# REF Node of Pretension Section . Reaction Force **URL:** \ **Category:** Analysis issues\ **Created:** [February 1, 2026, 12:26am UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759 "2026-02-01T00:26:27Z")\ **Posts on this page:** 9\ **Page:** 1
**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:** [February 1, 2026, 12:26am UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759/1 "2026-02-01T00:26:27Z")
Hi, Any idea why RF on the pretension section reference node do not deliver the expected value? Pretension load 1000 N. Section print of the pretension section 9.999600E+02 N RF at the BC : 1000 N . RF at Pretension section reference node (37) : 6.250000E+01 N (Unexpected ¿?¿) Thanks. ```auto *NODE 1,0,0,0 2,0.001,0,0 3,0.001,0.001,0 4,0,0.001,0 5,0,0,0.001 6,0.001,0,0.001 7,0.001,0.001,0.001 8,0,0.001,0.001 9,0.0005,0,0 10,0.001,0.0005,0 11,0.0005,0.001,0 12,0,0.0005,0 13,0.0005,0,0.001 14,0.001,0.0005,0.001 15,0.0005,0.001,0.001 16,0,0.0005,0.001 17,0,0,0.0005 18,0.001,0,0.0005 19,0.001,0.001,0.0005 20,0,0.001,0.0005 21,0.0005,0,0.0005 22,0.001,0.0005,0.0005 23,0.0005,0.001,0.0005 24,0,0.0005,0.0005 25,0.0005,0.0005,0 26,0.0005,0.0005,0.001 27,0.0005,0.0005,0.0005 28,0.000475,0.0005,0 29,0.000475,0.001,0 30,0.000475,0.001,0.0005 31,0.000475,0.0005,0.0005 32,0.000475,0.001,0.001 33,0.000475,0.0005,0.001 34,0.000475,0,0 35,0.000475,0,0.0005 36,0.000475,0,0.001 37,0,0,0 *ELEMENT,TYPE=C3D8I 1,24,31,30,20,16,33,32,8 2,1,34,28,12,17,35,31,24 3,9,2,10,25,21,18,22,27 4,25,10,3,11,27,22,19,23 5,12,28,29,4,24,31,30,20 6,17,35,31,24,5,36,33,16 7,21,18,22,27,13,6,14,26 8,27,22,19,23,26,14,7,15 9,25,27,23,11,28,31,30,29 10,27,26,15,23,31,33,32,30 11,9,21,27,25,34,35,31,28 12,21,13,26,27,35,36,33,31 *ELSET,ELSET=DEFAULT 1 2 3 4 5 6 7 8 9 10 11 12 *SURFACE,NAME=REACTION 8,S4 4,S4 7,S4 3,S4 *SURFACE,NAME=PRETENSIONSECTION 9,S1 10,S1 11,S1 12,S1 *MATERIAL,NAME=MATERIAL *ELASTIC,TYPE=ISOTROPIC 210000000000,0.3 *SOLID SECTION,ELSET=DEFAULT,MATERIAL=MATERIAL *BOUNDARY 1,1,,0 2,1,,0 3,1,,0 3,3,,0 4,1,,0 4,3,,0 5,1,,0 6,1,,0 7,1,,0 8,1,,0 10,1,,0 10,2,,0 12,1,,0 12,2,,0 14,1,,0 14,2,,0 16,1,,0 16,2,,0 17,1,,0 18,1,,0 19,1,,0 20,1,,0 22,1,,0 24,1,,0 *AMPLITUDE,NAME=pretensionsection1 0,0 1,1000 *PRE-TENSION SECTION,SURFACE=PRETENSIONSECTION,NODE=37 1.000000000000E+000,0.000000000000E+000,0.000000000000E+000 *NSET,NSET=N_REACT 37 *STEP,NLGEOM=YES,INC=100,AMPLITUDE=STEP *STATIC 0.1,1,0,0.1 *CLOAD,AMPLITUDE=pretensionsection1 37,1,1 *NODE FILE,GLOBAL=YES U,RF *EL FILE S,NOE,E,ENER *CONTACT FILE CDIS,CSTR *SECTION PRINT,SURFACE=PRETENSIONSECTION,NAME=Reaction_forces SOF,SOM *NODE PRINT,NSET=N_REACT,NAME=Reaction_Node RF,U *END STEP ``` ---
**Author:** ![chewbacca](https://avatars.discourse-cdn.com/v4/letter/c/e9c0ed/32.png) [@chewbacca](https://calculix.discourse.group/u/chewbacca)\ **Post date:** [February 3, 2026, 8:33am UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759/2 "2026-02-03T08:33:57Z")
sorry, forget my last post… still had an error in the deck. The deck itself seems ok, since ABAQUS yields correct output ```auto THE FOLLOWING TABLES ARE PRINTED SOFM SOF1 SOF2 SOF3 SOMM SOM1 SOM2 SOM3 1000. 1000. -1.5715E-14 -4.7307E-15 0.7066 4.6111E-18 0.4993 -0.5000 ``` ---
**Author:** ![chewbacca](https://avatars.discourse-cdn.com/v4/letter/c/e9c0ed/32.png) [@chewbacca](https://calculix.discourse.group/u/chewbacca)\ **Post date:** [February 3, 2026, 10:23am UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759/3 "2026-02-03T10:23:51Z")
For a beam of completely different geometry (4mm x 2mm x 2mm) but still 1000N pre-tension I get the same result as above: `9.999600E+02 N` (i.e. off by the tiny fraction of 4E-05N) So I assume adding the float integration point weights and locations in the element up yields a very small error. And yes, the reaction force for the pre-tension node does obviously NOT match the pre-tension force, in my example it is 1/8 of the applied load, in yours 1/16… we can check this ---
