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TR.18 Inactive/Delete Specification

This set of commands may be used to temporarily inactivate or permanently delete specified JOINTs or MEMBERs.

General Format

INACTIVE { MEMBERS member-list | ELEMENTS element-list }
DELETE { MEMBERS member-list | JOINTS joint-list }


These commands can be used to specify that certain joints or members be deactivated or completely deleted from a structure. The INACTIVE command makes the members and elements temporarily inactive; the user must re-activate them during the later part of the input for further processing. The DELETE command will completely delete the members/elements from the structure; you cannot re-activate them. The Delete Joint command must be immediately after the Joint Coordinates. The DELETE commands must be provided immediately after all member/element incidences are provided and before any INACTIVE commands.


  1. The DELETE MEMBER command will automatically delete all joints associated with deleted members, provided the joints are not connected by any other active members or elements.

  2. This command will also delete all the joints, which were not connected to the structure in the first place. For example, such joints may have been generated for ease of input of joint coordinates and were intended to be deleted. Hence, if a DELETE MEMBER command is used, a DELETE JOINT command should not be used.

  3. The DELETE MEMBER command is applicable for deletion of members as well as elements. If the list of members to be deleted extends beyond one line, it should be continued on to the next line by providing a blank space followed by a hyphen (-) at the end of the current line.

  4. If inactivating members causes joints to become unconnected in space (i.e., orphaned), a warning stating that those joints are not connected by any members or elements will be displayed in the output file. These warnings can normally be ignored.

  5. The inactivated members may be restored for further processes (such as an analysis or design for a 2nd set of load cases) by using the CHANGE command. See TR.37 Analysis Specification and Example EX. US-4 Inactive Members in a Braced Frame for more information. 

  6. The DELETE MEMBER command should be used to delete elements too. Specify the command as DELETE MEMBER j, where j is the element number of the element you wish to delete. In the example shown below, 29 to 34 and 43 are element numbers.

  7. Loads that have been defined on members declared as INACTIVE members will not be considered in the analysis. This applies to SELFWEIGHT, MEMBER LOADS, PRESTRESS, and POSTSTRESS LOADS, TEMPERATURE LOADs, etc.

    For those joints that become orphaned (see note d above), loads applied to such joints, either explicitly through the JOINT LOAD command, or generated by some means as in moving, wind or seismic load generation, will be "lost", meaning, they will not get considered for the analysis for those load cases for which the associated member is inactivated.

  8. The DELETE JOINT command must be specified before all incidence commands such as MEMBER INCIDENCE, ELEMENT INCIDENCE, etc.