摘要:

AbstractA finite element method for simulating excavation in elastoplastic soils which produces a ‘unique’ solution for any number of excavation stages is presented. The proposed method satisfies the uniqueness principle for elastic materials postulated by Ishihara,1and degenerates to the methods presented in the ADINA code2, 3and by Brown and Booker4and Ghaboussi and Pecknold5for the simple elastic cases. The non‐linear (elastoplastic) finite element equations are derived from a variational formulation which accounts for time‐varying problem domain and boundaries. The roots of these non‐linear equations are solved by Newton's method, using the notion of the consistent tangent operator proposed by Simo and Taylor6in conjunction with a numerical algorithm based on the ‘radial‐return’ concept for integrating stresses.7–9Numerical examples demonstrate that in the elastic case the solution to problems involving a ‘shrinking’ (excavation) or ‘expanding’ (fill) domain is superposable and does not depend on the number of construction stages. For a monotonically shrinking elastoplastic domain and the von Mises and Drucker—Prager yield models, it is shown that the proposed method also produces a ‘unique’ solution independent of the number of excavation stages. Finally, the asymptotic quadratic convergence exhibited by the proposed method is demonstrated to show the efficiency engend

ISSN:0363-9061    

DOI:10.1002/nag.1610130302

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe consolidation of a porous saturated sphere under an isotropic pressure, and free to drain on its surface, is examined. It is shown that a Mandel—Cryer effect develops irrespective of the magnitude of the strains which occur. Surprisingly, the effect is found to be virtually independent of strain. However, the progress of consolidation is substantially faster in the presence of large strain

ISSN:0363-9061    

DOI:10.1002/nag.1610130303

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper describes a technique for computing rigorous upper bounds on limit loads under conditions of plane strain. The method assumes a perfectly plastic soil model, which is either purely cohesive or cohesive‐frictional, and employs finite elements in conjunction with the upper bound theorem of classical plasticity theory.The computational procedure uses three‐noded triangular elements with the unknown velocities as the nodal variables. An additional set of unknowns, the plastic multiplier rates, is associated with each element. Kinematically admissible velocity discontinuities are permitted along specified planes within the grid. The finite element formulation of the upper bound theorem leads to a classical linear programming problem where the objective function, which is to be minimized, corresponds to the dissipated power and is expressed in terms of the velocities and plastic multiplier rates. The unknowns are subject to a set of linear constraints arising from the imposition of the flow rulé and velocity boundary conditions. It is shown that the upper bound optimization problem may be solved efficiently by applying an active set algorithm to the dual linear programming problem.Since the computed velocity field satisfies all the conditions of the upper bound theorem, the corresponding limit load is a strict upper bound on the true limit load. Other advantages include the ability to deal with complicated loading, complex geometry and a variety of boundary conditions. Several examples are given to illustrate the effectiveness of the proce

ISSN:0363-9061    

DOI:10.1002/nag.1610130304

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA simple and efficient method for the solution of uncoupled transient thermoelastic problems using boundary integral techniques is presented. The method employs a Laplace transformation to remove temporarily the time dependence of the governing equations. Numerical analysis is then carried out in the transform space, and results in the time‐position space are found by numerical inversion of the Laplace transform. The method has the advantage that it avoids time‐stepping and the costly evaluation of domain integrals. Boundary element and analytic solutions are compared, and the effect of cooling on the stresses around a deep underground opening is exami

ISSN:0363-9061    

DOI:10.1002/nag.1610130305

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe relation between the hypo‐elastic constitutive law and Mehrabadi and Cowin's dilatant double‐sliding model for cohesionless granular materials is studied. Conditions that must be satisfied by hypo‐elastic analogues of the double‐sliding model are derived constructively, and a simple example i

ISSN:0363-9061    

DOI:10.1002/nag.1610130306

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA finite element model is proposed for studying the seismic response of a flexible retaining wall/soil system. The model accounts for nonlinear hysteretic soil behaviour, and also for the increase in lateral stresses and settlement related to grain slip caused by cyclic loads. The response computed by the proposed method was compared with responses recorded at the Cambridge centrifuge facility, and found to be in reasonable agreement. The model was then used to identify the importance of factors such as flexibility of the wall and relative density of the backfill. The study reveals that the maximum bending moments given by current design procedures are nonconservative for stiffer walls. Deflections of flexible walls are of major concern. Flexible walls supporting a sand of medium density yield the greatest deflection.

ISSN:0363-9061    

DOI:10.1002/nag.1610130307

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe subject paper1details finite element analyses of underreamed footings installed at the tips of deeply embedded pipe piles. The analysis model incorporated a double‐hardening constitutive law and was calibrated using extensive field and laboratory test results. The results of the study were used to judge the relative effects of various aspects of the design, such as partial drainage and layering. Ultimately, this analysis was used to assess the adequacy of the footings as a remedial strengthening measure for a major offshore platfor

ISSN:0363-9061    

DOI:10.1002/nag.1610130308

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractIt is shown that a finite element calculation which approximates an ‘infinite medium’; problem by a mesh with finite boundaries will yield greater accuracy when stress boundary conditions are applied on the far‐field boundary than is obtainable with displacement boundary conditions. In particular, with Poisson's ratio close to 0.5, the accuracy of the latter model isseverelyimpaired, whereas the stress boundary condition model is unaffected for Poisson's ratio of 0.49 and a reasonable mesh. The eight‐node quadratic isoparametric element displays superb accuracy for the axisymmetric thick cylinder with either type of boundary co

ISSN:0363-9061    

DOI:10.1002/nag.1610130309

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0363-9061    

DOI:10.1002/nag.1610130310

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0363-9061    

DOI:10.1002/nag.1610130311

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY