• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.10a
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• pp.133-138
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• 1991

The aim of the present paper is to develop a computer program predicting ultimate fracture strength of initially cracked structure under monotonically increasing external loads. For this purpose, two kinds of 3-D isoparametric solid elements, one 6-node wedge element and another 8-node brick element are formulated along the small deformation theory. Plasticity in the element is checked using von Mises' yield criterion. Elasto-plastic stiffness matrix of the element is calculated taking account of strain hardening effect. If the principal strain at crack tip which is one nodal point exceeds the critical strain dependin on the material property, crack tip is supposed to be opened and the crack tip node which was previously constrained in the direction perpendicular to the crack line is released. After that, the crack lay be propagated to the adjacent node. Once a crack tip node is fractured, the energy of the newly fractured node should be released which is to be absorbed by the remaining part. The accumulated reaction force which was carried by the newly fractured node so far is then applied in the opposite direction. During the action of crack tip relief force, since unloading may be occured in the plastic element, unloading check should be made. If a plastic element unloads, elastic stress-strain equation is used in the calculation of the stiffness matrix of the element, while for a loading element, elasto-plastic stress-strain equation is continuously used. Verification of the computer program is made comparing with the experimental results for center cracked panel subjected to uniform tensile load. Also some factors affecting ultimate fracture strength of initially cracked plate are investigated. It is concluded that the computer program developed here gives an accurate solution and becomes useful tool for predicting ultimate fracture load of initially cracked structural system under monotonically increasing external loads.

• Safety and Health at Work
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• v.6 no.3
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• pp.200-205
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• 2015

Background: Construction activity has made considerable breakthroughs in the past two decades on the back of increases in development activities, government policies, and public demand. At the same time, occupational health and safety issues have become a major concern to construction organizations. The unsatisfactory safety performance of the construction industry has always been highlighted since the safety management system is neglected area and not implemented systematically in Indian construction organizations. Due to a lack of enforcement of the applicable legislation, most of the construction organizations are forced to opt for the implementation of Occupational Health Safety Assessment Series (OHSAS) 18001 to improve safety performance. Methods: In order to better understand factors influencing the implementation of OHSAS 18001, an interpretive structural modeling approach has been applied and the factors have been classified using matrice d'impacts croises-multiplication $appliqu{\acute{e}}$ a un classement (MICMAC) analysis. The study proposes the underlying theoretical framework to identify factors and to help management of Indian construction organizations to understand the interaction among factors influencing in implementation of OHSAS 18001. Results: Safety culture, continual improvement, morale of employees, and safety training have been identified as dependent variables. Safety performance, sustainable construction, and conducive working environment have been identified as linkage variables. Management commitment and safety policy have been identified as the driver variables. Conclusion: Management commitment has the maximum driving power and the most influential factor is safety policy, which states clearly the commitment of top management towards occupational safety and health.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.3
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• pp.100-108
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• 2016

The purpose of this study is to present a business strategy plan to increase organizational effectiveness of small and medium-sized enterprises. The research investigated in the level of human resource activity, such as recruitment, education, evaluation, compensation and development for the employees and executives who are working at small and medium-sized enterprises where located in Busan and Gyongnam province. With this, the research carried out actual proof analysis on the level of human resource activity effects on organization effectiveness like job satisfaction and organizational commitment. The following implications can be acquired from the result of multiple regression analysis on the 201 employees of small and medium enterprises. First, small and medium-sized enterprises should carry out human resource management activities and improve research and development capacity to enhance organization effectiveness. Second, in order to improve job satisfaction of the members of small and medium-sized enterprises, the management should concentrate on recruitment activity and reward maintenance management activity and come up with strategies to enhance learning ability and external network ability. Third, in order to enhance organizational commitment of the members of small and medium-sized enterprises, recruitment activity, training activity, and reward maintenance management activity should be carried out and the management should come up with strategies to enhance learning ability and external network ability. In this research, the objective was only to find out antecedents of organization effectiveness, but considering that causality might arise among the antecedents, in the studies hereafter, the verification on the structural relationship of various factors will be needed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.83-90
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• 1998

Stage transformation characteristics of Li, K and Na-graphite deintercalation compounds (GDICs) were studied under consideration of a deintercalation mechanism of the intercalants between carbon layers. Li-graphite intercalation compounds (GICs) synthesized by a controlling temperatures and pressures have been spontaneously decomposed in the atmosphere. By X-ray differaction analysis the $d_{001}$-values of stage 1 and 2 were identified to be 3.71 and 7.06 $\AA$, respectively. After 6 weeks, the deintercalation reaction of the Li-GICs ceased and only residual compounds could be observed. K-GICs were synthesized by the modified two-bulb method resulting in structural stabilities and stage transitions. By X-ray diffraction analysis the very stable K-graphite residue compounds were observed after 10 weeks. Na-GICs with stage 1 and 2 were synthesized using the high temperature and pressure technique. The temperature dependence of a deintercalation reaction and a thermal stability of Na-GICs were discussed. The structure changes of the Na-GDICs depending on heating rates were identified by X-ray diffraction. According to the deintercalation process, the stage transformations could be attributed to irregular deintercalations of the GDICs with disordered stage.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.2
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• pp.243-248
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• 2014

The permanent magnet linear synchronous motors facilitate maintenance, for it is structurally simple compare to rotating machine and has lots of advantage such as a precision control, high speed, high thrust and so on. However, it causes an increase of material cost because of structural characteristics that need to arranges the armature on the full length of transportation lines. Thus, in order to resolve this problem, we propose the discontinuous arrangement method of the armature but the edge always exists due to the structure when the armature is arranged discontinuously. Due to this edge, the cogging force is greatly generated and it causes thrust force ripple generating noise, vibration and decline of performance. Therefore, in this paper, we examined the characteristic of end edge according to the skew angle through 3-D numerical analysis using finite element method(FEM) and improved the operation characteristics.

