Investigation of initial construction stagesof incrementally launched post-tensioned concrete box bridges

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2021-2-12

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Altınsoy, Zafer

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The incrementallaunching method is a fast, popular construction method for post-tensioned concrete bridgeswith mid-span size.It does not require scaffolding under the deck;therefore,it is especially preferred when a bridge passes over a deep valley, high traffic area,or an environmentally sensitive area.Due to its dynamic natureof the launching, the design and optimization of incrementally launching bridges require special attention.A launching nose is used to decrease the moments on the bridge deck during the launch.Infinite beam model and semi-infinite beam models are the most commonmodels for the optimization of the launching noses. Bothmodels are based on advanced stages of the construction; however,to have an accurate design, initial construction stages should alsobe investigated. In this thesis, a model for the initial construction stages is developed.The new initial stage model includes the movement of the newly casted section and thecantileverdeflection of the launching nose,which arenot included in the current advancedstage models.The initial stage model is compared with the current advanced stage models. It is observedthat moments in the initial stages are higher than the advanced stage moments in some cases.Therefore, the initial stages also should be checked during thedesignstage. Effects of launching nose’sdesign parameters(length, unit weight,and stiffness)on the maximum deflection areinvestigated.It is found that all three parameters are affectingthe maximum deflection,and launching nose length is the most effective parameter.

Subject Keywords

Incremental Launching Method, Launching Nose, Post-tensioned Concrete Bridges, Prestressed Concrete Bridges, Optimization

URI

https://hdl.handle.net/11511/89771

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

Z. Altınsoy, “Investigation of initial construction stagesof incrementally launched post-tensioned concrete box bridges,” M.S. - Master of Science, Middle East Technical University, 2021.