Show Influence Lines/Surfaces

Forms:  Show Influence Lines/Surfaces, Select Frame Relative Distance

After lanes have been defined and a moving analysis case has been defined and run, click the Display menu > Show Influence Lines/Surfaces command to display the Show Influence Lines/Surfaces form.

The influence lines can be displayed for the various displacements, reactions, forces, moments, shears, and torsion or axial loads on joints, frames, shells, planes, asolids, solids, and links resulting from a unit load on a defined bridge lane in the structure.

The process for displaying influence lines/surfaces is as follows:

1.  Define lanes

2.  Assign frame lanes

3.  Define vehicles

4.  Define vehicles classes

5.  Define a bridge response(s)

6.  Define a moving load analysis case(s)

7. Run the analysis

8. Click the Display menu > Show Influence Lines/Surfaces command to display the Show Influence Lines/Surfaces form. Use the form to specify the influence lines to be plotted:

• Select One or More Lanes selection list. Select the lane(s) for which influence lines are to be displayed by clicking on the lane name in this selection list. Use the Select All Lanes button to select all of the displayed lanes. Use the Clear All Lanes button to deselect all selected lanes. Use the Shift and the Ctrl keys with the mouse to make multiple selection.

• Analysis Case Name drop-down list. Choose the analysis case for which the influence lines are to be displayed by clicking on the analysis case name in this drop-down list.

• Plot Parameters. Choose an option to determine how the plot is to be displayed relative to the lane alignment (along the center line or across the lane width) and if the plot should be a wire frame or a contour. The sub-options offer further refinement of the display with respect to showing or hiding the deck and vertical objects. If the lane has been defined with no width, Plot Along Lane Center Line is the only option available.

• Show Table button. Click the Show Table button to display the influence line data points in tabular form. The data in the table is for display purposes and cannot be edited here. Make changes to the table by adjusting the lane definition. Data in the table can be copied using the Copy Entire Table or Copy Selected Cells buttons. The copied data can then be pasted into another program.

• Contour Range and Transparency area. This area is available if the Plot Over Lane Width as Contours option is selected as the Plot Parameters. Use the Min. and Max. edit boxes to limit the display of the contour to a specified range. Use the Contour Transparency Factor drop-down list to specify the degree of transparency for the contour display. The lower the number, the more transparent the contour.

• Scaling. Select the Auto option to have SAP2000 automatically determine a scaling factor. Select the Scale Factor option to specify a scale factor. SAP2000 calculates the scale factor as a multiple of the default font size, which is determined as a multiple of the average story height. The advantage to determining the scale factor as a multiple of the default font size is that the default font size is limited by a specified minimum and maximum size that is specified using the Options menu > Preference > Dimensions/Tolerances command. This helps keep the automatically determined scale factor within a reasonable range most of the time. If the automatic scale factor seems to cause a display problem, use the Scale Factor option (on the Dimensions/Tolerances Preferences form) and specify a factor.

• Plot Influence Line for This Element Type area. Choose the element type for which the influence line is to be displayed. The option chosen here determines the options available in the lower right portion of the form. If an element type is not available, that element type is not included in the model.

• Joint option.

• Joint Label edit box. Type the Joint number for which the results are to be reported.

• Joint Result Type. Select the Joint Result Type as displacement or joint reaction. Depending on the structural configuration, some of the types may have no influence lines.

• Component. Select the component of joint displacement or joint reaction to be displayed.

• Frame option.

• Frame Label edit box. Type the frame number for which the results are to be reported.

• Relative Distance. This display box will show a default station along the frame object, typically the midpoint of the span. Click the Set Relative Distance to Fall on Lane Load Point button to display the Select Frame Relative Distance form. Select one of the program-calculated values on this form to specify a load point on the frame.

• Component. Select the component of moment, shear, torsion or axial load to be displayed. Depending on the structural configuration, some of the components may have no influence lines.

• Shell option.

• Area Label edit box. Type the shell number for which the results are to be reported.

• Shell Result Type. Select the Shell Result Type as resultant force, top stress or bottom stress. Depending on the structural configuration, some of the types may have no influence lines.

• Joint Label drop-down list. The influence line for the shell object will be plotted relative to the joint selected in this drop-down list.

• Component. Select the component and direction of force, moment, or stress to be displayed.

• Plane option.

• Plane Label edit box. Type the plane number for which the results are to be reported.

• Joint Label edit box. The influence line for the plane object will be plotted relative to the joint selected in this drop-down list.

• Component. Select the component and direction of stress to be displayed.

• Asolid option.

• Asolid Label edit box. Type the asolid number for which the results are to be reported.

• Joint Label edit box. The influence line for the asolid object will be plotted relative to the joint selected in this drop-down list.

• Component. Select the component and direction of stress to be displayed.

• Solid option.

• Solid Label edit box. Type the solid number for which the results are to be reported.

• Joint Label edit box. The influence line for the solid object will be plotted relative to the joint selected in this drop-down list.

• Component. Select the component and direction of stress to be displayed.

• Link option.

• Link Label edit box. Type the link number for which the results are to be reported.

• Link Result Type. Select the Shell Result Type as internal deformation, I-End force or J-End force. Depending on the structural configuration, some of the types may have no influence lines.

• Component. Select  the direction of the deformation or the axial load, shear, torsion or moment of the force to be displayed.

• Click the OK button to view the Influence line or the Cancel button to close the form without viewing the influence lines.

Example:  Use of this command is demonstrated in Problem R.