• International conference on construction engineering and project management
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• 2009.05a
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• pp.449-456
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• 2009

Image processing has been applied to steel bridge defect recognition since 1990s. Compare to human visual inspection, image processing provides a more objective and accurate way of assessment. Since shade and shadow may sometimes occur when taking bridge coating images, non-uniform illumination problems should be considered. By means of color image processing, this paper aims to mitigate the illumination effect for bridge coating assessment. Furthermore, the adaptable ellipse method (AEM) is proposed to recognize mild rust colors. Finally, AEM will be compared to the K-Means algorithm, a popular recognition method, to show its advantage.

• Structural Engineering and Mechanics
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• v.46 no.5
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• pp.615-627
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• 2013

One of the most common defects in reinforced concrete bridge decks is corrosion of steel reinforcing bars. This invisible defect reduces the deck stiffness and affects the bridge's serviceability. Regular monitoring of the bridge is required to detect and control this type of damage and in turn, minimize repair costs. Because the corrosion is hidden within the deck, this type of damage cannot be easily detected by visual inspection and therefore, an alternative damage detection technique is required. This research develops a non-destructive method for detecting reinforcing bar corrosion. Experimental modal analysis, as a non-destructive testing technique, and finite element (FE) model updating are used in this method. The location and size of corrosion in the reinforcing bars is predicted by creating a finite element model of bridge deck and updating the model characteristics to match the experimental results. The practicality and applicability of the proposed method were evaluated by applying the new technique to a two spans bridge for monitoring steel bar corrosion. It was shown that the proposed method can predict the location and size of reinforcing bars corrosion with reasonable accuracy.

• Journal of Welding and Joining
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• v.16 no.6
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• pp.77-85
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• 1998

Effects of non-cleaning and cleaning fluxes on the wetting properties and defects at flow soldered joints were investigated. Non-cleaning flux (R-type of 3.3% solid content) and cleaning flux (RMA-type of 15% solid content) were used. Wetting test was accomplished by wetting balance method with changing surface state of wetting specimen, CU. Sn-37%Pb solder was used for wetting test and flow soldering. As experimental results, the wetting time for vertical force from the surface tension being zero was mainly affected by surface state of the wetting specimen. Non-cleaning flux had a good wettability compared with cleaning flux. In case of non-cleaning flux, conveyor speed had a great affection to defects of bridge, icicle, and poor solder.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.267-273
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• 2001

In this study, welding phenomena involved in formation of penetrators during high frequency electric resistance welding were investigated. High speed cinematography of the process revealer that a molten bridge between neighboring skelp edges forms at apex point and travels along narrow gap toward to welding point at a speed ranging from 100 to 400 m/min. The bridge while moving along the narrow gap swept away oxide containing molten metal from the gap, providing oxide-free surface for a forge-welding at upsetting stand frequency of the budge formation, travel distance and speed of the bridge were affected by the heat input rate into strip. The travel distance and its standard deviation were found to have a strong relationship with the weld defect density. Based on the observation, a new mechanism of the penetrator formation during HF ERW process is proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.1
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• pp.98-107
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• 1998

There are many weld defects such as surface crack, lack of fusion, and imcomplete penetration in the butt joint of the existing steel bridges. The crack-like defects may significantly reduce the fatigue life of the structure. This paper presents the procedure and the results of the fatigue assessment of the butt joints with weld defect in the existing steel girder bridge. The butt joints with imcomple penetration were instrumented with strain gages to determine the stress histogram under normal traffic. Based on the measured stress histogram the crack propagation analyses were performed for the fatigue assesment. By using the suggested procedure and methodology, one can decide the time of periodic inspection and the necessity of repair of the butt joints with serious weld defects in the existing steel bridge.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.815-820
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• 2011

The railway bridge of the domestic still has been used steel base such as sperical bearing and pot bearing widely. However, the bearing of steel series is occured corrosion frequently, reduced durability and raised maintenance cost excessively due to the nature of the material. If the elastomeric bearing which is widely used in highway bridge is applied to the railway bridge, it will be able to compensate this defect a lot. In order to apply to the railway bridge used for highway bridge, is needed the control of the bridge ends deflection, lateral displacement and negative reaction. Therefore, the elastomeric bearing can be applied to the railway bridge enough, if installed negative reaction key for control of the bridge ends deflection, improved shear wedge performance for control of the lateral force, adjust the thickness of the elastomeric pad for the minimize deflection, in addition, can be economic design of sub-structures due to damping effect.

