• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.4
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• pp.129-137
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• 1999

Assessment of structural damage is a complex subject imbued with uncertainty and vagueness. This complexity arises from the use of subjective opinion and imprecise numerical data. Recently several active researches have been performed using new methods such as neural network approach or on-line damage detection. In this paper, Damage assessment (diagnosis) of the concrete bridges is studied by a new approach utilizing a neural fuzzy system that combined a neural network and a fuzzy logic. By applying this system to actual in-service bridges, it has been verified that the neural fuzzy method is effective for the bridge diagnosis.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.1
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• pp.9-18
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• 2014

The purpose of this study is to investigate the seismic behavior of hollow reinforced concrete bridge column systems with reinforcement details for material quantity reduction and to provide the details and reference data. Five hollow reinforced concrete bridge columns were tested under a constant axial load and a cyclically reversed horizontal load. The accuracy and objectivity of the assessment process can be enhanced by using a sophisticated nonlinear finite element analysis program. The adopted numerical method gives a realistic prediction of seismic performance throughout the loading cycles for several the investigated test specimens. This study documents the testing of hollow reinforced concrete bridge column systems with reinforcement details for material quantity reduction and presents conclusions based on the experimental and analytical findings.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.85-93
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• 2005

In order to effective transportation of goods & smooth traffic in west sea area, it is a plan to build Pyeongtaek bridge. Basically ship-handling operators have a mental difficulty and hazardous for navigation under bridge which is constructed across on the fairway. Therefore this study aims to propose the traffic safety assessment of navigation under the bridge by using full mission ship-handling simulator and also investigate the bridge design regulations of certain countries on the fairway.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.422-430
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• 1998

This paper presents the results of a major parametric study on the collapse cause of the Sungsoo Grand Bridge, a Gerber-type continuous truss bridge, which had collapsed just at the 15th year since opening to traffic. Among the various collapse causes such as poor design, poor welding, poor maintenance, and heavy traffic loads, this study focuses on the collapse cause assessment incorporating the effects of braket and H-beam members right below the expansion joint of the suspended truss. A local FEM analysis using fine shell elements is carrided out for the more precise estimation of stress range of the vertical pin-connected hanger whose fatigue fracture triggered the collapse of the bridge. Both the conventional S-N approach and the Ang-Munse's fatigue reliability method are used for the evaluation of the fatigue life and fatigue failure probability for the assessment based on all the available results of various field and labolatory tests. From these observations, It may be affirmatively stated that the effects of bracket and H-beam members accelerated the fatigue failure, and thus should be regarded as one of major causes that triggered the bridge collapse

• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.187-194
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• 2016

It is necessary to determine reliability indexes of existing railway bridges prior to setting up a proper target reliability index that can be used to introduce a reliability based limit state design method to design practice. Reliability is evaluated for a six PSC-I girder railway bridge, which is one of many representative types of double-track railway bridges. The reliability assessment is carried out for an edge girder subjected to bending moment. In the assessment, the flexural resistance and the fixed-load effect were obtained using existing statistical values from previous research on the introduction of limit state design to road bridge design. On the other hand, the live-load effect was determined using statistical values obtained from field measurement for the Joong-ang corridor, on which heavy freight trains are frequently passing. The reliability assessment is performed by AFOSM(Advanced First Order Second Moment method) for the limit state equation, and a sensitivity analysis for the reliability is performed for each factor of the load and resistance effects.

• Steel and Composite Structures
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• v.27 no.3
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• pp.327-335
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• 2018

This paper presents structural assessment of a steel railway bridge for current condition using modal parameter to upgrade finite element modeling in order to gather accurate result. An adequate monitoring, such as acceleration, displacement, strain monitoring, is important tool to understand behavior and to assess structural performance of the structure under surround vibration by means of the dynamic analysis. Evaluation of conditions of an existing steel railway bridge consist of 4 decks, three of them are 14 m, one of them is 9.7 m, was performed with a numerical analysis and a series of dynamic tests. Numerical analysis was performed implementing finite element model of the bridge using SAP2000 software. Dynamic tests were performed by collecting acceleration data caused by surrounding vibrations and dynamic analysis is performed by Operational Modal Analysis (OMA) using collected acceleration data. The acceleration response of the steel bridge is assumed to be governing response quantity for structural assessment and provide valuable information about the current statute of the structure. Modal identification determined based on response of the structure play significant role for upgrading finite element model of the structure and helping structural evaluation. Numerical and experimental dynamic properties are compared and finite element model of the bridge is updated by changing of material properties to reduce the differences between the results. In this paper, an existing steel railway bridge with four spans is evaluated by finite element model improved using operational modal analysis. Structural analysis performed for the bridge both for original and calibrated models, and results are compared. It is demonstrated that differences in natural frequencies are reduced between 0.2% to 5% by calibrating finite element modeling and stiffness properties.

