An Initial Equilibrium State Analysis of Cable Stayed Bridges by Minimizing Energy of Structures and Optimal Correction of Profiles Chang Hyun Kim
ABSTRACT The undeformed geometry of cable cannot be defined because the lateral stiffness of a cable is developed from applied tensions. So either the unstrained length or the tension of cable must be calculated from the deformed geometry. Determining either unstrained length or tension which satisfies the given geometry in equilibrium is defined as initial equilibrium state analysis. The initial member force method and geometric constraint method have been utilized for the TCUD analysis, but the initial member force is sensitive of initial tension values and geometric constraint method developed excessive cable tensions. So this paper presents a new TCUD analysis, the optimal TCUD analysis, which is based on both the geometric constraint method and the minimizing energy method. The proposed method can overcome the aforementioned drawbacks of the initial member force method and geometric constraint method. So the proposed method reproduces the target profile of the deck and pylon which is made by designer, and minimizes moments in deck and pylon. Also, we can find optimal profile of the structure by adjusting optimal factor. There are forward analysis and backward analysis in construction stage analysis. Forward analysis is performed by actual sequences of construction and backward analysis is performed by backward step construction using results of the TCUD analysis and we used to perform the backward analysis to find initial tensions. But if structures undergo no large deflection and plastic deform, both forward analysis and backward analysis reproduce same results. Two numerical examples are performed to demonstrate the validity and the effectiveness of the proposed method compared with previous studies.
Key Word Optimal TCUD analysis, TCUD, Initial Equilibrium analysis, Elastic catenary cable, Construction stage analysis, Cable stayed bridge
|