Static and seismic bearing capacity of shallow strip footings

• Seismic bearing capacity of shallow strip footings was studied.
• Soil and superstructure inertia effects on bearing capacity were evaluated separately.
• Smooth and rough footings were considered.
• The effect of vertical seismic acceleration was investigated.
• Empirical formulae of practical use were provided.

In this study, the evaluation of static and seismic bearing capacity factors for a shallow strip footing was carried out by using the method of characteristics, which was extended to the seismic condition by means of the pseudo-static approach. The results, for both smooth and rough foundations, were checked against those obtained through finite element analyses.Under seismic conditions the three bearing capacity problems for Nc, Nq and Nγ were solved independently and the seismic bearing capacity factors were evaluated accounting separately for the effect of horizontal and vertical inertia forces arising in the soil, in the lateral surcharge and in the superstructure.Empirical formulae approximating the extensive numerical results are proposed to compute the static values of Nγ and the corrective coefficients that can be introduced in the well-known Terzaghi׳s formula of the bearing capacity to extend its applicability to seismic design of foundations.