Determining Of The Reasonable Finished State And Analysis Of Construction Process Of Cable-stayed Suspension Bridge

The cable-stayed suspension bridge is a combination of two kinds of bridge type,which combines cable-stayed bridge and suspension bridge.It can play the advantages of cable-stayed bridge and suspension bridge simultaneously.It has great potential in the super-long-span bridge.In this paper,a finite element analysis model is established through BNLAS based on the design of a cable-stayed suspension bridge with a main span of 1408 m.The following work is done on the determination of the reasonable finished state and the analysis of the construction process in this paper:The two kinds of bridge constant load state were established according to the minimum bending energy method and the rigid support continuous beam method by considering the balance of the tower.Then the internal force and the cumulative displacement of two states were compared and analyzed.The comprehensive comparison shows that the rigid support continuous beam method which considers the force balance of the tower is more reasonable.The following models were based on the dead load condition of the bridge as a reasonable completion status.Then,according to this method,the dead load states of the bridges under five different load distribution ratios of transition zone were calculated,and their similarities and differences were compared.The analysis of moving load of service stage and integral overheating and cooling were carried out for the models with different load distribution ratios in the transition zone.The internal forces and deformations under load during service stage were compared.It is concluded that the larger the ratio of the dead load of the cable stayed in the transition zone.The larger the proportion of the constant load in the transition zone,the more reasonable the internal force is under the service stage,and the overall stiffness is more reasonable.At the same time,the concept of "stiffness ratio" was also proposed to evaluate the stiffness transition of the cable-stayed suspension bridge.It is concluded that the smaller the stiffness ratio,the smoother the transition of the stiffness.In order to optimize the force of the transition zone,four methods were used including the new load distribution mode,increasing the cable area,increasing the weight and increasing the stiffness of the main girder.The distribution of more dead loads to the cable stays near the cable-stayed section in the transition zone is beneficial to reduce the maximum stress amplitude under moving live load in the service stage,and can also improve the stiffness transition to a certain extent;increasing the area of stay cables or the hangers can reduce the stress amplitude under live load.Hangers and stay cables can be considered as independent systems when the area of stay cables or hangers is modified alone.The effect of reducing the live load stress amplitude is not significant by increasing the weight.The live load stress amplitude of the stay cables and the hangers can be reduced at the same time when the stiffness of the main girder increases.The overall stiffness can also be improved,and the transition of stiffness in the transition zone can be improved.The cable-stayed suspension bridge can tension hangers and stay cables asynchronously to reduce the maximum internal force in the construction process.The selection of different construction schemes has different influence on the force of different components;when the closure position is selected in the midspan,it can be done directly without the rest of the measures.It is necessary to tension temporary hanger when closure position is placed in the transition zone...