Experimental Investigation On Continuous Load Transfer Process Of Twin-Barge Float-Over Installation

The objective of the present study is to investigate the dynamic motions and impact loads of twin-barge floatover installation with the model tests, which involve multi-body interactions between wave-induced vessel motions and constraint components. A particular contribution of the model tests is that a novel remote rapid (de) ballasting system based on an intelligent algorithm is provided to change the draft of transportation and installation barges continuously, and the load transfer process of twin-barge float-over installation can be simulated in a continuous manner. In addition, several shock absorbers with adjustable constraint components, including the deck support units (DSUs), leg mating units (LMUs), surge and sway fenders, are carefully designed to smooth the continuous load transfer process. The impact loads between topside, barges and substructure can be captured accurately and efficiently. Two typical cases in the mating phase of twin-barge float-over installation, namely Case B2B where the topside is transferred from transportation barge to installation barges, and Case B2J where the topside is transferred from installation barges to pre-installed jacket, are simulated in the model tests. Results indicate that the impact loads on the DSUs of transportation barge increase and those on the DSUs of installation barges decrease continuously as the draft of transportation barge increases in Case B2B. Furthermore, the impact loads on the DSUs of installation barges decrease and the impact loads on the LUMs of Jacket increase continuously as the draft of installation barges increases in Case B2J. The relative motions and impact loads between the topside, barges, and jacket are within an acceptable limit in the investigated conditions. In addition, two particular phenomena are captured in the model tests. One is that the load transfer rate of the topside is closely related to the trim angle of the transportation barge, and another one is that the separations between stabbing pins of topside and receptor cones of DSUs are asynchronous. These phenomena have never been observed in conventional simulation methods.