Force density form-finding is a method of form-finding cable networks. The tension in each link of the network is made proportional to its length. The form that is found is that giving the minimum strain energy i.e. the form that minimises the sum of the squares of the lengths of the links multiplied by the stiffnesses of the links.
This can find the geometry of an artificial structure that is in equilibrium with user defined internal and external forces and constraints. There are two types of artificial structures available: soap-film structures to model membranes, and force-density structures to model cable nets.
Proceed in the same way as for a nonlinear static analysis except that the elements can have Form-finding Properties assigned as well as, or instead of, their true physical properties. The solver looks for the appropriate form-finding property for each element, and if none is defined it uses the normal property. Therefore the model can include a mixture of stiff “real” elements and form-finding elements.
Form-finding is an analysis which seeks to determine the shape of a lightweight structure under a set of boundary constraints. During a form-finding analysis with the solver will search for form finding properties with the property number assigned to the element. If none are found, the normal beam section or 2D element properties will be used instead.
Membrane geometries are defined using soap-film form-finding. In this method, all or part of the structure is modelled as having zero stiffness by assigning Soap Film Form-Finding Properties. It is useful to visualise this as making 1D elements into elastic bands, and 2D elements a soap film.