• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.167-174
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• 2007

This study proposes a practical and realistic method to establish an optimal lifetime maintenance strategy for deteriorating bridges by considering the life-cycle performance as well as the life-cycle cost. The proposed method offers a set of optimal tradeoff maintenance scenarios among other conflicting objectives, such as minimizing cost and maximizing performance. A genetic algorithm is used to generate a set of maintenance scenarios that is a multi-objective combinatorial optimization problem related to the and the life-cycle cost and performance as separate objective functions. A computer program, which generates optimal maintenance scenarios, was developed based on the proposed method. The subordinate relation between bridge members has been considered to decide optimal maintenance sequence. The developed program has been used to present a procedure for finding an optimal maintenance scenario for steel-girder bridges on the Korean National Road. Through this bridge maintenance scenario analysis, it is expected that the developed method and program can be effectively used to allow bridge managers an optimal maintenance strategy satisfying various constraints and requirements.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.60-68
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• 2017

Since the bridge is the main facility of the road that is the core of the civil infrastructure, the bridge is constructed to ensure stability and serviceability during the traffic use. In order to secure the safety of bridges, evaluating the integrity of bridges at present is an important task in the maintenance work of bridges. In general, to evaluate the load carrying capacity of bridges, it is possible to confirm the superimposed behavior and symmetric behavior of bridges by estimating the lateral load distribution factor of the bridges through vehicle loading tests. However, in order to measure the lateral load distribution factor of a commonly used bridge, a static loading test is performed. There is a difficulty in traffic control. Therefore, in this study, the static displacement component of the bridge measured in the dynamic loading test and the ambient vibration test was extracted by using empirical mode decomposition technique. The lateral load distribution was estimated using the extracted static displacement component and compared with the lateral load distribution factor measured in the static loading test.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.269-272
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• 2008

The seismic fragility curves of a structure represents the probability of exceeding the prescribed structural damage given various levels of ground motion intensityand the seismic fragility curve is essential to evaluation of structural performance and assessment of risk and loss of structures. The purpose of this paper is to develop seismic fragility functions for bridge structures in Koreaby reviewing those of advanced countries. Therefore, at first, we investigated development conditions of the seismic fragility functions. And the next highway bridges in Korea are classified into a number of categories and several typical bridges are selected to estimate seismic fragilities for using this analysis method in Korea. Finally, fragility curves for PSC Box girder bridge are estimated. The results show that the bridge classification and damage state play an important role in estimation of seismic damage and seismic fragility analysis for bridge structures.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.147-160
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• 2007

In this paper, we described the aeroelastic full-bridge model tests that were conducted to investigate the effect of alternative temporary stabilizing measures for thecable-stayed bridge during construction to ensure aerodynamic stability in the event of a typhoon or similar disasters. The effect of alternative temporary stabilizing measures was investigated through various configurations on two cable-stayed bridges with a main span of 475 m and 230 m, respectively. To investigate the bridge's aerodynamic behaviour and dynamic wind force during construction, the deflections at the end of the cantilever, the accelerations atthe top of the pylon and the moments at the lower part of the pylon were measured. As the result, the system with two sets of vertical cables per cantilever seemed to be the overall most effective solution, but the system with single vertical cable may also work. The combined system using the caisson support and vertical cables and the system with two sets of inclined cables per cantilever on the same anchor block may also be a solution. The inclined cables from the caisson to the girder were effective for some early stages of erecting the deck.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.371-382
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• 2006

A buffeting analysis is utilized for the estimation of aerodynamic vulnerability of a cable-stayed bridge due to upcoming wind turbulences. The buffeting analysis requires several input parameters such as structural parameters, aerodynamic parameters, and aero-elastic parameters. This study is motivated to estimate the sensitivity of these parameters on buffeting responses. The Seohae bridge is selected as an example bridge. The investigated parameters consist of the inclination of lift and drag coefficient of stiffening girder section, exponential decay factors of span-wise distributed wind turbulences, roughness length, spectra of wind velocity fluctuation, and structural damping. The buffeting response showed high dependency on the input parameters. As conclusions, the importance of parameter selection is emphasized. A further study is also proposed for more general conclusions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2A
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• pp.137-148
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• 2010

