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Validity and reliability of a field technique for sweat Na+ and K+ analysis during exercise in a hot‐humid environment

Baker, Lindsay B.; Ungaro, Corey T.; Barnes, Kelly A.; Nuccio, Ryan P.; Reimel, Adam J.; Stofan, John R.
Fonte: Wiley Periodicals, Inc. Publicador: Wiley Periodicals, Inc.
Tipo: Artigo de Revista Científica
Publicado em 11/05/2014 EN
Relevância na Pesquisa
17.57%
This study compared a field versus reference laboratory technique for extracting (syringe vs. centrifuge) and analyzing sweat [Na+] and [K+] (compact Horiba B‐722 and B‐731, HORIBA vs. ion chromatography, HPLC) collected with regional absorbent patches during exercise in a hot‐humid environment. Sweat samples were collected from seven anatomical sites on 30 athletes during 1‐h cycling in a heat chamber (33°C, 67% rh). Ten minutes into exercise, skin was cleaned/dried and two sweat patches were applied per anatomical site. After removal, one patch per site was centrifuged and sweat was analyzed with HORIBA in the heat chamber (CENTRIFUGE HORIBA) versus HPLC (CENTRIFUGE HPLC). Sweat from the second patch per site was extracted using a 5‐mL syringe and analyzed with HORIBA in the heat chamber (SYRINGE HORIBA) versus HPLC (SYRINGE HPLC). CENTRIFUGE HORIBA, SYRINGE HPLC, and SYRINGE HORIBA were highly related to CENTRIFUGE HPLC ([Na+]: ICC = 0.96, 0.94, and 0.93, respectively; [K+]: ICC = 0.87, 0.92, and 0.84, respectively), while mean differences from CENTRIFUGE HPLC were small but usually significant ([Na+]: 4.7 ± 7.9 mEql/L, −2.5 ± 9.3 mEq/L, 4.0 ± 10.9 mEq/L (all P < 0.001), respectively; [K+]: 0.44 ± 0.52 mEq/L (P < 0.001)...

Experimental and theoretical modeling of DNAPL transport in vertical fractured media; Experimental and theoretical modeling of dense, non-aqueous phase liquids transport in vertical fractured media

Levy, Laurent Claude, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 2 v. (614 p.); 6654704 bytes; 6654459 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
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In recent years, groundwater contamination by dense, non-aqueous phase liquids (DNAPLs) such as chlorinated solvents and polychlorinated biphenyls (PCBs) has become an important environmental concern in many industrialized areas. Accidental spills, poor storage facilities and inadequate disposal practices are factors contributing to the release of these chemicals into the subsurface environment. The detection and presence of DNAPLs at hazardous waste sites is likely to be a significant limiting factor in the site remediation process. This is especially true for the remediation of complex subsurface formations, such as fractured bedrock. This work has developed a new model describing DNAPL infiltration into a water- saturated, vertical fracture idealized as a circular section capillary tube. A series of laboratory and geotechnical centrifuge experiments of DNAPL infiltration into vertical capillary tubes was performed to demonstrate the validity of the model, and examine the role played by capillary, gravity, viscous, and inertia forces during the infiltration process. The new model can be used to better understand the processes likely to influence DNAPL transport and remediation in real fracture systems.; (cont.) Laboratory infiltration experiments showed that the common assumption of perfect wetting at the DNAPL/water interface is incorrect. Furthermore...

Desenvolvimento de um sistema de mensuração e aquisição de dados de uma centrífuga humana

