Go to the Members tab of the spreadsheet input, and go to the hinges sheet. The first field is for "Axial rigidity". Set this to tension only by selecting that option from the drop down list, or use the Ribbon menu tool "Tension only" once you have only the desired members selected.
There are three typical reasons why a tension-only member will induce bending.
When you run a P-Delta analysis, or a tension-only analysis, or compression-only analysis, each combination is solved directly. We do not use addition, or superposition, to calculate combined effects since a member that might not be in compression due to one load may be in compression due to that same load combined with another.
Under Process - Analysis - Load Conditions tab the user can select which cases or combinations to include.
RAM Instability In Finite Element Analysis
RAM Frame - Tension Only [FAQ]
Ram Elements Load Combos [FAQ]
Product TechNotes and FAQs
Structural Product TechNotes And FAQs