The force density method for form finding and computation of general networks

A new method for network analysis, the “force density method”, is presented. This concept is based upon the force-length ratios or force densities which are defined for each branch of the net structure. It is shown that the force densities are very suitable parameters for the description of the equilibrium state of any general network: the associated node coordinates of the structure are obtained by solving one single system of linear equations. A Gaussian transformation of the topological branch-node matrix yields the equation matrix. A method based on force densities renders a simple linear “analytical form finding” possible. If the free choice of the force densities is restricted by further conditions, the linear method is extended to a nonlinear one. A damped least squares approach is then introduced. In this version the method may be applied to the detailed computation of networks. Moreover, an interesting cross-connection between geometrical minimum way nets and prestressed unloaded structures is derived using the force densities.