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Results
Model Experiments For Ice Forces On Multi Conical Legged Structures
Kato, K. (Ishikawajima-Harima Heavy Industries, Co., Ltd.) | Adachi, M. (Ishikawajima-Harima Heavy Industries, Co., Ltd.) | Kishimoto, H. (Ishikawajima-Harima Heavy Industries, Co., Ltd.) | Hayashiguchi, S. (Ishikawajima-Harima Heavy Industries, Co., Ltd.)
ABSTRACT Model experiments for multi-legged structures with a conical column belt on each leg at the waterline (MCLS) were performed. Two types of MCLS, namely UB-MCLS and DB-MCLS were tested in IHI Ice Model Tank. The experiments were performed taking the intrusion angle as a testing parameter and six force components were measured. In the experiments, the ice force and the ice-induced overturning and twisting moments revealed its maximum at the intrusion angle of 30 deg. And in normalized fashion, the ice force and the ice-induced moments for DB-MCLS were twice as large as those for UB-MCLS. However, the magnitudes of those quantities were approximately the same for both DB-MCLS and UB-MCLS. The method to estimate an ice force on UBMCLS was introduced. Also the simplified method to estimate a first step ice force on UB-MCLS was also presented. INTRODUCTION A multi legged structure is an arctic structure which supports its superstructure by plural number of legs in various types. This structural type does not seem to be sui table for heavily ice covered seas like Beaufort Sea. However, when an ice condition is not heavy, it would be one of the most economical type. Thus quite a few number of structures of this type would be employed for developing natural resources in the regions such as the coast of Sakhalin and Bohai Bay. Two types of multi legged structures are considered. The first one is a multi vertical legged structure (MVLS in short), which supports its superstructure by plural number of vertical circular legs. The other is a multi conical legged structure (MCLS in short), which supports its superstructure by plural number of vertical legs with a conical shaped column belt at the water line on each leg. The authors have investigated how to estimate a total ice forces on this kind of arctic structures (for instance, Kato, 1990).
- Asia > Japan (0.28)
- Asia > Russia > Far Eastern Federal District > Sakhalin Oblast (0.24)
ABSTRACT A numerical method is developed to estimate ice loads which are mainly depend on the failure behavior of ice, and experiments are carried out to examine the validity of it. It uses a thick walled shell element based on the concept of the Rigid Bodies-Spring Models. It is equipped with functions in order to deal with characteristics of ice, such as material and geometrical nonlinearities, variations of material properties through thickness, buoyancy effects, and stiffness reduction due to cracking behavior. The verification tests of this method are carried out in the IHI ice tank on both level ice sheets and composite ice features including a model ice ridge, and make evident a good agreement between experimental results and simulation results. INTRODUCTION Many efforts have been paid to estimate ice loads acting on ice breakers and offshore arctic structures by field measurements, model tests mice tanks(Kato,1986) and numerical analyses (Watanabe and Kawai, 1980; Yoshimura and Kamesaki, 1981; Shibata, Kumakura and Matsushima, 1983). Precise results are obtained by field measurement methods, but they involve high costs. Well-designed experimental studies can also be performed in ice tanks, owing to the uniform ity and the reproducibility of model ices. However, there are limitations in range of mechanical properties of model ice. Numerical analysis are useful for the estimation of ice loads, and they can handle critical mechanical properties of ice which are not available in model tests. The critical difficulties in estimation of ice loads by numerical analysis come from the complexity of mechanical properties of ice. That is the reason why the mechanical properties of ice sheet and a suitable calculation model for representing its characteristics are necessary. This paper presents a numerical simulation code which is developed for the estimation of Ice loads, and the verification of the code.