• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.355-358
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• 2005

In this paper, an actual behavior of the pylon of Seohae Grand Bridge which is a cable stayed bridge and has been constructed 4 years ago was analyzed by using data acquisition system. As a result, the pylon of cable stayed bridge behaved normally with respect to the change of temperature. The annual displacement of the top of pylon(PY1) ranged from -71.4mm to +181.7mm in the longitudinal direction of the bridge. In the case of the longitudinal displacement, the displacement of PY1 was bigger than that of PY2 because PY1 is movable and PY2 is fixed in terms of the constraint condition of super structure. For the long term, PY1 will be sloped gently to the direction of Dangjin and PY2 will be also sloped gently to the direction of Pyongtaek by the effect of creep and shrinkage in the case of the longitudinal direction. The result of structural analysis showed good agreement with the result mentioned above.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.362-369
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• 2002

This paper mainly propose the new passive vibration control device, named BRV(the bridge reduced vibration), for reducing excessive traffic-induced vibration of bridges and for measuring performance of BRV numerical example was simulated. The purpose of BRV is mainly on reducing vertical acceleration and displacement of bridge. In BRV we can control the stiffness and damping coefficient to accept the performance we want. The result of simulation showed that the vertical acceleration and displacement was effectively diminished. It would be concluded that BRV can be used to improve the serviceability of bridge and fatigue life etc.

• 대한토목학회논문집
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• 제28권4A호
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• pp.507-515
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• 2008

본 연구에서는 모드분해기법을 이용한 변형률신호로부터 변위응답추정 방법을 개발하였다. 일반적으로 교량의 안정성평가는 완공 후에 초점이 맞추어져 있다. 하지만 가설 중에도 풍하중과 지진하중과 같은 동적하중에 노출되어 있으며, 이런 동적하중에 대한 안정성을 검토하기 위해 교량의 안정성 평가에 있어 중요한 인자인 변위를 추정하는 것이 중요하다. 그러나 건설현장에서의 적절한 변위측정 방법의 부재로 인하여 대형구조물의 전체적인 변위를 측정할 수 없는 것이 현실이다. 본 연구에서는 간접적으로 변위를 추정하는 방법인 변형률로 변위를 추정하는 방법을 제시하였으며, 광섬유 브래그 격자 센서(fiber optic Bragg-grating sensor)를 사용하여 변형률을 계측하였다. 기존에도 FBG센서를 이용한 변위추정 방법이 있었으며 기존의 방법으로는 정적하중에 대한 변위추정은 가능하였으나 고차 모드의 변형률신호와 노이즈의 영향 때문에 동적하중에 대한 변위추정은 많은 오차가 발생하여 정확한 변위추정이 어려웠다. 이런 오차를 줄이는 방법으로 모드분해기법을 사용하였다. 모드분해기법은 변형률신호로부터 proper orthogonal decomposition(POD)을 이용하여 추정한 모드형상과 empirical mode decomposition(EMD)을 이용하여 모드 분해한 변형률신호로 모드별 변위응답을 추정하고, 구조물의 주요 모드에 대한 변위응답을 합하여 전체변위응답을 추정하는 방법이다. 제안한 모드분해기법을 검증하기 위해 실내모형실험을 수행하였다.

• Earthquakes and Structures
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• 제17권6호
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• pp.533-543
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• 2019

This paper presents a study on the behavior of an RC bridge under near-field and far-field ground motions. For this purpose, a dynamic nonlinear finite element time history analysis has been conducted. The near-field and far-field records are chosen pairwise from the same events which are fits to the seismic design of the bridge. In order to perform an accurate seismic evaluation, the model has been analyzed under two vertical and horizontal components of ground motions. Parameters of relative displacement, residual displacement, and maximum plastic strain have been considered and compared in terms of near-field and far-field ground motions. In the following, in order to decrease the undesirable effects of near-field ground motions, a viscous damper is suggested and its effects have been studied. In this case, the results show that the near-field ground motions increase maximum relative and residual displacement respectively up to three and twice times. Significant seismic improvements were achieved by using viscous dampers on the bridge model. Somehow under the considered near-field ground motion, parameters of residual and relative displacement decrease dramatically even less than the model without damper under the far-field record of the same ground motion.

• Structural Engineering and Mechanics
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• 제55권2호
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• pp.365-377
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• 2015

Large-amplitude vibration of overhead sign structures can cause unfavorable psychological responses in motorists, interfere with readability of the signs, and lead to fatigue cracking in the sign structures. Field experience in Texas suggests that an overhead sign structure can vibrate excessively when supported within the span of a highway bridge instead of at a bent. This study used finite element modeling to analyze the dynamic displacement response of three hypothetical sign structures subjected to truck-passage-induced vertical oscillations recorded for the girders from four actual bridges. The modeled sign bridge structures included several span lengths based on standard design practices in Texas and were mounted on precast concrete I-girder bridges. Results revealed that resonance with bridge girder vertical vibrations can amplify the dynamic displacement of sign structures, and a specific range of frequency ratios subject to undesirable amplification was identified. Based on these findings, it is suggested that this type of sign structure be located at a bridge bent if its vertical motion frequency is within the identified range of bridge structure excitation frequencies. Several alternatives are investigated for cases where this is not possible, including increasing sign structure stiffness, reducing sign mass, and installing mechanical dampers.

