incidence of degenerative joint diseases. Therefore, treatment is recommended. However, there is no strong evidence on the efficacy of conservative treatments, and there are no recommendations for the use of these treatments in subjects with toe-in gait.

• Geomechanics and Engineering
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• 제29권5호
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• pp.567-582
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• 2022

In the present study, a series of physical experiments and numerical simulations were conducted to investigate the effects of mode I and mixed-mode I/II cracks on the fracture modes and stability of roadway tunnel models. The experiments and simulations incorporated different inclination angle flaws under both static and dynamic loads. The quasi-static and dynamic testing were conducted by using an electro-hydraulic servo control device and drop weight impact system (DWIS), and the failure process was simulated by using rock failure process analysis (RFPA) and AUTODYN software. The stress intensity factor was also calculated to evaluate the stability of the flawed roadway tunnel models by using ABAQUS software. According to comparisons between the test and numerical results, it is observed that for flawed roadways with a single radical crack and inclination angle of 45°, the static and dynamic stability are the lowest relative to other angles of fractured rock masses. For mixed-mode I/II cracks in flawed roadway tunnel models under dynamic loading, a wing crack is produced and the pre-existing cracks increase the stress concentration factor in the right part of the specimen, but this factor will not be larger than the maximum principal stress region in the roadway tunnel models. Additionally, damage to the sidewalls will be involved in the flawed roadway tunnel models under static loads.

• 한국지반공학회논문집
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• 제39권1호
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• pp.27-38
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• 2023

본 연구에서는 3D 프린팅 기술을 활용하여 타입말뚝 선단의 모양에 따른 관입성 분석을 현장 축소모형시험을 통해 관찰하고, 대변형 수치해석을 통해 타입 중 말뚝 선단에 집중되는 최대응력의 변화를 확인하였다. 3D 프린터를 통하여 다양한 직경, 각도 그리고 모양의 말뚝 선단 모형을 제작하였고, 이를 현장 축소모형시험에 활용하였다. 이를 통해, 말뚝 선단 조건에 따른 말뚝의 침하량의 변화를 관찰하였다. 더 나아가, 대변형 수치해석 기법을 적용하여 다양한 말뚝 선단 조건에 따른 타입 중 말뚝 선단부의 최대응력의 변화와 최대응력 작용 위치 또한 확인하였다. 현장 축소모형시험과 대변형 수치해석의 결과 분석을 토대로 말뚝 선단 조건의 변화를 통해 타입말뚝의 관입성을 향상 시킬 수 있으며 선단부에 집중되는 최대응력 또한 완화 시켜 말뚝 시공 중 말뚝 손상을 방지할 수 있을 것으로 결론지을 수 있었다.

• Structural Engineering and Mechanics
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• 제84권3호
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• pp.345-360
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• 2022

In this paper, the impact on seismic performance of an economical effective technique for retrofitting reinforced concrete (RC) columns using high-strength steel strips under high axial compression ratios was presented. The experimental program included a series of cyclic loading tests on one nonretrofitted control specimen and three retrofitted specimens. The effects of the axial compression ratio and spacing of the steel strips on the cyclic behavior of the specimens were studied. Based on the test results, the failure modes, hysteretic characteristics, strength and stiffness degradation, displacement ductility, and energy dissipation capacity of the specimens were analyzed in-depth. The analysis showed that the transverse confinement provided by the high-strength steel strips could effectively delay and restrain diagonal crack development and improve the failure mode, which was flexural-shear failure controlled by flexural failure with better ductility. The specimens retrofitted using high-strength steel strips showed more satisfactory seismic performance than the control specimen. The seismic performance and deformation capacity of the retrofitted RC columns increased with decreasing axial compression ratio and steel strip spacing. Based on the test results, a hysteretic model for RC columns that considers the transverse confinement of high-strength steel strips was then established. The hysteretic model showed good agreement with the experimental results, which verified the effectiveness of the proposed hysteretic model. Therefore, the aforementioned analysis can be used for the design of retrofitted RC columns.

• Journal of Animal Science and Technology
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• 제65권5호
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• pp.939-950
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• 2023

This study was conducted to assess the impact of growing condition variables on alfalfa (Medicago sativa L.) productivity. A total of 197 alfalfa yield results were acquired from the alfalfa field trials conducted by the South Korean National Agricultural Cooperative Federation or Rural Development Administration between 1983 and 2008. The corresponding climate and soil data were collected from the database of the Korean Meteorological Administration. Twenty-three growing condition variables were developed as explaining variables for alfalfa forage biomass production. Among them, twelve variables were chosen based on the significance of the partial-correlation coefficients or potential agricultural values. The selected partial correlation coefficients between the variables and alfalfa forage biomass ranged from -0.021 to 0.696. The influence of the selected twelve variables on yearly alfalfa production was summarized into three dominant factors through factor analysis. Along with the accumulated temperature variables, the loading scores of the daily mean temperature higher than 25℃ were over 0.88 in factor 1. The sunshine duration at temperature between 0℃-25℃ was 0.939 in factor 2. Precipitation days were 0.82, which was the greatest in factor 3. Stepwise regression applied with the three dominant factors resulted in the coefficients of factors 1, 2, and 3 for 0.633, 0.485, and 0.115, respectively, and the R-square of the model was 0.602. The environmental conditions limiting alfalfa growth, such as daily temperature higher than 25℃ or daily mean temperature affected annual alfalfa production most substantially among the growing condition variables. Therefore, future cultivar selection should consider the capability of alfalfa to be tolerant to extreme summer weather along with biomass production potential.

• Smart Structures and Systems
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• 제32권3호
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• pp.153-166
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• 2023

Health monitoring of civil infrastructures, in particular, old bridges that are still in service, has become more than necessary, given the risk that a possible degradation or failure of these infrastructures can induce on the safety of users in addition to the resulting commercial and economic impact. Bridge integrity assessment has attracted significant research efforts over the past forty years with the aim of developing new damage identification methods applicable to real structures. The bridge of Ouled Mimoun (Tlemcen, Algeria) is one of the oldest railway structure in the country. It was built in 1889. This bridge, which is too low with respect to the level of the road, has suffered multiple shocks from various machines that caused considerable damage to its central part. The present work aims to analyze the stability of this bridge by identifying damages and evaluating the damage rate in different parts of the structure on the basis of a finite element model. The applied method is based on an inverse analysis of the normal stress responses that were calculated from the corresponding recorded strains, during the passage of a real train, by means of a set of strain gauges placed on certain elements of the bridge. The results obtained from the inverse analysis made it possible to successfully locate areas that were really damaged and to estimate the damage rate. These results were also used to detect an excessive rigidity in certain elements due to the presence of plates, which were neglected in the numerical reference model. In the case of the continuous bridge monitoring, this developed method will be a very powerful tool as a smart health monitoring system, allowing engineers to take in time decisions in the event of bridge damage.