Joint Iteration Method of unloaded Cable Shape and Pre-displacement of Main Cable Saddle for Long-span Suspension Bridges

In this paper, a new method for calculating the unloaded cable shape and main cable saddle pre-displacement in the construction of long-span suspension bridges is proposed, which is called the joint iterative method (JIM). In this method, the first iteration does not require presupposing the saddle pre-displacement, and the results of the unloaded cable shape obtained in each subsequent iteration cycle will be mined to guide the saddle pre-displacement correction in the next iteration. This method uses simplified cable models and convergence conditions different from classical methods. In the simplified model of main cable mechanics, equal horizontal component of suspension bridge on both sides of main tower is taken as implicit condition, and equal unstressed cable length of each span of main cable is taken as convergence condition in iteration. Using this method, the pre-displacement of the main saddle and the unloaded cable shape of the Yingwuzhou Yangtze River Bridge is calculated by MATLAB program and compared with its designed value. The results show that this method requires few iterations and has high speed and accuracy.