• Structural Engineering and Mechanics
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• 제17권1호
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• pp.99-112
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• 2004

It is known that lap splices in the longitudinal reinforcement of reinforced concrete (RC) bridge columns are not desirable for seismic performance, but it is sometimes unavoidable. Lap splices were practically located in the potential plastic hinge region of most bridge columns that were constructed before the 1992 seismic design provisions of the Korea Bridge Design Specification. The objective of this research is to evaluate the seismic performance of reinforced concrete (RC) bridge piers with lap splicing of longitudinal reinforcement in the plastic hinge region, to develop an enhancement scheme for their seismic capacity by retrofitting with glassfiber sheets, and to assess a damage of bridge columns subjected to seismic loadings for the development of rational seismic design provisions in low or moderate seismicity region. Nine (9) test specimens with an aspect ratio of 4 were made with three confinement ratios and three types of lap splice. Quasi-static tests were conducted in a displacement-controlled way under three different axial loads. A significant reduction of displacement ductility was observed for test columns with lap splices of longitudinal reinforcements, whose displacement ductility could be greatly improved by externally wrapping with glassfiber sheets in the plastic hinge region. A damage of the limited ductile specimen was assessed to be relatively small.

• 한국지리정보학회지
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• 제15권4호
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• pp.114-123
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• 2012

본 연구는 국내에 시공이 완료되어 공용중인 해안 구조물 중 현수교를 대상으로 그 기하형상을 결정하고, 이를 이용하여 공용 이후의 대상 현수교의 변위를 결정함으로써, 케이블 교량의 안정성을 평가하는데 그 목적을 둔다. 이를 위해 공용 이후 시기별 주경간의 길이, sag, sag 비, 그리고 주탑의 변위를 산정하였다. 이는 대상 현수교 주탑의 거동에 따른 단계별 관리기준과 비교해 볼 때, 대상 현수교가 유지관리기준 범위 내에서 안정적으로 거동하고 있음을 알 수 있었다. 이상과 같이 현수교의 거동을 정확히 파악하기 위해서는 그 기하형상의 결정이 우선시된다. 따라서 공용기간 및 교통량의 증가에 따른 주기적인 실측형상모델의 결정이 필요하며, 이는 현수교 유지관리에 있어서 그 안정성 확보에 크게 기여할 수 있을 것으로 기대된다.

• 한국구조물진단유지관리공학회 논문집
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• 제20권2호
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• pp.40-48
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• 2016

본 연구는 지진이 발생할 경우 장대레일교량에 있어 레일과 상판 간의 종방향 상호작용에 미치는 영향을 검토하기 위한 것으로, 해석모델에 여러 하중조합과 함께 지진하중을 적용함으로써 대상 철도교량 레일에서의 축방향 부가응력과 레일-상판 간 상대변위의 변화를 산출하였다. 해석 결과, 본 연구 대상 철도교량의 경우 철도시설공단에서 제시하고 있는 표준응답스펙트럼을 적용할 때 레일부가응력은 대부분의 하중조합에 대해 허용기준 내의 값을 보이고 있는 반면, 레일-상판 상대변위는 공단에서 제시하는 허용기준을 초과하고 있는 것으로 나타났다. 따라서 레일-상판 상대변위가 레일부가응력에 비해 상대적으로 더 허용기준을 만족시키기 어렵다는 것을 알 수 있었으며, 아울러 고베 대지진과 같은 큰 규모의 지진이 발생하면 레일부가응력과 레일-상판 상대변위는 허용기준을 충족시키지 못하므로 이에 대한 적절한 내진 대비가 필요하다.

• Structural Engineering and Mechanics
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• 제80권6호
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• pp.749-765
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• 2021

Suspension bridges bear large eccentric live loads in rush hours when most vehicles travel in one direction on the left or right side of the bridge. With the increasing number and weight of vehicles and the girder widening, the eccentric live load effect on the bridge behavior, including bending and distortion of the main girder, gets more pronounced, even jeopardizing bridge safety. This study proposes an analytical algorithm based on multi-catenary theory for predicting the suspension bridge responses to eccentric live load via the nonlinear generalized reduced gradient method. A set of governing equations is derived to solve the following unknown values: the girder rigid-body displacement in the longitudinal direction; the horizontal projection lengths of main cable's segments; the parameters of catenary equations and horizontal forces of the side span cable segments and the leftmost segments of middle span cables; the suspender tensions and the bearing reactions. Then girder's responses, including rigid-body displacement in the longitudinal direction, deflections, and torsion angles; suspenders' responses, including the suspender tensions and the hanging point displacements; main cables' responses, including the horizontal forces of each segment; and the longitudinal displacement of the pylons' tower top under eccentric load can be calculated. The response of an exemplar suspension bridge with three spans of 168, 548, and 168 m is calculated by the proposed analytical method and the finite element method in two eccentric live load cases, and their results prove the former's feasibility. The nonuniform distribution of the live load in the lateral direction is shown to impose a greater threat to suspension bridge safety than that in the longitudinal direction, while some other specific features revealed by the proposed method are discussed in detail.

• Earthquakes and Structures
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• 제16권6호
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• pp.665-677
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• 2019

This study utilizes large-scale shake table test to investigate the seismic performance of an isolated bridge with lead rubber bearings crossing an active fault. Two transverse restraining systems with and without shear keys are tested by applying spatially varying ground motions. It is shown that the near-fault span exhibits larger bearing displacement than the crossing-fault span. Bridge piers away from the fault rupture are more vulnerable than those adjacent to the fault rupture by attracting more seismic demand. It is also verified that the shear keys are effective in restraining the bearing displacement on the near-fault span, particularly under the large permanent ground displacement.