Civil Engineering Reference
In-Depth Information
y
1
2
3
y_coords(1)
x
1
2
3
4
nxe=2
nye=2
4
5
6
y_coords(2)
dir='x'
5
6
7
8
7
8
9
y_coords(3)
x_coords(1)
x_coords(2)
x_coords(3)
Figure 5.3 Global node and element numbering for mesh of 3-node triangles
g(4)
g(2)
g(6)
g(1)
g(3)
g(5)
3
1
2
g(6)
g(4)
g(2)
g(5
)
g(3
)
g(1)
3
1
2
Figure 5.4 Local node and freedom numbering for different orientations of 3-node
triangles
displacement remains free,
and
700
means that node
7
is completely restrained. The final part of the data file refers
to loads and fixed displacement data. In this example, a uniform pressure of 1 kN/m
2
is to
be applied to the top surface of the block, which in the data file is replaced by equivalent
nodal loads. In the case of the 3-node triangle, the total force on each element is simply
shared equally between the two nodes (see Appendix A). In this case,
loaded nodes
is
read as 3, representing the nodes at the top of the block, and this is followed by the node
number and the
x
-and
y
-components of load to be applied. There are no fixed non-zero
displacements in this example, so
fixed freedoms
is read as zero.
After declaration of arrays whose dimensions are known, the program enters the “input
and initialisation” stage. Data concerning the mesh and its properties are now presented
together with the nodal freedom data as given in Figure 5.2. The total number of nodes
nn
and equations in the problem
neq
, are provided by subroutine
mesh_size
.
that at node
1
,the
x
-displacement is equal to zero while the
y
−
