The Experts below are selected from a list of 289269 Experts worldwide ranked by ideXlab platform
Perry Bartelt - One of the best experts on this subject based on the ideXlab platform.
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measurements of hillslope debris flow Impact Pressure on obstacles
Landslides, 2012Co-Authors: Louis Bugnion, Perry Bartelt, Brian W Mcardell, Corinna WendelerAbstract:We present measurements of hillslope debris flow Impact Pressures on small obstacles. Two Impact sensors have been installed in a real-scale experimental site where 50 m3 of water-saturated soil material are released from rest. Impact velocities vary between 2 and 13 m/s; flow heights between 0.3 and 1.0 m. The maximum Impact Pressures measured over 15 events represent between 2 and 50 times the equivalent static Pressures. The measurements reveal that quadratic velocity-dependent formulas can be used to estimate Impact Pressures. Impact coefficients C are constant from front to tail and range between 0.4 < C < 0.8 according to the individual events. The Pressure fluctuations to depend on the sensor size and are between 20% and 60% of the mean Pressure values. Our results suggest that hazard guidelines for hillslope debris flows should be based on quadratic velocity-dependent formulas.
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Impact Pressures and flow regimes in dense snow avalanches observed at the vallee de la sionne test site
Journal of Geophysical Research, 2008Co-Authors: Betty Sovilla, Mark Schaer, Martin Kern, Perry BarteltAbstract:[1] A fundamental problem in avalanche engineering is to determine the Impact Pressures exerted on structures. This task is complicated because snow avalanches flow in a variety of regimes, primarily depending on snow temperature and moisture content. In this paper we address this problem by analyzing measured Impact Pressures, flow velocities, and flow depths of five Vallee de la Sionne avalanches. The measurements are made on a 20 m high tubular pylon instrumented with high-frequency Pressure transducers and optoelectronic velocity sensors. In the observed avalanches, we find both subcritical and supercritical flow regimes. Typical Froude numbers were smaller than 6. The subcritical regime (Fr < 1) is characterized by a flow plug riding above a highly sheared basal layer. The measured Pressures are large and velocity-independent in contradiction to calculation procedures. Pressure fluctuations increase with flow depth, indicating a kinematic stick-slip phenomena which is largest at the basal layer. Supercritical flow regimes (1 < Fr < 6) are characterized by a sheared flow all over the avalanche depth. In this regime the Impact Pressure is velocity-dependent. We derive relationships governing Impact Pressure as a function of the Froude number, and therefore flow regime, encompassing all the observed avalanches.
Betty Sovilla - One of the best experts on this subject based on the ideXlab platform.
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Impact Pressures and flow regimes in dense snow avalanches observed at the vallee de la sionne test site
Journal of Geophysical Research, 2008Co-Authors: Betty Sovilla, Mark Schaer, Martin Kern, Perry BarteltAbstract:[1] A fundamental problem in avalanche engineering is to determine the Impact Pressures exerted on structures. This task is complicated because snow avalanches flow in a variety of regimes, primarily depending on snow temperature and moisture content. In this paper we address this problem by analyzing measured Impact Pressures, flow velocities, and flow depths of five Vallee de la Sionne avalanches. The measurements are made on a 20 m high tubular pylon instrumented with high-frequency Pressure transducers and optoelectronic velocity sensors. In the observed avalanches, we find both subcritical and supercritical flow regimes. Typical Froude numbers were smaller than 6. The subcritical regime (Fr < 1) is characterized by a flow plug riding above a highly sheared basal layer. The measured Pressures are large and velocity-independent in contradiction to calculation procedures. Pressure fluctuations increase with flow depth, indicating a kinematic stick-slip phenomena which is largest at the basal layer. Supercritical flow regimes (1 < Fr < 6) are characterized by a sheared flow all over the avalanche depth. In this regime the Impact Pressure is velocity-dependent. We derive relationships governing Impact Pressure as a function of the Froude number, and therefore flow regime, encompassing all the observed avalanches.
