problem description
title="Truss Sample Problem (Logan #3.42, p.123)" nodes=5 elements=4

nodes
1 x=-72 y=-36 z=0  constraint=fixed
2 x=0   y=-36 z=0  constraint=fixed
3 x=0   y=36  z=0  constraint=fixed
4 x=-72 y=36  z=0  constraint=fixed
5 x=0   y=0   z=72 constraint=free force=point_load

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

material properties
steel e=30e6 a=4

forces
point_load fx=1000 

constraints
fixed tx=c ty=c tz=c
free tx=u ty=u tz=u

end