Response Spectrum

In the Response Spectrum tab, you can assign response spectra to the individual excitation directions that can be used to determine the seismic loads.

Specifying Response Spectra for Directions

Assign Response Spectra

In this section, you can specify in which global axis direction a response spectrum should act and which spectrum is relevant in each case. Different response spectra can be effective for individual excitation directions.

It is necessary to activate at least one "Direction". Then, select one of the existing response spectra for this direction from the list. You can create a new spectrum using the button and edit the selected spectrum using the button.

You can specify a "scaling factor" for each direction in order to increase or flatten the response spectrum. You can check the result of the scaling in the table of a diagram and the Selection of Modes tab. The values of the diagram are shown scaled there.

Rotation of Horizontal Accelerations

The excitation direction can be rotated by an angle in the XY plane. For example, if the response spectrum is to excite the model at an angle of 45° around the Z-axis, you only need to activate the X direction for the response spectrum and specify the angle α as 45°.

Diagram

The lower section shows the read-in response spectrum as a diagram. The default diagram is the "Acceleration Period Diagram". You can use the X, Y, and Z buttons to the right of the diagram to control which direction is displayed.

Selecting Direction for "Acceleration-Period Diagram"

If you move the mouse along the graph, the respective abscissas and ordinates appear. Use the mouse wheel to zoom, use the left mouse button to move the diagram, and double-click the mouse wheel to restore the overall view of the diagram.

Abscissa: Period or Frequency

The diagram can be displayed as an "Acceleration – Period Diagram" or "Acceleration – Frequency Diagram". Use the list button to specify which size is used for the abscissa axis.

Displaying "Acceleration-Frequency Diagram"

Display: Linear or Logarithmic

A linear (lin) and logarithmic (log) division of the axes is possible for an optimal display. The following options are available using the list button:

• lin X / lin Y
• log X / lin Y
• lin X / log Y
• log X / log Y

Displaying Diagram with Logarithmic Division

Print Function

It is also possible to print the diagram. You have the following options:

• Print Graphics to Printer
• Print Graphics to Printout Report
• Print Graphics to PDF
• Print Graphics to Clipboard
• Print Graphics to File

Printing Diagram

The graphics printout is described in the chapter Graphics of the RFEM manual.