Spherical Bearing Standards & Applications

Spherical bearings (PTFE-on-steel sliding spherical elements) remain a standard solution where large rotations and significant vertical load transfer are required. The European standard EN 1337-7 is the accepted design/manufacturing baseline in Europe; the U.S. has ASTM D5977 (and AASHTO guidance); China publishes GB/T 17955 and TB/T 3320. Key differences lie in materials, sliding specifications, horizontal load practices, testing and documentation.

A spherical bridge bearing comprises a precision-machined convex stainless-steel surface that bears on a matching concave steel element covered with PTFE. Configurations include fixed, guided, and free-sliding. They are chosen where rotation capacity and/or high vertical load capacity are required while permitting controlled translation.

• EN 1337-7:2004 - Spherical and cylindrical PTFE bearings (Europe)
• ASTM D5977 - High Load Rotational (Spherical) Bearings (USA)
• GB/T 17955-2009 - Spherical bearings for bridges (China)
• TB/T 3320-2013 - Railway bridge spherical bearings (China)
• AASHTO / AISC guidance - Complementary U.S. design practice

All standards assume a stainless-steel convex element sliding over a PTFE surface, recognize fixed/guided/free-sliding types, and require dimensional checks, material certifications, NDT for welds, and sliding surface acceptance.

4.1 Scope & nominated design limits
EN 1337-7 is metric, oriented to European practices. ASTM D5977 is inch-pound, prescriptive about PTFE interfaces, and gives explicit allowable horizontal-to-vertical ratios. Chinese GB/T is similar to EN but more prescriptive; TB/T is stricter for rail.
4.2 Sliding material & lubrication rules
EN refers to EN 1337-2 for PTFE, allows UHMWPE alternative with testing. ASTM prescribes PTFE+stainless pairing. China requires PTFE with test reports.
4.3 Horizontal loads & design philosophy
ASTM/AASHTO uses a common rule: horizontal ≤ ~10% of vertical capacity, higher loads require testing. EN uses contact stress checks and design calculations. China is similar, but railway stricter.
4.4 Testing & manufacturing control
EN: QA, material certs, sliding tests. ASTM: acceptance tests, NDT, mill certs. China: QA records, sampling tests, third-party certificates.

• 1. Specify standard and edition.
• 2. State units (metric/imperial).
• 3. Require material certs for steel/PTFE.
• 4. Require QA & NDT.
• 5. Request sliding performance test data.
• 6. Define acceptance tests clearly.
• 7. Provide installation/maintenance instructions.
• 8. Define warranty & spare parts.
• 7. Typical applications

• Highway and rail bridges
       • Interchange flyovers
       • Industrial supports

• Ambiguous standard references
• Assuming PTFE properties
• Neglecting horizontal load testing
• Missing NDT on welds

Western clients should specify the exact standard edition, require 3rd-party inspection, define sliding tests under expected loads, and consider seismic/rail project needs.

EN 1337-7, ASTM D5977, and Chinese GB/T/TB/T describe fundamentally the same type of bearing, with differences in units, test requirements, and conservatism. For cross-border procurement, specify the exact standard edition, require certificates and tests, and define sliding performance under expected service conditions.