What is the bearing capacity of plate rubber bearings for highway bridges
Plate rubber bearings for highway bridges are key load-bearing components between the upper and lower structures of the bridge, and their bearing capacity directly determines the stability and service safety of the bridge. The core performance indicators and influencing factors are as follows:
Plate rubber bearings for highway bridges are key load-bearing components between the upper and lower structures of the bridge, and their bearing capacity directly determines the stability and service safety of the bridge. The core performance indicators and influencing factors are as follows:
1、 Core bearing performance indicators
1. Vertical bearing capacity
The vertical bearing capacity of plate rubber bearings is its core performance parameter. According to the national standard "Plate Rubber Bearings for Highway Bridges" (GB/T 20688), the vertical bearing capacity of bearings ranges from 0.1MN to 10MN, which can meet the needs of bridges with different spans and load levels. Small span slab bridges and pedestrian bridges often use 0.1-1MN bearings, while large-span continuous beam bridges and box girder bridges require 5-10MN high bearing capacity bearings. The bearing principle is to use the elastic deformation of rubber and the rigid constraint of steel plates to evenly transfer the dead and live loads of the upper structure to the pier, while adapting to the small settlement of the bridge through the compression deformation of rubber.
2. Horizontal bearing capacity
Plate type rubber bearings have a certain horizontal bearing capacity and are mainly used to resist horizontal forces during bridge operation, such as braking force, wind force, and frictional force caused by expansion displacement due to temperature changes. Usually, the horizontal bearing capacity of ordinary plate rubber bearings is not less than 10% of the vertical bearing capacity; When the bridge span is large and the horizontal force demand is high, plate rubber bearings with reinforced steel plates can be selected. The reinforced steel plates can significantly improve the horizontal shear resistance of the bearings and avoid shear failure due to excessive horizontal force.
3. Ultimate bearing state
Under extreme load conditions (such as earthquakes and vehicle overloading), the allowable compression deformation of plate rubber bearings is 15% of the total thickness of the bearing. Exceeding this limit will cause the rubber layer to peel off from the steel plate and the bearing to fail. At the same time, the shear ultimate deformation of the support is 70% of the total thickness of the rubber layer of the support, which meets the displacement requirements of the bridge under extreme working conditions such as earthquakes and ensures the safety of the bridge structure.
2、 Key factors affecting carrying capacity
1. Support structure design
The number of layers, thickness, and arrangement density of reinforced steel plates directly affect the bearing capacity of the support. The more layers and thickness of steel plates, the stronger the vertical stiffness of the support and the higher the upper limit of bearing capacity; The thickness of the rubber layer affects the elastic deformation capacity of the bearing. If the rubber layer is too thick, it will reduce the vertical bearing capacity, and if it is too thin, it will limit the deformation adaptability of the bearing. Therefore, it is necessary to design it correctly according to the bridge load.
2. Material properties
The rubber used for the bearings should be chloroprene rubber, natural rubber, or EPDM rubber. Among them, chloroprene rubber is resistant to aging, oil, and chemical corrosion, and is the mainstream choice for highway bridges. Its Shore hardness should reach 55-65 degrees to ensure the elasticity and compressive performance of the rubber; The reinforced steel plate should be made of high-quality carbon steel such as Q235, and after surface rust removal treatment, it should be tightly bonded with rubber to avoid delamination.
3. Construction and installation quality
The flatness and centerline deviation during support installation will directly affect the uniformity of force distribution. If the support is installed at an angle, it will cause local stress concentration, significantly reduce the actual bearing capacity, and even lead to early failure; In addition, anti slip steel plates or mortar cushion layers should be installed on the upper and lower contact surfaces of the support to ensure a smooth transmission path.
3、 Guarantee of bearing capacity in engineering applications
The selection should be based on the calculated span of the bridge, the self weight of the upper structure, the design live load and other parameters, and load verification should be carried out by professional engineers to avoid overloading.
After the installation of the support, regular inspections should be carried out, with a focus on checking the compression deformation, shear deformation, and rubber aging degree. If any abnormalities are found, they should be replaced in a timely manner to ensure stable long-term bearing performance.
For high-intensity earthquake zones and heavy-duty traffic bridges, upgraded products of plate type rubber bearings (such as PTFE sliding plate rubber bearings and pot type rubber bearings) can be selected to further enhance their load-bearing and deformation resistance capabilities.
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