Interaction of Ice Floes With Columns of a Semi-Submersible Platform

1983 ◽  
Vol 105 (4) ◽  
pp. 460-463
Author(s):  
P. G. Noble ◽  
D. Singh
Keyword(s):  
Maximum Load ◽  
Test Results ◽  
Ice Load ◽  
Physical Model Tests ◽  
Ice Concentration ◽  
Drilling Unit ◽  
Ice Loads ◽  
Ice Field ◽  
Preliminary Research ◽  
Ice Floes

A preliminary research project has been carried out to determine the effect of small ice floes on a semi-submersible drilling unit. Physical model tests have been conducted with two main objectives: first, to determine the ability of the columns to prevent ice from passing between them (arching) and thus minimizing the chance of riser damage, and second, to determine the total ice load on the semi-submersible during interaction with ice field concentrations. Three models were used, representing one half of a four, six or eight-legged semi-submersible platform. The dimensions and spacing of the columns were such that the heave and pitch responses were kept constant. The tests were conducted at a model scale of 1:30 using synthetic ice. Test results showed the maximum load measured on a four-legged semi-submersible model, at 100 percent ice floe concentration, was on the order of half of that measured on six or eight-legged semi-submersible models. Also the ice loads on a four-legged semi-submersible model at lower ice floe concentration were substantially less than those for six or eight-legged semi-submersible models. The total ice load on semi-submersible models is found to be a function of ice floe concentration. Up to about 75 percent ice concentration, ice loads varied linearly. Beyond that, the loads increased exponentially for all semi-submersible models.

Image Processing for the Analysis of an Evolving Broken-Ice Field in Model Testing

2012 ◽  
Author(s):  
Qin Zhang ◽  
Solange van der Werff ◽  
Ivan Metrikin ◽  
Sveinung Løset ◽  
Roger Skjetne
Keyword(s):  
Image Processing ◽  
Water Area ◽  
Test Results ◽  
Detection Algorithms ◽  
Ice Concentration ◽  
Broken Ice ◽  
Ice Field ◽  
Ice Floes ◽  
Processing Techniques ◽  
Ice Forces

Dynamic positioning (DP) experiments in model ice were carried out in the ice tank at the Hamburg Ship Model Basin (HSVA) in the summer of 2011. In these experiments the behavior of two different ships in a broken-ice field were studied. One of the main parameters characterizing a broken-ice field is the ice concentration, defined as the fraction of the total water area covered by ice. In this paper, image processing techniques are applied to derive the ice concentration in the model basin. Several points in time are analyzed in order to describe the evolution of the ice field. The applied techniques include methods for identifying individual ice floes and calculating the ice concentration in the vicinity of the model ship. Ice floe boundaries are then obtained, and the ice floe size distribution and shape factor may further be extracted from the images. The image processing methods applied in this work are object extraction and edge detection algorithms, which are further customized to ice identification. The obtained results can be used for relating the ice field characteristics to the model test results, such as the vessel’s displacements and the corresponding ice forces.

Laboratory Testing of a Flexible Boom for Ice Management

1993 ◽  
Vol 115 (3) ◽  
pp. 149-153 ◽  
Author(s):  
S. Lo̸set ◽  
G. W. Timco
Keyword(s):  
Oil Spills ◽  
The Arctic ◽  
Small Scale ◽  
Test Results ◽  
Offshore Structure ◽  
Video Cameras ◽  
Ice Concentration ◽  
Broken Ice ◽  
Ice Field ◽  
Force Components

