problem description
title="Displacement Boundary Condition Example" nodes=5 elements=4

nodes
1 x=0  y=0 constraint=fixed
2 x=10     constraint=free
3 x=20
4 x=30 
5 x=40     constraint=fixed_displacement

truss elements
1 nodes=[1,2] material=spring
2 nodes=[2,3]
3 nodes=[3,4]
4 nodes=[4,5]

material properties
spring A=1000 E=2000

constraints
fixed Tx=c Ty=c Tz=c
free  Tx=u Ty=c Tz=c
fixed_displacement Tx=0.02 Ty=c Tz=c

end
