• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.333-338
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• 2007

An infernally confined hollow reinforced concrete pier (ICH RC pier) is hollow RC pier which has a internal steel tube to enhance its ductility and stiffness by internal confinement. In this study, the internal steel tube were changed to investigate the behavior of ICH RC pier. The behavior of internally confined hollow reinforced concrete piers were evaluated with safety ratio, ductility, total material cost, the total weight of the pier, etc. As a result of analytical study, the usage of a minimum necessary thickness of the internal steel tube the most effective. The ICH RC pier has decrease of weight compare to Solid RC pier.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1669-1674
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• 2008

여수로는 방류량 월류시 한계류 상태와 고유속의 사류상태가 복합적으로 일어나는 흐름형태를 가지고 있어 여수로의 방류능력에 대한 평가시 수치해석 및 수리모형 실험을 통해 검증하고 있다. 여수로의 방류능력은 여수로 월류부 전면부 바닥고, 월류부 상 하류 경사, 월류웨어고 뿐만 아니라 교대 및 교각의 형상에 의해 영향을 받는다. 또한 월류웨어부를 지나 사류의 흐름양상을 보이는 천이부의 형상 및 후면 교각의 연장에 따라서도 급경사수로부의 흐름이 급변하게 된다. 국내 대부분의 여수로는 전면부의 교각(Pier)형상이 구조적인 안정성을 이유로 직벽형 설계방법을 일반적으로 채택하고 있으며 국내 및 미개척국(USBR)의 설계기준 또한 여수로 교각과 교대부의 평면 형상만을 고려할 수 있도록 제시하고 있어 국내 대부분의 수리 구조물들이 획일적인 구조물 형상을 벗어나지 못하고 있는 실정이다. 본 연구에서는 수치 및 수리모형 실험을 통해 국내 대댐에 설계되어 있는 직벽형태와 본 연구에서 제시하고 있는 켄틸러버형의 교각형상에 따른 여수로의 수리적 흐름양상 및 방류능력을 비교하여 그 효과를 검토하였다. 검토결과 켄틸러버형태의 교각이 설치된 여수로의 경우 직벽형에 비하여 전면부 수위상승 및 흐름교란이 적게 발생하였으며, 방류능력 또한 개선되는 결과를 나타내었고, 후면 교각의 연장이 길고 점차 축소될수록 급경사수로부의 흐름이 안정적인 것으로 나타났다.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.3
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• pp.215-222
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• 2015

The purpose of this study was to investigate abdominal local muscle activity during modified bridge exercise. 17 subjects participated in this study. Abdominal muscles measured. External oblique abdominis (EO), internal oblique abdominis (IO), transvers abdominis (TrA), and rectus abdominis (RA) during general bridge exercise and modified bridge exercise, respectively. Electromyogram (EMG) and real-time ultrasound were used to verify alteration of muscles. Activation of RA and EO muscles of non-dominant foot was significantly difference in general bridge exercise group, not modifiedl bridge exercise group. In the modified bridge exercise group, thickness of IO and TrA muscle of non-dominant foot was significantly difference in modified bridge exercise group than general bridge exercise group. Therefore, modified bridge exercise may be apply as more effective exercise for local muscle activity than global muscle.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.221-224
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• 2008

Recently various types of prefabricated pier has been developed. In this paper, prefabricated composite columns with core steel elements embedded in concrete were proposed, which has no prestressing. Based on the previous research on composite columns with low steel ratio, the column were designed. A simple bolt connection detail between a footing and a pier element were also suggested. In order to investigate the seismic performance of the composite columns, several tests on concrete encased composite columns, which are prefabricated, were performed. Quasi-static tests were carried out and their performance was evaluated and compared with the results from the tests on CIP composite piers. In the case of precast piers, the end part of the pier needs to be carefully reinforced and related recommendations on details were derived.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.189-193
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• 2010