Combatting oil spills in the Arctic is a major challenge. Drilling or producing oil or gas in the marginal ice zone (MIZ) may allow booms to be deployed upstream of an offshore structure to clear the water of ice, thereby enabling conventional oil spill countermeasures to be used. Such a boom would be kept in place by two ice-going service vessels or by moored buoys. SINTEF NHL and NRC have performed a number of small-scale tests with a flexible boom in the NRC ice basin in Ottawa. The purpose of the tests was to measure the effectiveness of using a flexible boom for collecting ice, and to determine the loads associated with collecting the ice. In the tests, various boom configurations were towed against a broken ice field consisting of ice pieces typically 50–100 mm across and 30 mm thick. The ice concentration was usually 10/10, but it was reduced to 8/10 and 5/10 for two tests. The boom was towed at speeds of 20 and 50 mm-s−1. Both the width of the boom and the slackness of the boom were varied over reasonable ranges. Two six-component dynamometers were used to support the boom. Thus, the force components on each end of the boom were measured. Further, two video cameras were used to record the effectiveness of each boom configuration. In this paper, the full results of this test program are presented and the application of the test results to the full-scale situation are discussed. The tests show that, under certain conditions, the use of boom is feasible for ice management in oil-contaminated water.

Influence of the Ice Concentration on the Ice Loads on the Hull of a Ship in a Managed Ice Field

2012 ◽  
Author(s):  
Solange van der Werff ◽  
Andrea Haase ◽  
René Huijsmans ◽  
Qin Zhang
Keyword(s):  
Development Project ◽  
Model Tests ◽  
Ice Thickness ◽  
Model Parameters ◽  
Dynamic Positioning ◽  
Ship Model ◽  
Ice Concentration ◽  
Ice Loads ◽  
Ice Field ◽  
Yaw Angle

The research and development project DYPIC (Dynamic Positioning in Ice) focuses on the challenges related to DP operations in Arctic environment. At the HSVA (Hamburg Ship Model Basin, Germany), model tests in ice were carried out using two configurations; one where the model was fixed to the towing carriage, and a free floating configuration, where the model ship was controlled by a DP system scaled to model parameters. During the model tests a number of parameters were systematically varied. Model ship velocity and yaw angle were the parameters related to the controlling of the model. In addition, the ice field characteristics were varied by applying two variations in ice floe size and two variations in concentration, resulting in four different ice field descriptions. The ice thickness was remained constant for all test implementations. Every test run with a particular controlling (velocity and heading) profile was executed in each of the four ice fields. In order to develop a DP controller which is optimally adjusted to the environment in which the system operates, it is important to find relations between the characteristics of the ice field and the forces they apply on the hull of the vessel or construction. An assessment of the measurements and observations during the testing is the basis of a study which has the objective to find how the ice field appearance and the ice loads on a structure relate to each other.

scholarly journals Influence of stirrup spacing on shear resistance and deformation of reinforced concrete beams

2018 ◽  
Vol 7 (1) ◽  
pp. 126
Author(s):  
Latha M S ◽  
Revanasiddappa M ◽  
Naveen Kumar B M
Keyword(s):  
Concrete Beam ◽  
Concrete Beams ◽  
Bending Moment ◽  
Maximum Load ◽  
Reinforced Concrete Beams ◽  
Test Results ◽  
Cement Concrete ◽  
Simply Supported ◽  
Reinforced Cement ◽  
Flexural Reinforcement

An experimental investigation was carried out to study shear carrying capacity and ultimate flexural moment of reinforced cement concrete beam. Two series of simply supported beams were prepared by varying diameter and spacing of shear and flexural reinforcement. Beams of cross section 230 mm X 300 mm and length of 2000 mm. During testing, maximum load, first crack load, deflection of beams were recorded. Test results indicated that decreasing shear spacing and decreasing its diameter resulted in decrease in deflection of beam and increase in bending moment and shear force of beam.

