Split-time method for estimation of probability of capsizing caused by pure loss of stability

Abstract

The paper reviews a multi-year research effort for using the split-time method to calculate the probability of ship capsizing due to pure loss of stability in irregular waves. The idea of the splittime method is to separate the complex problem into two less complex problems: a non-rare problem that involves the upcrossing of an intermediate level of roll and a rare problem that focuses on capsizing after an upcrossing. An initial implementation using a dynamic model with piecewise linear stiffness, which can be considered to be the simplest model of capsizing in beam seas, led to the concept of critical roll rate as the smallest roll rate at the instant of upcrossing that inevitably leads to capsizing. The extension of the split-time method to pure loss of stability required the consideration of the change of roll stiffness in waves and led to calculating the critical roll rate at each upcrossing. A metric of the likelihood of capsizing has been defined as the difference between the observed and critical roll rate at the instances of upcrossing. The probability of capsizing after upcrossing is found by approximating the tail with the Generalized Pareto Distribution.

Numerical study of extreme mechanical force exerted by a turbulent flow on a bluff body by direct and rare-event sampling techniques

“…Several authors have proposed original strategies (Mohamad & Sapsis 2018;Blonigan, Farazmand & Sapsis 2019) such as sequential sampling. These approaches and rare-event algorithms could also be considered for applications in wave-structure problems, ship motion and loads acting on offshore platforms (Belenky, Weems & Lin 2016). The paper is organized in two parts.…”

An overview of the current research on stability of ships and ocean vehicles: The STAB2018 perspective

“…Broaching zones are estimated, however the issue of their utilisation in real wave environment remains open. Belenky et al (2016aBelenky et al ( , 2016b use the concept of split-time method for the estimation of the probability of surf-riding and capsize due to pure loss of stability in irregular waves. By this concept, two problems are set: non-rare and rare, where a metric of the danger of the rare event is defined and computed utilising data from the non-rare problem (exceedances of an intermediate threshold) and statistical extrapolation techniques.…”

A Unified Numerical Method for Broaching and Loss of Stability in Astern Seas

“…It is also reported that the loss of stability numerical simulated by the code LAMP is used for evaluating the capsizing probability in random seas with a split-time method. However, its time-domain approach ignores the effect of the surge, sway, yaw, and rudder [26].…”