Section Designer
Additional forms: Moment Curvature Curve Details for {Curve Number}, Stress/Strain Contours for {Curve Number}
Use the Display menu > Show Moment Curvature Curve command or button to display the Moment Curvature Curve form. Use the form to display moment curvature curves for concrete sections that have reinforcing. If the section is not concrete and does not have reinforcement, this command will not be available.
Display areas.
Curvature plot. The program generates the moment curvature curve with moment on the vertical axis and curvature on the horizontal axis. Click the Details button in the lower right corner of the form to display the Moment Curvature Curve Details for {Curve Number} form. The lower portion of that form shows the moment curvature curve data in tabular form. The number of rows of data in the table and the number of points used to generate the plot are controlled by the number of points specified in the No. of Points edit box.
When the mouse pointer is moved over the plot, a display box below the Curvature plot area shows the value of the moment curvature curve at that point. The curvature is listed first followed by the moment.
Strain Diagram plot. This plot is generated when the mouse pointer is moved over the Curvature plot. The strain diagram illustrates the strain at that particular point on the curve.
When the mouse pointer is moved over the plot, the values for Concrete Strain, Steel Strain, and Neutral Axis are shown for that point in display boxes below the plot.
Select Type of Graph drop-down list. Choose the type of plot to be displayed.
Specify Scales/Headings button. Click this button to display the Override Axial Labels and Range form. Use the edit boxes on that form to change the horizontal and vertical ranges for the plot and the labels used on the horizontal and vertical axes.
Plot Exact Integration Curve check box and Color box. When this check box is checked, the exact integration curve will be included in the plot using the color shown in the Color box. Click the Color box to display the Color form; use that form to change the color used to display the exact integration curve.
Plot 3x3 Fiber Model Curve check box and Color box. When this check box is checked, the fiber model curve will be included in the plot using the color shown in the Color box. Click the Color box to display the Color form; use that form to change the color used to display the fiber model curve.
Show Numerical Results for Exact-Integration Curve option and Show Numerical Results for Fiber Model Curve option. The availability of these options depends on if the Plot Exact Integration Curve check box or the Plot 3x3 Fiber Model Curve check box or both are checked.
Caltrans Idealized Model check box. When this check box is checked, the moment curvature curve is generated in accordance with Caltrans specifications and the options in the Analysis Control area of the form become available.
Concrete Failure (Lowest Ultimate Strain) or Concrete Failure (Highest Ultimate Strain) options. When these option are selected, the Curvature plot shows the moment curvature curve for concrete failure at the lowest ultimate strain or the highest ultimate strain, respectively.
First Rebar Failure option. When this option is selected, the Curvature plot shows the moment curvature curve for rebar failure.
User Defined Curvature option. When this option is selected, an edit box is added to the form; use the edit box to specify the maximum curvature for the Curvature plot in accordance with Caltrans specifications.
P (Tension +ve) edit box. Enter the axial load for which the moment curvature curve is to be plotted. Tension values are positive and compression values are negative.
Max Curvature edit box. Enter the maximum curvature that the program is to consider when plotting the moment curvature curve. Note that the section may not be capable of reaching the maximum curvature specified. In other words, the section may fail before reaching the curvature specified in the Max Curvature edit box. If this happens, the maximum curvature shown in the Curvature plot or on the table on the Moment Curvature Curve Details for {Curve Number} form (displayed by clicking the Details button) may be less than the maximum curvature specified in the Max Curvature edit box. When the maximum curvature reported in the plot or in the table is less than the curvature specified, the section is not capable of carrying the axial load specified in the P edit box at a curvature equal to that specified in the Max Curvature edit box.
No of Points edit box. Enter the number of points used to construct the moment curvature curve.
Angle (Deg) edit box. This angle defines the orientation (direction) of the neutral axis, but not its exact location. The angle is measured from the negative local 3-axis of the section. Positive angles appear counterclockwise as you look down on the section. The angle can vary from -360° to +360°. The figure below illustrates how the angle controls the orientation of the neutral axis. Figure a shows the angle at 0° and Figure b shows the angle at 45°.
The angle also dictates the direction of the moment considered. When the angle is 0 degrees, the direction of moment is in the positive direction of the local 3-axis. Use the right hand rule to get a sense of the direction of this moment. When the angle is 180 degrees, the direction of moment is in the negative direction of the local 3-axis. The above figures illustrate the sense of the moment when the angle is 0 and 45 degrees.
As an example, if the angle specified were 225 degrees, the neutral axis would have the same orientation as that shown in the figure above, but the direction of the moment would be reversed as shown in the following figure.
Details button. Click this button to display the Moment Curvature Curve Details for {Curve Number} form. The top portion of the form shows a graphic of the Curvature plot. The bottom portion of the form shows a table that lists the moment and curvature values at each of the considered points of the moment curvature curve. The values shown in the table are connected by straight line segments to form the plot. Use the scroll bar on the right-hand side of the form to scroll from top to bottom in the display area.
File menu > Print to File command. This command prints the data to an output file (.out).
Contours button. Click this button to display the Stress/Strain Contours for {Curve Number} form. Use the options on the form to graphically display the stress or strain for a single point or all points. Use the arrow buttons in the lower right-hand corner of the form to cycle through the plot of the various points.
Add Curve button. Clicking this button will add curves to the plot based on the various choices made on the form. For example, if the Plot 3x3 Fiber Model Curve check box is checked, the curve added will be a Fiber 3x3 Curve. The P (Tension +ve) and Angle (Deg) check boxes also can be used to refine the curve definition; then click the Add Curve button. Note that the curve will be displayed using the color shown in the Selected Curve Color box. Click the Color box to display the Color form; use that form to change the color used to display the curve selected in the Curves display list.
Delete Curve button. Highlight a curve in the Curves display list, and click this button to delete the selected curve.