RMA-2, Telemac-2D, River2D 등 기존의 대부분 국내외 상용모형에서는 내부 경계인 하천구조물과 외부 경계인 측벽에서의 경계조건을 활동조건(slip condition)으로 가정하여 흐름장을 계산하였다. 그러나 실제로 벽면에서는 마찰력에 의해 흐름이 존재하지 않는 무활조건(no slip condition)이 물리적으로 타당하다. 따라서 본 연구에서는 내부구조물인 교각이 존재하는 영역에서의 수평 2차원 유속분포를 구하기 위해 천수방정식을 Galerkin법과 Newton-Raphson법에 의해 이산화한 수치모형을 개발하였다. Yulistiyanto 등(1998)이 수치모의 및 수리실험에 사용한 조건을 채택하여 벽면에서의 접선방향 유속이 존재하는 활동조건과 벽면에서 유속이 없는 무활조건을 부여하고 교각을 포함한 수로에서 유속, 수위 및 전단분포를 해석하였다. 활동경계조건을 적용한 경우 교각 표면을 따라 큰 유속이 분포하고 후면에서도 관성력에 의해 흐름방향 유속이 두드러지게 나타났으나 무활조건을 적용한 경우 교각 후면에서 와가 형성되고 후류현상이 두드러지게 나타났다. 무활조건을 적용한 경우 교각 전면부에서는 선수파(bow wave)가 4 cm정도 높게 나타났으며 교각 측면부에서는 2 cm 높게 나타났다. 반면 교각 후면에서는 후류의 영향으로 수면이 2 cm 낮게 분포하였다. 교각부에 작용하는 전단력을 분석한 결과 무활조건을 적용한 경우가 활동조건을 적용한 경우에 비해 최대 6배 높은 전단력이 나타났다.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.6
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• pp.87-98
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• 2009

It is well known that reinforcement details in the plastic hinge region of bridge piers give the most important effects on the seismic performance of bridges, from investigations of bridge failures in many earthquake events and in laboratory tests. Longitudinal reinforcement details give larger effects than lateral reinforcement details do. The lap-spliced longitudinal steel shows slip during earthquake events, which results in low ductility and inadequate seismic performance. However, before the issue of the earthquake design code, a considerable number of bridge piers were constructed with lap-spliced longitudinal steel in the plastic hinge region. Therefore, a large amount of research has been conducted on the seismic performance and retrofit of circular and rectangular shaped bridge columns with lap-spliced longitudinal steel. However, research on wall type piers is very limited. This paper investigates the seismic performance of a pier wall by a quasi-static test in the weak axis direction and proposes a retrofit method. From the test with variables being the longitudinal steel detail and the transverse steel amount, it is shown that the currently used definition of yield displacement is not adequate. Therefore a new definition of yield displacement for the ductility investigation for a pier wall is proposed. In addition, a retrofit method by steel plates and bolts is proposed to improve ductility, and test results show that slip of the longitudinal steel is prevented by up to a considerably large displacement.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.5
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• pp.53-58
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• 2002

A recent development, a concrete-filled steel(CFS) pier is an alternative to a reinforced concrete bridge pier in an urban area, because of its fast construction and excellent ductility against earthquakes. The capacity of CFS piers has not been used to a practical design, because there is no guide of a seismic design for CFS piers. Therefore, the guide of a seismic design value is derived from tests of CFS piers in order to apply it to a practical seismic design. Steel piers and concrete-filled steel piers are tested with constant axial load using quasi-static cyclic lateral load to check ductile capacity and using the real Kobe ground motion of pseudo-dynamic test to verify seismic performance. The results prove that CFS piers have more satisfactory ductility and strength than steel piers and relatively large hysteretic damping in dynamic behaviors. The seismic performance of steel and CFS piers is quantified on the basis of the test results. These results are evaluated through comparison of both the response modification factor method by elastic response spectrum and the performance-based design method by capacity spectrum and demand spectrum using effective viscous damping. The response modification factor of CFS piers is presented to apply in seismic design on a basis of this evaluation for a seismic performance.

