• Steel and Composite Structures
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• v.9 no.4
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• pp.325-348
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• 2009

This paper is concerned with steel-concrete composite plate girders curved in plan. At the design stage these girders are assumed sometimes to act independent of the deck slabs resting on them in order to simplify the analysis. The advantage of composite action between the steel girders and concrete deck is not utilized. Finite element modeling of such composite action in plate girders is considered in this paper. Details of the finite element modeling and the non-linear analysis of the girders are presented along with the results obtained. Tension field action in the web panels similar to those observed in the straight plate girders is also noticed in these girders. Finite element and experimental results in respect of curved steel plate girders and straight composite plate girders tested by other researchers are presented first to assess the accuracy of the modeling. Effects of parameters such as curvature, steel flange width and web panel width that affect the behavior of composite girders are then considered in the analyses. An approximate method to predict the ultimate strength of horizontally curved composite plate girders is also presented.

• Structural Engineering and Mechanics
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• v.82 no.3
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• pp.343-354
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• 2022

An understanding of the mechanism of concrete girders repaired with CFRP plates and its influence on the dynamic parameters is presented in this paper. Dynamic parameters are governed by the relationship with the physical properties of concrete girders and CFRP plates as well as the adhesive layer between them. A brief explanation of the mechanism of the composite action of concrete girders repaired with CFRP is also given in this paper. Experimental work was carried out to validate the theory of the composite action. The results show a decrease in the modal parameters of CFRP repaired girders that were turned over during the repair procedure, which contrasts with the proven static-based results that CFRP plates increase the stiffness of repaired girders. The composite action theory has explained the results based on the tension and compression forces' growth at the adhesive layer between the CFRP plates and girder surface during the repair procedure. Other girders were prepared and repaired without turning over in order to avoid tension and compression forces at the adhesive layer. The experimental results show an increase in the dynamic parameters of CFRP repaired girders that were not turned over during the repair procedure, which aligns with the static-based results. The study concludes that the dynamic parameters are excellent indicators for the assessment of CFRP repaired concrete girders. The study also suggests that researchers should not turn over damaged concrete girders to repair them with CFRP plates if they intend to study the dynamic parameters, in order to avoid the proposed composite action effect on modal parameters.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.3
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• pp.145-152
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• 1987

This paper suggests a method for the analysis of box girders which are subject to the membrane and the plate bending actions, Moreover, the method is applied to the box girders under distributed loads which have various geometrical types of cross sections and are made out of different materials. The approach is based on the finite element technique in which the structure is considered to be a spatial assemblage of flat plate elements and the deformations of the plates are to be approximated with 9-noded parabolic isoparametric elements. The results are summarized as follows. 1.In all models, the larger the widths of top flange inside of web are, the larger the vertical deflections are. 2.The maximum transverse and longitudinal moments in the composite box girders are judged to be larger than those in the RC box girders. 3.The transverse and the longitudinal moments in top flange of composite box. girders are larger than those in that of the RC box girders. 4.The transverse and longitudinal moments in web and bottom flange of the composite box girders are estimated to be very small in compare to those in web and bottom flange of the RC box girders.

• Structural Engineering and Mechanics
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• v.70 no.3
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• pp.257-267
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• 2019

Expressions for the calculation of ductility index for concrete girders with different ratios of prestressed and classical reinforcement were proposed using load-displacement, load-strain and load-curvature relation. The results of previous experimental static tests of several large-scale concrete girders with different ratio of prestressed and classical reinforcement are briefly presented. Using the proposed expressions, various ductility index of tested girders were calculated and discussed. It was concluded that the ductility of girders decreases approximately linearly by increasing the degree of prestressing. The study presents an expression for the calculation of the average ductility index of classical and prestressed reinforced concrete girders, which are similar to the analysed experimental test girders.

