Use the Interaction Surface Definition form as follows:
User Interaction Curve Options -- Choose the appropriate options. Note that when an option is selected, an explanation of that option is provided in the lower left-hand corner of the form. Those explanations are not repeated here.
Number of Curves and Number of Points on Each Curve edit boxes -- The values entered here determine the number of curves and the number of points on each curve specified in the spreadsheet area of the form.
Spreadsheet
Use the defaults or enter values in the spreadsheet to indicate the various P-M interaction curves that together define the interaction surface. Use the scroll bars in the spreadsheet area to view the additional M columns (move the scroll bar to the right).
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Important Notes: |
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For the axial load values, tension should always be input as positive and compression should always be input as negative. This is opposite the design convention for concrete but is consistent with the analysis convention and the steel-design convention. |
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The angle associated with each M column is indicated at the top of the spreadsheet. Angle 0 corresponds to the +M2 axis (usually the minor moment), Angle 90 corresponds to +M3 (usually the major moment), and so on. The moment values in each M column should always be input as positive values. |
When entering values in the P column of the spreadsheet, the plot at the right-hand side of the form shows the P versus M Curve 1 diagram. When entering values in an M column, the plot at the right of the form shows P versus the M Curve associated with the cursor location.
Scaling
Enter a scale factor in the P edit box. The default for this value is 1. This scale factor multiplies all values in the P column.
Enter a scale factor in the M edit box. The default for this value is 1. This scale factor multiplies all values in all the M columns. Typically the interaction surface in the spreadsheet is normalized so that the maximum moment at Angle 90 is 1, and the scale factor is set to the actual value of maximum moment at Angle 90 (+M3). Alternatively, the scale factor may be set to 1 and actual moment values may be input in the spreadsheet.
Access the Interaction Surface Definition form as follows:
Click the Define menu > Section Properties > Frame Nonlinear Hinge command to access the Define Frame Hinge Properties form. Then do one of the following:
Click the Add New Property button, which will access the Default for Added Hinges form; select an option to specify the default property settings for the new hinge definition; the Frame Hinge Property Data form will display.
Highlight a previously defined property and click the Add Copy of Property or the Modify/Show Property button, to access the Frame Hinge Property Data form.
Select P-M2-M3 from the list of hinge Types to access the Frame Hinge Property Data for {Hinge Name} - Interacting P-M2-M3 form.
Click the Modify/Show P-M2-M3 Interaction Surface Data button to access the Frame Hinge Interaction Surface for {Hinge Name} - Interacting P-M2-M3 form.
Select the User Definition option if it is not already selected and click the Define/Show Surface button.