• Journal of Ocean Engineering and Technology
• /
• v.22 no.5
• /
• pp.142-147
• /
• 2008

The cases of using new methods of big blocks are largely increasing on Recent large-scale bridge structures. So the accurate data of responses of bridges following environmental causes are required to be quickly recorded in order to predict. For this reason described above, the research on measuring system should be conducted for more knowledge of the details on application and stability of new methods. In this study, the new health monitoring system that can monitor the real behavior and damages of the bridge during all processes of construction is presented by analyzing cases of domestic and overseas bridge health monitoring system, and applied methods of following bridges.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.16 no.1
• /
• pp.125-133
• /
• 2010

Researches and studies which have been conducted so far on external confinement of long span concrete columns have mainly concentrated on concentric loading. But, long span bridge concrete columns over the sea are mainly subjected to concentrated axial load, and at the same time lange amount of moment by eccentric load. This paper experimentally investigates the performance of externally confined high-strength concrete columns subjected to loading mechanism and evaluates the effectiveness of two confinement materials carbon fibre and high performance glass fibre. Twelve short columns with the same dimensions were cast and tested Six columns were reinforced with hoop bars, the remaining six columns were reinforced with spiral bars and wrapped with three layers of carbon failure and high performance glass FRP sheets. Test variables considered were the shape of internal reinforcement and strengthening materials according to loading location. The experimental results showed that eccentric load could obviously lower down the maximum failure load of FRP-confined concrete columns, compared with the columns under concentric load. And compared with the carbon FRP-confined reinforced concrete columns, high performance glass FRP-confined columns displayed a higher load capacity and ductility, when tested both concentrically and eccentrically.

• Journal of Ocean Engineering and Technology
• /
• v.23 no.3
• /
• pp.59-64
• /
• 2009

Bridge types such as the suspension bridges and the cable stayed bridges maintained by cables present the dangerous possibility of a ship running through the bottom of the bridge. Due to hangers and main cables in the upper structural system, the bridge is also susceptible to disasters. However, these cable bridges are usually used for long span bridges over the sea. This structure is relatively more exposed to disasters, such as wind, hail, and earthquake, than other structures. This structure also has the potential to cause car accidents on account of the poor visibility due to foggy conditions. If a fire breaks out because of a car accident due to wind, a car explosion will likely occur.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.2
• /
• pp.153-160
• /
• 2011

Recently there are many long span cable supported bridges like Cable Stayed Bridge and Suspension Bridge already constructed or planned. Reconsidering of proper design wind load of long span bridge is required since the meteorological value based on the data only from 1960s to 1995 has been used when we estimate the wind load for designing long span bridges. In this paper, the research area was confined to western and southern coasts where many long span bridges have constructed. The method of moment and the least-squares method were used to estimate the expected wind speeds of 100 year's return period for girder bridges and for 200 year's return period for long span bridges based on the Gumbel's distribution. As the return-period wind speed on the land face was revised because of recent high speed velocity, the revised return-period wind speed is increased by 17%. Compatibility of return-period wind speed was also evaluated using RMS (Root Mean Square) error method. Aa a result of this paper, the least-squares method is more compatible than the method of moment in the case of western and southern coasts in Korea.

• Proceeding of EDISON Challenge
• /
• 2014.03a
• /
• pp.631-636
• /
• 2014

본 연구는 전산 유체 해석 프로그램인 EDISON_CFD 해석 결과 산출 된 정적공기력계수(양력계수, 항력계수)를 이용하여 교량 단면의 갤로핑(Galloping)에 대한 안정성 평가를 실시하는데 그 목적이 있다. 특히 해상 교량은 장대 교량인데다 높은 풍속까지 견뎌 내야 하므로 내풍 안정성 검토의 중요성이 부각되고 있다. 전산 해석에 사용된 교량은 이순신 대교와 거가 대교의 표준 단면을 사용하였으며, 받음각과 풍속의 변화를 주어 높은 레이놀즈수 영역에서 공기력계수의 변화에 대해 검토하였다.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.7
• /
• pp.61-73
• /
• 2008

