'grpa'This command allows to assign elements to a group. The group number is an element attribute used in the frd file. That way the user can read an result file, define groups and store the results together with group-definitions for further use in case no ccx input file is available. One element can only belong to one group. This command assigns a group number to certain elements stored in a given set. See “Element Definition Block” how this applies to the result format (frd).