Performance based design of blast resistant offshore topsides, Part I: Philosophy

The philosophy of performance based design of blast resistant offshore systems is an approach by which structural components are allowed to behave in a controlled non-linear characteristic that satisfies the demand criteria for preventing loss of lives, asset protection and integrity of escape routes. As the approach is based on behaviour rather than a prescriptive performance, uncertainties are removed which attributes to a precise design compared with a traditional design method. In the context of offshore installations, particularly for topside structures where safety cannot be compromised, this will lead to an economical design as well as meeting the functionality of a system from pre to post explosion regimes. This paper presents a performance based design philosophy for a typical topside structure which has the merit of being informative to the client and to regulators. This method also assists engineers in the comparison of engineering solutions which can be correlated to performance levels for which the installation has been designed and protected.The paper is divided into two sections. The first section discusses the methodology of the approach accompanied by a design algorithm assessment in which the principles of performance based design are emphasized in order to achieve the specific demand level for attainment of performance objectives. The second section demonstrates its application followed by a design example of a typical offshore topside to assess deck plate resistance against a defined blast load level.