• Computers and Concrete
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• 제32권4호
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• pp.411-423
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• 2023

The rapid development of road transport has increased the number of bridges that require widening. A critical issue in the construction of bridge widening is the influence of vibrations of the old bridge on the casting of wet joint concrete between the old and new bridges owing to the running traffic. Typically, the bridge is closed to traffic during the pouring of wet joint concrete, which negatively affects the existing transportation network. In this study, a newly developed microscopic traffic load modeling approach and the vehicle-bridge interaction theory are incorporated to develop a refined numerical framework for the analysis of random traffic-bridge coupled dynamics. This framework was used to investigate traffic-induced vibrations at the wet joint of a widened bridge. Based on an experimental study on the vibration resistance of wet joint concrete, traffic control strategies were proposed to ensure the construction performance of cast-in-site wet joint concrete under random traffic without interruption. The results show that the vibration displacement and frequency of the old bridge, estimated by the proposed framework, were comparable with those obtained from field measurements. Based on the target peak particle velocity and vibration amplitude of the wet joint concrete, it was found that traffic control measures, such as limiting vehicle gross weight and limiting traffic volume by closing an additional traffic lane, could ensure the construction performance of the wet joint concrete.

• Advances in concrete construction
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• 제3권4호
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• pp.295-316
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• 2015

A bridge widening technology using steel-concrete composite system was developed and is presented in this paper. The widened superstructure system consists of a newly built composite steel-concrete girder with concrete deck and steel diaphragms attached to the existing concrete girders. This method has been applied in several bridge widening projects in China, and one of those projects is presented in detail. Due to the higher stiffness-to-weight ratio and the rapid erection of composite girders, this widening method reveals benefits in both mechanical performance and construction. As only a few methods for the design of bridges with different types of girders are recommended in current design codes, a more accurate analytical method of estimating live load distribution on girder bridges was developed. In the analytical model, the effects of span length, girder pacing, diaphragms, concrete decks were considered, as well as the torsional and flexural stiffness of both composite box girders and concrete T girders. The study shows that the AASHTO LRFD specification procedures and the analytical models proposed in this paper closely approximate the live load distribution factors determined by finite element analysis. A parametric study was also conducted using the finite element method to evaluate the potential load carrying capacities of the existing concrete girders after widening.

• Computers and Concrete
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• 제23권5호
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• pp.329-334
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• 2019

Traffic flow capacity of some old road bridges is insufficient due to limited deck width. In such cases bridge deck widening is a common solution. For multi-girder reinforced concrete (RC) bridges it is possible to add steel-concrete composite girders as the new outermost girders. The deck widening may be combined with bridge strengthening thanks to thickening of the existing deck slab. Joint action of the existing and the added parts of such bridge span must be ensured. It refers especially to the horizontal plane at the interface of the existing slab and the added concrete layer as well as to the vertical planes at the external surfaces of the initially outermost girders where the added girders are connected to the existing bridge span. Since the distribution of the added concrete is non-uniform in the span cross-section the structure is particularly sensitive to the added concrete shrinkage. The shrinkage induces shear forces in the aforementioned planes. Widening of a 12 m long RC multi-girder bridge span is numerically analysed to assess the influence of the added concrete shrinkage. The analysis results show that: a) in the vertical plane of the connection of the added and the existing deck slab the longitudinal shear due to the shrinkage of the added concrete is comparable with the effect of live load, b) it is necessary to provide appropriate longitudinal reinforcement in the deck slab over the added girders due to tension induced by the shrinkage of the added concrete.

• 한국구조물진단유지관리공학회 논문집
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• 제12권4호
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• pp.187-194
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• 2008

도로교량의 경우 급속한 도시화로 인해 증가한 교통량을 처리하기 위해 교량확폭과 신설교량의 추가 건설 등의 방법이 사용되고 있다. 하지만 현재 국내에서는 확폭 또는 신설 교량의 추가건설의 타당성을 판단하기 위한 합리적인 절차나 기준이 마련되어 있지 않다. 또한 교량 확폭 공사 시에는 일반적인 교량신설 공사에 비해 불확실성을 내포한 사건들이 추가적으로 존재한다. 이에 본 논문에서는 의사결정수 방법을 이용해 교량확장에 따라 발생 가능한 사건의 기대 위험비용을 체계적으로 고려할 수 있는 개선된 형태의 생애주기비용 분석 모델을 제안하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.163-170
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• 1994

The widening of bridges under traffic condition brings to many problems. One of these is the internal stresses caused by different creep and shrinkage behavior of the existing bridge and that of the widened Bridge. This study was conducted to examine the effects of different creep and shrinkage behaviors between concretes. The results are as follows; Comparing the computational analysis results with the experimental study, it is shown that finite element analysis used in this study was well accorded with experimental results. And considering the shrinkage effects in widened bridges, joining-construction using the expanding concrete between the existing and widened bridge after at least three months from the day of completion of new bridge, is recommended.

