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This page is devoted to *frequently asked questions* (FAQ) related to [acceleration|Acceleration].
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h2. Acceleration-load calculation

*Question:* How does [SAP2000|sap2000:home] calculate and apply acceleration load?

*Answer:* Please see the [Acceleration load|Acceleration load] article for response.


h2. Rotational-acceleration-load calculation

*Question:* What procedure does {new-tab-link:http://www.csiberkeley.com/}CSI{new-tab-link} Software use to calculate rotational-acceleration load?

*Answer:* Please see the [Acceleration load|Acceleration load] article for response.


h2. Difference between relative and absolute acceleration

*Question:* The Display > Show Plot Functions menu presents options for either _relative_ or _absolute_ acceleration. What is the difference between these options?

*Answer:* Relative acceleration is within the reference frame of the structure. Absolute acceleration is within a universal reference frame, and given as the sum of relative acceleration and ground acceleration.

The same relative and absolute designations also apply to velocity and displacement.


h2. Manual application of acceleration load

*Question:* Can acceleration loads only be applied to selected members in a model?

*Answer:* {new-tab-link:http://www.csiberkeley.com/}CSI{new-tab-link} Software automatically generates and envelopes a set of acceleration loads for translation along, and rotation about, each global axis. These acceleration loads are applied at each node and element, and used to simulate ground motion during [time-history|Time-history analysis] and translation-only [response-spectrum|Response-spectrum analysis] analyses. They are also useful as starting load vectors for [Ritz-vector|Ritz vectors] analysis.

Users may manually assign acceleration loads to specific nodes and elements. Similar to [load-case|Load case] assignment, these loads are applied through an Analysis_analysis Casecase_.