|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
Akagawa, Satoshi (Shimizu Corporation) | Nakazawa, Naoki (Forest Works Inc.) | Sakai, Masafumi (Taisei Corporation) | Matsushita, Hisao (Nippon Kaiji Kyokai) | Terashima, Takashi (Pacific Consultants) | Takeuchi, Takahiro (Hachinohe Institute of Technology) | Saeki, Hiroshi (Hokkaido University)
ABSTRACT This paper demonstrates how to utilize 2D ice pressure data obtained by Akagawa et al. 1999. This data has been obtained through a series of field experiments conducted in the harbor of Notoro Lake near Abashiri-city on Okotuku shoreline with medium scale indentation test system (Nakazawa et al. 1999). We havd presented 2D ice pressure data visualizing the change of ice pressure distributions during the indentation tests in previous papers, such as Sodhi et al. 1998. Utilizing the 2D ice pressure data, a preliminary study on the mechanism of continuos ice pressure generation during ice indentation tests is described in this paper. Analyzing the correlation between the peak ice load ofa continuos ice load time-series record and 2D ice pressure distributions, ice failure modes are discussed to identify what kind of failure will predominantly contribute to a specific peak ice load observed during continuos sheet ice crushing. The 2D ice pressure data supports the concepts of line-like loading (Joensuu and Riska, 1989) and independent failure zones (Takeuehi et al. 1999) previously observed at indentation velocities of 30mm/sec. Furthermore, the 2D ice pressure data suggests that the peak ice load is caused predominantly by the flaking during brittle failure. INTRODUCTION It is well known that ice behaves in both ductile and brittle manners. Recent work on these behaviors have been summarized by Sodhi et al., 1998. This paper will combine the work on brittle failure and the independent failure zone concept actively studied by many scientists and engineers to the scale-effect of indentor size on ice pressure. A series of medium scale field indentation tests have been conducted by the authors in Notoro-lake Hokkaido, in order to observe the scale effect on ice pressure for different size ofindentors.
ABSTRACT A new computer model has been developed for evaluating the dynamic ice-structure interaction. The effects of soil-structure interaction are included in the model. The program can be used in the analysis of events where an offshore structure is subjected to the action of drifting ice sheets or massive ice features like an iceberg. The program is based on a substructure technique where separate equations are set up for each of the interacting medium. A zonal approach is applied while modelling the ice failure processes. Hence, the effects of nonsimultaneous crushing are considered. 1 INTRODUCTION Dynamic ice loads are generated when a drifting ice floe or an iceberg impacts against an offshore structure. Generally, slender structures exhibit a dynamic behaviour that must be considered in the design. A soft foundation and high drifting velocities of the ice floes lead to a similar situation. The most commonly observed form of interaction between an ice floe and structure can be characterized as quasi-static. In this case the ice crushes intermittently and causes transient vibrations which decay before the next event of ice crushing. Occasionally, also sustained ice induced vibrations have been measured. A high amplification of the dynamic response is generated in these cases. A large number of studies on the subject have been published over the past few years, building upon the pioneering research work by Miiiittlinen (1978). Ice-induced vibrations were observed in small-scale tests conducted by Toyama et al. (1983). The same phenomenon was observed also in full-scale by Nordlund, Kama and Jarvinen (1988). A numerical model and all associated simplified approach for narrow structures were developed by Kama and Turunen (1989, 1990). The most recent development includes laboratory tests conducted by Joensuu & Riska (1989), Sodhi (1989) and Kama & Muhonen (1990).