• Journal of Korean Society of Steel Construction
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• v.26 no.2
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• pp.91-103
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• 2014

High performance steel for bridges(HSB 800) with a minimum tensile stress of 800MPa was recently developed. However, the study for local buckling behavior of plate girders considering interactive effects of flanges and webs is still insufficient. In this study, the flange local buckling(FLB) strength of plate girders with HSB 800 was evaluated by nonlinear finite element analysis. The flanges and webs of plate girders having I-section were modeled as 3D shell elements in the nonlinear analysis. Initial imperfection and residual stress were imposed on the plate girder. The high performance steel was modeled as a multi-linear material. Thus, parametric study of compression flanges with a compact, noncompact and slender web was performed. The flange local buckling behavior of plate girders was analyzed, and the nonlinear analysis results were compared with the nominal flexural strength of both AASHTO LRFD(2012) and KHBDC LSD(2012) codes.

• Wind and Structures
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• v.25 no.3
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• pp.283-299
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• 2017

Two types of aerodynamic admittance function (AAF) that have been adopted in bridge aerodynamics are addressed. The first type is based on a group of supposed relations between flutter derivatives and AAFs. In so doing, the aero-elastic properties of a section could be used to determine AAFs. It is found that the supposed relations hold only for cases when the gust frequencies are within a very low range. Predominant frequencies of long-span bridges are, however, far away from this range. In this sense, the AAFs determined this way are of little practical significance. Another type of AAFs is based on the relation between the Theodorsen circulation function and the Sears function, which holds for thin airfoil theories. It is found, however, that an obvious illogicality exists in this methodology either. In this article, a viewpoint is put forward that AAFs of bluff bridge deck sections are inherently dependent on oncoming turbulent properties. This kind of dependence is investigated with a thin plate and a double-girder bluff section via computational fluid dynamics method. Two types of wind fluctuations are used for identification of AAFs. One is turbulent wind flow while the other is harmonic. The numerical results indicate that AAFs of the thin plate agree well with the Sears AAF, and show no obvious dependence on the oncoming wind fields. In contrast, for the case of bluff double-girder section, AAFs identified from the turbulent and harmonic flows of different amplitudes differ among each other, exhibiting obvious dependence on the oncoming wind field properties.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.110-113
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• 2009

본 연구에서는 무선센서노드을 이용하여 강판형 철도교량의 전형적인 손상유형인 거더부의 휨강성 저하와 지점부의 볼트풀림을 효과적으로 모니터링할 수 있는 하이브리드 모니터링 기법을 제안하였다. 이를 위해 다음과 같은 연구가 수행되었다. 첫째, 본 연구진에 의해 개발된 가속도 및 임피던스기반 무선센서노드를 간략하게 소개하였다. 둘째, 가속도 및 임피던스 신호를 이용하여 효과적인 손상모니터링이 가능한 기법들을 선정하였다. 마지막으로, 개발된 가속도 및 임피던스기반 무선센서노드를 모형 강판형 철도교에 설치하고, 일련의 손상 시나리오에 따른 하이브리드 모니터링을 수행하여 무선센서노드 및 모니터링 기법의 성능을 평가하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.326-331
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• 2009

An algorithm is proposed for computing dynamic displacements of a bridge using FBG sensors. An existing algorithm for estimating dynamic displacements of a simply supported beam through mode superposition is extended and applied to various types of bridges with bending and torsional modes. The proposed algorithm is examined through field tests on a suspension span steel deck plate box girder bridge. Guidelines are provided for determining the number of modes and the number of strain gages to be used.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.45-51
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• 2002

An acoustic finite element model of a bridge is developed to evaluate the noise generated by the traffic-induced vibration of the bridge. The dynamic response of a multi-girder bridge, modeled by a 3-dimensional frame element model, is analyzed with a 3-axle 8 DOFs truck model and a 5-axle 13 DOFs semi-trailer. The flat plate element is used to analyze the acoustic pressure due to the fluid-structure interactions between the vibrating surface and contiguous acoustic fluid medium. The radiation fields of noise with a specified distribution of vibrating velocity and pressure on the structural surface are also computed using the Kirchhoff-Helmholtz integral. Although the noise produced by the bridge vibration is not serious in itself, which is below the audible frequency range, it should be considered as an interaction problem between vehicle noise and bridge vibration noise in order to evaluate the traffic noise around the bridge.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.223-232
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• 2001

