Creep Parameters for Pile Settlement Equations

1989 ◽  
Vol 111 (4) ◽  
pp. 258-263
Author(s):  
D. Stelzer ◽  
O. B. Andersland
Keyword(s):  
Static Load ◽  
Experimental Tests ◽  
Sand Particle ◽  
Shear Stresses ◽  
Frozen Ground ◽  
Creep Equation ◽  
Frozen Sand ◽  
Pile Settlement ◽  
Ice Content ◽  
Friction Pile

Friction pile settlement in frozen ground is tyically predicted on the basis of a creep equation relating shear stresses at the soil/pile interface to pile displacement rates. Creep parameters are used to characterize soil type, soil/ice structure, temperature, and loading conditions. Experimental tests involving model steel piles embedded in frozen sand provided data showing that change in a given test variable can alter the numerical value for some of the creep parameters. The test variables included static, incremental, and dynamic loading; pile surface roughness; soil ice content; and sand particle size. Changes observed included the apparent effect on creep rate when a small dynamic load was superimposed on the static load. A tabulation of observed creep parameter changes is included.

MONITORING THE DYNAMICS OF THERMOABRASION COASTS AT KHARASAVEY AREA, WESTERN YAMAL (KARA SEA)

2017 ◽  
Author(s):  
Dmitry Kuznetsov ◽  
Dmitry Kuznetsov ◽  
Anatoliy Kamalov ◽  
Anatoliy Kamalov ◽  
Nataliya Belova ◽  
...  
Keyword(s):  
Human Impact ◽  
Remote Sensing Data ◽  
Kara Sea ◽  
Motor Vehicles ◽  
Yamal Peninsula ◽  
Western Coast ◽  
Frozen Ground ◽  
Coastal Dynamics ◽  
The North ◽  
Ice Content

The dynamics of thermoabrasion coasts on loose sediments under permafrost conditions are highly variable due to several factors: length of the dynamic period of the year, mechanic composition of the frozen ground and its ice content, hydrometeorological conditions, and human impact. Multiannual monitoring of the coastal zone was carried out by Lab. Geoecology of the North (Moscow State University) at the 22 km long Kharasavey deposit site, Western Coast of Yamal Peninsula (Kara Sea). The methods include direct measurements and observations (repeated topographic survey of shore transects from 1981 to 2012) along with remote sensing data analysis (images from 1964 to 2011). This allowed producing detailed characteristics of coastal dynamics. At the site, thermoabrasion coasts occupy the most part, and accumulative coasts are present in the north. Data on natural relief forming factors and ground composition are included in the detailed geomorphologic map of the site. Shore retreat rate shows correlation to amounts of wind-wave energy and to specific wind directions. Human impact on the coast includes dredging at the port channel, mining of sand, driving motor vehicles, and deposition of construction debris. Relations between shore retreat rate and aforementioned factors were studied, including dependencies on ice content, and shore segmentation was carried out. This allows for coastal dynamics forecasts in the region.

Effect of Dynamic Shear Force on Fastener Loosening in Assemblies

1997 ◽  
Author(s):  
Yubo Dong ◽  
Daniel P. Hess
Keyword(s):  
Cantilever Beam ◽  
Static Load ◽  
Nodal Line ◽  
Shear Stresses ◽  
Dynamic Shear ◽  
Bernoulli Beam ◽  
Cyclic Shear ◽  
Nodal Lines ◽  
Inertial Loading ◽  
Euler Bernoulli Beam

Abstract Placement and orientation of fasteners in assemblies is generally based on convenience or static load and strength considerations. Vibration and other dynamic loads can result in loosening of threaded product, particularly when cyclic shear stresses are present. This paper investigates the placement of a bolt and nut on a compound cantilever beam subjected to dynamic inertial loading. Calculations for an inertial loaded, cantilever, Euler-Bernoulli beam show that the dynamic shear stress is maximum near the dynamic nodal lines, and essentially vanishes near the anti-nodes. Experiments with a compound cantilever beam assembly with one fastener reveal that loosening occurs more readily when the bolt and nut are placed near a nodal line. Data presented include time to loosen, break-away torque, and acceleration level. The data shows that fastener integrity is maintained for longer periods of time and with lower tightening torques, when the bolt and nut are positioned away from nodal lines where shear stresses are lower, even though acceleration levels are higher.

