• Journal of Mechanical Science and Technology
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• 제17권1호
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• pp.85-96
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• 2003

In the present investigation, the nonlinear dynamic buckling of a curved plate subjected to sinusoidal loading is examined. By the theoretical analyses, a highly nonlinear snap-through motion of a clamped-free-clamped-free plate and its effect on the overall vibration response are investigated. The problem is reduced to that of a single degree of freedom system with the Rayleigh-Ritz procedure. The resulting nonlinear governing equation is solved using Runge-Kutta (RK-4) numerical integration method. The snap-through boundaries, which vary with different damping coefficient and linear circular frequency of the flat plate are studied and given in terms of force and displacement. The relationships between static and dynamic responses at the start of a snap-through motion are also predicted. The analysis brings out various characteristic features of the phenomenon, i.e. 1) small oscillation about the buckled position-softening spring type motion, 2) chaotic motion of intermittent snap-through, and 3) large oscillation of continuous snap-through motion crossing the two buckled positions-hardening spring type. The responses of buckled plate were found to be greatly affected by the snap-through motion. Therefore, better understanding of the snap-through motion is needed to predict the full dynamic response of a curved plate.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.22-27
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• 1999

고급복합재료(advanced composite material)는 여러 가지 훌륭한 장점에도 불구하고 건설기술자에게는 그 이론이 너무 복잡하여 건설구조에 대한 응용이 지연되고 있다. [$\alpha/\beta/\beta/\gamma/\alpha/\alpha/\beta$]r, $\alpha$=-$\beta$, $\gamma$=0$^{\circ}$ 또는 90$^{\circ}$ 와 같은 몇 가지 배향각을 갖은 적층판은, r이 증가함에 따라, $B_{i,j}$강성이 0으로 접근한다(1995). 건설구조물은 그 치수가 커서 r이 증가해도 지간 대 두께비가 충분히 커서, 횡방향 변형율(${\varepsilon}_{xz}$,${\varepsilon}_{yz}$)의 영향이 무시될 수 있다. 이 경우 판의 지배방정식은 간단한 특별직교이방성판의 식으로 변화된다. 김덕현은 토목구조물에 흔히 적용될 수 있는 이러한 배향각을 가진 적층판의 지배방정식을 취급이 간단한 특별직교 이방성 판의 경우로 변경시킨 다음 해석을 더 간단히 진행할 수 있도록 기술자들이 유사 등방성 상수(quasi-isotropic constant)를 사용하여 낮익은 등방성판의 방정식을 사용하여 답을 구한 다음 그가 개발한 "수정계수(correction factor)"를 사용하여 "정확한"해를 구하는 방법을 발표한바 있다(1991).는 방법을 발표한바 있다(1991).

• 한국정밀공학회지
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• 제11권1호
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• pp.89-96
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• 1994

This study is to develop a new composite material, a mixture of epoxy resin and granite aggergates which is called Expoxy-Granite, to overcome the inherent disadvantages of conventional materials commonly used as a bed structure material of long-term dimensional/ thermal stability. Under the various manufacturing conditions which could be formulated through experimental investigation, we have constructed 6 kinds of Epoxy-Granite structure models having one fifth the size of the ultra-precision machine tool bed structure. They are compared with cast iron and pure granite models through the dynamic test and the thermal deformation test. Both in the steel ball dropping test and in the forced vibration test, three types of epoxy-granite models made in this study have shown much better dynamic characteristics than the cast iron model and almost the same characteristics as compared with the pure granite model. In the thermal deformation test the above composite materials have also represented lower thermal displacements in the vertical direction of each model as compared with other specimens. It is therefore seen that the epoxy-granite complsite material can be applied to the construction of high-precision machine tool bed, instead of cast iron or pure granite.

• Advances in concrete construction
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• 제9권2호
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• pp.161-171
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• 2020

In this paper, an experimental study was conducted on the compressive behavior of steel tube confined concrete (STCC) and concrete-filled steel tube (CFST) columns with active and passive confinement. To create active confinement in the STCC and CFST specimens, an innovative method was used in this study, in which by applying pressure on the fresh concrete, the steel tube was laterally pretensioned and the concrete core was compressed simultaneously. Of the benefits of this technique are improving the composite column behavior, without the use of additives and without the need for vibration, and achieving high prestressing levels. To achieve lower and higher prestressing levels, short and long term pressures were applied to the specimens, respectively. Nineteen STCC and CFST specimens in three groups of passive, short-term active, and long-term active confinement were subjected to axial compression, and their mechanical properties including the compressive strength, modulus of elasticity and axial strain were evaluated. The results showed that the proposed method of prestressing the STCC columns led to a significant increase in the compressive strength (about 60%), initial modulus of elasticity (about 130%) as well as a significant reduction in the axial strain (about 45%). In the CFST columns, the prestressing led to a considerable increase in the compressive strength, a small effect on the initial and secant modulus of elasticity and an increase in the axial strain (about 55%). Moreover, increased prestressing levels negligibly affected the compressive strength of STCCs and CFSTs but slightly increased the elastic modulus of STCCs and significantly decreased that of CFSTs.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 추계학술대회 논문집
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• pp.299-303
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• 2001

