Study Of Construction Control Of Long-Span Suspension Bridge

While span of suspension bridge is increased, the construction control is more and more important to make the structure stress and geometric shape close to design state. Taking the Yichang Changjiang highway bridge as an example, analysis of construction control of suspension bridge is completed.Based on virtual lamina element theory, a 3D finite element model of suspension bridge in construction period is build up for construction control analysis. Due to advantage of virtual lamina element theory, by adjusting properties of element materials, the finite element model can be simply modified to simulate the steel box beam lifting construction period.Analysis of tower stress and geometric shape of structure during steel box beam lifting construction period is completed. The frequent short steps saddle pushing principle is presented, it means saddle pushing is frequent and space of each pushing is short. Contrastively calculating result shows that frequent short steps saddle pushing scheme makes tower stress more close to perfect state and it is beneficial to safety of structure.Based on field measuring, a temperature field and temperature gradient curve of steel flat box beam are presented. In this temperature gradient curve, the sunshine temperature difference between roof and floor is high to 30℃. Contrastively calculating of temperature stress in steel box beam shows that this temperature field is more close to the actual situation.In the case of sunshine temperature difference between roof and floor is 30℃, the temperature stress in roof of steel box beam is high to 100MPa, even 135MPa (the yield strength of Q345-94 steel is 345MPa). It means that temperature stress maybe vital factor in steel box beam design. In temperature analysis of steel box beam segment, the boundary condition definition is important. Contrastively calculating between actual boundary condition and fixed end boundary condition shows that their calculating results are very close. Therefore, in temperature stress analysis of steel box beam of long span suspension bridge, the whole box beams can be deem as an approximate infinitely long beam, then take out one box beam segment as a subject with the fixed end boundary condition, the calculating result will be close to the actual situation.For study of static load test of Yichang Changjiang highway bridge, a 3D virtual lamina element model of suspension bridge is build up. Theoretical calculation result accord with measure value.Based on analytic method, several controls parameter such as non-stress length of cable and datum strand shape in main cable erection period are analysed. The elevation of strand is changed in main cable erection period. So the elevation of datum strand in cable finished stage is different with that in main cable erection stage. Subsection linear function is used in temperature field of strand. The effect to strand shape caused by temperature is analysed.A method of length amending of straddle suspender cable in main cable clip is presented. Analytic expressions was offered to calculate the tangent point and its corresponding angle. Series expansion and numerical integral method were also investigated to calculate the accurate length of ellipse arc. Analysis results show that the method have high precision and rapidity of convergence.