Abstract
The static and seismic bearing capacity problem of shallow strip footings is investigated. Two kinematically admissible failure mechanisms M1 and M2 are considered in the framework of the upper-bound method of the limit analysis theory. The M1 mechanism is symmetrical, and it permits the calculation of the bearing capacity in the case of no-seismic loading. It is composed of a triangular active wedge under the footing and two radial shear zones composed of a sequence of rigid triangles. The M2 mechanism is nonsymmetrical and is composed of a single radial shear zone. This mechanism permits the calculation of the bearing capacity in the presence of seismic loading. Quasi-static representation of earthquake effects using the seismic coefficient concept is adopted. The solutions obtained are rigorous upper-bound ones in the framework of the limit analysis theory. The numerical results of the static and seismic bearing capacity factors are presented in the form of design charts for practical use in geotechnical engineering. These results are compared with results of other authors.
Highlights
The bearing capacity of strip footings in no-seismic areas has been extensively studied by several investigators [Terzaghi (1943), Caquot and Kerisel (1953), Meyerhof (1963), Vesic (1973), and Chen (1975) among others]
The few studies available in the literature describing the seismic effect on the bearing capacity concern the work of Meyerhof (1951) and Shinohara et al (1960). Both approaches are pseudostatic: horizontal and vertical accelerations are applied to the center of gravity of the structure and the problem is reduced to a static case of bearing capacity with inclined eccentric loads
Two computer programs using the Visual Basic programming language that resides in Microsoft Excel have been written to define the static and seismic bearing capacity factors as function of the mechanism’s parameters [(5) – (7) and (9) – (11)]
Summary
The bearing capacity of strip footings in no-seismic areas has been extensively studied by several investigators [Terzaghi (1943), Caquot and Kerisel (1953), Meyerhof (1963), Vesic (1973), and Chen (1975) among others]. The few studies available in the literature describing the seismic effect on the bearing capacity concern the work of Meyerhof (1951) and Shinohara et al (1960) Both approaches are pseudostatic: horizontal and vertical accelerations are applied to the center of gravity of the structure and the problem is reduced to a static case of bearing capacity with inclined eccentric loads. Sarma and Iossifelis (1990) and Richards et al (1993) suggested more rigorous approaches for calculating the seismic bearing capacity of strip footings in seismic areas by considering the inertia forces on all parts of the soil-structure system (soil and foundation) The theoretical approaches they used are based on the limit-equilibrium method. These solutions are rigorous upper-bound ones with respect to the exact solutions for an associated flow rule Coulomb material
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