• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.295-310
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• 2022

This paper proposes a modified bar simulation method for analyzing the shear lag effect of variable sectional box girder with multiple cells. This theoretical method formulates the equivalent area of stiffening bars and the allocation proportion of shear flows in webs, and re-derives the governing differential equations of bar simulation method. The feasibility of the proposed method is verified by the model test and finite element (FE) analysis of a simply supported multi-cell box girder with constant depth. Subsequently, parametric analysis is conducted to explore the mechanism of shear lag effect of varied sectional cantilever box girder with multiple cells. Results show that the shear lag behavior of variable box-section cantilever box girder is weaker than that of box girder with constant section. It is recommended to make the gradient of shear flow in the web with respect to span length vary as smoothly as possible for eliminating the shear lag effect of box girder. An effective countermeasure for diminishing shear lag effect is to increase the number of box chambers or change the variation manner of bridge depth. The shear lag effect of varied sectional cantilever box girder will get more server when the length of central flanges is shorter than 0.26 or longer than 0.36 times of total width of top flange, as well as the cantilever length exceeds 0.29 times of total length of box's flange. Therefore, the distance between central webs can adjust the shear lag effect of box girder. Especially, the width ratio of cantilever plate with respect to total length of top flange is proposed to be no more 1/3.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.649-660
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• 2005

Since the diaphragm manhole of steel box girder bridges is designed generally from experience, it has become the primary factor in the excessive cost of steel bridge construction. For the economical and efficient manufacture of diaphragm manholes, it is necessary to study the exact behavior of the diaphragm manhole in a steel box girder bridge. In this study, both an experimental test and a structural analysis are performed to verify the behavior of the diaphragm manhole in a steel box girder bridge. A detailed structural analysis was performed according to various diaphragm manhole shapes, and in conclusion, the suitable reinforcement method for the support of diaphragm manholes in steel box bridges is presented.

• Steel and Composite Structures
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• v.45 no.1
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• pp.119-131
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• 2022

Due to the complexity of the structure and the limits of classical SEA, a combined SEA approach is employed, with angle-dependent SEA in the low- and mid-frequency ranges and advanced SEA (ASEA) considering indirect coupling in the high-frequency range. As an important component of the steel box girder, the dynamic response of an L-junction periodic ribbed plate is calculated first by the combined SEA and validated by the impact hammer test and finite element method (FEM). Results show that the indirect coupling due to the periodicity of stiffened plate is significant at high frequencies and may cause the error to reach 38.4 dB. Hence, the incident bending wave angle cannot be ignored in comparison to classical SEA. The combined SEA is then extended to investigate the vibration properties of the steel box girder. The bending wave transmission study is likewise carried out to gain further physical insight into indirect coupling. By comparison with FEM and classical SEA, this approach yields good accuracy for calculating the dynamic responses of the steel box girder made of periodic ribbed plates in a wide frequency range. Furthermore, the influences of some important parameters are discussed, and suggestions for vibration and noise control are provided.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.4
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• pp.343-351
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• 2010

Bending and axial compressive stresses are distributed across the whole upper flange of a box girder bridge which has the span-to-depth ratio (B/L) of below 0.5, according to Korea Bridge Design Specifications (Minister of Land, Transport and Maritime Affairs, 2005). Shear lag phenomenon, however, can take place in the construction phase of cable-stayed bridge, in which stresses combining bending moment due to dead weight and cable vertical compression are induced. This study aims to analyze the effective width of flange over which composite stresses are given, which should be calculated during the construction phase of stiffening girder of single plane cable-stayed box girder bridge. The study results indicate that the full width of stiffening girder can be regarded as the effective flange width when the span-to-depth ratio for the deck is below 0.38. In other words, the area, where shear lag is taken into consideration, is larger than the width of box girder in single plane cable-stayed box girder bridges. Therefore, the current practice of considering the full width as the effective flange width regardless of changes of the span-to-depth ratio during the construction stage can produce an unsafe bridge. If the effective flange width is determined according to the single span structural system in the early stage of construction when the span-to depth ratio for the deck is high and composite stresses of every part expect each end of the bridge are calculated, it can result in a safe structural design. Since the span-to-depth ratio gradually decreases, however, it is appropriate to determine the effective width of flange on the basis of the full width and the cantilever structural system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.551-556
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• 2007

