Plate rubber bearings are a bridge bearing product that is inlaid, bonded and vulcanized with multiple layers of natural rubber and at least two layers of thin steel plates of the same thickness.
This type of rubber bearing has sufficient vertical stiffness to withstand vertical loads and can reliably transmit the pressure of the superstructure to the pier; it has good elasticity to adapt to the rotation of the beam end; It has large shear deformation to meet the horizontal displacement of the superstructure;
Plate bearings are divided into two types: rectangular and circular.
According to whether it can provide horizontal displacement, it is divided into: polytetrafluoroethylene skateboard bearings and ordinary rubber bearings.
Rectangular (circular) plate
(1) Performance: This product is inlaid with multiple layers of rubber sheets and thin steel plates, bonded under a certain pressure, a certain temperature and a certain time Vulcanized and pressed. It has sufficient vertical stiffness to bear vertical loads, can reliably transmit the reaction force of the upper structure of the beam plate to the pier, has good elasticity to adapt to the rotation of the beam end, and has large shear deformation to satisfy the upper structure. Horizontal displacement of beam structure.
(2) Features: This product has been widely used in bridge construction, hydropower projects, and house earthquake-resistant facilities. Compared with the original steel bearings, it has a simple structure and is easy to install; it saves steel and has a low price. It has the advantages of low cost, simple maintenance and easy replacement, and its low building height is beneficial to bridge design and cost reduction. It has good seismic isolation effect and can reduce the impact of live load and seismic force on buildings.
PTFE skateboard type
Referred to as PTFE skateboard bridge bearing, this product is a layer of polytetrafluoroethylene with a thickness of 2-3mm bonded to an ordinary plate rubber bearing. Made of fluoroethylene board. In addition to having the vertical stiffness and elastic deformation of ordinary plate rubber bearings, and being able to withstand vertical loads and adapt to beam end rotation, the bridge superstructure can be made more flexible due to the low friction coefficient (μ≤0.03) between PTFE and the stainless steel plate at the bottom of the beam. The horizontal displacement is not limited. Large-span bridges with spans >30 meters, simply supported beam continuous plate bridges and multi-span continuous beam bridges can be used as movable supports; continuous beam push, T-beam lateral movement and large equipment slippage Can be used as a slider. a: Neoprene: Applicable temperature +60℃∽-25℃
b: Natural rubber: Applicable temperature +60℃∽-40℃ 1) Selection
a: View plate type The installation and construction drawings of rubber bearings mainly pay attention to the main technical parameters such as specifications, thickness, and design bearing capacity of plate rubber bearings. For PTFE skateboard rubber bearings, you should also pay attention to the size, installation position and direction of the embedded steel plate;
b: When selecting plate rubber bearings, the maximum bearing capacity of the bearing should be consistent with the reaction force of the bridge fulcrum. , the allowable deviation range should be ±10%;
c: For curved, sloped, inclined and wide bridges, circular plate rubber bearings should be used. Highway bridge projects should not use rubber bearings with spherical crowns or slopes;
d: When the longitudinal slope of the bridge is not greater than 1%, plate rubber bearings can be directly installed on the piers, but they should The thickness required to take into account the effect of longitudinal slope. When the longitudinal slope is greater than 1%, embedded steel plates (with wedge-shaped steel plates), concrete pads (padded stones with slopes) or other measures should be used to level the bottom of the beam to ensure that the supports are flat. The plate rubber bearing should be checked according to the relevant provisions of JTG D62 and can be used only after the calculation meets the specified requirements.
e: GJZF4 and GYZF4 type PTFE slide rubber supports should be installed horizontally. Upper and lower steel plates should be installed, and 5201-2 silicone grease should be applied between the PTFE slide plate and the stainless steel plate. A dust cover must be installed after installation; the PTFE slide plate of the support must not be placed on the bottom of the support, unlike the PTFE slide plate. The contacting stainless steel plates cannot be placed directly on bridge piers or pad stones.
2) Installation
a: Installation preparation
a.1 The installation place of the plate rubber bearing should be equipped with supporting pads, and the plane size of the supporting pads should be According to the local pressure calculation, the length and width of the pad should be at least 50mm greater than the corresponding dimensions of the support, and its height should be more than 100mm, and the convenience of replacement of the support should be considered.
a.2 A steel mesh should be arranged inside the bearing padding. When the diameter of the steel bars is 8mm, the spacing should be 50mm×50mm. There should be vertical steel bars in the bridge piers and platforms extending into the bearing padding. The concrete strength grade of the cushion stone should not be lower than C50.
a.3 The surface of the bearing pad should be smooth, clean, dry and free of floating sand.