In this paper, we introduce the Partial Half-Through Type Plate Girder Bridge proposed by Hyundai Development Co. and KRTC Consortium in Turn-Key Based design last year, and this type of bridge may be adapted to the railway bridge under similar conditions. This bridge across the North Han River was to be concerned its find view and the protection of water source. For its location is inside the dam, it required the long span and the clearance for the flood also. Its new composite section was able to diminish the deflection and vibration. Its shop-fabrication could control its quality easily, and might to be launched. This structural type have satisfied its functions, construction situations, and overall safeties, so this is the field-oriented type. However the composition and connections of the proposed members are different to the recent forms, and difficult to be applied to present specifications. Therefore it requires a certification on the application for more safety by not only analytical verifications but also experimental studies. Nevertheless, this type of bridge may have some more applications from now on.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.386-394
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• 2007

Due to the transportability problems, long rail shall be from base rail unit, which is normally 100m for regular rail and 300m for high speed rail. After these rail units are transported from the fabricator to the site, the field weld would be performed.axial stresses in the long rail is mainly from the temperature differences at various locations the long rail. Also the gaps between each welds cause secondary axial stresses in the rail. In addition to these, re-welds the fractured rails, rail buckling, irregular rail vibration, rail twist also result innonuniform axial stresses in the rail. To obtain the rail buckling stability, the rail stresses shall be released due to the resetting of CWR. Traditionally two resetting of CWR methods have been applied, the one is rail heater and the other is rail tenser. these methods, the latter has been recommended because it has less limitation in the rail length and it is easier to minimized the force differences. But even in this method, the calculation is cumbersome and is not easy to find out the rail stress distribution itself.refined methodsxial stress resetting in the long rail is studied and this study be easily applied in the real construction. From this approach, more rational rail maintenance system can be expected.

• 소음진동
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• 제9권1호
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• pp.184-188
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• 1999

Noise regulation of heavy construction machinery is getting stricter： 3 dB per every 4 year in European community. To meet this requirement many engineers have adopted the enclosing structures with thick absorbing materials and small opening, This increases internal temperature of the enclosure which have engine systems such as electric equipment that are vulnerable to heat, and engine block and muffler that can be regarded as heat sources. So noise control engineers have to consider a coupling problem: combining heat balance and noise reduction. This paper describes this approach by introducing simple heat transfer theory and SEA. The enclosing system of the loader whose enclosing structure consists of two rooms is investigated to show the validity of this method. The results represent that the simple heat transfer theory can be useful to estimate cooling performance when it is linked together by the back pressure theory in duct system. and the radiated noise can also be estimated by the SEA. Therefore a designer can use these approaches to define the opening ratio of an enclosure and the mass flow rate of air considering radiating noise.

• 소음진동
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• 제9권3호
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• pp.535-543
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• 1999

The seismic qualification of the structures has been great concern in our engineering society with an effort to reduce the severe damages from an earthquake. However, on the contrary to the importance of the seismic qualification, the whole procedures are used to rely on the advanced countries who require various expenses for the qualification, which leads to the heavy loss of the foreign currency. In this study, the nuclear air conditioning system produced by LG Cable are adopted for the seismic qualification based on the guideline of NUREG, IEEE and ASME code. In order to confirm the validity of the present study, the results from the Ellis & Watts are compared with the present results and, also, the seismic qualification procedures and results mentioned herein are approved by KOPEC, which is a naitonal surveillance institute for the construction of nuclear power plant. From these results, the author confirmed the validity of the present seismic qualification procedures and results, which might be usefully applied to the other kind of seismic qualification of equipments.

• KCI Concrete Journal
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• 제12권2호
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• pp.55-72
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• 2000

This paper proposes a mechanical model to describe the load-deformation responses of the reinforced concrete plate members under service load state. An Analytical method is introduced on the basis of the rotating crack model which considers equilibrium, compatibility conditions, load-strain relationship of cracked member, and constitutive law for materials. The tension stiffening effect in reinforced concrete structures is taken into account by the average tensile stress-strain relationship from the load-strain relationship for the cracked member and the constitutive law for material. The strain compatibility is used to find out the crack direction because the crack direction is an unknown variable in the equilibrium and compatibility conditions. The proposed theory is verified by the numerous experimental data such as the crack direction, moment-steel strain relationship, moment-crack width relationship. The present paper can provide some basis for the provision of the definition of serviceability for plate structures of which reinforcements are deviated from the principal stresses, because the present code defines the serviceability by the deflection, crack control, vibration and fatigue basically for the skeletal members. The proposed theory is applicable to predict the service load state behavior of a variety of reinforced concrete plate structures such as skew slab bridges, the deck of skew girder bridges.

• 한국초전도ㆍ저온공학회논문지
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• 제6권4호
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• pp.46-50
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• 2004

The Experimental results of the in-line type inertance tube pulse tube cryocooler for cooling superconductor RF filter are presented in this paper. The pulse tube refrigerator, which has no moving parts at its cold section, is attractive in obtaining higher reliability, simpler construction, and lower vibration than any other small refrigerators. The purpose of this study is to analyze the characteristics of in-line type inertance tube pulse tube refrigerator (IPTR), and to get main factor to improve the performance of the in-line type IPTR. Firstly, design parameters of the in-line IPTR are discussed by ARCOPTR program, and then to find optimal conditions of in-line type IPTR, cool down characteristics according to the variations of the charging pressure, inertance tube volume, regenerator volume and pulse tube volume are measured by the experiment. The lowest temperature of the cold end was about 50 K. Cooling capacity was the highest in the charging pressure of 32 atm. and 5W at 72K. On the other hand, COP of the in-line type IPTR was the highest in the charging pressure of 21 atm. and 0.018 at 77K.