In STAAD, there are 2 methods for handling cables:
1) By using the MEMBER TENSION command in conjunction with the MEMBER CABLE command
This method works satisfactorily as long as the cables do not go into compression. Once they go into compression, they have to be switched off, their initial tension has to be removed from the loading matrix and the remaining structure has to be re-analysed. Versions of STAAD prior to STAAD.Pro 2006 Build 1004 do not properly handle the portion that involves removing the initial tension. Hence, if there is an initial tension on cables which eventually go into compression, the results will be approximate or inaccurate.
You can find a description of this method under section "1.11.1 - Linearized Cable Members" of the STAAD.Pro Technical Reference manual.
2) Non-linear cable analysis. The description of this method is available in the following sections of the STAAD.Pro Technical Reference manual
- AD.2007-10.2 ,
You are using the 1st option mentioned above. Thus, you need to use MEMBER TENSION command in conjunction with the MEMBER CABLE