• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.456-464
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• 2016

Increasing the strength of structural materials allows their self-weight to be reduced and this, in turn, enables the structures to satisfy esthetic requirements. The yield strength of high-performance steel is almost 480 MPa, which is approximately 50% higher than that of general structural steel. The use of high strength materials, however, makes the sections more slender, which can potentially result in significant local stability problems. The strength of slender element sections might be governed by their elastic buckling behavior, and the elastic buckling strength is very sensitive to the boundary conditions. Because the web provides the boundary conditions of the compressive thin-flange, the stiffness of the web can affect the elastic buckling strength of the flange. In this study, therefore, the effects of the flange and web slenderness ratios on the elastic flange local buckling of I-girders subjected to a pure bending moment were evaluated by finite element analysis (FEA). The analysis results show that the elastic local buckling strength and buckling modes were affected not only by the web support conditions, but also by the flange and web slenderness ratios.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.13-22
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• 2000

In order to resolve the problem of increasing traffic entailed by the economic development, road system is reorganization and new highways are built, and long span bridges over 40m are being constructed in environmental and aesthetic considerations. Most long span bridges that are currently being constructed are in general steel box girder and preflex girder bridges; however these types of breiges are less efficiency than PSC I-type girder bridges in terms of construction cost and maintenance. Therefore, in these study, structural efficiency of PSC I-type girders based on section parameters, concrete compressive strength and other design parameter is observed to develope new PSC I-type girder for long span bridges. As a results of analysis, most important design parameters that control the stress of the girder are found to be the top flange width and the height of girder. In this light, the relationship between the two variables is determined and cross-section details of the girder that most appropriates for the long span bridges are proposed. The use of high strength concrete appears to increase the general design span however the increase rate of the span from increasing concrete ultimate strength appears to be reduced depending on the span. Also, the optimal girder spacing is determined through the parameter studies of design span using the proposed girder.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.528-531
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• 2004

Nowadays, many of PSC bridges has constructed because high performance and long span bridge is required. Therefore, it is required that the evaluation of PSC bridges which retain various structure performance. In this study, nonlinear FEM analysis was performed with two parameter, concrete compressive strength and effective prestress force which is dominant factor for evaluating structural behavior of PSC bridge. Concrete compressive strength was adapted between 30Mpa and 100Mpa and effective prestress force was used the value which is considered effective rate for time-dependant effect. In the result of this study, it was showed that concrete compressive strength and effective prestress force is important factor for evaluating structural behavior of PSC bridge.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.680-685
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• 1998

Prestressed concrete I-girders were used in the bridge applications in the early 1950s. During the last four decades, the most widely used girder length of bridges have been below 30meters. The main objective of this study is to develope the alternative section for long span bridge which exceed 40 meters. The developed Bulb-Tee girder has a wide bottom flange to enhance the compressive strength and to allow placement of a large number of strands in the bottom flange. New bulb-tee shaped PSC girder sections are proposed in this paper. Splicing the technique for long span bridge girder to reduce the self weight is also proposed.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.149-159
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• 1998

The reasonable prediction of time-dependent deformation of prestressed concrete(PSC) box girder bridges is very important for accurate construction as well as good serviceability. The long-term behavior is mostly influenced by the probabilistic characteristic of creep and shrinkage. This paper presents a method of statistical analysis and sensitivity analysis of creep and shrinkage effects in PSC box been taken into account - model uncertainty, parameter variation and environmental condition. The statistical and sensitivity analyses are performed by using the numerical simulation of Latin Hypercube sampling. For each sample, the time-dependent structural analysis is performed to produce response data, which are then statistically analyzed. The probabilistic prediction of the confidence limits on long-term effects of creep and shrinkage is then expressed. Three measure are examined to quantify the sensitivity of the outputs of each of the input variables. These are rank correlation coefficient(RCC), partical rank correlation coefficient(PRCC) and standardiozed rank regression coefficient(SRRC) computed on the ranks of the observations. Three creep and shrinkage models - i. e., ACI model. CEB-FIP model and the model in Korea Highway Bridge Specification - are studied. The creep model uncertainy factor and the relative humidity appear to be the most dominant factors with regard to the model output uncertainty.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.81-94
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• 2010

This paper deals with the fracture simulation of UHPFRC girder with the interface type model. Based on the existing numerical simulation of quasi-brittle fracture in normal strength concrete, constitutive modeling for UHPFRC I-girder has been improved by including a tensile hardening at the failure surface. The finite element formulation is based on a triangular unit, constructed from constant strain triangles, with nodes along its sides and neither at the vertex nor the center of the unit. Fracture is simulated through a hardening/softening fracture constitutive law in tension, a softening fracture constitutive law in shear as well as in compression at the boundary nodes, with the material within the triangular unit remaining linear elastic. LCP is used to formulate the path-dependent hardening-softening behavior in non-holonomic rate form and a mathematical programming algorithm is employed to solve the LCP. The piece-wise linear inelastic yielding-failure/failure surface is modeled with two compressive caps, two Mohr-Coulomb failure surfaces, a tensile yielding surface and a tensile failure surface. The comparison between test results and numerical results indicates this method effectively simulates the deformation and failure of specimen.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.127-134
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• 2008

The response of a bridge can be influenced by span length, bridge's surface condition, vehicle's weight, and vehicle's velocity. It is difficult to predict accurate behavior of a bridge. In the current standard of specifications, such dynamic effect is defined by impact factor and prescribed to consider live load as to increase design load by means of multiplying this value by live load. However, it is not well understood because the Impact factor method differs from every country. Dynamic, static and pseudo-staitic field loading tests on PSC-I girder bridges were carried out to find out the dynamic property of the bridge. This paper is aimed to figure out actual dynamic property of the bridge by using field loading test. An empirical method based on impact factor is widely used and also argued. Displacement and strain response measured from the tests was compared with one from the empirical method. The former seems to be reasonable since it can consider actual response of a bridge through field tests.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.859-864
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• 2001

An effective live load model for analyzing probable maximum live load effects such as moment and shear in transverse direction was developed. The main procedure of this live load model is composed of four parts, i.e., firstly, determination of the appropriate influence lines in longitudinal direction, secondly, application of the characteristics of vehicles and traffic patterns in longitudinal direction, thirdly, determination of the appropriate influence lines in transverse direction, and fourthly, application of the characteristics of vehicles and traffic patterns in transverse direction. Through this procedure, the probabilistic distributions of maximum probable load effects are deduced in the form of probability density function (PDF) and/or cumulative density function(CDF). This live load model is able to consider local or global deterioration of bridges in the structural analysis.

• 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

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.193-200
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• 1998

The precast prestressed concrete girders of I-type section are frequently employed to design the short-to-medium span bridge. However, its beam depth is greatly increased as its span length is increased over than about 30m. Therefore, the economic and aesthetic effectiveness are rapidly decreased in case of the span length over 30m. The purpose of this paper is to verify the structural safety on the new spliced two span bridge and analyze the variation of member forces and stress distribution according to the construction stages and time. The new spliced technique is performed by partial post tensioning and release in the U-type girders. The structural characteristics of this technique is the introduction of secondary moment to reduce the bending moment by self weight of precast U-type girders constructed in simply supported beam type. So, it is expected that the structural efficiency of this spliced bridge may be improved more than other techniques.