Realworld context: In 2024, a 35 year old prestressed concrete bridge in Texas was experiencing severe abutment cracking caused by restrained thermal expansion. The original fixed steel rocker bearings had seized. Engineers replaced them with PTFE laminated sliding bearings and applied 5201 2 silicone grease. After two years of monitoring, horizontal movements returned to design limits, cracking stopped, and the $470,000 replacement cost was 38% lower than a full pot bearing retrofit. This is the practical value of PTFE bearings.
PTFE laminated bridge bearings solve this problem by adding a sliding interface to a reinforced elastomeric bearing. A thin sheet (1.5–3 mm) of polytetrafluoroethylene (PTFE) — the same low friction material used in non stick cookware — is bonded to the rubber. When pressed against a mirror finished stainless steel plate, the friction coefficient drops to 0.02–0.05, allowing smooth, controlled sliding.
Figure 1: Cross section of a PTFE laminated bridge bearing]
All rubber and steel layers are vulcanized together into a single monolith. The PTFE sheet is bonded using a special adhesive that resists peeling and aging.
The rubber compresses under vertical load (up to 10,000 kN or more depending on size). Steel shims prevent excessive bulging, so the bearing maintains a uniform pressure distribution. When the bridge rotates (e.g., under a moving truck), the rubber deforms elastically — no additional moving parts are needed.
The PTFE–stainless steel interface is lubricated with silicone grease (e.g., 5201-2). This gives a static friction coefficient of 0.02–0.05 — lower than ice on ice. Typical design horizontal displacements: ±50 mm to ±150 mm, depending on bearing length and temperature range.
Sources of horizontal movement:
Daily & seasonal temperature changes (up to 50 °C variation)
Concrete shrinkage (0.2–0.4 mm/m over time)
Prestress shortening (2–5 mm per span)
Seismic ground motions
During an earthquake, the sliding friction acts as a passive energy dissipator. When horizontal inertia forces exceed the static friction, the bearing slides, converting seismic energy into heat and movement. This protects piers, columns, and girder ends from brittle failure. For this reason, PTFE bearings are used as multi directional sliding bearings in seismic zones (AASHTO LRFD Article 14.7.1).
The rubber layers absorb high frequency vibrations caused by vehicle tires and joint irregularities. Field measurements show vibration amplitude reductions of 25–35% compared to steel rocker bearings — which directly reduces bridge fatigue and improves ride comfort.
Project: Overpass bridge, twin steel girders, 3 spans of 35 m each.
Original bearing: Plain elastomeric pads (could not slide).
Problem: Thermal expansion caused excessive shear deformation; elastomeric pads cracked after 12 years.
Solution: Replaced with GYZF4 400×500 mm PTFE laminated bearings with stainless steel counterplates.
Results after 3 years:
Horizontal movement measured: +41 mm / –38 mm (design range ±50 mm)
No cracking in abutment backwalls
Friction coefficient measured on site: 0.032 (within spec)
Project cost: 212,000 ,.212,000vs.350,000 estimated for pot bearings
This case confirms that PTFE laminated bearings are not just “cheaper” — they are technically adequate for medium span bridges with moderate rotation demands.
Application | Typical Span | Recommended Bearing Type |
Highway overpasses | 20–40 m | Rectangular GJZF4 |
Continuous box girder bridges | 30–60 m | Round GYZF4 |
Incremental launching construction | Any | Temporary PTFE sliding pads |
Old bridge rehabilitation | Any (existing) | Replace fixed bearings with PTFE sliding |
Seismic retrofitting | Any | PTFE + external restrainers |
Do NOT use PTFE bearings when:
Rotation angle exceeds 0.02 rad (about 1.1°) — use pot or spherical bearings.
The bridge is very short (<15 m) — plain elastomeric pads may be cheaper and sufficient.
There is no access for future inspection/lubrication — sliding may fail.
Technical Advantages vs. Other Bearing Types (Expanded)
Feature | PTFE Laminated Bearing | Steel Pot Bearing | Spherical Bearing | Plain Elastomeric |
Max horizontal movement | ±50 to ±150 mm | ±30 to ±60 mm | ±50 to ±100 mm | Not designed for sliding |
Rotation capacity | ≤0.02 rad | Up to 0.04 rad | Unlimited | ≤0.03 rad |
Initial cost (relative) | 1× (baseline) | 1.8× – 2.5× | 3× – 5× | 0.6× |
Maintenance frequency | Every 5–10 years (re grease) | Low (sealed) | Low | None (but no sliding) |
Corrosion risk | Low (PTFE inert, rubber protects steel) | Moderate (seal failure) | Low (if stainless) | Low |
Ease of replacement | Very easy (low profile, light) | Difficult (heavy) | Difficult | Easy |
Unique strengths of PTFE laminated bearings:
Low profile – total height often <50 mm, reduces pier/abutment size.
