Restraints

The boundary conditions of a model are defined in the Restraints module, where all structural nodes are listed and available for selection and restraining against deformation in any of the six degrees-of-freedom.

When carrying out 2D analysis, it might be useful to restrain all out-of-plane degrees-of-freedom, so as to minimise running time. Hence, and as an example, for a model defined and responding in the x-z plane (2D models created with the wizard feature are defined in this plane), all nodes should possess y+rx+rz restraining conditions. Note that for this common type of situations (y=0, and y+rx+rz restrained for all the nodes) the y+rx+rz restraints are not shown on the 3d plot, for reasons of clarity.

The modelling of foundation flexibility can be accomplished through the use of link elements, the first structural node of which is restrained in all directions (x+y+z+rx+ry+rz), whilst the second is connected to the structure. Any of the currently available response curves can then be employed to model the elastic or inelastic response of the soil in each of the six degrees-of-freedom.

Notes

1. In order to model yield penetration at the base, when present, it suffices to increase the length of the corresponding column element by the adequate amount. Refer to the available literature for indications on how to compute such yield penetration length [e.g. Paulay and Priestley, 1992; Priestley et al., 1996].
2. Copying&pasting of data is not possible in this module.