This package defines the preprocessed or sliced structure model which is used for the Finite Element Analysis. It also provides the means for slicing or preprocessing the structure as it is defined in the structure package.
A sliced structure is one whose bars have been chopped into smaller finite elements where the loads originally applied in the bar are distributed in their nodes. The loads are distributed in a way such that the work done by the equivalent nodal forces equals the work done by the load.
A structure model (structure.Structure) can be sliced using the preprocess.StructureModel function.
This function is the only public function this package exports.
The result is a preprocess.Structure.
Each bar is sliced differently depending on whether it's subject to only axial stress and the loads applied to it. When a bar is an axial member, it isn't sliced at all. A bar is an axial member if the following three conditions are met:
- it's pinned in both ends,
- has no distributed loads applied to it, and
- has forces (not moments) applied only on it's nodes.
Non-axial bars are sliced according to whether they have loads applied to them or not. If they haven't got any load applied, they are sliced into a small number of finite elements. If they have loads applied to them, they are sliced into a slightly larger number of elements, plus the positions where a concentrated load is applied and the start and end positions of distributed loads. These locations in a bar's directrix are important to consider, as it's where stress discontinuities take place.