• Structural Engineering and Mechanics
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• 제24권3호
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• pp.339-354
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• 2006

Hangzhou Bay Bridge spans the Hangzhou Bay and is located at Zhejiang province in the southeast seacoast of China. The total length of the bridge is 36 km. The bridge is composed of bridge approaches made up of multi-span prestressed concrete box girders and two cable-stayed bridges over the north and south navigable spans respectively. The seismic response analysis of the bridge model shows that if the navigable spans are designed as the routine earthquake-resistance system, the displacements and internal forces in pylons, piers and deckes are too large to satisfy the anti-seismic requirement of the structure. Therefore, the seismic reduction design was carried out by using viscous dampers to dissipate the kinetic energy of the structure both longitudinally and transversely. Using the vibration reduction system and aiming at the reasonable optimal goal, the purpose to reduce the seismic responses in south and north navigable spans has been achieved.

• 한국지진공학회논문집
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• 제24권4호
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• pp.169-178
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• 2020

In a previous paper, ambient vibration tests were conducted on a cable stayed bridge with resilient-friction base isolation systems (R-FBI) to extract the dynamic characteristics of the bridge and compare the results with a seismic analysis model. In this paper, a nonlinear seismic analysis model was established for analysis of the bridge to compare the difference in seismic responses between nonlinear time history analysis and multi-mode spectral analysis methods in the seismic design phase of cable supported bridges. Through these studies, it was confirmed that the seismic design procedures of the "Korean Highway Bridge Design Code (Limit State Design) for Cable Supported Bridges" is not suitable for cable supported bridges installed with R-FBI. Therefore, to reflect the actual dynamic characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure is proposed that applies the seismic analysis method differently depending on the seismic isolation effect of the R-FBI for each seismic performance level.

• 한국건설순환자원학회논문집
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• 제1권2호
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• pp.120-127
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• 2013

밤콩 사장교는 메콩강 삼각주 지역 연결 사업의 일환으로 메콩강 하류의 꾸롱 삼각주에 위치하고 있으며, 중앙경간 450m의 사장교로 설계되었다. 왕복 4차선으로 구성된 강합성 보강형과 멀티 스트랜드 방식의 케이블을 적용하였으며, 개선된 H형 주탑과 현장타설 콘크리트 말뚝 기초로 구성되어 있다. 주탑, 프리캐스트 콘크리트 바닥판 그리고 현장타설 콘크리트 말뚝에는 고강도 콘크리트를 적용하여 구조적 안정성을 확보하였다. 본 고에서는 밤콩 사장교의 설계에 적용된 설계기준 및 주요 설계 특징을 설명하고자 한다.

• Structural Engineering and Mechanics
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• 제70권2호
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• pp.169-178
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• 2019

The replacement of damaged components is an important task for long-span bridges. Conventional strategy for component replacement is to close the bridge to traffic, so that the influence of the surrounding environment is reduced to a minimum extent. However, complete traffic interruption would bring substantial economic losses and negative social influence nowadays. This paper investigates traffic control technologies without interruption for component replacement of long-span bridges. A numerical procedure of traffic control technologies is proposed incorporating traffic microsimulation and site-specific data, which is then implemented through a case study of cable replacement of a long-span cable-stayed bridge. Results indicate traffic load effects on the bridge are lower than the design values under current low daily traffic volume, and therefore cable replacement could be conducted without traffic control. However, considering a possible medium or high level of daily traffic volume, traffic load effects of girder bending moment and cable force nearest to the replaced cable become larger than the design level. This indicates a potential risk of failure, and traffic control should be implemented. Parametric studies show that speed control does not decrease but increase the load effects, and flow control using lane closure is not effectual. However, weight control and gap control are very effective to mitigate traffic load effects, and it is recommended to employ a weight control with gross vehicle weight no more than 65 t or/and a gap control with minimum vehicle gap no less than 40 m for the cable replacement of the case bridge.

