Irina Sæther - Academia.edu (original) (raw)
Papers by Irina Sæther
Digital temperature sensors provide an attractive means to conveniently record ice and water temp... more Digital temperature sensors provide an attractive means to conveniently record ice and water temperatures in remote locations. Unlike conventional analogue techniques, a digital sensor performs a physical measurement, interprets its result in terms of temperature and transmits that result to a logger or display system in digital form. Processing of digital signals is comparatively robust and cheap. Custom calibration may be applied to increase measurement accuracy. A popular example of a digital temperature sensor is the Maxim Integrated DS18B20, which is readily available as a bare sensor in a standard transistor casing, or from third-part providers as a probe with the sensor encased in a waterproofed metal sleeve. We found that the quality of water protection of the probes varies widely, and that bare sensors and sensors in probes offered by most third-party providers (i.e. not by official distributors) are almost always clones, i.e. not produced by Maxim Integrated. We summarize in this paper the spectrum of counterfeit sensors currently available and how they differ from authentic parts and specifications in the Maxim Integrated data sheet. Currently sold sensors are grouped into 7 families, 6 of them representing counterfeits. Awareness of the prevalence and characteristics of counterfeit sensors will help avoid surprises during costly experimental field work.
The present report deals with corrosion of steel reinforcement which is the principal cause of de... more The present report deals with corrosion of steel reinforcement which is the principal cause of deterioration of reinforced concrete infrastructure. Previous research on steelbar corrosion has mainly been devoted to the causes and mechanisms of corrosionwhile relatively little attention has been given to the problem of assessing the residual strength of corroded structures. The objective of the present report is to investigate the effects of steel bar corrosion on structural performance. In the first phase of this research, a comprehensive evaluation was carried out based on published laboratory testdata on corrosion of steel bars in concrete, see Appendix D. In the second phase, experimental research was conducted to investigate the effects of steel bar corrosion, using both specimens collected from the field (30 years exposure) and standard specimenscast in the laboratory. The experimental data from the present research is used todevelop methods for assessment of the structural consequences of reinforcement corr osionEC Sixth Framework ProgramSustainable Bridges – Assessment for Future Traffic Demands and Longer LivesTIP3-CT-2003-001653</p
IAHR / NTNU, Nov 1, 2020
Ice loads on a concrete dam have been calculated from stress measurements in Taraldsvikfossen Res... more Ice loads on a concrete dam have been calculated from stress measurements in Taraldsvikfossen Reservoir, a small reservoir in Narvik, Norway, during three winter seasons. Ice thickness was in the range of 0.5 to 1.0 m, and both thermal ice loads were observed and water level fluctuations up to 30 cm were observed when the ice cover froze to the spillway. The maximum global line load measured was 60 to 90 kN/m, in line with current design guidelines in Norway. Consistent with earlier reports, line loads were not evenly distributed along the dam face. A thermal line load model was able to reproduce the approximate shape and magnitude of many line load peaks even when the measured vertical stress profile could not be reproduced by the model. The result add to an extremely small body of data in Norway and motivate investigations in other pars of the country with expected higher or lower ice loads
Regionally, an ice cover in fjords of mainland Norway may form and break up repeatedly during win... more Regionally, an ice cover in fjords of mainland Norway may form and break up repeatedly during winter. Due to relatively high water temperatures, the freeze-up process is expected to be related to freshwater-induced stratification in the fjords in conjunction with low air temperatues. In an attempt to identify the variability of water conditions in the fjords leading up to and during ice cover development, a low-cost buoy had been developed to cope with the high potential of loss of equipment during break-up of ice. The current version of the buoy logs GPS coordinates and ocean, ice and air temperature, and transmits data through the cell phone network. Experience from the first season of multiple deployments showed that the concept is working but the physical design of the buoy could be improved to withstand forces in open water.