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measurements and analysis of full scale avalanche Impact Pressure at the vallee de la sionne test site
Proceedings of the 2006 International Snow Science Workshop Telluride Colorado, 2006Co-Authors: Betty Sovilla, Mark Schaer, Lambert RammerAbstract:Abstracts Impact Pressures of eight snow avalanches measured at the Swiss avalanche test site Vallee de la Sionne are reported. Avalanche typologies varied between dense and powder. Measurements were performed on obstacles of different shape and dimension. High-frequency Pressure sensors were mounted on a 20 m high tubular pylon and on a 5 m high steel wedge. To interpret the influence of sensor dimension on Impact Pressure measurements, the total Pressure exerted on the steel wedge was recorded using two bi-axial sensors and compared to the Pressure recorded by the high-frequency sensors. On a small concrete wall, a 1 m 2 Pressure plate mounted with 4 load-gauge bolts measured normal and tangential forces. Along the tubular pylon (between 1–6 m above ground) optoelectronic sensors recorded the avalanche flow velocity. Flow depths were measured by mechanical sensors. Analysis of high resolution Impact forces in combination with velocity measurements allowed us to reconstruct the flow structure. We combined Impact Pressure with observation on avalanche structure to obtain load distribution and size effects for different avalanche typologies. Measured Pressures are compared to the existing Swiss calculation procedure. It is shown that actual calculation formulas are not able to properly reproduce the measured Pressure values and the load distribution.
Mark Schaer - One of the best experts on this subject based on the ideXlab platform.
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Impact Pressures and flow regimes in dense snow avalanches observed at the vallee de la sionne test site
Journal of Geophysical Research, 2008Co-Authors: Betty Sovilla, Mark Schaer, Martin Kern, Perry BarteltAbstract:[1] A fundamental problem in avalanche engineering is to determine the Impact Pressures exerted on structures. This task is complicated because snow avalanches flow in a variety of regimes, primarily depending on snow temperature and moisture content. In this paper we address this problem by analyzing measured Impact Pressures, flow velocities, and flow depths of five Vallee de la Sionne avalanches. The measurements are made on a 20 m high tubular pylon instrumented with high-frequency Pressure transducers and optoelectronic velocity sensors. In the observed avalanches, we find both subcritical and supercritical flow regimes. Typical Froude numbers were smaller than 6. The subcritical regime (Fr < 1) is characterized by a flow plug riding above a highly sheared basal layer. The measured Pressures are large and velocity-independent in contradiction to calculation procedures. Pressure fluctuations increase with flow depth, indicating a kinematic stick-slip phenomena which is largest at the basal layer. Supercritical flow regimes (1 < Fr < 6) are characterized by a sheared flow all over the avalanche depth. In this regime the Impact Pressure is velocity-dependent. We derive relationships governing Impact Pressure as a function of the Froude number, and therefore flow regime, encompassing all the observed avalanches.
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measurements and analysis of full scale avalanche Impact Pressure at the vallee de la sionne test site
Proceedings of the 2006 International Snow Science Workshop Telluride Colorado, 2006Co-Authors: Betty Sovilla, Mark Schaer, Lambert RammerAbstract:Abstracts Impact Pressures of eight snow avalanches measured at the Swiss avalanche test site Vallee de la Sionne are reported. Avalanche typologies varied between dense and powder. Measurements were performed on obstacles of different shape and dimension. High-frequency Pressure sensors were mounted on a 20 m high tubular pylon and on a 5 m high steel wedge. To interpret the influence of sensor dimension on Impact Pressure measurements, the total Pressure exerted on the steel wedge was recorded using two bi-axial sensors and compared to the Pressure recorded by the high-frequency sensors. On a small concrete wall, a 1 m 2 Pressure plate mounted with 4 load-gauge bolts measured normal and tangential forces. Along the tubular pylon (between 1–6 m above ground) optoelectronic sensors recorded the avalanche flow velocity. Flow depths were measured by mechanical sensors. Analysis of high resolution Impact forces in combination with velocity measurements allowed us to reconstruct the flow structure. We combined Impact Pressure with observation on avalanche structure to obtain load distribution and size effects for different avalanche typologies. Measured Pressures are compared to the existing Swiss calculation procedure. It is shown that actual calculation formulas are not able to properly reproduce the measured Pressure values and the load distribution.
