Impact scenario models for probabilistic risk-based design for ship–ship collision Kaarle Ståhlberg a , Floris Goerlandt a, * , Sören Ehlers b , Pentti Kujala a a Aalto University, School of Engineering, Department of Applied Mechanics, Marine Technology, Research Group on Maritime Risk and Safety, P.O. Box 15300, FI-00076 AALTO, Espoo, Finland b Norwegian University of Science and Technology, Department of Marine Technology, Otto Nielsens vei 10, 7491 Trondheim, Norway article info Article history: Received 30 April 2013 Received in revised form 27 May 2013 Accepted 29 June 2013 Keywords: Risk-based design Probabilistic damage assessment Ship–Ship collision Impact scenario abstract A number of authors have proposed probabilistic risk based ship design for ship–ship collision, conditional to the local trading area of a vessel. The probability of collision and consequences are deter- mined based on the traffic conditions in which a vessel is expected to operate. This paper investigates the adequacy of currently avail- able models for impact scenarios, i.e. models linking the traffic conditions to the conditions at the moment of collision. An explor- atory statistical model is presented to establish such a link. A probabilistic risk based design case study is performed for a fleet of RoPax vessels trading on a specified route in the Gulf of Finland. The available impact scenario models from the literature are compared with the developed probabilistic evasive maneuvering model. The results show that the impact scenario models have a very significant influence to the calculated hull breach probabilities. No well- justified impact scenario models are presently available and also the presented probabilistic evasive maneuvering model is burdened with uncertainty. Hence, to move toward a probabilistic risk based ship design paradigm for ship–ship collision in a local trading area, more focus and research is needed to establish a credible link. Ó 2013 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: þ358 9 470 23476; fax: þ358 9 470 23493. E-mail address: floris.goerlandt@aalto.fi (F. Goerlandt). Contents lists available at SciVerse ScienceDirect Marine Structures journal homepage: www.elsevier.com/locate/ marstruc 0951-8339/$ – see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.marstruc.2013.06.006 Marine Structures 33 (2013) 238–264