Initial Equilibrium States Analysis by Optimization of Concrete Cablestayed Bridges Considering Creep and Shrinkage Kil Je Jung
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 stressfree state. Therefore, either the unstrained length of cable must be calculated from the given configuration. Determinimg either unstrained length or tension that satisfies the target configuration is defined as an initial equilibrium state analysis. Overtime, the geometry configuration of a concrete cablestayed bridge is changed by the timedependent behavior although it satisfied the target configuration at the initial equilibrium state. The established method analyzed initial equilibrium state of concrete cablestayed bridge based on NewtonRaphson method for obtaining the undeformed length of cables, which assimilate deformed shape of a structure to target configuration at the specified target time when the timedependent behavior will be ended. Althogh the previous analysis guarantees convergence and satisfies exactly the target configuration at target time, that method has a problem of developing excessive bending moment of a frame structure. For overcoming the demerit, this paper presents an initial equilibrium analysis of concrete cablestayed bridges by applying the suggested methods of steel cablestayed bridges which is minimizing bending moment of the frame structures and hybrid TCUD analysis. A new type of concrete cablestayed bridge using concrete filled tubular girder is performed to demonstrate the validity and the effectiveness of the proposed analysis method. This thesis is considering the timedependent behavior of concrete such as creep, shrinkage phenomenon and aging effects, effects of steelconcrete composite beam and casting delay by the construction stage. The proposed method is capable of considering the geometirc shape as well as the bending moment of a concrete cablestayed bridge at the target time in the initial equilibrium analysis.
Key Word Concrete cablestayed bridge, Concrete filled tubular, Optimization, Initial equilibrium state, Sensitivity Analysis
