• Wind and Structures
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• v.32 no.5
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• pp.509-520
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• 2021

The streamlined box is a common type of girders for long-span suspension bridges. Spanning deep canyons, long-span bridges are frequently attacked by strong winds with large angles of attack. In this situation, the flow field around the streamlined box changes significantly, leading to reduction of the flutter performance. The wind fairings have different effects on the flutter performance. Therefore, this study examines the flutter performance of box girders with different wind fairings at large angles of attack. Computational fluid dynamics (CFD) simulations were carried out to extract the flutter derivatives, and the critical flutter state of a long-span bridge was determined. Further comparisons of the wind fairings were investigated by a rapid method which is related to the input energy by the aerodynamic force. The results show that a reasonable type of wind fairings could improve the flutter performance of long-span bridges at large angles of attack. For the torsional flutter instability, the wind fairings weaken the adverse effect of the vortex attaching to the girder, and a sharper one could achieve a better result. According to the input energies on the girder with different wind fairings, the symmetrical wind fairings are more beneficial to the flutter performance

• Computers and Concrete
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• v.21 no.3
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• pp.269-278
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• 2018

In this paper, two methods M1 and M2 to determine long-term deflection through finite element analyses including the effect of creep and relaxation are proposed and demonstrated for a PSC box-girder. In both the methods, the effect of creep is accounted by different models from international standards viz., ACI-209R-92, CEB MC 90-99, B3 and GL2000. In M1, prestress losses due to creep and relaxation and age adjusted effective modulus are estimated through different models and have been used in finite element (FE) analyses for individual time steps. In M2, effects of creep and relaxation are implemented through the features of FE program and the time dependent analyses are carried out in single step. Variations in time-dependent strains, prestress losses, stresses and deflections of the PSC box-girder bridge through M1 and M2 are studied. For the PSC girder camber obtained from both M1 and M2 are lesser than simple bending theory based calculations, this shows that the camber is overestimated by simple bending theory which may lead to non-conservative design. It is also observed that stresses obtained from FEM for bottom fibre are lesser than the stresses obtained from bending theory at transfer for the PSC girder which may lead to non-conservative estimates.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.297-302
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• 2007

Although just developed in recent years, curved box girder has widely used in modern highway system due to their load resistance capacity as well as aesthetic considerations. According to recent literature reviews on curved box girder designs, distortional load was not considered as much as it deserves to be. In practice, the effect of distortional force is very small in straight bridge systems but yet unknown how it is in curved bridge systems. For the reason, this paper will show an extensive parametric study on distortional behavior. Based on Dabrowski formulas, using finite element method, various bridges were investigated. In this study, following parameters will be included: span length, curvature radius, section height, section width, and internal section angle (web slope). From the obtained results, some initial geometric parameters are proposed for curved box girder bridges.

• 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.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.05a
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• pp.227-232
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• 1998

강상형교(Steel Box Girder Bridge)는 휨강성 및 비틀림강성이 I형이나 II형 단면에 비해서 현저하게 크고 가설시의 안전성도 우수하며, 완성후의 내하력도 크다는 장점을 갖고 있어 지간이 40-80m인 교량에 적용되는 대표적인 교량형식이며, 또한 경제적, 구조적인 특성을 고려하여 대분분이 연속교 형식으로 건설되고 있다. (중략)

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.131-137
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• 1996

To perform condition monitoring of P.C. Box girder bridge under ambient traffic, dynamic characteristics were identified using the results of load test an analysis. It was found that natural frequencies obtained from the measured acceleration data for the forced vibration part and free vibration part were nearly identical. Thus it can be concluded that dynamic parameters are properly determined under ambient traffic condition. Finite element model for analysis was calibrated using measured frequencies. Change of dynamic characteristics were predicted through analysis of the established finite element model with anticipated change.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.227-234
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• 2001

The lifting and lowering supports method was recently developed in steel box girder bridge. It has many advantages by lifting and lowering of inner supports and filled concrete. This method reduces an amount of steel and height of girders. It is one of the methods used to effectively increase the use of structural material. However, if there is too much lifting of inner supports, it is possible to cause buckling of the compression flange or web panel. Therefore it needs a proper number of longitudinal and transvers stiffener.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.77-87
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• 1999

The conventional design of prestressed concrete box girder bridges has been based on the linear elastic analyses using simplified geometric models. To overcome the restriction involved in the simplifications, a macro element for the rational analysis of prestressed concrete box girder bridges with variable cross sections is incorporated in the present analysis. Through the adoption of nonlinear material models, the behaviour of prestressed box bridges up to ultimate loading stage can be examined. The time dependent material models included in the present macro element code enable to predict the long term behaviour of prestressed concrete box girder bridges. The proposed macro element code with the nonlinear material models and time dependent routines can be efficiently used for the realistic analysis of prestressed concrete box girder bridges with arbitrary shapes.

• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.449-458
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• 2016

The temperature data were measured for two years in a bridge specimen and the bridge in service nearby in order to calculate the effective temperature for thermal loads in steel box girder bridge. The maximum and minimum effective temperatures were calculated in the bridge specimen and the bridge according to air temperature in 2014, 2015 and 2years. The effective temperatures calculated in this study were compared the Euro code and the Highway Bridge Design Criteria. The coefficients of determination in the maximum effective temperature and the Euro code for 2 year were calculated from R = 0.927, R = 0.894 in a bridge specimen and the bridge respectively. Those of minimum temperature and the Euro code were analyzed from R = 0.992, R = 0.813 in two bridge respectively. Also, the results were evaluated as being very similar, or slightly increased as compared with the maximum temperature of the Korean Highway Bridge Design Code(Limit State Design).

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.564-571
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• 2005

Two-plate girder bridge and narrow steel box girder bridge are suggested for the steel wheel AGT system. For these bridge system, rail-bridge interaction analysis was carried out and dynamic behavior of these bridges was investigated. The result shows that all the estimated parameters satisfy the criteria concerned. As a result these two suggested bridge systems have enough performance to be competitive for the LRT elevated structures.