Strand7:  Hints & Tips

Direct summation of loads
When you run the structural solvers, Strand7 reports the total amount of load acting on the structure as:

  1. DIRECT SUMMATION
  2. MOMENTS ABOUT THE ORIGIN
These numbers can be very useful in monitoring the amount of load you have actually applied to the structure, and for checking overall equilibrium with recoverd reactions. The MOMENTS ABOUT THE ORIGIN reports the total moment sum (MX,MY,MZ) about a point at (0,0,0). The direct summation on the other hand is simply the summation of the entries in the load vector {P} in the equation [K]{d}={P}. This means that on a structure where there is a zero net force, (e.g. a cylinder with a uniform internal pressure), the (FX,FY,FZ) values will be reported as zero. In addition, the moments (MX,MY,MZ) listed here will be different from those given by the MOMENTS ABOUT THE ORIGIN because they do not include the moments due to forces. Further, because the values listed are the summation of the loads in {P}, this does not include any load which is applied to contrained nodes. This means that on the structure shown in the following picture, the total FY is reported as 0.5PL instead of the expected PL.

The expected PL load is instead reported as the load summation applied to beam elements.
Direct Summation of Loads
Cantilever with uniform distributed load.