This paper describes Genetic Algorithm-Based Relay Search Method, RS-GA, which is developed in this study to search the multiple design variables in the design space. The RS-GA based on Simple-GA consists of some functions to search many variables from some wide variable space. It repeats a Simple-GA, that is the convergence process of the Simple-GA, which makes many time reiteration itself. From the results of the numerical studies, it was actually found that RS-GA can search all peak-variable from the 2D functions including 5 peaks. Finally, RS-GA applied for design-strengthening problems in composite plate girder bridges using the external prestressing technique is also verified.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.83.1-83.1
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• 2010

본 연구는 고강도 강재를 적용한 연속교 형식의 강교량에 대하여 연구를 수행하였다. 교량에 사용되는 주구조의 고강도화에 따로 연속교의 교각 부근 부모멘트부에는 정모멘트부에 비하여 큰 모멘트가 작용하게 된다. 또한 정모멘트 구간과 달리 상부플랜지에 인장력이 작용하게 되어 완공 후에도 극한 하중 상태에서 콘크리트 데크가 응력을 부담할 수 없게 된다. 이에 따라 하부 플랜지에 불안정 파괴가 발생할 가능성이 있으며 비합성 단면과 같은 방법으로 설계하게 된다. 또한 모멘트 재분배를 고려한 설계를 하기 위해서는 부모멘트부에 충분한 휨 연성이 필요하다. 고강도 강재를 적용한 교량은 일반강재를 적용한 교량에 비하여 휨연성이 감소하게 되므로 휨연성 확보를 위한 보강방안이 필요하다. 본 연구는 부모멘트부의 휨연성 향상을 휘하여 가로보의 부등 배치를 제안하였으며, 유한요소해석 결과 휨연성이 향상되었다.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.707-715
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• 2005

Corrugated webs have been used for composite prestressed concrete box girder bridges. Innovative steel plate girders using corrugated webs have been proposed. It has been found that analytical and experimental researches conducted to determine the strength of trapezoidally corrugated webs can fail with respect to three different buckling modes: local, global, and interactive shear buckling. Shear buckling capacity equations based on classical and orthotropic plate buckling theories have been proposed,but these equations show some differences. In this paper, geometric parameters that influence interactive shear buckling behavior with interaction effects are identified via extensive bifurcation buckling analysis using the finite element meth.

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.84-92
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• 2012

Anchorage zone in prestressed concrete cable stayed bridges is very important area due to the more accurate analysis is needed to estimate the behavior. In the study, since the cable anchorage zone in the prestressed concrete cable-stayed bridge is subject to a large amount of concentrated tendon forces, it shows very complicated stress distributions and causes a serious local cracks. Accordingly, It is necessary to investigate the parameters of affecting the stress properties, such as the cable inclination, the position of anchor plate, the modeling method and the three dimensional effect. The tensile stress distribution of anchorage zone is compared to the actual design condition by varing the stiffness of spring element in the local modeling and an appropriate position of anchor plate is determined. These results would be elementary data to the stress state of anchorage zone and more efficient design.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.483-490
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• 2007

Traditional external post-tensioning method using either steel bars or tendons is commonly used as a retrofitting method for concrete bridges. However, the external post-tensioning method has some disadvantages such as stress concentration at anchorages and inefficient load carrying capability regarding live loads. Thermal prestressing method is a newly proposed method for strengthening and rehabilitation of concrete girder bridges. Founded on a simple concept of thermal expansion and contraction of steel, the method is a hybrid method of external post-tensioning and steel plate bonding, combining the merits of two methods. In this paper, basic concepts of the method are presented and an illustrative experiment is introduced. From actual experimental data, the thermal prestressing effect is substantiated and the FEM approach for its analysis is verified.