• Wind and Structures
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• v.23 no.3
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• pp.191-209
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• 2016

Wind tunnel tests of a 1/2200-scale mountainous terrain model have been carried out to investigate local wind characteristics at a bridge location in southeast Tibet, China. Flows at five key locations on the bridge at deck level were measured for 26 directions. It was observed that wind characteristics (including mean wind velocity and overall turbulence intensity) vary significantly depending on the approaching wind direction and measurement position. The wind inclination angle measured in the study fluctuated between $-18^{\circ}$ and $+16^{\circ}$ and the ratio of mean wind velocity to reference wind velocity was small when the wind inclination angles were large, especially for positive wind inclination angles. The design standard wind speed and the minimum critical wind speed for flutter rely on the wind inclination angle and should be determined from the results of such tests. The variation of wind speed with wind inclination angles should be of the asymmetry step type. The turbulence characteristics of the wind were found to be similar to real atmospheric flows.

• Smart Structures and Systems
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• v.31 no.2
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• pp.155-169
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• 2023

The quasi-static component of the moving vehicle-induced dynamic response is promising in damage detection as it is sensitive to bridge damage but insensitive to environmental changes. However, accurate extraction of quasi-static component from the dynamic response is challenging especially when the vehicle velocity is high. This paper proposes an adaptive quasi-static component extraction method based on the modified variational mode decomposition (VMD) algorithm. Firstly the analytical solutions of the frequency components caused by road surface roughness, high-frequency dynamic components controlled by bridge natural frequency and quasi-static components in the vehicle-induced bridge response are derived. Then a modified VMD algorithm based on particle swarm algorithm (PSO) and mutual information entropy (MIE) criterion is proposed to adaptively extract the quasi-static components from the vehicle-induced bridge dynamic response. Numerical simulations and real bridge tests are conducted to demonstrate the feasibility of the proposed extraction method. The results indicate that the improved VMD algorithm could extract the quasi-static component of the vehicle-induced bridge dynamic response with high accuracy in the presence of the road surface roughness and measurement noise.

• Smart Structures and Systems
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• v.31 no.1
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• pp.29-43
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• 2023

This study investigates the possibility of damage detection of a real bridge by means of a modal parameter-based finite element (FE) model update. Field moving vehicle experiments were conducted on an actual steel plate girder bridge. In the damage experiment, cracks were applied to the bridge to simulate damage states. A fast Bayesian FFT method was employed to identify and quantify uncertainties of the modal parameters then these modal parameters were used in the Bayesian model update. Material properties and boundary conditions are taken as uncertainties and updated in the model update process. Observations showed that although some differences existed in the results obtained from different model classes, the discrepancy between modal parameters of the FE model and those experimentally obtained was reduced after the model update process, and the updated parameters in the numerical model were indeed affected by the damage. The importance of boundary conditions in the model updating process is also observed. The capability of the MCMC model update method for application to the actual bridge structure is assessed, and the limitation of FE model update in damage detection of bridges using only modal parameters is observed.

• Structural Engineering and Mechanics
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• v.90 no.4
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• pp.417-428
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• 2024

Nanocomposite-reinforced concrete systems have gained increasing attention in bridge construction due to their enhanced mechanical properties and durability. Understanding the transient dynamics of these advanced materials is crucial for ensuring the structural integrity and performance of bridge infrastructure under dynamic loading conditions. This paper presents a comprehensive study of the measurement techniques employed for assessing the transient dynamics of nanocompositereinforced concrete systems in bridge construction applications. A numerical method, including modal analysis are discussed in detail, highlighting their advantages, limitations, and applications. Additionally, recent advancements in sensor technologies, data acquisition systems, and signal processing techniques for capturing and analyzing transient responses are explored. The paper also addresses challenges and opportunities in the measurement of transient dynamics, such as the characterization of nanocomposite-reinforced concrete materials, the development of accurate numerical models, and the integration of advanced sensing technologies into bridge monitoring systems. Through a critical review of existing literature and case studies, this paper aims to provide insights into best practices and future directions for the measurement of transient dynamics in nanocompositereinforced concrete systems, ultimately contributing to the design, construction, and maintenance of resilient and sustainable bridge infrastructure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.255-266
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• 2012

Main cable of a suspension bridge is the important member which shows the overall structure integrity at bridge completion. Configuration of main cable is a free hanging state at cable erection completion and is different from that at bridge completion supporting the dead loads such as hanger, girder, and so on. Accordingly, the configuration control under cable erection is considerably significant because the configuration at cable erection completion has direct influence on that at bridge completion. That is performed by sag adjustments at center, side span and tension adjustments at anchor span. The former needs the sag sensitivity which represents the control quantity of strand length corresponding to that of sag. The latter requires the tension sensitivity which shows the change of strand tension according to that of strand temperature. In this study, the fundamental equations of cable were derived with the assumption of either catenary or parabola shape, the differential-related equations using chain rule on horizontal tension were drawn from those and finally the estimation methods of the sag / tension sensitivity were proposed from both those. The nonlinear numerical analysis flow charts of sag sensitivity based on the catenary equations were proposed and the sag sensitivities grounded on the differential-related equations were compared with the results using them for various parameters of sag change. Also, considering the combinations of sag change parameters, the calculation method of the final variation for the cable sag was suggested. For the real suspension bridge under construction with PPWS method, the sag/tension sensitivity were estimated considering the construction conditions like the change of PPWS length, PPWS temperature, bridge span, etc.. We hope that this study will be a systematic guideline for the configuration control under main cable erection and improved highly by field verification in the real bridge site.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.557-564
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• 2014