Albuquerque, Eduardo Possamai
Fonte: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre Publicador: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre
Tipo: Dissertação de Mestrado
PORTUGUêS
Relevância na Pesquisa
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Os estudos recentes mostram que em voos aeroespaciais os tripulantes sofrem com os efeitos fisiológicos resultantes da força gravitacional. Para demonstrar os efeitos causados por essa força, são utilizadas centrífugas humana. Com o objetivo de monitorar e controlar os dados emitidos por uma centrífuga humana é proposto o desenvolvimento de um sistema de mensuração e aquisição de seus dados. A centrífuga utilizada no projeto foi desenvolvida recentemente no Centro de Microgravidade – PUCRS com um orçamento de baixo custo, possuindo boa mobilidade comparada a outros modelos convencionais de centrífugas. O sistema proposto para controla-la é dividido em quatro etapas de aquisição de dados: captação, transmissão, exibição e armazenamento. As etapas de captação e transmissão são realizadas através de placas desenvolvidas no projeto e software de transmissão. Já as outras duas etapas são realizadas apenas por software. Cada uma delas compreende: controle dos dados fisiológicos, de dados gerados pela centrífuga, de dados de vídeo e o controle dos dados do ambiente. Esse sistema permite que os testes realizados na centrífuga humana tenham resultados mais precisos e ofereçam uma maior segurança para o indivíduo submetido à hipergravidade...

Desenvolvimento de uma centrífuga humana movida a exercício para treinamento de pilotos e pesquisas aeroespaciais

Albuquerque, Marcelo Possamai
Fonte: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre Publicador: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre
Tipo: Dissertação de Mestrado
PORTUGUêS
Relevância na Pesquisa
17.57%
O ser humano está adaptado a viver em uma aceleração gravitacional aproximada de 9,81 m/s², sendo ela equivalente à 1G. Caso ele sofra o efeito de acelerações de valor superior ou inferior a esse valor problemas de ordem fisiológica podem ocorrer. O agravamento desses problemas fisiológicos depende diretamente do eixo corporal afetado, a intensidade das acelerações e o tempo de aplicação das mesmas. Foguetes e aviões de caça são os equipamentos atuais que mais aplicam acelerações nocivas. Assim, para treinar a resistência do corpo humano à força G e desenvolver pesquisas na área, são utilizadas centrífugas humanas. Esses equipamentos executam movimentos circulares em torno de um eixo, produzindo uma reação inercial à aceleração centrípeta que é utilizada para simular uma força G. As centrífugas humanas vêm sendo utilizadas na fisiologia aeroespacial desde a metade do século 20. Porém, treinamentos com pilotos e pesquisas nacionais nessa área são deficitários no Brasil, uma vez que o país não possui esse tipo de equipamento. Então, para suprir essa necessidade, uma centrífuga humana foi construída no Centro de Microgravidade/FENG da PUCRS.O equipamento foi denominado Centrífuga Albuquerque e foi construído dentro de um orçamento de baixo custo...

Physical modelling of landslides in loose granular soils

Beddoe, Ryley
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
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The catastrophic consequences associated with landslides necessitate predictions of these hazards to be made with as much certainty as possible. However, the often complex nature of these events make predictions highly challenging. In this thesis, a number of hypotheses related to the triggering mechanisms and subsequent consequences of landslides in a loose-granular soil were investigated. The investigation was conducted using small-scale geotechnical centrifuge models, and a new flume facility developed to examine landslide behavior in a reduced-scale model. The first hypothesis explored in this research was that static liquefaction might preferentially occur in the saturated granular soil located at the base of the landslide rather than the well-drained inclined portion of the slope. Using a geotechnical centrifuge model, it was found that a small initial toe failure did act as a monotonic loading trigger to shear the loose contractile saturated sand at the base of the slope and caused liquefaction to occur. The second hypothesis investigated whether the consequences of a landslide triggered under elevated groundwater antecedent conditions are higher than scenarios under drier antecedent conditions. Results from five centrifuge models subjected to different antecedent groundwater conditions show that higher groundwater conditions can result in landslides with velocities about three times higher and travel distances eight times higher than low antecedent conditions. The third hypothesis investigated the influence of slope inclination on landslide consequences. Seven geotechnical centrifuge models were built and tested...

