• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.61-71
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• 2007

Navier's and Finite element solutions based on the first-order shear deformation theory are presented for the analysis of through-thickness functionally graded plates and shells. The functionally graded materials are considered: a sigmoid function is utilized for the mechanical properties through the thickness of the isotropic structure which varies smoothly through the plate and shell thickness. The formulation of a nonlinear 9-node Element-based Lagrangian shell element is presented for the geometrically nonlinear analysis. Natural-coordinate-based strains are used in present shell element. Numerical results of the linear and nonlinear analysis are presented to show the effect of the different top/bottom elastic modulus, loading conditions, aspect ratios and side-to-thickness ratios on the mechanical behaviors. Besides, the result according to the variation of the power-law index of isotropic functionally graded structures is investigated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.293-296
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• 2010

일반 교량에 주로 사용되는 콘크리트 바닥판 시공을 위해서는 동바리, 거푸집 등을 설치하고 철근 배근 후 콘크리트를 타설하는 방법이 사용되어왔다. 그러나 기존 콘크리트 바닥판 시공은 계절 및 기후의 영향을 많이 받는다. 또한 시공과정에서 많은 인력이 요구되고 시공 안전성 확보를 위한 노력이 필요한 실정이다. 이러한 문제점을 극복하기 위하여 최근에 프리캐스트 바닥판을 이용한 교량 시공이 늘어나고 있는 추세이다. 프리캐스트 바닥판은 공장에서 선제작한 후 현장에서 조립하여 시공한다. 따라서 프리캐스트 바닥판 시공은 계절 및 기후의 영향을 최소화 하여 공기를 단축할 수 있고, 공장제작에 따른 양호한 품질도 보장된다. 또한 인력이 적게 요구되면서 시공 안전성도 확보할 수 있다. 그러나 이러한 기존의 프리캐스트 바닥판은 패널의 폭이 좁고 외측 캔틸레버부의 시공 시 별도의 지보공이 필요한 단점을 갖고 있었다. 이러한 단점을 보완하기 위해 장폭 외측 프리캐스트 바닥판이 제안되었다. 장폭 외측 프리캐스트 바닥판은 패널의 폭을 늘려서 장폭의 바닥판을 만들고, 가설구조물을 이용하여 지보공 없이 시공이 가능하게 고안되었다. 본 연구에서는 장폭 외측 프리캐스트 패널 캠버 조정에 사용 될 가설구조의 현장적용을 위하여, 실험 후 유한요소해석을 수행하여 비교 및 검증하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1289-1298
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• 1994

The new p-version crack model is proposed to estimate the stress intensity factors of the thick cracked plate under flexure. The proposed model is based on high order theory and $C^{\circ}$-plate element including shear deformation. The displacements fields are defined by integrals of Legendre polynomials which can be classified into three groups such as basic mode, side mode and internal mode. The computer implementation allows arbitrary variations of p-level Up to a maximum value of 10. The stress intensity factors are computed by virtual crack extention approach. The effects of ratios of thickness to crack length(h/a), crack length to width(a/W) and boundary conditions are investigated. Very good agreement with the existing solution in the literature are shown for the uncracked plate as well as the cracked plate.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.197-208
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• 2000

Choi et al./sup 1)/ presented the total Lagrangian formulation based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors and taking into account the second order rotation terms in the incremental displacement field. Assumed strain concept is adopted in order to overcome the shear locking phenomena and to eliminate the spurious zero energy mode. In this paper, for the ultimate strength analysis of stiffened shell structures considering effects of residual stresses, the return mapping algorithm based on the consistent elasto-plastic tangent modulus is applied to anisotropic shell structures. In addition, the load/displacement incremental scheme is adopted for non-linear F.E. analysis. Based on such methodology, the computer program is developed and numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with the results in literatures.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.367-375
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• 2011

