• Journal of Navigation and Port Research
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• v.36 no.3
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• pp.163-168
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• 2012

Recently, people's desire for the waterfront space has been increasing, and more people want to spend their leisure time close to the water. This paper proposes a damage detection technique using the static strain for the floating structure. An existing damage index, in which the modal strain energy was utilized to identify possible location of damage, is expanded to apply the static strain. The new damage index is expressed in terms of the static strains of undamaged and damaged structures. After calculating damage index, the possible damage locations in the structure are determined by the pattern recognition technique. The accuracy and feasibility of the proposed method is demonstrated by using experimental strain data from a scale model of floating structure.

• Tunnel and Underground Space
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• v.11 no.4
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• pp.328-338
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• 2001

Horizontal tunnel face reinforcement using Fiber Glass Tube(FGT) or steel pipe and pipe roofing techniques are frequently used when the stability of newly excavated tunnel is not guaranteed. However, the mechanical behavior of tunnels using these techniques has not been fully understood so far. Therefore, engineering rule of thumb is commonly applied during designing procedure, and it is difficult to adopt these techniques rationally. In this study, the application of a simplified numerical analysis method based on composite mechanics is verified. The mean field theory and the strain energy theory are used to obtain the equivalence elastic moduli of reinforced soil and rock. Furthermore, a parametric study on the deformational behavior of tunnel face is performed for various patterns of prereinforcement.

• Composites Research
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• v.22 no.4
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• pp.27-32
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• 2009

Characterisation of the stress-strain relationship as well as crashworthiness of cellular polymer was investigated under constant impact energy with different velocities, considering inertia and strain rate effects simultaneously during the impact testing. Quasi-static and impact tests were carried out for two different density (64 $kg/m^3$, 89 $kg/m^3$) cellular polymer specimens. Also, the equations, coupled with the Sherwood-Frost model and the Impulse-Momentum theory, were employed to build the constitutive relation of the cellular polymer. The nominal stress-strain curves obtained from the constitutive relation were compared with results from impact tests and showed to be in good agreement.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.511-520
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• 2004

The fracture energy evaluated from the previous experimental results can be simulated by using the modified singular fracture process zone (S-FPZ) model. The fracture model has two fracture properties of strain energy release rate for crack extension and crack close stress versus crack width relationship $f_{ccs}$ ( w ) for fracture process zone (FPZ) development. The $f_{ccs}$( w ) relationship is not sensitive to specimen geometry and crack velocity. The fracture energy rate in the FPZ increases linearly with crack extension until the FPZ is fully developed. The fracture criterion of the strain energy release rate depends on specimen geometry and crack velocity as a function of crack extension. The variation of strain energy release rate with crack extension can explain theoretically the micro-cracking, micro-crack localization and full development of the FPZ in concrete.

• Magazine of the Korea Concrete Institute
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• v.1 no.1
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• pp.105-114
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• 1989

휨을 받는 철근콘크리트 부재 단면의 연화현상은 구조물의 파괴하중 해석시 중요한 인자로 작용한다. 일반적인 탄-소성 이론에 근거한 소성한계해석법을 사용할 경우 철골 구조물에는 적합하지만 철근콘크리트 구조물에는 최대하중 이후의 연화현상으로 인하여 이 이론은 부적합하게 된다. 따라서 본 논문의 주목적은 변위제어방법을 사용하여 철근콘크리트 구조물이 파괴될 때까지의 완전한 거동을 이끌어 내는 것이다. 프로그램을 사용한 계산결과를 보다 빠르고 경제적으로 이끌어 내기 위하여 단면의 성질인 모멘트-곡률, 축력-축\ulcorner향 변형률, 그리고 전단력 변형률 곡선 등을 여러개의 직선적으로 단순화한 모델식을 사용하여 해석한다. 또한 연화현상을 고려한 유한요소의 해석결과는 사용된 요소의 크기에 따라 결과가 매우 다르게 나타나기 때문에 이를 방지하기 위하여 파괴에너지 개념을 도입하여 모멘트-곡률 곡선을 보정하여 구조계산에 적용시킨다. 이와 같이 단면을 층으로 나누어 해석하지 않고 직접 단면의 성질을 나타내는 곡선들을 적용한 본 프로그램으로 보와 골조를 해석한 결과는 실제적인 실험결과와 비교하였을 경우 거의 일치하게 나타난다.

