Transportation industry standard "bridge bearings with polymer material skids" Interpretation

The Ministry of Transportation approved the release of the recommended industry standard "polymer material skids for bridge bearings" (JT/T 901-2023) on January 19, 2023, which has been implemented since April 19, 2023.

I. Revision background

With the rapid development of China's economy, high-speed railroads, highway bridge construction also developed rapidly, bearing sliding plate in which plays a vital role. In order to meet the requirements of railroad and highway bridge design, the development of polytetrafluoroethylene slide plate, modified ultra-high molecular weight polyethylene slide plate, modified polytetrafluoroethylene slide plate and SF-1 lateral slide plate. The physical properties of various bearing skids are different and the application conditions are different. In order to regulate the use and detection, corresponding standards have been promulgated, such as European Standard EN1337-2: 2004 "Structural Bearing Part 2; Sliding Elements" and JT/T 901-2014 "Polymer Material Skids for Bridge Bearings" standard, which provides a standard specification for bridge bearing designers to select and detect the control. However, with the development of society, the railroad and highway construction has put forward higher requirements for earthquake prone areas and cross-sea bridges and other harsh environmental conditions to use friction pendulum vibration isolation bearing, friction pendulum vibration isolation bearing design requires the slide plate to operate under silicone grease-free conditions, and the friction coefficient should be controlled within a certain range. For this reason, according to the market demand, we further modified the existing sliding plate material, and developed two kinds of high wear resistance bridge bearing sliding plate material with friction coefficient between 0.03 and 0.05 under the condition of no silicone grease lubrication: ultra-high performance polytetrafluoroethylene sliding plate (UHPF), modified polytetrafluoroethylene sliding plate, these two kinds of sliding plate can meet the design requirements of friction pendulum vibration isolation bearing.

In order to unify and improve the types and technical conditions of the bridge bearing sliding plate, regulate its function, structure, production and inspection, the formation of a consistent and strict, complete and applicable industry standards, the Ministry of Transport organized the relevant units to carry out the industry standard "bridge bearing with polymer material sliding plate" (hereinafter referred to as "the standard") the revision work.

Second, the positioning and role of the standard

The Standard specifies the classification, structure and type of polymer sliding plate for bridge bearing, technical requirements, test methods, inspection rules, marking, packaging, transportation and storage. Applicable to highway bridge plate bearing, basin type bearing, spherical bearing and bridge bearing with vibration isolation function with polymer material sliding plate, other building structure engineering reference use.

The revision of this standard provides a standard basis for the selection and use of bridge bearing sliding plate products under earthquake prone environmental conditions, and plays an important role in the standardization, serialization and industrialization of sliding plate products.

Third, the main content of the standard revision

(A) compared with the 2014 version of the standard "bridge bearing with polymer material sliding plate" (JT/T 901-2014), this standard has mainly done the following aspects of the revision.

Add a new product of ultra-high performance polytetrafluoroethylene sliding plate (UHPF), with the characteristics of resistance to cumulative long-distance displacement and rapid shear movement, so that the design of the bridge bearing more than one optional sliding plate material; according to the demand for the use of the sliding plate is divided into silicone grease lubrication and non-silicone grease lubrication sliding plate, where non-silicone grease lubrication sliding plate is mainly used in the bridge vibration isolation bearing, the standard revision mainly around the bridge vibration isolation Bearing sliding plate (non-silicone grease lubricated sliding plate) related requirements of each chapter, the content of the provisions of the revised.

(B) the main revised content of each chapter

1. added modified polytetrafluoroethylene sliding plate, modified ultra-high molecular weight polyethylene sliding plate, ultra-high performance polytetrafluoroethylene sliding plate (UHPF), copper-based three-layer composite sliding plate

Reason for addition: Add some terms and definitions, corresponding to the classification department of slip sheet materials in the document. For the addition of ultra-high performance polytetrafluoroethylene sliding plate (UHPF) this new material sliding plate, the reason is that the preparation team investigated the specifications, papers and reports on the high level of seismic technology and bearing technology at home and abroad, as well as the combination of the actual bridge project normal use conditions and earthquake conditions under the bearing damage, there are the following main problems.

(1) The traditional slide plate has strong dependence on silicone grease, silicone grease is brought out in the movement of the bearing, the silicone grease is exhausted and difficult to replenish in 3~5 years after operation, the friction coefficient is increasing, accelerating the wear and tear.

