• 한국도로학회논문집
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• 제8권2호
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• pp.31-35
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• 2006

Cement stabilisation is a common method for stabilising recycled road base material and provides a longer pavement life. With cement effect, the increment of stiffness in the stabilised layer would provide better load transfer to the pavement foundation. The recycling method provides an environmentally option as the existing road base materials will not be removed. This paper presents a case study of a trial section along the North-South Expressway in West Malaysia, where the Falling Weight Deflectometer (FWD) was implemented to evaluate the compressive strength and in-situ stiffness of the cement stabilised road base material. The improvement in stiffness of the cement stabilised base layer was monitored, and samples were tested during the trial. FWD was found to be useful for the structural assessment of the cement-stabilised base layer prior to placement of asphalt layers. Results from the FWD were applied to verify the assumed design parameters for the pavement. Using the FWD, an empirical correlation between the deflection and the stiffness modulus of the pavement foundation is proposed.

• Nuclear Engineering and Technology
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• 제27권5호
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• pp.760-766
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• 1995

Young's Modulus와 단지 기하학적 테이타를 이용하여 흘드다운스프링의 탄성강성도를 해석하는 방법을 제시하였다. 제시된 이 방법은 엔지니어링 빔이론과 카스티릴아노 이론을 이용하여 판형흘드다운스프링의 탄성강성도 해석에 적용하였다. 이러한 방법의 효율성과 신뢰성을 보여주기 위하여 제안된 방법으로 부터의 탄성강성도를 여러가지 형태의 홀드다운스프링의 시험결과와 비교하였다. 이러한 결과비교에 의해 제안된 방법이 판형홀드다운스프링의 탄성강성도를 구하는데 있어서 효과적임을 입증하였다.

• 한국안전학회지
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• 제29권3호
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• pp.64-71
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• 2014

The generalized tangential stiffness matrix of semi-rigid frame element with shear deformations based on Haringx's shear theory is newly derived and compared with the previous study based on Engesser's shear theory. Also, linearized elastic and geometric stiffness matrices are newly presented from the exact tangential stiffness matrix. In oder to obtain the inelastic system buckling load of shear flexible semi-rigid frame structure, the Ef method by tangential modulus theory is adopted and the FE analysis programs are developed. Finally, the shear and semi-rigid effects of system bucking are investigated by two numerical examples.

• Structural Engineering and Mechanics
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• 제70권4호
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• pp.421-429
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• 2019

This paper presents an analytical model for the estimation of initial lateral stiffness of steel moment resisting frames with masonry infills. However, rather than focusing on the single bay-single storey substructure, the developed model attempts to estimate the global stiffness of multi-storey and multi-bay frames, using an assembly of equivalent springs and taking into account the shape of the lateral loading pattern. The contribution from each infilled frame panel is included as an individual spring, whose properties are determined on the basis of established diagonal strut macro-modeling approaches from the literature. The proposed model is evaluated parametrically against numerical results from frame analyses, with varying number of frame stories, infill openings, masonry thickness and modulus of elasticity. The performance of the model is evaluated and found quite satisfactory.

• Geomechanics and Engineering
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• 제25권4호
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• pp.341-345
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• 2021

1D sand compression response to ko-loading experiences volume contraction from low to high effective stress regimes. Previous study suggested compressibility model with physically correct asymptotic void ratios at low and high stress levels and examined only for both remolded clays and natural clays. This study extends the validity of Enhanced Terzaghi model for different sand types complied from 1D compression data. The model involved with four parameters can adequately fit 1D sand compression data for a wide stress range. The low stress obtained from fitting parameters helps to identify the initial fabric conditions. In addition, strong correlation between compressibility and the void ratio at low stress facilitates determination of self-consistent fitting parameters. The computed tangent constrained modulus can capture monotonic stiffening effect induced by an increase in effective stress. The magnitude of tangent stiffness during large strain test should not be associated with small strain stiffness values. The use of a single continuous function to capture 1D stress-strain sand response to ko-loading can improve numerical efficiency and systematically quantify the yield stress instead of ad hoc methods.

• 한국구조물진단유지관리공학회 논문집
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• 제7권1호
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• pp.191-198
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• 2003

The pavement stiffness is scarcely used in structural analysis to design the superstructure of bridge. It is reasonable not to consider it in the case of asphalt concrete pavement over concrete deck because the pavement stiffness compared with the concrete deck plate can be ignored. However, sometimes, the pavement materials have a similar amount of elastic modulus to concrete and are applied to the orthotropic steel deck plate which has relatively less stiffness compared with the concrete deck plate. In this paper, the steel plate deck of a real bridge project was analyzed by considering the pavement stiffness by linear elastic FEM. It was assumed that a perfect bond between the steel plate deck and the pavement exited. The results indicated that the structural behavior of the orthotropic steel deck plate can be estimated enough to affect the evaluation result of structural capacity in some cases. Therefore, the investigations by experimental tests and more advanced numerical model are indispensible in figuring the design formula for considering the effects of pavement stiffness in the structural analysis of an orthotropic bridge.

