Numerical studies of the moment carrying capacity of a short pier foundation in a clay soil

Numerical predictions of the immediate moment carrying capacity of a short pier foundation in saturated clay are presented. Three-dimensional finite element analyses are carried out using linear and non-linear programs and using a linear axi-symmetric program. Preliminary investigations are made to determine suitable boundary distances for analysis at full-scale and size of loading increment for non-linear analyses. Predictions of the behaviour of prototype pier and of conventional and centrifuge models of this pier are then made. It is shown that the axi-symmetric program yields significantly higher rotations per unit moment than the linear three-dimensional program and that, using both of these programs, elastic analyses of the conventional and centrifuge models and of the prototype yield very similar results. It is also shown that non-linear analyses of the conventional and centrifuge models yield significantly different moment/rotation relationship in accordance with the behaviour actually observed in the model tests. The relationship obtained for the centrifuge model is shown to differ only slightly from that obtained for the prototype, due to the boundary restrictions in the model, and to be of the same order as the centrifuge test result at working condition but not at ultimate capacity

Three-dimensional finite element studies of the moment-carrying capacity of short pier foundations in cohesionless soil

This study is concerned with the moment-carrying capacity of short pier foundations in loose and dense cohesionless soil. The results of non-linear three-dimensional finite element analyses are compared with data from centrifuge tests modelling the behaviour of 1 m diameter prototype piers. The numerical predictions are shown to be very sensitive to the value of coefficient of earth pressure at rest, K0, and most closely match observations when K0 = 0.6 is assumed. The results of parametric studies of square prototype piers in loose and dense cohesionless soils are then presented. Empirical equations are derived between moment-carrying capacity and pier geometry, for limiting pier rotations of 1°and 2°, and very close fits are demonstrated between the values given by these equations and the original computed values.University of Liverpool NATO-B2The research presented in this paper was performed at the University of Liverpool while the first writer was supported by a “TUBITAK, NATO-B2” Scholarship awarded by the Technical Research Council of Turkey

Some applications of the finite element method in soil mechanics

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