• Journal of the Korea Society for Simulation
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• v.15 no.3
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• pp.103-114
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• 2006

Now distribution centers include an ASRS (Automated Storage and Retrieving System) and automated transfer systems such as conveyors and AGV (Automated Guided Vehicle). These automated distribution centers have lots of parameters to be considered fur operating performance. The general basic parameters in the distribution centers are specifications of storage equipment, system operating rules, configuration of storage area and unit load features. In this paper, an approach using simulation and metamodeling with response Surface method to optimize the design parameters of an automated distribution center model is presented. The simulation based metamodel will constitute an efficient approximation of the system function, and the approximate function will be used to design rapid optimal parameters of the distribution center model. This paper provides a comprehensive framework for economical material flow system design using the simulation and metamodeling.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.27-34
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• 2010

Recently, high-speed railway systems have gained increased interest as a means of environmental friendly transportation, and numerous bridges for high-speed railways have been constructed accordingly. However, bridge design for high-speed railways requires more consideration than conventional railway design because fast-moving trains will lead to significant impact on bridge structures. Thus, this research proposes a revised design considering both bridge-rail longitudinal interaction and dynamic effect of trains to ensure stability of fast travelling trains. To validate the proposed design algorithm, numerical analyses are performed and compared using a constructed 250 m long bridge with 5 spans for a high-speed railway. From the numerical results, the proposed optimum design of high-speed railway bridges exhibits the most economic life-cycle-cost (LCC) when compared with several existing design approaches.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.66-69
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• 2008

This study presents deflection analysis of long span structures for pedestrian bridge on crossroads. For long span structures, the size of structural members should be determined considering the esthetic view and vehicle below the structures. As a result, the slenderness ratio of members is increased and the structure may be suffered from significant deflection. The under-tensioned system on lower part of the structure, is applied in order to reduce the deflection and the size of members. In this regard, the under-tensioned system enables the load of upper parts to carη to the end of beam by means of tensional force in cable. In addition, effectiveness of under-tensioned system can be different depending on the size of cable, the number and spacing of posts. This study is performed with conforming the effect by analytical various parameters (size of cable, number and spacing of post). Dead and live loads is supposed to apply in the slab, and the analytical result by MIDAS program are presented addressing the effect of the under-tensioned system.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.1
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• pp.143-148
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• 2011

In this study, the damage to the bridge structure such as the crack and water leakage was assessed due to the increase of the vehicle load and traffic on the roads. In order to make this into the database, as a part of the automation system development for the bridge maintenance, the students themselves designed and developed their own inspection robotic system based on the idea of robots currently being developed overseas. Its field testing was conducted and its applicability assessed. During the design and fabrication, its connection to the details of the unit course taken in the undergraduate level was focused. In terms of new product development, the field application was possible due to the support of the academic-industrial cooperation firms. Furthermore, through the survey of the students, the improvements in the practical skills of the students who participated in this development process was affirmed.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.49-58
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• 2003

Underground flexible pipes for electric cables are subject to external loads and surrounding soil pressure. Particularly, strain of flexible pipes is of great concern in terms of safety and maintenance for electric cables. In this paper, stress and strain of flexible pipes with various installation depth are compared using traditional formula, FEM analysis, model soil box test and field test. from the findings of various analyses, considering the strain criteria-maximum 3.5%, it is suggested that flexible pipes can be buried at the depth of 80cm without additional soil improvement.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.156-163
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• 2002

Hollow core slabs generally have not been used for a bridge or a parking slab in Korea. In this study, high performance hollow core slabs, which have been the most thick one in domestic are re-designed and examined for practical use. Flexural tests were performed on four 315mm deep hollow core slabs to investigate adaptability for high vehicle live loadings and composite action with topping concrete. The precast slabs were pre-tensioned with ten strands of 1/2 inch diameter at the lower of slab and four strands of 1/2 inch diameter at the upper of slab, and cast with 80 mm deep topping concrete. Tested hollow core slabs showed ductile failure behaviors which were conformed to the current Ultimate Strength Design Method for a span of 10m up to the live load of 1,000 kgf/㎡. The rectangular md round shear cotters which were used for the composite action between precast and topping concrete, developed sufficient strengths because cracking, even micro had not been developed at the end of slabs up to the pure flexural tensile failure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.757-762
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• 2010

Owing to the high specific strength and stiffness of composite materials, they are extensively used in mechanical systems and in vehicle industries. However, most mechanical structures experience repeated load and fatigue. Therefore, it is important to perform fatigue analysis of fiber-reinforced composites. The properties of composite laminates vary depending upon the stacking sequence and stacking direction. Fatigue damage of composite laminates occurs according to the following sequence: matrix cracking, delamination, and fiber breakage. In this study, fatigue tests were performed for damage analysis. Fatigue damages, which have to be considered in fatigue analysis, are determined by using the stiffness values calculated from hysteresis loops, and the obtained fatigue damage curve is examined using Mao's equation and Abdelal's equation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.203-209
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• 2010

In this study, the fatigue characteristics and life of a woven glass fabric/epoxy laminate composite applied to railway vehicles was evaluated. The fatigue test was conducted using a tension-tension load with a stress ratio R of 0.1 and frequency of 5 Hz. Two types of woven glass fabric/epoxy laminate composite was used in the fatigue test: with and without carbon/epoxy ply reinforcement. In addition, the fatigue life of the woven glass fabric/epoxy laminate composite was compared with that of aluminum 6005, which is used in the car body and underframe structures of railway vehicles. The test results showed that the failure strength and life of the woven glass fabric/epoxy laminate composite reinforced with three carbon/epoxy plies had a remarkable improvement compared with that of the bare specimen without reinforcement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.813-820
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• 2010

The vertical roller mill is important for machine grinding and mixing various crude materials in the process of producing Portland cement. A vertical roller mill is subjected to cyclic bending stress because of the roller load. Because of the cyclic bending stress, only $4{\times}10^6-8{\times}10^6$ cycles are achieved instead of $4{\times}10^7$ cycles. The stress also causes fractures at the edge of grinding path of the outer roller. The expenses incurred in repairing the grinding path amounts to 30% of the total maintenance cost. Therefore, it is desirable to redesign the vertical roller mill in order to reduce the expenses incurred in repairing the roller. In this study, artificial neural networks (ANNs) were applied in order to solve the multiobjective optimization problem for vertical roller mills by using the function approximation ability of ANNs. To learn and generalize ANNs, the maximum and minimum stresses were estimated from the results of the finite-element analysis of a vertical roller mill. Thus, ANNs could be applied to solve the multiobjective optimization problem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.137-142
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• 2017

Recently, the reduction of vehicle weight has been increasingly studied, in order to enhance the fuel efficiency of passenger cars. In particular, the seat frame is being studied actively, owing to considerations of driver safety from external impact damage. Therefore, this study focuses on high strength steel sheet (SPFC980)/polymer heterojunction hybrid materials, and their performance in regards to impact energy absorption. The ratio of impact energy absorption was observed to be relatively higher in the SPFC980/polymer hybrid materials under the impact load. This was found by calculating the equivalent flexural rigidity, which is the bending effect, according to the Castigliano theorem. An efficient wire-web structure was investigated through the simulation of different wire-web designs such as triangular, rectangular, octagonal, and hexagonal structures. The hexagonal wire-web structure was shown to have the least impact damage, according to the simulations. This study can be utilized for seat frame design for passengers' safety, owing to efficient impact absorption.