Neoprene Bearing Pad Specification

Neoprene Bearing Pad Specification

I. Material Properties

1、Main Material

1. Made of neoprene (polychloroprene), complying with standards such as ASTM D2000 or GB/T 20028.
2. Rubber hardness: Typically Shore A 50±5 to 70±5, adjustable based on load requirements.
3. Physical properties:
   1. Tensile strength: ≥10 MPa (at room temperature)
   2. Elongation at break: ≥300%
   3. Aging resistance: After aging at 70℃ for 168h, tensile strength change rate ≤-20%, elongation change rate ≤-30%.
   4. Weather resistance: Resistant to ozone (50pphm, 40℃×72h) without cracking, suitable for long-term outdoor use.

2、Reinforcement Material (Optional)

1. Natural rubber or synthetic fiber fabrics (e.g., nylon, polyester) interlayers can be embedded to enhance compressive stiffness and load-bearing capacity, with common layers ranging from 1 to 5.

II. Structural and Dimensional Specifications

1、Shape Classification

1. Rectangular bearing pads:
   1. Common size range: Length L=100-1000mm, Width B=100-800mm, Thickness H=10-100mm.
   2. Examples: 150mm×200mm×20mm, 200mm×300mm×30mm.
2. Circular bearing pads:
   1. Diameter Φ=100-600mm, Thickness H=10-80mm.
   2. Examples: Φ200mm×25mm, Φ300mm×40mm.
3. Special-shaped bearing pads: Customizable for trapezoidal, arc-shaped, or other special shapes, suitable for complex structural interfaces.

2、Tolerance Requirements

1. Length/width: ±2% (when size ≤500mm), ±1% (when size >500mm).
2. Thickness: ±1mm (when thickness ≤20mm), ±2% (when thickness >20mm).

III. Mechanical Performance Indicators

1、Compressive Performance

1. Design compressive strength: Typically 8-15 MPa, ultimate compressive strength ≥25 MPa.
2. Compressive elastic modulus (Ec): Ranges from 3-10 MPa depending on hardness and layers, calculated by the formula:Ec​=1+2n/kEr​(1+2n)​

   (where Er​is the rubber elastic modulus, n is the number of layers, and k is the shape factor).

2、Shear Performance

1. Design shear strength: ≥1.5 MPa, shear elastic modulus (G): 0.6-1.2 MPa.
2. Allowable shear deformation: ≤0.5 times the thickness (at room temperature).

3、Uplift and Slip Resistance

1. Uplift force: Designed according to installation methods (e.g., bolt fixing), typically ≥5 kN (for small bearings).
2. Friction coefficient: μ≥0.3 when contacting concrete surfaces, μ≥0.25 when contacting steel plates.

IV. Environmental Adaptability

1、Temperature Range

1. Operating temperature: -40℃ to +80℃, short-term tolerance up to +100℃ (≤24h).
2. Low-temperature brittleness temperature: ≤-45℃ (in line with GB/T 1682 standard).

2、Chemical Resistance

1. Water resistance: After immersion in 23℃ water for 72h, weight change rate ≤±5%, strength reduction ≤10%.
2. Oil resistance: When contacting mineral oils (e.g., machine oil), oil-resistant neoprene is recommended, with volume expansion rate ≤15%.

V. Installation and Connection Methods

1、Fixing Methods

1. Bolt connection: Bearing pads are pre-drilled with bolt holes (diameter Φ6-Φ16mm), fixed to the foundation or components via expansion bolts.
2. Adhesive connection: Bonded to concrete or steel surfaces using high-strength rubber-specific adhesives (e.g., neoprene adhesives).

2、Joint Treatment

1. When splicing multiple bearings, the joint width ≤2mm, which should be filled with sealant to prevent water penetration.

VI. Standards and Certifications

• International standards: ASTM D1149 (rubber property testing), AASHTO LRFD (bridge bearing specifications), EN 1337-3 (European bearing standards).
• Chinese standards: GB 20688.4 (Part 4 of rubber bearings), JT/T 853 (neoprene bearings for highway bridges).

VII. Selection Reference Table

VIII. Testing and Acceptance

1. Factory testing: Each batch of products must undergo tests for hardness, tensile strength, and compression set (GB/T 7759).
2. Sampling ratio: 500 pieces per batch, sampling ≥3 pieces; if less than 500, count as one batch.

Note: Specific specifications can be customized according to engineering design requirements. For special properties such as aging resistance or high damping, technical parameters should be specified during procurement.