Load to Mass Conversion

Select the Load to Mass Conversion tab in the Analysis types dialog to convert static loads to masses used in dynamic calculations.

You can define loads/masses at once for all calculation purposes. It is not necessary to define separately static loads or masses taken into account in structure analyses (static and dynamic, respectively). On the basis of the pre-defined static loads one may create masses to be used during dynamic calculations.

To convert static loads to masses, do the following.

Determine the cases for which conversion of loads to masses will be carried out. Provide the numbers of load cases; define the direction of the conversion process and the multiplication coefficient to be applied to the value of the static load.
Determine the set of directions in the global coordinate system (X, Y, Z) along which the masses will operate.
Determine the analysis case that will use the masses created from loads. You can select cases from the drop-down list in the following 3 ways:
- Select single dynamic cases such as modal or harmonic analysis; masses added to the modal analysis also participate in following seismic analysis cases.
- Dynamic mass - if selected, converted masses are included in all dynamic cases.
- Global mass - if selected, converted masses are included in all dynamic cases and in the static cases for body force loads and angular acceleration forces.
Click Add.

You can also delete or modify a load case as necessary.

Concentrated forces are automatically converted to concentrated masses, distributed loads to distributed masses, and moments to rotational masses. Select Loads > Mass table to view converted masses in the table of masses. Mass values are presented in the table as weight values (acceleration of gravity is applied). Masses created due to the conversion process are marked CNV in the Memo field to differentiate them from user defined masses. The mark denotes the origin of a mass for the benefit of the conversion procedure.

Note: Conversion of loads to masses is always carried out at the beginning of calculations. It begins with the removal of the masses generated during the previous conversion. The change of the contents of the MEMO field in the table of masses may result in a mass not being removed during conversion, which leads to duplication of masses.

In the Added masses table, the Conversion of loads tab presents data concerning masses (read only and printable). Individual table columns are as follows:

Converted case - a number and a name of a converted case.
Conversion direction - depending on a selected direction X+ / Y+ / Z+ / X- / Y- / Z-.
Factor - a dimensionless coefficient.
Mass direction - X, Y or Z.
Case - a number of the modal case to which a load is converted or dynamic for all cases.

Note: For shell structures a hydrostatic pressure load cannot be converted to masses.