C.S. Wijesinghe
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Offshore Pile Run Mitigation
Evaluation of pile run mitigation systems for decreasing the shockload in an offshore crane
This thesis presents an evaluation of pile run mitigation systems for decreasing the shockload in an offshore crane. Monopiles for windturbines at sea are installed with offshore cranes on jack-up or floating vessels. During driving of the monopile with an impact hammer, the pile can lose its support due to a sudden reduction in soil resistance. This causes falling of the pile which is called pile run. As the hammer has slack rope when it is supported by the pile, it will fall along with the pile until it is suddenly suspended in the crane rigging, which causes a shockload on the crane and in the crane wire. Different pile run and shockload mitigation solutions were collected, after which a shockload model was created with Matlab and Simulink. This model gives insight into the influence of the most important components of the hammer-crane-vessel system on the shockload and calculates the total shockload in sling, MH tackle and crane wire with or without a mitigation solution. It was found that the shock load model should include a hammer, sling, MH tackle, boom, boomhoist and reeving for accurate calculation of the shockload and for evaluation of the mitigation solutions. The vessel roll motion only has a small influence on the shockload and was neglected for the final shockload model. Most of the mitigation solutions were evaluated with the shockload model, except for the solutions that avoid hammer suspension in the crane. The other mitigation solutions were analysed and evaluated for the Bokalift 2 crane, all with the same conditions of 1m slack rope, free fall and a hammer mass of 1400t. As this is a quite conservative calculation, a plot with all the allowable combinations of slack rope length and average hammer acceleration was presented as the main conclusion of this work. With this, the soil resistance can also be taken into account to make the analysis and evaluation more realistic. The shock load absorber under the hook is suitable for reducing the shockload under the allowable load, whereas the shock load absorber in the crane reeving is not as it is too slow. The flexible sling is only a suitable mitigation solution when there is still sufficient soil resistance during the pile run. For free fall and 1m slack rope, it would not be sufficient as common sling materials have a too low strength/Emodulus ratio. Controlling the slack rope length or limiting pile speed is a suitable mitigation solution if the correct combination of slack rope length and average hammer acceleration (from slack to taut rope) can be guaranteed.
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This thesis presents an evaluation of pile run mitigation systems for decreasing the shockload in an offshore crane. Monopiles for windturbines at sea are installed with offshore cranes on jack-up or floating vessels. During driving of the monopile with an impact hammer, the pile can lose its support due to a sudden reduction in soil resistance. This causes falling of the pile which is called pile run. As the hammer has slack rope when it is supported by the pile, it will fall along with the pile until it is suddenly suspended in the crane rigging, which causes a shockload on the crane and in the crane wire. Different pile run and shockload mitigation solutions were collected, after which a shockload model was created with Matlab and Simulink. This model gives insight into the influence of the most important components of the hammer-crane-vessel system on the shockload and calculates the total shockload in sling, MH tackle and crane wire with or without a mitigation solution. It was found that the shock load model should include a hammer, sling, MH tackle, boom, boomhoist and reeving for accurate calculation of the shockload and for evaluation of the mitigation solutions. The vessel roll motion only has a small influence on the shockload and was neglected for the final shockload model. Most of the mitigation solutions were evaluated with the shockload model, except for the solutions that avoid hammer suspension in the crane. The other mitigation solutions were analysed and evaluated for the Bokalift 2 crane, all with the same conditions of 1m slack rope, free fall and a hammer mass of 1400t. As this is a quite conservative calculation, a plot with all the allowable combinations of slack rope length and average hammer acceleration was presented as the main conclusion of this work. With this, the soil resistance can also be taken into account to make the analysis and evaluation more realistic. The shock load absorber under the hook is suitable for reducing the shockload under the allowable load, whereas the shock load absorber in the crane reeving is not as it is too slow. The flexible sling is only a suitable mitigation solution when there is still sufficient soil resistance during the pile run. For free fall and 1m slack rope, it would not be sufficient as common sling materials have a too low strength/Emodulus ratio. Controlling the slack rope length or limiting pile speed is a suitable mitigation solution if the correct combination of slack rope length and average hammer acceleration (from slack to taut rope) can be guaranteed.
The increasing global container trade has intensified demands on container handling technology. Automation has addressed many challenges, but limitations persist, particularly in spreader design. These attachments, equipped with rotating twist locks, rely on remote-controlled actuators and sensors. However, current designs exhibit frequent maintenance, multiple failure points, and limited sensing capabilities. Additionally, dependence on external power restricts mobility, limiting their use in smaller terminals and remote operations. This research employs an iterative design approach to develop a novel spreader that reduces maintenance frequency by 75 percent, minimizes failure points by 50 percent, and integrates an advanced control algorithm with built-in error detection. This reduces reliance on remote operators, enhancing safety by mitigating operator fatigue-induced errors. An internal power source enables 20 hours of continuous operation, while the independent control system reduces downtime by 1 hour, minimizing delays from operator breaks.
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The increasing global container trade has intensified demands on container handling technology. Automation has addressed many challenges, but limitations persist, particularly in spreader design. These attachments, equipped with rotating twist locks, rely on remote-controlled actuators and sensors. However, current designs exhibit frequent maintenance, multiple failure points, and limited sensing capabilities. Additionally, dependence on external power restricts mobility, limiting their use in smaller terminals and remote operations. This research employs an iterative design approach to develop a novel spreader that reduces maintenance frequency by 75 percent, minimizes failure points by 50 percent, and integrates an advanced control algorithm with built-in error detection. This reduces reliance on remote operators, enhancing safety by mitigating operator fatigue-induced errors. An internal power source enables 20 hours of continuous operation, while the independent control system reduces downtime by 1 hour, minimizing delays from operator breaks.