Mechanical Analysis of Ultra-Wide Tower System in Cable Lifting Construction of a Y-Shaped Arch Bridge

The under-construction medium-bearing space Y-shaped steel box-rib arch bridge is the first of its kind in China as a new type of shaped arch bridge. This paper takes the most important structural tower system in its cable lifting construction as the background， and increases the transverse width of the tower to 47.6 m by adjusting the setting of universal bars on the basis of the conventional tower to form an extra-wide tower， and uses the analytical method and finite element analysis method to establish the SAP 2000 numerical model to analyze the overall and internal components of the integrated system of cable and buckle tower for stiffness， strength and stability refinement to verify whether the extra-wide tower has good mechanical performance. The analytical formula for the force of the lifting cable on the tower is given， and the force of the lifting cable on the tower is calculated by this formula. Considering the wind cable as a spring unit capable of withstanding tension and compression， formulas are given for converting the spring stiffness and for calculating the strain value corresponding to the initial tension of the wind cable. Design recommendations are given for wind cables and tower rods settings： after setting a certain initial tension of wind cable， it can effectively reduce the non-linear effect of wind cable drape and increase its restraining effect on the tower， and can pre-deflect the tower by the initial tension of wind cable to achieve the purpose of making the maximum forward and backward displacement of the tower tend to be close. The universal rod webs have a small radius of inertia in the direction of the weak axis and a relatively large length and slenderness， so the stress increase after considering the stability is large and should be given attention when designing.