• Steel and Composite Structures
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• v.36 no.4
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• pp.481-492
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• 2020

To study the rail mapped deformation caused by the pier settlement of simply - supported bridges with China Railway Track System III (CRTS III) slab ballastless track (SBT) system under the mode of non-longitudinal connection ballastless track slab, this study derived an analytical solution to the mapped relationships between pier settlement and rail deformation based on the interlayer interaction mechanism of rail-pier and principle of stationary potential energy. The analytical calculation results were compared with the numerical results obtained by ANSYS finite element calculation, thus verifying the accuracy of analytical method. A parameter analysis was conducted on the key factors in rail mapped deformation such as pier settlement, fastener stiffness, and self-compacting concrete (SCC) stiffness of filling layer. The results indicate that rail deformation is approximately proportional to pier settlement. The smaller the fastener stiffness, the smoother the rail deformation curve and the longer the rail deformation area is. With the increase in the stiffness of SCC filling layer, the maximum positive deformation of rail gradually decreases, and the maximum negative deformation gradually increases. The deformation of rail caused by the pier settlement of common-span bridge structures will generate low-frequency excitation on high-speed trains.

• Korean Journal of Applied Biomechanics
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• v.21 no.2
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• pp.207-213
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• 2011

The purpose of this study was to investigate changes in elastic properties of tendon structure of human ankle dorsiflexor following eccentric exercise. Six male subjects(age: $27.3{\pm}2.0$ years, height: $180.3{\pm}1.4$ cm, weight: $82.6{\pm}5.3$ kg) and three female subjects(age: $26.7{\pm}2.9$ years, height: $170.0{\pm}4.2$ cm, weight: $66.6{\pm}1.4$ kg) performed a single bout eccentric exercise consisting of 120 repetitions of maximum eccentric contractions. Prior to and following the eccentric exercise, isometric ankle dorsiflexion strength along with longitudinal ultrasound image of the tibialis anterior(TA) were collected. Muscle strength decreased about 30% after eccentric exercise. From the muscle strength vs. aponeurosis elongation curve, we obtained an index of stiffness. Stiffness of deep aponeurosis of the TA was assessed and found to be decreased from $87.4{\pm}33.56$ N/mm to $73.1{\pm}23.52$ N/mm. The results of this study suggest that decrease in stiffness of the TA aponeurosis following eccentric exercise might have significant implications to functions of the muscle-tendon complex and the involved joint motion and provide better understanding of eccentric exercise in the fields of training and rehabilitation.

• Structural Engineering and Mechanics
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• v.53 no.4
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• pp.791-818
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• 2015

RC buildings constitute the prevailing type of construction in earthquake-prone region like Kathmandu Valley. Most of these building constructions were based on conventional methods. In this context, the present paper studied the seismic behaviour of existing RC buildings in Kathmandu Valley. For this, four representative building structures with different design and construction, namely a building: (a) representing the non-engineered construction (RC1 and RC2) and (b) engineered construction (RC3 and RC4) has been selected for analysis. The dynamic properties of the case study building models are analyzed and the corresponding interaction with seismic action is studied by means of non-linear analyses. The structural response measures such as capacity curve, inter-storey drift and the effect of geometric non-linearities are evaluated for the two orthogonal directions. The effect of plan and vertical irregularity on the performance of the structures was studied by comparing the results of two engineered buildings. This was achieved through non-linear dynamic analysis with a synthetic earthquake subjected to X, Y and $45^{\circ}$ loading directions. The nature of the capacity curve represents the strong impact of the P-delta effect, leading to a reduction of the global lateral stiffness and reducing the strength of the structure. The non-engineered structures experience inter-storey drift demands higher than the engineered building models. Moreover, these buildings have very low lateral resistant, lesser the stiffness and limited ductility. Finally, a seismic safety assessment is performed based on the proposed drift limits. Result indicates that most of the existing buildings in Nepal exhibit inadequate seismic performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.657-663
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• 2018

In this study, shape optimization was performed to improve the vibration isolation capability of an anti-vibration rubber assembly, which is used in the field option cabin of agricultural tractors. A uniaxial tension test and biaxial tension test were performed to characterize the hyper-elastic material properties of rubber, and the data were used to calibrate the material model used in the finite element analyses. A field test was performed to quantify the input excitation from the tractor and the output response at the cabin frame. To account for the nonlinear behavior of rubber, static analyses were performed and the load-displacement curve of rubber was derived. The stiffness of the rubber was calculated from this curve and input to the harmonic analyses of the cabin. The results were verified using the test data. Taguchi's parameter design method was used to find the optimal shape of the anti-vibration rubber assembly, which indicated a shape with reduced stiffness. The vibration of the cabin frame was reduced by the optimization by as much as 35% compared to the initial design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.337-343
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• 2017

As a shop practice, a strength estimation method for die cast parts is suggested, in which various defects such as pores can be allowed. The equivalent porosity is evaluated by combining the stiffness data from a simple elastic test at the part level during the shop practice and the theoretical stiffness data, which are defect free. A porosity equation is derived from Eshelby's inclusion theory. Then, using the Mori-Tanaka method, the porosity value is used to draw a stress-strain curve for the porous material. In this paper, the Hollomon equation is used to capture the strain hardening effect. This stress-strain curve can be used to estimate the strength of a die cast part with porous defects. An elastoplastic theoretical solution is derived for the three-point bending of a die cast beam by using the plastic hinge method as a reference solution for a part with porous defects.

