• Magazine of the Korea Concrete Institute
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• 제10권4호
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• pp.145-151
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• 1998

The vertical tensile stress, ${\sigma}_y$, in the contact zone between the overlay (mortar layer) and substratum (base concrete) can be the main cause of the failure phenomenon of overlaid concrete structures. The development of tensile stress, ${\sigma}_y$, due to external rainy condition was analytically investigated using finite element method. Rainfall intensity $(n_R\;=\;1/a,\;t_R\;=\;10min,\;60min)$, thickness of overlay (do=1,2,4,10 cm) and overlay material (CM,ECM,EM) were the main variables in the analyses. An equation was suggested with which the development of vertical tensile stress, ${\sigma}_y$, in the rainy condition could be determined. Using this equation, it is possible to select proper material properties and overlay thicknesses to prevent failure in the contact zone due to thermally transient condition caused by rainfall.

• The Journal of Korean Academy of Prosthodontics
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• 제29권2호
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• pp.147-160
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• 1991

The purpose of this study was to examine, by the method of finite element analysis, how implant geometry with or without connection between natural tooth and osseointegrated abutments affected the stress distribution in surrounding bone and osseointegrated prosthesis. The mandibular first and second molars were removed and the two osseointegrated implants were placed in the first and second molar sites. Stress analysis induced by prostheses with connection(Model A)or without connection(Model B) between natural tooth(second bicuspid) and two osseointegrated abutments(first molar and second molar) was performed under vertical point load(Load P1) or distributed point load(Load P2). The results were as follows; 1. Under vertical point load, mesial tilting was shown in both Model A and Model B and inferior displacement of Model A was greater than that of Model B in the second bicuspid. 2. Under vortical point load, the first and second molars showed mesial tilting in both Model A and Model B, and inferior displacement of them was similar in Model A and Model B and was less than that of the second bicuspid. 3. Under distributed point load, mesial displacement was shown in Model A and Model B and inferior displacement of Model A was less than that of Model B in the second bicuspid. 4. Under distributed point load, mesial tilting was shown and inferior displacement of Model A was similar to that of Model B in the first and second molars. 5. In Model A under vertical point load, high stress was concentrated in the corneal portion of first molar and distributed throughout the second molar and the second bicuspid, and the stress distribution of the second molar was greater than that of the second bicuspid. 6. In Model B under vertical point load, high stress was concentrated in the coronal and mesio-cervical portion of the first molar. 7. In Model A under distributed point load, high stress was concentrated in the mesio-cervical portion of the first molar and evenly distributed throughout the second molar and the second bicuspid. 8. In Model B under distributed point load, high stress was concentrated in the disto-cervical portion of the second bicuspid and evenly distributed throughout the first and second molars.

• Journal of the Korean Society of Safety
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• 제31권2호
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• pp.64-69
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• 2016

In this paper, structural analysis of High-Speed railway vertical tunnel structures was performed to verify the structural stability. The corrugated steel plate method was applied to the vertical tunnel structures for its simple construction method and low cost. The structural stability of Wall, Connection and Storage section was performed with LRFD and ASD design method at joint part, buckling, stress and plastic hinge. From the results, all of vertical tunnel structures shown the structural stability regardless of design method and structure types. So, the application of corrugated steel plate in vertical tunnel structures instead of cast-in-placed concrete was quite enough.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.587-598
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• 2008

In the trackbed design using elastic multi-layer model, the stress-dependent resilient modulus is an important input parameter, which reflects substructure performance under repeated traffic loading. The resilient moduli of crushed stone and weathered granite soil were developed using nonlinear dynamic stiffness, which can be measured by in-situ and laboratory seismic tests. The prediction models of resilient modulus varying with the deviatoric or bulk stress were proposed (Park et al., 2008). To investigate the performance of the prediction models proposed herein, the elastic response of the test trackbed near PyeongTaek, Korea was evaluated using a 3-D nonlinear elastic computer program (GEOTRACK) and compared with measured elastic vertical displacement during the passages of freight and passenger trains. The material types of the test sub-ballasts are crushed stone and weathered granite soil, respectively. The calculated vertical displacements within the sub-ballasts are within the order of 1mm, and agree well with measured values with the reasonable margin. The prediction models are thus concluded to work properly in the preliminary investigation. The prediction models proposed for resilient modulus were verified by the comparison of the calculated vertical displacements with measured ones during train passages.

