Figure.1: Bridge Bearing Replacement Procedure.

Bridge Bearing Replacement Procedure || Procedures For Maintenance And Rehabilitation Of Bridges

Figure.2: Excessively Tilted bearings and Supported By Wooden planks

Figure.3: Damaged Pedestals.

Bearing Replacement & Lifting of Superstructure for Replacement of Bearing and Pedestal: 

The Bridge shall be closed for the traffic during replacement of the bearings.

1. The following method sequence to be adopted for replacement of the bearings:

A. It is first very important to open the expansion joints and disconnect the spans. The top wearing course, including the bitumen topping if any has to be chipped out of a width of at least 50 mm along every expansion joint.

B. All expansion joints should be cleared from any debris dust etc.

C. Provide steel plate of 20 mm on top of pier cap (below the location of the jacks) and below the bottom of the diaphragm beam (top of the jacks).

D. Now fix the hydraulic jacks of 100 Tn capacity (or as per load requirements) for each pier (2 on each diaphragm beam ) along with Screw jacks (or wooden logs) suitably placed between the hydraulic jacks. All the jacks to be placed below the diaphragm beams as shown in the diagram.

Figure.4: Schematic diagram for replacement of bearing

Figure.5: Lifting Superstructure to replace bearings and Pedestals.

Figure 6: Supporting Hydraulic Jacks of 100 TN capacity

E. Set of requisite hydraulic jacks to be connected to a single power pack.
F. Now commence the lifting process by operating all the jacks and simultaneously tighten the screw jacks. The lifting should be done for a up to height of 10 mm.
G. Remove the existing damaged bearing and then fix the new bearings as per design and lower the span on the new bearing.

2. The following method sequence to be adopted for replacement of the cracked

bearing pedestals:

A. Cleaning of the Concrete Surface: Concrete on the damaged or loose area shall be chipped/removed. And dust particles from the opening area shall be removed by an air blower.

B. Reinforcement and applying corrosion protective chemical: If old bearing pedestal is to be rehabilitated, the chipped surface shall be thoroughly cleaned by wire brush to remove loose rust particles then exposed reinforcement shall be cleaned of all rust and millscale by mechanical wire brush, to removal of oil or greasy residues and also the loss of reinforcement shall be compensated by tying of new reinforcement. If a new bearing pedestal is to be cast, then the new reinforcement shall be anchored and tied up with existing reinforcements of pier cap, through special SS fasteners and shall be shaped for the new bearing pedestal to be cast. The reinforcement’s rust, if any, shall be removed by applying rust removal, chemical (Reebaklens RR of Fosroc or equivalent product of BASF or Sika) and cleaning of reinforcement with a mechanical wire brush. After that applying one coat of zinc rich coating of Nitozinc Primer of Fosroc or equivalent product of BASF or Sika).

C. Micro-concrete: Flowable mix of 1part by weight of Micro-concrete power, 1 part by weight of grit/Aggregate (up to 10mm) and necessary water required for workability. The mix shall be mixed thoroughly by mechanical stirred for about 3 mins.

D. Applying: After providing necessary water tight shuttering, the flowable mix should be poured and there is no need for compaction as it is flowable and self compacting mix.

E. Curing: The curing of pedestal shall be done for at least seven days.

Maintenance of bridge bearings: 

1. Surrounding of all bearings shall be cleared of silt and debris.

2. In case of POT-PTFE bearings, I have noticed in some cases that temporary clamp did not disconnect after installation of the bearing. Fixed temporary clamp interrupts the bearing function.  So after installation of POT-PTFE bearings, You need to pay attention to disconnect the temporary clamp. 

3. In case of metal bearings, dirt,rust and corrosion are common remedies due to weather affect.

For Bearing rust removal and Cleaning/repainting: The following stepwise treatment is to be followed:

A. The area around the bearings and their pedestals shall be cleared of all debris,
vegetation, dust, etc. And cleaned for proper inspection.

B. Fresh graphite grease as approved by the Engineer shall be applied to the surfaces which are siding, rotating or moving due to movement in bearings.
C. All other surfaces of the metallic bearing shall be cleaned of all rusts, corrosion and a coat of anticorrosive oil paint applied.

Click the following links to read more:

Procedures For Maintenance And Rehabilitation Of Bridges

Function and Type Of Expansion joints In Bridges | Details of Expansion joints

A Sample Of Bridge Inspection Report

Type Of Bridge Bearing | Function Of Bridge Bearing

Components Of Bridge | Basic Parts of A Bridge | Bridge Elements

Proforma of Bridge Inspection Report As Per IRS SP 35

Bridge Foundation | Type-Of-Bridge-Foundation

Classification-Of-Bridges | Type-Of Bridges

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