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 spanning structure to the pier, and to withstand deformation of the end of the bridge span structure such as horizontal displacement and rotation angle; 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 spanning structure to rotate freely and cannot move; the latter not only enable 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 not only widely used in small and medium-span road bridges, urban bridges, and railway bridges, but also in large spans. Bridges are also used extensively. Currently widely used in the bridge project is the common plate, PTFE plate and cassette rubber bearings 3 types. 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 compounded with the compounding agent and compounded by a compounding agent after being plasticized. After being parked, recycled, and rolled out, the film is cut into semi-finished products with certain specifications. The semi-finished product is pressurized and vulcanized on a plate vulcanizing machine after being loaded. The vulcanization process should pay attention to avoid the uneven thickness and the movement of the steel plate.
In bridge rubber bearings, the lead rubber bearing is made by vertically filling the middle of a common shock absorbing and damping rubber bearing. The purpose of filling lead is to improve the energy absorption efficiency 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 the shock absorber and damper and can be used independently in a seismic isolation system.