New Method for Calculating the Preoffsetting Value of the Saddle on Suspension Bridges Considering the Influence of More Parameters

To seek a proper way to calculate the preoffsetting value of saddle on a suspension bridge, some influences of structural parameters on the preoffsetting are considered, then a new method for the preoffsetting value of saddle is proposed. On the basis of the relationship of the main cable and saddle, equilibrium equations, geometric equations, and physical equations are deduced. Then, the equations are solved by the Newton-Raphson iteration method to derive the Jacobian influence matrix of preoffsetting. For convergence of the numerical calculation, constraint conditions and the range of initial values are given. Through comparison of the measured value in a 1/30-scale model test and the calculated value, the reliability of the new method is confirmed. Finally, parametric analysis of preoffsetting shows that (1) with an increase of the saddle radius, saddle preoffsetting increases in the middle-span direction; (2) with increases of the side/middle-span and rise/span ratios, saddle preoffsetting increases in the side-span direction; (3) the influence of cable self-weight on saddle preoffsetting is negligible; (4) with an increase of unstressed cable length in the side span, saddle preoffsetting increases in the middle-span direction; and (5) with an increase of unstressed cable length in the middle span, saddle preoffsetting increases in the side-span direction.