Determination On The Rational Status And Study On The Overall Stability Of Long-span Hybrid Girder Cable-stayed Bridge

With its unique advantages, hybrid girder cable-stayed bridge has become one of the main directions of long-span cable-stayed bridge. As the span increases, for to ensure the security during the process of the bridge construction and to meet the design requirements of the internal force and linear of bridge structure after its completion, it is worthwhile to research the determination on the reasonable status and study on its overall stability of the hybrid girder cable-stayed bridge.The determination on the reasonable state of the long-span hybrid cable-stayed bridge can be divided into two main parts: the determination of the reasonable finished state and the determination of the reasonable construction state. The paper bases on the engineering background of Jiujiang Yangtze River Bridge and the calculation software of the plane frame finite element program FBR_CAL_SUO and SUS_CAL_SUO, uses the synthesis method of dead load balance method,the stress balance method and the least squares method. This synthesis method calculates the influence of dead load, live load, prestressing force, weight load and other factors by aiming to restrict the maxim and minimum stress of the main beam under the normal load and by means of adjusting the cable tensile forces, and uses the optimized method of forward analysis to determine the reasonable finished state. It shows that this method is accurate and reliable by comparing the result with the design result. After the determination of the reasonable finished state, we adopt the "two-step in place based on forward analysis method" to determine the reasonable construction state of the long-span hybrid cable-stayed bridge, to ensure the stress security of structure during the process of construction and the reasonable finished status during the finished phase. The calculated results show that the "two-step method in place" method is effective and simple, and it also provides theoretical foundation for construction.One of the main problems that long-span bridges should consider is the stability. While because of its large-span and asymmetry, the stability problem of the long-span hybrid cable-stayed bridge is especially evident. Thus, it is necessary to research the stability of the long-span hybrid cable-stayed bridge. This paper first expounds the stability question of the first and second of the cable-stayed bridge and introduced the evaluation indicators of the stability. Then it give an analysis of linear, nonlinear and geometric nonlinear on its operating conditions during the phase of the construction and operation by using the large universal software ANSYS. The calculation result shows that the stability factors of the Jiujiang Yangtze River Bridge meet the standard on both of the construction and operation phases.