• Structural Engineering and Mechanics
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• v.54 no.2
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• pp.257-289
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• 2015

Shear connectors are generally used to link the slab and girders together in slab-on-girder bridge structures. Damage of shear connectors in such structures will result in shear slippage between the slab and girders, which significantly reduces the load-carrying capacity of the bridge. Because shear connectors are buried inside the structure, routine visual inspection is not able to detect conditions of shear connectors. A few methods have been proposed in the literature to detect the condition of shear connectors based on vibration measurements. This paper proposes a different dynamic condition assessment approach to identify the damage of shear connectors in slab-on-girder bridge structures based on power spectral density transmissibility (PSDT). PSDT formulates the relationship between the auto-spectral densities of two responses in the frequency domain. It can be used to identify shear connector conditions with or without reference data of the undamaged structure (or the baseline). Measured impact force and acceleration responses from hammer tests are analyzed to obtain the frequency response functions at sensor locations by experimental modal analysis. PSDT from the slab response to the girder response is derived with the obtained frequency response functions. PSDT vectors in the undamaged and damaged states can be compared to identify the damage of shear connectors. When the baseline is not available, as in most practical cases, PSDT vectors from the measured response at a reference sensor to those of the slab and girder in the damaged state can be used to detect the damage of shear connectors. Numerical and experimental studies on a concrete slab supported by two steel girders are conducted to investigate the accuracy and efficiency of the proposed approach. Identification results demonstrate that damages of shear connectors are identified accurately and efficiently with and without the baseline. The proposed method is also used to evaluate the conditions of shear connectors in a real composite bridge with in-field testing data.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.823-832
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• 2006

To ensure the serviceability requirements of PSC composite girder bridges, it is essential to predict the stresses and deformations of the structure under service load conditions. Stresses and deformations vary continuously with time due to the effects of creep and shrinkage of concrete and relaxation of prestressing steel. The importance of these time-dependent effects is much more pronounced in precast prestressed concrete structures built in stages than in those constructed in one operation. In this paper, time-dependent analyses for PSC composite bridges using 30m standard girders have been conducted considering with the variation of the times of introducing initial prestressing forces and casting concrete. A computer program has been developed for the time-dependent analysis of simple or continuous PSC composite girders and parametric studies are conducted. Based on the numerical results, it is investigated the long-term behaviors of PSC composite girder bridges and discussed the limitations of the current codes for the prestress loss.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.527-536
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• 2005

A method of reinforcement using external tendons has been found to be one of the effective techniques of reinforcement and its application is increasing. In this paper, the method to calculate the initial tendon force is proposed for the improvement of load-carrying capacity in existing steel-concrete composite bridges. An equation for the increment of tendon force was derived for tendon configurations and live load types, and the effect of reinforcement in a composite beam was numerically studied. The method to calculate the number of tendon and initial tendon force was presented by proposing the new method to calculate the rating factor, which considers the increment of tendon force. The method was shown to be effective for an existing steel-concrete bridge.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.439-448
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• 2000

A multi-level design synthesis (MLDA) algorithm for efficiently optimizing orthotropic steel deck bridges is proposed in the paper, because it is usually very difficult to optimize orthotropic steel deck bridges using a conventional single-level (CSL) algorithn since the bridges have a large number of members and show complex structural behaviors. In the proposed MLDS algorithms a coordination method is introduced to divide the bridges into main girders and orthotropic steel decks and decomposition method is also used to reduce the number of design variables of the decks for system level optimization. For efficient optimization of the bridges the MLDS algorithm incorporates the crucial approximation techliques such as constraints deletion and stress reanalysis. The constraint deletion technique for deflection is found to be very useful for the optimization problem of the bridges, since a deflection constraint is usually inactive in the design. Considering the complex system of the bridges, the proposed the efficient stress reanalysis technique may prove to be a very effective method, since it does not require expensive design sensitivity analyses. The applicability and robustness of the MLDS algorithm is demonstrated using various numerical examples and compared with other algorithm presently available so far.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.2
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• pp.111-122
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• 1994