• 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.54 no.6
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• pp.1267-1281
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• 2015

Carbon steel plate girders have been used on a large scale in the building industry. Nowadays, Lean Duplex Stainless Steel (LDSS) plate girders are gaining popularity as they possess greater strength and are more impervious to corrosion than those that are constructed from carbon steel. Regardless of their popularity, there is very limited information with regards to their shear behavior. In this paper, the non-linear finite element analysis was employed to investigate the shear behavior of LDSS plate girders. Parameters considered were the web thickness, the flange width, and the girders aspect ratio. The analysis revealed that although the shear behavior of the LDSS girders was no different from that of carbon steel plate girders, it had obviously been affected by the non-linearity of the material. Furthermore, the selected parameters were found to pronounce effect on the shear capacity of the LDSS girders. That is, the shear capacity increased considerably with web thickness, and increased slightly with flange width. However, it was reduced as the aspect ratio increased. Comparisons between the finite element analysis failure loads and those predicted by the current European Code of Practice revealed that the latter underestimated the shear strength of the LDSS plate girders.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.201-214
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• 2013

Lattice girders are widely used as a substitute for H-steel ribs at domestic tunnels. However, lattice girders have a weak point in terms of the support capacity compare to H-steel ribs because of the lower stiffness and the weakness of the welded parts. To improve the weakness of the lattice girder, reformed lattice girders are developed in Korea by adding one more spider and having flat welded surface. Laboratory tests and field measurements were performed for the original and the reformed lattice girders to evaluate the performance of the reformed lattice girders. According to the laboratory compression test, reformed lattice girders have 16% higher load bearing capacity than that of original lattice girders. Reformed lattice girders are more stable than original lattice girders because reformed lattice girders tend to bend less according to the field measurements.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.3142-3146
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• 2011

This paper introduces improved prestressed concrete (PSC) girders for the railway bridges. In order to improve performance of conventional PSC girders, various types of PSC girders are either under development or have already been applied in railway bridges. Incrementally prestressed concrete girder is one of these newly developed girders. According to the design concept, these types of PSC girders have the advantages of requiring less self-weight while having the capability of longer spans. However, the tensional failure of top flange is one of the critical issues at the first prestressing stage. To effectively provide initial section stiffness of PSC girders, concrete block on the top flange is used in this study. The efficiency of the proposed structures, compared with conventional girders and improved ones, is successfully demonstrated in the example.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.507-512
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• 2002

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 30 meters. The main objective of this study is to develope the alternative section for widely spaced girder of 30 meters span bridge. Girder spacing, the number of strands and compressive strength of concrete are major parameters for widely spaced girders. The optimal girder spacing is determined through the parameter studies of design using widely spaced girders. 30m span bridges of widely girder spacing must use high-strength concrete. Although the basic unit cost of concrete is higher for high-strength concrete, it may be partially or even fully offset by reduced quantities of concrete as result of the smaller number of girders used. High-strength concrete girders have more prestressing strands per girder, but the total number of strands for all of the girders is less than that required for the larger number of normal-strength concrete girders. It could design PSC-I Birdge with widely spaced girder owing to high-strength concrete.

• Tunnel and Underground Space
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• v.6 no.2
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• pp.122-130
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• 1996

Generally the NATM technique uses shotcrete, rock bolts, H-beam steel ribs, and concrete lining for the tunnel support in Korea. Among them, H-beam steel ribs are extremely heavy and difficult for workers to handle. Therefore, especially in Europe, lattice girders are being used instead of H-beam steel ribs for tunnel support. Lattice girders have basically the same function as H-beam steel ribs in tunnelling. The main advantages of using lattice girders compared to H-beam steel rib supports are as follows: 1) lattice girders have relatively a low weight enough to be easily lifted and installed by labors and 2) they create a more effective bond with the shotcrete. The purpose of this study is to evaluate the effectiveness and applicability of lattice girders compared to H-beam steel ribs used in construction tunnel sites and to show that lattice girders can be adequately applied in domestic tunnel construction sites as a new tunnel support system.