Data part, geometry of edges

start_define
bottom_edge geometry_line 1
end_define

start_define
right_edge geometry_line 2
end_define

start_define
left_edge geometry_line 3
end_define

We want to specify the edges at which boundary conditions are imposed later. Each edge will be specified by a geometry_line data record, since the edges are straight lines. It is convenient to define a name for each edge, so that later that name can be used when needed and the input file remains more readable. Each start_define ... end_define specifies a word, by example bottom_edge which will be later substituted with its real meaning, by example geometry_line 1. Such defines can be used for all kinds of input.

bottom_edge 0.0 0.0 60.0 0.0 0.01
left_edge 0.0 0.0 0.0 15.0 0.01
right_edge 60.0 0.0 60.0 5.0 0.01

The first line bottom_edge 0.0 0.0 60.0 0.0 0.01 is read by Tochnog as geometry_line 1 0.0 0.0 60.0 0.0 0.01, so in fact geometry_line 1 is specified. The other two lines specify geometry_line 2 and geometry_line 3. The $0.01$ indicate the tolerance of the lines; all nodes in the model with a distance not more than $0.01$ are considered to be located on the geometrical lines.

Notice that we identify each geometry_line by a unique index; for the present geometry lines the indices 1, 2 and 3 are used. In fact, most of the data in the input file uses an index, by example element data records use an index which is the element number, node data records use an index which is the node number, etc.