This dialog can be accessed from the Model > Seismic > Equivalent static / accidental torsion load menu command. This command creates a load case corresponding to either an equivalent static load or an accidental torsion load to a selected seismic code.
In many cases simplified analysis methods using equivalent static loading are used in seismic analysis. The static loading to be considered will normally be defined with reference to a design code.
In most cases a code based response spectrum is what is required, but on occasions it is useful to be able to generate a spectrum from a given time history. When selecting this option a time history must first be selected. This is a text file either in tab of comma separated form, or a PEER file.
In seismic analysis there is often a need to extract mass and (torsional) inertia data for each storey of a structure. This option looks at the structure, storey by storey, summing the mass and Izz inertia across all the nodes in that storey. The results are output to a csv file which can be opened in Excel.
In general the load curves used in seismic analysis are from reference curves or a database of ground motions. When selecting this option a time history must first be selected. This is a text file either in tab or comma separated form, or a PEER file.