Experimental study of axial behaviour of tapered piles

1998 ◽  
Vol 35 (4) ◽  
pp. 641-654 ◽  
Author(s):  
Jinqi Wei ◽  
M Hesham El Naggar
Keyword(s):  
Cross Sections ◽  
Load Transfer ◽  
Confining Pressure ◽  
Transfer Model ◽  
Operating Characteristics ◽  
Unit Load ◽  
Shaft Resistance ◽  
Cylindrical Piles ◽  
Axial Response ◽  
The Difference

Tapered piles, which have greater top cross sections than bottom ones, have the potential for substantial cost advantages for static loading conditions. However, tapered piles have not often been considered a design option because of the lack of design tools and knowledge about the behaviour of these piles. The objectives of this study are to explore and better understand the operating characteristics of the axial response of tapered piles. A large laboratory facility for testing model piles was developed. In this facility, the soil was contained in a steel soil chamber and pressurized using an air bladder to model the confining pressure. Three instrumented steel piles with different degrees of taper were used in this study. As expected, it was found that as the taper angle increased, the shaft resistance increased. It was found that the shaft resistance of the tapered pile was up to 40% larger than that of the cylindrical pile. The difference in the shaft resistance of the two types decreased for higher values of confining pressure. It was also found that the load distribution along the pile shaft for both pile types had the same pattern. However, this pattern varied as the confining pressure increased. Furthermore, the unit load transfer was significantly affected by the initial sand density for both pile types at low confining pressure, but as the confining pressure increased, this effect diminished. It is concluded that the tapered piles offer a larger resistance than the cylindrical piles. However, for longer piles, it is suggested that the taper be limited to the top length corresponding to 20 diameters.Key words: tapered piles, shaft friction, axial response, load transfer, model testing.

The Calculation of Critical Pile Length for Super-Long Pile Based on Settlement Control

2011 ◽  
Vol 71-78 ◽  
pp. 4179-4183
Author(s):  
Li Nong Xia ◽  
Yun Dong Miao ◽  
Tie Qiang Tan ◽  
Xin Tong
Keyword(s):  
Shear Deformation ◽  
Field Measurement ◽  
Load Transfer ◽  
Working Condition ◽  
Transfer Model ◽  
Shaft Resistance ◽  
Pile Diameter ◽  
Pile Settlement ◽  
Deformation Transfer ◽  
Pile Length

Based on the analysis of character of load-transfer of super-long pile, for the purpose of pile settlement control, critical pile length for single friction super-long pile was calculated by Cooke’s shear deformation-transfer model, because the assumption of Cooke’s model is similar with working condition of super-long pile. In the analysis, compression of pile is taken into account. Then, the design chart of critical pile length for super-long pile is provided for normal design index. Lastly, the critical pile length of an engineering example is analysed by the method, the calculated results have agreed well with the field measurement. The analysis show that critical pile length is greatly concerned with ratio of Young’s module of pile and soil, the greater the ratio is, longer the critical pile length is. Pile diameter also affects the critical pile length, the larger the diameter is, longer the critical pile length is. In addition, the critical pile length of super-long pile is concerned with shaft resistance distribution along the pile.

scholarly journals Long-Term Observations of Microwave Brightness Temperatures over a Metropolitan Area: Comparison of Radiometric Data and Spectra Simulated with the Use of Radiosonde Measurements

2021 ◽  
Vol 13 (11) ◽  
pp. 2061
Author(s):  
Mikhail V. Belikovich ◽  
Mikhail Yu. Kulikov ◽  
Dmitry S. Makarov ◽  
Natalya K. Skalyga ◽  
Vitaly G. Ryskin ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Elevation Angle ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Systematic Bias ◽  
Tropospheric Temperature ◽  
Absorption Model ◽  
60 Ghz ◽  
Error Budget ◽  
The Difference

