• 대한치과보철학회지
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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.

• 대한치과보철학회지
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• 제39권3호
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• pp.313-318
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• 2001

Masticatory function is more important than esthetics in posterior fixed restoration. The usual technique-mounting the casts on a semi-adjustable articulator, etc. -cannot make all patients satisfied with their restorations. For example, functionally generated path technique can be an easier and more satisfactory method in the restoration of group function. These clinical reports describe various approaches for occlusal restoration of relatively simple posterior fixed protheses according to patients occlusal patterns. The 3-unit bridge restoration is one of the most popular treatment options in prosthodontics. Because dentists have much experiences of it, they restore a missing span of one tooth mechanically, that is, without special consideration. While esthetics is important in making an anterior 3-unit fixed prostheses, mastication is more focused on in posterior 3-unit bridge restoration. Many dentists are concerned about various aspects in esthetics, such as morphology of the tooth, value, chroma, hue, translucency, surface texture, etc. But they do not usually consider various methods to restore occlusion. They treat one-tooth-missing area in a similar way in spite of patients having variety of occlusal patterns. Three cases are presented here in 3 or 4-unit bridge restoration. They show some methods to restore patients' occlusal patterns.

• The Journal of Advanced Prosthodontics
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• 제14권4호
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• pp.223-235
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• 2022

PURPOSE. To compare the clinical outcomes of two types of implant restoration for posterior edentulous area, 3-unit bridge supported by 2 implants and 3 implant-supported splinted crowns. MATERIALS AND METHODS. The data included 127 implant-supported fixed restorations in 85 patients: 37 restorations of 3-unit bridge supported by 2 implants (2-IB), 37 restorations of 3 implant-supported splinted crowns (3-IC), and 53 single restorations (S) as controls. Peri-implantitis and mechanical complications that occurred for 14 years were analyzed by multivariable Cox regression model. Kaplan-Meier curves and the multivariable Cox regression model were used to analyze the success and survival of implants. RESULTS. Peri-implantitis occurred in 28.4% of 2-IB group, 37.8% of 3-IC group, and 28.3% of S control group with no significant difference. According to the implant position, middle implants (P2) of the 3-IC group had the highest risk of peri-implantitis. The 3-IC group showed a lower mechanical complication rate (7.2%) than the 2-IB (16.2%) and S control group (20.8%). The cumulative success rate was 52.8% in S (control) group, 62.2% in 2-IB group, and 60.4% in 3-IC group. The cumulative survival rate was 98.1% in S (control) group, 98.6% in 2-IB group, and 95.5% in 3-IC group. There was no significant difference in the success and survival rate according to the restoration type. CONCLUSION. The restoration type was not associated with the success and survival of implants. The risk of mechanical complications was reduced in 3 implant-supported splinted crowns. However, the middle implants of the 3 implant-supported splinted crowns had a higher risk of peri-implantitis.

• Interaction and multiscale mechanics
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• 제3권4호
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• pp.321-331
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• 2010

A new technique is proposed for bridge structural damage detection based on spatial wavelet analysis of the time history obtained from vehicle body moving over the bridge, which is different from traditional detection techniques based on the bridge response. A simply-supported Bernoulli-Euler beam subjected to a moving spring-mass unit is established, with the crack in the beam simulated by modeling the cracked section as a rotational spring connecting two undamaged beam segments, and the equations of motion for the system is derived. By using the transfer matrix method, the natural frequencies and mode shapes of the cracked beam are determined. The responses of the beam and the moving spring-mass unit are obtained by modal decomposition theory. The continuous wavelet transform is calculated on the displacement time histories of the sprung-mass. The case study result shows that the damage location can be accurately determined and the method is effective.

• 대한치과보철학회지
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• 제40권5호
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• pp.429-440
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• 2002

Current dental restorations present a relatively weak resistance to fracture. Owing to their unique mechanical properties, fibre-reinforced polymers are now being considered. Unidirectional or woven continuous fibres, made of glass, polyethylene, carbon or Kevlar, have been evaluated. This study focused on the use of glass fibre knitted fabrics to reinforce acrylate resins, in order to investigate the possibility to construct single crowns as well as three unit bridges. Some points affecting the final composite system were tested ; 1) static strength, with focus on the stress transfer under a occlusal contact point ; 2) modelling of a three nit bridge ; 3) fatigue strength as a posterior three unit bridge material. The study demonstrated that knitted fabric reinforcements are showing an interesting compromise between stiffness, static strength for single crown. For three unit bridge applications in the posterior arch, however knitted glass fabric reinforcements were not strong enough in fatigue An additional reinforcement in the posterior arch fixed partial denture design was recommended.

