Numerical Investigation of the Performance of Caissons in Cohesive Soils under Cyclic Loading
Publication: International Journal of Geomechanics
Volume 20, Issue 5
Abstract
Cumulative plastic deformations under cyclic loading can be a key consideration in the design of caissons and short piles. In the case of caissons and piles serving as anchors for floating offshore structures, the possibility of loss of embedment due to upward ratcheting of the anchor under cyclic loading is a particular concern. This paper presents a finite-element investigation of a caisson subjected to cyclic lateral and inclined loading. A cyclic hardening model is employed to permit simulation of cumulative plastic deformations during loading below the ultimate load state. An asymmetric Fourier analysis was employed as a highly efficient alternative to a full three-dimensional analysis, and results using the two approaches were found to be in good agreement. A realistic range of material parameters was established through back-analysis of laboratory model tests published previously. Parametric studies were performed to assess the effects of small-strain soil stiffness, subyield stress–strain behavior, load inclination, soil–pile interface adhesion, and load reversals. Pile performance for cyclic loading with nonuniform load amplitudes was also investigated. The aforementioned factors were found to have a moderate to large influence on the magnitude of cumulative displacements under cyclic loading.
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Acknowledgments
The authors acknowledge the Iraqi Ministry of Higher Education and Scientific Research and the University of Baghdad for providing support for this study. This work was also partially supported by the National Science Foundation (award number CMMI-1463431). The use of the advanced computing resources provided by Texas A&M High Performance Research Computing at Texas A&M University (TAMU) is acknowledged.
Notation
The following symbols are used in this paper:
- D
- diameter of caisson;
- E
- elastic modulus;
- Fa
- applied load;
- Fax
- applied horizontal load;
- Fax-rev
- applied horizontal load reversal;
- Fpeak
- applied peak load;
- Fult
- ultimate load capacity;
- FS
- factor of safety;
- H
- initial kinematic hardening modulus;
- L
- length of caisson;
- su
- undrained shear strength;
- t
- thickness of the caisson wall;
- ur
- cumulative resultant displacements;
- ux
- cumulative horizontal displacements;
- uy
- cumulative vertical displacements;
- α
- adhesion factor;
- αb
- back stress;
- back stress rate;
- γ
- parameter;
- plastic flow rate;
- equivalent plastic strain rate;
- ζ
- load reversal ratio;
- μ
- Poisson’s ratio;
- σ
- stress;
- σ0
- initial yield stress;
- σmax
- ultimate stress; and
- ψ
- load inclination angle.
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Published In
International Journal of Geomechanics
Volume 20 • Issue 5 • May 2020
Copyright
© 2020 American Society of Civil Engineers.
History
Received: Oct 8, 2018
Accepted: Sep 26, 2019
Published online: Mar 16, 2020
Published in print: May 1, 2020
Discussion open until: Aug 17, 2020
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