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Civil-Comp Proceedings
ISSN 1759-3433 CCP: 80
PROCEEDINGS OF THE FOURTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: B.H.V. Topping and C.A. Mota Soares
Paper 122
Numerical and Physical Modelling of the Uplift Behaviour of Strip Anchors in Cohesionless Soil E.A. Dickin+ and M. Laman*
+Department of Civil Engineering, University of Liverpool, United Kingdom
Full Bibliographic Reference for this paper
E.A. Dickin, M. Laman, "Numerical and Physical Modelling of the Uplift Behaviour of Strip Anchors in Cohesionless Soil", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Fourth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 122, 2004. doi:10.4203/ccp.80.122
Keywords: strip anchors, uplift response, finite element, non-linear analysis, centrifuge, sand.
Summary
Anchor plates are light structural members often employed to withstand uplift forces
experienced, for example, by transmission towers, masts and structures subject to
buoyancy. A number of conventional laboratory-based studies have been reviewed
by Frydman and Shaham [1] and provide experimental evidence of the influence of
geometry and depth of embedment on the uplift behaviour of anchor plates. A
centrifuge study reported by Dickin [2] simulating the behaviour of 1m wide anchor
plates also demonstrated the influence of anchor size. Anchor plates with a range of
geometries and embedment ratios were investigated and empirical shape factors
proposed. Comparisons were drawn with a number of limit state and finite element
based design methods
The purpose of the research reported herein was to compare computations using PLAXIS with results from the centrifuge modelling programme. PLAXIS is a finite element package specially developed for the analysis of deformation and stability in geotechnical engineering projects (Brinkgreve and Vermeer [3]). An elasto-plastic hyperbolic model, the so-called Hardening Soil Model (HSM), was used for the non- linear sand behaviour in this study. When subjected to primary deviatoric loading, sandy soil shows a decreasing stiffness and simultaneously irreversible plastic strains develop. The observed relationship between the pressure and axial strain can be well approximated by a hyperbola as used in the variable elastic, hyperbolic model (Duncan and Chang [4]). The HSM, however, far supercedes the hyperbolic model and is capable of simulating nonlinear, inelastic, stress dependent material behaviour.
Limiting states of stress are described by means of the friction angle (
PLAXIS incorporates a fully automatic mesh generation procedure, in which the
geometry is divided into elements of the basic element type and compatible
structural elements. The strip anchors were represented by a rigid beam element with
soil interface parameters generated using an interaction coefficient The load-displacement relationships from the PLAXIS analyses generally showed good agreement with observed behaviour in the pre-peak region for all anchor depths. Anchors with embedment ratios of 3 and 7, considered as typical examples of shallow and intermediate depth anchors, were given particular attention. The change in response in the soil above a strip anchor, which is dependent on its embedment, was also reflected in the displacement contours obtained from PLAXIS. It may be concluded that the pre-peak uplift behaviour of strip anchors can be sensibly modelled by the Hardening Soil Model available in PLAXIS although the post-peak softening phase observed in some physical model tests requires a more sophisticated soil model. References
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