• Wind and Structures
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• v.30 no.2
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• pp.119-131
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• 2020

A butterfly web girder is a box-shaped girder with discretely distributed side openings along the spanwise direction. Until now, there have been few studies related to the aerodynamic performance of the butterfly web bridge. The objective of the current study was to clarify the effects of the side openings on the aerodynamic performance of the girder. Two butterfly web girders with side ratios B/D = 3.24 and 5, where B is the girder width and D is the depth, were examined through a series of wind tunnel tests. A comparison of the results for butterfly web girders and conventional box girders of the same shape confirmed that the side openings stabilized the vortex-induced vibration and galloping when B/D = 3.24, whereas the vortex-induced vibration and torsional flutter were stabilized when B/D = 5. The change in the flow field due to the side openings contributed to the stabilization against the vibration. These findings not only confirmed the good aerodynamic performance of the butterfly web bridge but also provided a new method to stabilize the box girder against aerodynamic instabilities via discretely distributed side openings.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.405-408
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• 2008

The most effective factors that improve sections and elongate spans of the prestressed concrete girders are shapes of sections and strengths of concretes, and the concrete strength is more influenced to enhance the allowable tensile strength on top and bottom fibers than increasing of flexural strength of girders. In this study, 60 MPa high-strength prestressed concretes were constructed at the Wonsoo Bridge where in the 1st section of expanding constructions of the Nonsan to Junjoo Expressway, the high-strength concrete was placed on the eight- 35 meters simple span IPC girders of four lanes of Nonsan direction. During casting of girder concretes, quality controls were carried out with continuing controls of surface moistures and corrections of the unit water using the air-meter methods right after batching. It was confirmed that compressive strengths of girder concretes ensure the target strength and the heat of hydrations of girder concrete were measured. Though using same materials and constructing methods, there're a wide range of strengths of each girder, so, when high-strength concretes cast in the place hereafter, a countermove should be prepared.

• Structural Engineering and Mechanics
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• v.54 no.6
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• pp.1135-1152
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• 2015

Most of current bridge decks are made of reinforced concrete and often deteriorate at a relatively rapid rate in operational environments. The quick deterioration of the deck often impacts other critical components of the bridge. Another disadvantage of the concrete deck is its high weight in long-span bridges. Therefore, it is essential to examine new materials and innovative designs using hybrid system consisting conventional materials such as concrete and steel with FRP plates which is also known as composite deck. Since these decks are relatively new, so it would be useful to evaluate their performances in more details. The present study is dedicated to Hat-Shape composite girder with concrete slab. The structural performance of girder was evaluated with nonlinear finite element method by using ABAQUS and numerical results have been compared with experimental results of other researches. After ensuring the validity of numerical modeling of composite deck, parametric studies have been conducted; such as investigating the effects of constituent properties by changing the compressive strength of concrete slab and Elasticity modulus of GFRP materials. The efficacy of the GFRP box girders has been studied by changing GFRP material to steel and aluminum. In addition, the effect of Cross-Sectional Configuration has been evaluated. It was found that the behavior of this type of composite girders can be studied with numerical methods without carrying out costly experiments. The material properties can be modified to improve ultimate load capacity of the composite girder. strength-to-weight ratio of the girder increased by changing the GFRP material to aluminum and ultimate load capacity enhanced by deformation of composite girder cross-section.

• Steel and Composite Structures
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• v.45 no.2
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• pp.159-173
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• 2022

This paper proposes a hybrid machine-learning model, which is called DANN-IP, that combines a deep artificial neural network (DANN) and an interior-point (IP) algorithm in order to improve the prediction capacity on the patch loading resistance of steel plate girders. For this purpose, 394 steel plate girders that were subjected to patch loading were tested in order to construct the DANN-IP model. Firstly, several DANN models were developed in order to establish the relationship between the patch loading resistance and the web panel length, the web height, the web thickness, the flange width, the flange thickness, the applied load length, the web yield strength, and the flange yield strength of steel plate girders. Accordingly, the best DANN model was chosen based on three performance indices, which included the R^2, RMSE, and a20-index. The IP algorithm was then adopted to optimize the weights and biases of the DANN model in order to establish the hybrid DANN-IP model. The results obtained from the proposed DANN-IP model were compared with of the results from the DANN model and the existing empirical formulas. The comparison showed that the proposed DANN-IP model achieved the best accuracy with an R^2 of 0.996, an RMSE of 23.260 kN, and an a20-index of 0.891. Finally, a Graphical User Interface (GUI) tool was developed in order to effectively use the proposed DANN-IP model for practical applications.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.163-176
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• 2006