• 한국전산구조공학회논문집
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• 제24권6호
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• pp.655-662
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• 2011

본 논문에서는 다지점 가진 시 장대교량에 대한 지진응답해석을 수행하고 설계상의 다양한 요구에 유연하게 대처하기 위해서 다지점 가진 해석에 필요한 비선형시간이력해석 알고리즘(영향계수법)을 제안하고, 이를 신뢰성있는 비선형 유한요소해석 프로그램(RCAHEST)에 추가하였다. 동일한 유한요소모델에 대해 범용 유한요소해석 프로그램 SAP2000의 Multi-support Excitation 기능을 이용하여 연구에서의 결과에 대한 비교 검증을 수행하였다. 이 연구결과를 바탕으로 인천대교에 대해서 유한요소모델링을 실시하고 다지점 가진을 고려한 비선형시간이력해석을 수행하였다. 수평변위응답의 분석 결과 시간지연이 늘어날수록 최대 수평변위가 줄어드는 것을 확인할 수 있었다. 또한 입력지진파의 최대가속도를 단계적으로 증가시키며 극한해석을 수행하여 대상 교량의 사용성을 평가하였다.

• Smart Structures and Systems
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• 제15권1호
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• pp.99-117
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• 2015

The Stonecutters Bridge (SCB) in Hong Kong is the third-longest cable-stayed bridge in the world with a main span stretching 1,018 m between two 298 m high single-leg tapering composite towers. A Wind and Structural Health Monitoring System (WASHMS) is being implemented on SCB by the Highways Department of The Hong Kong SAR Government, and the SCB-WASHMS is composed of more than 1,300 sensors in 15 types. In order to establish a linkage between structural health monitoring and maintenance management, a Structural Health Rating System (SHRS) with relevant rating tools and indices is devised. On the basis of a 3D space frame finite element model (FEM) of SCB and model updating, this paper presents the development of an SHR-oriented 3D multi-scale FEM for the purpose of load-resistance analysis and damage evaluation in structural element level, including modeling, refinement and validation of the multi-scale FEM. The refined 3D structural segments at deck and towers are established in critical segment positions corresponding to maximum cable forces. The components in the critical segment region are modeled as a full 3D FEM and fitted into the 3D space frame FEM. The boundary conditions between beam and shell elements are performed conforming to equivalent stiffness, effective mass and compatibility of deformation. The 3D multi-scale FEM is verified by the in-situ measured dynamic characteristics and static response. A good agreement between the FEM and measurement results indicates that the 3D multi-scale FEM is precise and efficient for WASHMS and SHRS of SCB. In addition, stress distribution and concentration of the critical segments in the 3D multi-scale FEM under temperature loads, static wind loads and equivalent seismic loads are investigated. Stress concentration elements under equivalent seismic loads exist in the anchor zone in steel/concrete beam and the anchor plate edge in steel anchor box of the towers.

• Structural Engineering and Mechanics
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• 제54권2호
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• pp.337-362
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• 2015

This paper presents a feasibility study on structural damage alarming and localization of long-span cable-supported bridges using multi-novelty indices formulated by monitoring-derived modal parameters. The proposed method which requires neither structural model nor damage model is applicable to structures of arbitrary complexity. With the intention to enhance the tolerance to measurement noise/uncertainty and the sensitivity to structural damage, an improved novelty index is formulated in terms of auto-associative neural networks (ANNs) where the output vector is designated to differ from the input vector while the training of the ANNs needs only the measured modal properties of the intact structure under in-service conditions. After validating the enhanced capability of the improved novelty index for structural damage alarming over the commonly configured novelty index, the performance of the improved novelty index for damage occurrence detection of large-scale bridges is examined through numerical simulation studies of the suspension Tsing Ma Bridge (TMB) and the cable-stayed Ting Kau Bridge (TKB) incurred with different types of structural damage. Then the improved novelty index is extended to formulate multi-novelty indices in terms of the measured modal frequencies and incomplete modeshape components for damage region identification. The capability of the formulated multi-novelty indices for damage region identification is also examined through numerical simulations of the TMB and TKB.