• Structural Engineering and Mechanics
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• 제77권1호
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• pp.137-149
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• 2021

In engineering design, the axial equivalent elastic modulus of laminated FRP pipe was mostly calculated by the average elastic modulus method or the classical laminated plate theory method, which are based on relatively simplified assumptions, and may be not accurate enough sometimes. A new analytical calculation method for the axial equivalent elastic modulus of laminated FRP pipe was established based on three-dimensional stress state. By comparing the results calculated by this method with those by the above two traditional analytical methods and the finite element method, it is found that this method for the axial equivalent elastic modulus fits well not only for thin-walled pipes with orthotropic layers, but also for thick-walled pipes with arbitrary layers. Besides, the influence of the layer stacking on the axial equivalent elastic modulus was studied with this method. It is found that a proper content of circumferential layer is beneficial for improving the axial equivalent elastic modulus of the laminated FRP pipe with oblique layers, and then can reduce its material quantity under the premise that its axial stiffness remains unchanged. Finally, the meso-mechanical mechanism of this effect was analyzed. The improving effect of circumferential layer on the axial equivalent elastic modulus of the laminated FRP pipe with oblique layers is mainly because that, the circumferential fibers can restrain the rigid body rotations of the oblique fibers, which tend to cause the significant deformations of the pipe wall units and the relatively low axial equivalent elastic modulus of the pipe.

• 한국음향학회지
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• 제37권5호
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• pp.338-342
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• 2018

상하층 간 공동주택의 바닥충격음 문제를 해결하기 위해 국토교통부에서는 바닥충격음 레벨에 영향을 미치는 완충재에 대한 물성 기준도 함께 고시하고 있다. 완충재에 대한 물성 기준중 가열전후 동탄성계수, 손실계수는 특히 바닥충격음과 가장 연관되어 있다. 따라서 본 연구에서는 기준에서 명시하고 있는 $70^{\circ}C$의 온도 조건을 기준으로 $10^{\circ}C$씩 증가시키고 $10^{\circ}C$씩 저감시켜 온도변화에 따른 동탄성계수 및 손실계수에 대하여 변화율을 검토하였다. 총 8가지 종류의 시료에 대하여 동탄성계수 및 손실계수 측정 방법은 펄스 가진법으로 수행되었으며 결과 산출방법은 감쇠 진동 파형을 이용한 시계열 해석법으로 산출하였다.

• 마이크로전자및패키징학회지
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• 제26권4호
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• pp.39-46
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• 2019

Polydimethylsiloxane (PDMS)를 베이스 기판으로 사용하고 이보다 강성도가 높은 flexible printed circuit board (FPCB)를 island 기판으로 사용하여 island-bridge 구조의 soft PDMS/hard PDMS/FPCB 신축 패키지를 형성하고, 이의 유효 탄성계수와 변형거동을 분석하였다. 각기 탄성계수가 0.28 MPa, 1.74 MPa 및 1.85 GPa인 soft PDMS, hard PDMS, FPCB를 사용하여 형성한 soft PDMS/hard PDMS/FPCB 신축 패키지의 유효 탄성계수는 0.58 MPa로 분석되었다. Soft PDMS/hard PDMS/FPCB 신축 패키지에서 soft PDMS의 변형률이 0.3이 되도록 인장시 hard PDMS와 FPCB의 변형률은 각기 0.1과 0.003이었다.

• 한국재료학회지
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• 제13권9호
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• pp.606-612
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• 2003

Surface and mechanical properties of thin films with submicron thickness was characterized by nanoindentation with Berkovich and Vickers tips, and scanning probe microscopy. Nanoindention was made in a depth range of 15 to 200 nm from the surface by applying tiny force in a range from 150 to $9,000 \mu$N. Stiffness, contact area, hardness, and elastic modulus were determined from the force-displacement curve obtained. Reliability was first tested by using fused quartz, a standard sample. Elastic modulus and hardness values of fused quartz measured were the same as those reported in the literature within two percent of error. Mechanical properties of ITO thin film were characterized in a depth range of 15∼200nm. As indentation depth increased, elastic modulus and hardness decreased by substrate effect. Ion beam deposited DLC thin films were indented in a depth range of 40∼50 nm. The results showed that the DLC thin film using benzene and bias voltage 0∼-50 V has elastic modulus and hardness value of 132 and 18 GPa respectively. Pure DLC thin films showed roughnesses lower than 0.25 nm, but silicon-added DLC thin films showed much higher roughness values, and the wavy surface morphology.