• Journal of Oral Medicine and Pain
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• v.30 no.3
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• pp.337-344
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• 2005

A tactile sensor employs a piezoelectric element to detect contact frequency shifts and thereby measure the stiffness or softness of material such as tissue, which allows the sensor to be used in many fields of research for urology, cardiology, gynecology, sports medicine and caner detection and especially for cosmetics and skin care. In this study, reliability of the tactile sensor system was investigated with its manual application to the muscles susceptible to temporomandibular disorders. Stiffness and elasticity of anterior temporalis, masseter and trapezius muscles were calibrated bilaterally from 5 healthy men with an average of 24.5$\pm$0.94 years. The tactile sensor used in this study had a computer-controlled and motor-driven sensor unit which automatically pressed down on the skin surface over the muscles being measured and retracted, thereby providing the hysteresis curve. The slope of the tangent of the hysteresis curve (${\Delta}f/{\Delta}x$) is defined as stiffness of the muscle being measured and the distance between the two parts of the curve as its elasticity. To determine inter-examiner reliability, all the measurements were performed by the two examiners A and B, respectively and the same examination were repeated with an interval of 2 days for intra-examiner reliability. The results from this study demonstrated high reliability in measuring stiffness and elasticity of anterior temporalis, masseter and upper trapezius muscles using a tactile sensor system. It is suggested that the tactile sensor system can be a highly reproducible and effective instrument for quantitative evaluation of the muscle in head and neck region.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.135-145
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• 2005

Geotechnical design routinely requires that in-situ strength, stiffness of the ground be determined. In the working stress conditions, the strain level in a ground experienced by existing structures and during construction is less than about 0.1%~1%. In order to analyze the deformational behavior accurately, the in-situ testing technique which provides the reliable deformational characteristics at small strains, needs to be developed. Cone pressuremeter tests were performed on the western off-shore region of korea, and analyzed using cavity expansion theory and curve fitting technique to obtain the shear modulus at small strain level of $10^{-1}%$. The value of $E_u/S_u$ ratio for the marine clay shows about 589 at the small strain. However the value of $E_u/S_u$ estimated by lab tests are much smaller values ranged from 81 to 91. It is indicated that the curve fitting technique from CPM tests results can be used to obtain the shear modulus at small strain.

• Structural Engineering and Mechanics
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• v.16 no.5
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• pp.533-556
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• 2003

The flutter and buckling analysis of a beam structure subjected to a static follower force is completely studied in the paper. The beam is fixed in the transverse direction and constrained by a rotational spring at one end, and by a translational spring and a rotational spring at the other end. The co-existence of flutter and buckling in this beam due to the presence of the follower force is an interesting and important phenomenon. The results from this theoretical analysis will be useful for the stability design of structures in engineering applications, such as the potential of flutter control of aircrafts by smart materials. The transition-curve surface for differentiating the two distinct instability regions of the beam is first obtained with respect to the variations of the stiffness of the springs at the two ends. Second, the capacity of the follower force is derived for flutter and buckling of the beam as a function of the stiffness of the springs by observing the variation of the first two frequencies obtained from dynamic analysis of the beam. The research in the paper may be used as a benchmark for the flutter and buckling analysis of beams.

• Textile Coloration and Finishing
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• v.28 no.2
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• pp.109-117
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• 2016

Synthetic fabrics, such as nylon and polyester, were dyed with persimmon juice by using a padding mangle repeatedly. The mechanical properties of these synthetic fabrics were analyzed using the Kawabata evaluation system. The following findings were obtained from this investigation. As the number of repetitions of padding dyeing increased, the tensile energy per unit area and the tensile resilience of synthetic fabric remained almost unchanged, whereas the linearity of the load-extension curve of the synthetic fabrics increased. As the number of padding repetitions increased, the synthetic fabrics dyed with persimmon juice exhibited increases in thickness and weight. As the number of repetitions of padding treatment with persimmon juice increased, the values of stiffness, anti-drape stiffness, fullness, and softness also increased, whereas the flexibility with soft feeling, crispness, and scrooping sensation significantly decreased. The amount of coated persimmon juice on the surface of the fabrics increased after three repetitions of padding treatment with persimmon juice. Nylon and polyester fabrics were dyed evenly with persimmon juice treated using a padding mangle.

• Journal of Mechanical Science and Technology
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• v.19 no.3
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• pp.792-801
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• 2005

This paper discusses a dc motor equipped electric power steering (EPS) system and demonstrates its advantages over a typical hydraulic power steering (HPS) system. The tire-road interaction torque at the steering tires is calculated using the 2 d.o.f. bicycle model, in other words by using a single-track model, which was verified with the J-turn test of a real vehicle. Because the detail parameters of a steering system are not easily acquired, a simple system is modeled here. In previous EPS systems, the assisting torque for the measured driving torque is developed as a boost curve similar to that of the HPS system. To improve steering stiffness and return-ability of the steering system, a third-order polynomial as a torque map is introduced and modified within the preferred driving torques researched by Bertollini. Using the torque map modification sufficiently improves the EPS system.