On the Longjiang Road elevated ramp in Changzhou, synchronous jacking was employed to replace the bearings. Thirty‑two low profile, self‑locking hydraulic cylinders (200t, 50mm stroke) were used, paired with two PLC‑driven, 8‑point intelligent synchronous jacking hydraulic systems achieving ±0.5 mm synchronization accuracy. The ramp was lifted as a single unit by installing the cylinders on the piers. After jacking, the damaged rubber bearings and related ancillary components were repaired and serviced. Once maintenance was complete, the cylinders were lowered and the ramp was returned to its original position, with the overall jacking operation achieving excellent results.
Rubber bearings are prone to aging due to their material properties and prolonged exposure to overload conditions, frequently resulting in cracking, void formation, and excessive shear deformation. As traffic volumes rise, vehicle weights increase, and axle loads grow, bearing damage accelerates exponentially. Therefore, once signs of aging are detected, prompt replacement must be scheduled to ensure the safe operation of the bridge deck.
Since the girder must be lifted to replace the bearings, a temporary traffic interruption is required during the replacement process. Therefore, the project demands convenient execution, a short construction period, and minimal impact on traffic. The contractor promptly established an overall bridge jacking plan, and all aspects of the project were carried out in an orderly manner. The following outlines the specific process for bearing replacement on the Longjiang Road elevated ramp in Changzhou.
Urban Elevated Ramp Bearing Replacement Procedure:
1.Position the hydraulic cylinders and sensors by placing the cylinders on top of the piers, and pre-install sensors on the horn brackets at critical locations.
2.Connect the hydraulic cylinders and sensors to the synchronous jacking system and the PLC control cabinet.
3.Start the control computer to monitor real-time data from each sensor and automatically analyze the safety status during the bridge jacking process. The system provides visual and graphical feedback throughout the operation.
4.Initial Alignment (Pre‑loading): Pre‑loading is performed to eliminate non‑elastic deformation of the supports and settlement of the foundation. All jacks are raised synchronously, keeping the stroke lengths roughly equal. Stop jacking just as the bridge deck begins to lift off the bearings. Pause for 1–2 hours to monitor potential settlement and beam movement.
5.Full lifting: After confirming system stability during the observation period, proceed with the overall synchronous jacking. The stroke speed of each jack is controlled precisely by the synchronous jacking system to maintain uniform lifting at all points.
6.Mechanical Locking: Once the girder or deck is raised sufficiently to release bearing pressure, tighten the locknuts on all self‑locking hydraulic jacks to secure the pistons, ensuring safety for subsequent operations.
7.Bearing Replacement: Remove and replace the aged or damaged bearings.
8.Unlocking the Cylinders: Loosen the locknuts on all self‑locking hydraulic cylinders and prepare for piston retraction.
9.Lowering the Girder: Once all tasks are completed, lower the hydraulic jacks synchronously to restore the girder onto the new bearings. The replacement process is now complete.