Piles of a bridge pier are connected with the column through the pile cap (footing). Behavior of the pile foundation can be different according to the connection method between piles and the pile cap. Connection methods between pile heads and the pile cap are divided into two groups : rigid connections and hinge connections. Domestic design code has been specified to use rigid connection method for the highway bridge. In the rigid connection method, maximum bending moment of a pile occurs at the pile head and this helps the pile to prevent the excessive displacement. Rigid methods are also good to improve the seismic performance. However, some specifications prescribe that conservative results through investigations of both the fixed-head condition and the free-head condition should be reflected in the design. This statement may induce an over-estimated design for the bridge which has high-quality structures with casing covered drilled shafts and the PC-house contained pile cap. Because the assumption of free-head conditions (hinge connections) is unreal for the elevated pile cap system with multiple piles of the long span sea-crossing bridges. On the other hand, elastic displacement method to evaluate the pile reactions under the pile cap is not suitable for this type of bridges due to impractical assumptions. So, full modeling techniques which analyze the superstructure and the substructure simultaneously should be performed. Loads and stress state of the large diameter drilled shaft and the pile cap for Incheon Bridge which will be the longest bridge of Korea were investigated through the full modeling for rigid connection conditions.

• 한국방재학회:학술대회논문집
• /
• 2011.02a
• /
• pp.86-86
• /
• 2011

토목 기술의 발달로 장대교량이 증가함에 따라 교면 포장도 더 심각한 진동 및 충격, 기상조건에 노출되게 된다. 교면 포장은 차량의 주행의 편리성뿐 아니라 교량 구조물을 보호해야 하는 역할도 함께 수행하기 때문에 일반 토공부의 포장과 다른 성능을 필요로 한다. 교면 포장의 특수함을 감안하여 교면 포장의 품질을 평가하고, 설계와 적용시 반영 한다면 교량의 내구 연한 및 시공, 유지관리 비용을 절감 할 수 있을 것이다. 본 논문에서는 교면 포장에 요구되는 성능을 조사하고, 교면 포장 특히, 장대 교량 적용시 교면 포장의 성능 평가를 위한 평가 방법을 고찰하였다. 교면 포장의 가장 큰 구조적 특징은 교량의 진동과 휨에 의해 포장이 받게 되는 휨응력이다. 특히 교량의 장경간화에 따라 더 큰 진동과 변형을 경험하게 되는 교면 포장은 그에 따른 충분한 휨 추종성과 피로 저항성을 확보하여야 한다. 기존 토공부 포장에서는 실험이 간단한 원통형 공시체를 이용한 간접인장강도 모드의 실험으로 피로 성능을 평가하였으나, 교면 포장은 실제 거동 특성과 유사한 빔 피로 시험 모드가 보다 신뢰성이 높을 것으로 판단된다. 빔 피로시험 모드로는 3점, 4점, 5점 휨 피로 시험 모드가 있으며, 각각의 모드는 지지점의 개수, 재하점의 개수에 따라 다른 거동 특성을 평가 할 수 있다. 최근 개발된 5점 휨 시험의 경우 교량에서 발생하는 부(-)모멘트를 모사할 수 있어 보다 현실적인 검증이 가능할 것으로 예상된다. 이 외에도 실제 크기 모형을 이용하여 윤하중을 가하는 Full-scale 모델의 경우 비용과 시간이 많이 소요되는 단점이 있으나 가장 신뢰성이 높은 방법이라고 할 수 있다. 교면 포장은 교량구조부로 수분이 침투되는 것을 막아주는 역할을 하여야 하며, 특히 해상 교량의 경우의 염분과 겨울철 사용되는 제빙화학제는 콘크리트의 열화와 강구조물의 부식을 발생시키므로 교면 포장의 방수 성능 검토는 매우 중요한 역할을 한다. 일반 토공부 포장과 달리 교면 포장은 하부층이 대기에 노출되어 있기 때문에 겨울철에 더 낮은 온도로 포장체의 온도가 내려가게 되고, 온도가 떨어진 포장층은 스티프니스가 증감함에 따라 저온 균열의 발생확율이 높아지며, 휨추종성도 나빠질 가능성이 높다. 따라서 저온에서의 균열 저항성 및 스티프니스를 평가하는 것은 교면 포장 재료의 중요한 인자 중 하나이다. 포장과 포장 하부층의 접착은 포장층의 일체화된 거동을 할 수 있게 하기 때문에 내구성 향상에 중요하다. 특히 교량과 같이 진동과 변형이 많은 경우에 있어 포장 접착층의 성능은 포장과 교량 구조물의 파손에 더 큰 영향을 미치게 된다. 접착성능은 실내에서의 직접인장모드와 전단접착강도 시험 모드의 실험이 있으며, 현장에서 측정하는 Pull-off 실험 등이 있다. 최근에 교통량과 중차량의 증가와 더불어 교량이 장경간화 되어 가면서 평가방법과 기준을 과거보다 엄격하게 할 필요성이 있다. 하지만 현실은 교면포장에 대한 시방규정이 모호하기 때문에 본 논문에서 제시한 국내외의 다양한 평가방법을 통해 적절한 교면포장의 성능을 평가하고 교면포장의 거동특성에 대한 이해를 함으로써 보다 발전된 교량기술을 확보할 수 있을 것이다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.1A
• /
• pp.1-10
• /
• 2012