This study proposes the optimal ratio of vertical load-carrying capacity (${\beta}$) by investigating structural performances and economic efficiency in the extradosed bridges. Without design standards for the extradosed bridge, Japanese design standards have been used domestically. For the design live load, DL24 is found to be more adequate than DB24. Using the DL24 load, parameter studies are carried out. The parameters are 'main tower height', 'main girder stiffness', and 'cable arrangement'. As a result, it is found that one side cable-stayed extradosed bridges are more economical than double side cable-stayed extradosed bridges. This study also shows that when the ratio of vertical load-carrying capacity(${\beta}$) is 30~50% in the extradosed bridge with the ratio of tower height to main span length 1/6, the extradosed bridge is most economical because of the cable stress less than the allowable stress.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.101-109
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• 2009

An algorithm is proposed for estimating dynamic displacements of a bridge by using FBG sensors and by superposing some measurable low modes. Modal displacements are obtained from the beam theory and the generalized coordinates are deduced from the strains measured by FBG sensors. By considering flexural and torsional modes occurred in bridges only as flexural modes of a simply supported beam by separating a bridge into multiple girders or parts, the proposed algorithm can be applied to various types of bridges. Guidelines are provided theoretically for determining the number of modes and the number of strain gages to be used. The proposed algorithm has been examined through simulation studies on various types of bridges, laboratory experiments on a model bridge, and field tests on a simple span PC Box girder bridge. Through the simulation study, the effects of the error in the vibration modes and measurement noise on estimating the dynamic displacements are analyzed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.217-224
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• 2005

A methodology of selecting an optimal model is proposed for applying a frequency-domain SI method effectively. Instead of using a reduced finite element model, a reasonably detail finite element model is established first and then the model is identified. To satisfy the identifiability criterion, a parameter grouping scheme is applied to control the number of unknowns. Among the simulated member grouping cases, an optimal model is selected as the one with the minimal statistical error. The proposed approach has been examined through simulation studies on a single span box-girder bridge.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.23-24
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• 2010

In this research, the comparison and analysis of domestic prestressed concrete bridges were performed with major variations of superstructure type, and span lengths using the 'current status of roadbridge and tunnel' informations provided by MLTM and STATISTICS KOREA. As a result of analysis, steel box girder bridges with 50~100m span length represent about 76% of bridges, but prestressed concrete bridges represent a relatively smaller percentage. In order to replace steel box girder bridges with prestressed concrete bridges, it is necessary to develop prestressed concrete bridges with high-strength tendons and concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.961-966
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• 2003

In recent, the design of diaphragm which is representative disturbed region in PSC box girder bridge have been performed according to the empirical method or beam theory. But, these methods couldn't be described the behavior of the end diaphragm, and placed reinforcements accurately. As the compressive stress transferred by the web concentrated on the lower parts of diaphragm, it was demonstrated that the basic assumption of 2-D strut-and-tie model for the diaphragm that the compressive stress acts on the upper parts of the diaphragm is wrong. Meanwhile, in this research, after analyzing the variables of end diaphragm, the 2-D strut-and-tie models appropriate to each cases are proposed. And, the problems of 2-D strut-and-tie model were analyzed, so 3-D strut-and-tie model is proposed as well. There is no codes which include the demonstration of safety of 3-D strut-and-tie model. Hence, for nodes, the stresses at the elements which included the singular node in strut-and-tie model were investigated using the finite element analysis. And, the stress states of strut has one direction, so effective stresses were considered at the stage, dimensioning of the model. From the results, 3-D strut-and-tie model could predict the behavior of end diaphragm accurately, and design of reinforcement could be performed economically.