• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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• pp.148-155
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• 2008

The aim of the study is to interpret the distribution of occlusal force by 3-dimensional finite element analysis of ISP(Implant Supported Prosthesis) supported by minimum number of implant to restore the edentulous patients. For this study, the Astra Tech implant system is used. Geometric modeling for 6 and 4 fixture ISP group is performed with respect to the bone, implant and one piece superstructure, respectively. Implants are arbitrarily placed according to the anatomical limit of lower jaw and for the favorable distribution of occlusal force, which is applied at the end of cantilever extension of ISP with 30mm. Element type is tetrahedral for finite element model and the typical mechanical properties, Young's modulus and Poisson's ratio of each material, cortical, cancellous bone and implant material are utilized for the finite element analysis. From this study, we can see the distribution of equivalent stress equal to real situation and speculate the difference in the stress distribution in the whole model and at each implant fixture, From the analysis, the area of maximum stress is distributed on distal contact area between bone and fixture in the crestal bone. The maximum stress is 53MPa at the 0.2mm area from the bone-implant interface in the maximum side for 300N load condition for 4 fixture case, which is slightly less than the stress calculated from allowable strain. This stress has not been deduced to directly cause the loss of crestal bone around implant fixture, but the stress can be much reduced as the old peoples may have lower chewing force. Thus, clinical trial may be performed with this treatment protocol to use 4 fixtured ISP for old patients.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.155-167
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• 2004

In this paper, the inelastic buckling behavior of the beam under uniform bending was investigated using the energy-based method, which can tackle problems in fourth order eigenvalue. The pattern of residual stress was not available to satisfy the I-sections manufactured in Korea. however; therefore, the well-known polynomial and simplified pattern of residual stress was adopted in this study. The inelastic lateral-distortional buckling behavior of the beam with I-sections manufactured in Korea was investigated. The study was then extended to the inelastic lateral-torsional buckling of the beam by minimizing the out-of-plane web distortion. The inelastic lateral-torsional buckling results obtained in this paper were compared with the prediction of allowable bending stress given in the Korean steel designers' manual (1995). Results showed that the importance of inelastic lateral-distortional buckling did not arise for beams under uniform bending. Likewise, the design method in KSDM (1995) was proven to bo too conservative for intermediate and short spans of beams without intermediate bracing.

• Journal of Korea Water Resources Association
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• v.37 no.9
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• pp.719-727
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• 2004

Water quality models can be applied to manage the regional water quality problems and to estimate the target and allowable pollution load in watershed effectively. The optimization of state variables in the given water quality model Is necessary to build up more effective model. The least-squares method is applied to fit field observations in QUAL2E developed by U.S. EPA, which is most widely used one in the world to simulate the stream water quality, and the optimization model with constraints is constructed to estimate the parameters. The objective function of the optimization model is solved by Solver in Microsoft Excel and Monte Carlo simulation is conducted to know the influence of parameter in conventional pollutants. It is found that this technique is easily implemented and rapidly convergent computational procedure to calibrate the parameters after appling this approach in Anyang stream located in Kyonggi province mainly.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.39-46
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• 1990

This paper was analized the thermal conductivity of polystylene (TENSAR- GEOGRID) embeding into the subbase through frost penetration depth, frost heave, change of bearing capacity, and soil moisture movement due to freezing, thawing and icing actions, and their results were as follows : 1.The change of temperature into the sub-base was much increased by the Tensar-Geogrid insertion, and the frost penetration and frost heave were decreased as the thinner of the insulation thickness but the thawing velocity of melting period was appeared to be faster in case of non-insulated. 2.The frost heave had a close relationship with the thickness of insulations which was reasonably included anti-frost effects. 3.The moisture content during the freezing period of upper layer of the insulation insertion was increased by 15 per cent but it was returned to initial state of the thawing period, and at the down layer temporarily increased by 10 per cent and returned to the original state at once. 4.The insulation was acted as a function of distribution of surcharge, and the settlement of the sub-base was about 1.5 mm under 15 tonnage of load and which was included within the allowable limits. 5.The sliding resistance due to the icing which was induced by the insulation insertion into the sub-base was appeared as more 40 per cent than noninsulation area, so that the insulations should be restricted on the place such as mountains, curved and cross area which were required the braking power under the traffics.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.4
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• pp.109-117
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• 2017

Coastal reclamation has created large flat lands, part of which is an attractive site to construct greenhouse complexes for the horticulture industry. Wind environments over these coastal lands are entirely different from those of the inland area, and demand increased structural safety. The objective of this study is to evaluate the structural safety of two single-span greenhouses, peach type and even-span type, under the wind characteristics of coastal reclaimed lands. The wind pressure coefficients acting on the walls and roofs of two greenhouses were measured by wind tunnel experiments, and those acting on the roofs were approximately two times larger than those suggested by the existing design guidelines. Consequently, structural analysis conducted by SAP2000 showed that greenhouse structures designed by the existing guidelines might lead to structural failure under coastal wind conditions because their maximum allowable wind speeds were lower than the design wind speed. Especially, the peach type greenhouse constructed in a reclaimed land could be damaged by approximately 48 % of the design wind speed and needed improvement of structural designs. This study suggested increasing the spacing of rafters with thicker pipes for the peach type greenhouse to enhance economic feasibility of the building under strong wind conditions of reclaimed lands.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.961-972
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• 2002

Flat plate structures under lateral load are susceptible to the brittle shear failure of plate-column connection. To prevent such brittle failure, strength and ductility of the connection should be ensured. However, according to previous studies, current design methods do not accurately estimate the strength of plate-column connection. In the present study, parametric study using nonlinear finite element analysis was performed for interior connections. Based on the numerical results, a design method for the connection was developed. At the critical sections around the connection coexist flexural moment and shear developed by lateral and gravity loads, and maximum allowable eccentric shear stresses were proposed based on the interactions between the flexural moment and shear, The proposed method can precisely predict the strength of the connection, compared with the current design provisions. The predictability of the proposed method was verified by the comparisons with existing experiments and nonlinear numerical analyses.

