G.17.2.6 Tension- and Compression-Only Analysis
When some members or support springs are linear but carry only tension or only compression, then this analysis may be used.
This analysis is automatically selected if any member or spring has been given the tension or compression only characteristic. This analysis is an iterative analysis which continues to convergence. Any member/ spring that fails its criteria will be inactive (omitted) on the next iteration. Iteration continues until all such members have the proper load direction or are inactive (default iteration limit is 10).
This is a simple method that may not work in some cases because members are removed on interim iterations that are needed for stability. If instability messages appear on the second and subsequent iterations that did not appear on the first cycle, then do not use the solution. If this occurs on cases where only springs are the tension/compression entities, then use multilinear spring analysis.
Note: If the list of members that are to be considered as tension changes between load cases (which would be characterized with the inclusion of an additional MEMBER TENSION command with the revised member list), then this should be followed by an additional analysis command (and a CHANGE command) before starting the next load case definition.
If the list of members does not change (i.e., there is no new MEMBER TENSION command defined between these load cases), then it is not necessary to include any additional analysis and change commands, the analysis will automatically reset the axial status and iterate to solve for all the specified tension members.