• Structural Engineering and Mechanics
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• v.52 no.5
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• pp.1019-1032
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• 2014

Rails are key elements in railway superstructure since these elements receive directly the train load transmitted by the wheels. Simultaneously, rails must provide effective stress transference to the rest of the track elements. This track element often deteriorates as a consequence of the vehicle passing or manufacturing imperfections that cause in rail several defects. Among these rail defects, transverse cracks highlights and are considered a severe pathology because they can suddenly trigger the rail failure. This study is focused on UIC-60 rails with transverse cracks. A 3-D FEM model is developed in ANSYS for the flawless rail in which conditions simulating the crack presence are implemented. To account for the inertia loss of the rail as a consequence of the cracking, a reduction of the bending stiffness of the rail is considered. The numerical models have been calibrated using the first four bending vibration modes in terms of frequencies. These vibration frequencies have been obtained using the Experimental Modal Analysis technique, studying the changes in the modal parameters of the rails induced by the crack and comparing the results obtained by the model with experimental results. Finally, the calibrated and validated models for the single rail have been implemented in a complete railway ballasted track FEM model in order to study the static influence of the cracks on the rail deflection caused by a load passing.

• Steel and Composite Structures
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• v.12 no.5
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• pp.379-393
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• 2012

Many steel bridge infrastructures in the world are getting older, and a large number of these structures are in need of maintenance, rehabilitation or replacement. Most of them are subjected to corrosion due to exposure to aggressive environmental conditions and inadequate maintenance, causing reduction of their carrying capacities. In order to have an adequate bridge management, it is of paramount importance to develop an efficient, accurate and rapid condition assessment method which can be used to make reliable decisions affecting the cost and safety. Therefore, a simple and accurate method of calculating remaining yield and tensile strength by using a concept of representative effective thickness with correlation of initial thickness and maximum corroded depth is proposed in this study, based on the results of many tensile coupon tests of corroded plates obtained from a steel plate girder with severe corrosion, used for about 100 years. Furthermore, a strength reduction diagram which will be very useful for bridge inspection engineers to make rational decisions about the maintenance management of aged steel bridge infrastructures is presented.

• Resources Recycling
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• v.17 no.1
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• pp.73-79
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• 2008

Along with the increased social infrastructures and reconstruction, the demand for aggregate, which is used in concrete, has rapidly increased. However, there are problems due to the exhaustion of natural aggregate resources, and strict restrictions. In this study, the possibility of using rapid chilled steel slag as a substitutive material of fine aggregate is determined from the property test and mechanical test for the concrete that is made with rapid chilled steel slag, which highly decreases the free CaO, the main problem of the steel slag.

• Geomechanics and Engineering
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• v.24 no.6
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• pp.559-572
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• 2021

This research presents the monitoring results and their interpretation on load sharing of the pile foundation during the construction of a high-rise (124 m in height) building in Bangkok, in soft clayey ground. Axial forces in several piles, pore water pressure and earth pressures beneath the raft in a tributary area were monitored through the construction period of the building. The raft of the pile foundation in soft clayey ground can share the load up to 10-20% even though the foundation was designed using the conventional approach in which the raft resistance is ignored. The benefit from the return of ground water table as the uplift pressure is recognized. A series of parametric study by 3D-FEA were carried out. The potential of utilizing the piled raft system for the high-rise building with underground basement in soft clayey ground was preliminarily confirmed.

• Smart Structures and Systems
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• v.30 no.6
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• pp.583-599
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• 2022

In this paper, a multi-objective wireless sensor network configuration optimization method is proposed. The proposed method aims to determine the optimal information and lifespan wireless sensor network for structural health monitoring of large-scale infrastructures. In particular, cluster-based wireless sensor networks with multi-type of sensors are considered. To optimize the lifetime of the wireless sensor network, a cluster-based network optimization algorithm that optimizes the arrangement of cluster heads and base station is developed. On the other hand, based on the Bayesian inference, the uncertainty of the estimated parameters can be quantified. The coefficient of variance of the estimated parameters can be obtained, which is utilized as a holistic measure to evaluate the estimation accuracy of sensor configurations with multi-type of sensors. The proposed method provides the optimal wireless sensor network configuration that satisfies the required estimation accuracy with the longest lifetime. The proposed method is illustrated by designing the optimal wireless sensor network configuration of a cable-stayed bridge and a space truss.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.2
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• pp.1-11
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• 2017

