The Analysis Of Pre-camber Setting And Creep For Single Pylon Cable-stayed Bridge

The cable-stayed bridge have to go through a process of phased construction. The stiffness of the structure during the construction process is smaller than a bridge when it is done, geometric nonlinearity is more prominent. Load of the structure (weight, construction machinery, pre-stress, etc.) is imposed in the construction process step by step, every stage is accompanied by change of structural form; creep and shrinkage of the Component materials; the change of the boundary constraint; pre-stressed tension and system conversion, Therefore, the cable-stayed bridge Pre-camber set is more complex than the average bridge, the dead load distribution of the cable-stayed bridge is one of the important criteria that measures the design, due to the practical constraints, requirements that want each cable-stayed bridge to meet the zero moment is unrealistic. Thus, if the cable-stayed bridge structure system was once identified, we can always find a set of cable-stayed force, so that if the structure is affected by the determined loads, some target that reflect the mechanical properties will be optimal, ii is the optimal goal under the target. If the structure parameters won’t change, the dead load optimization of cable-stayed bridge dead load will be converted to cable-stayed cable power optimization problem, and also it provides a premise for the pre-camber settings optimization.Traditional cable-stayed bridge initial tension appears that internal forces is not closed and other shortcomings in the practical application. First, bridge cable force optimization has three categories which they have their own advantage and shortcomings at present, the cable force optimization that has specified the stress state, Unconstrained Cable Force optimization and constrained cable force, then there are different methods to determine the initial tension。 The analysis showed that optimization of one goal will be inevitably at the expense of the cost of another goal.The paper take Jiangxi River Bridge project as background, use finite element software Midas/Civil as the tool. It will use a variety of constraints that determine optimal cable forces to meet bridge-done stage, and then use the method of unclosed coordinate force to draw the of the initial tension of construction phase, checking the stress in the construction and bridge-done phase,at last the paper considers creep in order to determine the pre-camber settings.After analysis, the influence matrix method formulated by some objective function is able to include various influence and and can get different target function, mechanical properties will be tested after calculating of finished bridge to meet bridge requirements, this paper that combines with finite element software use the lack of fit force method, it can avoid the geometric non-linear factors caused by creep and cable sag, it can mostly reduce the unclosed phenomenon, after initial force is calculated, force will be tested in actual use phase to meet the construction safety requirement; after the theoretical calculation, we can see the camber vertex is in the left of the span, about a quarter span place, creep make significant influence to the linear of construction stage and finished bridge stage, it accounts for about20%of the camber; it has little difference between CEB-FIP standard and China(JTG D62-2004) standard.