$
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$
$
$     ----------     Flag Pole With Generalized DOF    ---------
$                                                file 4
$
$ This is the last in a series of samples which deals with a "flag pole".
$ The pole is almost a cantilever beam. It is a set of 10 beam elements
$ which are pinned at the first and second nodes.
$
$ This sample, tries to solve this problem badly. We compute the modes
$ in air and we do not use the proper boundary conditions. We then place
$ it in water connect the system, use two modes as generalized DOFs,
$ and compute raos with and without a top weight.
$
$ The results here are not at all similar to the "correct" results found
$ previously. The reason is simply that using only the first two modes
$ does not provide a "reasonable" representation of the deformation
$ required to satisfy the boundary conditions.
$
$ Finally, we use 10 modes and compute the RAOs. In contrast to using
$ 2, these results are reasonably similar to the "correct" ones. The
$ only real problem is that where the others had a single peak, These
$ have a "double peak" in the neighborhood of where a single peak
$ should be. This is simply a result of having to use a combination of
$ modes to get to reasonance.
$
$ The primary point here is that you can get reasonable answers to
$ problems provided: you use enough modes to "capture the deformation
$ of the system being modeled", and you can compute these modes in
$ any condition. In other words, MOSES will properly account for
$ mass and stiffness changed as the body moves through space.
$
$
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$
$
$*********************************************      basic parameters
$
&dimen -dimen meters k-nts
&device  -g_default device -oecho no -auxin f_pole.dat
&title Flag Pole - Modes Computed in Air - No Weight - Bad B.C.
$
$*********************************************      read model
$
inmodel
&apply -perc @ 0 f_pole 100
$
$*********************************************      estimates
$
&set num_mode = 20
e_estimate
$
$*********************************************      set configuration
$
&instat -locat 0 0 +100
$
$*********************************************      get modes
$
struct -init
   modes -num_ev %num_modes%
end
strpos
   modes value
   &loop i 1 %num_mode%
      &set cname = M0@0%i%
      modes vector -load %cname%
   &endloop
end
$
$*********************************************      put in water
$
&instat -locat 0 0 00
$
$*********************************************      define connections
$
medit
   connector c1 ~spr1 *1
   connector c2 ~spr2 *3
end
&equi
&stat force
&event_store 1
$
$*********************************************      loop num modes
$
&loop nuse ( 2 %num_mode  )
$
$*********************************************      use modes
$
&describe body f_pole -gen 1:%nuse
&apply -perc @ 00
&equi
&stat motion
&stat force
$
$*********************************************      raos
$
&apply -perc @ 100  -force @ 100
&equi
&stat motion
&stat force
freq_resp
    mor_work %twei -nonlin
    rao -heading 0 -period %liste%
    &subt Motion of Node *%n_nodes% - With Weight - N Modes = %nuse
    fr_poin *%n_nodes%
       report
       add_col Energy -inpu %l_drao
       plot 2 3 15 -t_left 'X Motion RAO (m)' \
                   -t_x    'Period (Seconds)'  \
                   -legend 1 'Moses '         \
                   -legend 2 'Energy Estimate'
       end
end
$
$*********************************************      end loop
$
&endloop
$
$*********************************************      all done
$
&fini