ZPA (Reg. Guide 1.60/UBC - g's) <or> # Time History Output Cases - CAESAR II - Help

CAESAR II Users Guide

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CAESAR II
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CAESAR II Version
13

(Available for: Spectrum/1.60/UBC and Time History)

Specifies an acceleration factor or distinct times as described below. The usage of this parameter varies with the analysis type.

Normalized Response Spectra

For specific pre-defined normalized response spectra, this value is the acceleration factor (in g's) by which the spectrum is scaled. For example, when a spectrum analysis uses one of the pre-defined spectra names beginning with "1.60" (such as 1.60H.5 or 1.60V7), CAESAR II constructs an earthquake spectrum according to the instructions given in USNRC (formerly USAEC) Regulatory Guide 1.60. This guide requires that the shape of the response spectrum be chosen from the curves shown in the following figures, based upon the system damping value. The last number in the default CAESAR II spectrum name indicates the percent critical damping. For example, 1.60H.5 indicates 0.5% critical damping, while 1.60V7 indicates 7%. If the analysis uses one of the pre-defined spectra names beginning with "UBC" (such as UBCSOIL1), CAESAR II uses the normalized seismic response spectra for the corresponding soil type from Table 23-3 of the Uniform Building Code (1991 Edition). Reg Guide 1.60 and the UBC curves are normalized to represent a ground acceleration (ZPA or zero period acceleration) of 1g. The true value is site dependent. Therefore, using the ZPA value appropriately scales any Regulatory Guide 1.60 or the Uniform Building Code response spectra.

Time History Analysis

For a time history analysis, this value is the number of distinct times at which the results of the load cases (the dynamic load as well as all static/dynamic combinations) are generated. In addition, CAESAR II generates one set of results for each load case containing the maximum of each output value (such as displacement, force, or stress) along with the time at which it occurred. The times for which results are generated are determined by dividing as evenly as possible the load duration by the number of output times. For example, if the load duration is one second and five output cases are requested, results are available at 200, 400, 600, 800, and 1000 milliseconds, in addition to the maximum case. The total number of results cases generated for an analysis is the product of the number of load cases (one dynamic case plus the number of static/dynamic combination cases) times the number of results cases per load (one maxima case plus the requested number of output cases). The total number of results cases is limited to 999:

(1 + # Static/Dynamic Combinations) x (1 + # Output Cases) £ 999

At least one output case, in addition to the automatically generated maxima case, must be requested. More than one is not necessary, because the worst case results are reflected in the maxima case and individual results at every time step are available through the ELEMENT command when animating time history results.