Elastomeric Bearings: A Comprehensive Guide to EN 1337-3:2005
Elastomeric bearings are critical components in bridge and civil engineering structures, enabling translational and rotational movements while transmitting loads safely. For global engineers, contractors, and manufacturers, understanding two pivotal standards-Europe's EN 1337-3:2005 and China's GB/T 20688 series-is essential to ensure compliance, performance, and cross-market compatibility.
1. Introduction to EN 1337-3:2005 – Europe's Benchmark for Elastomeric Bearings
EN 1337-3:2005 is the European Committee for Standardization (CEN)'s definitive standard for elastomeric structural bearings, approved in 2004 and enforced across EU/EEA member states since 2005. It governs the design, materials, manufacturing, testing, and conformity of bearings used in bridges and similar structures with comparable support conditions.
★Key Scope & Application
Product Types: Covers laminated bearings (Types A/B/C), laminated sliding bearings (Types D/E with PTFE sliding surfaces), and plain pad/strip bearings (Type F).
Dimensions & Materials: Plan dimensions up to 1200×1200 mm; limited to natural rubber (NR) or chloroprene rubber (CR) (no reclaimed rubber allowed).
Temperature Range: -25°C to +50°C (short-term up to +70°C); extreme low-temperature (-40°C) applications require additional shear modulus validation.
★Core Technical Requirements
Shear Modulus: 0.7 MPa, 0.9 MPa, or 1.15 MPa (23°C, with tolerances ±0.10 MPa to ±0.20 MPa); low-temperature (-25°C) and aged (70°C for 3 days) variants must meet strict limits.
Bond Strength: Steel-elastomer and PTFE-elastomer interfaces must withstand shear strain up to 2 without cracking or delamination.
Compression Performance: Repeated compression (2 million cycles) allows ≤12% modulus increase; no bonding defects or plate misalignment.
Manufacturing Tolerances: Plan size ±2/+4 mm; elastomer layer thickness tolerances ±10%–±15% (depending on layer thickness); total bearing thickness tolerances ±2 mm (≤100 mm) to ±4 mm (>150 mm).
★Conformity & CE Marking
Compliance requires factory production control (FPC) per Annex N and two conformity assessment systems:
System 1: For critical applications (e.g., bridge main bearings) – includes third-party type testing, factory inspection, and ongoing surveillance.
CE marking (per Annex ZA) mandates disclosing key specs (e.g., shear modulus, steel yield strength, operating temperature).
2. China's GB/T 20688 Series – Equivalent Standards for Global Compatibility
China's GB/T 20688 series (GB/T 20688.3-2006 and GB/T 20688.4-2006) is technically aligned with EN 1337-3:2005 but tailored to local engineering needs. It is mandatory for projects in China and widely recognized for international collaborations.
Key Correlations to EN 1337-3:2005
|
Feature |
EN 1337-3:2005 |
GB/T 20688 Series |
|
Core Product Coverage |
Laminated, sliding, plain pad/strip bearings |
GB/T 20688.3 (ordinary bearings) = EN Types A/B/C/F; GB/T 20688.4 (sliding bearings) = EN Types D/E |
|
Material Requirements |
NR/CR, no reclaimed rubber |
Same material restrictions; identical physical/mechanical specs (tensile strength ≥14 MPa for bearing samples, compression set ≤15% for CR) |
|
Shear Modulus |
0.7/0.9/1.15 MPa |
Matching standard values; extended low-temperature (-40°C) validation for cold regions |
|
Sliding Surface |
PTFE thickness 1.5–2.5 mm |
PTFE thickness 1.5–3 mm; identical lubrication dimple area (20%–30%) and volume (10%–20%) requirements |
|
Testing Methods |
Shear modulus (Annex F), compression (Annex H), bond strength (Annex G) |
Equivalent test methods (GB/T 528 for tensile strength, GB/T 7759 for compression set) aligned with ISO standards referenced in EN 1337-3 |
3. Practical Guidance for European & American Stakeholders
When to Use Which Standard?
EU/EEA Projects: Mandate EN 1337-3:2005 with CE marking; ensure compliance with CEN member state national annexes (e.g., partial safety factors).
Chinese Projects: Use GB/T 20688.3/4; for seismic applications.
Global Projects: Prioritize dual compliance – most technical requirements overlap, but verify temperature ranges, tolerances, and testing methods (e.g., GB/T 20688's stricter low-temperature validation).
Key Considerations for Cross-Market Collaboration
Material Consistency: NR/CR are universal, but confirm GB/T 20688's polymer blending limits (≤5% secondary polymer) match EN 1337-3
Testing Alignment: Use ISO-equivalent test methods (e.g., ISO 37 = GB/T 528, ISO 1431-1 = GB/T 7762) to avoid redundant testing.
Marking & Documentation: For CE marking, reference EN 1337-3; for Chinese projects, include GB/T 20688 compliance certificates and factory inspection reports.
Conclusion
EN 1337-3:2005 and GB/T 20688 are complementary standards that set global benchmarks for elastomeric bearing performance. European and American professionals can leverage their technical alignment to streamline cross-border projects, while understanding regional adaptations (e.g., China's low-temperature and seismic provisions) ensures compliance and reliability.
For projects requiring dual-market access, prioritize harmonized materials, shared testing protocols, and clear conformity documentation. By mastering these standards, engineers and manufacturers can deliver safe, durable bearings for bridges and civil structures worldwide.