The paper proposes rating equations for main components such as girders, towers and cables in cable-stayed bridges. Load rating equations for girders and towers are proposed using stress and stability equations and load rating equation for cables is presented. A moving load analysis is performed and distribution types of live loads are determined for the cases of a maximum axial tensile force, a maximum axial compressive force, a maximum positive and a negative moment for each component. The Dolsan Grand bridge is used to verify a validity of proposed equations, The conventional rating equation overestimates rating factors of girders and towers in the Dolsan Grand bridge, whereas proposed rating equations properly reflect the axial-flexural interaction behavior of girders and towers in cable-stayed bridges.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.571-582
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• 2012

Prestressed composite girders provide efficient composite action by applying prestress to the sub-encasing concrete. In this study, an enhanced prestressed composite girder with forms suspended from the steel girder is utilized. Long-term behavior of the prestressed composite girder is estimated using age-adjusted effective modulus method, which is verified experimentally using measurements obtained from an in-service bridge. Then, parametric study is carried out to investigate the influences caused by ambient temperature, humidity, prestressing and concrete casting date.

• Steel and Composite Structures
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• v.34 no.3
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• pp.321-332
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• 2020

The loss of composite action at the hogging moment zone for a continuous composite girder reduces the girder stiffness and strength. This paper presents an experimental investigation of the use of an ultra-high performance concrete (UHPC) slab at the hogging moment zone and a normal concrete (NC) slab at the sagging moment zone. The testing was conducted to verify the level of loading at which composite action is maintained at the hogging moment zone. Four two-span continuous composite girders were tested. The thickness of the UHPC varied between a half and a full depth of slab. The degree of shear connection at the hogging moment zone varied between full and partial. The experimental results confirmed the effectiveness of the UHPC slab to enhance the girder stiffness and maintain the composite action at the hogging moment zone at a load level much higher than the upper service load limit. To a lesser degree enhanced performance was also noted for the smaller thickness of the UHPC slab and partial shear connection at the hogging moment zone. Plastic analysis was conducted to evaluate the ultimate capacity of the girder which yielded a conservative estimation. Finite element (FE) modeling evaluated the girder performance numerically and yielded satisfactory results. The results indicated that composite action at the hogging moment zone is maintained for the degree of shear connection taken as 50% of the full composite action and use of UHPC as half depth of slab thickness.

• Advances in Computational Design
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• v.2 no.2
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• pp.147-168
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• 2017

Over the past couple decades, externally bonded fiber reinforced polymer (FRP) composites have emerged as a repair and strengthening material for many concrete infrastructure applications. This paper presents an analytical investigation of the use of carbon FRP (CFRP) for a specific problem that occurs in concrete bridge girders wherein the girder ends are damaged by excessive exposure to deicing salts and numerous freezing/thawing cycles. A 3D finite element (FE) model of a full scale prestressed concrete (PC) I-girder is used to investigate the effect of damage to the cover concrete and stirrups in the end region of the girder. Parametric studies are performed using externally bonded CFRP shear laminates to determine the most effective repair schemes for the damaged end region under a short shear span-to-depth ratio. Experimental results on shear pull off tests of CFRP laminates that have undergone accelerated aging are used to calibrate a bond stress-slip model for the interface between the FRP and concrete substrate and approximate the reduced bond stress-slip properties associated with exposure to the environment that causes this type of end region damage. The results of these analyses indicate that this particular application of this material can be effective in recovering the original strength of PC bridge girders with damaged end regions, even after environmental aging.

• International Journal of Concrete Structures and Materials
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• v.7 no.1
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• pp.71-78
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• 2013

Prestressed concrete (PC) is the predominant material in highway bridge construction. The use of high-strength concrete has gained wide acceptance in the PC industry. The main target in the highway industry is to increase the durability and the life-span of bridges. Cracking of elements is one aspect which affects durability. Recently, nine 7.62 meter long PC I-beams made with different concrete strength were designed according to a simple, semi-empirical equation developed at the University of Houston (UH) (Laskar et al., ACI Journal 107(3): 330-339, 2010). The UH Method is a function of shear span-to-depth ratio (a/d), concrete strength $\sqrt{f^{\prime}_c}$, web area $b_wd$, and amount of transverse steel. Based on testing these girders, the shear cracking strength of girders with different concrete strength and different shear span-to-depth ratio was investigated and compared to the available approaches in current codes such as ACI 318-11 (2011) and AASHTO LRFD Specifications (2010).

• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.369-377
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• 2013

The age-adjusted effective modulus method has been known to provide more precise assessment than the traditional Yassumi method for long-term behavior estimation of prestressed composite girders. The age-adjusted effective modulus method, however, involves complicated calculation, thereby making the Yassumi method more prevalent in actual design. This study presents rational approaches to revise creep coefficients for the Yassumi method by using parametric study results obtained from the age-adjusted effective modulus method.