Leaning Arch Bridge Design Study Of A Number Of Issues

Along with the fast development of bridge industry, people's request to bridge is not merely to satisfy the need of transportation, the request of landscape to bridge is also more and more high. Double X-arch bridge is a beauty with novel structure, the model is distinct and it has a line of beauty, so it is usually to be the best scheme of the landscape bridge in our country. Because of the structure is complicated, the space effect is obvious, the quantity of this new type arched bridge constructed is little and the research outcome about the double X-arch bridge has only a few in our country and overseas, which limited the development of this new kind of bridge. Therefore, making research on the design parameter of the double X-arch bridge has important theories meaning and practical value.This text according to the structure characteristics of the double X-arch bridge, use the FEM to construct the bridge's spatial finite element model, use the space beam unit to simulate the longitudinal collar beams, end floor beams, middle floor beams and the arch ribs. etc. use the plate element to simulate the bridge deck and the truss element to simulate the suspenders, with all of which to build up the bridge's spatial mechanical computational finite element model. Suspenders' initial force is calculated by influence matrix method and optimized, using the optimized calculating result as the initial tension to input the bridge's calculation model, which can make the suspenders' tension and the design value fit together well. By using the finite element model of the bridge to investigate the suitable sloping angle of arch rib and the pulling form of the outer suspenders of the double X-arch bridge, and defined the dimension of suitable sloping angle of the arch ribs and suitable pulling form of the outer suspenders. On this foundation, this text investigated the effect on the static property, the dynamic property and the stable property of the double X-arch bridge, which is generated by the change of the arch rib's sloping angle. The main work and results of this text are as follows:1. In this text, by using the influence matrix method to calculate and optimize the initial tension of the boom, using the optimized calculating result as the initial tension to input the bridge's calculation model can make the suspenders' tension and the design value fit together well, which can provide the initial balance of the bridge.2. The suitable sloping angle between the main arch rib and the stable arch rib as well as the suitable pulling form of the outer boom are the important factors that influences the double X-arch bridge designing quality. The suitable sloping angle between the main arch rib and the stable arch rib and the suitable pulling form of the outer boom are investigated in this text, according to the calculating result, the domain of suitable sloping angle of the arch rib is defined: the sloping angle of the main arch rib is sloping outside from 0°～1.5°, and when it reaches 1°is the best; the sloping angle of the stable arch rib is sloping inside from 8°～12°, and when it reaches 10°is the best. According to the calculating result, when the outer boom and the outer arch rib are not in the same plane along with increasing the pulling angle of the outer boom can reduce the lateral displacement effectively, which can provide a better balanced and stabilized state.3. The effect on the static property of the double X-arch bridge caused by the change of the arch ribs' sloping angle(1) The effect on the static property of the double X-arch bridge caused by the change of the main arch rib's sloping angle. The augmentation of the main arch rib's sloping angle has little effect on the shear, the moment of torsion and the moment of flexion of double X-arch bridge, but it has significant effect on the axial force of the bridge. Among them, the axial force of the collar beam and the axial force of the outer arch rib increase with the augmentation of the main arch rib's sloping angle, the axial force of the inner arch rib decreases obviously with the augmentation of the main arch rib's sloping angle. The change of the sloping angle of the main arch rib has little effect on the bridge's displacement, which can prove that adjusting the sloping angle of the main arch rib is not the effective measure to control the displacement of the bridge.(2) The effect on the static property of the double X-arch bridge caused by the change of the stable arch rib's sloping angle. The change of the stable arch rib's sloping angle has great effect on the inner force of the double X-arch bridge. The axial force and the shear-Z of the collar beam decrease with the augmentation of the stable arch rib's sloping angle, but the moment of flexion-Y and the moment of torsion increase with it obviously. The change of the stable arch rib's sloping angle has little effect on the inner force of the main arch rib, but it has great effect on the lateral shear (shear-Y), the lateral shear increases with the augmentation of the stable arch rib's sloping angle. The axial force and the lateral shear (shear-Y) of the outer arch rib increase greatly with the augmentation of the stable arch rib's sloping angle. The change of the stable arch rib's sloping angle has great effect on the lateral displacement of the double X-arch bridge. Adjusting the sloping angle of the stable arch rib can control the bridge's lateral displacement well, which can provide a better balanced state of the bridge.4. The effect on the dynamic property of the double X-arch bridge caused by the change of the arch ribs' sloping angle(1) The effect on the autooscillated property of the double X-arch bridge caused by the change of the main arch rib's sloping angle. The change of main arch rib's sloping angle has great effect on the autooscillated frequency of the double X-arch bridge. The first 5 order autooscillated frequency increase with the augmentation of the main arch rib's sloping angle, especially the first two order autooscillated frequency increase obviously, the bridge's autooscillated frequency which after the 6th order increases with the augmentation of the main arch rib's sloping angle first, but when the arch rib's sloping angle surpass 1°, the bridge's autooscillated frequency will decrease on the contrary.(2) The effect on the autooscillated property of the double X-arch bridge caused by the change of the stable arch rib's sloping angle. The change of the stable arch rib's sloping angle has great effect on the first and the second order autooscillated frequency, the first two order autooscillated frequency increase obviously with the augmentation of the stable arch rib's sloping angle. The change of the stable arch rib's sloping angle has little effect on the autooscillated frequency of the 3^rd order to the 10^th order.5. The effect on the stable property of the double X-arch bridge caused by the change of the arch ribs' sloping angle(1) The effect on the stable property of the double X-arch bridge caused by the change of the main arch rib's sloping angle. The change of main arch rib's sloping angle has great effect on the stability factor of the first and the second order of the double X-arch bridge. The stability factor of the bridge's first two order is improved obviously by the augmentation of the main arch rib's sloping angle. The augmentation of the main arch rib's sloping angle is benefit to improving the low order stability property of the double X-arch bridge, but it is not benefit to improving the high order stability property of the bridge.(2) The effect on the stable property of the double X-arch bridge caused by the change of the stable arch rib's sloping angle. The change of the stable arch rib's sloping angle has great effect on the stable property of the double X-arch bridge. The stability factors of the bridge's first order to the eighth order decrease with the augmentation of the stable arch rib's sloping angle. Since the increasing of the sloping angle of the stable arch rib, the stable arch rib will produce bigger lateral thrust to the main arch rib, which will change the buckling modal of the bridge. The results can prove that the augmentation of the stable arch rib's sloping angle is not benefit to improving the stable property of the double X-arch bridge. When designing, the stable arch rib's sloping angle of the double X-arch bridge is unsuitable to be too big and from 8°to 10°is the best.