The elevation of the top surface of the bearing pad must be accurate. In the case of flat slope, the supporting pads at both ends of the same beam and the supporting pads on the same pier and platform should be in the same design elevation plane, and their relative height difference should not exceed ±1.5 mm. The height difference of the same supporting pads should be less than 0.5 mm.
b: Bearing installation
b.1 After the bearing arrives at the site, check whether there is a manufacturer's trademark or permanent mark on the bearing. During installation, the centerline of the support position should be marked on the support pads and supports in accordance with the design drawings to ensure that the supports are accurately in place.
b.2 When the bearing is installed, the bearing should be prevented from bias or excessive initial shear deformation. After the installation is completed, it must be ensured that the support is in close contact with the upper and lower structures, and no hollowing occurs. For beam-slab structures that do not form an integral structure, heavy vehicles should be prevented from passing through.
b. 3 The design of bridge piers and abutments should consider the need for support maintenance and replacement. Under any circumstances, two or more supports are not allowed to be installed side by side at the same support point along the longitudinal centerline of the beam; on the same beam (slab), it is not appropriate to install more than two supports laterally; supports of different specifications are not allowed to be installed side by side at the same support point. Bases should not be installed side by side.
b. 4 After the bearing is installed, a comprehensive check should be made to see if there is any leakage of the bearing, the installation direction and position of the bearing (contact with the embedded steel plate, the position of the center line of the bearing), and the specifications and models of the bearing. Whether there are errors, whether temporary fixed facilities have been removed, whether silicone oil has been injected into the PTFE skateboard support (it is strictly prohibited to use lubricating oil instead of silicone oil), etc. Once discovered, they should be adjusted and dealt with in time to ensure the normal operation of the support after installation, and Record various deviations and abnormalities that occur after the bearing is installed.
b.5 The average compressive stress σc=10MPa during the use stage of the bearing. The volume of the rubber elastomer of the bearing is Eb=2000MPa.
When the bearing is in contact with concrete, the friction coefficient μ=0.3; when it is in contact with the steel plate, the friction coefficient μ=0.2; when the polytetrafluoroethylene plate is in contact with the stainless steel plate (when silicone grease is added) the friction coefficient μ is less than Equal to 0.03, when the temperature is lower than -25°C, the μf value increases by 30%. When the skateboard support must be installed, silicone grease is added to the surface of the PTFE plate.
b.6 When installing the rectangular supports, place them in the direction of the bridge with the short side dimension.
3. Maintenance
1) Plate rubber bearings should be maintained and repaired regularly. Once problems are found, they should be repaired or replaced in time.
2) Plate rubber bearings and PTFE slide rubber bearings should be inspected as follows:
a: Whether the bearings are slipping or hollowing;
b: Whether the shear displacement of the bearing is too large (the shear angle should not be greater than 35°);
c: Whether the bearing has excessive compression deformation; (the maximum compression deformation must not be More than 0.07te, te is the total thickness of the rubber layer of the bearing)
d: Whether the rubber protective layer of the bearing has cracking, hardening and other aging phenomena, and record the crack location, cracking width and length;
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e: Whether the protrusions of the rubber plates between the stiffened steel plates on each layer of the support are uniform and normal;
f: For the PTFE slide rubber support, the polyethylene layer on the top of the support should be checked. Check whether the PTFE slide plate is intact, whether there is any peeling phenomenon, whether the support has slipped out of the stainless steel plate on the top surface of the support, and whether 5201-2 silicone grease has been applied and filled into the oil storage pit of the rubber support of the PTFE slide plate.
3) All parts of the support should be kept intact and clean. Remove garbage and debris around the support in time, and remove snow and ice in winter to ensure the normal operation of the support. At the same time, sewage should be cleaned frequently to remove accumulated water on piers and platform caps. Rubber bearings should be prevented from contacting grease. Residual engine oil on the bottom of beams and piers and platform caps should be cleaned. Prevent rubber from aging and deteriorating from losing its function.
2.4.4 If the pressure on the beam fulcrum is uneven and the support appears hollow or has excessive compression deformation, it should be adjusted.
2.4.5 Plate rubber bearings should be replaced in time when excessive shear deformation, aging, cracking, etc. occur. ,
2.4.6 For the rubber support of the PTFE slide plate, if sediment is found to enter the contact surface between the PTFE slide plate and the stainless steel plate or the silicone grease dries up, clean it in time and inject new silicone grease.