A comparison of common structural rules with previous class rules

The paper compares the scantling criteria of rules individually issued in the last years by classification societies, with the recently released Common Structural Rules (CSR). The evolution of the rules background criteria for scantlings is examined, also in connection with the debate at IMO level of the concept of Goal Based Design. The attention is focussed on the progress towards the identification of reference scenarios able to clarify the content of the rules themselves. A clearer definition of reference environmental conditions, of the corrosion model and of failure modes are the fields where this trend is recognised. Less evident is the identification of scenarios for accidental conditions. After this first general analysis on the goals of rules, the evolution in terms of consistency of the formulations to the target is examined. Evolution trends in the definition of characteristic loads and strength values and of combination criteria are seen from a probabilistic and risk based viewpoint. Changes in the formats for design checks of structures are also monitored.