ABSTRACT
Offshore foundations are often exposed to combined vertical (V), horizontal (H) and moment (M) loading. The response of a rigid footing on sand subjected to combined loading can be represented by projections of a unique 3D interaction surface, on the V-H, V-M/B and H-M/B planes (B is width of foundation). It has been shown that the failure envelopes in V-M/B and H-M/B planes would take symmetrical parabolic forms whereas the failure envelope on H-M plane could be expressed by inclined ellipses for a single foundation on sand (see e.g. Gottardi & Butterfield, 1995). The inclination of the failure surface in
the plane implies that the horizontal/moment capacity of a shallow foundation on sand is a function of the direction of the applied moment/horizontal load for a single foundation.