In this paper, the contents of numerical in the innovative tender design of the super long-span suspension bridge to be constructed between Myodo and are introduced. The total span length of the bridge, of which the main span is the third in the world so far, reaches 2,260km, and the has the floating type girder which has no vertical points at pylon. Judging from the condition of navigation, wind climate on, and construction cost, it is inevitable to make the central span 1,545m and to the technical level applied to the structural components in the existing suspension system. To realize the innovative super long-span suspension bridge, the close numerical investigations for the structural capacity, aerodynamic serviceability, and dynamic serviceability are carried out by various tools of computational mechanics.

• Structural Engineering and Mechanics
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• v.39 no.5
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• pp.643-659
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• 2011

The design of box girders requires the determinations the buckling stress of the flange and the webs. Existing design equations available in codes of practice ignore the interactions between the box girder components. The paper illustrates the influence of the geometric interaction on the buckling stress of box girders. Generalized equations are first derived in terms of the web the flange geometric properties. Industrial examples are then presented showing the variation of the flange buckling stress for various stiffening configurations. The influence of the flange/web proportions on the buckling stress of box girder components is also highlighted. It is shown that buckling strength of the flange is largely affected by the restraints imposed by the webs or attached diaphragms. Graphs are presented showing various limiting states of box girders. These graphs are useful to use in practice in order to achieve economical and efficient design of box girders and rationally predict local buckling stress.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2A
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• pp.109-118
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• 2009

A new bridge system described in this paper uses concrete-filled steel tube (CFT) girders as a replacement for conventional girders. Experimental investigations were carried out to comprehend the flexural behavior of CFT girder. Specimens were manufactured considering several parameters such as the strength of filling material, the eventual presence and number of inner shear connectors to evaluate the bending bearing capacity of CFT girder. The experimental investigation consisted of designing and constructing a test specimen and loading it to collapse in bending to check the applicability of the system. Test results showed that concrete filled steel tube girders have good ductility and maintain their strength up to the end of the loading. The stiffening effect of the ㄱ-shaped perfobond rib is determined to contribute relatively to the increase of the bending bearing capacity.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.801-811
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• 1998

In this paper, aerodynamic properties and improvements of the ${\pi}-shaped$ stiffening girder is studied by wind tunnel tests in steel composite cable stayed bridge. As an improvement device, fairing, extension, post and flap is tested. and the best improved section is selected and estimated on angles of attack, damping ratios and turbulent flows. It is shown that the selected fairing is effective to improve the aerodynamic stability. And this study can be utilized as a database of wind-resistant methodology of steel composite cable stayed bridge.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.350-355
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• 2008

This paper addresses vibration comfort evaluation on suspension bridge subjected to moving vehicles. The moving load method is commonly employed for the analysis, even though it is less accurate than the moving mass approach which considers vehicle-bridge interaction effects and roughness of the pavement. In this study, a parametric study on modeling method by means of the moving load technique, such as the number of modes included in the analysis, types of moving loads, and length of the stiffening girder, is carried out. The numerical result indicated that use of the triangular pulse load may result in significant overestimation on vibration discomfortness.

• Wind and Structures
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• v.14 no.2
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• pp.153-165
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• 2011

The alternative solution for flutter and buffeting stability of a long suspension bridge will be a passive control using flaps. This method not only enables a lightweight economic stiffening girder without an additional stiffness for aerodynamic stability but also avoid the problems from the malfunctions of control systems and energy supply system of an active control by winglets and flaps. A mechanically control using flaps for increasing flutter speed and decreasing buffeting response of a suspension bridge is experimentally studied through a two dimensional bridge deck model. The result shows that the flutter speed is increased and the buffeting response is decreased through the mechanical drive of the flaps.