Exercise in artificial gravity

Edmonds, Jessica Leigh
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 115 p.; 6255490 bytes; 6262345 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
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Artificial gravity provided by short radius centrifugation is considered a promising countermeasure to the deleterious physiological effects of microgravity during long-duration space flight. We investigated the feasibility of dual countermeasures to address space flight deconditioning of the musculoskeletal and cardiovascular systems, by combining centrifugation with lower-body exercise. The exercise device is a small stair-stepper with constant resistance provided by dampers beneath each foot, and is the first such device to be used in centrifuge studies. We modified the existing centrifuge to support the additional stresses due to exercise and added following structural elements: support struts on the rotation shaft, a redesigned footplate to which the exercise device was mounted, and horizontal support beams. We also added a sliding mattress with linear ball bearings on rails, so that the subject's body can move up and down while stepping. Design changes and exercise feasibility were validated by having subjects exercise during centrifugation at 23 rpm. We measured heart rate, blood pressure, forces on the feet, and knee deflection due to Coriolis accelerations, for up to four subjects. As expected, heart rate and blood pressure did increase normally with exercise on the centrifuge...

Wave propagation through soils in centrifuge testing

Semblat, J. F.; Luong, M. P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/01/2009
Relevância na Pesquisa
26.88%
Wave propagation phenomena in soils can be experimentally simulated using centrifuge scale models. An original excitation device (drop-ball arrangement) is proposed to generate short wave trains. Wave reflections on model boundaries are taken into account and removed by homomorphic filtering. Propagation is investigated through dispersion laws. For drop-ball experiments, spherical wave field analysis assuming linear viscoelasticity leads to a complete analytical description of wave propagation. Damping phenomena are examined and evaluated using this description.

Continuous Centrifuge Decelerator for Polar Molecules

Chervenkov, S.; Wu, X.; Bayerl, J.; Rohlfes, A.; Gantner, T.; Zeppenfeld, M.; Rempe, G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/11/2013
Relevância na Pesquisa
26.88%
Producing large samples of slow molecules from thermal-velocity ensembles is a formidable challenge. Here we employ a centrifugal force to produce a continuous molecular beam with a high flux at near-zero velocities. We demonstrate deceleration of three electrically guided molecular species, CH$_3$F, CF$_3$H, and CF$_3$CCH, with input velocities of up to $200\,\rm{m\,s^{-1}}$ to obtain beams with velocities below $15\,\rm{m\,s^{-1}}$ and intensities of several $10^9\,\rm{mm^{-2}\,s^{-1}}$. The centrifuge decelerator is easy to operate and can, in principle, slow down any guidable particle. It has the potential to become a standard technique for continuous deceleration of molecules.; Comment: 5 pages, 4 figures; version accepted for publication in PRL

Rotational spectroscopy with an optical centrifuge

Korobenko, Aleksey; Milner, Alexander A.; Hepburn, John W.; Milner, Valery
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/09/2013
Relevância na Pesquisa
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We demonstrate a new spectroscopic method for studying electronic transitions in molecules with extremely broad range of angular momentum. We employ an optical centrifuge to create narrow rotational wave packets in the ground electronic state of $^{16}$O$_2$. Using the technique of resonance-enhanced multi-photon ionization, we record the spectrum of multiple ro-vibrational transitions between $X^3\Sigma_{g}^{-}$ and $C^3\Pi_{g}$ electronic manifolds of oxygen. Direct control of rotational excitation, extending to rotational quantum numbers as high as $N\gtrsim 120$, enables us to interpret the complex structure of rotational spectra of $C^3\Pi_{g}$ beyond thermally accessible levels.; Comment: 5 pages, 6 figures

Understanding ground deformation mechanisms for multi-propped excavation in soft clay

Lam, S. Y.; Haigh, S. K.; Bolton, M. D.
Fonte: Elsevier Publicador: Elsevier
Tipo: Article; accepted version
EN
Relevância na Pesquisa
26.88%
This is the author accepted manuscript. The final published version can be found on the publisher website at: http://www.sciencedirect.com/science/article/pii/S0038080614000286 Copyright ? 2014 Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.; Deep excavation works are carried out to construct underground infrastructures such as deep basements, subways, and service tunnels. The execution of these deep excavation works requires the use of retaining walls and bracing systems. Inadequate support systems have always been of major concern, as excessive ground movement induced during excavation could cause damage to neighboring structures, resulting in delays, disputes, and cost overruns. To gain a better understanding of the mechanisms involved in soil excavations, centrifuge model tests of deep excavations in slightly over-consolidated soft clay have been carried out using a newly developed testing system, in which the construction sequence of a multi-propped wall for deep excavations can be simulated in flight. Deformation mechanisms are observed using Particle Image Velocimetry. Settlements of the ground surface and changes in pore water pressure are monitored during the excavation. The effects of prop stiffness...

