The section cut forces for moving load analysis represent realistic forces for the given section cut. Extreme forces from individual section cut elements that occur for different placements of the live load are not combined together as this would result in overestimating the section cut forces. This can be illustrated by a simple model that I have attached.

In the attached model, the lane and section cuts are defined as shown in the figure below:

Unit load "vehicle" is applied to travel along the lane, which results in the moment diagram shown below:

Since each of the two main beams is 10m long, the maximum moment at the midspan due to the unit moving load is (0.5 kN reaction) * (0.5 m support to midspan location) = 2.5 kN-m as indicated in the above screenshot.

Now, two section cuts (one using groups and the other using quadrilateral cutting plane) are defined such that they cut both beams at the midspan. The section cut moments are again 2.5 kN-m, which indicates that the results are as expected:

Attachments

• SAP2000 V11.0.8 model (Zipped SDB file)