Martin Kern - One of the best experts on this subject based on the ideXlab platform.
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Impact Pressures and flow regimes in dense snow avalanches observed at the vallee de la sionne test site
Journal of Geophysical Research, 2008Co-Authors: Betty Sovilla, Mark Schaer, Martin Kern, Perry BarteltAbstract:[1] A fundamental problem in avalanche engineering is to determine the Impact Pressures exerted on structures. This task is complicated because snow avalanches flow in a variety of regimes, primarily depending on snow temperature and moisture content. In this paper we address this problem by analyzing measured Impact Pressures, flow velocities, and flow depths of five Vallee de la Sionne avalanches. The measurements are made on a 20 m high tubular pylon instrumented with high-frequency Pressure transducers and optoelectronic velocity sensors. In the observed avalanches, we find both subcritical and supercritical flow regimes. Typical Froude numbers were smaller than 6. The subcritical regime (Fr < 1) is characterized by a flow plug riding above a highly sheared basal layer. The measured Pressures are large and velocity-independent in contradiction to calculation procedures. Pressure fluctuations increase with flow depth, indicating a kinematic stick-slip phenomena which is largest at the basal layer. Supercritical flow regimes (1 < Fr < 6) are characterized by a sheared flow all over the avalanche depth. In this regime the Impact Pressure is velocity-dependent. We derive relationships governing Impact Pressure as a function of the Froude number, and therefore flow regime, encompassing all the observed avalanches.
Jeom Kee Paik - One of the best experts on this subject based on the ideXlab platform.
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nonlinear structural behaviour of membrane type lng carrier cargo containment systems under Impact Pressure loads at 163 c
Ships and Offshore Structures, 2017Co-Authors: Jung Min Sohn, Jeom Kee PaikAbstract:ABSTRACTThis paper is a sequel to the paper dealing with quasi-static responses previously studied by the authors. The structural failure of membrane-type liquefied natural gas carrier (LNGC) cargo tank is an important issue in the construction of ultra-large an LNG carrier. However, quasi-static analysis to investigate the structural failure is difficult and tends to give conservative results. To compensate the weak points of the quasi-static analysis, a procedure for the dynamic analysis was developed to assess the structural failure using nonlinear finite element method. A nonlinear finite element method is employed to model metal membrane, insulation and surface contacts. Various element formulations are tested at different points along a corrugated surface to optimise the accuracy of the model with respect to computation time. Material properties used in the model are calibrated based on experimentally measured values at cryogenic conditions (−163 °C). The model is used to predict the structural fail...
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nonlinear structural analysis of membrane type lng carrier cargo containment system under cargo static Pressure loads at the cryogenic condition with a temperature of 163 c
Ships and Offshore Structures, 2011Co-Authors: Jeom Kee Paik, Jung Min Sohn, Y S ShinAbstract:Liquefied natural gas carriers (LNGCs) have become larger in size but without any accompanying increase in the number of cargo tanks, thus resulting in a subsequent increase in both cargo Pressure loads and sloshing Impact Pressure actions. This trend raises the question of whether the cargo containment systems of LNGCs in their existing proportions are strong enough to withstand the abnormal actions that may occur in service. Answering this requires an investigation of possible changes in the structural design of the membrane corrugations in cargo tanks, which essentially necessitates precise analysis of strength performance. The objective of the present paper is to investigate the structural behaviour of membrane-type LNGC cargo containment system under cargo static Pressure loads at the cryogenic condition with a temperature of −163°C, while a sequel to the present paper will be reported in a separate paper dealing with structural behaviour under sloshing Impact Pressure loads. In the present study, AN...
