• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.497-504
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• 1988

The steady state thermal stress intensity factors (TSIF's) are analyzed for hypocycloid, symmetric airfoil and symmetric lip type rigid inclusions embedded in infinite elastic solids, using Boganoff's complex variable approach in plane thermoplasticity. Two thermal conditions are considered, one with an uniform heat flow disturbed by an insulated rigid inclusion of cusp crack shape and the other with an uniform heat flow disturbed by a rigid inclusion of cusp crack shape with fixed boundary temperature. The tendencies of TSIF's for rigid inclusions of cusp crack shape are somewhat different from those of traction free cusp cracks. However, if k=-1, the non-dimensionalized TSIF's for rigid inclusions of cusp crack shape become those of traction free cusp cracks like the tendencies of the SIF's under mechanical loading conditions. The thermal stress and displacement components for a rigid circular inclusion of radius Ro are drived from the results of a hypocycloid crack type rigid inclusion.

• Computers and Concrete
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• v.2 no.4
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• pp.309-324
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• 2005

The moment-curvature relationship of reinforced concrete beams made of normal- and high-strength concrete experiencing complex load history is studied using a numerical method that employs the actual stress-strain curves of the constitutive materials and takes into account the stress-path dependence of the concrete and steel reinforcement. The load history considered includes loading, unloading and reloading. From the results obtained, it is found that the complete moment-curvature relationship, which is also path-dependent, is similar to the material stress-strain relationship with stress-path dependence. However, the unloading part of the moment-curvature relationship of the beam section is elastic but not perfectly linear, although the unloading of both concrete and steel is assumed to be linearly elastic. It is also observed that when unloading happens, the variation of neutral axis depth has different trends for under- and over-reinforced sections. Moreover, even when the section is fully unloaded, there are still residual curvature and stress in the section in some circumstances. Various issues related to the post-peak behavior of reinforced concrete beams are also discussed.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.6 s.46
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• pp.67-73
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• 2005

Precise analysis of soil-structure interaction requires a proper description of soil profile. However, such approach becomes generally nearly unpractical for soil exhibiting material discontinuity and complex geometry since meshes should match that material discontinuity line. To overcome these difficulties, a different numerical integration method is adopted in this paper, which enables to integrate easily over an element with material discontinuity without regenerating mesh fellowing the discontinuity line. As a result the mesh is highly structured, loading to very regular silliness matrix. The influence of the shape of soil profile on the response is examined and it is seen that the proposed soil-structure analysis method can be easily used on soil-structure interaction problems with complicated soil profile and produce reliable results regardless of material discontinuities.

• Macromolecular Research
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• v.17 no.7
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• pp.538-543
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• 2009

In this study, methotrexate (MTX)-encapsulated polymeric micelles using methoxy poly(ethylene glycol) (MPEG)-grafted chitosan (ChitoPEG) copolymer were prepared. The MIX-incorporated polymeric micelles of ChitoPEG copolymer has a particle size of around 50-100 nm. In 1H nuclear magnetic resonance (NMR) study, the specific peaks of MTX disappeared in heavy water ($D_2O$) and only the specific peak of MPEG was observed, while all of the peaks were confirmed in dimethyl sulfoxide (DMSO). These results indicated that MTX was complexed with chitosan and then formed an ion complex inner-core of the polymeric micelle in an aqueous environment. The drug contents of the polymeric micelle were around $4{\sim}12%$ and the loading efficiency of MTX in the polymeric micelles was higher than 60% (w/w) for all of the formulations. The cytotoxicity of MIX and MTX-incorporated polymeric micelle against CT26 tumor cells was not significantly changed.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.15-24
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• 2005

Modeling techniques of piled pier were reviewed and the influences of pile cap's boundary conditions were analyzed in this study. The method using flexible springs seems to be useful fur the practical design since its simplified model can represent the complex behaviors of pile groups efficiently. Parameter studies were performed far various pile group arrangements, pile spacings, end bearing conditions, and loading stages to analyze their effects on the lateral displacements, maximum pile bending stresses, and lateral stiffness of pile groups. Through the parameter studies, it was found that when lateral stiffness of pile groups was estimated by using three-dimensional analysis method (YSGroup), its complex behavior could be predicted better than other methods based on single pile analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.8064-8073
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• 2015

One of the efficient procedures for the solution of partial differential equations is the method of differential quadrature. This method has been applied to a large number of cases to circumvent the difficulties of the complex algorithms of programming for the computer, as well as excessive use of storage due to conditions of complex geometry and loading. In-plane vibrations of curved beams with inextensibility and extensibility of the arch axis are analyzed by the differential quadrature method (DQM). Fundamental frequencies are calculated for the member with various end conditions and opening angles. The results are compared with exact experimental and numerical results by other methods for cases in which they are available. The DQM gives good accuracy even when only a limited number of grid points is used, and new results according to diverse variation are also suggested.