In this study, we present an algorithm that conducts an unique naming process for the bridge object through the solid object identification focused on 3D straight bridge model. For the recognition of 3D objects, the numerical algorithm utilizes centroid point, and solid object on the local coordination system. It classifies the object feature set by classifying the objects and members based on the bridge direction. By doing so, unique names, which contain the information about span, members and order of the object, were determined and the suitability of this naming algorithm was examined through a truss bridge model and a bridge model with different coordinate systems. Also, the naming process based on the object feature set was carried out for the real 3D bridge model and then was applied to the module on local server and mobile device for real bridge inspection work. From the comparison of the developed naming algorithm based on object identification and the conventional one based on field inspection, it was shown that the conventional field inspection work can be effectively improved.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.7-21
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• 2008

Foundation failure due to bridge scour during floods is the leading cause of bridge failure. Performed were the evaluation of bridge scour vulnerability and prioritization on real bridges registered in the National Highway Bridge Inventory of the capital region. The case studies for 30 national highway bridges consist of site investigation including boring test, bridge scour analysis fur the design flood, bearing capacity evaluation of the bridge foundation before and after scour, comprehensive evaluation of bridge scour vulnerability, and prioritization. Nine of 26 spread (feting bridges showed the potential future vulnerability to scour with significant decrease in the bearing capacity of foundations due to scour and the remaining 17 spread footing bridges were expected to maintain their stability to resist the effects of scour. Three of 4 pile foundation bridges exhibited considerable decrease in the bearing capacity of foundation after scour.

• Wind and Structures
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• v.10 no.1
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• pp.61-82
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• 2007

This paper presents a novel finite element (FE) model for analyzing coupled flutter of long-span bridges using the commercial FE package ANSYS. This model utilizes a specific user-defined element Matrix27 in ANSYS to model the aeroelastic forces acting on the bridge, wherein the stiffness and damping matrices are expressed in terms of the reduced wind velocity and flutter derivatives. Making use of this FE model, damped complex eigenvalue analysis is carried out to determine the complex eigenvalues, of which the real part is the logarithm decay rate and the imaginary part is the damped vibration frequency. The condition for onset of flutter instability becomes that, at a certain wind velocity, the structural system incorporating fictitious Matrix27 elements has a complex eigenvalue with zero or near-zero real part, with the imaginary part of this eigenvalue being the flutter frequency. Case studies are provided to validate the developed procedure as well as to demonstrate the flutter analysis of cable-supported bridges using ANSYS. The proposed method enables the bridge designers and engineering practitioners to analyze flutter instability by using the commercial FE package ANSYS.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.183-186
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• 2010

This paper presents a stable real-time based FlexRay technology which is employed with a standard protocol of the marine electronic equipments and the bridge navigational watch alarm system (BNWAS). The traditional marine communications use NMEA communication protocols, and RS-232 and RS-422 techniques in the BNWAS, thus there are difficulty in seeking stability and reliability. To overcome such problems we utilize the FlexRay protocol technique to prevent data loss or error.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.98-106
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• 2011

The deck of steel box girder bridges is composed of deck plate, longitudinal rib, and transverse ribs. The orthotropic steel decks have high possibility to fatigue damage due to numbers of welded connection part, the heavy contact loadings, and the increase of repeated loadings. Generally, the local stress by the repeated loadings of heavy vehicles causes the orthotropic steel deck bridge to fatigue cracks. The increase of traffic volume and heavy vehicle loadings are promoted the possibility of fatigue cracks. Thus, it is important to exactly evaluate the structural behavior of bridge considering the contact loading area of heavy vehicles and real load patterns of heavy trucks which have effects on the bridge. This study estimated the effect of contact area of design loads and real traffic vehicles through the finite element analysis considering the real loading conditions. The finite element analysis carried out 4 cases of loading patterns in the orthotropic steel deck bridge. Also, analysis estimated the influence of contact area of real truck loadings by the existence of diaphragm plate. The result of finite element analysis indicated that single tire loadings of real trucks occurred higher local stress than one of design loadings, and especially the deck plate got the most influence by the single tire loading. It was found that the diaphragm attachment at joint part of longitudinal ribs and transverse ribs had no effects on the improvement of structural performance against fatigue resistance in elastic analysis.