The specific challenges of ship operations in sea ice-covered waters of the Arctic depend on fact... more The specific challenges of ship operations in sea ice-covered waters of the Arctic depend on factors including the purpose of the operation, the capabilities of the ship and equipment available, the degree of situational awareness and crew experience. Focusing on transits of sea ice in the waters of the Northern Sea Route (NSR), this study demonstrates that the solutions currently employed range from active route finding to accepting getting beset in ice, apparently depending on the purpose of operation. Challenges and operational constraints are discussed. The analysis is based on data provided by the NSR Administration, vessel motion data from satellite-borne receivers of Automatic Identification System signals (S-AIS data of AISSat-1), and sea ice products (AMSR2 ice concentration, ice charts). Travel times northeast of Severnaya Zemlya ranged from 1 to 6 days, depending on ice pressure. A statistical relationship between travel time and ice conditions has been obtained east of t...
Winter concreting can be an attractive option for construction in remote areas where concerns abo... more Winter concreting can be an attractive option for construction in remote areas where concerns about wildlife and soil integrity are prioritized. In order to minimize disturbance of wildlife and to be able to access remote sites with minimal damage to the soil, partial winter construction of a power line is being considered in northern Norway. Ice formation has to be prevented during the early stages of concreting of mast foundations in order to ensure design properties, long transportation ways have to be considered, and quick setting and achievement of the ultimate design strength are desired. Conventional materials in conjunction with artificial heating are considered to provide a potential solution. In the current field trial we investigated the feasibility of grouting anchor bolts (rock anchors) at ground temperatures below freezing using a vertically-installed hydronic heating system to warm up the rock prior to grouting. Also, hydronic heating of the footing during winter conc...
Deterioration and ageing of concrete structures and the increased traffic intensities and loads a... more Deterioration and ageing of concrete structures and the increased traffic intensities and loads are some of the major problems facing civil engineers, industry and researchers. Corrosion of embedded steel reinforcement is one of the main causes of deterioration. Deterioration of reinforced concrete may lead to a number of undesirable consequences such as loss of serviceability, loss of load carrying capacity and reduction in safety of structures and traffics. Steel bar corrosion affects the reinforcement itself, the surrounding concrete and the composite action between steel and concrete. The most critical effect is probably the reduction in cross sectional area of the affected bar. If corrosion is allowed to propagate over a sufficiently long period of time and proper interventions not are made, loss of bond may also lead to impaired stiffness and strength of affected structural components. The main objective of this PhD project is to develop methodology for assessment of deteriora...
Cold Regions Science and Technology, 2015
Static ice loads (ice actions) are a key design parameter for dams in cold climates. However, the... more Static ice loads (ice actions) are a key design parameter for dams in cold climates. However, their theoretical description is still elusive, introducing uncertainty in design and hindering development of remediation measures. We present and analyze measurements of stresses due to thermal loads in a small reservoir in northern Norway. Several weeks of observations, including both cold and warm spells, were well-described by a simple equation that accounts for thermal expansion and temperature-dependent creep. One model parameter was found to depend systematically on the location of measurements within the reservoir. Biaxial stress measurements showed that the stress field was not homogeneous. Results suggest that the stress field in reservoirs should be predictable from first principles with numerical methods and point toward a promising, simple parameterization.
Structure and Infrastructure Engineering, 2011
Corrosion of embedded steel bars continues to be the principal cause of deterioration of reinforc... more Corrosion of embedded steel bars continues to be the principal cause of deterioration of reinforced concrete structures. The most obvious effect is the reduction in cross-sectional area of the affected steel bars. If corrosion is allowed to propagate over a sufficiently long period of time and proper interventions are not made, loss of the bond between the corroded steel bar and the surrounding contaminated concrete may also lead to impaired structural performance and safety of the affected structures. The present paper is devoted to a review of published pullout test data on bond strength of corroded steel bars in concrete. The experimental results are carefully evaluated in order to examine the influence on bond strength of parameters such as corrosion level, bar diameter, bar position, concrete cover, transverse reinforcement and impressed current density.