• 한국구조물진단유지관리공학회 논문집
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• 제15권3호
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• pp.163-170
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• 2011

본 연구에서 교량바닥판용으로 조립식(Modular) 유리섬유 보강(GFRP) 바닥판의 개념을 제안하였다. 본 조립식 GFRP 바닥판시스템은 GFRP 주 단위모률(unite module)과 연결 단위모듈로 구성되어 있다. 본 GFRP 바닥판의 구조성능을 평가하기 위해 정적하중실험을 실시하였다. 그리고 구조성능 결과에 대해서 범용 유한요소 프로그램인 LUSAS을 이용한 수치해석 결과와 비교 분석하였다. 본 연구에서 제안한 조립식 GFRP 바닥판은 교량적용에 매우 유용할 수 있음을 확인할 수 있었다. 제안된 GFRP 바닥판의 파괴모드가 개발된 다른 상용화된 GFRP 바닥판의 파괴모드와 매우 유사한 파괴모들 나타내었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.354-361
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• 2002

This paper propose section properties factor to generate stress history for fatigue analysis and safety inspection of steel bridge. A methodology is described for the computation of numerical stress histories in the steel truss bridge, caused by the vehicles using section properties factor. The global 3-D beam model of bridge is combined with the local shell model of selected details. Joint geometry is introduced by the local shell model. The global beam model takes the effects of joint rigidity and interaction of structural elements into account. Connection nodes in the global beam model correspond to the end cross-section centroids of the local shell model. Their displacements are interpreted as imposed deformations on the local shell model. The load cases fur the global model simulate the vertical unit force along the stringers. The load cases fer the local model are imposed unit deformations. Combining these, and applying vehicle loads, numerical stress histories are obtained. The method is illustrated by test load results of an existing bridge.

• 한국지반공학회논문집
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• 제28권10호
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• pp.55-68
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• 2012

우리나라 조간대의 약 83%는 서해안에 분포하고 있으며, 경기도와 인천지역에 약 35.1%가 분포하고 있다. 본 연구는 경기만 일원에 분포하는 조간대 퇴적층의 형성 환경과 특성을 이해하기 위하여 수행되었으며, 광물학적, 지구화학적, 물리적 특성에 대한 관찰과 기술을 통해 각각의 세부적인 퇴적단위를 구분하였다. 우리나라 서해 연안 조간대에서 채취된 퇴적물의 층서적 위치, 퇴적상 및 침식 부정합면을 근거로 조간대는 기반암 상위로부터 Unit 4${\rightarrow}$Unit 3${\rightarrow}$Unit 2${\rightarrow}$Unit 1의 순서로 4개의 퇴적단위로 구분되며, 경기만에서 측정된 퇴적층을 서해안 조간대 퇴적층과 대비하면 북부지역에 해당되는 청라지구에서는 Unit 4, Unit 3, Unit 2, Unit 1의 모든 지층이 나타나며, 영종도지역에서는 Unit 2, Unit 1의 지층이 관찰되며, Unit 4, Unit 3은 결층이다. 경기만의 중부와 남부지역에 해당되는 인천대교와 송도지역은 Unit 4, Unit 3, Unit 1의 지층이 관찰되며, Unit 2는 결층에 해당한다. 가로림만에 해당되는 대산 지역은 Unit 4-Unit 3-Unit 1이 관찰된다. 상부 지층에 해당하는 Unit 1과 Unit 2 지층은 경기만 북부의 청라지구와 영종도 지역에서 넓게 분포하며, 남부 지역은 하부 지층의 Unit 3과 Unit 4 지층이 잘 나타난다. 경기만에서 측정된 평균 점토광물 함량비는 청라지구에서 8.2%, 영종도에서 2.9%, 인천대교에서 18.4%, 송도지역에서 24.6%로 나타났다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1046-1051
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• 2004

As a method to execute efficient maintenance of steel railway bridge, in this paper, program for fatigue assessments of structural member of steel railway bridge were developed. This program is composed with 3 unit module program which variable stress analysis, fatigue assessment and fatigue crack propagation. The validity of developed program was verified from evaluating the result of filed measurement and program output.

• 대한치과보철학회:학술대회논문집
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• 대한치과보철학회 1994년도 춘계학술대회
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• pp.18-18
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• 1994