• Composites Research
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• v.32 no.1
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• pp.6-12
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• 2019

This paper describes the characteristics for mode I interlaminar and intralaminar fractures of cross-ply carbon/epoxy composite laminates. We obtained mode I interlaminar fracture toughness and mode I intralaminar fracture toughness based on energy release rate and Finite Element Analysis (FEA). For this purpose, the Double-Cantilever Beam (DCB) test and FEA were performed for cross-ply DCB specimens. Also, the behavior of load-displacement curve at the interlaminar and intralaminar crack was analyzed. The results show that mode I intralaminar fracture toughness was lower than mode I interlaminar fracture toughness in the cross-ply DCB specimen.

• Elastomers and Composites
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• v.42 no.3
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• pp.168-176
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• 2007

When the rubber vulcanizates reinforced with carbon black or silica are subjected to cyclic loading from its virgin state, the stress required on reloading is less than that on the initial loading. This stress softening phenomenon is referred to as the Mullins effect. The strain energy function of rubber vulcanizates was investigated using theory of pseudo-elasticity incorporated damage parameter that Ogden and Roxburgh have proposed to describe the damage-induced stress softening effect in rubber-like solids. The quasi-static cyclic loading test was performed using the NR-SBR vulcanizates reinforced with carbon black, and then the effect of a damage parameter to stress-strain curve in reloading and subsequent reloading paths was studied. The strain energy function of the rubber vulcanizates with a different filler content was also evaluated.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.30-35
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• 1997

물성치가 상이한 계에서 접합면을 포함한 전 영역내의 연속 응력장 개선방안을 제안하였다. 재료의 물성치가 100배 차이가 나는 직선보 예제에 대해 변위형 유한요소해에서는 접착면 상ㆍ하측에서 응력들이 불연속이며 상당한 차이를 보이고 있는데 반하여 본 연구에서의 응력장은 연속이며 접합면의 절점응력들이 이론해에 근접하고 있다 또한 본 연구에서의 연속 응력장으로 계산한 변형률 에너지는 수회 이내의 반복계산에서 이론해에 수렴하고 있다.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.685-692
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• 2007

When the shear force governs the response of an RC element, as in the case of a low-rise shear wall, the effect of shear on the element's response is thought to be responsible for the 'pinching effect' in the hysteretic loops. However, it was recently shown that this undesirable pinching effect can be eliminated in the hysteretic load-deformation curves of a shear-dominant element if the steel grid orientation is properly aligned in the direction of the applied principal stresses. In this paper, the presence and absence of the pinching mechanism in the hysteretic loops of the shear stress-strain curves of RC elements was explained rationally using a compatibility aided truss model. The analytical results indicate that the pinching effect of the RC elements is strongly related to the direction of the steel arrangement. The area of the energy dissertation does not increase proportionally to the difference between the direction of the principal compressive stress and the direction of the steel arrangement.

• Journal of Korean Society of Steel Construction
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• v.16 no.3 s.70
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• pp.295-303
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• 2004

In this paper, an improved four-node Reissner-Mindlin plate-bending element with enhanced assumed strain field is presented for the analysis of isotropic and laminated composite plates. To avoid the shear locking and spurious zero energy modes, the transverse shear behavior is improved by the addition of a new enhanced shear strain based on the incompatible displacement mode approach and bubble function. The "standard" enhanced strain fields (Andelfinger and Ramm, 1993) are also employed to improve the in-plane behaviors of the plate elements. The four-node quadrilateral element derived using the first-order shear deformation theory is designated as "14EASP". Several applications are investigated to assess the features and the performances of the proposed element. The results are compared with other finite element solutions and analytical solutions. Numerical examples show that the element is stable, invariant, passes the patch test, and yields good results especially in highly distorted regimes.