8. Tower Cable

An initially straight cable is loaded by point masses, the cable's own weight, and point masses. The static equilibrium and the eigenfrequencies around the static equilibrium are computed. This test originates from an older ADINA test case description[28] and has been converted to the MKS system of units.

The cable is prestressed with an initial stress, initial strain, or initial force (see input file cable.mdl). All 3 variants are tested, checking the final deformed position and the cable forces. The dead weights are introduced by means of point masses and referenced in the natural boundary condition case nbc 1 (file cable.mdl) with the terrestrial gravitational acceleration in the proper direction, i.e. the negative y-axis. Note that the vibration analysis case (case 2) may not reference the natural boundary condition case nbc 1, because it would re-introduce the boundary condition a second time.

The static load-displacement response of a node (node A) and the deformed configuration are shown in the figures below. Values correspond to those of the ADINA test case description.

Tower Cable: Initial (blue) and deformed position in [m] at load level 1.0. Applied forces [N] plotted in deformed configuration.

Figure 70. Tower Cable: Initial (blue) and deformed position in [m] at load level 1.0. Applied forces [N] plotted in deformed configuration.


Tower Cable: Load-displacement and load-stress curves of node A (values in [in]).

Figure 71. Tower Cable: Load-displacement and load-stress curves of node A (values in [in]).


The vibration analysis with prestress results (the equilibrium position for the load factor 1.0) are listed in the table below. To perform a restart with a given equilibrium solution the dof_init directive has to be issued to the case defining the free vibration analysis (here: case 2)

   case 2
      ...
      dof_init 'DISP.*.10.0.1'
      ...
   end

or in the command line to B2000++

prompt> b2000++ -adir dof_init=DISP.*.10.0.1 -adir case=2 DBNAME

Mode f [Hz] (B2000++) f [Hz] (ADINA, see footnote)
1 0.226 0.226



[28] K. J. Bathe; ADINA - A Finite Element Program for Automatic Dynamic Incremental Analysis; MIT Report 82448-1 (1976).