Section Cuts

Section cut forces are reported at a single point in the local coordinate system defined for the section cut. Six different force components are reported at that single point. They are:

Section cut forces are reported as forces acting on the objects that make up the group that defines the section cut. An example of this is discussed below. Positive section forces act in the same direction as the positive section cut local axes. The sense of positive moments can be determined using the right hand rule.

Consider the example shown in the figure below. The global coordinate system axes and the section cut local coordinate system axes are shown in Figure "a." This illustrates that the local coordinate system axes may be different from the global system.

 

 

 

Figure "b" shows a floor system that consists of 9 area objects labeled F1 through F9 and 16 associated point objects labeled 1 through 16. Suppose that we want to determine the section cut forces through the floor system at the location identified by the heavy line in Figure "c." This section cut passes through the point objects labeled 3, 7, 11 and 15.

There are two possible groups you could define to use in the section cut definition. Figure d shows the first possible group which includes area objects F2, F5 and F8 and point objects 3, 7, 11 and 15. Figure e shows free body diagrams that define the positive direction of section cut forces when the section cut is defined using the group definition shown in Figure d. Note that the positive section cut forces acting on the left free body diagram are in the same direction as the positive section cut local axes shown in Figure a. The left free body diagram is the one that includes the objects that were used to define the group that defined the section cut.

Figure "f" shows the second possible group that could define the section cut. This group includes area objects F3, F6 and F9 and point objects 3, 7, 11 and 15. Figure "g" shows free body diagrams that define the positive direction of section cut forces when the section cut is defined using the group definition shown in Figure "f." Note that the positive section cut forces acting on the right free body diagram are in the same direction as the positive section cut local axes shown in Figure "a." The right free body diagram is the one that includes the objects that were used to define the group that defined the section cut.