The cosine time history function is a periodic function. A cosine function cycle starts at its positive maximum value (positive value of amplitude), proceeds to a value of 0, continues to its negative minimum value (negative value of amplitude), and returns to a value of 0 again.
Time History Function Name edit box. Use the default or specify another name for the time history function by typing directly in the edit box.
Parameters area.
Period edit box. Enter the period of the cosine function. It is the time in seconds that it takes for the function to complete one cycle.
Number of Steps per Cycle edit box. Enter the number of steps, that is, function value points, provided for each cycle of the function.
Number of Cycles edit box. Enter the number of cycles in the function.
Amplitude edit box. Enter the maximum function value of the cosine function.
Define Function area. This area displays the period and spectral acceleration values for the function. They cannot be edited and are provided for review purposes only. These values update when changes are made to the items in the Parameters area of the form. If manual changes to the Period and Acceleration values are necessary, click the Convert to User-Defined button to convert the function to a user-defined function, which will make the values editable.
Function Graph area. This area displays a graph of the function. It updates automatically as additional points are defined for the function. In some cases it may be necessary to click the Display Graph button after making changes to the form to display or update the graphical display.
Run the mouse pointer over the function graph and a dot appears along the line representing the time history function. The coordinates of the dot are reported in the box just below the graph.
Access the Time History Function Definition - Cosine form as follows:
Click the Define menu > Functions > Time History command to access the Define Time History Functions form. Then do one of the following:
Select Cosine from the Choose Function Type to Add drop-down list; click the Add New Function button.
Highlight an existing Cosine function definition in the Functions display area and click the Modify/Show Spectrum button.