• 대한치과보철학회지
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• 제9권1호
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• pp.17-22
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• 1969

Intra-oral films of 155 patients were taken on the areas of Gold Crown-Bridges, S. P. Bridges and Partial Dentures. And the author observed periodontal ligaments widening rates, the presence of periapical lesions and the alveolar bone patterns on the Partial Denture Saddle portions. The results were as follows : 1. Periodontal ligaments a) Periodontal ligaments widening rate increased obviously with the duration of wearing those prosthetic appliances. b) Periodontal ligaments widening rate was the highest in partial denture wearing patients, and then that of S. P. Crown Bridge patients, Gold Crown Bridge wearing females, Gold Crown Bridge males were the sequences. 2. Periapical lesions a) Periapical lesions increased with the wearing duration of those prosthetic appliances. But they did not increase in proportion to the duration. Periapical lesions were about the same in the teeth with those appliances showing relatively higher rate in Partial Denture abutment teeth and the lowest in Gold-Bridge abutment teeth. 3. Alveolar bone of Partial Denture saddle portion One third of all(32%) were normal with their smooth and compact bone pattern so that they were considered to perform normal function.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 봄 학술발표회 논문집
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• pp.188-193
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• 1993

In widening of existing bridges, construction joints between old new parts of concrete slabs are subjected to repeated traffic loads during placing and curing of concrete. Therefore, the main focus of this paper is given to examine several construction methods of bridge widening. As a result, the occurrence of cracks in vibrating specimen is faster than non-vibrating one, but the difference between flexural strength and ultimate moment was negligible. Also, it shows the same result in other construction method, say direct and non-shrinkage joint specimen.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 봄 학술발표회 논문집
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• pp.13-18
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• 1994

Most widened bridges have been constructed by the joining-construction method that makes new and existing bridge structurally single structure. However, joing-construction method has several problems in design and construction viewpoint. Therefore, this study is conducted in order to investigate structural behavior of widened RC slab and traffic-induced vibration of existing bridge during placing and curing of new concrete by the prototype flexural fatigue test. From the results of this study, it is shown that stress-concentration and slip occur between concrete and reinforcing rod at joint section but the reduction of load carrying capacity and of fatigue strength is negligible according to the traffic-induced vibration as well as the difference of construction method. A reasonable construction method for the bridge widening which takes into account the effects of the traffic-induced vibration and S-N curve for the widened bridge are also proposed.

• 콘크리트학회지
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• 제25권5호
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• pp.29-33
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• 2013

• 치과방사선
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• 제8권1호
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• pp.5-9
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• 1978

The purpose of this study is to investigate the effect of dental restorations on the periodontal and periapical tissues. The author examined 620 cases of amalgam, 390 cases of gold inlay, 422 cases of crown and 644 cases of bridge through the standard intraoral films being appended in the charts that had been kept at the Dept. of Oral Diagnosis in Seoul National University Hospital. This study obtained the following results; 1. The restorations of amalgam, gold inlay crown and bridge were found more frequently in female than in male. 2. The restorations of amalgam, gold inlay and crown were found more numerously in mandibular teeth than in maxillary teeth in both sexes. But in the case of crown, the fact is quite the reverse especially in anterior teeth. 3. On the contrary, in the case of bridge, the restorations of bridge were much more distributed in the maxillary teeth than in the mandibular teeth. 4. Roentgenographic changes of periodontal tissues whose teeth were treated with any type of four restorations were periodontal space widening, lamina dura discontinuity and periapical lesion in the order described in both sexes. 5. On the occasion of between amalgam and gold inlay or between crown and bridge, the differences of periodontal changes were of no consequence. On the other hand, the differences of periodontal changes were apparant between the group of amalgam & gold inlay and the group of crown & bridge.