Station Keeping Trials in Ice: Ice Load Monitoring System

2018 ◽  
Author(s):  
Håvard Nyseth ◽  
Anders Hansson ◽  
Johan Johansson Iseskär
Keyword(s):  
Data Sets ◽  
Station Keeping ◽  
Ice Load ◽  
Hull Structure ◽  
Load Monitoring ◽  
Ice Loads ◽  
Recorded Data ◽  
Measurement Concept ◽  
Ice Impacts ◽  
Basic Philosophy

In connection with the Statoil SKT project, DNV GL have developed a method for estimating ice loads on the ship hull structure and mooring tension of the anchor handling tug supply (AHTS) vessel Magne Viking by full scale measurements. In March 2017, the vessel was equipped with an extensive measurement system as a preparation for the dedicated station-keeping trial in drifting ice in the Bay of Bothnia. Data of the ice impacts acting on the hull were collected over the days of testing together with several other parameters from the ship propulsion system. Whilst moored, the tension in the mooring chain was monitored via a load cell and logged simultaneously to the other parameters. This paper presents the processes involved in developing the measurement concept, including the actual installation and execution phases. The basic philosophy behind the system is described, including the methods used to design an effective measurement arrangement, and develop procedures for estimation of ice loads based on strain measurements. The actual installation and the process of obtaining the recorded data sets are also discussed.

scholarly journals Study on the Water-Physical Properties of the Cement-Plaster Bonded Rock-Like Materials

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Yong Zhang ◽  
Zhiguo Cao ◽  
Xiaomeng Shi
Keyword(s):  
Physical Properties ◽  
Physical Model ◽  
Coupling Model ◽  
Model Tests ◽  
Physical Parameters ◽  
Test Results ◽  
Physical Model Tests ◽  
Fluid Coupling ◽  
Softening Coefficient ◽  
Solid Fluid Coupling

The cement-plaster bonded rock-like material is one of the most commonly used materials to simulate different rocks in physical model tests. However, the applicability of this material in solid-fluid coupling model tests is not clear because there are few research studies on the water-physical properties of this material and its similarity to the actual rock is uncertain. This paper presents a systemic experimental study on the water-physical properties of the cement-plaster bonded rock-like materials. The parameters of rock-like materials, including water absorption, softening coefficient, and permeability coefficient, were compared with those of actual rocks to analyse the applicability of such material. Then, the influence of proportion on the water-physical properties of this material was discussed. By multiple regression analysis of the test results, empirical equations between the water-physical parameters and proportions were proposed. The equations can be used to estimate the water-physical properties of cement-plaster bonded rock-like materials with specific proportion and thus to select suitable materials in the solid-fluid coupling physical model tests.

Research on the Influences of Broken Ice Parameters on Maneuverable Forces of Ice-Going Ship Oblique Sailing

2021 ◽  
Author(s):  
Shenyu Xuan ◽  
Chengsheng Zhan ◽  
Zuyuan Liu ◽  
Binfeng He ◽  
Qiaosheng Zhao ◽  
...  
Keyword(s):  
Time History ◽  
Test Results ◽  
Ship Maneuvering ◽  
Average Value ◽  
Ocean Science ◽  
Broken Ice ◽  
Ice Conditions ◽  
Ice Field ◽  
Ice Resistance ◽  
Good Agreement

Abstract The broken ice is one of the most common ice conditions for ice-going ships, and the research of ship maneuvering movement in broken ice field can improve sailing safety. In this paper, the discrete element method (DEM) was adopted to study the maneuverable forces, including resistance and transverse force, of ice-going ship oblique sailing in broken ice fields. First, the Araon model tests data of Korea Institute of Ocean Science & Technology (KIOST) was used to verify the ice resistance of direct sailing under different ice sizes and model speeds, and the numerical results are in good agreement with the test results. Second, the influences of broken ice parameters (including concentration, thickness, and shape) on ship-ice interaction and maneuverable forces distribution were researched. The maneuverable forces on the ice-going ships are mainly from the ship-ice interaction. The time history curves of maneuverable forces were analyzed from the average value of maneuverable forces, the average value of peak maneuverable forces, and the number of peaks. Besides, the parameters of broken ice have a heavy influence on the movement of broken ice around the hull, such as accumulating and sliding. The analysis of the broken ice movement contributes to understanding the influences of broken ice parameters on ice-going ships.