Ground-based microwave radiometers are increasingly used in operational meteorology and nowcasting. These instruments continuously measure the spectra of downwelling atmospheric radiation in the range 20–60 GHz used for the retrieval of tropospheric temperature and water vapor profiles. Spectroscopic uncertainty is an important part of the retrieval error budget, as it leads to systematic bias. In this study, we analyze the difference between observed and simulated microwave spectra obtained from more than four years of microwave and radiosonde observations over Nizhny Novgorod (56.2° N, 44° E). We focus on zenith-measured and elevation-scanning data in clear-sky conditions. The simulated spectra are calculated by a radiative transfer model with the use of radiosonde profiles and different absorption models, corresponding to the latest spectroscopy research. In the case of zenith-measurements, we found a systematic bias (up to ~2 K) of simulated spectra at 51–54 GHz. The sign of bias depends on the absorption model. A thorough investigation of the error budget points to a spectroscopic nature of the observed differences. The dependence of the results on the elevation angle and absorption model can be explained by the basic properties of radiative transfer and by cloud contamination at elevation angles.

STUDY OF IN-MEDIUM PROPERTIES OF N*(1535) AND CHIRAL SYMMETRY FOR BARYONS THROUGH THE η-MESIC NUCLEI FORMATION AT J-PARC

2008 ◽  
Vol 23 (27n30) ◽  
pp. 2512-2515 ◽  
Author(s):  
HIDEKO NAGAHIRO ◽  
DAISUKE JIDO ◽  
SATORU HIRENZAKI
Keyword(s):  
Chiral Symmetry ◽  
Cross Sections ◽  
Optical Potential ◽  
Nuclear Medium ◽  
Nucleus Interaction ◽  
Level Crossing ◽  
Doublet Model ◽  
The Difference ◽  
Characteristic Features ◽  
Mesic Nuclei

We investigate the properties of η-nucleus interaction by postulating the N*(1535) dominance for η-N system. We evaluate the N*(1535) properties in the nuclear medium using two kinds of chiral models, and find that these two models provide qualitatively different η-nucleus optical potentials reflecting the quite distinct properties of N*(1535) in these chiral models. Especially, in the chiral doublet model, we can expect to have the level crossing between η and N*(1535)-hole which is expected to provide the characteristic features for the optical potential and the formation spectra. We find also that the difference of these models can be seen in the formation cross sections of the η mesic nuclei with (π+, p ) reaction expected to be performed at J-PARC project.

Experimental Study of the Rotary Filling Piles with Large-Diameter under the Axial Load

2012 ◽  
Vol 594-597 ◽  
pp. 527-531
Author(s):  
Wan Qing Zhou ◽  
Shun Pei Ouyang
Keyword(s):  
Experimental Study ◽  
Axial Load ◽  
Load Transfer ◽  
Soft Soil ◽  
Large Diameter ◽  
Shaft Resistance ◽  
Tip Resistance ◽  
Soil Foundation ◽  
Soft Soil Foundation ◽  
Deep Soft Soil

Based on the experimental study of rotary filling piles with large diameter subjected to axial load in deep soft soil, the bearing capacity behavior and load transfer mechanism were discussed. Results show that in deep soft soil foundation, the super–long piles behave as end-bearing frictional piles. The exertion of the shaft resistance is not synchronized. The upper layer of soil is exerted prior to the lower part of soil. Meanwhile, the exertion of shaft resistance is prior to the tip resistance. For the different soil and the different depth of the same layer of soil, shaft resistance is different.

