Bridges play an important role in the entire transportation network, and bridge bearings play a great role in the safety and stability of bridges. In order to better meet the development needs of highway and railway bridge technology in China, the types of bridge bearings are constantly updated and increased.
The role of bridge bearings
The reason why the bridge bearing is so important in the overall operation process of the bridge is that it connects the bridge superstructure and the substructure, and it is precisely because of this that the bridge bearing needs to assume a certain functional role.
First of all, the bearing must have sufficient bearing capacity to support the vertical loads such as dead loads and live loads transmitted from the bridge superstructure, as well as the lateral loads formed by **, wind, etc., and transfer these loads to the bridge substructure safely and effectively.
Secondly, because the environmental conditions where the bridge is located are in continuous change, and will have a certain influence on the bridge, therefore the bridge bearing should also be able to adapt to the fulcrum angle change that the horizontal displacement and deflection of the superstructure produces, ensure that the structure can be deformed by the factors such as live load, temperature change, concrete shrinkage and creep, so that the actual situation of the upper and lower structure of the bridge conforms to the static schema of the structure.
In addition, in order to improve the seismic performance of the entire bridge when it occurs, the bridge bearing should also have certain seismic absorption and isolation performance, that is, under the action of ** and wind, it has the effect of adapting to instantaneous large displacement. Of course, due to the complexity of the forces acting on the bridge structure, the bridge bearing should also play other roles to meet the normal operation needs of the bridge.
Bearing performance test
The necessity of testingThe bearing plays an important role in the operation of the bridge, but it is also one of the common parts of the bridge disease, especially the bridge is subjected to the reciprocating load of passing vehicles in the operation process, and the physical parameters of the bridge structure itself are also non-determined and uneven, so it is very easy to cause disease and damage of the bridge bearing. The relevant performance testing of the bridge bearing can effectively control the quality of the bearing, and ensure that the bridge will maximize its role to a certain extent, so as to bring promotion to the entire transportation system.
The relevant standards and specifications also put forward clear requirements for the specific performance indicators related to bridge bearings, such as "Rubber Bearings Part 4: Ordinary Rubber Bearings" (GB T 20688.).4-2023), it is required that under the design load, the average compressive deformation of the bearing is not more than 7% of the total thickness of the rubber layer; According to the total height of the bearing, the specific requirements for the vertical compression deformation of the support are given. Regarding the turning angle in the basin bearing of highway bridges (JT T391-2019), the rotation angle of the vertical design of the bearing is required to be not less than 002rad。Through the quality inspection of the bearing, it can also be seen whether the bearing meets the corresponding technical requirements, and provides technical data for later operation and maintenance.
Detect contentDue to the different types of bridge bearings, the specific components and structural forms are different, and the appropriate items should be selected according to the product characteristics and actual needs when testing their performance.
For the detection of bridge bearing performance, the first is the performance test of the finished bearing product, including mechanical properties, durability performance, planing performance and other specific aspects, the main test items are ultimate compressive strength, compressive elastic modulus, shear elastic modulus vertical compressive stiffness, horizontal equivalent stiffness, compressive deformation, shear elastic modulus after aging, allowable shear angle tangent, allowable angle tangent, design corner, friction coefficient between sliding plate and stainless steel plate, design compressive stress, design tensile stress, Equivalent damping ratios and shear strain related items, etc.
In addition to the detection of the finished product of the bearing, the material used in the bearing also directly affects the performance and quality of the bearing, therefore, the performance testing of the materials used in the bearing is an important part of the bridge bearing detection. The specific detection of which materials are closely related to the type of bridge bearing, basin bearing material testing includes steel, rubber, bearing slide plate, 5201-2 silicone grease, copper sealing ring, guide slide plate, anchor bolt material, etc., spherical bearing material testing includes PTFE plate, silicone grease lubricant, hard chrome plating layer, stainless steel plate, steel, steel casting, etc., and plate bearing material performance testing includes rubber, slide plate, steel plate and anchor bolt components.
Conclusion
The performance testing of bridge bearings is an important guarantee to ensure that the bridge bearings play their role normally, and the corresponding testing items should be selected according to the specific types of bridge bearings in the actual testing. In addition, the installation quality of the bearing is also directly related to the working performance of the bearing, and the quality control of its installation construction and materials cannot be ignored.