scholarly journals Simulation of Ice-Propeller Collision with Cohesive Element Method

2019 ◽  
Vol 7 (10) ◽  
pp. 349 ◽  
Author(s):  
Zhou ◽  
Wang ◽  
Diao ◽  
Ding ◽  
Yu ◽  
...  
Keyword(s):  
Rotational Speed ◽  
Constitutive Law ◽  
Impact Loads ◽  
Cohesive Element ◽  
Ice Loads ◽  
Ice Floes ◽  
The Time Domain ◽  
Contact Position ◽  
The Impact ◽  
Element Method

The existence of ice in ice-covered waters may cause damage to the propeller of polar ships, especially when massive ice floes are submerged around the hull. This paper aims to simulate an interaction process of a direct ice collision with a propeller based on the cohesive element method. A constitutive law is applied to model the ice material. The model of ice material is validated against model test results. The resulting impact loads acting on the contact surfaces and the corresponding ice block velocity are calculated in the time domain. The ice crushing, shearing and fracture failures are reproduced in the simulation. The convergence study with three meshing sizes of ice block is performed. To carry out a parametric study, five parameters are selected for analysis. These parameters are composed of rotational speed, direction of the propeller, initial speed of the ice block, contact position, and area between the ice and the propeller. The results show that the ice loads are affected by the five factors significantly. Ice loads tend to increase by decreasing the rotational speed, increasing the initial ice speed and the contact area, and changing the rotational direction from clockwise to counterclockwise. The effect of the contact position on the impact loads is relatively complex, depending on rotational speeds of the propeller.

Reliability Against Drifting Ice—An Adjunct to Monte Carlo Simulation

1991 ◽  
Vol 113 (3) ◽  
pp. 253-259
Author(s):  
A. B. Dunwoody
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Normal Family ◽  
Probability Distributions ◽  
Load Model ◽  
Ice Load ◽  
Ice Loads ◽  
Drifting Ice ◽  
Log Normal ◽  
Monte Carlo Simulation Program

A method is presented for the calculation of the reliability of a structure against drifting ice subject to restrictions on the form of the ice load model and on the form of the probability distributions of the ice feature characteristics. The ice load model must have the form that the ice load is proportional to the product of the characteristics of the impacting ice feature raised to individual powers. Results from a Monte Carlo simulation program are presented to demonstrate that the ice loads for a number of useful ice interaction scenarios can be modeled by an equation of this form. The probability distributions of the ice feature characteristics must be from the log-normal family. A realistic example using publicly available ice data and ice load model is presented.

Guidance Model Representing an Ice Field for Path-Planning in Ice Management

2020 ◽  
Author(s):  
Jon Bjørnø ◽  
Mathias Marley ◽  
Roger Skjetne
Keyword(s):  
Path Planning ◽  
Breaking Effect ◽  
B Splines ◽  
Planning Algorithm ◽  
Broken Ice ◽  
Ice Field ◽  
Ice Floes ◽  
Path Planning Algorithm ◽  
Guidance Information ◽  
Guidance Model

Abstract In the work presented in this paper, the problem on how to represent a simplified ice field in a guidance model, enabling path and maneuver planning for IM operation, has been studied. The use of B-splines and other basis functions are considered to represent relevant guidance information over the 2D drifting ice field. A weight value is computed and updated at locations that represents broken ice (visited by an icebreaker) versus unbroken ice. The guidance model will ensure that there is a continuous representation of the state of the ice field during the operations. The drifting behavior of the ice field is incorporated into the guidance model. The model will be updated with new (solid) ice that is formed at the beginning of the ice field, and it will continuously be updated in the path where the icebreaker moves. To simulate the maneuvers of the icebreaker, a dynamic model is used, and the ice breaking effect where the ice field is continuously broken into smaller ice floes is included in the model. This representation of an ice field can be used in a path-planning algorithm to determine the icebreaker path in a moving ice environment in order to reduce the ice field into small enough ice floes and reduce the load on the protected structure.

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