Numerical Analysis of Branch Mechanical Response to Loading

2019 ◽  
Vol 45 (4) ◽  
Author(s):  
Barbora Vojáčková ◽  
Jan Tippner ◽  
Petr Horáček ◽  
Luděk Praus ◽  
Václav Sebera ◽  
...  
Keyword(s):  
Finite Element ◽  
Cross Sections ◽  
Mechanical Response ◽  
Mechanical Analysis ◽  
Beam Deflection ◽  
Design System ◽  
Elliptical Cross ◽  
Static Mechanical ◽  
The Difference ◽  
Tree Uprooting

Failure of a tree can be caused by a stem breakage, tree uprooting, or branch failure. While the pulling test is used for assessing the first two cases, there is no device-supported method to assess branch failure. A combination of the optical technique, pulling test, and deflection curve analysis could provide a device-supported tool for this kind of assessment. The aim of the work was to perform a structural analysis of branch response to static mechanical loading. The analyses were carried out by finite element simulations in ANSYS using beam tapered elements of elliptical cross-sections. The numerical analyses were verified by the pulling test combined with a sophisticated optical assessment of deflection evaluation. The Probabilistic Design System was used to find the parameters that influence branch mechanical response to loading considering the use of cantilever beam deflection for stability analysis. The difference in the branch’s deflection between the simulation and the experiment is 0.5% to 26%. The high variability may be explained by the variable modulus of the elasticity of branches. The finite element (FE) sensitivity analysis showed a higher significance of geometry parameters (diameter, length, tapering, elliptical cross-section) than material properties (elastic moduli). The anchorage rotation was found to be significant, implying that this parameter may affect the outcome in mechanical analysis of branch behavior. The branch anchorage can influence the deflection of the whole branch, which should be considered in stability assessment.

Fluid Flow and Heat Transfer of Liquid Sodium in Small-Scale Heat Sinks With Different Geometries

2021 ◽  
Author(s):  
Mahyar Pourghasemi ◽  
Nima Fathi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Sections ◽  
Heat Sink ◽  
Volume Ratio ◽  
Heat Sinks ◽  
Liquid Sodium ◽  
Small Scale ◽  
Nusselt Numbers ◽  
The Difference

Abstract 3-D numerical simulations are performed to investigate liquid sodium (Na) flow and the heat transfer within miniature heat sinks with different geometries and hydraulic diameters of less than 5 mm. Two different straight small-scale heat sinks with rectangular and triangular cross-sections are studied in the laminar flow with the Reynolds number up to 1900. The local and average Nusselt numbers are obtained and compared against eachother. At the same surface area to volume ratio, rectangular minichannel heat sink leads to almost 280% higher convective heat transfer rate in comparison with triangular heat sink. It is observed that the difference between thermal efficiencies of rectangular and triangular minichannel heat sinks was independent of flow Reynolds number.

Simulation of Flow Field on a Large Scale Wind Turbine

2008 ◽  
Author(s):  
I. Janajreh ◽  
C. Ghenai
Keyword(s):  
Flow Field ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Cross Sections ◽  
Large Scale ◽  
Wind Farms ◽  
Operating Characteristics ◽  
Cross Sectional ◽  
Capital Costs

Large scale wind turbines and wind farms continue to evolve mounting 94.1GW of the electrical grid capacity in 2007 and expected to reach 160.0GW in 2010 according to World Wind Energy Association. They commence to play a vital role in the quest for renewable and sustainable energy. They are impressive structures of human responsiveness to, and awareness of, the depleting fossil fuel resources. Early generation wind turbines (windmills) were used as kinetic energy transformers and today generate 1/5 of the Denmark’s electricity and planned to double the current German grid capacity by reaching 12.5% by year 2010. Wind energy is plentiful (72 TW is estimated to be commercially viable) and clean while their intensive capital costs and maintenance fees still bar their widespread deployment in the developing world. Additionally, there are technological challenges in the rotor operating characteristics, fatigue load, and noise in meeting reliability and safety standards. Newer inventions, e.g., downstream wind turbines and flapping rotor blades, are sought to absorb a larger portion of the cost attributable to unrestrained lower cost yaw mechanisms, reduction in the moving parts, and noise reduction thereby reducing maintenance. In this work, numerical analysis of the downstream wind turbine blade is conducted. In particular, the interaction between the tower and the rotor passage is investigated. Circular cross sectional tower and aerofoil shapes are considered in a staggered configuration and under cross-stream motion. The resulting blade static pressure and aerodynamic forces are investigated at different incident wind angles and wind speeds. Comparison of the flow field results against the conventional upstream wind turbine is also conducted. The wind flow is considered to be transient, incompressible, viscous Navier-Stokes and turbulent. The k-ε model is utilized as the turbulence closure. The passage of the rotor blade is governed by ALE and is represented numerically as a sliding mesh against the upstream fixed tower domain. Both the blade and tower cross sections are padded with a boundary layer mesh to accurately capture the viscous forces while several levels of refinement were implemented throughout the domain to assess and avoid the mesh dependence.

