# Error in simple truss analysis with one element **URL:** \ **Category:** Uncategorized\ **Created:** [September 17, 2021, 5:03pm UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721 "2021-09-17T17:03:01Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [September 17, 2021, 5:03pm UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721/1 "2021-09-17T17:03:01Z")
Hi, I’m trying to run this simple analysis involving one truss element (fixed at one end, compressed at the other one) in CalculiX: ```auto *Node 1, 0, 0, 0 2, 55, 0, 0 *Element, type=T3D2, elset=all 1, 1, 2 *Nset, nset=Set-1 1, 2 *Elset, elset=Set-1 1, *Solid Section, elset=all, material=Material-1 1., *Nset, nset=fix 1, *Nset, nset=load 2, *Material, name=Material-1 *Elastic 2., 0.3 *Boundary fix, 1, 6 *Step *Static *Cload load, 1, -1. *EL PRINT,ELSET=all,FREQUENCY=100 S,E *NODE FILE,OUTPUT=3D U *EL FILE S,NOE,E *End Step ``` But I get this error: ![error](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/1981f149b8d42be90cfd337622f8fb3819998caa.jpeg) To make sure that it’s not a modeling error, I submitted the same input file in Abaqus and got correct results. Am I missing some special characteristic of truss elements in ccx ? ---
**Author:** ![ginda](https://avatars.discourse-cdn.com/v4/letter/g/e68b1a/32.png) [@ginda](https://calculix.discourse.group/u/ginda)\ **Post date:** [September 17, 2021, 11:09pm UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721/2 "2021-09-17T23:09:47Z")
Change `fix, 1, 6` to `fix, 1, 3`. No bending for `T3D2`. ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [September 18, 2021, 12:05pm UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721/3 "2021-09-18T12:05:57Z")
Right, it works. Thank you 🙂 Apparently, Abaqus handles those redundant boundary conditions differently. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [September 27, 2021, 6:24am UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721/4 "2021-09-27T06:24:15Z")
> [@ginda](#): > > No bending for `T3D2` . Hi, I’have observed weird results on that beam under compression. It is the same file posted but once refined. When using ccx\_dynamic.exe for windows both pardiso and Pastix gives weird results. ¿May i have some missing dll. Does it happen to someone else? ![screenshot.10](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/52a3a5ff8931f4cea0a45a65cb0693281c613890.jpeg) ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [September 27, 2021, 3:58pm UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721/5 "2021-09-27T15:58:13Z")
hi, above example are for truss element, so it does not required mesh to be refined. only use one element mesh betwen each joint of connected members. spliting and refining mesh may cause stability problem and spurious movement since each element end nodes become hinged. best ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [September 27, 2021, 6:29pm UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721/6 "2021-09-27T18:29:12Z")
Again, it seems to be handled differently by various solvers. In Abaqus there’s no such spurious deformation in this example when multiple truss elements are used. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [September 28, 2021, 5:46am UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721/7 "2021-09-28T05:46:06Z")
Thanks Suyono Un Saludo/Best Regards ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [September 28, 2021, 7:27am UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721/8 "2021-09-28T07:27:05Z")
Changing the force direction also fails. I have build and refine a truss with a mass at the end expecting it to behave as a pendulumm (chain) but it fails so it should not be exactly a hinged connection. ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [September 28, 2021, 11:04pm UTC](https://calculix.discourse.group/t/error-in-simple-truss-analysis-with-one-element/721/9 "2021-09-28T23:04:07Z")
hi, you could try changie and use the element to B31R rather than T3D2 to avoid any unexpected behaviour due to unstable structure problems. even it’s a beam element the bending effect did not take into account, these beam are expanded to C3D8R element with only one integration point. best,