• The Journal of Korean Academy of Prosthodontics
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• 제29권2호
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• pp.103-115
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• 1991

This study was executed to analyze the stress distribution of tooth, supporting structure and overdenture by two-dimensional photoelastics when 6 types of coping were inserted. Types of coping were designed to be inclined plane, short dome, medium dome, shore square, medium square and o-p anchor attachment. Fortes were applied respectively as follows: 1) Vertical load of 10 kg on the incisal edge 2) $30^{\circ}$ diagonal load of 8 kg on the labial surface. The results were as follows: 1. In case of short dome and o-p anchor attachment, the stress is evenly distributed on teeth, supporting tissue structure under vertical and $30^{\circ}$ diagonal load, then short dome and o-p anchor attachment show better stress distribution and stabilization of overdenture than any other coping under labial diagonal load. 2. Inclined plane revealed greater tendency of displacement of overdenture than any other coping under labial diagonal load. 3. Long height of copings had greater concentration of stress than short height of copings. 4. In case of medium dome under labial diagonal load, there were high level of stress concentration on denture base contacted labioincisal angle of coping.

• Restorative Dentistry and Endodontics
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• 제44권2호
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• pp.15.1-15.8
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• 2019

Objectives: The aim of this study was to investigate whether the diameter and direction of the plunger and simulation of the periodontal ligament (PDL) affected the stress distribution in endodontically treated premolars. Methods: A fracture strength test was simulated via finite element analysis. A base model was set up, and the following parameters were modified: plunger diameter (3 mm vs. 6 mm), plunger direction (vertical vs. $135^{\circ}$ angular to the central fossa), and PDL simulation. The analysis was conducted using the CosmosWorks structural analysis program, and the results are presented in terms of von Mises stresses. Results: The smaller plunger increased the stresses at the contact area of the crown, but the plunger diameter had no effect on the stress distribution within the root. An angular plunger direction increased stresses within the root, as well as at the buccal cusp of the crown, compared with the vertical direction. Simulation of the PDL caused higher stress accumulation, especially in the cervical region of the root. Conclusions: The plunger diameter had no effect on the stress distribution in the roots, whereas the plunger direction and PDL simulation did affect the stress distribution. More stringent standards can be established by taking such parameters into account when performing fracture testing in future studies.

• The Journal of Korean Academy of Prosthodontics
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• 제44권2호
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• pp.207-216
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• 2006

Statement of Problem: To conduct a successful function of implant prosthesis in oral cavity for a long time, it is important that not only structure materials must have the biocompatibility, but also the prosthesis must be designed for the stress, which is occurred in occlusion, to scatter adequately within the limitation of alveolar bone around implant and bio-capacity of load support. Now implant which is used in clinical part has a very various shapes, recently the fixture that has tapered form of internal connection is often selected. However the stress analysis of fixtures still requires more studies. Purpose: The purpose of this study is to stress analysis of the implant prosthesis according to the different implant systems using finite element method. Material and methods: This study we make the finite element models that three type implant fixture ; $Br{\aa}nemark$, Camlog, Frialit-2 were placed in the area of mandibular first premolar and prosthesis fabricated, which we compared with stress distribution using the finite element analysis under two loading condition. Conclusion: The conclusions were as follows: 1. In all implant system, oblique loading of maximum Von mises stress of implant, alveolar bone and crown is higher than vertical loading of those. 2. Regardless of loading conditions and the type of system. cortical bone which contacts with implant fixture top area has high stress, and cancellous bone has a little stress. 3. Under the vertical loading, maximum Von mises stress of $Br{\aa}nemark$ system with external connection type and tapered form is lower than Camlog and Frialit-2 system with internal connection type and tapered form, but under oblique loading Camlog and Frialit-2 system is lower than $Br{\aa}nemark$ system.

• The Journal of Korean Academy of Prosthodontics
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• 제31권3호
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• pp.303-316
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• 1993