In this study, structural behavior of bolted joints which were important elements in plate girder design was analyzed using commercial FE analysis program. Also, the numerical analysis method that simply showed behavior of bolts was proposed using the connector element of ABAQUS, nonlinear FE program. Numerical analysis was conducted to verify the proposed numerical analysis method on the basis of the experiment of previous study. In order to investigate effects of action force which was changed by locations of the bolted joints, the three different models were developed by the locations of the bolted joints and behavior for the each model was compared and analyzed by various design parameters (area of splice plates, stiffness of splice plates, and stiffness of bolts). The moment-displacement relations of structures for the various design parameters were investigated to analyze effects of each parameter in ultimate behavior of the structures. Also, the effects of each parameter were compared by force.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.503-512
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• 2010

In AASHTO LRFD (2007), a compact section is defined as a section in which no premature failure caused by local buckling of web and flange plate or later buckling occurs before the section reaches the plastic moment, Mp. The current AASHTO LRFD (2007) provides the compact section requirement by limiting the web slenderness only for webs without longitudinal stiffeners. The role of longitudinal stiffener is to increase the web buckling strength caused flexure. Although a web does not satisfy the compactness requirement without longitudinal stiffeners, the web buckling can be prevented by use of valid longitudinal stiffeners. Therefore, the web may be able to reach the plastic moment. However, the reason why a longitudinal stiffener may not be used to satisfy compactness requirement is not cleary explained in AASHTO LRFD (2007). In this study, the buckling and ultimate strength behaviors of stiffened webs subjected to bending are investigated through the linear buckling and nonlinear finite element analysis. It is found that steel plate girders having webs that do not satisfy the compactness requirement are able to reach the plastic moment if the longitudinal stiffeners have sufficient rigidities and are properly located. From a nonlinear regression analysis of the results, a new compactness requirement is suggested for webs stiffened with one longitudinal stiffener.

• Proceedings of KOSOMES biannual meeting
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• 2004.05b
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• pp.121-125
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• 2004

Recently, High Tensile Steel is adapt to thin plate on the steel structure and marine structure is used widely, It is possible for buckling happens great. Specially, Initial deflection of ship structure happens in place absence necessarily by heat processing of welding or cutting etc. This Initial Deflection is exerted negative impact when thin plate absence complicated nonlinear behaviour accompanied secondary budding. As a result, must idealize initial deflection that occurrence is possible to endow stability and accuracy in the hull structure or marine structure and reflect in early structure design considering secondary buckling. Longi direction of compressive load interacts and analyzed finite element series analysis that apply various kinds initial deflection shape measured actually on occasion that is arranged simply supported condition in this research. Applied ANSYS (elasto-plasticity large deformation finite element method) to be mediocrity finite element program for analysis method and analysis control used in Newton-Raphson method & Arc-length method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.149-150
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• 2013

Recently, various types of perforated breakwaters are being constructed for protecting offshore storm waves. In general, perforated breakwaters have wave chambers with perforated walls at seaside. Purposes of the wave chambers are to reduce wave reflections and maximum wave forces acting on the breakwater. Impact wave forces due to wave breaking can attack to the perforated wall directly, so the effects have to be considered in the design of the perforated wall carefully. Using resonance channels for wave energy dissipation, a new concept perforated breakwater is proposed, which is free from impact loads. Numerical simulation was made for wave reflection characteristics of the breakwater with respect to major design parameters. Numerical analysis was carried out using the Galerkin's FE model based on the linear potential theory considering energy dissipation on the perforated plate. Variations of wave reflection was investigated according to perforated ratios of perforated plate.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.335-345
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• 2008

In this study, we suggest a stochastic finite element scheme for the probabilistic analysis of the composite laminated plates, which have been applied to variety of mechanical structures due to their high strength to weight ratios. The applied concept in the formulation is the weighted integral method, which has been shown to give the most accurate results among others. We take into account the elastic modulus and in-plane shear modulus as random. For individual random parameters, independent stochastic field functions are assumed, and the effect of these random parameters on the response are estimated based on the exponentially varying auto- and cross-correlation functions. Based on example analyses, we suggest that composite plates show a less coefficient of variation than plates of isotropic and orthotropic materials. For the validation of the proposed scheme, Monte Carlo analysis is also performed, and the results are compared with each other.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1120-1131
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• 2011

Researches using time reversal acoustics(TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of a plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric(PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.