Dataset for "Interaction between surface structures and tunnelling in sand: centrifuge and computational modelling"

Giardina, Giorgia; DeJong, Matthew J.; Mair, Robert J.
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Relatório Formato: .fig, Matlab
Relevância na Pesquisa
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The article associated with this dataset can be found at http://dx.doi.org/10.1016/j.tust.2015.07.016; Raw data supporting figures in the publication: Giardina G, DeJong MJ, Mair RJ (2015) Interaction between surface structures and tunnelling in sand: centrifuge and computational modelling. Tunnelling and Underground Space Technology, 50, 465-478.; This work was supported by the EPSRC [grant number EP/K018221/1].

Centrifuge modeling of fault propagation through alluvial soils

Roth, W. H.; Scott, R. F.; Austin, I.
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /06/1981
Relevância na Pesquisa
26.88%
The behavior of alluvial deposits subjected to fault movements in the underlying bedrock is of major concern for critical structures located within fault zones. An understanding of fault propagation through soils would assist in design of such structures, but could also be utilized in geological interpretation of fault displacement history. On the premise that alluvial fault morphology contains shear patterns characteristic of modes and rates of fault displacements, a study was undertaken involving centrifugal and numerical models of reverse faulting. This paper describes the centrifuge model testing performed to backup simultaneous numerical studies (Geognosis Report, 1980), which will be described elsewhere. A comprehensive model test series under earth gravity conditions (1g) involving reverse and normal faulting under different angles has recently been undertaken by Cole (1979). However, model tests performed under 1g-conditions are limited to rather thin soil layers because of their inability to simulate realistic gravity stress conditions. Furthermore, it is not possible to simulate faulting fast enough to include inertial effects with such models.

Analysis of Centrifuge Pile Tests; Simulation of Pile-Driving

Scott, Ronald F.
Fonte: California Institute of Technology Publicador: California Institute of Technology
Tipo: Report or Paper; PeerReviewed Formato: application/pdf
Publicado em 20/06/1980
Relevância na Pesquisa
26.88%
Previous studies on the centrifuge have been directed towards simulating the behavior of a laterally-loaded pile in fine, dry and saturated sand. After data had been obtained on the model pile, attention was turned to modelling the soil-pile interaction behavior. Since the Winkler [continuous reaction elements (springs) distributed along the pile length] foundation representation is the simplest that can be adduced, and, moreover, has been found to give adequate results for design in a variety of foundation problems, attempts were made to extract a Winkler type of function from the model pile test results. The pile response is obtained from the output of a series of strain gauges attached to the pile. In effect these indicate the bending moment in the pile as a function of length along it. As a consequence, to obtain the pile-soil interaction behavior at various locations along the pile, it is necessary to integrate the bending moment function twice for each level of applied load to obtain pile displacements (the top displacement is measured and known), and to differentiate it twice, to get the soil interaction pressure. Then, at a given point on the pile, the pile-soil interaction behavior is given by plotting the pressure versus the displacement at various load levels. A series of such functions at different depths gives the information required for subsequent analyses. The troubles with this procedure are well-known. Double integration is satisfactory and gives a good indication of pile deflections...

Axially-loaded centrifuge pile tests

Christenson, John E.; Scott, Ronald F.
Fonte: California Institute of Technology Publicador: California Institute of Technology
Tipo: Report or Paper; PeerReviewed Formato: application/pdf
Publicado em 01/03/1982
Relevância na Pesquisa
26.88%
This report concerns investigations of the behavior of piles under axial loading using centrifugal modeling and t-z analysis. The results of five centrifuge model pile tests on instrumented piles are presented. The present chapter puts this work into perspective, both with relation to current practical concerns with pile performance and existing analytical techniques.