• Journal of Korea Water Resources Association
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• v.31 no.5
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• pp.539-552
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• 1998

When the pier is constructed in the cohesive be, the accuracy maynot be obtained because the equation for calculating the scour at piers is based upon the results which are analyzed through the experiments in the non-cohesive bed. In this paper, the variation of the depth of the pier scour occurred by constructing 5 types of pier in the channel having the cohesive material is examined. The experimental results are analyzed based upon Froude numbers and non-dimensional numbers which are indicated as the flow depths compared to the pier width. The results are also compared with the results obtained using the existing pier scour equations. In this paper, the shape factors, which can be used for calculating the scour depth of the pier in the cohesive channel bed, are suggested. The shape factors are indicated through the ratios between the scour depth at the circular pier and the scour depths at the different types of pier, and are suggested as two stages. In the first stage, in which the water depth compared to the pier width is less than 1.2, the shape factors are given as the equations. However, in the second stage the shape factors are given as the constant values. It is understood that the shape factors suggested in this paper can be properly usd for calculating local scour at piers in the bridges which are constructed in the cohesive channel bed having the characteristics of the bed material which is used in these experiments. Keywords : local scour, maximum scour depth, cohesive bed material, pier shape, pier, shape factor.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1737-1741
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• 2008

하천 개수나 치수를 위한 기초 연구의 일환으로 수치모형을 이용한 검증 및 예측 과정이 요구되어 왔고, 고전적인 수치모의 방법으로 결과 산출이 용이한 1차원 모형을 적용시켜 왔다. 1차원 모형의 경우 모의영역을 쉽게 넓힐 수 있고, 입력 자료가 간단하다는 장점이 있지만, 수직적이고 수평적인 흐름특성 변화 및 난류 구조를 보이는 3차원적인 자연하천 흐름을 종방향의 1차원적인 모의 결과를 이용하여 평가한다는 점에서 비현실적이다. 하천을 가로질러 교각이나 보와 같은 구조물이 위치하고 있거나, 좌우 비대칭적인 형상의 수로를 모의할 경우 흐름특성의 공간적인 분포는 단순한 단면 평균적인 개념으로는 설명되기 힘들다. 최근에야 비로소 수공학 관련 실무자들에 의해서 최소한 2차원 수치모형을 기본적인 평가법으로 도입해야 한다는 분위기가 감지되고 있으며, 일반적으로 한강과 같은 대하천을 모의할 경우, 대다수의 실무자들과 연구자들이 축척을 문제 삼아 수로 내부에 위치한 교각을 생략하여 2차원 모의를 수행하기도 한다. 따라서 본 연구에서는 수로 내부에 위치한 교각을 2차원 모의하는 방법에 대한 비교 평가를 수행하고자 한다. 동일한 격자를 이용하여 교각을 고려하지 않았을 경우와 교각 형상을 모의 영역에서 삭제하여 경계처리를 하였을 경우, 마지막으로 교각이 위치하고 있는 영역에 항력을 적용하였을 경우에 대해서 비교 평가한다. 이를 위하여 2차원 천수방정식을 흐름방정식으로 하는 유한요소모형을 구축하였으며, 모형의 검증을 위해 교각이 수로에 위치할 경우에 대한 실내 실험 자료와 비교한다. 또한 검증된 모형을 이용하여 교각이 포함된 한강의 일부 구간을 선정하여, 교각 모의 방법에 대한 비교 평가를 수행한다. 본 연구에서 구축된 자료 및 제시된 수치모형은 하천복원, 치수관리 측면에서 매우 유용하게 사용될 것으로 기대된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3A
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• pp.383-390
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• 2008

A Precast Prefabricated Bridge Column using steel tube and prestressing bar was proposed for the application of precast method on substructure. A column specimen designed by the proposed bridge column system was made and performed a quasi-static test. The failure mode appeared to be a flexural failure and there is no damage on column segment connection. And it is good use of the self-centering ability by prestressing force. Test results showed that a column specimen satisfy the earthquake specification, and the structural stability was verified. Nonlinear finite element analysis was performed and compared with the test results. Force-displacement relation and location of crack from the analysis results were compared with the test results and it agreed well. The quantitative analysis was also performed by a parametric study using this modeling technique.