Utilizing Modeling in a Reliability Study of ACA Joints in Humidity Tests

2013 ◽  
Vol 10 (1) ◽  
pp. 30-39 ◽  
Author(s):  
Kirsi Saarinen ◽  
Laura Frisk
Keyword(s):  
Radio Frequency Identification ◽  
Cost Savings ◽  
Experimental Tests ◽  
Shear Stresses ◽  
Cycling Test ◽  
Humidity Level ◽  
Anisotropic Conductive Adhesive ◽  
Frequency Identification ◽  
Identification Tags ◽  
Selection Of

Radio frequency identification tags (RFID) with anisotropic conductive adhesive (ACA) joints are used in various applications where the environmental conditions may impair their reliability. Thus the effects of different environmental stresses on reliability need to be investigated. The purpose of this work was to study whether a relatively simple shear stress model can be utilized in reliability prediction of anisotropically conductive paste (ACP) joints in an accelerated humidity test on the basis of the information obtained from another humidity test. If modeling gives accurate results when studying reliability, the need for actual testing would decrease and thereby time and cost savings could be achieved. In this study, finite element models were made to calculate shear stresses in ACP joints induced by two different humidity tests. Additionally, experimental tests were performed and the results were compared with those of modeling. The test samples were RFID tags whose microchips were attached with ACP. A constant humidity test was used to study the effects of high humidity level and a humidity cycling test was used to examine the effects of constantly varying humidity. In the modeling it was observed that the selection of the stress-free temperature has a significant effect on the results. With three different stress-free temperatures, three different sets of results were obtained. Although the tags saturated in the extreme conditions of the humidity cycling test, according to modeling, the change in relative humidity level in the humidity cycling test did not increase the harshness of the test. However, the temperature change in the humidity cycling test increased the harshness.

Contact shear stresses in dowel-type joints with expansive kits of timber structures

2016 ◽  
Vol 231 (1) ◽  
pp. 140-149
Author(s):  
Jose G Fueyo ◽  
Manuel Domínguez ◽  
Jose A Cabezas
Keyword(s):  
Experimental Tests ◽  
Element Model ◽  
Shear Stresses ◽  
Load Carrying Capacity ◽  
Timber Structures ◽  
Expansion Process ◽  
Global Response ◽  
Load Carrying ◽  
Overall Performance ◽  
The Relationship

This paper studies the shear stresses appearing in the contact zones of dowel-type joints of timber structures using expansive kits. To achieve this goal, a finite element model capable of determining the effect of using these kits on the global response of the joint has been prepared. For its development, different tools have been used to model the expansion process, the contact between the different parts of the joint, the compression pressures triggered by this contact, the resulting shear stresses caused by friction and, finally, the effect of all these circumstances on the overall performance of the joint, especially on the relationship between the applied load and the related displacement. The design of the model has been checked for correctness using experimental tests. The results obtained show that the use of expansive kits slightly improves the load-carrying capacity of the dowel through the rope effect.

Model Pile‐Settlement Behavior in Frozen Sand

1991 ◽  
Vol 5 (1) ◽  
pp. 1-13 ◽  
Author(s):  
David L. Stelzer ◽  
Orlando B. Andersland
Keyword(s):  
Settlement Behavior ◽  
Model Pile ◽  
Frozen Sand ◽  
Pile Settlement

scholarly journals Modeling the Influence of a Magnetomechanical Effect on the Permeability Tensor of a Tensductor Core

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4023 ◽  
Author(s):  
Roman Szewczyk ◽  
Michał Nowicki ◽  
Anna Ostaszewska-Liżewska ◽  
Mika Malinen
Keyword(s):  
Magnetic Permeability ◽  
Experimental Tests ◽  
Permeability Tensor ◽  
Soft Magnetic Materials ◽  
Shear Stresses ◽  
Soft Magnetic ◽  
Principal Stresses ◽  
Tensile Forces ◽  
Rotation Procedure ◽  
Good Agreement

This paper presents a new method of modeling the influence of mechanical stresses on a magnetic permeability tensor of soft magnetic materials. The proposed method utilizes the principal stresses concept to compensate the influence of shear stresses. As a result, the stress dependence of a magnetic permeability tensor may be assessed with only the knowledge about the influence of axial stresses on magnetic properties of isotropic material. The proposed method was used for a finite element method based model of a tensductor designed for measurements of tensile forces. Due to the fact that 2D stresses distribution occurs in a tensductor, simplification of both principal stresses and a magnetic permeability tensor rotation procedure was proposed. As a result, good agreement was reached between the results of modeling and the results of experimental tests. This result validates the possibility of utilization of the proposed modeling method for the design of magnetomechanical devices.

