Initial Equilibrium States Analysis by Optimization of Concrete Cable-stayed 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 stress-free 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 cable-stayed bridge is changed by the time-dependent behavior although it satisfied the target configuration at the initial equilibrium state. The established method analyzed initial equilibrium state of concrete cable-stayed bridge 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 the time-dependent 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 cable-stayed bridges by applying the suggested methods of steel cable-stayed bridges which is minimizing bending moment of the frame structures and hybrid TCUD analysis. A new type of concrete cable-stayed 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 time-dependent behavior of concrete such as creep, shrinkage phenomenon and aging effects, effects of steel-concrete 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 cable-stayed bridge at the target time in the initial equilibrium analysis.
Key Word Concrete cable-stayed bridge, Concrete filled tubular, Optimization, Initial equilibrium state, Sensitivity Analysis
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