In the bridge project, bearings need to be set at both ends of the beam bridge span. The main function of the bearing is to reliably transmit all loads ( including dead load and live load ) on the span structure to the bridge piers, and to withstand deformations of the horizontal deflection and corners of the bridge span structure caused by the load. The second is to adapt to the shrinkage caused by changes in temperature and humidity. There are two kinds of fixed and movable bearings for bridge bearings. The former is the position of the fixed span structure on the pier, which allows the ends of the span structure to rotate freely but cannot move; the latter not only enables the free rotation of the end fulcrum but also requires It can move freely and withstand the expansion and contraction caused by temperature change, concrete shrinkage and load and other factors of bridge span structure.
The use of rubber bearings began in the late 1950s in the foreign countries and was applied in many countries around the world in the 1960s. Compared with other rigid bearings, bridge rubber bearings not only have reliable working performance, but also have the advantages of simple structure, adequate material source, and easy processing and manufacturing.
Because rubber bearings can adapt to the deformation of the superstructures of wide bridges, curved bridges, and skew bridges in all directions, they are currently widely used not only in small and medium-span road bridges, urban bridges, and railway bridges, but also in large spans. Currently there are 3 types widely used in the bridge project including the common plate, PTFE plate and cassette rubber bearings. The principle of selecting rubber main materials for bridge rubber bearings is to meet the requirements of engineering performance. In combination with the requirements of environmental conditions, NR, CR, EPDM, IIR, and chlorinated IIR are basically selected. The rubber bearing manufacturing process of bridges is often molded. In the production process, the rubber is plasticized and compounded into a compounding gel according to the formula. After being parked, recycled, and rolled out, the semi-finished film is cut into certain specifications. The semi-finished product is pressurized and vulcanized on a plate vulcanizing machine after being loaded. It should be paid attention to avoid the uneven thickness and the movement of the steel plate in the process of vulcanization.
In bridge rubber bearings
, the lead rubber bearing is made by vertically filling the middle of a common shock absorbing damping rubber bearing. The purpose of filling lead is first to improve the energy absorption effect of the bearing and ensure that the bearing is moderately damped; the second is to increase the early stiffness of the bearing, which is beneficial for controlling the wind reaction and resisting the slight vibration of the foundation.
The seismic isolation system composed of such rubber bearings is a leading product and has been widely used in large and medium-sized bridges abroad, and has achieved good results. High damping rubber bearings are made of high damping rubber material. High damping rubber can be obtained by incorporating graphite in NR or synthetic rubber, and the damping characteristics of the material can be adjusted according to the amount of graphite incorporated. As with lead-damping and damping rubber bearings, the high-damping and shock-absorbing rubber bearing also has the functions of shock isolator and damper, and can be used independently in a seismic isolation system.