• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1784-1793
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• 2001

The flow fields around an elliptic cylinder of axis ratio AR=2 adjacent to a free surface were investigated experimentally using a water channel. The main objective is to understand the effect of the free surface on the flow structure in the near-wake. The flow fields were measured by varying the depth of cylinder submergence, for each experimental condition, 350 velocity fields were measured using a single-frame PIV system and ensemble-averaged to obtain the spatial distribution of turbulent statics. For small submergence depths a large-scale eddy structure was observed in the near-wake, causing a reverse flow near the free surface, downstream of the cylinder. As the depth of cylinder submergence was increased, the flow speed in the gap region between the upper surface of the cylinder and the free surface increased and formed a substantial jet flow. The general flow structure of the elliptic cylinder is similar to previous results for a circular cylinder submerged near to a free surface. However, the width of the wake and the angle of downward deflection of the shear layer developed from the lower surface of the elliptic cylinder are smaller tan those for a circular cylinder.

• Steel and Composite Structures
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• v.33 no.6
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• pp.865-875
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• 2019

The current article proposed to develop a geometrical model for the analysis and modelling of the uniaxial functionally graded structure using the higher-order displacement kinematics with and without the presence of porosity including the distribution. Additionally, the formulation is capable of modelling three different kinds of grading patterns i.e., Power-law, sigmoid and exponential distribution of the individual constituents through the thickness direction. Also, the model includes the distribution of porosity (even and uneven kind) through the panel thickness. The structural governing equation of the porous graded structure is obtained (Hamilton's principle) and solved mathematically by means of the isoparametric finite element technique. Initially, the linear frequency parameters are obtained for different geometrical configuration via own computer code. The comparison and the corresponding convergence studies are performed for the unidirectional FG structure for the validation purpose. Finally, the impact of different influencing parameters like aspect ratio (O), thickness ratio (S), curvature ratio (R/h), porosity index (λ), type of porosity (even or uneven), power-law exponent (n), boundary condition on the free vibration characteristics are obtained for the FG panel and discussed in details.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.256-263
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• 2006

In this paper, an experimental hybrid method, which implements the earthquake response control of a building structure with a TLD(Tuned Liquid Damper) by using only a TLD as an experimental part, is proposed and is experimentally verified through a shaking table test. In the proposed methodology, the whole building structure with a TLD is divided into the upper TLD and the lower structural parts as experimental and numerical substructures, respectively. At the moment, the control force acting between their interface is measured from the experimental TLD with shear-type load-cell which is mounted on shaking table. Shaking table vibrates the upper experimental TLD with the response calculated from the numerical substructure, which is subjected to the excitations of the measured interface control force at its top story and an earthquake input at its base. The experimental results show that the conventional method, in which both a TLD and a building structure model are physically manufactured and are tested, can be replaced by the proposed methodology with a simple experimental installation and a good accuracy for evaluating the control performance of a TLD.

• Special Issue of the Society of Naval Architects of Korea
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• 2013.12a
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• pp.81-84
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• 2013

일반적인 Bulk carrier는 Single deck, Double bottom, Hopper side tank, Top side tank와 함께 Single side skin 또는 Double side skin으로 구성되어 Single hull bulk carrier 또는 Double hull bulk carrier라 불린다. 본 논문의 연구선박인 Double hull bulk carrier는 CSR에서 규정짓고 있는 Double hull bulk carrier의 특징 중 Hopper side tank가 없기에 일반적인 Double hull bulk carrier와는 다른 구조를 가진다. 구조적 특징으로는 Inner bottom과 Inner hull 연결부위에 응력 집중 발생, Side shell의 Shear에 대해 구조적 안전성, Double hull에 대한 CSR for bulk carrier의 Rule적용 여부에 대한 판단 등이 있다. 따라서 본 연구에서는 Double hull bulk carrier의 구조적 특징과 구조해석을 통한 응력 집중 부위의 평가 및 Fatigue analysis을 통한 피로수명을 계산하여 이를 통해 구조의 안전성을 살펴보고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.337-341
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• 2004

This paper concerns the analytical modeling and dynamic analysis of advanced rotating blade structure implemented by a dual approach based on structural tailoring and viscoelastic materials technology. Whereas structural tailoring uses the directionality properties of advanced composite materials, the passive materials technology exploits the damping capabilities of viscoelastic material(VEM) embedded into the host structure. The structure is modeled as a composite thin-walled beam incorporating a number of nonclassical features such as transverse shear, warping restraint, anisotropy of constituent materials, and warping and rotary inertias. The VEM layer damping treatment is modeled by using the Golla-Mushes-McTavish(GHM) method, which is employed to account for the frequency-dependent characteristic o the VEM. The displayed numerical results provide a comprehensive picture of the synergistic implications of the application of both techniques, namely, the tailoring and damping technology on vibration response of thin-walled beam structure exposed to external time-dependent excitations.

