Problem with Strand7 analysis
Problem with Strand7 analysis
(OP)
Hi, i tried to model a structure that supports a pebble crusher and when i assigned a pinned connection to some beams of the model (using Attributes/Beam/End Release/Rotation/1 and 2:Rel), the following error appears in the linear static solver: Global stiffness matrix is singular. And i couldn't figure out why is that.
Then i tried to model a simpler case and i have the same error:
Global Stiffness Matrix Singular at Equation 7: Pivot = 0.000000E+00 (Node 5 DX)
*ERROR[ 4]:Global stiffness matrix is singular.
I just create 3 beams, 2 simply supported and the other one connected to them, then assigned a geometry to the beams and self-weight as load case.
Does anyone have the same error?
Please help!
Then i tried to model a simpler case and i have the same error:
Global Stiffness Matrix Singular at Equation 7: Pivot = 0.000000E+00 (Node 5 DX)
*ERROR[ 4]:Global stiffness matrix is singular.
I just create 3 beams, 2 simply supported and the other one connected to them, then assigned a geometry to the beams and self-weight as load case.
Does anyone have the same error?
Please help!






RE: Problem with Strand7 analysis
The simplest way to see this problem is to shrink all members by, say, 10%. Do this via
Entity display > Beams > Shrink
One simple way to fix it is to subdivide each of the two side members into two, then "clean" the resulting mesh.
Tools > Subdivide
Tools > Clean > Mesh
However in your real problem (rather than the hugely simplified example you wisely posted) fixing might not be so simple.
RE: Problem with Strand7 analysis
Denial - The Strand7 viewer is a free download, and will open any size file, including results. It will do pretty well everything except edit the model and run the analysis.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Problem with Strand7 analysis
Do you know can i connect these elements in Strand7?
I'm not get used to this program yet
RE: Problem with Strand7 analysis
As Denial explained, there is no connection between your central beam and the two outer beams. These members need to share a common node in order to be able provide stiffness to your central beam.
The easiest way to do this with your situation is to select all members then go to tools-->intersect beams. You model should run fine after this.
Also take care as to the orientation of your beams, they are bending about their weak axis as currently modelled. You can visualise this by by changing the beam entity display mode to section or solid.
RE: Problem with Strand7 analysis
In general it would be better to use the beam intersect function as suggested by robbievanl because the subdivision process will only work if the intersection point is exactly at the mid-point of the beams being sub-divided. Also for a more complex model you should always clean the mesh to make sure all free nodes are deleted and nodes with common coordinates are merged.
If you can get to a Strand7 training course I can recommend them. For someone starting out with the program the increase in productivity will pay back the course time and costs very quickly.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Problem with Strand7 analysis
Unfortunately, it didn't work.
I've tried everything; the Subdivide tool, Intersect Beams, Clean Mesh, and the program is still having the same error about the singularity in the stiffness matrix when i try to assign a pinned connection between the central beam and the two outer beams.
Thanks anyway for the help
RE: Problem with Strand7 analysis
This is a classic trap for people in their early days of learning automated frame analysis. I've fallen into it myself an embarrassingly large number of times.