Three-Dimensional Modelling of Foundations under Combined Loading

1. z y Wave Load Direction x G.T. Houlsby (Oxford University) and M.J. Cassidy (The University of Western Australia) Three-Dimensional Modelling of Foundations under Combined Loading This research is sponsored by the ARC as part of an IREX exchange programme between Oxford University and The University of Western Australia Motivation Examples THEORY The theoretical models are based on work-hardening plasticity theory, and have four main components. The new features for the three-dimensional models are high lighted. Purpose: to develop realistic models for shallow foundations for offshore structures when subjected to combined loads in three dimensions A B A C B D C Elasticity: dimensionless stiffness factors are defined, depending on the footing geometry D The effects of horizontal loads in different directions can be studied Applications are to jack-up structures and to caisson foundations, for example for offshore wind turbines Yield surface: a yield surface is defined in terms of dimensionless variables in 6-dimensional stress space Forces in 3 directions and moments about 3 axes are taken into account Foundation model placed at the bottom of each leg Hardening law: this defines the relationship between the size of the yield locus and the penetration of the footing into the soil Flow rule: The foundation models use “non-associated” flow rules to ensure that the ratios between the plastic displacements are realistic The effects of skewed environmental loading on three dimensional structures can be studied Different geometries of foundations can be defined Visit us at www-civil.eng.ox.ac.uk or www.cofs.uwa.edu.au