Spherical Bearing for Large Rotational Displacements

SB-1: Spherical bearing structure.

Spherical bearing, also called spherical bridge bearing, is one type of bridge bearings with large rotation capacity. Similar with pot bearing, spherical bearing also can be divided into three types: fixed spherical bearing, guided spherical bearing and free sliding spherical bearing. With high strengthened steel body, spherical bearing is especially designed for high vertical, horizontal and lateral loads and where large rotational structural displacements need to be accommodated.

Spherical bearing types
Fixed spherical bearing only allows for rotations, any longitudinal or traversal movement is restrained. Guided spherical bearing with edge steel guide accommodates unidirectional movements. Free sliding spherical bearing can slid in all directions.

Working principle of spherical bearing
Spherical bearing is formed by top steel plate, stainless steel slide, PTFE slide, convex plate, curved PTFE and concave plate. The sliding of convex plate and concave plate can accommodate the structural rotations of the beam end. The stainless steel slide and PTFE slide can further reduce friction coefficient, thus displacement of expansion and contraction can be accommodated. While, depending on whether the spherical bearing is fixed, guided or free sliding, the vertical loads, horizontal forces, longitudinal movements or transverse movements can be accommodated. What's more, the guided bar and the restraining ring also can transmit the horizontal forces. Thus, spherical bearings are especially suitable for more complex bridges.

Main technical performance

• Spherical bearing vertical loading capacity (kN): 1000, 1500, 2000, 2500, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 12500, 15000, 17500, 20000.
• Design displacement of spherical bearing
  • Bridge in longitudinal direction
    1000 - 2500 kN e = ±50 mm e = ±100 mm.
    3000 - 20000 kN e = ±50 mm e = ±100 mm e = ±150 mm.
  • Bridge in transverse direction
    Free sliding spherical bearing e = ±40 mm.
    The design displacement can be customized according to the project requirements).
• Design friction coefficient of spherical bearing (in condition of PTFE layer with silicon grease lubrication and stresses about 30 MPa).
  Normal temperature type: 0.03.
  Cold resistant type: 0.05.
• Design friction coefficient of spherical bearing (in condition of PTFE layer with silicon grease lubrication and stresses about 30 MPa).
  • Normal temperature type: 0.03.
  • Cold resistant type: 0.05.
• Horizontal force spherical bearing can withstand
  • Normal temperature type: 0.03.
  • Cold resistant type: 0.05.
• Working temperature
  • Normal temperature type: -25 °C to + 60 °C.
  • Cold resistance type: -40 °C to + 60 °C.

SB-2: Concave plates for making the spherical bearing.

SB-3: Top steel plate for making the spherical bearing.

SB-4: Spherical bearings are being produced.

SB-5: Spherical bearings are being inspected.

Features

• Large vertical loading capacity.
• Allows for large horizontal displacement.
• Better adapting to the large rotations.
• Minimum sliding friction coefficient.
• More suitable for the low temperature regions.
• High strengthened stainless steel makes it durability.
• Long termed economic cost.

Application

• Applicable bridges: RC bridge, PC bridge, steel bridge, railway bridge, easy dropping bridge, ends inclined bridge, etc.
• Applicable bridge conditions: bridges with large turning angles, wide and curved bridges, bridges with big torsions, bridges in low temperatures lower than -30 °C, etc.

SB-6: Spherical bearing is used for railway bridge.

SB-7: Spherical bearing is used for bridge in low temperature region.

Maintenance of spherical bearing
During using, the spherical bearing needs to be inspected and maintained regularly. And the inspection items are as following:

• Checking whether the anchor bolt is cut and the rubber sealing is cracking and aging.
• Checking whether the relative displacement of the spherical bearing is uniform and record the displacement one by one.
• Clean the debris and dust around the spherical bearing, while at the same time, using the cotton cleans surface of the stainless steel.
• Loose the anchor nut regularly, clean and oil the anchor nut to avoid rust, and then fasten the anchor nut.
• Check the height changing of the spherical bearing to confirm the abrasion condition of the PTFE slide. And when the height of spherical bearing changes over than 3 mm, the rubber sealing should be removed to inspect the condition of the PTFE slide.
• Painting the steel components of the spherical bearing regularly to avoid rust destroy (except the stainless steel slide).