• Structural Monitoring and Maintenance
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• 제3권4호
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• pp.315-333
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• 2016

This study aims to perform damage identification for Da-Sheng-Guan (DSG) high-speed railway truss arch bridge using fuzzy clustering analysis. Firstly, structural health monitoring (SHM) system is established for the DSG Bridge. Long-term field monitoring strain data in 8 different cases caused by high-speed trains are taken as classification reference for other unknown cases. And finite element model (FEM) of DSG Bridge is established to simulate damage cases of the bridge. Then, effectiveness of one fuzzy clustering analysis method named transitive closure method and FEM results are verified using the monitoring strain data. Three standardization methods at the first step of fuzzy clustering transitive closure method are compared: extreme difference method, maximum method and non-standard method. At last, the fuzzy clustering method is taken to identify damage with different degrees and different locations. The results show that: non-standard method is the best for the data with the same dimension at the first step of fuzzy clustering analysis. Clustering result is the best when 8 carriage and 16 carriage train in the same line are in a category. For DSG Bridge, the damage is identified when the strain mode change caused by damage is more significant than it caused by different carriages. The corresponding critical damage degree called damage threshold varies with damage location and reduces with the increase of damage locations.

• Smart Structures and Systems
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• 제18권3호
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• pp.585-599
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• 2016

Steel cables serve as the key structural components in long-span bridges, and the force state of the steel cable is deemed to be one of the most important determinant factors representing the safety condition of bridge structures. The disadvantages of traditional cable force measurement methods have been envisaged and development of an effective alternative is still desired. In the last decade, the vision-based sensing technology has been rapidly developed and broadly applied in the field of structural health monitoring (SHM). With the aid of vision-based multi-point structural displacement measurement method, monitoring of the tensile force of the steel cable can be realized. In this paper, a novel cable force monitoring system integrated with a multi-point pattern matching algorithm is developed. The feasibility and accuracy of the developed vision-based force monitoring system has been validated by conducting the uniaxial tensile tests of steel bars, steel wire ropes, and parallel strand cables on a universal testing machine (UTM) as well as a series of moving loading experiments on a scale arch bridge model. The comparative study of the experimental outcomes indicates that the results obtained by the vision-based system are consistent with those measured by the traditional method for cable force measurement.

• Earthquakes and Structures
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• 제7권3호
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• pp.333-347
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• 2014

Multi-scale model can take both computational efficiency and accuracy into consideration when it is used to conduct elasto-plastic seismic response analysis for complex steel bridges. This paper proposed a method based on pushover analysis of member sharing the same section pattern to verify the accuracy of multi-scale model. A deck-through type steel arch bridge with a span length of 200m was employed for seismic response analysis using multi-scale model and fiber model respectively, the validity and necessity of elasto-plastic seismic analysis for steel bridge by multi-scale model was then verified. The results show that the convergence of load-displacement curves obtained from pushover analysis for members having the same section pattern can be used as a proof of the accuracy of multi-scale model. It is noted that the computational precision of multi-scale model can be guaranteed when length of shell element segment is 1.40 times longer than the width of section where was in compression status. Fiber model can only be used for the predictions of the global deformations and the approximate positions of plastic areas on steel structures. However, it cannot give exact prediction on the distribution of plastic areas and the degree of the plasticity.

• 한국강구조학회 논문집
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• 제17권1호통권74호
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• pp.13-21
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• 2005

본 논문에서는 강아치교의 고등해석과 최적설계를 수행하였다. 고등해석은 해석시에 구조계와 그에 속한 부재의 강도와 안정을 직접 고려함으로서, 해석후 개별부재의 강도검토가 필요없는 설계방법을 지칭한다. 기하학적 비선형 효과를 고려하기 위하여 안정함수를 사용하였다. 잔류응력으로 인한 점진적인 소성화를 고려하기 위하여 CRC 접선 탄성계수를 사용하였다. 탄성강성에서 완전소성강성까지 점진적인 소성화를 나타내기 위하여 포물선 함수를 사용하였다. 최적화 기법으로는 수정된 단면점증법을 사용하였다. 수정된 단면점증법은 AASHTO-LRFD의 상관방정식으로 계산된 값중에서 최대값을 가지는 부재의 크기를 단계별로 증가시키는 방법이다. 목적함수는 구조물의 중량을 사용하였으며, 제약조건식은 구조시스템의 하중-저항능력 및 처짐 조건을 고려하였다. 제안된 방법에 의한 설계결과를 기존의 연구결과와 비교하였다.

