• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.136-149
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• 2011

Large portion of the domestic bridges are slab bridges reflecting the geographical characteristic of the country, where exists lots of inclines and small winding brooks. Many of the slab bridges are damaged and superannuated as they become obsolete. Deterioration is accelerated when the traffic density becomes large and heavy vehicles pass frequently. A strengthening method for deteriorated slab bridges was studied in this work. The examined net-type strengthening method uses both longitudinal and transverse prestressing for strengthening. In this way, the deflection at the center of the slab can be better controlled, and consequently, the slab is more efficiently strengthened. Three slab specimens were fabricated for the experimental test and subjected to three different loading conditions, and the load bearing capacities and deflections of slabs were examined. Flexural stiffness of slabs increased by 30.7~107.3%, and deflection of slabs decreased by 27.6~52.2% after net-type strengthening. The net-type prestressing is efficient to the strengthening for the center of a slab, and its efficiency is also valid under eccentric loadings. Since extra prestress forces can be added in the future, if necessary, the net-type strengthening system is advantagous for the maintenance and repair of slab bridges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.71-80
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• 2010

Bridge deck is directly influenced by environment and vehicle load, it is easily damaged so that it requires an appropriate repair and retrofit. Therefore, developing a bridge deck with high durability is necessary in order to minimize the maintenance of bridge deck and use it to its design life. In this study, static test was carried out to evaluate a fatigue capacity of steel-concrete composite deck, which was newly developed by supplementing problems of existing reinforced concrete deck. Based on results from the static test, fatigue load was decided, and fatigue test was conducted under the constant amplitude repeated load. From the fatigue tests, the S-N curve regarding principle structural details of composite deck was made, and characteristics of fatigue behavior was estimated by comparing and evaluating it with fatigue design criteria. In addition, fatigue design guideline was presented. As a result, it is found that each structural details of composite deck proposed by this study, such as upper flange of corrugated steel plate and middle section of it, shear connector and lower flange of corrugated steel plate, is satisfying the fatigue strength.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.5
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• pp.301-308
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• 2021

It is important to develop a digital SOC (Social Overhead Capital) maintenance system for preemptive maintenance in response to the rapid aging of social infrastructures. Abnormal signals induced from structures can be detected quickly and optimal decisions can be made promptly using IoT sensors deployed on the structures. In this study, a digital SOC monitoring system incorporating a multimetric IoT sensor was developed for long-term monitoring, for use in cloud-computing server for automated and powerful data analysis, and for establishing databases to perform : (1) multimetric sensing, (2) long-term operation, and (3) LTE-based direct communication. The developed sensor had three axes of acceleration, and five axes of strain sensing channels for multimetric sensing, and had an event-driven power management system that activated the sensors only when vibration exceeded a predetermined limit, or the timer was triggered. The power management system could reduce power consumption, and an additional solar panel charging could enable long-term operation. Data from the sensors were transmitted to the server in real-time via low-power LTE-CAT M1 communication, which does not require an additional gateway device. Furthermore, the cloud server was developed to receive multi-variable data from the sensor, and perform a displacement fusion algorithm to obtain reference-free structural displacement for ambient structural assessment. The proposed digital SOC system was experimentally validated on a steel railroad and concrete girder bridge.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.1
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• pp.55-66
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• 2001

All kinds of disasters are occurring for several reasons in modern cities. So, We need the disaster management system to deal with them at this point that Those disasters are getting larger and more frequent. We organized the database into three categories; the traffic accident database on traffic accidents that is recognized as a typical disaster resulting from vehicles's increasement rapidly in modern urban life, the gas explosion disaster database on gas explosion that causes to fatal damage through broad areas, and the bridge management database that contains bridge resource information and repair record. In this study, we developed the Disaster Management System using the wireless internet GIS that can access the database and identify field information for the accident area in emergency situation as well as can modify and update the database in field directly, so that can cope with the disaster situations effectively.

• Journal of the Korean Society for Railway
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• v.14 no.3
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• pp.271-275
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• 2011

According to governmental policies for green growth, the increase in the traffic volume of railroad is a representative method to reduce total greenhouse gas (GHG) emitted from transport. Comprehensive assessment for the GHG emission of railroad has been studied to compare the difference of transport modes just in the operating step excluded the construction step. The purpose of this study was to evaluate GHG emissions in railroad construction sector. The targets were some construction works for civil, track, building, and electric system in A line. The GHG emission source of constructing railroad infrastructure was mainly the energy consumption of heavy equipments. As a result, the civil construction sector showed more than 96% of total GHG emissions and its specific GHG emission was 2.191 ton $CO_2e/m$. Also, the specific GHG emissions of civil construction works were of the order: earthworks > tunnels > bridges > station. In future, it will be required to calculate the overall GHG emission of railroad through life cycle approaches including operation, maintenance and disposal step.