• Steel and Composite Structures
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• v.37 no.1
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• pp.99-115
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• 2020

This article deals with the dynamic analysis in pad concrete foundation containing Silica nanoparticles (SiO₂) subject to seismic load. In order to control the foundation smartly, a piezoelectric layer covered the foundation. The weight of the building by a column on the foundation is assumed with an external force in the middle of the structure. The foundation is located in soil medium which is modeled by spring elements. The Mori-Tanaka law is utilized for calculating the equivalent mechanical characteristics of the concrete foundation. The Kevin-Voigt model is adopted to take into account the structural damping. The concrete structure is modeled by a thick plate and the governing equations are deduced using Hamilton's principle under the assumption of higher-order shear deformation theory (HSDT). The differential quadrature method (DQM) and the Newmark method are applied to obtain the seismic response. The effects of the applied voltage to the smart layer, agglomeration and volume percent of SiO₂ nanoparticles, damping of the structure, geometrical parameters and soil medium of the structure are assessed on the dynamic response. It has been demonstrated by the numerical results that by applying a negative voltage, the dynamic deflection is reduced significantly. Moreover, silica nanoparticles reduce the dynamic deflection of the concrete foundation.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.445-455
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• 2000

This study proposed to beam-column joint model consisting of different type structural member to develop new structural system in the structural viewpoint as to a method to overcome various problem according to change of construction environment. This study promoted rigidity and capacity to stiffen reinforced concrete for steel structure end to increase rigidity of long spaned steel beam, and welt to steel flange to anchor U-shaped main bar of SRC structure end to easy stress flow between the different type structure. Through the series of experiments, proposed to possibility of this joint model, and investigated joint rigidity and capacity.

• Journal of the Korean Society of Industry Convergence
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• v.11 no.3
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• pp.127-134
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• 2008

This study is to develop the structure analysis and optimization algorithm of the strut supported temporary structure for underground constructions. Developed algorithm performs the analysis and the optimization of each strut, wale, and H pile of temporary structures separately. The design variables of nonlinear optimization consist of the cross-sections of temporary structures such as strut, wale, and H pile and the solution of the nonlinear programming is searched using for the method of successive unconstranint minimization technique. The weight of the structure is used for the object function of nonlinear programming. the constraints are derived from the specification of the temporary structures as compressive axial, bending, shear, composite stress and serviceability. The structural analysis is performed based on the elastoplastic beam theory. This developed program can be used to evaluate the applicability, convergence, and effectiveness of the temporary structures.

• Structural Engineering and Mechanics
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• v.56 no.6
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• pp.1021-1040
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• 2015

An effective method to calculate aerodynamic loads and aeroelastic responses of large wind turbine tower-blade coupled structures in yaw condition is proposed. By a case study on a 5 MW large wind turbine, the finite element model of the wind turbine tower-blade coupled structure is established to obtain the modal information. The harmonic superposition method and modified blade-element momentum theory are used to calculate aerodynamic loads in yaw condition, in which the wind shear, tower shadow, tower-blade modal and aerodynamic interactions, and rotational effects are fully taken into account. The mode superposition method is used to calculate kinetic equation of wind turbine tower-blade coupled structure in time domain. The induced velocity and dynamic loads are updated through iterative loop, and the aeroelastic responses of large wind turbine tower-blade coupled system are then obtained. For completeness, the yaw effect and aeroelastic effect on aerodynamic loads and wind-induced responses are discussed in detail based on the calculating results.

• Wind and Structures
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• v.30 no.4
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• pp.379-392
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• 2020

The paper presents a Life-Cycle Cost-based optimization framework for wind-excited tall buildings equipped with Tuned Mass Dampers (TMDs). The objective is to minimize the Life-Cycle Cost that comprises initial costs of the structure, the control system and costs related to repair, maintenance and downtime over the building's lifetime. The integrated optimization of structural sections and mass ratio of the TMDs is carried out, leading to a set of Pareto optimal solutions. The main advantage of the proposed methodology is that, differently from the traditional optimal design approach, it allows to perform the unified design of both the structure and the control system in a Life Cycle Cost Analysis framework. The procedure quantifies wind-induced losses, related to structural and nonstructural damage, considering the stochastic nature of the loads (wind velocity and direction), the specificity of the structural modeling (e.g., non-shear-type vibration modes and torsional effects) and the presence of the TMDs. Both serviceability and ultimate limit states related to the structure and the TMDs' damage are adopted for the computation of repair costs. The application to a case study tall building allows to demonstrate the efficiency of the procedure for the integrated design of the structure and the control system.