Structural reliability analysis of the Load-out Support Frame (LSF) for structural safety assessment

Abstract

When an offshore platform topside is constructed in the yard, it has to be loaded out to the transportation vessel for its transportation to the installation site. In doing so, the Load-out Support Frame (LSF) is used to carry the whole weight of the topside from the yard ground (quay) to the transportation vessel. The LSF supports topside on top of the grillage during the transportation, and it becomes a Deck Support Frame (DSF). There are a lot of uncertainties duringthe load-out, transportation and installation operations, such as environment load, structural failure possibilities due to the welded or bolted joint connections etc. Therefore, the LSF should be considered structural reliability for itssafety assessment so that it may assess for the uncertainty in the material properties, in the construction quality (welding, bolting etc.), and in the load should be carried out to ensure safety. Especially, when the heavy weight of the topside platform (over 10,000 ton) is loaded in the load-out process, the structural reliability is critical matter in this operation. Even a small failure in the structural member or in the welding fracture lead to the instability of the heavy structural system and it may rise to a serious trouble or a disaster. In this paper, the assessment of the structural reliability of the (LSF) has been carried out. That is, probability failure (Pf) (or Reliability Index (RI)) is compu