• Journal of Korean Association for Spatial Structures
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• v.8 no.4
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• pp.73-80
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• 2008

The objective of current study is to develop an optimization technique for the seismic actively controlled building structures using active tendon devices by an efficient solution of LQR control gain. In order to solve the active control system, the Ricatti closed-loop algorithm has been applied, and the state vector has been formulated by the transfer matrix and solved by a numerical technique of the trapezoidal rule. The time-delay problem has been also considered by phase compensation. To optimize the performance index, the ratio of the weighted matrix is the design variable, allowable story drift limits of IBC 2000 and tendon forces have been applied as restraint conditions, and the optimum control program has been developed with the algorithm of the SUMT technique. In examples of the optimization problem of eight stories shear buildings, it is evaluated that the optimum controlled building is more suitable in the control of earthquake response than the uncontrolled system and can reduce the performance index to compare with the controlled system with a constant ratio of the weighted matrix.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.11
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• pp.2886-2896
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• 1996

The Type of Service based multicast routing algorithm is necessary to support efficiently herogeneous applications in ATM network. In this paper I propose the Constrained Multicast Tree with Virtual Destination(DMTVD) heuristic algorithm as least cost multicast routing algorithm. The service is categorized into two types, as delay sensitive and non in CMTVD algorithm. For the delay sensitive service type, the cost optimized route is the Minimum Cost Stenier Tree connecting all the destination node group, virtual destination node group and source node with least costs, subject to the delay along the path being less than the maximum allowable end to end delay. The other side for the non-delay sensitive service, the cost optimized route is the MCST connecting all the multicast groups with least costs, subject to the traffic load is balanced in the network. The CMTVD algorithm is based on the Constrained Multicasting Tree algorithm but regards the nodes branching multiple destination nodes as virtural destination node. The experimental results show that the total route costs is enhanced 10%-15% than the CTM algorithm.

• Structural Engineering and Mechanics
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• v.57 no.3
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• pp.569-585
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• 2016

This paper highlights a case study that investigates the behaviour of existing bridge, West Terrace Bridge, induced by horizontal seismic loading. Unfortunately the lack of past information related to seismic activity within the NSW region has made it difficult to understand better the capacity of the structure if Earthquake occurs. The research was conducted through the University of Western Sydney in conjunction with Railcorp Australia, as part of disaster reduction preparedness program. The focus of seismic analyses was on the assessment of stress behaviour, induced by cyclic horizontal/vertical displacements, within the concrete slab and steel truss of the bridge under various Earthquake Year Return Intervals (YRI) of 1-100, 1-200, 1-250, 1-500, 1-800, 1-1000, 1-1500, 1-2000 and 1-2500. Furthermore the stresses and displacements were rigorously analysed through a parametric study conducted using different boundary conditions. The numerical analysis of the concrete slab and steel truss were performed through the finite element software, ABAQUS. The field measurements and observation had been used to validate the results drawn from the finite element simulation. It was illustrated that under a YRI of 1/1000 the bottom chord of the steel truss failed as the stress induced surpassed the ultimate stress capacity and the horizontal displacement exceeded the allowable displacement measured in the field observations whereas the vertical displacement remained within the previously observed limitations. Furthermore the parametric studies in this paper demonstrate that a change in boundary conditions alleviated the stress distribution throughout the structure allowing it to withstand a greater load induced by the earthquake YRI but ultimately failed when the maximum earthquake loading was applied. Therefore it was recommended to provide a gap of 50mm on the end of the concrete slab to allow the structure to displace without increasing the stress in the structure. Finally, this study has proposed a design chart to showcase the failure mode of the bridge when subjected to seismic loading.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.3
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• pp.207-219
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• 2008

In urban areas, it is very often to excavate ground adjacent to existing structures for the construction of new buildings. Deformation and vibration induced by such construction activities may cause damages to the existing structures and petitions from citizens. To secure safety of the existing structures, particularly of tunnels, establishment of general guidelines on vibration have been crucial concerns, although some institutions have their own guidelines which are not generally accepted. This study aims establishing guidelines for tunnel safety due to blast-induced vibration. Numerical methods are adopted for this study. Blast load equation proposed by International Society of Explosive Engineers (2000) is used to decide detonation pressure. Analysis models were obtained from the construction cases of Seoul Metros. By performing dynamic numerical analysis, vibration velocity of an existing tunnel is evaluated. The numerical results are verified by comparing with the field measurement data obtained in excavation sites adjacent to an existing tunnel. Based on the results vibration safety zone is proposed. Influence circle for vibration velocity is drawn and the area not exceeding the allowable vibration velocity is established.