In this study, an algorithm which can be applied to the optimum design of simple steel plate girders was developed, and efficient optimization strategies for the solution of algorithm were found out. The optimum design algorithm consists of 3-levels of optimization. In the first and second levels of optimization, the absolute maximum bending moment and shearing force are extracted and in the third level of optimization, the optimum cross section of steel plate girder is determined. For the optimum design of cross section, the objective function is formulated as the total area of cross section and constraints are derived in consideration of the various stresses and the minimum dimension of flange and web based on the part of steel bridge in the Korea standard code of road bridge. Sequential unconstrained minimization technique using the exterior penalty function method(SUMT-EP), sequential linear programming(SLP) and sequential quadratic programming (SQP) are proved to be efficient and robust strategies for the optimum design of simple plate girder cross section. From the reliable point of view, SLP is the most efficient and robust strategy and SQP is the most efficient one from the viewpoint of converguency and computing time.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.217-220
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• 2008

Recently, many studies about a high-strength concrete and composite structures are being progressed to get the more economic and stable result in the construction of structure all over the world. One of those studies is about CFTA(Concrete Filled and Tied Steel Tubular Arch) girder that applies an arch structure and a pre-stressed structure to CFT(Concrete Filled Steel Tubular) Structure which is filled with a concrete and improve the stiffness and strength of the structure by the confinement effect of fillers to maximize the efficiency of structure and economic. In this study, non-linear behavior of CFTA girders filled with a general concrete and the high-strength concrete respectively were analyzed by using ABAQUS 6.5-1 and results were compared.

• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.231-239
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• 2003

Many box girder bridges have been constructed during the past several decades due to their large bending and torsional rigidities as well as aesthetic considerations. However, box girders have shortcoming in that the cross section distorts under an eccentric loading and warps out of the section plane. Therefore, in order to reduce distortional stresses such as distortional warping and transverse bending normal stresses, diaphragms were generally installed in the box girders. Shapes of the diaphragms in steel-box-girder bridges constructed up to date were solid-plate, frame, and truss types. The objectives of this study using parametric study were to evaluate the appropriate stiffness ratio of intermediate diaphragms and then to propose the effective spacing and numbers of intermediate diaphragms based on the evaluated stiffness ratio. Target bridges for this study were straight continuous span bridges with a single-cell steel box section. The parameters for the parametric study were the shape of box section, the span numbers, the equivalent span length, the stiffness of intermediate diaphragms, and the spacing of intermediate diaphragms. From the results of the parametric study, the effective spacing and numbers as well as the stiffness ratio of the intermediate diaphragms will be presented.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.537-547
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• 2005

MABB(Editor's note: Please spell out "MABB" upon first mention)is a new structural type of arch that connects arch ribs and stiffened girders with two internal arches. In this study, the static and dynamic behavior of MABB were analyzed in comparison with those of conventional arches for the investigation of the structural effect of MABB on moving loads. For the purpose of surveying the effect of internal arches on the dynamic behavior of structure, natural frequency and natural vibration mode were investigated and the static and dynamic behavior were analyzed by the method of idealizing train loads as traveling loads consisting of a group of concentrated loads. From the results, the following conclusions were known. First, it is concluded that with MABB, decreasing the section of stiffened girders is possible as compared with conventional arches because the increase of stiffness by internal arches is larger than that of the mass of internal arches. Second, MABB has the advantage of assurance of stability of dynamic behavior because the dynamic behavior of MABB on moving loads is usually investigated in a more stable way than that of conventional arches.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.559-569
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• 2012

Cross-beam in the existing temporary bridge system is usually installed to prevent the lateral-torsional buckling of girders and to promote the construction efficiency. However, most of this cross-beams are connected to the girder web by bolts, and therefore, gravitational load resisting capacity of the cross-beams are negligibly small. In recent years, new temporary bridge system, in which the cross-beams and girders are connected to resist the external loads as a unit, was developed. In this paper, we present the experimental and analytical study results pertaining to the structural behavior and load carrying capacity of new temporary bridge system. From the results of study, it was found that the continuous cross-beam increased the flexural rigidity and reduced the maximum flexural stress in the girder. In addition, it was also found that the new temporary bridge system developed is more appropriate for the application in the long-span temporary bridge.

• Journal of Korean Society of Steel Construction
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• v.30 no.1
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• pp.49-58
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• 2018

This study conducted nonlinear finite element analysis to figure out the influence of shear performance on the ${\beta}$ of girders with trapezoidal corrugated web. Through the experiment specimen, analysis model which is highly accurate was verified. Based on this, a parameter analysis was conducted on key variables affecting ${\beta}$. Proposed formulas of previous studies were analyzed using parameter analysis result. Eurocode was designed to be safer than other proposals. Only models that are included in the inelastic area, depending on the Moon's proposal, were satisfied the proposed formulas by Kim to enhance economic design.