Along with the development of coasts, islands and mountains, the demand of long-span bridges increases which, in turn, brings forth the construction of cable-supported bridges like suspension and cable-stayed bridges. There are various types of statically indeterminate structures widely applied that supported the main girder with stay cables, main cables, hanger cables with aesthetic structural appearance. As to the cable-supported bridges, the health monitoring of a bridge can be identified by measuring tension force on cable repeatedly. The tension force on cable is measured either by direct measurement of stress of cable using load cell or hydraulic jack, or by vibration method estimating tension force using cable shape and measured dynamic characteristics. In this study, a method to estimate dynamic characteristics of hanger cables by using a digital image processing is suggested. Digital images are acquired by a portable digital camcorder, which is the sensor to remotely measure dynamic responses considering convenient and economical aspects for use. A digital image correlation(DIC) technique is applied for digital image processing, and an image transform function(ITF) to correct the geometric distortion induced from the deformed images is used to estimate subpixel. And, the correction of motion of vision-based measurement system using a fixed object in an image without installing additional sensor can be enhanced the resolution of dynamic responses and modal frequencies of hanger cables.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5C
• /
• pp.323-331
• /
• 2006

It is a recent worldwide trend that erosion characteristics of soil, the resistance factor against scour, are quantified and considered in the estimation of scour depths in fine-grained soils. As part of the efforts, local erosion characteristics on fine-grained soils of the West Coast area are analyzed through scour rate experiments, where a lot of sea-crossing long-span bridges are planned and being constructed in recent years. Four sites including Incheon Bridge, Choji Bridge, Hwankyung Bridge, and Janghang area are finally selected for this study and the scour rate tests are performed using 34 undisturbed soil samples from the sites. The critical shear stresses which represent erodibility of the soil tend to be proportional to the undrained shear strength values. The relative ability of cohesive fine-grained soils to resist erosion is assumed to be higher than that of noncohesive soils. Quantified local erosion characteristics of fine-grained soils in the West Coast area are presented in forms of charts showing relationships between scour rates and shear stresses, and suggested as basic data for the estimation of scour depths and design of bridge foundations in the West Coast area.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.5
• /
• pp.609-616
• /
• 2008

Recently, many ocean bridges that connect land to island or island to island have been constructed along with the improvement of the nation's economy. Long-span bridges can be categorized as suspension bridge, cable-stayed bridge, arch bridge and truss bridge. In this study, correction with respect to construction error can be presented on site through the monitoring of the cable tension change of real structure for four major construction stages so that construction accuracy, including the management of profiles, can be improved. A vibration method, the so-called indirect method that uses the cable's natural frequency changes from the acceleration sensor installed on the cable, is applied in measuring cable tension. In this study, the estimation formula for the effective length of cable with damper is presented by comparing and analyzing between actual measurement and analysis result for the change of the cable's effective length. By the way, it is known that the reliability of estimating cable tension by applying the former method that uses the net distance from damper to anchorage is low. Therefore, for future reference of the maintenance stage, the presented formula for estimating the effective length of cable can be used as a reference for the rational decision-making, such as the re-tensioning and replacement of cable.