When an element (usually spring) is deactivated, the structural system changes, therefore the results stored in the particular summation load cases are not correct anymore, since their results derive from the former statical system. In order to correct them to be in accordance with the actual system, the forces in the removed elements stored in a certain summation load case have to be brought back upon the structure with negative sign and then added to this summation load cases in accordance with the normal rules of statics.
This is accomplished by defining and calculating a respective correction load case (type "DEMO", menu Actions on element end / Element removal).
A load case of this type has to be defined for all summation load cases which contain results of the removed spring element (most commonly SW-SUM, PT-SUM, CS-SUM, SDL-SUM).
In the following the procedure is explained exemplary for SW-SUM.
In the top window the name of the load case (e.g. DEMO-1201-SW) has to be entered. In the usual way the label for the load management (SW) defines to which summation load case the results of the given load case should be added.
In the bottom window for each removed element (e.g. spring) the summation load case from which the stored results of this element should be taken and used as loading must be given. In addition one can initialise (set to zero) the results of the removed element in the particular summation load case by choosing the respective option – this is just a formal act depending on whether the user wants to see the former results stored in the removed spring element even after removal or not. However if the removed spring should be activated again in a later stage, it is essential to initialize its results.
Note that the total stage summation load case (STG-SUM) is adjusted “automatically” when performing the calculation for all partial summation load cases due to the assignment of the particular labels and load management definitions, as for example the calculation of DEMO-1201-SW (with the given label SW) will add the corresponding results to SW-SUM and STG-SUM at the same time.
(If however one wishes to initialize the results of the removed elements also in the stage summation load case (STG-SUM), a “dummy” load case (DEMO-1201-SUM-INIT) has to be generated and calculated for this, at which the option “Initialize…” is activated).