Back Issues 11-20

INFLUENCE OF SHEAR-BANDING EFFECTS ON THE ULTIMATE BEARING CAPACITY EQUATION OF FOUNDATIONS

Tse-Shan Hsu

President, Institute of Mitigation for Earthquake Shear Banding Disasters

Professor, Feng-Chia University, Taiwan, R.O.C., This email address is being protected from spambots. You need JavaScript enabled to view it.

Da-Jie Lin, Tsai-Fu Chuang and Yi-Min Huang

Associate Professors and Assistant Professor, Feng-Chia University, Taiwan, R.O.C.

Abstract

Previous research has shown that the sliding failure plane of foundations in terms of shear banding can only be induced by plastic strain softening. Shear banding is also considered a failure phenomenon that appears under the condition of structural instability. Based on the research results of this study, four conclusions can be drawn as follows: (1) The solution of shear bands comes from the determinant of the structure matrix being equal to zero, so it can be obtained by the finite-element method under prescribed displacements. (2) Under the condition that the initial structure is symmetric, the structure will lose its symmetry when shear bands are induced by plastic strain softening. (3) In the derivation of the ultimate bearing capacity equation of foundations, if a perfectly plastic model is adopted after setting the general shear failure plane, then a shear band is not induced and the structural symmetry is maintained, resulting in overestimation of the ultimate bearing capacity of the foundations. (4) Traditional scholars adopt the perfectly plastic model; thus, shear bands cannot be induced and the plastic zones spread to the elastic zones originally outside the shear bands, resulting in overestimation of the ultimate bearing capacity of foundations. Therefore, the authors suggest that the strain-softening model should be adopted in future studies on the ultimate bearing capacity of foundations. Design codes should also introduce the ultimate bearing capacity equation of foundations based on the strain-softening model to ensure the safety of building foundations.

Keywords: strain softening, perfectly plastic, ultimate bearing capacity, foundation, general shear failure, punching shear failure, stability, symmetry.

Attachments:

1215 Final.pdf

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2809 kB