**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:** [February 3, 2026, 10:58am UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759/4 "2026-02-03T10:58:16Z")
Hi @chewbacca , Thanks for looking at this. Seem Rf on the ref node of a pretension section is not working properly. I will post on GitHub. I agree Section print is right . Thank you again. ---
**Author:** ![chewbacca](https://avatars.discourse-cdn.com/v4/letter/c/e9c0ed/32.png) [@chewbacca](https://calculix.discourse.group/u/chewbacca)\ **Post date:** [February 3, 2026, 11:54am UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759/5 "2026-02-03T11:54:24Z")
Since 62.5N (corner), 125N (mid-side) and 250N (center) are the nodal reaction forces depending on the nodes’ location on the cross-section I would assume that ccx refers to one of those rather than their sum (maybe due to mpcs) when generating the output. In my case the nodal numbering is a bit different, so ccx reports 125N in contrast to your 62.5N. So their is something wrong (but just for info: ABAQUS reporst RF=0.0 for the pre-tension node). ---
**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:** [February 3, 2026, 12:28pm UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759/6 "2026-02-03T12:28:53Z")
This simple model shows RF1=300 N (applied preload is 1200 N) if submitted in ccx 2.22 and RF1=1200 N if submitted in ccx 2.23: > \*NODE > 1, 0, 0, 0 > 2, 0, 0, 10 > 3, 0, 10, 0 > 4, 0, 10, 10 > 5, 10, 0, 0 > 6, 10, 0, 10 > 7, 10, 10, 0 > 8, 10, 10, 10 > 9, 0, 0, 20 > 10, 0, 10, 20 > 11, 10, 0, 20 > 12, 10, 10, 20 > 13, 0, 0, 0 > \*ELEMENT, TYPE=C3D8, ELSET=EALL > 1, 4, 2, 1, 3, 8, 6, 5, 7 > 2, 10, 9, 2, 4, 12, 11, 6, 8 > \*NSET, NSET=FIXED > 1, 3, 5, 7, 9, 10, 11, 12 > \*NSET,NSET=PREF > 13 > \*NSET, NSET=PNSET > 2, 4, 6, 8 > \*ELSET, ELSET=PELSET > 1 > \*SURFACE, NAME=PSURF, TYPE=ELEMENT > PELSET, S3 > \*MATERIAL, NAME=STEEL > \*ELASTIC > 210000, 0.3 > \*SOLID SECTION, ELSET=EALL, MATERIAL=STEEL > \*PRE-TENSION SECTION, SURFACE=PSURF, NODE=13 > \*STEP > \*STATIC > \*BOUNDARY > FIXED, 1, 6, 0 > \*CLOAD > 13, 1, 1200 > \*NODE PRINT, NSET=PREF > RF > \*NODE PRINT, NSET=PNSET > RF > \*NODE FILE > RF, U > \*END STEP Forces from the nodes on the pretension surface are also printed. RF3 (preload direction) in each node there is actually -300 N. ---
**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:** [February 3, 2026, 12:50pm UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759/7 "2026-02-03T12:50:21Z")
OHH.😀 That was fixed silently at some point in this last version. 2.23. Thank you very much. In some way it confirms there is a bug in previous version. Solved then. Thanks. ---
**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:** [February 3, 2026, 12:52pm UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759/8 "2026-02-03T12:52:32Z")
As RF contains the external forces I guess solution should be: RF = 1000N for Displacement Driven Preload. RF = 0 N for Load Driven Preload. Regards EDITED: CCX 2.23 delivers 1000N in both cases. I guess it behaves like a REF node of a Rigid Body. ---
**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:** [February 3, 2026, 1:01pm UTC](https://calculix.discourse.group/t/ref-node-of-pretension-section-reaction-force/3759/9 "2026-02-03T13:01:01Z")
> [@Disla](#): > > That was fixed silently at some point in this last version. 2.23. Yeah, it’s good to retest all GitHub bug reports just in case. Unfortunately, many are still relevant, from what I’ve noticed so far. > [@Disla](#): > > I guess it behaves like a REF node of a Rigid Body. Yes, exactly.