How to Correct Quay Crane Girder Deflection Problem?

Quay Crane (QC) is the core equipment of the harbor loading and unloading operation, mainly used for rapid loading and unloading of ship containers. Due to its long-term high load operation, coupled with the influence of environmental factors (such as wind, foundation settlement, etc.), the problem of girder deflection occurs from time to time. Quay cranes generally divide the girder into two parts at the hinge point: the front and rear girders. Girder deflection not only affects the operating accuracy of the crane but also may cause safety hazards and even lead to equipment damage and operational delays. Therefore, how to effectively detect and correct girder deflection has become a key issue in harbor equipment maintenance.

In this article, we will analyze the causes of girder deflection of quay cranes and provide practical correction methods to help port operators extend equipment life and improve operational efficiency.

Analysis of the causes of beam deflection

First of all, let's understand the structural characteristics of single box girder single hinge point quay crane, whose front and rear girders are composed of single box girder, and the hinge point adopts single shaft connection (see Fig. 1). This structure has the advantages of light weight and small load bearing, but it also has the disadvantages of low rigidity and easy to be affected by external forces.

Common causes of girder deflection

The reasons for the deflection of the girder of the shore container crane are usually as follows:

• Uneven settlement of foundation: After long-term use of shoreside container cranes, the track foundation may settle due to geological changes or uneven loads, resulting in an imbalance of the level of the girder.
• Deviation of hinge point hole boring: In the assembly stage, if the accuracy of hinge point hole boring is not enough when the front and rear girders are docked, it will lead to the deflection of the front girder after installation.
• Rail installation error: the rail is unevenly laid or badly worn, causing the crane's running track to deviate.
• Welding residual stress release: the V-shaped structure at the hinge point has a large amount of welding, and the residual stress is gradually released under the action of barge or strong wind, resulting in the contraction of one side and the stretching of the other, which ultimately leads to the formation of skew.
• Influence of external force: Strong wind, collision, or improper operation may lead to an instantaneous uneven force on the beam, which triggers deflection.
• Limitations of single hinge point structure: Compared with a double box girder double hinge point bank bridge (face contact + high rigidity), a single hinge point bank bridge has weaker torsion resistance and is more susceptible to external forces.

How to detect girder deflection?

Before correction, the deflection of the girder needs to be detected accurately, commonly used methods include:

• Laser level measurement: To detect the horizontal and vertical deviation of the girder.
• Total station monitoring: Used to track the deformation trend of the beam over a long period.
• Sensor real-time monitoring: Some modernized ports adopt intelligent sensors to monitor the status of the girder in real time.

Effective methods for correcting beam deflection

a. Adjusting track leveling

If the deflection is caused by the rail problem, it can be used:

• Track shim adjustment: Add shims under the low side track to restore the level.
• Rail recalibration: Use professional equipment to readjust the rail spacing and levelness.

b. Reinforcement or repair of the beam structure

• Welding reinforcement: Patch welding on the deformed parts to restore the structural strength.
• Partial replacement: If the deformation is serious, part of the beam components can be replaced.

c. Use hydraulic jacking to correct

For larger deflections, hydraulic jacks can be used to jack up the beams with laser calibration to gradually restore the level.

d. Strengthen routine maintenance

• Regular inspection: Establish a mechanism to monitor the deformation of the girder and deal with it as early as possible.
• Windproof measures: Lock the crane before strong winds to reduce the influence of external forces.

Measures for preventing beam deflection usually have the following 3 points

• Optimize the welding process: use symmetrical welding to reduce residual stress.
• Add a real-time monitoring system: use sensors to monitor the deformation trend of the girder.
• Control manufacturing accuracy: ensure that the hinge point hole matching boring meets the standard.

Conclusion

The girder deflection problem of a single-box girder single-hinge-point bank bridge needs to be solved comprehensively from three aspects: structural design, manufacturing process, and correction technology. High-altitude hinge point boring is the most reliable correction method at present, but it needs to strictly control the construction safety and accuracy. Port enterprises should strengthen the daily monitoring and maintenance to prolong the life of the equipment and ensure operational safety.

For more detailed maintenance solutions for quay cranes, please consult the Weihua team. We specialize in producing and selling all kinds of port equipment!