• Journal of the Korean Society for Railway
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• v.13 no.5
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• pp.521-527
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• 2010

The Paved Track is applied to reduce maintenance cost of conventional line. The Paved Track could be used in all types of lines including earthwork, bridge, tunnel and turnout sections. In case of earthwork section, the construction joint is the most critical factor to track durability. The construction joint does not affect to the track structure directly, but the gap due to discontinuity of slabs may affect to the long-term serviceability. To evaluate this problem, the accelerated track test has been performed on the construction joint and the middle part to of the real scale Paved Track. The purpose of this test is that evaluate the vulnerability of construction joint section comparing the trends of settlement and earth pressure under repeated loads of construction joint with those of the middle slab part.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.3
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• pp.225-232
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• 2008

Overload vehicles operate damage to road, bridge, and then increasing in maintenance and repair cost because structures are reduced durability. The existing regulation systems have many problems and need coping measure. Therefore, this paper organized Ubiquitous sensor network system for development of intelligent auto overload vehicle regulation system about high speed vehicles, also axial load WIM sensor was selected by indoor experiment through wireless protocol. And we examined possibility U-load auto overload vehicle regulation system through experiment of the transmission and reception distance. If this system will apply to road and bridge, might be effective for economy and convenience through establishment of U-IT system. And high speed vehicle that was amalgamate IT technology and existing overload regulation problems, also tested wireless sensor for USN organization. This experiment aim to organize system interface for user through perfection man-less, wireless system of Internal/External Network from high speed WIN sensor with USN organization. Accordingly, it is necessary experimentation through Test Bed for constitution External network and application of actually regulations using WCDMA/HSDPA.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.587-596
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• 2006

A half portion of Korean railway bridges depends on the type of steel plate girder bridge. Since these bridges have been built in the early stage of Korean economical boom, numerous maintenance effort suffers from aging and progressive degradation issues at present. In accordance with these efforts, this paper would like to address the detailed analyses of thin steel plates with bolts in order to simulate the connection regions of steel plate girder bridge. The fundamental modal analysis, transient dynamic analysis with 3D piezoelectric element in open circuit loop and signal process with aids of TOF(time of flight) and WC(wavelet coefficient) are extensively discussed.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.17-26
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• 2010

Maintenance of the roads and bridges is a major issue for all road administrators around the world, and various initiatives are being implemented in each region for the purpose of controlling the ever increasing road maintenance cost while ensuring the safety of the vehicles driving. Efforts for such initiatives have also been made in Asia and initiatives for managing heavy-weight vehicles have recently gained momentum in Korea and Japan. We have developed a technology for unevenly installing bar-shaped sensors (piezo quartz sensors) to enable dynamic axle load measurement at a highly accurate level, and have estimated our measurement accuracy of axle load/gross weight, etc. on an actual road. The measurement accuracy of the axle load/gross weight varies significantly depending on the number of sensors installed. In our implementation, the target accuracy was set to below ${\pm}5%$ for gross weight measurement so that automatic regulation can be applied. We have achieved our target by installing 8-point measurement system. However, to have this technology widely accepted, it was necessary to reduce the system size so that it can be easily implemented. Therefore, we have estimated the relationship between the measurement accuracy and the system size (number of measurement points), and have come up with the proposal of 3-point measurement as an optimum number of measurement points, and have estimated its performance on an actual road. Additionally, we evaluated the relationship between the measurement accuracy and vehicle velocity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.254-260
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• 2017

The service life of civil infrastructure needs to be maintained or extended through appropriate inspections and maintenance planning, which results from the optimization process. A multi-objective optimization process can lead to more rational and flexible trade-off solutions rather than a single-objective optimization for the service life management of civil infrastructure. Recent investigations on the service life management of civil infrastructure were generally based on minimizing the life-cycle cost analysis and maximizing the structural performance. Various objectives for service life management have been developed using novel probabilistic concepts and methods over the last few decades. On the other hand, an increase in the number of objectives in a multi-objective optimization problem can lead to difficulties in computational efficiency, visualization, and decision making. These difficulties can be overcome using the objective reduction approach to identify the redundant and essential objectives. As a result, the efficiency in computational efforts, visualization, and decision making can be improved. In this paper, the multi-objective optimization using the objective reduction approach was applied to the service life management of concrete bridges. The results showed that four initial objectives can be reduced by two objectives for the optimal service life management.