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This page contains frequently asked questions related to *section cuts*.

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h1. General FAQ

h2. Can the program display force diagrams based on a sequence of section cuts?

*Extended Question*: I have developed a 3d stick model of a slab bridge with the use of shell elements to model the slab.  I have made and saved various section cuts through the slab and wanted to view the shear and bending moment diagrams with quantitative values. Is this possible?

*Answer:* While there is no built-in capability within the program to display shear and moment diagrams for a series of section cuts as of V14.0.0, you can obtain these diagrams outside of the program with some additional pre-processing and post-processing.

(1) Use interactive database editing ("Edit > Interactive Database Editing") to conveniently define multiple section cuts. The data can even be imported from Excel in which you can setup formulas to automate defining the sections cuts at desired intervals along the span.

!Section_cut_definition_tables.png!

(2) Run the analysis and use "Display > Show Tables > ANALYSIS RESULTS > Structure Output > Other Output Items > Section Cuts > Table: Section Cut Forces - Analysis" menu command to display the section cut forces in a tabular format. Then you can export the data to Excel for post-processing and plotting the moment and shear diagrams.

This may require significant effort if done manually, but it would be a reasonable approach if it is automated using Application Programming Interface (API). The discretization should be refined as needed in order to adequately define the section cuts.

Please note that a new feature is planned (collection of section cuts along a line) that will enable you to do this within the program.





h1. Section Cut Defined by Cutting Plane

h2. What is the orientation of positive 3 axis of quadrilateral for quadrilaterals located in vertical plane?

The positive 3 axis refers to the positive 3 axis of the quadrilateral, using the same convention as for shell elements. Therefore, the positive 3 axis is always uniquely defined. {verify}


h2. Can I define the cutting plane to cut though any joints?

For section cuts defined by quadrilateral cutting planes, SAP2000 calculates the section cut forces by summing the element joint forces from the frame, shell and link members that are fully cut by the cutting plane and included in the group that defines the section cut. The joints that are considered are those that (1) belong to the section cut group; (2) are assigned to the fully cut elements; and (3) are on the specified side of the cutting plane. In order for the program to determine on which side of cutting plane the joints are, the cutting plane should not directly pass through any joints, if possible.

h1. Section Cut Defined in Graphical User Interface

h2. The magnitude of the Integrated Forces for the right side is different from the magnitude of the integrated forces for the left side. Why?

*Expanded Question*: After using "Draw > Draw Section Cut", the magnitude of the Integrated Forces for the right side is different from the magnitude of the integrated forces for the left side? Based on equilibrium, should not the magnitude of these two sets of forces be the same?

*Answer:* The section cut forces on the left side and on the right side can be different, because the section cut forces are based on the forces at the joints (of the element cut by the section cut) at each side of the section cut. Create simple example of cantilever wall with two member and determine the section cut forces at the middle of each member.

h2. When section cut is drawn in 3D view only X and Y coordinates are provided. How exactly is the section cut plane defined for this case?

For the "Draw > Draw Section Cut" menu command, the forces are reported in the section cut coordinate system, which is defined by three axes (1,2,Z) as follows:

* section cut 1 axis is located in a plane that is parallel with global XY plane; it is rotated by user-specified "Angle (X to 1)" counterclockwise from the global X axis
* section cut 2 axis is located in a plane that is parallel with global XY plane; it is rotated 90 degrees counterclockwise from section cut 1 axis
* section cut Z axis is parallel with global Z axis

Integrated forces are reported either on the left side or on the right side of the section cut using right hand rule. For example, if the section cut is drawn in a horizontal plane from left to right in an XZ view, then integrated forces on the left side represent the effect from the structure above the section cut, expressed in the section cut (1,2,Z) coordinate system, using right hand rule. Similarly, integrated forces on the right side represent the effect from the structure below the section cut, expressed in the section cut (1,2,Z) coordinate system, using right hand rule. 
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h2. For draw section cut option, why are the integrated forces shown in 1, 2 and Z directions? Why not 1, 2 and 3?

For the section cuts drawn in the graphical user interface, the section cut 3 axis is always parallel with global Z. Therefore the integrated forces are shown in 1, 2 and Z directions.
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