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Certain types of [load case|kb:Load case], including [response spectrum|kb:Response-spectrum analysis] and [time history|kb:Time-history analysis], allow users to specify the direction of applied *acceleration load*, as shown in Figure 1:

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!fig 1 - angle for time history.png|align=center,border=1!

{center-text}Figure 1 - Angle specification for time-history acceleration load{center-text}

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While other types of load case, including static, [modal|kb:Modal analysis], and [buckling|kb:Buckling], provide for acceleration load along global axes, users may still apply acceleration load in an *arbitrary direction* through one of the following approaches:

* Establish an equivalent system by applying scale factors to acceleration loads oriented along global axes. For example, a resultant acceleration load 45° from the global X axis is equivalent to a UX and UY component, each scaled to 0.7071.

* Calculate and apply acceleration loads directly to the [joints|kb:Joint] of a structure, as done through the following process:
** Analyze the model, then display the assembled-joint-masses table using the Display > Show Tables > Analysis Results > Joint Output > Joint Masses > Table: Assembled Joint Masses option.
** Export this table to Excel, then, using joint mass, acceleration magnitude, and acceleration direction, calculate the acceleration-load global-axes components at each joint.
** Within a load case, apply the calculated acceleration loads using the Edit > Interactive Database Editing > Model Definition > Joint Assignments > Joint Load Assignments > Table: Joint Loads - Force option. Users may export this table to Excel, edit, then import back to the analysis software.


h1. See Also

* [Context help|doc:Context helpHelp] for acceleration-load application
* [Interactive database editing|kb:Interactive database editing]