Analysis Of Static-Dynamic Mechanics Performance Of Long-span Suspension Bridges

The modern suspension bridge consisting of stiff girder and main cable is a system of flexible suspension. It becomes the first choice of long-span bridges for its great spanning capacity and beautiful structure model. To ensure suspension bridges' safety during construction and service, the research on the static and dynamic characteristic of the long-span suspension bridges is developed in this dissertation based on Sidu River Suspension Bridge in the west of national highway from Shanghai to Chengdu. The main contents and achievements are as following:1. The calculation theories of suspension bridges, including elastic theory and deflection theory in early-stage, finite displacement theory and analytic calculation theory used presently are introduced systematically. Moreover, the merits and faults of the latter two methods are compared and analyzed, which provides theoretical basis for the analysis of static and dynamic characteristic of suspension bridges.2. Based on the finite displacement theory, a calculation method simulating all construction stages of the suspension bridge is presented and put in practice to the Sidu River Suspension Bridge. The elevation variations of the control points of main cables and stiff girders are researched, the varying rules during construction process are found. The rigid connection sequence of the stiff girder is studied and that the construction method using full hinge to hoist stiff girder is confirmed to satisfy the requirements of internal force and alignment. The effects of P-â–³on the tower's allowable deviation and unbalanced horizontal force of every stage are thoroughly analyzed firstly. In addition, the main saddle's propulsion stages and values according to the tower's allowable deviation and unbalanced horizontal force are determined.3. The static performance of the suspension bridge under vehicular load and temperature is analyzed making use of the finite-element method. The feasibility that the live load can be calculated using linear second-order theory is confirmed. Based on the analysis of displacement and internal force responses of the main cable, suspender and stiff girder, the bias loading effect under the condition of half-range full-load is analyzed, which interprets the important function of main cable in bearing bias loading. Furthermore, the function effects of heating-up and cooling on the Sidu River Suspension Bridge are analyzed and the stress characteristics of all stressed structures of the suspension bridge under the action of temperature are concluded.4. The free vibration differential equations for the superstructures of suspension bridges are described. Meantime, the dynamic performances of Sidu River Suspension Bridge are analyzed using the finite-element method. In addition, the effects of rigidity variations of the main cable, suspender, stiff girder and tower and terminal condition etc on the bridge's dynamic performance are researched. Some conclusions are achieved which can provide references for the optimum design of suspension bridges.