# Buckling length coefficient kcr **URL:** \ **Category:** Product Support\ **Tags:** rfem-6, effective-length, addon-structure-stability\ **Created:** [August 19, 2026, 2:51pm UTC](https://community.dlubal.com/t/knicklangenbeiwert-kcr/4122 "2026-08-19T14:51:30Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![vferg](https://community.dlubal.com/letter_avatar_proxy/v4/letter/v/258eb7/32.png) [@vferg](https://community.dlubal.com/u/vferg)\ **Post date:** [August 19, 2026, 2:51pm UTC](https://community.dlubal.com/t/knicklangenbeiwert-kcr/4122/1 "2026-08-19T14:51:30Z")
Hi everyone, I’m currently working on a project for a course assignment. My classmates and I are having trouble interpreting the following information about the “Stability Analysis” add-on: The effective length factor kcr is generally 1.0 for a member pinned at both ends and at most 0.5 for a member fixed at both ends. The system I created is pin-supported and carries only axial forces. However, the factor for member number 97 is 0.487. I can’t explain this value, as I intended to model a pinned support condition. Could someone please help me with this? I’ve attached a link to the relevant file. Thank you in advance for your help and time! [https://drive.google.com/file/d/1NqR5hb-9Vc0FCWx6tSYVjfzY-UOBjeaf/view?usp=drive\_link](https://drive.google.com/file/d/1NqR5hb-9Vc0FCWx6tSYVjfzY-UOBjeaf/view?usp=drive_link) ---
**Author:** ![stefan.hoffmann](https://community.dlubal.com/user_avatar/community.dlubal.com/stefan.hoffmann/32/108_2.png) [@stefan.hoffmann](https://community.dlubal.com/u/stefan.hoffmann)\ **Post date:** [August 20, 2026, 8:37am UTC](https://community.dlubal.com/t/knicklangenbeiwert-kcr/4122/5 "2026-08-20T08:37:44Z")
Hi vferg, welcome to the community 🙂 ! The following webinar explains buckling lengths (starting at around minute 43): ► [https://www.dlubal.com/de/support-und-schulungen/schulungen/videos/004049](https://www.dlubal.com/de/support-und-schulungen/schulungen/videos/004049) For a system with multiple members, it’s important to generate a local mode shape and then determine the buckling length for that member. Please reconsider your model using only truss members — N only. These are numerically stable here, even though a chain of hinges forms at all the connections. A better approach is to use a combination of beam and truss members. When I test your model using beam members with a small member end hinge, I get a local mode shape. The governing buckling length for the member here is 1.0: ![image](https://community.dlubal.com/uploads/default/original/2X/a/a44d1d551a8588564618f0065063a745068dc78f.png) Your member types do not produce a local mode shape, due to the member type, so the values cannot be used here. Best regards, Stefan Hoffmann ---
**Author:** ![vferg](https://community.dlubal.com/letter_avatar_proxy/v4/letter/v/258eb7/32.png) [@vferg](https://community.dlubal.com/u/vferg)\ **Post date:** [August 29, 2026, 10:48am UTC](https://community.dlubal.com/t/knicklangenbeiwert-kcr/4122/6 "2026-08-29T10:48:55Z")
Hi Stefan, Thanks for your reply. Unfortunately, I haven't been able to solve my problem, and I still have a few questions: - Why are you using the self-weight load case (LF Eigengewicht) here instead of the governing ULS combination? - I modeled all the members as beam members, assigned end hinges at both ends, set the spring stiffnesses as shown in your screenshot, and ran the analysis (also using the self-weight load case). However, for member 30, I get a kcr value of 0.591 for the first eigenmode, while the values for the other members range from 0,... to 32. So I don't get the same result as you—why is that? - Did you change the material or the cross-sections of the members? Thanks in advance. Best regards, vferg ---
**Author:** ![stefan.hoffmann](https://community.dlubal.com/user_avatar/community.dlubal.com/stefan.hoffmann/32/108_2.png) [@stefan.hoffmann](https://community.dlubal.com/u/stefan.hoffmann)\ **Post date:** [August 31, 2026, 6:16am UTC](https://community.dlubal.com/t/knicklangenbeiwert-kcr/4122/7 "2026-08-31T06:16:35Z")
Hi vferg, I only chose the LF self-weight as a representation because the resulting internal forces are generally easy to follow here. Could you please upload your modified model? I only modified the points mentioned. Best regards, Stefan Hoffmann ---
**Author:** ![vferg](https://community.dlubal.com/letter_avatar_proxy/v4/letter/v/258eb7/32.png) [@vferg](https://community.dlubal.com/u/vferg)\ **Post date:** [September 2, 2026, 8:19am UTC](https://community.dlubal.com/t/knicklangenbeiwert-kcr/4122/8 "2026-09-02T08:19:24Z")
[Konstruktion\_Ahornfrucht diagonal.rf6](https://community.dlubal.com/uploads/short-url/258MSSZ1GKdwicaPNBqK4J1TcFK.rf6) (5.3 MB) Hello, attached is the file. ---
**Author:** ![stefan.hoffmann](https://community.dlubal.com/user_avatar/community.dlubal.com/stefan.hoffmann/32/108_2.png) [@stefan.hoffmann](https://community.dlubal.com/u/stefan.hoffmann)\ **Post date:** [September 2, 2026, 9:19am UTC](https://community.dlubal.com/t/knicklangenbeiwert-kcr/4122/9 "2026-09-02T09:19:54Z")
Hi vferg, Thanks for your feedback. To avoid distorting the system too much, the value at the joint needs to be very small. You set it to 1000, which already has a significant clamping effect. I had set it to just 1.0: ![image](https://community.dlubal.com/uploads/default/original/2X/b/bc2d5f71b3fbf814d68966b8b18a8fe79184b40f.png) The higher the value, the less pinned the joint becomes and the more it tends toward a fixed connection. So the effective length factor is already very close to 0.5 here, rather than 1.0. Best regards, Stefan Hoffmann ---
**Author:** ![vferg](https://community.dlubal.com/letter_avatar_proxy/v4/letter/v/258eb7/32.png) [@vferg](https://community.dlubal.com/u/vferg)\ **Post date:** [September 17, 2026, 1:56pm UTC](https://community.dlubal.com/t/knicklangenbeiwert-kcr/4122/10 "2026-09-17T13:56:34Z")
Hello Stefan, Thanks to your help, I now arrive at a minimum kcr value of 1.34 in the governing load case for member 21 — that sounds much more plausible to me. Thank you very much for your extensive support! Kind regards, vferg