Response Spectrum Definition - User Definition

Use the Response Spectrum Function Definition form to define a response spectrum based on user specified parameters.

• Function Name edit box.  Use the default or specify a new name for the response spectrum function.

• Function Damping Ratio edit box . Use the default or specify the damping ratio that will be used to generate the response spectrum curve. During analysis, the response spectrum curve will be automatically adjusted from this value to the actual damping present in the model.

• Defined Function area

• • Add button

  • 1. Type the first set of period and spectral acceleration values into the Period and Value edit boxes at the top of this area.

    2. Click the Add button.

    3. Type in the next set of  values and again click the Add button. Continue this process until all sets of values have been entered.

  • Modify button.

  • 1. Highlight the values to be modified in the list box. Note that when highlighted, they appear in the Period and Value edit boxes at the top of the area.

    2. Modify the values in the edit boxes.

    3. Click the Modify button.

  • Delete button.

  • 1. Highlight the appropriate values in the list box.

    2. Click the Delete button.

  • Function Graph area. This area displays a graph of the function. It updates automatically as additional points are defined for the function. Run the mouse pointer over the function graph and a dot appears along the line representing the response spectrum. The coordinates of the dot are reported in the box just below the graph.

Access the Response Spectrum Function Definition - User Defin form to add a user spectrum as follows:

1. Click the Define menu > Functions > Response Spectrum command to access the Define Response Spectrum Functions form. Then do one of the following:

   • Select User from the Choose Function Type to Add drop-down list; click the Add New Function button.

   • Highlight an existing User function definition in the Response Spectra display area and click the Modify/Show Spectrum button.

2. Select User from the drop-down list.

Note:  This form also appears when the Convert to User Defined button is clicked on the code-specific function forms.