Sway Platforms: Influence of Configuration, Topside Weight and Design Philosophy on Structural Reliability Available to Purchase

Moment magnification in platforms such as monopods and jack-ups may be addressed in a variety of ways in the design process. This paper investigates how differing treatments influence the reserve strength ratio (RSR) and hence structural reliability of sway platforms. Both WSD and LRFD versions of API RP2A are considered, together with several methods of estimating the moment magnification factor. The effect of varying topside weight is also incorporated — increasing topside load increases the second order moments but also increases the amount of steel provided by the Code to resist the loadings. It is found that the RSR varies widely for different structural configurations and may either increase or decrease with increasing topside weight. The RSR is also sensitive to the design approach adopted. As a result, a single set of partial load factors will not succeed in narrowing the spread of reliabilities across different configurations and design philosophies. Indeed, the use of a WSD format may result in more uniform reliability levels than API RP2A-LRFD for certain sway platforms.