The purpose of this study was to analysis the stress distribution induced by three unit PFM bridges and various cantilever bridges replacing maxillary latersal incisor. The simplified two-dimensional photoelastic models used for this study was contructed in the folio- wing way. CR/R ratio was designed to be 1 : 1, 1 : 1.25 and 1 : 1.5. The pontics of cantilever bridge supported by maxillary canines consisted of wrap-around type, rest-extension type, and simple type. 3-unit PFM bridge was constructed with traditional method. 1kg vertical static load was applied on the center of the incisal edge of the pontic. The stress pattern was examined and recorded by photography. The results obtained were as follows ; 1. The magnitude of stress on the abutment root apex area of a traditional 3-unit bridge was the lowest. 2. The model of cantilevered pontic with a rest showed the relatively well distributed stress around the abutment tooth. The model with simple pontic generated the greatest stress concentration in the supporting structure of the abutment tooth. 3. As the height of bone level reduced, the rotational and vertical force increased around the abutment tooth. 4. The stress concentration of the 3-unit bridges occured on the root apex and stress concentration of the cantilever briage occured on the root apex and cervix area, 5. In the case of the cantilever bridge, stress concentrated distally on the root apex area of the abutment tooth and additional stress was observed mesially on the upper part of the root. Especially in the case of the simple pontic, was phenomenon was more apparent than the others. 6. Force applied to cantilevered pontic was transmitted to the adjacent central incisor through the contact surface. Stress was markedly observed on the mesial cervix area in the case of simple pontic and on the root apex area in the case of wrap-around type and rest-extension type.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제30권4호
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• pp.331-338
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• 2004

Stress transfer to the surrounding tissues is one of the factors involved in the design of dental implants. Unfortunately, insufficient data are available for stress transfer within the regenerated bone surrounding dental implants. The purpose of this study was to investigate the concentration of stresses within the regenerated bone surrounding the implant using three-dimensional finite element stress analysis method. Stress magnitude and contours within the regenerated bone were calculated. The $3.75{\times}10-mm$ implant (3i, USA) was used for this study and was assumed to be 100% osseointegrated, and was placed in mandibular bone and restored with a cast gold crown. Using ANSYS software revision 6.0, a program was written to generate a model simulating a cylindrical block section of the mandible 20 mm in height and 10 mm in diameter. The present study used a fine grid model incorporating elements between 165,148 and 253,604 and nodal points between 31,616 and 48,877. This study was simulated loads of 200N at the central fossa (A), at the outside point of the central fossa with resin filling into screw hole (B), and at the buccal cusp (C), in a vertical and $30^{\circ}$ lateral loading, respectively. The results were as follows; 1. In case the regenerated bone (bone quality type IV) was surrounded by bone quality type I and II, stresses were increased from loading point A to C in vertical loading. And stresses according to the depth of regenerated bone were distributed along the implant evenly in loading point A, concentrated on the top of the cylindrical collar loading point B and C in vertical loading. And, In case the regenerated bone (bone quality type IV) was surrounded by bone quality type III, stresses were increase from loading point A to C in vertical loading. And stresses according to the depth of regenerated bone were distributed along the implant evenly in loading point A, B and C in vertical loading. 2. In case the regenerated bone (bone quality type IV) was surrounded by bone quality type I and II, stresses were decreased from loading point A to C in lateral loading. Stresses according to the depth of regenerated bone were concentrated on the top of the cylindrical collar in loading point A and B, distributed along the implant evenly in loading point C in lateral loading. And, In case the regenerated bone (bone quality type IV) was surrounded by bone quality type III, stresses were decreased from loading point A to C in lateral loading. And stresses according to the depth of regenerated bone were distributed along the implant evenly in loading point A, B and C in lateral loading. In summary, these data indicate that both bone quality surrounding the regenerated bone adjacent to implant fixture and load direction applied on the prosthesis could influence concentration of stress within the regenerated bone surrounding the cylindrical type implant fixture.

• Journal of the Korean Geotechnical Society
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• 제24권2호
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• pp.87-97
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• 2008

Behaviors of cemented engineered soils, composed of rigid sand particle and soft rubber particle, are investigated under $K_o$ condition. The uncemented and cemented specimens are prepared with various sand volume fractions to estimate the effect of the cementation in mixtures. The vertical deformation and elastic wave velocities with vertical stress are measured. The bender elements and PZT sensors are used to measure elastic wave velocities. After cementation, the slope of vertical strain shows bilinear and is similar to that of uncemented specimen after decementation. Normalized vertical strains can be divided into capillary force, cementation, and decementation region. The first deflection of the shear wave in near field matches the first arrival of the primary wave. The elastic wave velocities dramatically increase due to cementation hardening under the fixed vertical stress, and are almost identical with additional stress. After decementation, the elastic wave velocities increase with increase in the vertical stress. The effect of cementation hinders the typical rubber-like, sand-like, and transition behaviors observed in uncemented specimens. Different mechanism can be expected in decementation of the rigid-soft particle mixtures due to the sand fraction. a shape change of individual particles in low sand fraction specimens; a fabric change between particles in high sand fraction specimens. This study suggests that behaviors of cemented engineered soils, composed of rigid-soft particles, are distinguished due to the cementation and decementation from those of uncemented specimens.