• Smart Structures and Systems
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• v.13 no.6
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• pp.901-925
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• 2014

The reliability of a Bridge management System depends on the quality of visual inspection and the reliable estimation of bridge condition rating. However, the current practices of visual inspection have been identified with several limitations, such as: they are time-consuming, provide incomplete information, and their reliance on inspectors' experience. To overcome such limitations, this paper presents an approach of automating the prediction of condition rating for bridges based on digital image analysis. The proposed methodology encompasses image acquisition, development of 3D visualization model, image processing, and condition rating model. Under this method, scaling defect in concrete bridge components is considered as a candidate defect and the guidelines in the Ontario Structure Inspection Manual (OSIM) have been adopted for developing and testing the proposed method. The automated algorithms for scaling depth prediction and mapping of condition ratings are based on training of back propagation neural networks. The result of developed models showed better prediction capability of condition rating over the existing methods such as, Naïve Bayes Classifiers and Bagged Decision Tree.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.2
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• pp.267-275
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• 2023

As aged infrastructures have been increased, the importance of accurate maintenance costs and proper budget allocation for infrastructure become prominent under limited resources. This study proposed a mapping algorithm between representative defects, repair methods, and the estimated maintenance costs for concrete bridges. In this regard, using BMS (Bridge Management System) data analysis, bridge repair methods were classified and matched with defects according to their locations, types, and sizes. In addition, the maintenance costs were estimated based on the amount of work-load and quantity per unit using CSPR (Cost Standard Production Rate). As a result, the level of accuracy was an average of 85.1 % compared with the actual bill of quantity for Seoul bridge maintenance. The accuracy of maintenance costs is expected to be enhanced by considering the various site conditions such as pier height, extra charge conditions, additional equipment, etc.

• Bulletin of the Korean Chemical Society
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• v.31 no.1
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• pp.162-167
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• 2010

We investigated the adsorption and desorption characteristics of benzene molecules on $Si(001)-2{\times}n$ surfaces using a variable-low temperature scanning tunneling microscopy. When benzene was adsorbed on a $Si(001)-2{\times}n$ surface at a low coverage, five distinct adsorption configurations were found: tight-binding (TB), standard-butterfly (SB), twisted-bridge, diagonal-bridge, and pedestal. The TB and SB configurations were the most dominant ones and could be reversibly interconverted, diffused, and desorbed by applying an electric field between the tip and the surface. The population ratios of the TB and SB configurations were affected by the benzene coverage: at high coverage, the population ratio of SB increased over that of TB, which was favored at low coverage. The desorption yield decreased with increasing benzene coverage and/or density of vacancy defect. These results suggest that the interaction between the benzene molecules is important at a high coverage, and that the vacancy defects modify the adsorption and desorption energies of the benzene molecules on Si(001) surface.

• Journal of Welding and Joining
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• v.18 no.3
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• pp.68-75
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• 2000

The incomplete penetration(IP) discontinuity in butt joint weld, which is detected during safety analysis of the steel bridge by nondestructive evaluation(NDE) method, is classified as unacceptable defect according to the NDE codes and standards. In fact, there are a little allowance in butt joint weld in the view point of design criterion, and also detected IP discontinuity should be classified and evaluated for the fatigue strength and residual life estimation. In this study, we performed fatigue test to evaluate the fatigue strength of high strength steel(SWS490A) containing IP discontinuities in various size, the results compared and classified according to the bridge construction standard specification which published by korea administration of construction and traffic. Experimental results could be used to evaluate and estimate the IP discontinuities considering different stress range in butt joint bridge weld during periodic safety inspection.