(2) The traditional sliding plate material is hard and brittle, not resistant to high temperature, under the rapid motion of the earthquake (V

(3) BS EN15129-2018 Anti-seismic device (seismic isolation device European standard 15129-2018) and AASHTOGSID-2014 Guide Specifications for Seismic Isolation Design (Fourth Edition) ( Seismic Design Specifications - American Association of State Highway and Transportation - 2014) and other specifications are clear that the bearing sliding plate should be able to withstand the seismic dynamic conditions of rapid shear resistance, while having the ability to long distance low wear; domestic "bridge bearing with polymer material sliding plate" (JT/T 901-2014) no sliding plate without silicone grease lubrication in the case of rapid shear performance description.

Ultra-high performance polytetrafluoroethylene sliding plate (UHPF) replaces the traditional material using silicone grease practice, the wear resistance and lubrication performance under the condition of no silicone grease are superior to the wear resistance and lubrication performance under the condition of silicone grease, so the definition of the performance range.

2. Add the "symbol" (see 3.2)

Reason for addition: According to the requirements of GB/T 1.1-2020 "Standardization Guidelines Part 1: Structure and Drafting Rules of Standardization Documents", the symbols applicable to this standard are listed when applicable, so that users can understand the relevant content of the standard more intuitively.

3. Changed the "classification by skateboard use function" (see 4.1.2)

Change the content: the original standard "4.1.2 according to the use of the function of the slide plate is divided into: a) pressure-bearing slide plate (plane and surface), code CY; b) side guide groove with the slide plate, code CD." changed to "according to the use of the slide plate is divided into: a) with silicone grease lubrication slide plate: the surface of the slide plate Set up a storage pit, coated with silicone grease, can be used PTFE, M-PTFE, M-UHMWPE, UHPF four slide plate material; mainly used for bridge plate rubber bearing, basin bearing, ball bearing, etc.. Code RH; b) No silicone grease lubrication slide plate: no grease storage pit on the slide plate surface, no silicone grease coating, M-PTFE, UHPF two slide plate materials can be used; mainly used for bearing with vibration isolation function and building structure engineering bearing. (Code WRH; c) side-oriented slide plate: when used on bridge bearings, no grease storage pit, no silicone grease, can use M-PTFE, M-UHMWPE, UHPF, SF-I four kinds of slide plate materials; mainly used for bearing lateral slip. Codename DX.".

Reason for change: Because this standard revision is mainly added to the non-silicone grease lubricated slide material, and the function is not only pressure-bearing, but also shock-absorbing function, in order to enable the design unit and users to better distinguish and select the slide, it is necessary to describe clearly the state of various types of slide in use, so that users can choose more clearly.

4. Added structure (see 4.2)

Reason for addition: To let designers and users see the structure of different shapes of skateboards more visually, so that it is clearer when choosing to use them.

5. Added "Material" section (see 5.2)

Add content: Add the material requirements of UHPF skid: "UHPF skid should be filled with UHMWPE resin conforming to GB/T 32679 and high strength PTFE fiber conforming to GB/T 38173 and organic material polyether ether ketone conforming to JB/T 12420, the average particle size of UHMWPE resin should not be larger than 160μm, molecular weight should not be less than 9 million, the mixture should be uniform."

Reason for addition: Because UHPF skateboard material is added in the skateboard classification section, it is necessary to describe this skateboard material clearly. 6.

6. changed the "skateboard performance" section (see 5.3)

Changes: Corresponding to 4.1.1 skateboard material classification will be five kinds of material physical performance requirements in a table unified description; Corresponding to 4.1.2 skateboard use function classification will have silicone grease lubrication skateboard, no silicone grease lubrication skateboard, side guide skateboard friction wear performance are described, so that the back and forth, the document paragraph more clearly.

Reason for change: The standard 2014 version of the slide material is mainly for the commonly used basin bearing and spherical bearing. In recent years, friction pendulum vibration isolation bearings and other vibration isolation bearings are widely used on highway bridges, so it is necessary to provide both a certain frictional dissipation energy, and good wear resistance of the slide material for bridge vibration isolation bearings. Therefore, in the revision of the standard, according to the research and development status of polymer material sliding plate for vibration isolation bearing in China in recent years, combined with the relevant foreign standards, supplemented with the sliding plate material for vibration isolation bearing (no silicone grease lubricated sliding plate). According to the European standard EN 15129-2018 vibration isolation device requirements, the slip sheet material used for vibration isolation bearing should meet the following requirements.

