• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.127-135
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• 2006

In this study, steel deck bridges are chosen as analytic model to show the structural behaviors generated by high temperature of pavement and to formulate the simplified approximate analysis of thermal effects. In general, the thermal effect is changed by the material property of pavements and environmental temperature as well as shape, size and boundary conditions of bridge. Specially, this effect is the representative initial stress problem dependent on time. The thermal effect, however, does not depend on time and thermal effect is regarded as initial load in this study. After these thermal loading is modelled as moving loads, influence lines of reactions of shoes are calculated and the successive pavement steps with arbitrary segments are determined to minimize the thermal effect of shoes by influence line.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.715-725
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• 2003

This paper is a part of a research program to develop a new design method for reinforced concrete bridge columns under seismic loading. The objectives of this paper are to investigate the relationship between ductility and confinement steel amount and to propose a design equation for reinforced concrete bridge columns. Computer program NARCC was used for parametric study, which was proved to provide good and conservative analytical result especially for deformation capacity and ductility factor compared with test result. A total of 7,200 reinforced concrete columns confined with spirals or perfect circular hoops were selected by combination of variables such as section diameter, aspect ratio, concrete compressive strength, yielding strength of longitudinal and confinement steel, longitudinal steel ratio, axial load ratio, and confinement steel ratio. Based on the parametric study a new design equation for confinement steel amount considering ductility demand was proposed, which can be used in the new seismic design method, i.e. ductility-based seismic design, for RC bridge columns.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.107-119
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• 1991

This dissertation analyzes the running mechanism of flexible and thin tape above rotating head through the experiment. The scope of study is confined to measure the vertical deformation of running tape under hydrodynamic pressure invoking phenomena of elasto-hydrodynamic lubrication between the protruded bump on a rotating cylinder ad the running tape. Experimental system is devised to measure the vertical deflection of the running tape by opto-electronical displacement gauge, which enables to detect microscopic surface deflection of high frequency. Thorough the tests of small specimens of groove and bump, the accuracy and reliability of this experimental method is confirmed and achieved an accuracy within 5%(2.mu.m) error for the microscopic deflection with high frequency. In experimental works, the effects of bump size on flying characteristics of the tape were evaluated and examined. For the vertical deformation of the running tape. the numerical results and its trend agree qualitatively with the experimental ones.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.145-157
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• 2008

Load transfer efficiency (LTE) reflects the structural performance of doweled and undoweled joints of Jointed Concrete Pavement (JCP). A 3-dimensional (3-D) model of JCP was built using ABAQUS software in this study. Three concrete slabs were placed on bonded sublayers composed of a base and subgrade. Spring elements were used to connect the adjacent slabs at joints. Different spring constants were input to the model to simulate different joint stiffness of the concrete pavement. The LTE of the joint increased with an increase of the spring constant. The effects of material properties and geometric shape on the behavior of JCP were analyzed using different elastic modulus and thickness of the slab and base in the modeling. The results showed the elastic modulus of the subgrade affected the behavior of the slab and LTE more than that of the base and the thickness of the slab and base. The effects of a negative temperature gradient on the behavior of the slab and LTE were more than that of positive and zero temperature gradients. Joints with low stiffness were more sensitive to the temperature gradient of the slab.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.11
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• pp.1099-1104
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• 2012

The study investigates the mechanical deformation of a newly developed screwless omega-wire dynamic system for stabilization of the spine. The omega-wire spring stabilization system was tested under tension, compression, and dynamic compressive fatigue loads. In addition, its bending deformation was compared to that of a spiral-wire spring system using FEA. A model whose hanger inter-center distance is 60 mm showed an ultimate tensile stress of 3981.7 N at a displacement of 3.61 mm and an ultimate compressive load of 535.6 N at a displacement of 2.16 mm. Under fatigue loading of 5 Hz with 10 N/1 N, it did not show any failure over 5 million cycles, and the displacement was restricted to 8-9 mm. In the FEA, the omega-wire spring system showed more flexible bending features than did the spiral-wire spring system.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.147-158
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• 2004