• Structural Engineering and Mechanics
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• v.64 no.3
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• pp.361-379
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• 2017

In this article, the vibration behavior of double-bonded sandwich microplates with homogeneous core and nanocomposite facesheets reinforced by carbon nanotube and boron nitride nanotube under multi physical fields such as 2D magnetic and electric fields is investigated. Symmetric and un-symmetric distributions of nanotubes are considered for facesheets of sandwich microplates such as uniform distribution and various functionally graded distributions. The double-bonded sandwich microplates rest on visco-Pasternak foundation. Material properties of sandwich microplates are obtained by the extended rule of mixture. The sinusoidal shear deformation theory (SSDT) is employed to describe displacement fields of sandwich microplates. Also, the dimensionless natural frequency is obtained by classical plate theory (CPT) and compared with the obtained results by SSDT. It can be seen that the obtained dimensionless natural frequencies by CPT are higher than SSDT. In order to study the material length scale parameters, modified strain gradient theory at micro scale is utilized and then, the equations of motion are derived using Hamilton's principle. The effects of different parameters such as foundation parameters including Winkler, shear layer and damping coefficients, various distributions and volume fraction of nanotubes, core to facesheet thickness ratio, aspect and side ratios on the dimensionless natural frequencies are discussed in details. The results of present work can be used to optimum design and control of similar systems such as micro-electro-mechanical and nano-electro-mechanical devices.

• Steel and Composite Structures
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• v.35 no.2
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• pp.187-197
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• 2020

Ground motion records are commonly used for fragility curves (FCs) developing utilized in seismic loss estimating analysis for earthquake prone zones. These records could be 'real', say the recorded acceleration time series or 'simulated' records consistent with the regional seismicity and produced by use of alternative simulation methods. This study has focused on fragility curves developing for masonry buildings through computational 'simulated' ground motion records while evaluating the properness of these fragilities compared to the curves generated by the use of 'real' records. Assessing the dynamic responses of structures, nonlinear computational time history analyses through the equivalent single degree of freedom systems have been implemented on OpenSees platform. Accordingly, computational structural analyses of multi-story 3D frame structures with different stiffening members considering soil interaction have been carried out with finite element software according to (1992) Earthquake East-West component. The obtained results have been compared to each frame regarding soil interaction. Conclusion and recommendations with the discuss of obtaining findings are presented.

• Composites Research
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• v.22 no.2
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• pp.30-36
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• 2009

In this paper, we propose the design method for the composite torque link of a landing gear for a helicopter. The composite torque link has to be light weighted and very stiff to keep the shock absorber in the landing gear of helicopter. The configuration and structural shape has to be designed in consideration of the RTM (Resin Transfer Molding) manufacturing process which is adopted to minimize the manufacturing cost. The mechanical properties are obtained through the coupon tests with the specimens made by the same manufacturing process for the composite structure. The optimal design process was performed through iterative modifications of the models which were verified by stress analysis using FEM. The composite torque link has lug-shaped parts and is very thick, so 3D Layered solid elements of ABAQUS were used to get the stress field including the stress components in thickness direction and non-linear static analysis using contact B.C. of rigid-deform condition was used to get the optimal design.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.145-157
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• 2008

Load transfer efficiency (LTE) reflects the structural performance of doweled and undoweled joints of Jointed Concrete Pavement (JCP). A 3-dimensional (3-D) model of JCP was built using ABAQUS software in this study. Three concrete slabs were placed on bonded sublayers composed of a base and subgrade. Spring elements were used to connect the adjacent slabs at joints. Different spring constants were input to the model to simulate different joint stiffness of the concrete pavement. The LTE of the joint increased with an increase of the spring constant. The effects of material properties and geometric shape on the behavior of JCP were analyzed using different elastic modulus and thickness of the slab and base in the modeling. The results showed the elastic modulus of the subgrade affected the behavior of the slab and LTE more than that of the base and the thickness of the slab and base. The effects of a negative temperature gradient on the behavior of the slab and LTE were more than that of positive and zero temperature gradients. Joints with low stiffness were more sensitive to the temperature gradient of the slab.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.25-29
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• 2012

The properties of carbon nanotube-metal hybrid nanostructures are critically dependent on the structure and chemistry of the metal-carbon nanotube interface. In this study, the interface between nickel and multi-walled carbon nanotubes (CNTs) has been investigated using physical vapor-deposited (sputter-deposited) nickel onto the surface of freestanding carbon nanotube arrays processed by nano-imprint lithography (NIL). These interfaces have been characterized by transmission electron microscopy and 3D atom probe tomography. In the nickel nanocrystals growing on the CNT surface, a metastable hexagonal $Ni_3C$-types phase appears to be stabilized. The structural stability of the nickel-CNT interface is also discussed and related to potential implications for the properties of these nanocomposites.