problem description
title="Mixed Element Sample Problem (Logan #5.10, p.189)" nodes=3 elements=2 

nodes
1 x=0 y=0 constraint=fixed 
2 x=240 y=0 constraint=free force=point_load
3 x=240 y=-120 constraint=pin 

beam elements
1 nodes=[1,2] material=steel

truss elements
2 nodes=[2,3] material=spring

material properties
steel e=29e6 ix=200 a=10
spring e=29e6 a=4.14e-3

forces
point_load fy=-2000

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

end