• 한국방재학회 논문집
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• 제11권1호
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• pp.15-22
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• 2011

본 논문에서는 아치 형상을 갖는 강재 거더에 콘크리트가 충진되고 외부에 긴장력을 도입하여 구조적 효율성을 높인 CFTA 거더(Concrete-Filled and Tied Steel Tubular Arch Girder)의 아치효과와 구조적 성능을 검증하기 위해 정적하중재하실험을 수행하였고, 실험결과의 타당성을 검증하기 위해 유한요소해석을 수행하였다. CFTA 거더는 강재, 콘크리트, PS강재 등을 이용하여 각 재료의 역학적 장점을 최대한 발휘하도록 형상화하였다. 본 연구에서는 프레임해석프로그램으로 지간장 12m인 축소모형을 설계하였으며, 해석결과에 근거하여 정적재하실험이 수행되었다. 정적재하실험 결과, CFTA 거더의 구조적 성능과 안전성이 검증되었으며, 아치 효과에 의해 타 구조형식과는 다른 처짐 형상이 나타났다. 또한 ABAQUS 프로그램을 이용한 유한요소해석을 통해 차량 충돌 안정성과 정적재하실험결과의 타당성을 입증하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1691-1696
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• 2010

Jeong-Ji overbridge is designed to be 9.3km long, the longest for a high speed railway bridge ever constructed in Korea. This bridge is constituted of three types of structure. Standard type bridge is 35m PSC Box bridge which will be constructed by Precast Span Method. To cross the Cheonan Nonsan Expressway, 80m three-span steel arch bridge is designed to avoid rail expansion joint. Finally, Extradosed bridge is planned for high speed railway bridge for the first time in Korea based on originative and advanced design techniques. It is expected that this will contribute to the development of national technology for long-span high speed railway bridges.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.276-281
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• 2008

Glass-fiber reinforced polyester(GFRP) composite material is a promising alternative to existing construction materials such as steel, concrete and wood. One of passible applications of GFRP composite material is to build temporary bridges by assembling GFRP composite decks. In this paper, we develop a system of temporary arch bridges that can be built by easy assembling of GFRP composite decks. For this purpose, several types of temporary arch bridges are suggested and verified by FE analysis.

• Smart Structures and Systems
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• 제22권6호
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• pp.727-741
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• 2018

To mitigate vibrations, tuned mass dampers(TMD) are widely used for long span bridges or high-rise buildings. Due to some durability concerns, such as fluid degradation, oil leakage, etc., the alternative solutions, such as the non-contacted eddy current damping (ECD), are proposed for mechanical devices in small scales. In the present study, a new eddy current damping TMD (ECD-TMD) is proposed and developed for large scale civil infrastructure applications. Starting from parametric study on finite element analysis of the ECD-TMD, the new design is enhanced via using the permanent magnets to eliminate the power need and a combination of a copper plate and a steel plate to improve the energy dissipation efficiency. Additional special design includes installation of two permanent magnets at the same side above the copper plate to easily adjust the gap as well as the damping. In a case study, the proposed ECD-TMD is demonstrated in the application of a steel arch bridge to mitigate the wind-induced vibrations of the flexible hangers. After a brief introduction of the configuration and the installation process for the damper, the mitigation effects are measured for the ambient vibration and forced vibration scenarios. The results show that the damping ratios increase to 3% for the weak axis after the installation of the ECD-TMDs and the maximum vibration amplitudes can be reduced by 60%.

• Steel and Composite Structures
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• 제15권5호
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• pp.567-583
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• 2013

Experimental studies and finite element analyses have been carried out to establish the effect of tendon damage on the structural behavior of concrete filled tubular tied arch girder (CFTA girder). The damage of tendon is considered in different stages by varying the number of damaged cables in the tendon. Static and dynamic structural parameters are observed at each stage. The results obtained from the experiments and numerical studies have been compared to validate the studies. The tendons whose damage can significantly affect the stiffness of the CFTA girder are identified by performing the sensitivity analysis. The locations in the girder which are sensitive to the tendon damage are also identified.

• 한국강구조학회 논문집
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• 제15권2호
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• pp.197-206
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• 2003

본 논문에서는 유전자 알고리즘을 이용한 비선형 탄성 최적설계 방법을 제시하였다. 제안한 비선형 탄성해석은 종래 설계의 단점 즉 탄성해석 후 비선형 효과를 고려하기 위하여 $B_1$, $B_2$ 계수를 사용하는 불합리성을 극복하였다. 유전자 알고리즘은 다윈(Darwin)의 적자생존의 개념을 기본으로 선택, 교배 및 돌연변이라는 세 가지 연산을 수행함으로써 최적설계에 필요한 설계변수 즉 부재 단면을 형성하여, 제약조건을 모두 만족하는 최소 구조물 중량을 제공하는 설계변수를 선택하면서 최적설계를 수행하였다. 목적함수로는 구조물의 총중량을 사용하였으며, 제약조건식으로는 하중저항능력, 사용성 및 연성도를 사용도를 사용하여 최적설계를 수행하였다. 2차원 강뼈대 구조물, 3차원 강뼈대 구조물, 그리고 3차원 강아치교의 설계예제를 수행하였다.