scholarly journals A new method for measuring optical scattering properties of atmospherically relevant dusts using the Cloud and Aerosol Spectrometer with Polarization (CASPOL)

2013 ◽  
Vol 13 (3) ◽  
pp. 1345-1356 ◽  
Author(s):  
A. Glen ◽  
S. D. Brooks
Keyword(s):  
Cross Sections ◽  
Atmospheric Aerosols ◽  
Single Particle ◽  
Global Climate ◽  
Optical Scattering ◽  
Measurement Tool ◽  
Optical Signature ◽  
New Instrument ◽  
The Difference ◽  
Atmospherically Relevant

Abstract. Atmospheric aerosols have major impacts on regional and global climate through scattering and absorption of solar radiation. A new instrument, the Cloud and Aerosol Spectrometer with Polarization (CASPOL) from Droplet Measurement Technologies measures light scattered by aerosols in the forward (4° to 12°) and backward (168° to 176°) directions, with an additional polarized detector in the backward direction. Scattering by a single particle can be measured by all three detectors for aerosols in a broad range of sizes, 0.6 μm < diameter < 50 μm. The CASPOL is a unique measurement tool, since unlike most in-situ probes, it can measure optical properties on a particle-by-particle basis. In this study, single particle CASPOL measurements for thirteen atmospherically relevant dusts were obtained and their optical scattering signatures were evaluated. In addition, Scanning Electron Microscopy (SEM) was used to characterize the shape and morphology of each type of dust. The total and polarized backscatter intensities varied with particle size for all dust types. Using a new optical signature technique all but one dust type could be categorized into one of three optical scattering groups. Additionally, a composite method was used to derive the optical signature of Arizona Test Dust (ATD) by combining the signatures of its major components. The derived signature was consistent with the measured signature of ATD. Finally, calculated backscattering cross sections for representative dust from each of the three main groups were found to vary by as much as a factor of 7, the difference between the backscattering cross sections of white quartz (5.3 × 10−10 cm−2) and hematite (4.1 × 10−9 cm−2).

Correction method for the asymmetry of the tangential beam in Couette (or Searle) geometry used in rheo-small-angle neutron scattering

2004 ◽  
Vol 37 (3) ◽  
pp. 438-444 ◽  
Author(s):  
Florian Nettesheim ◽  
Ulf Olsson ◽  
Peter Lindner ◽  
Walter Richtering
Keyword(s):  
Neutron Scattering ◽  
Cross Sections ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Correction Method ◽  
Shear Cell ◽  
The Asymmetry ◽  
The Difference ◽  
Scattering Cross Sections ◽  
Final Expression

A method of correcting the asymmetry in the scattering of the tangential beam configuration in a rheo-small-angle neutron scattering experiment is proposed. The asymmetry of the scattering in the tangential beam configuration can be attributed to the difference in pathlength for neutrons that are scattered toward compared with those which are scattered away from the axis of rotation of the shear cell. The pathlength problem is solved and a final expression for the two-dimensional scattering intensity is given. The results from these calculations are compared with experimental data, which offer a different option to correct this asymmetry, namely by just measuring the scattering of H2O/D2O mixtures with absolute scattering cross sections identical to those of the respective samples. However, the situation for anisotropic media is more complex and the correction procedure described here is less effective.

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