Centrifuge Studies of Cyclic Lateral Load-Displacement Behavior of Single Piles

Scott, Ronald F.
Fonte: California Institute of Technology Publicador: California Institute of Technology
Tipo: Report or Paper; PeerReviewed Formato: application/pdf
Publicado em 15/06/1978
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In the period following the completion of the previous report of December 1977 and the end of the contract on OSAPR Project 8 with California Institute of Technology, additional pile loading tests were conducted. Two different test series were followed through: additional load-unload cyclic tests again in simulation of the Mustang Island (MI) tests and pile vibration tests. The reasons for the first series were: (a) the model pile dimensions originally chosen for the Mustang Island simulation did not correctly represent either the El of the prototype pile, nor its width; and (b) it was desired to perform the tests in a soil more closely resembling the fine-grained MI sand, at higher relative densities than had been achieved in the earlier tests. It is worth pointing out here that it is not easy to produce a model pile with the correctly scaled EI, since, although the dimensions can be correctly calculated, they are based on an assumed E for the material which may be slightly different in the metal actually machined, and the strain gauges, leads and moisture-protection coating employed increase the EI in the final product. A further deficiency of the first test pile was that, although the model pile had been instrumented with 5 strain gauges...

Centrifuge studies of cyclic lateral load-displacement behavior of single piles

Scott, Ronald F.
Fonte: California Institute of Technology Publicador: California Institute of Technology
Tipo: Report or Paper; PeerReviewed Formato: application/pdf
Publicado em //1977
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A meeting was held at the California Institute of Technology, February 26, 1976, between a group representing the American Petroleum Institute (API), and Professors K. L. Lee of UCLA and R. F. Scott of Caltech. Problems relating to the dynamic performance of offshore structures were discussed, in particular with respect to their interaction with foundation soils, and the hazards related to the sliding of those soils on modest slopes. Attention was given to both wave- and earthquake-generated forces, especially on pile-supported structures, with particular consideration directed towards the latter. Although the behavior of structures at a wide variety of locations is of concern, current interest centers on those in the Arctic. The particular point of the discussion regarded current field investigations, laboratory test procedures, determination of soil material properties and behavior under cyclic or dynamic loadings, and analysis including soil-structure interactions. It is felt that improvement is needed in all these areas to improve confidence in the ability of analyses to estimate the performance of offshore structures under design loads. Field data on the performance of full-scale structures under severe loading conditions are urgently required...

Centrifuge liquefaction tests in a laminar box

Hushmand, B.; Scott, R. F.; Crouse, C. B.
Fonte: ICE Publishing Ltd. Publicador: ICE Publishing Ltd.
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /06/1988
Relevância na Pesquisa
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The difficulties associated with instrumenting earthquake sites in order to record pore pressure changes in a future event led to the use of scaled model tests performed in a centrifuge. Both dry and saturated sands were employed, contained in a box constructed of aluminium laminae designed to move freely on each other. This would result in shearing distortions developing in the soil unimpeded by the container. Accelerometers, displacement transducers and pore pressure sensors were attached to the box and embedded in the soil at various elevations so as to record the response of the soil to an earthquake-like excitation supplied to the base of the container. A special apparatus was constructed to imitate earthquake motion. In some tests on saturated sand, the soil profile was liquefied. Test results of accelerations, lateral and vertical displacements and pore pressures against time for typical earthquake inputs are given. The data, obtained under controlled conditions, can be compared with the various calculation methods for dynamically generated pore pressures.