• Structural Engineering and Mechanics
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• 제43권5호
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• pp.583-605
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• 2012

This paper presents a spatial catenary cable element for the nonlinear analysis of cable-supported structures. An incremental-iterative solution based on the Newton-Raphson method is adopted for solving the equilibrium equation. As a result, the element stiffness matrix and nodal forces are determined, wherein the effect of self-weight and pretension are taken into account. In the case of the initial cable tension is given, an algorithm for form-finding of cable-supported structures is proposed to determine precisely the unstressed length of the cables. Several classical numerical examples are solved and compared with the other available numerical methods or experiment tests showing the accuracy and efficiency of the present elements.

• 한국강구조학회 논문집
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• 제25권4호
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• pp.335-346
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• 2013

AASHTO LRFD 및 도로교한계상태설계기준에서는 신뢰도 기반 활하중 모델로부터 결정된 트럭하중과 차로하중을 동시에 재하하도록 하고 있으며, 트럭하중은 충격계수를 고려하되 차로하중은 충격계수를 적용하지 않도록 규정하고 있다. 본 연구에서는 중앙경간 230m, 400m 및 540m의 멀티케이블 강합성 사장교를 대상으로 트럭하중과 차로하중이 동시에 주행하는 경우에 대해 차량-교량 상호작용 해석을 수행하고 케이블과 보강거더의 충격계수를 평가하였다. 트럭하중은 6-자유도의 차량 모델을 사용하였으며, 차로하중은 일련의 1축 차량이 연행해서 주행하는 것으로 모사하였다. 교량의 감쇠비가 충격계수에 미치는 영향을 평가하였으며, 충격에 영향을 미치는 주요 인자인 노면조도와 주행속도를 해석변수로 고려하였다. 노면조도는 ISO 8608 규정에 근거하여 랜덤 생성하였으며, 차량-교량 상호작용해석 시 노면조도는 트럭하중에만 적용하였다. 한편, 사장교의 충격계수 평가를 위해 실무에서 사용되고 있는 영향선 기법에 의한 충격계수를 동적 상호작용 해석에 의한 결과와 비교하였다.

• Smart Structures and Systems
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• 제25권4호
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• pp.487-499
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• 2020

This paper proposes a novel approach to model updating for a large-scale cable-stayed bridge based on ambient vibration tests coupled with a hybrid metaheuristic search algorithm. Vibration measurements are carried out under excitation sources of passing vehicles and wind. Based on the measured structural dynamic characteristics, a finite element (FE) model is updated. For long-span bridges, ambient vibration test (AVT) is the most effective vibration testing technique because ambient excitation is freely available, whereas a forced vibration test (FVT) requires considerable efforts to install actuators such as shakers to produce measurable responses. Particle swarm optimization (PSO) is a famous metaheuristic algorithm applied successfully in numerous fields over the last decades. However, PSO has big drawbacks that may decrease its efficiency in tackling the optimization problems. A possible drawback of PSO is premature convergence leading to low convergence level, particularly in complicated multi-peak search issues. On the other hand, PSO not only depends crucially on the quality of initial populations, but also it is impossible to improve the quality of new generations. If the positions of initial particles are far from the global best, it may be difficult to seek the best solution. To overcome the drawbacks of PSO, we propose a hybrid algorithm combining GA with an improved PSO (HGAIPSO). Two striking characteristics of HGAIPSO are briefly described as follows: (1) because of possessing crossover and mutation operators, GA is applied to generate the initial elite populations and (2) those populations are then employed to seek the best solution based on the global search capacity of IPSO that can tackle the problem of premature convergence of PSO. The results show that HGAIPSO not only identifies uncertain parameters of the considered bridge accurately, but also outperforms than PSO, improved PSO (IPSO), and a combination of GA and PSO (HGAPSO) in terms of convergence level and accuracy.