Structures vibration induced by ice action

Ice induced vibration of fixed offshore structures has been observed in different seas, for example, Beaufort Sea, Cook Inlet, Gulf of Bothnia, Bohai Gulf, Sea of Okhotsk, Caspian Sea. It can have a significant impact, as it may lead to failure due to structural fatigue (Bohai Gulf) or softening foundations, or cause problems with the serviceability of platforms. The experimental works have been conducted for a long time and give results which can be used only for conditions corresponding to the experiment. Moreover, approximate analytical solutions have a limited area of application, because of complexity of the phenomenon. A 2D solution for the numerical study of ice-induced vibration of vertical-sided fixed offshore structures based upon the discrete elements method has been developed by Saint Petersburg State Polytechnical University. The results of the comprehensive numerical analysis have been presented by authors to determine the main parameters of the environment and construction which influence the phenomenon

An overview of ice loads on structures

Ice of many forms grows annually on rivers, lakes and the sea, and as a consequence can interact with hydrotechnical or coastal structures, generating forces on them. These forces must be appropriately assessed and accounted for in the design of structures in water bodies affected by ice. Ice conditions such as thickness, strength, morphology and floe size influence ice forces and must be characterized and suitable extreme values of these features determined. The environmental driving forces of wind, current and temperature must also be understood. Information on ice conditions and environmental factors are combined to provide guidance on calculating the magnitude of ice forces that a structure might be expected to withstand over its lifetime. Various national and international standards and codes that provide guidance on ice forces have been introduced and a high level overview of determining ice loads provided. Areas that would benefit from further research include; investigation of compressive strength of ice for rates greater than 10-3 s-1, the relation between rate effects in laboratory tests and rate in ice loading of structures, and analytical work to implement ice constitutive relations into the nonuniform stress states of ice indentation.Peer reviewed: YesNRC publication: Ye

On borehole indentor (BHI) measurements and analysis

In situ measurements on stress\u2013indentation curves conducted with the National Research Council (NRC), Canada and the Arctic and Antarctic Research Institute (ARRI), Russia borehole indentors (BHI) are analyzed and classified. This establishes harmony with laboratory observations on stress\u2013strain diagrams and some compatibility with the recommendations (ISO/DIS 19906) on estimating uniaxial ice strengths from BHI strengths. The analysis is devoted mainly to consider the influence of local ice conditions and the indentation rates on the pressure\u2013indentation curves. Simultaneous records of the acoustic emission (AE) detected by accelerometers installed on the ice surface, within 1.5 m of the indentation plate, indicated that major cracks are nucleated at the ice/plate interface. Microstructural analysis of the indented ice confirmed this important conclusion in addition to revealing recrystallization as well as healing activities in the indented ice. An attempt, with extremely limited success, has been made in applying conventional ice failure criteria for predicting the observed stress\u2013indentation curves. Phenomenologically, however, a power-law between the indentation-rate and upper-yield strength exhibits the same rate sensitivity (about 3) usually obtained for strain-rate dependence of uniaxial strengths. Numerical solutions of the rate-sensitive indentation processes must be developed (as has successfully been achieved for uniaxial tests) on microstructure-property based mathematical (rheological) model that includes the effects of the rate-dependent kinetics of deformation, microcracking and crack-enhanced creep. Premature brittle fractures are contact problems and modeling must consider the nucleation of cracks in ice at the ice/plate contact surface.Peer reviewed: YesNRC publication: Ye

An overview of ice loads on structures

Ice of many forms grows annually on rivers, lakes and the sea, and as a consequence can interact with hydrotechnical or coastal structures, generating forces on them. These forces must be appropriately assessed and accounted for in the design of structures in water bodies affected by ice. Ice conditions such as thickness, strength, morphology and floe size influence ice forces and must be characterized and suitable extreme values of these features determined. The environmental driving forces of wind, current and temperature must also be understood. Information on ice conditions and environmental factors are combined to provide guidance on calculating the magnitude of ice forces that a structure might be expected to withstand over its lifetime. Various national and international standards and codes that provide guidance on ice forces have been introduced and a high level overview of determining ice loads provided. Areas that would benefit from further research include; investigation of compressive strength of ice for rates greater than 10-3 s-1, the relation between rate effects in laboratory tests and rate in ice loading of structures, and analytical work to implement ice constitutive relations into the nonuniform stress states of ice indentation.Peer reviewed: YesNRC publication: Ye

Neuroendocrine influences in psychoimmunology and neoplasia: A review

Much recent work has focused on the interrelationships among environmental. psychological and physiological phenomena involved in immune-related disorders. with special emphasis being given to neoplastic processes. The present review looks first at the physiological pathways involved in the body's assorted and alternating responses to stressful environmental and psychological conditions and the immune system sequelae following each of two distinct psychophysiological coping responses-active coping and passive coping/helplessness reaction. Psychoimmunological findings about stressful life events. bereavement and mental depression as stressors the integrated with current psychoneuroimmunological postulates. A framework is outlined that may have utility for understanding the relationship among chronic psychological emotional stress in its many forms, accompanying neurohormonal changes. and increased susceptibility to immune-mediated neoplastic growth. Finally, the recently evolved concepts of hyper-adaptosis and cancrophilia are employed to further integrate theoretical pathways with clinical findings in the hopes of presenting a fertile base on which others may plan and conduct empirical research and intervention strategies