Analysis Wizard : Ritz Analysis

A Ritz analysis is similar to a modal analysis but is specified in terms of Ritz vectors.

Definition

Number of Ritz Vectors

The number of Ritz vectors in each of x, y and z, and thus the number of modes required from the eigenanalysis.

Maximum No. Iterations

All eigensolvers are iterative. This is used to set up the maximum number of iterations that will be allowed. It is rare that this value will need to be increased. The maximum number of iterations can also be set in the Gss Analysis Settings dialog.

Mass Option

This specifies how the mass of the elements is to be included in a dynamic analysis.A scale factor can be applied to modify the element masses. This is typically used to increase the mass to allow for connections.

Mass Derived from Loads

In addition to the mass of the elements, extra mass can be inferred from loads (Case definition) applied in a particular Direction, with a Scale factor if required. This is used where “dead loads” have been applied to the structure which represent mass in the real structure.

P-delta Case

The basis on which the geometric stiffness is calculated. This can either be a load description (e.g. 1.2L1 + 1.2L2) or an analysis or combination case (e.g. A3 or C4). When a load description is specified, GSA first analyses the structure under this load and generates a geometric stiffness from the resulting forces/moments. When an analysis or combination case is specified the geometric stiffness is constructed from the results in this analysis or combination case. Combination cases can only be simple combination cases (i.e. of the form )

This option is only present if a “Ritz p-delta” analysis has been requested.