====== B Command ======

B,<num>,<group>,<spgroup>,<bbc>,<force>,<end1>,<end2>

Defines a nonlinear beam and its properties for the NONLINEAR module. This command associates already defined beam element(s) with a backbone curve. This command does not make any new elements, change material, or any other properties of the beam(s) defined by other commands. 
  * num - Beam Number
  * group - beam group number for the nonlinear beam
  * spgroup - spring group number that is connected to the end of the beam
  * bbc - backbone curve used for the beam definition.
  * force - force option 
  * end1 - element at one end of the beam.
  * end2 - element at other end of the beam.