Incremental wave analysis and its application to performance-based assessment of jacket platforms

In this paper, a relatively novel approach is established to estimate different limit states and accurate behavior of jacket platforms against environmental wave loading. This novel approach which is called Incremental Wave Analysis (IWA) can be an appropriate substitute to current pushover practice. The IWA can take into account the effects of variation in wave height and wave-in-deck loading in the estimating of platforms' behavior. This paper aims to introduce the applications of this approach in deterministic assessment of offshore platforms, comprehensively. The IWA can estimate the collapse-prevention limit state of jacket platforms properly. In addition, an appropriate parameter for ultimate capacity of offshore platforms is introduced which is called Collapse Wave Height (CWH). It is illustrated that the CWH can be utilized as a substitute to RSR parameter in the design and assessment of jacket platforms. Moreover, this novel indicator is able to exceptionally estimate the collapse probability of offshore platforms utilizing a deterministic practice. This is a unique feature that can never be achieved by current pushover method utilizing RSR parameter. The IWA can be carried out using either nonlinear static or dynamic wave analyses. Therefore, in this paper, both Static and Dynamic Incremental Wave Analyses (SIWA and DIWA) will be systematically explained. Before conducting DIWA, some fundamental questions such as importance of dynamic analysis and also proper methodology for conducting dynamic analysis, will be investigated. Comparison between SIWA and DIWA will also bring about worthwhile results which will be discussed thoroughly.