COMPUTATIONAL ISSUES REGARDING LATTICE MODELS FOR WOOD

摘要

This paper describes means to overcome some of the computational issues related to lattice models. The first is the use of a solution technique, different from a Newton-Raphson approach, called the Step-Size-Control (SSC) algorithm to handle strain-softening behaviour of individual elements and to account for the possible snap-back of the load-displacement path. The second is a method to circumvent the need to recalculate the global stiffness matrix in each load step, called the Method of Inelastic Forces (MIF). Thirdly, a significant reduction in the model's degrees of freedom is achieved by using a hybrid system of lattice and solid elements, for which the lattice is only used in areas of high stress gradients. Details of these optimisations are given and their implementation is shown for a 3D example model. While the hybrid model and the MIF can be generally used and significantly reduce computational costs, the SSC routine is better suited for lattice models in which only a small number of links change to a plastic or strain-softening state.