SAMCoT - Annual Report 2015

SAMC

• ANNUAL REPORT 2015

Local ice actions

A proper understanding of local ice actions and action

effects is important in the design of ships and offshore

structures. Local, in this respect, means that loads on a

contact area are typically of size 1 m

, but in general are

determined by the structural arrangement. Depending on

the local contact conditions such as shape of the structure,

ability to deform etc., the local ice action will vary. Here

SAMCoT’s research efforts focused on the following topics:

Fluid-Structure Interaction, analysis of ice-structure colli-

sions; Understanding of local ice actions on ships and

offshore structures and Validation of SPH based approach

to fracture of ice.

Application to ultimate limit state design

(little or no plastic deformations)

In order to bridge the gap between local ice loads used for

the design of ice-going vessels and offshore structures,

analysis of the International Association of Classification

Societies Ltd. Polar Class (IACS PC) and Russian Maritime

been performed. A summary of the analysis can be

found in the 23rd International Conference POAC`15

paper “Understanding the effect of assumptions on shell

plate thickness for Arctic ships”. In addition, the detailed

analysis, including derivations of the rule formulae and

uncertainty quantifications, has been published in the

International Journal of Ocean Engineering (see paper

“Discussion of assumptions behind rule-based ice loads

due ice crushing”). Results from this study have been

used to extend the ice failure maps developed earlier by

Dr Lu. Solutions for localized ice edge crushing have been

added to theoretically different fracture patterns (see the

POAC15 paper “Toward a holistic load model for structures

in broken ice”). The updated ice failure map is shown in

Figure WP4_11 and is based on observations of ice failure

in contact with floating ship-shaped structures in level ice

and in low ice concentrations.

Application to accidental limit state design

(significant plastic deformations)

Within the context of local ice loads due to an abnormal ice

event, our group has been addressing two effects: the effect

of structural deformations (coupled ice-structure interac-

tion during an impact event) and the effect of surrounding

water (hydrodynamic interaction effects).

Coupled ice-structure interaction

Results of ice and structure collision experiments, where

both the ice and the impacted structure undergo perma-

nent damage, have been presented at POAC15; for detailed

information refer to the paper entitled “Pilot study of

ice-structure interaction in a pendulum accelerator”. We

highlight that further investigations of this coupled inter-

action are vital to improve the understanding of ice loads

in a realistic impact scenario and to establish additional

requirements to limit catastrophic damage to vessels with

design loads with high probabilities (less than a 100 year

return period).

Hydrodynamic interaction effects

In the analysis of ice-vessel collisions, hydrodynamic

effects from the surrounding water may also be important

because they affect the motions of the ice and the vessel

before and after the collision (e.g. see Figure WP4_12).

Figure WP4_10. The probability of level ice breaking at a specific length while interacting with a downward-sloping rigid structure

shown at various interaction speeds. The right graph includes hydrodynamics and the left graph does not. Blue indicates a high

probability.

Figure WP4_12. The probability of the level ice breakin at a specific length while interacting w th a

downward sloping rigid structure shown at various interaction speeds. The right graph includes

hydrodynamics and the right graph does not. Blue indicates a high probability.

Local ice actions:

A proper understanding of local ice actions and action effects are important in design of ships and

offshore structures. Local in this respect means loads on a contact area typically of size 1 m

or so,

but in general determined by t e structural arrangement. Depending on the local contact conditions

such as shape of the structure, ability to deform etc., the local ice action will vary. Here SAMCoT’s

research efforts focused on the items illustrated in Figure WP4_20.

Figure WP4_20. Illustration of items being studied for a better understanding of local ice actions.

Fluid-Structure

Interaction

analysis of ice-

structure

collisions

Understandi g

of local ice

actions

on ships

and offshore

structures

Validation

of SPH

based approach

to fracture of ice

Figure WP4_12. The probab lity of the level ic breaking at a specific lengt while interacting with a

downward slopin rigid structure shown t various interaction speeds. The right graph includes

hy rodynamics and the ri ht graph does not. Blue indicates a igh probability.

Local ice actions:

A roper understa ding f local ice actions and action effects are importa t in design of ships and

offshore structures. Local in thi r spect means loads on a con ct area typically of size 1 m

r so,

but i general determined by the str ct ral arrang ment. Depe ding on the lo al con act conditions

such as shape of the str cture, ability to d form etc., the local ice action will vary. Here SAMCoT’s

research efforts focused on th items illustrated n Figure WP4_20.

Figure WP4_20. Illustrati n of items being stu ied for a b tter understa ding f lo al ice actions.