.. _uniformExcitation:

Uniform Excitation
^^^^^^^^^^^^^^^^^^

The UniformExcitation pattern allows the user to apply a uniform excitation to a model acting in a certain direction. The command is as follows:

.. function:: pattern UniformExcitation $patternTag $dof -accel $tsTag <-vel0 $vel0> <-fact $cFact>

.. csv-table:: 
   :header: "Argument", "Type", "Description"
   :widths: 10, 10, 40


   $patternTag, |integer|, unique tag among load patterns
   $dof, |integer|, dof direction the ground motion acts
   $tsTag, |integer|, tag of the TimeSeries series defining the acceleration history.
   $vel0, |float|, the initial velocity (optional: default=0.0)
   $cFact, |float|, constant factor (optional: default=1.0)

.. warning::

   The responses obtained from the nodes for this type of excitation are **RELATIVE** values, and not the absolute values obtained from a :ref:`multiSupportPattern`. This is a consequence of the equation of motion being solved: 

   .. math::
   
	M\ddot{U} + C\dot{U} + K U = P(t)

   and how the loads are applied with this load pattern.

   .. math::

      P(t) = -c_{Fact} M l \ddot{u_g}

   where :math:`l`' is a vector of **1**'s and **0**'s, with a **1** corresponding to all matrix equations in the **$dof** degree-of-freedom direction and **0** for all other degrees-of-freedom. The :math:`\ddot u_g` is obtained from the time series.

.. admonition:: Example:

   The following example shows how to construct a **UniformExcitation** pattern with a tag of **2** acting in the **1** direction. The acceleration for the pattern comes from the :ref:`pathTimeSeries` with tag **3** which has been created using the contents of the ``elCentro.dat`` file, a :math:`\delta t = 0.02`, and a scale factor given by the variable **g**, which has been set to **386.1**.

   1. **Tcl Code**

   .. code:: tcl

      set g 386.1
      timeSeries Path 3 -filePath elCentro.dat -dt 0.02 -factor $g
      pattern UniformExcitation  2 1 -accel 3


   2. **Python Code**

   .. code:: python

      g = 386.1
      timeSeries('Path', 3, '-dt', 0.005, '-filePath', 'A10000.dat', '-factor', g)
      pattern('UniformExcitation', 2, 1, '-accel', 3)	 



Code Developed by: |fmk|