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This page containsis devoted to *frequently asked questions* (FAQ) related to *[time-history analysis|kb:Time-history analysis]*. analysis.
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h1
h2. What value of scale factor should beI useduse forto thedefine definition ofa the time-history load case?

*Answer:* The two options available are thedescribed followingas two possibilitiesfollows:

* When the load type is set to [load pattern|kb:Load pattern], the values of the time-history function valuesare multiplied by the scale factor areto produce unitless and terms. Here, the record should describe the variation of loads in loading over time, as applied in the [load pattern in time|kb:Load pattern].

* When the load type is set to Accel, the time-historyscale functionfactor valuesshould multipliedbe byspecified thesuch scalethat factorit shouldmultiplies bewith enteredthe suchvalues thatof theythe aretime-history equalfunction to produce the acceleration desired accelerationin inthe current units. If the values of the time-history function valuesare aregiven in the same units as the current units, thenthe scale factor ofshould 1be wouldset beto used1.0. Otherwise, the scale factor should reflect the conversion from the units of the time-history function units to the current units.
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anFor example, if the time-history data areis in cm/sec/sec units, and the current units are ft/sec/sec, then a scale factor of 0.0328 should be entered, because 1(ft) / 30.48(cm) = 0.0328 should be used.

h1
h2. What forces are included in reactions forfrom time-history analysis?

*Extended Question:* WhatAre forcesthe arereaction includedforces in the reactions that which are reported for direct -integration time-history analysis, areas theyfollows:

* structuralElastic forcesforce corresponding to= K*u
* dampingDamping forcesforce corresponding= to C*du/dt
* inertiaInertia forcesforce corresponding= to M*d^2u/dt^2
* or a combination of the above?

*Response:* The reactions included{^}2{^}u/dt{^}2{^}

*Answer:* Reactions include only the effects of onlyelastic, elasticand (orpossibly inelastic), forces, unless [links|kb:Link] are connected at the jointsto [joint|kb:Joint] locations, in which case the [damping|kb:Damping] forces fromwithin link linksobjects are also included induring computingcomputation theof joint reactions.


h1h2. What value should Ibe setspecified for the output time-step size forduring time-history analysis?

The output*Answer:* Output time-step size should be small enough to provide sufficient resolution for the analysis. The required resolution dependsis dependent onupon the characteristiccharacteristics of applied loading and alsosuch onstructural theproperties characteristicsas (suchthe as natural periods) of the structure itself. YouThe cansufficiency determineof whetherresolution themay resolutionbe is sufficientdetermined by decreasing the time-step size until theit step size is small enough thatto results are not longeraffect affectedresults.
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*What time-step size should be setspecified for input acceleration record? And what time-step size should be set for inputand displacement recordrecords?*

*Extended Question:* SayIf, thatfor theexample, analysis resolution requires a 0.005 sec005sec output time-step size., Whatwhat time-step size shouldis best befor usedeither foran input acceleration record and what time-step size should be used for input or displacement record?

*Answer:* {open-question}
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