• Geotechnical Engineering
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• v.13 no.2
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• pp.155-168
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• 1997

Lattice girder is a new steel support developed in Europe for the replacement of an existing H-shaped steel set, which is installed after tunnel excavation. Lattice girder has the following several advantages : 1. Lattice girder minimizes the amount of shotcrete shadow which happens to occur behind a steel support. 2. A triangular shape of lattice girder makes shotcrete placed efficiently. 3. Lattice girder provides a good bond strength for shotcrete, which makes the composite structure of lattice girder and shotcrete behave monolithic, and therefore, the rock load can be supported effectively by the lattice girder system, This paper presents the results from a model wall test, a strength test for shotcrete shot on the model wall and a strength test for the bond between lattice girder and shotcrete. These tests proved that lattice-girder system is superior to H-shaped steel-set system concerning the shotcrete rebound rate, the developed shotcrete strength and the adhesion characteristics.

• Structural Engineering and Mechanics
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• v.69 no.2
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• pp.193-204
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• 2019

This paper presents results from experimental and numerical studies on the response of steel-concrete composite box bridge girders under certain localized fire exposure conditions. Two composite box bridge girders, a simply supported girder and a continuous girder respectively, were tested under simultaneous loading and fire exposure. The simply supported girder was exposed to fire over 40% of its span length in the middle zone, and the two-span continuous girder was exposed to fire over 38% of its length of the first span and full length of the second span. A measurement method based on comparative rate of deflection was provided to predict the failure time in the hogging moment zone of continuous composite box bridge girders under certain localized fire exposure condition. Parameters including transverse and longitudinal stiffeners and fire scenarios were introduced to investigate fire resistance of the composite box bridge girders. Test results show that failure of the simply supported girder is governed by the deflection limit state, whereas failure of the continuous girder occurs through bending buckling of the web and bottom slab in the hogging moment zone. Deflection based criterion may not be reliable in evaluating failure of continuous composite box bridge girder under certain fire exposure condition. The fire resistance (failure time) of the continuous girder is higher than that of the simply supported girder. Data from fire tests is successfully utilized to validate a finite element based numerical model for further investigating the response of composite box bridge girders exposed to localized fire. Results from numerical analysis show that fire resistance of composite box bridge girders can be highly influenced by the spacing of longitudinal stiffeners and fire severity. The continuous composite box bridge girder with closer longitudinal stiffeners has better fire resistance than the simply composite box bridge girder. It is concluded that the fire resistance of continuous composite box bridge girders can be significantly enhanced by preventing the hogging moment zone from exposure to fire. Longitudinal stiffeners with closer spacing can enhance fire resistance of composite box bridge girders. The increase of transverse stiffeners has no significant effect on fire resistance of composite box bridge girders.

• 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.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.585-588
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• 2008

Resistance to lateral torsional buckling of steel I-girder (open section) is a very important design requirement. But, most studies of steel I-girder with corrugated webs were invested in shear behavior. Until now, most studies about Lateral torsional buckling of I-girder with corrugated webs have been based on Lindner.J's study. the study includes that the pure torsional constant of I-girder with corrugated webs doesn't different from that of I-girder with flat webs. This paper pesents pure torsional constant I-girder with sinusoidally corrugated webs by using finite element analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.841-846
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• 2001

The applicability of the concept of IPC(Incrementally Prestressed Concrete) girder which effectively reduces the depth of the conventional prestressed girders by introducing prestress in two different stages is theoretically reviewed in this research. Expressions on top and bottom stresses resulting from different loading stages are presented. Beneficial effects of IPC girder compared with those traditional prestressed girders are evaluated by investigating the girder depth for the same span or girder span for the same girder depth. Parking structures and ware house structures which need relatively longer span and are subject to large live loads are considered in comparison. It was found that the single or double tee slab designed by IPC concept could be built upto 50% longer in its span and upto 45% less in its depth compared to those of traditionally prestressed single or double tee slabs. In addition, the amount of prestressing tendons could be reduced.

• Structural Engineering and Mechanics
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• v.51 no.1
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• pp.39-66
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• 2014

This study deals with the design of bridge girder structures and consists of two parts. In the first part an optimal bridge girder topology is determined using a software based on structure compliance minimization with constraints imposed on the body mass, developed by the authors. In the second part, an original way in which the topology is mapped into a bridge girder structure is shown. Additionally, a method of converting the thickness of the bars obtained using the topology optimization procedure into cross sections is introduced. Moreover, stresses and material consumption for a girder design obtained through topology optimization and a typical truss girder are compared. Concluding, this paper shows that topology optimization is a good tool for obtaining optimal bridge girder designs.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.426-429
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• 2006

This paper focuses on the static behavior of prestressed and non-prestressed connections for the steel-concrete hybrid girder. Based on the experimental study, it is found that the girder with non-prestressed connection failed by local concrete failure at the connection area, and the studs are taken out from the concrete. In case of the girder with prestressed joint, the failure of the girder is initiated by the crack at the varying section area. The test results show that the girder with prestressed connection has higher load carrying capacity compare to the girder with non-prestressed connection by 12%. Therefore, the application of prestressing at the concrete-steel connection recommended for the more secure connection.

• Structural Engineering and Mechanics
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• v.61 no.3
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• pp.427-436
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• 2017

This paper presents an experimental and analytical investigation on the behavior of a U-shaped girder subjected to operation, cracking and ultimate loads. A full-scale destructive test was conducted on a U-shaped girder to study the cracking process, load-carrying capacity, failure mechanism and load-deformation relationships. Accordingly, the tested U-shaped girder was modeled using ANSYS and a non-linear element analysis was conducted. The investigation shows that the U-shaped girder meets the specified requirements of vertical stiffness, cracking and ultimate load capacity. Unfavorable torsional effect is tolerable during operation. However, compared with box girders, the U-shaped girder has a more transverse mechanical effect and longitudinal cracks are apt to occur in the bottom slab.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.185-192
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• 2003

This study presents the Optimum Evaluation of PS Concrete Deck and High Strength Two Plate Girder System. Recently, for the simplification of structure and the long length of bridge, a small number girder bridge which minimized a number of girder by two is much designed and constructed. For the structural analysis, a finite element formulation considering with even the matter of torsion in the three-dimensional problem is presented. And connectively, for the design of optimum section, an algorithm of optimum design is developed. The section of a small number girder bridge which constituted of two girders and PS Concrete Deck is optimized by using optimum program developed in this study. and two girders bridge refered in this study is proved a efficiency and a economy by being compared and checked to the general plate girder bridge with five girder and Reinforced Concrete Deck.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.13-23
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• 2000

In this study, an flexural test on half-scale spliced PSC-I girder was conducted to verify the efficiency of the long span spliced girder as suggested by the Korean Highway Design Specification. The experimental results showed that the specimens developed a complex failure mode due to flexural-compression and torsional stress. The cracking moment of each girder was higher the experiment than was calulated by the ACI and the ultimate strength were the almost same. To estimate the safety and the structural efficiency of the spliced girder, the proposed Yielding Resistance Index(YRI) and ductility index by American Concrete Institutes were used based on the energy concept. The proposed YRI defined the ratio of crack resisting energy and the total energy calculated from load-displacement relationship. Based on the analysis of YRI and ductility index, the flexural behavior of the spliced girder was found to be efficient. Through the experimental results, the structural behavior of proposed spliced PSC I-type girder for long span bridge was found to be more efficient than the exsisting PSC I-type girders.