The analysis of baseflow contribution is very significant in Korea because most rivers have high variability of streamflow due to the monsoon climate. Recently, the importance of such analysis is being more evident especially in terms of river management because of the changing pattern of rainfall and runoff resulted from climate change. Various baseflow separation methods have been developed to separate baseflow from streamflow. However, it is very difficult to identify which method is the most accurate way due to the lack of measured baseflow data. Moreover, it is inappropriate to analyze the annual baseflow contribution for Korean rivers because rainfall patterns varies significantly with the seasons. Thus, this study compared the baseflow contributions at various time-scales (annual, seasonal and monthly) for the 4 major river basins through BFI (baseflow index) and suggested baseflow contribution of each basin by the BFI ranges searched from different baseflow separation methods (e.g., BFLOW, HYSEP, PART, WHAT). Based on the comparison of baseflow contributions at the three time scales, this study showed that the baseflow contributions from the monthly and seasonal analysis are more reasonable than that from the annual analysis. Furthermore, this study proposes that defining BFI with its range is more proper than a specific value for a watershed, considering the difference of BFIs between various baseflow separation methods.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.1-9
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• 2022

De -icing salts have been used commonly in areas where snow or ice is a seasonal safety hazard for roadway, however, the salts is one of main causes on serious deterioration of road infrastructures in crowded urban city like Seoul. In order to establish maintenance strategy of road infrastructures under de-icing salts laden environment, it is necessary to examine environmental characteristics and its response to the existing facilities. The purpose of this study is to evaluate the deterioration environment of road infrastructures. Additional purpose is to develop a design model and details for durability design of infrastructures under de-icing salts laden environment, considering mainly a build-up rate of surface chlorides. Concentration of external chloride solution and surface chloride content were calculated at the level of average de-icing salts for 5 years, ratio of auxiliary road of 17.5 to 30%, and effective exposure area to snow 50 to 80%. The chloride build-up rate was 0.073 ~ 0.077% / year and the maximum surface chloride content was calculated to be 2.2 ~ 2.31% by concrete wt. This study is expected to be used for establishing integrated strategy of road infrastructures, such as predicting chloride profiles or degree of chemical corrosion to exposure concrete.

• Smart Structures and Systems
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• v.33 no.2
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• pp.93-103
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• 2024

Despite the rapid development of sensors, structural health monitoring (SHM) still faces challenges in monitoring due to the degradation of devices and harsh environmental loads. These challenges can lead to measurement errors, missing data, or outliers, which can affect the accuracy and reliability of SHM systems. To address this problem, this study proposes a classification method that detects anomaly patterns in sensor data. The proposed classification method involves several steps. First, data scaling is conducted to adjust the scale of the raw data, which may have different magnitudes and ranges. This step ensures that the data is on the same scale, facilitating the comparison of data across different sensors. Next, informative features in the time and frequency domains are extracted and used as input for a deep neural network model. The model can effectively detect the most probable anomaly pattern, allowing for the timely identification of potential issues. To demonstrate the effectiveness of the proposed method, it was applied to actual data obtained from a long-span cable-stayed bridge in China. The results of the study have successfully verified the proposed method's applicability to practical SHM systems for civil infrastructures. The method has the potential to significantly enhance the safety and reliability of civil infrastructures by detecting potential issues and anomalies at an early stage.

• Korean Journal of Construction Engineering and Management
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• v.17 no.3
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• pp.134-142
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• 2016

Main infrastructures, such as levee, dam, bridge, road, etc., are very important due to not only the means of support for social and industrial activities in normal situation but also the means of protection of life and property during disaster occurrence. In spite of this importance of infrastructures, however, any disaster management systems that actively use these infrastructures are not developed yet. Moreover, infrastructures are not usually included in emergency action plans, thus it occurs second and third impact on communities and industries due to collapsing or damage of infrastructures. Therefore, the authors in this paper analyzed previous research, SWOT, STEEP, and patents and technical journals and conducted a technology need survey ni order to understand the trend of disaster management system as well as suggest main research fields and detail research items. The results of this paper will be a foundation of developing an advanced infrastructure integrated system of maintenance and disaster mitigation and contribute our nation to have an active response system by using infrastructure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6D
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• pp.655-662
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• 2010

As the national competitive power indicator, the infrastructures have been constructed with government's SOC budgets. However, even SOC budget is decreased, Public-Private Partnership Project (PPP project) has been introduced to solve demands on extending infrastructures, and among PPP projects, road projects take high portions. This study analyzes the operation & management item of financial model which is connected to the O&M cost and project proposal of previously proposed road project and analyzes the Korea Expressway Co.,'s project cost items and O&M tasks to reflect the characteristics of road projects. Based on results, this study suggests necessity of the O&M cost breakdown structure and the cost calculation standard on each cost item. Also, for the existing task execution tools, O&M cost calculation tool and finance analysis task tool will be integrated, and the system is suggested web-based system. Thus, it is expected that it contributes to the securing overall business values on PPP project and expending profit-base infrastructures.