Analysis Of Construction Control On Main Cable System Of Long-span Suspension Bridge

In recent years, there have been rapid developments of long-span suspension bridge in China. Suspension bridge, with its strong ability and soft beautiful shape, becomes the first choice of long-span bridge structure in domestic and international. Taking the Saiwudiegeer Bridge for example, this paper centers on the erection of main cable and researches the analysis of construction control. Main contents presented in the paper are as follows:First of all,Based on segmental linear theory and catenary cable element theory, the paper obtained the truth cable shape of finished-bridge, taking geometric parameter, the cable design sag and the coordinate of saddle, as control target. Considering correction of main cable at saddle, the non-stress length and the coordinate of cord clip can be figured out according to the theory that the non-stress length of cable will not change during construction object.The second,This paper utilized the FEM to establish the model of suspension bridge based on the finite displacement theory. By alternate nonlinear analysis of inversion and positive direction method, the initial cable shape and pre-deflection of saddle can be approached generally. Based on experiences in practice, the paper made a detailed instruction about how to adjust the cable to design value. The absolute height of pendant vertex is measured as Reference cable's control target, while the general cable's is the relative height with reference cable. There is a natural sequence of construction, the cable shape shall be adjusted in the following order: first in middle span, second in side span and lastly in the anchorage. The pushing space and the right pushing moment of every construction stage should be calculated, In order to make the stress of the tower close to perfect state. The pushing space should be is equal to the free sliding displacement of saddle at the top of cable toward. The right pushing moment can be agreed according to the superior limit of pre-deflection, generally use 10 percent of the superior limit as control value.At last,An example is used to verify that, the way of calculating tension in fixed-end or simply supported boundary model seems to be inapplicable to the situation of short cable. Based on the classical beam theory, the paper supposed the short cable's boundary is the combination of fix-end and simply supported boundary. Considering the mathematical relationship between frequency and vibration mode, A Equation Set can be founded and the tension of the cable can be figured out.The results indicate that this method can offer a new way for calculating the force of cable,and it can be extended in the same practices.