• Coupled systems mechanics
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• v.9 no.4
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• pp.359-379
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• 2020

Due to susceptibility of bridges in the past earthquakes, vulnerability assessment and strengthening of bridges has gained a particular significance. The objective of the present study is to employ an analytical method for the development of fragility curves, as well as to investigate the effect of strengthening on the RC box-girder bridges. Since fragility curves are used for pre-and post-earthquake planning, this paper has attempted to adopt the most reliable modeling assumptions in order to increase the reliability. Furthermore, to acknowledge the interaction of soil, abutment and pile, the effect of different strengthening methods, such as using steel jacketing and FRP layers, the effect of increase in the bridge pier diameter, and the effect of vertical component of earthquake on the vulnerability of bridges in this study, a three-span RC box-girder bridge was modeled in 9 different cases. Nonlinear dynamic analyses were carried out on the studied bridges subjected to 100 ground motion records via OpenSEES platform. Therefore, the fragility curves were plotted and compared in the four damage states. The results revealed that once the interaction of soil and abutment and the vertical component of the earthquake are accounted for in the calculations, the median fragility is reduced, implying that the bridge becomes more vulnerable. It was also confirmed that steel jackets and FRP layers are suitable methods for pier strengthening which reduces the vulnerability of the bridge.

• Journal of Navigation and Port Research
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• v.32 no.5
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• pp.321-326
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• 2008

Recently the large sea bridge's construction crossing harbor and main ship's route have been propelled in the domestic so that it is active for the smoothly traffic flow of inland transportation and road user's convenience. However, it can bring about the trouble to ensure marine traffic safety if it is built that sea bridge's construction sets to an economy principle in the extension of the land road system. We're adopting Ship Handling Simulation in representative method for the influence assessment of marine traffic safety and danger elements beforehand. This research attempts to show the problems through the comparison and analysis of the reports relating to the sea bridge construction for 4 organization possessing Ship Handling Simulation. Finally, We offer the necessity of standardization on performing and assessment method of simulations.

• Structural Engineering and Mechanics
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• v.54 no.2
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• pp.257-289
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• 2015

Shear connectors are generally used to link the slab and girders together in slab-on-girder bridge structures. Damage of shear connectors in such structures will result in shear slippage between the slab and girders, which significantly reduces the load-carrying capacity of the bridge. Because shear connectors are buried inside the structure, routine visual inspection is not able to detect conditions of shear connectors. A few methods have been proposed in the literature to detect the condition of shear connectors based on vibration measurements. This paper proposes a different dynamic condition assessment approach to identify the damage of shear connectors in slab-on-girder bridge structures based on power spectral density transmissibility (PSDT). PSDT formulates the relationship between the auto-spectral densities of two responses in the frequency domain. It can be used to identify shear connector conditions with or without reference data of the undamaged structure (or the baseline). Measured impact force and acceleration responses from hammer tests are analyzed to obtain the frequency response functions at sensor locations by experimental modal analysis. PSDT from the slab response to the girder response is derived with the obtained frequency response functions. PSDT vectors in the undamaged and damaged states can be compared to identify the damage of shear connectors. When the baseline is not available, as in most practical cases, PSDT vectors from the measured response at a reference sensor to those of the slab and girder in the damaged state can be used to detect the damage of shear connectors. Numerical and experimental studies on a concrete slab supported by two steel girders are conducted to investigate the accuracy and efficiency of the proposed approach. Identification results demonstrate that damages of shear connectors are identified accurately and efficiently with and without the baseline. The proposed method is also used to evaluate the conditions of shear connectors in a real composite bridge with in-field testing data.

• Journal of Navigation and Port Research
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• v.29 no.1 s.97
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• pp.71-75
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• 2005

From the viewpoint of navigation safety, it would be best if it's possible to build a bridge whose main span is wide enough, however, sometimes it may not be possible due to geographical or economic reason To construct the bridge on the shipping route, consideration factors for marine traffic safety must be investigated and examined from the viewpoint of marine traffic engineering. This study aims to secure marine traffic safety and maintain smoothly traffic flow through assessment qf these factors. As the first step, examination factors such as traffic volume, ship size and bridge width were assessed quantitatively using marine traffic flow simulation technique.