Light weight – one person can carry a bearing up to 500 kN.
Corrosion resistant – PTFE unaffected by deicing salts or coastal spray.
Wide temperature range – verified for –40°C to +60°C.
Customizable – Round (GYZF4), rectangular (GJZF4), or square shapes; load ratings from 100 kN to 10,000 kN.
Figure 2: Applying silicone grease on PTFE surface
Step 1: Prepare Surfaces
Clean the stainless steel counterplate with isopropyl alcohol. Remove any dust, oil, or weld spatter.
Inspect PTFE sheet for scratches or damage. If scratches exceed 0.5 mm depth, replace the bearing.
Use 52012 silicone grease (other greases may degrade PTFE or rubber).
Apply a uniform layer, approximately 0.5–1 mm thick, covering the entire PTFE area.
Do not use graphite, molybdenum disulfide, or petroleum based greases.
Align the bearing with layout marks on the pier and girder.
Ensure the stainless steel plate is directly above the PTFE sheet (no offset).
Initial eccentricity should be less than 5% of the bearing length.
A steel bellows or heavy rubber boot prevents sand, road salt, and debris from entering the sliding interface. This is critical for achieving 30+ year life.
Make sure the cover allows free movement (± displacement range).
Specification drawing of the assembly PTFE Laminated bearing
Lower the girder slowly. Check with a feeler gauge that contact is even (gaps <0.5 mm).
If one corner is high, shim the bearing or adjust the support.
Common Mistakes (That Destroy Bearings)
Mistake | Consequence |
No grease → dry PTFE | Friction rises to 0.10–0.15, wear accelerates 10× |
Stainless steel plate missing | PTFE abrades against concrete → failure in months |
Eccentric placement | Edge crushing, reduced sliding travel |
No dust cover | Sand embeds in PTFE → scratches → high friction |
Using wrong lubricant | Rubber swelling or PTFE delamination |
Recommended inspection interval: Every 2 years for normal bridges; after any major seismic event (>0.2g peak ground acceleration).
Inspection item | What to look for | Acceptable condition | Action if failed |
Silicone grease | Presence, color | Thin, even, transparent/white | Clean & re apply grease |
PTFE surface | Wear depth, scratches | Wear <0.5 mm, no exposed fabric | Replace if >0.5 mm wear |
Stainless steel plate | Smoothness, corrosion | Ra ≤0.8 μm, no pitting | Polish or replace |
Dust cover | Integrity | No holes, no trapped debris | Repair or replace |
Signs that replacement is urgent:
PTFE worn down to the fabric interlayer (white fibers visible).
Rubber extrusion — steel shims exposed.
Bearing has slid off the edge of support (immediate jacking required).
Expected Service Life – Real Data
With proper design, installation, and 2 year greasing, PTFE laminated bearings consistently achieve:
Environment | Service life (years) | Failure mode most likely |
Clean, dry, dust proof (e.g., inside box girder) | 40–50 | Grease dries out only |
Typical highway bridge (with dust cover) | 30–40 | Grease contamination, minor wear |
Coastal or deicing salt, poor dust cover | 15–25 | PTFE edge wear, stainless corrosion |
No dust cover, no maintenance | 5–10 | Rapid abrasion, sliding failure |
Q1: Can PTFE laminated bearings be used in curved or skew bridges?
Yes, as long as the sliding direction aligns with the principal movement. For multi directional movement, use a round bearing (GYZF4). The PTFE surface can slide in any direction.
Q2: What is the maximum rotation angle?
Typically 0.02 rad (≈1.1°). If rotation is higher, consider a pot bearing or use a spherical bearing.
Q3: How often must the silicone grease be reapplied?
In normal conditions every 5–10 years. In dusty or wet environments, check every 2 years and re grease if dry or contaminated.
Q4: Can I replace a fixed bearing with a PTFE sliding bearing without modifying the bridge?
Often yes. The bridge is lifted slightly (using jacks), old bearing removed, stainless plate installed on girder, new PTFE bearing placed, and structure lowered. However, you must ensure the adjacent bearings can handle the redistributed movement.
Q5: Are PTFE bearings allowed by AASHTO?
Yes. AASHTO LRFD Bridge Design Specifications, Article 14.7.1, covers elastomeric bearings with PTFE sliding surfaces. The friction coefficient and design displacement must comply with the provisions.