For stiffened plates composed of composite materials, many researchers have used a finite element method which connected isoparametric plate elements and beam elements. However, the finite element method is difficult to reflect local behavior of stiffener because beam elements are transferred stiffness for nodal point of plate elements, especially the application is limited in case of laminated composite structures. In this paper, for analysis of laminated composite stiffened plates, 3D shell elements for stiffener and plate are employed. Reissner-Mindlin's first order shear deformation theory is considered in this study. But when thickness will be thin, isoparamatric plate bending element based on the theory of Reissner-Mindlin is generated by transverse shear locking. To eliminate the shear locking and virtual zero energy mode, the substitute shear strain field is used. A deflection distribution is investigated for simple supported rectangular and skew stiffened laminated composite plates with arbitrary orientation stiffener as not only variation of slenderness and aspect ratio of the plate but also variation of skew angle of skew stiffened plates.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.177-184
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• 2012

An optical defect detection method using ESPI(electronic speckle pattern interferometry) is proposed. ESPI is widely used as a non-contact measurement system which show deformation and phase map in real time. ESPI can be divided as the in-plane, out-of-plane and shearography by operation principle and target object and also divided with bulk type and optic fiber type by the optic configurations. This paper is focused on optic fiber type out-of-plane ESPI, which has the following advantages: (1) low cost; (2) reduction of the unreliable factors generated by separated optic components; (3) simplification of the optic configuration; (4) great reduction of volume; (5) flexibility, to be easily designed into different structures to adapt to inaccessible environments such as pipeline cavity and so on.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.1
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• pp.13-23
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• 2015

The paper experimentally deals with the radial in-plane vibration characteristics of disk-shaped piezoelectric transducers. The radial in-plane motion, which is induced due to Poisson's ratio in the piezoelectric disk polarized in the thickness direction, was measured by using an in-plane laser vibrometer, and the natural frequencies were measured by using an impedance analyzer. The experimental results have been compared with theoretical predictions obtained by simplified theoretical and finite-element analyses. It appears that the fundamental mode of a piezoelectric disk transducer is a radial mode and its radial displacement distribution from the center to the perimeter is not monotonic but shows maximum slightly apart from the perimeter. The theoretically-calculated fundamental frequencies agree well with the finite-element results for small thickness-to-diameter ratio, and they are accurate within 7 % error for the ratio up to 0.4.

• Tunnel and Underground Space
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• v.16 no.1 s.60
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• pp.11-25
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• 2006

The world's largest nucleon decay experiment facility is constructed at a depth of approximately 1,000 meters, in the Kamio Mine, Japan. The excavated cavern is consisted of a cylinder of 42.4 m high and a semi elliptical dome of 15.2 m high, with a bottom diameter of 40 m. The total excavation volume is approximately $69,000\;m^3$. Because of the character as a large cavern excavation in deep underground, there is many unknown factors in rock mechanics. Based on the results of rock test and numerical analysis, the monitoring of rock mass behavior accompanying progress of construction was performed by various instruments installed in the rock mass surrounding the cavern. The monitoring data was used in the study of measures for cavern stability.

• 대한공업교육학회지
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• v.35 no.2
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• pp.224-237
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• 2010

When the underwater structure sails high speed, noise and vibration propagate to the sensor in the nose of the dome. In this paper, to avoid this kind of noise and vibration CRP(Carbon Reinforced Plastic) material and SNORE ring(Self-NOise REduction Ring) are attached at the curved structure and simulates its isolation characteristics using commercial software. Vibration displacement and stress are calculated at the planar sensor array. The material of the curved structure is aluminum and maximum outer diameter is 53Omm, 215mm in length, 270mm in planar diameter, respectively. Based on the simulation results, reduction ratio of the received normal stress at the sensor is above 95% at the frequency of 12kHz and 15kHz. At the mid point of the planar sensor the normal stress is higher than 20mm and 40mm apart. This results can be used to increase the sensitivity of the acoustic sensor as a basic data.