Digital temperature sensors provide an attractive means to conveniently record ice and water temp... more Digital temperature sensors provide an attractive means to conveniently record ice and water temperatures in remote locations. Unlike conventional analogue techniques, a digital sensor performs a physical measurement, interprets its result in terms of temperature and transmits that result to a logger or display system in digital form. Processing of digital signals is comparatively robust and cheap. Custom calibration may be applied to increase measurement accuracy. A popular example of a digital temperature sensor is the Maxim Integrated DS18B20, which is readily available as a bare sensor in a standard transistor casing, or from third-part providers as a probe with the sensor encased in a waterproofed metal sleeve. We found that the quality of water protection of the probes varies widely, and that bare sensors and sensors in probes offered by most third-party providers (i.e. not by official distributors) are almost always clones, i.e. not produced by Maxim Integrated. We summarize in this paper the spectrum of counterfeit sensors currently available and how they differ from authentic parts and specifications in the Maxim Integrated data sheet. Currently sold sensors are grouped into 7 families, 6 of them representing counterfeits. Awareness of the prevalence and characteristics of counterfeit sensors will help avoid surprises during costly experimental field work.
The present report deals with corrosion of steel reinforcement which is the principal cause of de... more The present report deals with corrosion of steel reinforcement which is the principal cause of deterioration of reinforced concrete infrastructure. Previous research on steelbar corrosion has mainly been devoted to the causes and mechanisms of corrosionwhile relatively little attention has been given to the problem of assessing the residual strength of corroded structures. The objective of the present report is to investigate the effects of steel bar corrosion on structural performance. In the first phase of this research, a comprehensive evaluation was carried out based on published laboratory testdata on corrosion of steel bars in concrete, see Appendix D. In the second phase, experimental research was conducted to investigate the effects of steel bar corrosion, using both specimens collected from the field (30 years exposure) and standard specimenscast in the laboratory. The experimental data from the present research is used todevelop methods for assessment of the structural consequences of reinforcement corr osionEC Sixth Framework ProgramSustainable Bridges – Assessment for Future Traffic Demands and Longer LivesTIP3-CT-2003-001653</p
IAHR / NTNU, Nov 1, 2020
Ice loads on a concrete dam have been calculated from stress measurements in Taraldsvikfossen Res... more Ice loads on a concrete dam have been calculated from stress measurements in Taraldsvikfossen Reservoir, a small reservoir in Narvik, Norway, during three winter seasons. Ice thickness was in the range of 0.5 to 1.0 m, and both thermal ice loads were observed and water level fluctuations up to 30 cm were observed when the ice cover froze to the spillway. The maximum global line load measured was 60 to 90 kN/m, in line with current design guidelines in Norway. Consistent with earlier reports, line loads were not evenly distributed along the dam face. A thermal line load model was able to reproduce the approximate shape and magnitude of many line load peaks even when the measured vertical stress profile could not be reproduced by the model. The result add to an extremely small body of data in Norway and motivate investigations in other pars of the country with expected higher or lower ice loads
Regionally, an ice cover in fjords of mainland Norway may form and break up repeatedly during win... more Regionally, an ice cover in fjords of mainland Norway may form and break up repeatedly during winter. Due to relatively high water temperatures, the freeze-up process is expected to be related to freshwater-induced stratification in the fjords in conjunction with low air temperatues. In an attempt to identify the variability of water conditions in the fjords leading up to and during ice cover development, a low-cost buoy had been developed to cope with the high potential of loss of equipment during break-up of ice. The current version of the buoy logs GPS coordinates and ocean, ice and air temperature, and transmits data through the cell phone network. Experience from the first season of multiple deployments showed that the concept is working but the physical design of the buoy could be improved to withstand forces in open water.
