engleski

PROBABILISTIC COMBINATION OF WAVE AND WHIPPING BENDING MOMENTS ON SHIP STRUCTURE

A commonly used structural reliability formulation for tankers and bulk carriers is extended to include whipping effects. Procedures for the short-term and the long-term prediction of wave- induced and whipping bending moments are developed. The problem is formulated in the frequency domain using standard engineering tools for the load computation: a seakeeping code for the rigid-body response and a beam finite element model for the transient vibratory response. The von Karman approach with correction for the pile- up effect is employed for the bow flare slamming load assessment. The influence of operational and environmental uncertainties is taken into account considering different shipping routes, heavy weather avoidance and heavy weather manoeuvring. Afterwards, three types of correlations between wave and whipping bending moments are elaborated. The short-term load combination factors are derived based on a large number of time signal reconstructions from the frequency domain. These results are then evaluated by comparison with TULCS model test data of the Rigoletto container ship for available sea states and operating conditions. Based on the derived results the regression equations for estimation of the most probable short-term load combination factor are formulated. Several suggestions for the long-term prediction of the partially correlated combined bending moment and consequently the long-term load combination factor are provided. The developed procedure is applied for the structural reliability assessment of two large container ships. Finally, conclusions are drawn and guidelines for further research are given.

Bow flare slamming; Container ship; Fast Fourier transformation; Load combinations; Operational and environmental uncertainties; Spectral analysis Structural reliability analysis; Ultimate limit state; Vertical wave bending moments; Whipping bending moments

Rad je pisan kao međunarodni dvojni doktorat (COTUTELLE) u suradnji s Instituto Superior Tecnico, Tehničkim Sveučilištem iz Lisabona.