Convection experiments in a centrifuge and the generation of plumes in a very viscous fluid

Nataf, H.-C; Hager, B. H.; Scott, R. F.
Fonte: European Geosciences Union Publicador: European Geosciences Union
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em //1984
Relevância na Pesquisa
26.88%
«Plumes» originating from unstable· thermal boundary layers have been proposed to be the preferred mode of small-scale convection in the Earth's mantle. However, doubts have been cast on the validity of the extrapolation from laboratory to mantle-like conditions. In particular, it was feared that inertial effects might be the origin of the observed instabilities. In this paper, experiments are described fbr which inertial effects are negligible. A small aspect-ratio tank filled with a very viscous fluid (Pr = 106) is used to observe the behaviour of convection for Rayleigh numbers up to 6.3 x 10^5. These high values are reached by conducting the experiment in a centrifuge which provides a 130-fold increase in apparent gravity. Rotational effects are small, but cannot be totally dismissed In this geometry thermal boundary layer instabilities are indeed observed, and are found to be very similar to their lower Prandtl number counterparts. It is tentatively concluded that once given a certain degree of «vulnerability», convection can develop «plume»-like instabilities, even when the Prandtl number is infinite. The concept is applied to the earth's mantle and it is speculated that «plumes» could well be the dominant mode of small-scale convection under the lithospheric plates.

Influência de variáveis na técnica de centrífugo-flutuação para a recuperação de ovos de Toxocara canis em solo; Influence of variables on centrifuge-flotation technique for recovery of Toxocara canis eggs from soil

Santarém, Vamilton Alvares; Magoti, Luciana Puga; Sichieri, Tathiana Dias
Fonte: Universidade de São Paulo. Instituto de Medicina Tropical de São Paulo Publicador: Universidade de São Paulo. Instituto de Medicina Tropical de São Paulo
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; Formato: application/pdf
Publicado em 01/06/2009 ENG
Relevância na Pesquisa
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Com o objetivo de avaliar a influência de variáveis na técnica de centrífugo-flutuação para a recuperação de ovos de Toxocara canis em solo, amostras de solo foram previamente esterilizadas e divididas em alíquotas de um grama e contaminadas com 200 ovos. Após contaminação, foram comparadas, em etapas seriadas, as variáveis: filtragem, tipo de lavagem e ressuspensão do material. Como ponto de partida, utilizou-se técnica com lavagem de solo em Tween 80 (0,2%) e solução de hidróxido de sódio 0,1N; ressuspensão; e centrífugo-flutuação em solução de nitrato de sódio (d = 1,20 g/cm³). Os ovos recuperados foram contados com 10 repetições e três leituras para cada repetição. A filtragem reduziu significativamente a recuperação de ovos em relação ao material não filtrado (p < 0,001), enquanto o número de ovos foi significativamente maior quando da ressuspensão do material (p < 0,05). Após padronização, as soluções de cloreto de sódio, dicromato de sódio, nitrato de sódio, sulfato de zinco, sulfato de magnésio foram comparadas. O sulfato de zinco mostrou os melhores resultados. Dessa forma, as chances de recuperação de ovos de T. canis podem ser ampliadas com um processo duplicado de lavagem do solo com água destilada e ressuspensão do sedimento...

Using small-strain stiffness to predict the load-settlement behaviour of shallow foundations on sand

Archer,A; Heymann,G
Fonte: Journal of the South African Institution of Civil Engineering Publicador: Journal of the South African Institution of Civil Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2015 EN
Relevância na Pesquisa
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Foundation settlement prediction is a challenging task due to the difficulties associated with the quantification of the soil stiffness and the abundance of available analysis methods. Of the different soil stiffness moduli that may be measured, the initial small-strain stiffness is important since it can be measured both in the field and the laboratory, and settlement prediction methods using this parameter are becoming more common. The objective of this paper is to present a settlement prediction method for shallow foundations that only uses small-strain stiffness as input parameter. The method was developed by conducting physical modelling in the geotechnical centrifuge at the University of Pretoria to quantify the behaviour of shallow foundations on sand. Bender and extender elements were used to obtain the small-strain stiffness profile below the foundation before it was vertically loaded and the load-settlement curve determined. The tests were conducted on different density sands corresponding to loose, medium-dense and dense sand. A non-linear stepwise analysis approach was used in conjunction with a softening function, with variables calibrated to obtain the best fit solution for the different sand densities. Results indicate that the accuracy of the proposed method decreases as the sand density increases...