Cross-sea bridge pot bearings GPZ1250GD

Detailed Introduction to Pot Bearing Model SPZ1250GD

1. Model Interpretation

The model "SPZ1250GD" follows the GB/T 17955-2015 standard (Chinese National Standard for Pot Bearings) and industry naming conventions, with each segment representing core attributes:

SPZ: Abbreviation for "Special Pot Bearing for Bridges" – indicating it is a specialized pot bearing designed for bridge infrastructure, with optimized load-bearing and displacement performance.

1250: Denotes the rated vertical load capacity of 1,250 kN (125 tons) – suitable for medium-span bridges (10–30 meters) such as urban overpasses and rural highways.

GD: Stands for "Guided Fixed Type" – a hybrid design that combines fixed bearing stability and guided bearing direction control: it restricts transverse (lateral) displacement while allowing limited longitudinal (axial) movement, preventing bridge girders from shifting off-track under dynamic loads.

2. Core Technical Parameters

Parameter Category

Specification Value

Remarks

Rated Vertical Load

1,250 kN

Tested under static load (1.5× rated load for 1 hour, no permanent deformation)

Horizontal Load Capacity

≥ 375 kN (30% of vertical load)

For resisting lateral forces from wind, vehicle centrifugal force, or seismic activity

Longitudinal Displacement

± 20 mm

Allowed movement along the bridge’s length (to compensate for temperature expansion/contraction)

Transverse Displacement

≤ ± 5 mm

Restricted to prevent lateral slippage (core "guided" function)

Allowable Rotation

0.02 rad (≈ 1.15°)

Accommodates bridge girder deflection under load (e.g., heavy trucks)

Friction Coefficient

≤ 0.03 (dry condition); ≤ 0.015 (with grease)

Based on PTFE-stainless steel sliding pair

Operating Temperature

-40℃ ~ +60℃

Suitable for most climates (cold northern regions to warm southern areas)

Service Life

≥ 30 years

Under standard maintenance and non-corrosive environments

3. Structural Composition & Material Advantages

SPZ1250GD adopts a 5-layer modular structure, each component engineered for durability and performance:

3.1 Cast Steel Basin (Load-Bearing Core)

Material: High-tensile Q345B low-alloy cast steel (yield strength ≥ 345 MPa).

Design Features:

Thickened basin wall (18 mm) and bottom (22 mm) to resist impact from heavy loads;

Hot-dip galvanization (zinc coating thickness ≥ 85 μm) + epoxy resin topcoat – protects against rust in humid or rainy environments (e.g., river-crossing bridges).

Function: Distributes vertical loads evenly from the bridge girder to the pier foundation, avoiding local stress concentrations.

3.2 PTFE Sliding Plate (Displacement Medium)

Material: Modified PTFE composite (blended with 15% glass fiber and 5% bronze powder) – enhances wear resistance by 40% compared to pure PTFE.

Dimensions: 180 mm × 150 mm × 8 mm (length × width × thickness); surface flatness tolerance ≤ 0.1 mm/m.

Function: Enables smooth longitudinal displacement with minimal friction, reducing mechanical wear on bridge girders.

3.3 Stainless Steel Sliding Surface

Material: 304 stainless steel (thickness 3 mm) – attached to the bottom of the bridge girder.

Surface Treatment: Mirror polishing (Ra ≤ 0.8 μm) – ensures tight contact with the PTFE plate and minimizes friction.

3.4 EPDM Sealing Ring

Material: Ethylene Propylene Diene Monomer (EPDM) rubber (Shore hardness 60±5).

Function: Seals the gap between the cast steel basin and PTFE plate, preventing dust, rainwater, or road salt from entering – prolonging the sliding pair’s service life by 5–8 years.

3.5 Steel Guide Rails

Material: 45# carbon steel (quenched and tempered, hardness HRC 28–32).

Installation: Two parallel rails fixed to the pier, on either side of the cast steel basin.

Function: Restricts transverse displacement to ≤ ±5 mm, guiding the bridge’s movement strictly along the longitudinal direction (critical for curved or mountainous highway bridges).

4. Key Functional Characteristics

4.1 Guided-Fixed Dual Performance

Unlike pure fixed bearings (no displacement) or pure guided bearings (unlimited single-direction movement), SPZ1250GD balances stability and adaptability:

Fixed function: Limits transverse displacement to protect bridge piers from lateral damage (e.g., from strong crosswinds).

Guided function: Allows ±20 mm longitudinal movement to compensate for temperature-induced expansion (summer) and contraction (winter) of concrete girders.

4.2 High Seismic Resistance

Integrated steel shear keys (embedded in the cast steel basin) – designed to yield at 400 kN horizontal load, absorbing seismic energy during moderate earthquakes (≤ 7 magnitude).

Post-seismic recoverability: The guided rails prevent permanent misalignment, enabling quick bridge inspection and restoration.

4.3 Low Maintenance & Durability

PTFE plate’s self-lubricating property eliminates the need for frequent grease replenishment (only reapply every 3–5 years).

Hot-dip galvanization + epoxy coating resists corrosion in industrial or coastal areas (tested to withstand 1,000 hours of neutral salt spray without visible rust).

5. Applicable Scenarios

SPZ1250GD is optimized for medium-span bridge projects requiring directional displacement control, including:

Urban overpasses and flyovers (resisting lateral traffic loads and wind forces);

Rural and suburban highway bridges (span 10–30 meters, adapting to temperature fluctuations);

Small river-crossing bridges (corrosion-resistant design for humid environments);

Industrial access bridges (supporting heavy truck loads up to 50 tons).

6. Installation & Maintenance Guidelines

6.1 Installation Requirements

Foundation Leveling: The pier top must be leveled to within ±0.5 mm/m – use cement mortar to adjust unevenness (prevents uneven load distribution).

Guide Rail Alignment: Ensure the guide rails are parallel to the bridge’s longitudinal axis (tolerance ≤ 1 mm/m) – misalignment will cause jamming during displacement.

Lubrication: Apply silicone grease (compatible with PTFE) to the sliding surface before installing the bridge girder – ensures friction coefficient ≤ 0.02.

Bolt Fastening: Use M24 high-strength bolts (8.8 grade) to fix the cast steel basin to the pier, tightening to a torque of 450 N·m.

6.2 Routine Maintenance

Inspection Frequency: Annually (urban bridges) or biennially (rural bridges).

Key Checks:

EPDM seal: Replace if cracks or deformation are found;

PTFE plate: Replace if wear thickness ≤ 4 mm (half of original 8 mm);

Guide rails: Check for loose bolts or bending (tighten or straighten as needed).

7. Quality Certification & Compliance

Complies with GB/T 17955-2015 (China) and EN 1337-5 (Europe) standards for pot bearings;

ISO 9001:2015 quality management system certified (from raw material inspection to finished product testing);

Each unit undergoes factory load testing (1.5× rated vertical load for 1 hour) and displacement testing (±20 mm longitudinal movement) before shipment – test reports provided with delivery.