.. _HowToMRS-label:

====================
How to MRS analysis
====================

Introduction
============
This guide explains how to carry out Modal Response Spectrum (MRS) analysis using viiapackage and rhdhv_fem package. The
guide also demonstrates which items should be checked once the analysis has been created and run is complete.

Prerequisite before MRS
=======================

Input number of modes
---------------------
Before an MRS analysis can be created, first prerequisite is to have validated A3 - Fixed Base Eigenfrequency analysis
or A7 - Flex Base Eigenfrequency Analysis. Once eigen frequency analysis has been run successfully, go to corresponding
eigen frequency analysis results folder and open the .out file. In X- and Y- direction, check for the mode number at
which cumulative modal mass participation percentage is just above 70%. Note down higher of the two mode numbers in X-
and Y- direction. This will be used as input during creation of MRS analysis.

For example, in the figure below modal mass participation in x- and y-direction, respectively, are shown for an object.
For x-direction the 70% cumulative is reached at mode 6 while in Y-direction this is reached at mode 22.

.. figure:: _static/howto_mrs/ModalMass70X.png
   :align:   center

.. figure:: _static/howto_mrs/ModalMass70Y.png
   :align:   center

The higher of the two modes is selected for MRS analysis, 22 in case of above situation.

Make sure to convert all imposed load to dead load using project.viia_convert_imposed_loads_to_self_weight().

Creating MRS analysis
=====================
To create MRS analysis use the following syntax:

.. code-block:: python

    import viiaAnalysis project.viia_create_loads(load='MRS_loads')
    project.viia_create_load_combination_response_spectrum()
    project.viia_analysis(analysis_nr='A5', run=True, nmodes=22)

The value of n_modes in the present case is taken as 22 (higher of X- and Y- direction modes at which mass participation
crosses 70%). This value will vary from object to object, check A3-/A7- analysis out file. If due to some reasons,
70% cumulative participating modal mass is not reached, run A3-/A7- again and request more modes.

Loads and Analysis
==================
If everything was properly set up, Geometry > Loads > Cases will look something like this.

.. figure:: _static/howto_mrs/geometryLoads.png
   :align:   center

and in the analysis tab, a new analysis 'A5 - Modal response spectrum analysis' would have been created.

.. figure:: _static/howto_mrs/analysisMRS.png
   :align:   center

Checks before running MRS analysis
==================================
Check the following things before you run your MRS analysis.

Check 1
-------
Check if eigen frequencies are correctly considered in the analysis.

.. figure:: _static/howto_mrs/consideredFrequencies.png
   :align:   center

Check 2
-------
Go to 'Output response spectrum analysis' tab

.. figure:: _static/howto_mrs/outputMRS.png
   :align:   center

and check whether the considered load case is set to corresponding dead load case in your analysis.

.. figure:: _static/howto_mrs/staticLoadMRS.png
   :align:   center

MRS analysis is ready for run.