Cable System Analysis And Construction Control Of Long-span Suspension Bridges

As the cables of long-span suspension bridges have significant flexible characteristics in the construction process, to ensure that the formed bridge to meet the design requirements, it must be strictly controlled in construction. Analysis and calculation are the important elements in the construction control of long-span suspension bridge. Based on the engineering background of Sidu River Bridge, which is the west part of Shanghai-Chengdu National Highway in Hubei Province, structure analysis and construction control study on the cable system of long-span suspension bridges are carried on in this thesis. The main research contents and achievements are as follows:In view of the drawbacks of the existed analytical methods for cable's shape calculation, an accurate analytical and calculational theory named Segmental Catenary Theory is established. iterative formulae for main design parameters of suspended rope are deduced in detail and the corresponding calculation program is compiled.Based on the Segmental Catenary Theory, analytical iterative methods for construction control calculation of catwalk are established, so as to confirm the shape of the catwalk, the unstressed length of the bearing cable, the end horizontal component force and vertical component force of the cable etc. The influences of the tower displacement which is caused by imbalance horizontal component force and the temperature variation upon the shape of catwalk are taken into consideration in the calculation method. The calculation results for the catwalk of the Sidu River Bridge show that the method is effective and reliable, which has clear mechanical concepts, fast convergence and high precision.According to the existing problems in the erection process of bearing cable, the erection principle is pointed out and the adjustment method for the shape of catwalk is put forward for reference.On the basis of the Segmental Catenary Theory, analytical iterative methods for construction control calculation of main cables are established, so as to solve the calculation problems of the shape of main cable in formed bridge, the unstressed length of main cable, tangent point's position of the saddle, shape and pre-offsetting of the datum strands, shape and pre-offsetting of the formed strands, the fixed site of the cable-clamps, unstressed fabrication length of the hanger etc. The impacts of the tower displacement and the temperature variation upon the shape of main cable are taken into consideration in the calculation method. The calculation for the main cable of the Sidu River Bridge shows that the method is effective and reliable, which has clear mechanical concepts and high precision.The method of controlling the datum strands and common strand is offered here. What must be emphasized is that the datum strands'elevation is changing during the erection process of cable strands, so the datum strands' elevation is different from that of the formed cables after the completion of the main cable's erection . The effects of the change of the cable length and that the change of span on the middle-span sag of the cable are analyzed, and a comparison is made between the Parabola Linear Approximate Calculation Method and the Segmental Catenary Nonlinear Exact Calculation Method. It is discovered that the calculation result of the two methods are very approximate.In this thesis, Sidu River Bridge is introduced as an example, the structure analysis and the construction control calculation to cable system of the suspension bridge is presented. The process is clear and the effect is well, which can be used for reference and application in similar projects.