Simulation Analysis For Construction Stages Of Self-anchored Suspension Bridges

In recent years, self-anchored suspension bridges are increasing used by engineers for their aesthetic look, convenient adaptability and low cost. They are becoming more long in the span and large in the scope. No matter for construction or calculation of construction simulation, self-anchored suspension bridges differ from conventional suspension bridges. Analysis for construction stages of self-anchored suspension bridge is the key to determine whether its location takes place accurately. Based on the construction stages of self-anchored suspension bridges, the reasonable construction state of each construction stages is calculated, which is used to judge whether the current construction state coincides with. This is the important guarantee to reach the designed bridge's completion state safely and accurately.This paper, based on Wanxin Self-anchored Suspension Bridge in Fushun City, utilizes the general FEM program to establish the whole bridge model. According to the construction stages of self-anchored suspension bridges, the forward analysis method and iterative produce of assumption—calculation—comparison—update assumption are used for calculation of each construction stages. The hanger forces, the internal forces of stiffening-girder and the main cable shapes of each construction stages are obtained by the methods. When supposing the construction ideal initial state in the first time, the initial state model is established according to the cable's span central sag in the bridge's completion state, the main cable shape in the bridge's completion state is obtained by iterative calculation. The cable design sag, rope site and the deck design shape in the bridge's completion state are taken as the geometric parameter of control target. The stress of stiffening-girder in self-anchored suspension bridges is related with the hanger force, the hanger force in the rational completion state is obtained by the stiffness holding continuous beam in this paper. Simulation analysis for construction stages is obtained by hanger force as concentrate force under the action of main cable and stiffening-girder.According to example computation, the following conclusions are obtained: 1) The stiffening girder is constructed at the elevation of the bridge's completion state. The method that hanger force in the rational completion state is obtained by the stiffness holding continuous beam is convenient. The hanger forces are uniform besides the hangers near the pier.2) The method is effective, that the cable design sag, rope site and the deck design shape in the bridge's completion state are taken as the geometric parameter of control target, iterative produce of assumption—calculation—comparison—update assumption are used for calculation of main cable shape in the free-cable and completion state, geometric form and internal forces of each construction stages.3) The free-cable shape is parabolic. The main cable shape changes after a series of construction stages. The cable shape in the bridge's completion state is not parabolic, nor catenary. It is between parabolic and catenary.4) After the suspension cables being tensioned the first, the weight of stiffening girder is transferred to the main cable through the hanger. The stiffening girder is separated from the supports. The moment diagram of stiffening girder at the main cable scope is the same as a continuous multi-span girder bridge, and the values of moment are small.5) Before the suspension cables being tensioned the second, the whole main cable deforms downward under the additional dead load. The deformation of the stiffening girder is "S" shape, side span girders are upward and middle span girder is downward. The blending moment diagram of stiffening girder at the main span is the same as a continuous three-span girder bridge. After the suspension cables tension finished, the additional dead load is transferred to the main cable through the hanger. The blending moment diagram of stiffening girder in the main span is the same as a continuous multi-span girder bridge. Due to weight and the additional dead load and strong concentrated force of main cable, the moment of anchoring span differ significantly.