March 12, 2026
Bridge bearings are designed to last 25–50 years, but their service life depends heavily on the quality of the original installation, the maintenance regime, and the environmental conditions. When bearings reach the end of their service life — through wear, corrosion, seismic damage, or simple age — they must be replaced to prevent the development of unintended restraint forces that can cause cracking and structural damage. Bearing replacement requires lifting the bridge superstructure off the existing bearings, removing the old bearings, installing new ones, and lowering the superstructure back down. The tool that makes this possible safely and precisely is the synchronous hydraulic jacking system.
A bridge superstructure is a complex, statically indeterminate structure. If it is lifted unevenly — with one jack rising faster than the others — differential settlements are introduced that can cause cracking of the concrete deck, yielding of the steel girders, or damage to the bearings themselves. The consequences can be severe and costly. Synchronous jacking eliminates this risk by using a central PLC controller to monitor the load and displacement at every jack simultaneously and to adjust the hydraulic pressure in real time to maintain a perfectly level lift. The tolerance is typically ±1 mm across all jack positions, regardless of the number of jacks or the span of the bridge.
A synchronous hydraulic jacking system in operation during a bridge bearing replacement. The PLC controller (right) monitors the load and displacement at each of the four jacks in real time, maintaining a level lift within ±1 mm to prevent secondary stresses in the structure.
Successful bearing replacement begins with thorough preparation. The structural engineer must first analyse the bridge to determine the jack positions, the required lift height, and the maximum allowable differential settlement. The jack positions are typically at the pier cap, as close as possible to the bearing locations, to minimise the cantilever moment in the deck during lifting.
The bearing shelf must be surveyed to confirm that it is level and capable of supporting the jack reaction forces. If the concrete is deteriorated, local repair may be required before jacking. Temporary works — typically steel spreader beams — are designed to distribute the jack loads over a sufficient area of the bearing shelf. Monitoring points (survey targets or displacement transducers) are installed on the superstructure to provide independent verification of the lift.
With the jacks in position and the PLC system commissioned, the lift begins. The operator initiates the lift from the PLC console, and the system automatically controls all jacks simultaneously. The lift rate is typically slow — 0.5–2 mm per minute — to allow the structure to respond and to give the operator time to intervene if any anomaly is detected. The target lift height is typically 10–20 mm above the bearing seating level, sufficient to allow the old bearing to be slid out and the new one to be positioned.
Throughout the lift, the PLC system continuously monitors and logs the load at each jack and the displacement at each monitoring point. If any jack deviates from the target displacement by more than the specified tolerance, the system automatically pauses the lift and alerts the operator. This closed-loop control is what distinguishes synchronous jacking from conventional jacking and makes it the only acceptable method for lifting complex bridge structures.
With the superstructure safely supported at the target height, the bearing replacement work can proceed. The old bearing is released from its anchor bolts (if applicable) and slid out from the pier cap. The bearing shelf is cleaned, and any deteriorated concrete is repaired. The new bearing is positioned on the shelf, aligned with the bridge axis, and the anchor bolts (if required) are installed and torqued to the specified value.
With the bridge superstructure safely supported by hydraulic jacks, workers remove the deteriorated bearing from the pier cap. The new bearing is visible in the foreground, ready for installation.
The lowering operation is the reverse of the lift, and is equally critical. The PLC system controls all jacks simultaneously, lowering the superstructure at a controlled rate onto the new bearings. As the load transfers from the jacks to the new bearings, the load readings at each jack are monitored to verify that the load distribution matches the design values. Any significant deviation may indicate a bearing alignment problem that must be corrected before the full load is transferred.
| Bridgent Jack Model | Capacity (tonnes) | Stroke (mm) | Application |
|---|---|---|---|
| BJ-50 | 50 | 200 | Small bridge bearings, slab bridges |
| BJ-200 | 200 | 300 | Medium span bridges, viaducts |
| BJ-500 | 500 | 400 | Long-span bridges, cable-stayed bridges |
| BJ-1000 | 1,000 | 500 | Major bridge structures, heavy loads |
Bridgent supplies double-acting, lock-nut hydraulic jacks and PLC-controlled synchronous jacking systems for bridge bearing replacement and other bridge lifting operations. Our systems include load cells, displacement transducers, hydraulic power units, and the PLC control console. We provide full technical support including jack positioning design, lift procedure development, and on-site supervision. Contact us for a quotation on your next bearing replacement project.
Bridgent is your specialist partner for bridge construction and maintenance materials. From CFRP and post-tensioning systems to hydraulic jacks and noise barriers, we supply the complete range with full engineering support.
Tags:Bridge MaintenanceHydraulic JackingBridge Bearing ReplacementBridge ConstructionBridgent Products
Westcoast New Area, Qingdao City ,Shandong Province ,China