(1) Sliding plate material without silicone grease lubrication.

(2) Sliding plate material should have good creep performance, the creep deformation under constant load for 48h is less than 20% of the exposed thickness of the sliding plate.

(3) for the bridge bearing sliding plate material should have good wear resistance, wear distance should be able to meet the sliding distance of not less than 10km requirements.

With reference to the above requirements, the standard for non-silicone grease lubricated sliding plate developed load compression deformation and line wear rate and other related performance indicators and test methods.

No silicone grease lubrication slide plate in the use of vibration isolation bearing, on the one hand, should meet the performance requirements of conventional bearing friction and wear, on the other hand, should meet the role of frictional energy dissipation under the action of the earthquake. Therefore, in addition to the use of conventional bearings in the standard requirements, the performance requirements of the non-seismic action without silicone grease lubricated sliding plate, but also under the action of the earthquake without silicone grease lubricated sliding plate fast dynamic friction coefficient index. The coefficient of dynamic friction of the sliding plate increases with the sliding speed, usually the relative sliding speed of the bearing sliding plate under seismic conditions in 100mm/s - 1000mm/s. According to the experience of foreign sliding speed in 200mm - 250mm/s, the coefficient of dynamic friction of the sliding plate tends to stabilize. Through our determination of the coefficient of dynamic friction of silicone grease lubricated sliding plate in 50mm, 100mm, 150mm, 200mm and 250mm/s speed conditions, the above conclusion is verified. Therefore, it was determined that the average speed of the determination of the coefficient of dynamic friction of silicone grease-free lubricated sliding plate is 200mm/s.

For the format of the arrangement because the standard adds no silicone grease lubrication skateboard, in 4.1.2 in accordance with the use of functional classification into a silicone grease lubrication skateboard, no silicone grease lubrication skateboard and side guide groove skateboard, because there are silicone grease lubrication and no silicone grease lubrication of the two types of physical and mechanical properties of the skateboard index test method is the same, so put in a table description, so that both brief and clear, to avoid repetition, and can explain The two types of sliding plate friction coefficient, line wear rate and load compression deformation performance test conditions are different, so separate description; for non-silicone grease lubricated sliding plate is mainly to play a role in shock absorption, so the non-silicone grease lubricated sliding plate in the earthquake under the action of the dynamic friction coefficient is described separately, so that the hierarchy is clear, easy to understand, can guide the user to better application.

7. Changed the "Test Methods" section (see Chapter 6)

Changes

(1) Increased the test method requirements for materials.

Reason for change: In accordance with the requirements of GB/T 1.1-2020, the technical requirements mentioned in Chapter 5 are required to give the test method requirements in this chapter.

(2) changed the test method requirements for tensile strength, tensile strain at break and tensile modulus of elasticity of sliding plates.

Reason for change: According to GB/T 1040.1 and GB/T 1040.2 test method standards and JT/T 391-2019 "road bridge basin bearing", TB/T 2331-2013 "railroad bridge basin bearing", TB/T 3320-2013 "railroad spherical bearing", GB/T 37358-2019 "building friction pendulum vibration isolation bearing The test methods of tensile strength and tensile strain at break and tensile modulus of elasticity of the sliding plate are modified.

(3) change the test method of slide plate size, clarify the slide plate measurement method and ambient temperature requirements.

Reasons for the change: Because there is no steel ruler with 0.1mm accuracy, it is necessary to change the requirements of measuring tools; increase the requirements of measuring method and ambient temperature, which are more conducive to the quality control of slide plate dimensions.

(4) increased the coefficient of friction and the number of repeated loading correlation test method requirements.

Reason for change: Because the standard text increased this performance of the slide plate, it is necessary to increase the corresponding test method requirements.

8. Changed the "inspection rules" section (see Chapter 7)

(1) change the classification of the slide inspection.

Increased the normal production type inspection requirements "normal production, density, tensile strength, tensile strain at break, ball indentation hardness, tensile modulus of elasticity once a year for third-party inspection; friction coefficient, line wear rate, load compression deformation, interlayer bonding fastness, compression permanent deformation once every two years for third-party inspection";. Increased the "group batch and sampling".

