Author(s): S. H. Iyer
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Abstract: Ice forces on structures occur in two basic forms, static and dynamic. Among static loads, ice pressures due to thermal thrust are the most significant. Dynamic loads are caused by the impact of floating ice at breakup. The common structures subject to ice actions are concrete dams, light piers, bridge piers, conical piers, drilling and production platforms, and various other marine structures. The designer of these structures is faced with the problem of selecting appropriate values for ice pressures under various conditions. Currently, there are no well-established codes or standards to which the designer can refer for ice action under most of the commonlyoccurring ice conditions. Among the existing codes, the important ones are due to Korzhavin, USSR-SN 76, CSA old highway code, CSA-S6.74 and the design practices of the Canadian Ministry of Transport and Lighthouses, Canadian Department of Public Works and those of Sweden and Finland. Most of these are quite recent in origin and have been developed to cover specific situations. Considerable disparity is noted in the results obtained by using these codes and design practices. Little guidance is given for statistical variability of ice properties, force fluctuations due to structural vibrations, velocity of ice floes, etc. The present codes do not refer to conical structures explicitly. For this paper, FENCO CONSULTANTS LTD. has made an attempt to overcome some of the above-mentioned limitations by considering such factors as nature and mechanism of ice thrust, ice failure processes, effects of aspect ratio, characteristic peaks during dynamic impacts, moving ice pack with unconsolidated floes, unconsolidated and consolidated pressure ridges, etc. In establishing these guidelines. reference has been made to the vast in-house sources of information gathered from ice-related projects carried out by FENCO over a period of years as well as the published information of others. A table giving the values of ice pressures to be used for freshwater ice and sea ice under various conditions has been presented. The theoretical bases underlying these guidelines have been discussed. The concept of energy, i. e. energy to break up a unit volume of ice, is introduced as this directly represents the time average pressure due to ice action. Good agreement is observed between the tabulated values and the test results.
Year: 1978