Design and Type Selection of Laminated Rubber Bearings for Highway Bridges
The rubber bearing is made of multi-layer rubber plates embedded, bonded, and pressed with thin steel sheets, and the bearing capacity can reach 10000kN. It has the advantages of simple structure, easy manufacture, less steel consumption, low cost and convenient installation. Rubber bearings are suitable for road, city and railway bridges with small and medium spans. According to my country’s highway bridge code, the beam bridge with a standard span of 20m can generally use laminated rubber bearings. The reaction force applicable to rubber bearings is generally reasonable below 2000KN.
Round rubber bearings are the same as rectangular rubber bearings, but have a different shape. This bearing is round. The circular rubber bearing is vulcanized by several layers of rubber sheets and thin steel sheets. With good elasticity and rigidity, it can meet the horizontal displacement of the upper structure. The circular rubber bearing has the advantages of excellent workmanship, simple structure, low price and easy replacement.
Install the circular rubber bearing first, and ensure that the design of the supporting pad is accurate, and the longitudinal axis of the plate girder box girder is parallel to the center of the bearing. As the beam is erected and lowered, it should be smooth to prevent deflection or initial shear deformation.
The circular rubber bearing is suitable for curved bridges, inclined bridges, and cylindrical pier bridges. There are two types of circular rubber bearings, ordinary laminated rubber bearings and PTFE sliding rubber bearings. Both are shock-absorbing products commonly used in road bridges, and the latter has an extra layer of PTFE slide plate than the former. Ordinary rubber bearings are suitable for short-span highway bridges, while PTFE sliding rubber bearings are suitable for long-span highway bridges.
Ordinary laminated rubber bearings for cast-in-place beam bridges are easy to install. Keep the pier pad stone top surface clean. If the height difference of the supporting pad is too large, it can be adjusted with cement mortar. Mark the center of the support pad stones according to the design drawing. When installing, the center of the rubber bearing should be consistent with the center line of the support pad stone to ensure the accurate positioning of the support. When the same beam needs two or four supports, in order to facilitate leveling, a layer of cement mortar can be laid between the support pad stone and the support, so that the support will automatically level under the pressure of the bridge body. Before pouring the beam body, place a supporting steel plate slightly larger than the plane of the support on the bracket, weld the anchor bars on the steel plate to connect with the beam body, and pour the supporting steel plate as a part of the pouring beam formwork. According to the above method, the bearing can be tightly attached to the steel plates on the bottom of the beam and the top surface of the pad stone.
The key to the installation of the prefabricated beam rubber bearing is to ensure that the bottom of the beam and the top surface of the pad stone are parallel and flat, so that they fit closely with the upper and lower surfaces of the bearing, and there should be no deviation, deviation, and uneven bearing capacity. Firstly, the supporting pad stones are processed to make the supporting pad stones have the same elevation. The bottom surface of the prefabricated beam in contact with the support should be flat. When there is honeycomb slurry and inclination, it should be compacted and leveled with cement mortar in advance.