• Steel and Composite Structures
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• v.38 no.6
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• pp.657-670
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• 2021

This paper presents a designing method for enhancing fire resistance of steel box bridge girders (closed steel box bridge girder supporting a thin concrete slab) through taking into account such parameters namely; fire severity, type of longitudinal stiffeners (I, L, and T shaped), and number of longitudinal stiffeners. A validated 3-D finite element model, developed through the computer program ANSYS, is utilized to go over the fire response of a typical steel box bridge girder using the transient thermo-structural analysis method. Results from the numerical analysis show that fire severity and type of longitudinal stiffeners welded on bottom flange have significant influence on fire resistance of steel box bridge girders. T shaped longitudinal stiffeners applied on bottom flange can highly prevent collapse of steel box bridge girders towards the end of fire exposure. Increase of longitudinal stiffeners on bottom flange and web can slightly enhance fire resistance of steel box bridge girders. Rate of deflection-based criterion can be reliable to evaluate fire resistance of steel box bridge girders in most fire exposure cases. Thus, T shaped longitudinal stiffeners on bottom flange incorporated into bridge fire-resistance design can significantly enhance fire resistance of steel box bridge girders.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.262-267
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• 2008

The type used mainly in present our country in the superstructure of the railway bridge including the high speed railway is classified by the box girder and the I-type girder, greatly. The box girder is mainly used by the high speed railway bridge, and the I-type girder is used mostly by general railway bridge style. In this study, according to current railway bridge design code, we execute design by the span length of each considered bridge form. Also we analyze the suitable girder height by the span length and calculate the construction costs. The comparative analysis of the structural efficiency is produced by the span length. From this study, it is exposed that the girder height by the span length is the biggest in box girder. Also it is evaluated that the construction costs of the box girder is higher than that of the I-type girder although there is a difference between more or less according to adopted construction method.

• Wind and Structures
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• v.31 no.1
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• pp.31-41
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• 2020

A new type of bridge deck section consisting of four-box decks, two side decks for vehicular traffic lanes and two middle decks for railway traffic, has been experimentally investigated for determining its aerodynamic properties. The eight flutter derivatives were determined by the Iterative Least Squares (ILS) method for this new type of four-box deck model, with two windshields of 30 mm and 50 mm height respectively. Wind tunnel experiments were performed for angles of attack α = ±6°, ±4°, ±2° and 0° and Re numbers of 4.85×105 to 6.06×105 and it was found that the four-box deck with the 50 mm windshields had a better aerodynamic performance. Also, the results showed that the installation of the windshields reduced the values of the lift coefficient CL for the negative angles attack in the range of -6° to 0°, but the drag coefficient CD increased in the positive angle of attack range. However, galloping instability was not encountered for the tested reduced wind speeds, of up to 9.8. The aerodynamic force coefficients and the flutter derivatives for the four-box deck model were consistent with the results reported for the Messina triple-box bridge deck, but were different from those reported for the twin-box bridge decks.

• Structural Engineering and Mechanics
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• v.31 no.2
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• pp.137-152
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• 2009

Mechanic behavior of Y-shape thin-walled box girder bridge structure is complex, so one can not exactly hold the mechanical behavior of the Y-shape thin-walled box girder bridge structure through general calculation theory and analytical method. To hold the mechanical behavior better, based on elementary beam theory, by increasing the degree of freedom analytical method, taking account of restrained torsiondistortion angledistortion warp and shearing lag effect at the same time, authors obtain a thin-walled box beam analytical element of 10 degrees of freedom of every node, derive stiffness matrix of the element, and code a finite element procedure. In addition, authors combine the obtained procedure with spatial grillage analytical method, meanwhile, they build a new analytical method that is the spatial thin-walled box girder element grillage analysis method. In order to validate the precision of the obtained analysis method, authors analyze a type Y-shape thin-walled box girder bridge structure according to the elementary beam theory analytical method, the shell theory analytical method and the spatial thin-walled box girder element grillage analysis method respectively. At last, authors test a type Y-shape thin-walled box girder bridge structure. Comparisons of the results of theory analysis with the experimental text show that the spatial thin-walled box girder element grillage analysis method is simple and exact. The research results are helpful for the knowledge of the mechanics property of these Y-shape thin-walled box girder bridge structures.

• 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

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.95-102
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• 1997

Jointless bridge is a new construction method applicable to bridge of short length. In the jointless bridge expansion of superstructure due to thermal effect was absorbed in the flexible pile-type abutment in stead of expansion joint in the conventional bridges. By removing expansion joint, it retards deterioration and extends life time of bridge. In this paper, jointless bridge of steel box girder type was studied through finite element analysis. Stress variations of superstructure and pile due to thermal effect was studied for the two span continuous integral bridge of 80m length and the results of analysis was presented.

• Wind and Structures
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• v.35 no.5
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• pp.337-351
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• 2022

As central-slotted box decks usually have excellent flutter performance, studies on this type of deck mostly focus on the vortex-induced vibration (VIV) control. Yet with the increasing span lengths, cable-supported bridges may have critical wind speeds of wind-induced static instability lower than that of the flutter. This is especially likely for bridges with a central-slotted box deck. As a result, the overall aerodynamic performance of such a bridge will depend on its wind-induced static stability. Taking a 1400 m-main-span cable-stayed bridge as an example, this study investigates the influence of a series of deck shape parameters on both static and flutter instabilities. Some crucial shape parameters, like the height ratio of wind fairing and the angle of the inner-lower web, show opposite influences on the two kinds of instabilities. The aerodynamic shape optimization conducted for both static and flutter instabilities on the deck based on parameter-sensitivity studies raises the static critical wind speed by about 10%, and the overall critical wind speed by about 8%. Effective VIV countermeasures for this type of bridge deck have also been proposed.

• Steel and Composite Structures
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• v.26 no.1
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• pp.115-123
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• 2018

Steel-concrete composite structure is widely applied to bridge engineering due to their outstanding mechanical properties and economic benefit. This paper studied a new type of steel-concrete composite anchorage system for a self-anchored suspension bridge and focused on the mechanical behavior and force transferring mechanism. A model with a scale of 1/2.5 was prepared and tested in ten loading cases in the laboratory, and their detailed stress distributions were measured. Meanwhile, a three-dimensional finite element model was established to understand the stress distributions and validated against the experimental measurement data. From the results of this study, a complicated stress distribution of the steel anchorage box with low stress level was observed. In addition, no damage and cracking was observed at the concrete surrounding this steel box. It can be concluded that the composite effect between the concrete surrounding the steel anchorage box and this steel box can be successfully developed. Consequently, the steel-concrete composite anchorage system illustrated an excellent mechanical response and high reliability.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.165-166
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• 2009

This paper is to research for construction of the longest open toped steel box girder composite bridge using precast concrete deck in the country. This type bridge can bring down the construction costs by reducing the steel's weight used it's girders. And, it also can reduce working hours for construction over 6months by applying the precast deck system. I will introduce the process of construction the longest this type bridge within the country named Seochon Bridge

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.154-161
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• 2012

The damping ratio of railway bridge has become one of the most important issues in dynamic design and dynamic stability of railway bridge. In the present study, laboratory and field test were performed for railway bridges such as a twin I-shaped steel composite girder, PSC box, steel box, PSC, IPC, PRECOM, preflex. The damping ratio of railway bridge according to structure types was estimated by logarithmic decrement method. Therefore, magnitude, frequency and amplitude of load did not affect damping ratio of railway bridge. Also, damping ratio limit of steel composite and PSC bridges was evaluated in 1.0%.