Modeling tension-only members
Tension-only members may be modeled through the following process:
- Select all frame objects which will only carry tension.
- Set the compression limit to zero through Assign > Frame > Tension/Compression Limits.
Note that the assignment of tension/compression limits is a nonlinear analysis feature, and some applicable points, taken from Context Help, include:
- Tension/compression limits will only be activated in a nonlinear static or nonlinear direct-integration time-history analysis load case. In general, use a nonlinear analysis technique when tension/compression limits are present in the model.
- When linear analysis is performed using the initial stiffness of a member (stiffness at zero), computation will use the full axial stiffness (AE/L) as though no limits are assigned.
- When linear analysis uses the stiffness at the end of a nonlinear analysis load case, axial frame behavior depends on whether or not the tension/compression limits are exceeded at the end of the case, conditions for which are described as follows:
- Limits exceeded. Axial frame behavior is replaced with a sufficiently soft spring (1e-6*EA/L) which simulates zero stiffness.
- Limits not exceeded. The software uses full axial stiffness (AE/L) as though no limits are assigned.
- Limits exceeded. Axial frame behavior is replaced with a sufficiently soft spring (1e-6*EA/L) which simulates zero stiffness.
Tension-only members in moving-load analysis
The only method available to account for the nonlinear properties of members which are assigned tension and compression limits during moving-load analysis is step-by-step time-history moving-load analysis. Additional information is available in the Analysis Reference Manual (Step-By-Step Analysis > Time-History Analysis, page 466).
See Also
- Tension-only elements in ETABS article