How to Sum Reaction Forces

The summation of reaction forces in a model is often used to verify input loadings, validate model behavior or determine floor load distributions. In the Results environment, the "Inquire: Results" dialog can be used to sum the reaction forces of selected nodes.

Another typical application of summing reaction forces is to determine the total force of a pressure load when the area of pressure is unknown and cannot be readily calculated. As shown in Figure 1, the cutting frame has a pressure load applied to two surfaces of unknown area and is fully constrained at the bottom of each of the four legs. The total force of the pressure can be calculated by summing the vertical reactions of all of the constrained nodes.

To sum the reaction forces in the Results environment for a Static Stress Analysis:

• Select and display the desired reaction (X, Y or Z) using the "Results Contours” tab,  “Other Results” panel, “Reactions” pull-down menu “Reaction Force (Negative) ” pull-out menu;
• Select the nodes that will be used in the summation;
• Right click anywhere in the working area;
• In the pop-up menu that appears, select "Inquire Results"; and
• In the "Inquire: Results" dialog (Figure 2), click on the "Summary" pull-down menu and select "Sum".