• Smart Structures and Systems
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• v.24 no.6
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• pp.783-791
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• 2019

Prefabricated reinforced-concrete shear walls are used extensively in building structures because they are convenient to construct and environmentally sustainable. To make large walls easier to transport, they are divided into smaller segments and then assembled at the construction site using a variety of connection methods. The present paper proposes a precast shear wall assembled using steel shear keys, wherein the shear keys are fixed on the embedded steel plates of adjacent wall segments by combined plug and fillet welding. The anchoring strength of shear keys is known to affect the mechanical properties of the wall segments. Loading tests were therefore performed to observe the behavior of precast shear wall specimens with different anchoring components for shear keys. The specimen with insufficient strength of anchoring components was found to have reduced stiffness and lateral resistance. Conversely, an extremely high anchoring strength led to a short-column effect at the base of the wall segments and low deformation ability. Finally, for practical engineering purposes, a design approach involving the safety coefficient of anchoring components for steel shear keys is suggested.

• Wind and Structures
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• v.29 no.3
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• pp.195-207
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• 2019

This paper presents an overview of wind turbine research techniques including the recent application of hybrid testing. Wind turbines are complex structures as they are large, slender, and dynamic with many different operational states, which limits applicable research techniques. Traditionally, numerical simulation is widely used to study turbines while experimental tests are rarer and often face cost and equipment restrictions. Hybrid testing is a relatively new simulation method that combines numerical and experimental techniques to accurately capture unknown or complex behaviour by modelling portions of the structure experimentally while numerically simulating the remainder. This can allow for increased detail, scope, and feasibility in wind turbine tests. Hybrid testing appears to be an effective tool for future wind turbine research, and the few studies that have applied it have shown promising results. This paper presents a literature review of experimental and numerical wind turbine testing, hybrid testing in structural engineering, and hybrid testing of wind turbines. Finally, several applications of hybrid testing for future wind turbine studies are proposed including multi-hazard loading, damped turbines, and turbine failure.

• Steel and Composite Structures
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• v.38 no.1
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• pp.79-86
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• 2021

Due to the complex geological conditions, a large number of high quality coal seams was buried in the western of China which cannot be mining in open-pit methods. The dynamic properties of that coal cannot be studied easily in real site for the complex working condition. The compound coal blocks made on the basis of the real situation were studied in the laboratory. The physical and mechanical properties of the compound coal blocks and the raw coal were contrasted by using the UCS tests. The results show that the compound coal blocks made by mixing coal powder, cement and water in proportion of 2.5:2:1 are the closest to that of standard raw coal. Then the propagation of strain waves and crushing effects on the coal were studied in the compound coal blocks by using the super dynamic strain test system and the numerical calculated method of ANSYS/LS-DYNA. The results show that the diameter of the crushing zone in the compound coal blocks was similar to that in the numerical results. The fractures distribution in laboratory tests also has a similar trend to the calculation results. The measured strain waves at the distance of 50 cm, 100 cm, and 150 cm from the center of the charge are mainly concerned at -1.0×104 με and have a similar trend as that in the numerical simulation.

• Wind and Structures
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• v.36 no.2
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• pp.75-90
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• 2023

Turbulent wind flow over hilly terrains has been extensively investigated in the scientific literature and main findings have been included in technical standards. In particular, turbulent wind flow over nominally two-dimensional hills is often adopted as a benchmark to investigate wind turbine siting, estimate wind loading, and dispersion of particles transported by the wind, such as atmospheric pollutants, wind-driven rain, windblown snow. Windblown sand transport affects human-built structures and natural ecosystems in sandy desert and coastal regions, such as transport infrastructures and coastal sand dunes. Windblown sand transport taking place around any kind of obstacle is rarely in equilibrium conditions. As a result, the modelling of windblown sand transport over complex orographies is fundamental, even if seldomly investigated. In this study, the authors present a wind-sand tunnel test campaign carried out on a nominally two-dimensional sinusoidal hill. A first test is carried out on a flat sand fetch without any obstacle to assess sand transport in open field conditions. Then, a second test is carried out on the hill model to assess the sand flux overcoming the hill and the morphodynamic evolution of the sand sedimenting over its upwind slope. Finally, obtained results are condensed into a dimensionless parameter describing its sedimentation capability and compared with values resulting from other nominally two-dimensional obstacles from the literature.