Analysis On Main Cable Shape Of Long-span Suspension Bridge

Suspension bridge is a composite system made up of cable,tower,stiff girder and suspender. It has become the the bridge across the strongest because the main cable is tensioned and the material is utilized effieiently. With the development of science and social progress, the span of suspension bridge is also increasing. The cable is the main supporting component in the system, causing its linear to be susceptible to the construction conditions, temporary facilities and the impact of environmental temperature. So the cable-shaped accurate calculation is the key point of suspension bridge’s construction control.The main cable shape is the base of structure analysis after the completion of the suspension bridge, the main cable shape directly affects the stress distribution of the structure as a whole, also the main cable configuration will determine its own unstressed cable length, hanging boom location and unstressed length, these parameters are essential in design and construction control. Precise calculation and analysis of empty cable type and unstressed cable length is essential to reach the ideal state of the bridge, In the construction process of suspension bridge, the linear free cable status is very important control parameters. Once complete the erection of the main cable of suspension bridge, geometric alignment adjustment is very difficult, so research and analysis of the main cable line and the influence parameters of unloaded cable line is of great significance.In this paper, the first part is to study the accurate calculation of long span suspension bridge main cable shape and unstressed cable length as the goal, ansysing the the analytical method and finite element method of the main cable shape and unstressed stress cable length calculation, such as parabola method, segmented catenary method, finite element method etc. From the unloaded cable shape to finished main cable shape, and considering the construction stage shape of the main cable, complete suspension bridge main cable shape of the system analysis.It gives a variety of calculating results of the main cable shape based on the project, systematically study the pros and cons of various calculation methods.It gives the main cable shape and unstressed cable length accurately calculated recommendations of the same specifications suspension, the parabola method is not accurate, and is not suitable for the calculation of the main cable of long span suspension bridge, but it can be more accurate to get the shape of the cable with no boom. using segmented catenary method or the finite element method can get the precise alignment of the bridge and the unstressed cable length, accurate empty cable shape can be obtained by catenary method or the finite element method.The second part of this paper is to improve the main cable accuracy, ansys the main influence parameters of the cable shape, including elastic modulus of main cable, cable strand weight, main cable span and temperature. Relying on the project, It studied the mathematical rules between the unloaded cable line shape and the influence parameters, and the practical conclusion is drawn in order to provide technical support for the precise erection and adjustment of the unloaded cable line type of suspension bridges in practical engineering, and the relationship between the unloaded and finished main cable shape is analyzed, the change of the main points’ height of the finished main cable shape can be obtained directly by the change of the main points’ height of the unloaded main cable shape.