• Fashion & Textile Research Journal
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• v.24 no.1
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• pp.156-163
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• 2022

Loss of leg muscle and muscle weakness, which are caused by aging, affect muscle function and sense of balance. As a way of preventing seniors from falling, we developed the idea of wearing functional supporters based on graduated compression technique and in the form of a taping supporter. Their impact on power, sense of balance, overcoming fatigue, and subjective wearing sensation was investigated. The following results were obtained. After wearing functional compression supporters, body temperature increased from 24.5 ± 0.5℃ to 26.3 ± 0.6℃. Calf size, which assesses the level of edema, decreased from 26.1 ± 1.8cm to 25.7 ± 1.8cm. The result of dynamic balance test, which helps estimate the fall prevention effect, increased from 6.4 ± 0.9sec to 7.1 ± 0.6sec. Lactate level, which indicates the level of fatigue, decreased from 8.1 ± 0.6mmol/L to 7.3 ± 0.8mmol/L. Standing long jump record, which assesses power, increased from 110.1 ± 3.1cm to 112.0 ± 2.8cm. Standing on one leg with eyes closed, which assesses sense of balance, increased from 4.2 ± 1.1sec to 6.5 ± 0.8sec. Ankle angle, which assesses joint stability, increased from 75.3 ± 4.0° to 80.1 ± 1.7°. In metabolism and physical performance testing, which assesses keep, the score increased from 26.3 ± 1.7 to 28.8 ± 1.2. Muscle supporting score, which assesses joint stability, increased from 7.3 ± 0.6 to 7.8 ± 0.4. In the category of body type, which assesses wearing sensation and body shaping function, the score increased from 5.7 ± 1.4 to 6.4 ± 1.2

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.2
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• pp.105-114
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• 2016

When impact load is applied to a plate structure, a common phenomenon that occurs in structures is plastic deformation accompanied by a large strain and eventually it will experience a fracture accordingly. In this study, for the rational design against accidental limit state, the plastic material constants of steel plate which is formed by line heating and by cold bending procedure have been defined through the numerical simulation for the high speed tension test. The usefulness of the material constants included in Cowper-Symonds model and Johnson-Cook model with the assumption that strain rate can be neglected when strain rate is less than the intermediate speed is verified through comparing the present numerical results with those in references. This paper ends with describing the future study.

• Structural Engineering and Mechanics
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• v.74 no.6
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• pp.789-807
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• 2020

Multiple earthquakes that occur during short seismic intervals affect the inelastic behavior of the structures. Sequential ground motions against the single earthquake event cause the building structure to face loss in stiffness and its strength. Although, numerous research studies had been conducted in this research area but still significant limitations exist such as: 1) use of traditional design procedure which usually considers single seismic excitation; 2) selecting a seismic excitation data based on earthquake events occurred at another place and time. Therefore, it is important to study the effects of successive ground motions on the framed structures. The objective of this study is to overcome the aforementioned limitations through testing a two storey RC building structural model scaled down to 1/10 ratio through a similitude relation. The scaled model is examined using a shaking table. Thereafter, the experimental model results are validated with simulated results using ETABS software. The test framed specimen is subjected to sequential five artificial and four real-time earthquake motions. Dynamic response history analysis has been conducted to investigate the i) observed response and crack pattern; ii) maximum displacement; iii) residual displacement; iv) Interstorey drift ratio and damage limitation. The results of the study conclude that the low-rise building model has ability to resist successive artificial ground motion from its strength. Sequential artificial ground motions cause the framed structure to displace each storey twice in correlation with vary first artificial seismic vibration. The displacement parameters showed that real-time successive ground motions have a limited impact on the low-rise reinforced concrete model. The finding shows that traditional seismic design EC8 requires to reconsider the traditional design procedure.

• Steel and Composite Structures
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• v.7 no.6
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• pp.457-468
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• 2007

Analytical and experimental investigation on dynamic properties of extra lightweight concrete sandwich beams reinforced with various lay ups of carbon reinforced epoxy polymer composites (CFRP) are discussed. The lightweight concrete used in the core of the sandwich beams was made up of extra lightweight aggregate, Lica. The density of concrete was half of that of the ordinary concrete and its compressive strength was about $100Kg/cm^2$. Two extra lightweight unreinforced (control) beams and six extra lightweight sandwich beams with various lay ups of CFRP were clamped in one end and tested under an impact load. The dimension of the beams without considering any reinforcement was 20 cm ${\times}$ 10 cm ${\times}$ 1.4 m. These were selected to ensure that the effect of shear during the bending test would be minimized. Three other beams, made up of ordinary concrete reinforced with steel bars, were tested in the same conditions. For measuring the damping capacity of sandwich beams three methods, Logarithmic Decrement Analysis (LDA), Hilbert Transform Analysis (HTA) and Moving Block Analysis (MBA) were applied. The first two methods are in time domain and the last one is in frequency domain. A comparison between the damping capacity of the beams obtained from all three methods, shows that the damping capacity of the extra lightweight concrete decreases by adding the composite reinforced layers to the upper and lower sides of the beams, and becomes most similar to the damping of the ordinary beams. Also the results show that the stiffness of the extra lightweight concrete beams increases by adding the composite reinforced layer to their both sides and become similar to the ordinary beams.

