İtme sürme yöntemiyle yapılan ardgermeli kutu kesitli betonarme köprülerin inşaatlarının ilk aşamalarının incelenmesi

The incremental launching method is a fast, popular construction method for post-tensioned concrete bridges with 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 nature of 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 common models for the optimization of the launching noses. Both models are based on advanced stages of the construction; however, to have an accurate design, initial construction stages should also be 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 the cantilever deflection of the launching nose, which are not included in the current advanced stage models. The initial stage model is compared with the current advanced stage models. It is observed that moments in the initial stages are higher than the advanced stage moments in some cases. Therefore, the initial stages also should be checked during the design stage. Effects of launching nose's design parameters (length, unit weight, and stiffness) on the maximum deflection are investigated. It is found that all three parameters are affecting the maximum deflection, and launching nose length is the most effective parameter.