But
===

This macro-command allows a fast and efficient post-processing calculation to determine the floor spectra of any building after a dynamic seismic analysis taking into account the interaction of the floor with the masses of the equipment (*cf.* documentation [:external:ref:`R4.05.08 <R4.05.08>`]).

For example, it can be used after a transient dynamic calculation of a building during the earthquake, transient dynamic calculation on a reduced modal basis, calculated as a relative coordinate system, or even after a non-linear transient dynamic resolution.

This macro-command executes in succession:


1. extracting the relative acceleration at one or more nodes of the mesh in the result concept (RECU_FONCTION [:external:ref:`U4.32.03 <U4.32.03>`]);


2. the combination with ground acceleration to obtain absolute acceleration (CALC_FONCTION [:ref:`U4.32.04 <U4.32.04>`]);


3. calculation of the transfer function that takes into account the interaction of the floor and the masses


4. calculating the acceleration response spectrum with several damping coefficients (CALC_FONCTION [:ref:`U4.32.04 <U4.32.04>`]);


5. Impression of floor spectra.

For practical examples of implementation, the reader can refer to the sdld109 test case [:external:ref:`V2.01.109 <V2.01.109>`].

The macro command produces a table_sdaster concept.