Mass redistribution

The mass redistribution procedure is implemented. For time history analysis and each spectrum dynamic load case, a set of mass redistribution groups may be defined. It is possible to comply with the building code's requirements thanks to this technology, which includes taking into account the torsional effects of unknown mass locations and spatial variations in earthquake loads.

Every group has the following parameters:

• Position of the local coordinate system of the group. There are two options to define the position of this coordinate system: default and specifying the angle of rotation about the global Z-axis.
• Mass relocation along the local axis R` (Eak_R`).
• Mass relocation along the local axis T` (Eak_T`).
• A list of items to create a group.

The default position of the UCS for the group is determined in the following way:

• for single-component earthquake loads - the direction of the local X-axis is determined as the projection of the earthquake load on the XOY-plane of the global coordinate system;
• for three-component earthquake loads with radial components - the direction of the local X-axis coincides with the direction of the radial component of the earthquake load;
• for other spectral dynamic loads and time history analysis - the local coordinate system of the group coincides with the global coordinate system.

The purpose of mass redistribution is to move the centres of masses by the specified displacements, Eak_R` and Eak_T`.

Important.

The group redistributes masses obtained from loads and mass weights applied to the elements and directly to the internal nodes of the group. The internal nodes of the group are the nodes that belong only to the elements of the group. To collect the masses from the FE into the nodes of this element, a diagonal mass matrix is used, no matter what type of matrix has been specified.