• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.101-108
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• 2012

The orthotropic steel deck bridge made by using relatively thin steel plate, and structural members such as transverse and longitudinal ribs, cross beam, etc. in the bridge are fabricated with complex shape by welding. Therefore, the possibility occurring deformation and defects by welding is very high, and stress states in the welded connection parts are very complex. Also, the fatigue cracks in orthotropic steel deck bridge are happening fromthe welded connection parts of secondary member than main member. However, stress evaluation for main members is mainly carried out in the design process of the bridge, detailed stress evaluation and characteristic analysis is not almost reviewed in the structural details which fatigue crack occurred. For the orthotropic steel deck bridge with open ribs which has been serviced for 29 years, in this study, the cause of fatigue crack is investigated and the fatigue safety of the bridge is examined based on fieldmeasurement by the loading test and real traffic condition. Also, structural analyses using gridmodel and detailed analysis model were carried out for the welded connection parts of longitudinal rib and diaphramthat fatigue crack occurred. Additionally, the behavior characteristics due to running vehicles were investigated by using influence area analysis for these structural details, and the occurrence causes of fatigue crack in the target bridge were clarified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.235-249
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• 2011

A new form of I-type PSC bridge girder, which has hole in the web, is proposed in this paper. Three different concepts were combined and implemented in the design. First of all, a girder was precast at a manufacturing plant as divided pieces and assembled at the construction site using post-tensioning method, and the construction period at the site will be reduced dramatically. In this way, the quality of concrete can be assured at the manufacturing factory and concrete curing can be well controlled, and the spliced girder segments can be moved to the construction site without a transportation problem. Secondly, a numerous number of holes was made in the web of the girder. This reduces the self-weight of the girder. But more important thing related to the holes is that about half of the total anchorages can be moved from the girder ends into individual holes. The magnitude of negative moment developed at girder ends will be reduced. Also, since the longitudinal compressive stresses are reduced at ends, thick end diaphragm is not necessary. Thirdly, Prestressing force was introduced into the member through multiple stages. This concept of multi-stage prestressing method overcomes the prestressing force limit restrained by the allowable stresses at each loading stage, and maximizes the magnitude of applicable prestressing force. It makes the girder longer and shallower. Two 50 meter long full scale girders were fabricated and tested. One of them was non-spliced, or monolithic girder, made as one piece from the beginning, and the other one was assembled using post-tensioning method from five pieces of segments. It was found from the result that monolithic and spliced girder show similar load-deflection relationships and crack patterns. Girders satisfied specific girder design specification in flexural strength, deflection, and live load deflection control limit. Both spliced and monolithic holed web post-tensioned girders can be used to achieve span lengths of more than 50m with the girder height of 2 m.