Reason for change: Because the test items and test frequency is different, it is necessary to describe separately, so that the production side and the use of a more intuitive understanding of the type test items and test cycle. For the group and sampling changes are based on industry standards to prepare the requirements, so that users are easier to understand and easier to operate when using the standard.

(2) changed the rules of determination.

Reason for the change: to better guide the production side of the skateboard in the type test and factory inspection of the operation, but also to facilitate the customer's acceptance of the operation. 9.

9. changed the part of "friction coefficient test method of skateboard" (see Appendix A)

(1) Changes: Changed the diagram of the test specimen with silicone grease lubricated slide plate friction coefficient; changed the test method of static and dynamic friction coefficient with silicone grease lubricated slide plate.

Reason for change: According to the requirements of the relevant bearing standards, the friction coefficient specimen should be changed; the description of the test method is more specific, so as to better guide the slide friction coefficient test process and reduce the error of the test results.

(2) increased content: increased the friction coefficient test conditions with silicone grease lubricated slide UHPF; increased the static and dynamic friction coefficient and the number of repeated loading correlation test method and test conditions and calculation method requirements without silicone grease lubricated slide.

Reason for increase: Because the standard increased the UHPF slide material, so it is necessary to the new slide material friction coefficient test conditions; standard also added two new silicone grease lubricated slide material, no silicone grease lubricated slide working principle is mainly through the different friction coefficient and achieve the function of vibration isolation, so it is necessary to no silicone grease lubricated slide friction coefficient test method and test process Therefore, it is necessary to describe the friction coefficient test method and test process of silicone grease lubricated skids in detail, so as to obtain more accurate test results and better guide the design unit and the user to verify the friction coefficient index of silicone grease lubricated skids.

10. Changed the "test method for skateboard line wear rate" section (see Appendix B)

(1) add content: the test conditions of the line wear rate of UHPF with silicone grease lubrication skateboard and the test conditions of the line wear rate of skateboard without silicone grease lubrication have been added.

Reason for addition: The standard adds UHPF silicone grease lubricated skids and two kinds of non-silicone grease lubricated skids, so it is necessary to add the UHPF silicone grease lubricated skids and non-silicone grease lubricated skids line wear rate performance index test process description, in order to guide the test process to ensure the accuracy of the test results.

(2) Changes: The formula for calculating the line wear rate is changed from "after wear - before wear" to "before wear - after wear".

Reason for change: Through consultation with relevant experts and inspection agency professionals, it was confirmed that the provisions of the original standard is wrong, so it is necessary to change it. 11.

11. Changed the part of "test method for load compression deformation of skids" (see Appendix C)

Addition: The test conditions for load compression deformation of UHPF with silicone grease lubricated skids and the test conditions for load compression deformation of two types of skids without silicone grease lubrication have been added.

Reason for addition: Since the standard adds two kinds of sliding plates with and without silicone grease lubrication, it is necessary to describe the test process of load compression deformation performance index of the new UHPF sliding plates with and without silicone grease lubrication in order to guide the test process and ensure the accuracy of the test results.

12. changed the "copper-based three-layer composite skids interlayer bonding fastness and compression permanent deformation test method" section (see Appendix D)

(1) change the SF-I slide test size, from the original "interlaminar bonding fastness specimen size of 120mm × 120mm × 2.5mm, compression deformation specimen size of 15mm × 15mm × 2.5mm." changed to "interlaminar bonding fastness specimen size should be 120mm × 20mm × 2.4mm, compression permanent deformation specimen size of 15mm × 15mm × 2.4mm." The SF-I slide plate compression permanent deformation test device schematic was added.

Change, increase the reason: Because the total thickness of the SF-I slide plate is required in clause 5.4.1.2 of this standard, the specimen should be selected in accordance with the size requirements of the slide plate. The addition of SF-I skid plate compression permanent deformation test device schematic diagram allows a more intuitive understanding of the method and process of the skid plate compression permanent deformation test.

(2) The test method of initial static friction coefficient of copper-based three-layer composite skateboard is added.

Reason for addition: Because the initial static friction coefficient of the product has been added to the performance requirements in this standard, it is necessary to increase its test method requirements.

Draft compiler: Shenzhou City Engineering Plastics Co.

Draft Review: National Traffic Engineering Facilities (Highway) Standardization Technical Committee Zhao Jun