Stability and motion response analyses of transport with barge
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The water has been used for transportation for ages. The barge started early to become one of the most effective methods to perform such an operation. Over the years the floating flat-bottomed structure has been developed until the one we use today which is characterised by its flat bottom and large deck area. An offshore transport can be divided into three phases, each having its own considerations. The first phase may be called on-loading and here the stability is important. The next phase is named the transport. Here the most important aspect is the motion responses of the barge to the physical environmental conditions. Especially the waves give the barge accelerations which may cause movement of the cargo. To prevent this movement seafastening has to be designed to withstand the forces created by the accelerations. The last phase is the off-loading. Here resonance is the main problem. This phenomenon may cause large motions and accelerations and thereby cause the whole operation to be postponed. The stability analysis is used to decide the intact stability and the damaged stability. The results are compared with criteria given in DNV(1996) and Noble Denton (2005). The requirements states whether the operation is secure according to the stability principle. The motion response analysis uses physical environmental conditions given by Noble Denton (2005) to find the accelerations due to the motions. The seafastening need to be designed according to these accelerations to have a secure transport. The case study included in this report is the analyses of stability and motion response of a barge loaded with 4 bridges and 2 towers. The barge is subjected to physical environmental conditions according to the Valhall field in the southern North Sea (Grant, 2005). A program package called SESAM, including the programs GeniE, HydroD and POSTRESP, is used to perform the analyses. The main results give a range of stability of 76,8 degrees for intact stability and 61,8 degrees for damaged stability with two adjacent flooded tanks. Both these are on the correct side of the requirements.
Master's thesis in Offshore structural engineering