Loads on an Off-Shore Structure due to an Ice Floe Impact

• Main Author: Ryszard Staroszczyk
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2006
• Subjects: Ice Sheet
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.540.6091; http://www.ibwpan.gda.pl/docs/ahem/ahem54str077.pdf

In the paper, the problem of dynamic impact of a floating ice sheet at an off-shore structure is considered. It is assumed that during an interaction event the dominant mechanism is the brittle fracture of ice at the ice–structure interface, that is, elastic and creep effects in ice are ignored. Since in natural conditions the edge of floating ice is usually irregular, the contact between a floe and an engineering object is imperfect. Thus, at any one time, the failure of ice occurs only in a number of small zones along a structure wall, leading to a highly irregular variation of forces exerted on the structure during the impact process. It is supposed in the analysis that the successive small-scale fracture events at the contact surface occur at random, and all these small-scale events take place independently of each other. An off-shore structure is modelled as a fixed and rigid circular cylinder with vertical walls. For an adopted geometry of the ice sheet, its initial horizontal velocity, and the variety of parameters describing the limit failure stresses in ice, the history of total loads sustained by the structure and the floe velocity variation are illustrated for a typical impact event. Furthermore, probability distributions for maximum impact forces exerted on the structure, depending on the floe size, its thickness and initial velocity, are determined. Key words: floating ice, off-shore structure, dynamic impact, brittle fracture Notations A, A0 – ice–structure contact area, reference area, b – discrete ice element size, Fx, Fy – components of total force sustained by a structure, h – ice floe thickness, m – floe mass, r0,R0 – cylinder radius, floe radius, t – time, v – floe velocity, V0 – initial floe velocity, x – ice penetration distance, β – ice fracture strength scale dependance parameter, 78 R. Staroszczyk ∆ – critical displacement, ε f – critical failure strain, σc – ice clearing stress, σ f – ice failure stress, σ∗f – normalized ice fracture strength. 1.