Experimental study of the axial movement of the pipeline in permafrost conditions with changes in soil temperature and humidity

2020 ◽  
Vol 10 (3) ◽  
pp. 243-251
Author(s):  
Ramil N. Bakhtizin ◽  
◽  
Sultanmagomed M. Sultanmagomedov ◽  
Timur S. Sultanmagomedov ◽  
Denis A. Gulin ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Longitudinal Direction ◽  
Resistance Coefficient ◽  
Soil Reaction ◽  
Shear Stresses ◽  
Sharp Change ◽  
Frozen Ground ◽  
Frozen Soils ◽  
Temperature And Humidity ◽  
Different Soils

The significant part of the frozen soils, common of the northeastern regions of the laying of pipelines, loses its bearing capacity when the temperature rises to the values of melting ice. In turn, the loss of the design position of the pipeline section located in the thawed soil area causes unacceptable deformations, which can lead to incidents and accidents. The most dangerous places arise at the boundaries of sites with different soils properties, and primarily at the border of frozen and thawed soils. Currently, to evaluate the thermal interaction of pipelines with frozen thawing soils, data are used for ordinary thawed soils, however standard methods are not suitable in these cases, since they do not take into account a sharp change in the properties of frozen soils during thawing. The authors conducted studies of soil resistance (coefficient of soil reaction) to the longitudinal displacements of the pipeline depending on the temperature and humidity of the soil. For this purpose, an experimental model of a pipeline in frozen ground was developed. The main characteristics of the model and the experimental technique are described in detail. The results of studies of the coefficient of soil reaction in the longitudinal direction, as well as the ultimate shear stresses depending on the temperature and humidity of the soil, the type of soil and the depth of the pipeline are presented. The dependence of the coefficient of soil reaction on the ratio of the depth of the pipeline to its diameter is shown. It was established that at a temperature t = –8... –10 °С and humidity w = 10...15 %, the highest value of the coefficient of soil reaction is achieved. In the absence of moisture, the temperature does not affect the coefficient of soil reaction. The lowest coefficient of soil reaction for frozen soils is achieved at a positive soil temperature.

Downward water movement into frozen ground, western arctic coast, Canada

1983 ◽  
Vol 20 (1) ◽  
pp. 120-134 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Soviet Union ◽  
Active Layer ◽  
Water Movement ◽  
Field Studies ◽  
Frozen Ground ◽  
Thermally Induced ◽  
The Soviet Union ◽  
Field Evidence ◽  
Hydraulic Gradients ◽  
Ice Content

Field studies carried out mainly since 1975 in permafrost areas of Alaska, Canada, China, and the Soviet Union have been combined with the results of laboratory investigations to show that in summer water can move from the thawing active layer into the subjacent frozen active layer and under certain conditions even into the top of permafrost. Direct field evidence discussed includes: data from drilling and neutron probe logging, which show a summer increase in the ice content of already frozen ground; summer heave of heavemeters, with heave occurring in the frozen active layer; and increase in the ice content of the subjacent frozen ground in both permafrost and non-permafrost areas, caused by snowmelt infiltration. Indirect field and laboratory evidence is also added to support the direct lines of evidence. The conditions that favor the downward migration of water from thawed to frozen ground are examined in terms of thermally induced hydraulic gradients, hydraulic conductivity, content of unfrozen pore water, temperature gradients, ice content, and gravity. Some geocryologic implications of the summer growth of ice in frozen ground, including the effects on water balance calculations and the origin of patterned ground, are briefly mentioned.

Seismic reliability of axially loaded vertical piles

2020 ◽  
Vol 57 (12) ◽  
pp. 1805-1819
Author(s):  
Gennaro Esposito ◽  
Gordon A. Fenton ◽  
Farzaneh Naghibi
Keyword(s):  
Probabilistic Model ◽  
Static Load ◽  
Seismic Loads ◽  
Seismic Reliability ◽  
Reliability Level ◽  
Code Calibration ◽  
Current Design ◽  
Pile Settlement ◽  
A Site ◽  
Acceptable Reliability

The reliability of single vertical pile foundations subjected to seismic loads is assessed and compared with the minimum acceptable reliability level for static load conditions mandated by the Canadian codes. The analysis is executed for a site with a mean shear-wave velocity of the top 30 m of the ground equal to 250 m/s subjected to the ground motion hazard of five Canadian cities. Using both a full probabilistic analysis and simplified probabilistic model, the results seem to indicate that the current design practice is unable to achieve the reliability target of the codes. The shortfall is particularly significant when the limiting pile settlement is relatively small. The calculated reliability level of small limiting settlements is impacted by the geotechnical variability, whereas the seismic hazard variability affects large pile limiting settlements. Finally, the simplified probabilistic model produces the same results as the full probabilistic model for large pile settlement and is a convenient tool to execute code calibration.

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