Analysis of Target Configuration for Concrete Cable-stayed Bridges Considering Construction Stages and Creep Phenomenon Jae Woong Hwang
ABSTRACT Since the lateral stiffness of a cable is developed from applied tensions, no unique undeformed configuration of a cable structure is defined in the stress-free state. Therefore, deformed shape of a structure under dead loads is used as the reference configuration, and is referred to the target configuration under dead loads or the initial equilibrium configuration. In addition, the process determining the initial tension or the length of cables for the satisfying the target configuration is defined as initial equilibrium state analysis. The several established methods analyzed initial equilibrium state are the initial member force method, the geometric constraint method, and the optimal TCUD analysis method which is based on both the geometric constraint method and the minimizing energy method. However, the previous analysis methods are developed for the structural system had no creep phenomenon. Therefore, these methods don¡¯t apply to concrete cable-stayed bridges. This thesis presents the analysis of target configuration for concrete cable-stayed bridges considering construction stages and creep phenomenon. Overtime, the geometry configuration of a concrete cable-stayed bridge is changed by the creep phenomenon although it satisfied the target configuration at the initial equilibrium state. Therefore, this thesis proposes the approach based on Newton-Raphson method for obtaining the undeformed length of cables, which assimilate deformed shape of a structure to target configuration at the specified target time when structural geometry configuration is satisfied with target configuration. A steel structure is obtained only unique configuration although it had different construction stages and processes if it constructed under elastic limit condition. However a concrete structures increasing the additional deformation as a creep deformation except for the elastic deformation has a variety of configurations according to the construction stages and processes. Therefore, the proposed method should apply to concrete cable-stayed bridges considering their construction stages. A numerical example is performed to demonstrate the validity and the effectiveness of the proposed analysis method. The example bridge constructed using one-side cantilever method has 104m span length and 12 cables.
Key Word Concrete cable-stayed bridge, Creep, Target configuration, Displacement sensitivity, Analysis of construction stage
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