• Journal of Navigation and Port Research
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• v.37 no.5
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• pp.527-533
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• 2013

This paper presents damage detection and estimation of stiffness parameter on a concrete scale model and a real structure of concrete pontoon using dynamic properties such as mode shapes and natural frequencies. In case of damage detection, dynamic impact test on a concrete scale model is accomplished to extract mode shapes and the practicality is verified by utilizing a damage detection technique. And the stiffness parameter of a real structure of concrete pontoon was estimated via system identification technique using the natural frequencies of the structure. The results indicate that the damaged elements of the scale model are found exactly using damage detection technique and the effective stiffness property of the real structure of concrete pontoon can be estimated by system identification technique.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.10 s.241
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• pp.1092-1100
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• 2005

In the present study, characteristics of steady state laminar flows of a straight duct connected to a 180$^{o}$ curved duct were examined in the entrance region through experimental and numerical analyses. For the analysis, the governing equations of laminar flows in the Cartesian coordinate system were applied. Flow characteristics such as velocity profiles and secondary flows were investigated numerically and experimentally in a square cross-sectional straight duct by the PIV system and a CFD code(STAR CD). For the PIV measurement, smoke particles produced from mosquito coils. The experimental data were obtained at 9 points dividing the test sections by 400 3m. Experimental and numerical results can be summarized as follows. 1) Reynolds number, Re was increased, dimensionless velocity profiles at the outer wall were increased due to the effect of the centrifugal force and secondary flows. 2) The intensity of a secondary flow became stronger at the inner wall rather than the outer wall regardless of Reynolds number. Especially, fluid dynamic phenomenon called conner impact were observed at dimensionless axial position, x/D$_{h}$=50.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.1044-1048
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• 2002

The experimental modal testing has been carried out for the stator of a generator to confirm the vibrational mode shapes and the corresponding natural frequencies. The model of the stator for the vibration analysis was developed and a series of vibration analyses was carried out. And the properties of the solid element were updated to reduce the differences of the natural frequencies between the measured and the analysed. In the vibration anlyses, the axial, radial and circumferential properties of the solid element were separately varied to take into account the orthotropic effect of the laminated structure and to match the primary modes of the stator core which were extracted from the modal testing. After several attempts to match the measured natural frequencies and model shapes, the properties of the stator model were determined. Comparison of the vibration analyses results based on the determined properties showed fairly good coincidence with the measured data.

• Earthquakes and Structures
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• v.9 no.4
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• pp.911-936
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• 2015

This work evaluates the performance of a number of seismic assessment procedures when applied to a case study reinforced concrete (RC) wall building. The performance of each procedure is evaluated through its ability to accurately predict deformation demands, specifically, roof displacement, inter-storey drift ratio and wall curvatures are considered as the key engineering demand parameters. The different procedures include Direct Displacement-Based Assessment, nonlinear static analysis and nonlinear dynamic analysis. For the latter two approaches both lumped and distributed plasticity modelling are examined. To thoroughly test the different approaches the case study building is considered in different configurations to include the effects of unequal length walls and plan asymmetry. Recommendations are made as to which methods are suited to different scenarios, in particular focusing on the balance that needs to be made between accurate prediction of engineering demand parameters and the time and expertise required to undertake the different procedures. All methods are shown to have certain merits, but at the same time a number of the procedures are shown to have areas requiring further development. This work also highlights a number of key aspects related to the seismic response of RC wall buildings that may significantly impact the results of an assessment. These include the influence of higher-mode effects and variations in spectral shape with ductility demands.

• Corrosion Science and Technology
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• v.16 no.5
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• pp.235-240
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• 2017

Regional cathodic protection has significant impact on pipeline integrity management. After risk analyses of a newly built gas distribution station constructed in an area with large dwelling density, risk score was high because of potential threat caused by galvanic corrosion. Except reinforced steel in concrete, there are four kinds of metal buried under earth: carbon steel, galvanized flat steel, zinc rod and graphite module. To protect buried pipeline from external corrosion, design and construction of regional cathodic protection was proposed. Current density was measured with potential using potential dynamic test and boundary element method (BEM) was used to calculate current requirement and optimize best anode placement during design. From our calculation on the potential, optimized conditions for this area were that an applied current was 3A and anode was placed at 40 meters deep from the soil surface. It results in potential range between $-1.128V_{CSE}$ and $-0.863V_{CSE}$, meeting the $-0.85V_{CSE}$ criterion and the $-1.2V_{CSE}$ criterion that no potential was more negative than $-1.2V_{CSE}$ to cause hydrogen evolution at defects in coating of the pipeline.

• Structural Engineering and Mechanics
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• v.65 no.4
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• pp.381-388
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• 2018

Dynamic behaviour of beam carrying masses has attracted attention of many researchers and engineers. Many studies on the analytical solution of beam with concentric tip mass have been published. However, there are limited works on vibration analysis of beam with an eccentric three dimensional object. In this case, bending and torsional deformations of beam are coupled due to the boundary conditions. Analytical solution of equations of motion of the system is complicated and lengthy. Therefore, in this study, Differential Transform Method (DTM) is applied to solve the relevant equations. First, the Timoshenko beam with 3D tip attachment whose centre of gravity is not coincident with beam end point is considered. The beam is assumed to undergo bending in two orthogonal planes and torsional deformation about beam axis. Using Hamilton's principle the equations of motion of the system along with the possible boundary conditions are derived. Later DTM is applied to obtain natural frequencies and mode shapes of the system. According to the relevant literature DTM has not been applied to such a system so far. Moreover, the problem is modelled by Ansys, the well-known finite element method, and impact test is applied to extract experimental modal data. Comparing DTM results with finite element and experimental results it is concluded that the proposed approach produces accurate results.