C modeling
==============

Characteristics of modeling
-----------------------------------

This modeling validates the use of dynamic substructuring for modal analysis. It compares a modal calculation by dynamic substructuring with a "direct" calculation (without dynamic substructuring).

In addition, option ACCE_ABSOLU is also validated for single-press spectral modal calculation.

Tested sizes and results
------------------------------

Modal calculation: pipe line frequencies
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The first 14 natural frequencies of the pipe are tested and the results of the calculation by dynamic substructuration are compared with those of the reference [:ref:`1 <1>`].

.. csv-table::

    "**Clean Fashion**", "**Reference**
    **Frequencies (Hz)**", "**Tolerance**
    **Aster_Code (%)**"
    "**1**", "2.91", "1"
    "**2**", "4.44", "2"
    "**3**", "4.86", "1"
    "**4**", "5.02", "1"
    "**5**", "6.95", "1"
    "**6**", "7.58", "2"
    "**7**", "7.82", "1"
    "**8**", "10.94", "1"
    "**9**", "11.65", "2"
    "**10**", "11.78", "2"
    "**11**", "12.80", "2"
    "**12**", "14.32", "2"
    "**13**", "15.17", "6"
    "**14**", "15.79", "4"



Seismic response by spectral calculation
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We create the same table for the absolute accelerations:

.. csv-table::

    "**Knot**", "**Max absolute acceleration in** :math:`\mathit{DX}`
    **("direct" calculation)**", "**Tolerance (%)**"
    ":math:`N10` ", "227,616 inches/s²", "0.2"
    ":math:`N20` ", "285.906 inches/s²", "3.0"
    ":math:`N30` ", "177.284 inches/s²", "4.0"