Where is the rotational performance of spherical bearings for railway rail transit bridges reflected
The rotational performance of spherical bearings on railway rail transit bridges is one of their core functions, mainly reflected in three aspects: flexibility in adapting to bridge structural deformation, controllability of rotation angle, and stability under bearing state. The specific manifestations are as follows:
The rotational performance of spherical bearings on railway rail transit bridges is one of their core functions, mainly reflected in three aspects: flexibility in adapting to bridge structural deformation, controllability of rotation angle, and stability under bearing state. The specific manifestations are as follows:
1. Adapt to the vertical angular deformation of bridges
Under the action of dead load (self weight, bridge deck pavement) and live load (trains, pedestrians), the two ends of the bridge will produce vertical angles (such as the angle at the end of a simply supported beam and the angle at the support of a continuous beam). The core structure of a spherical bearing is a sliding pair of spherical PTFE plate and spherical stainless steel plate. The design of spherical contact allows the bearing to rotate freely in any direction, and the center of rotation coincides with the bending center of the beam, effectively releasing the angular deformation caused by bending of the beam and avoiding the bearing from being "lifted" or generating additional stress by the beam.
2. Meet the horizontal displacement and rotation requirements of the bridge
Railway bridges may experience horizontal displacement due to factors such as temperature changes, concrete shrinkage and creep, and train braking. The rotational performance of spherical bearings can work in conjunction with the horizontal displacement function: while the beam slides horizontally, the bearings can synchronously complete small vertical or horizontal angle rotations without interfering with each other. For example, when the temperature rises in a large-span continuous beam bridge, the beam body elongates and accompanied by the rotation angle at the support. The spherical support can simultaneously meet the composite deformation requirements of "sliding+rotation", ensuring the uniform stress distribution of the bridge structure.
3. Design adaptability and controllability of rotation angle
The rotational performance of the bearings needs to match the turning angle requirements of different bridge types. The design will specify the rated turning angle (usually the vertical turning angle of railway bearings can reach 0.02-0.05 rad, or 1.15 ° -2.86 °), and the bearing capacity remains stable during the turning process - even if the design turning angle is reached, the spherical contact pair of the bearings will not experience stress concentration and can continuously withstand the vertical load of the bridge (including dead load, live load, and train impact load). In addition, the rotational friction coefficient of the support is relatively low (the friction coefficient of the PTFE plate is ≤ 0.03), resulting in low resistance during rotation and no additional constraint bending moment on the beam.
4. Dual directional rotation capability suitable for complex stress conditions
Unlike unidirectional hinge bearings, railway ball bearings have bidirectional rotational performance and can simultaneously adapt to longitudinal and transverse angular deformations of the beam. This characteristic is particularly suitable for complex bridge types such as curved bridges, cable-stayed bridges, and continuous rigid frame bridges. For example, the beam body of a curved railway bridge not only has longitudinal angles, but also angles generated by lateral torsion. The spherical structure of spherical bearings can withstand such composite angles, avoiding local pressure damage to the bearings.
5. Rotational energy dissipation and reset performance under earthquake conditions
The rotational performance of seismic resistant railway ball bearings also has the function of energy dissipation and seismic reduction. When an earthquake occurs, the beam undergoes severe rotation and displacement, and the spherical sliding pair of the support can dissipate some seismic energy through friction during the rotation process; After the earthquake, the spherical self resetting characteristic of the support can drive the beam to recover to its initial position, reduce residual deformation of the beam, and improve the seismic safety of the bridge.
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