Abstract
A simplified analytical method providing accurate unstrained lengths of all structural elements is proposed to find the optimized initial state of self-anchored suspension bridges under dead loads. For this, equilibrium equations of the main girder and the main cable system are derived and solved by evaluating the self-weights of cable members using unstrained cable lengths and iteratively updating both the horizontal tension component and the vertical profile of the main cable. Furthermore, to demonstrate the validity of the simplified analytical method, the unstrained element length method (ULM) is applied to suspension bridge models based on the unstressed lengths of both cable and frame members calculated from the analytical method. Through numerical examples, it is demonstrated that the proposed analytical method can indeed provide an optimized initial solution by showing that both the simplified method and the nonlinear FE procedure lead to practically identical initial configurations with only localized small bending moment distributions.
Highlights
It is well known that cables cannot behave as structural members until large tensioning forces are induced
13.889@9 = 125 m process, it was demonstrated that G.target configuration under dead loads (TCUD) can provide the ideal initial configuration of suspension bridges under dead loads
The initial shape of the main cable and the main girder obtained by unstrained element length method (ULM)(G) is exactly the same as that obtained by G.TCUD from the fourth and the fifth columns in Tables 6 and 7, which shows that G.TCUD and the corresponding ULM(G) enable the provision of an ideal initial state of extremely long self-anchored suspension bridges
Summary
It is well known that cables cannot behave as structural members until large tensioning forces are induced. In the case of self-anchored suspension bridges, bending moments by initial shaping analysis should almost vanish, except for local moments between anchored points, even though large axial forces in the main girders and the towers are inevitably induced due to the transfer of cable tensions Based on these observations, the following comments are provided to gain some insight into the mechanical behaviors of suspension bridges under dead load before a simplified analytical method to determine the optimized initial solution of suspension bridges. It should be noted that, in the case of self-anchored suspension bridges with a fabrication camber under dead loads, horizontal tension components of the main cable can induce extremely large negative bending moments in the main girder as the span length is increased To eliminate these moments and obtain the optimized initial state solution, the tension components of the hanger cables should be suitably decreased in order to exclude these bending moments, except for local moments.
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