The specific challenges of ship operations in sea ice-covered waters of the Arctic depend on fact... more The specific challenges of ship operations in sea ice-covered waters of the Arctic depend on factors including the purpose of the operation, the capabilities of the ship and equipment available, the degree of situational awareness and crew experience. Focusing on transits of sea ice in the waters of the Northern Sea Route (NSR), this study demonstrates that the solutions currently employed range from active route finding to accepting getting beset in ice, apparently depending on the purpose of operation. Challenges and operational constraints are discussed. The analysis is based on data provided by the NSR Administration, vessel motion data from satellite-borne receivers of Automatic Identification System signals (S-AIS data of AISSat-1), and sea ice products (AMSR2 ice concentration, ice charts). Travel times northeast of Severnaya Zemlya ranged from 1 to 6 days, depending on ice pressure. A statistical relationship between travel time and ice conditions has been obtained east of t...
Winter concreting can be an attractive option for construction in remote areas where concerns abo... more Winter concreting can be an attractive option for construction in remote areas where concerns about wildlife and soil integrity are prioritized. In order to minimize disturbance of wildlife and to be able to access remote sites with minimal damage to the soil, partial winter construction of a power line is being considered in northern Norway. Ice formation has to be prevented during the early stages of concreting of mast foundations in order to ensure design properties, long transportation ways have to be considered, and quick setting and achievement of the ultimate design strength are desired. Conventional materials in conjunction with artificial heating are considered to provide a potential solution. In the current field trial we investigated the feasibility of grouting anchor bolts (rock anchors) at ground temperatures below freezing using a vertically-installed hydronic heating system to warm up the rock prior to grouting. Also, hydronic heating of the footing during winter conc...
Deterioration and ageing of concrete structures and the increased traffic intensities and loads a... more Deterioration and ageing of concrete structures and the increased traffic intensities and loads are some of the major problems facing civil engineers, industry and researchers. Corrosion of embedded steel reinforcement is one of the main causes of deterioration. Deterioration of reinforced concrete may lead to a number of undesirable consequences such as loss of serviceability, loss of load carrying capacity and reduction in safety of structures and traffics. Steel bar corrosion affects the reinforcement itself, the surrounding concrete and the composite action between steel and concrete. The most critical effect is probably the reduction in cross sectional area of the affected bar. If corrosion is allowed to propagate over a sufficiently long period of time and proper interventions not are made, loss of bond may also lead to impaired stiffness and strength of affected structural components. The main objective of this PhD project is to develop methodology for assessment of deteriora...
Cold Regions Science and Technology, 2015
Static ice loads (ice actions) are a key design parameter for dams in cold climates. However, the... more Static ice loads (ice actions) are a key design parameter for dams in cold climates. However, their theoretical description is still elusive, introducing uncertainty in design and hindering development of remediation measures. We present and analyze measurements of stresses due to thermal loads in a small reservoir in northern Norway. Several weeks of observations, including both cold and warm spells, were well-described by a simple equation that accounts for thermal expansion and temperature-dependent creep. One model parameter was found to depend systematically on the location of measurements within the reservoir. Biaxial stress measurements showed that the stress field was not homogeneous. Results suggest that the stress field in reservoirs should be predictable from first principles with numerical methods and point toward a promising, simple parameterization.
Structure and Infrastructure Engineering, 2011
Corrosion of embedded steel bars continues to be the principal cause of deterioration of reinforc... more Corrosion of embedded steel bars continues to be the principal cause of deterioration of reinforced concrete structures. The most obvious effect is the reduction in cross-sectional area of the affected steel bars. If corrosion is allowed to propagate over a sufficiently long period of time and proper interventions are not made, loss of the bond between the corroded steel bar and the surrounding contaminated concrete may also lead to impaired structural performance and safety of the affected structures. The present paper is devoted to a review of published pullout test data on bond strength of corroded steel bars in concrete. The experimental results are carefully evaluated in order to examine the influence on bond strength of parameters such as corrosion level, bar diameter, bar position, concrete cover, transverse reinforcement and impressed current density.