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h2. How are tension-only members modeled during response-spectrum analysis?

*Answer:* [Tension-only|kb:Tension and compression limits tips] and compression-only behavior are nonlinear effects which should be evaluated using nonlinear [time-history|kb:Time-history analysis] analysis because. [responseResponse-spectrum|kb:Response-spectrum analysis] analysis (RSA) is a linear method which does not consider nonlinear assignments during formulation. [Links|kb:Link] arerepresent another nonlinear assignment which does not affect RSA. RSA uses effective stiffness and effective [damping, and is based on|kb:Damping] according to the stiffness used forin the corresponding [modal|kb:Modal analysis] analysis case. Stiffness may be based on zero initial conditions or that at the end of the nonlinear case. These options are shown in Figure 1:

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!Modal_load_case.png|align=center,border=0!

{center-text}Figure 1 - Stiffness{center-text}

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Nonlinear [time-history|kb:Time-history analysis] analysis should be run to consider complete nonlinear behavior.


h1. See Also

* [Tension and compression limits|kb:Tension and compression limits tips] article

* [Tension-only elements in ETABS|etabs:Tension-only elements in ETABS] article