(note as of October 2011 CUFSM4 is now available)
Elastic Buckling Analysis of
Thin-walled members, by their very
nature, have the potential to suffer from a variety of cross-section
stability problems. CUFSM employs the semi-analytical finite strip
method to provide solutions for the cross-section stability of such
members. The software has been successfully used by researchers,
educators, students, and practicing engineers. While CUFSM is most commonly used for thin-walled cold-formed steel members, it has also been
used for a large variety of other materials and applications.
Find the local, distortional
and global buckling load of your member now! Use CUFSM.
The semi-analytical finite strip method is a variant of the more
common finite element method. A thin-walled cross-section is discretized
into a series of longitudinal strips, or elements. Based on these strips
elastic and geometric stiffness matrices can be formulated. The
procedure is readily recognizable by anyone who has studied matrix
analysis of structures, but is specialized to apply to plate
deformations beyond conventional beam theory. A paper describing the
finite strip method, as implemented in CUFSM is available (pdf
of paper). The solution allows a user to explore all potential
cross-section instabilities in a given member in an expedient and
What's new (version 3.12)
Improvements in the user interface and the implementation of the
constrained finite strip method for modal decomposition and
identification are the major changes in version 3.12 of CUFSM. Version
3.12 is a minor bug fix from version 3.11, which was the first major release of CUFSM since 2003.
(Bug fixes: older CUFSM 2.5 and 2.6 files read in properly now,
cross-section properties provided for user convenience have been
The constrained finite strip
method, or cFSM for short, is a new extension to the finite strip
method which provides the ability to decompose stability solutions into
contributions consistent with local-plate, distortional, and global
deformation modes. Further, general analysis may be identified as
containing certain percentages of each of the possible deformation
modes. This new extension, now implemented and shared in CUFSM, provides
users with an entirely new tool for exploring cross-section stability.
The cFSM implemented in CUFSM is discussed briefly in this
paper and the cFSM idea is also
discussed further here.
For a primer on Interpreting
CUFSM results in a glance select the thumbnail to the right. For
a complete explanation of CUFSM and its application within the
Direct Strength Method please see my 170 page design guide,
complete with nearly 100 pages of practical examples,
AISI or the
Steel Framing Alliance and discussed further in
CUFSM 3.12 Tutorials
(start with the table of
tutorials without hyperlinks in pdf format
related CUFSM .mat tutorial files
Download individual tutorials only
Table of contents (ppt)
Frequently Asked Questions - What is
CUFSM? Why use it? (ppt)
Overview of CUFSM features (ppt)
Tutorial 1 - Learn the basics and
interpret results (ppt)
Tutorial 2 - Build a model from
scratch and find Pcr (ppt)
Tutorial 3 - Build a model using the
template and find Mcr (ppt)
Advanced Functions - B. conditions,
springs, constraints, cFSM (ppt)
Advanced Ideas - Defining buckling
modes, higher modes.. (ppt)
Advanced Matlab - Calling
CUFSM from your own code (ppt)
Theory - Background to finite
strip and constrained finite strip (pdf)
Thanks to Zhanjie Li for updating
the tutorials to version 3.12!
For earlier versions, including
tutorials, see the archive.
CUFSM version 3.12
version for PCs
Installation: first - apologies - the new
version of CUFSM takes several minutes to install and initializing the
program is a bit slower due to changes by the Mathworks (makers of
Matlab) in distributing compiled software. Please be a little patient
with the installation. Directions: unzip the setup file to the
directory of your choice, double-click the setup program. Installation requires
that you have Administrator privileges on the machine. This setup has
been tested on a variety of Win XP and Vista machines.
Very rarely the
installation reports that .dll files are missing, in this case the most
likely cause is that your computer may not have certain Visual C++
packages installed. Start by downloading the Microsoft Visual C++
Redistributable Package. For 32-bit systems, download the SP1 version of
here). For 64-bit systems, download vcredist_x64.exe (available
here). After downloading and installing this file, uninstall and
then re-install CUFSM. (Thanks to Ron Ziemian for this fix)
Windows 7 compatability note! Certain icons do not appear after installation on some machines, please follow these instructions to bring the icons back:
1. Right Click on shortcut icon on desktop for CUFSM.
2. Go to properties
3. Click the Compatibility Tab at the top right
4. Check "Run in Compatibility Mode Box"
5. Select Windows XP or Windows Vista from the drop down menu.
6. Exit properties tab and restart CUFSM.
(Thanks to Christopher N Grey, Virgina Tech for this workaraound)
source version for any platform
download all m-files
unzip the files to the directory of your choice. To run in matlab open
the file cufsm3.m and then hit the run button on the toolbar in the
matlab editor, OR, change directory in matlab to the directory you
unzipped the files into by selecting the "..." button after the current
directory listing, and then type "cufsm3" in the command window.
License and Distribution
|CUFSM is open
Free License v 1.2. Please provide a reference to the author (Ben Schafer) and
note the version you are using.
of older CUFSM versions are also available for download. Contact firstname.lastname@example.org
CUFSM is open source, see license. However users of the software are
asked to reference the software when they publish results using CUFSM.
The currently recommended reference is the following summary paper:
Schafer, B.W., Ádány, S. “Buckling
analysis of cold-formed steel members using CUFSM: conventional and
constrained finite strip methods.” Eighteenth International Specialty
Conference on Cold-Formed Steel Structures, Orlando, FL. October 2006. (pdf)
Direct Strength Method
The Direct Strength Method is a design method for cold-formed steel
members that uses cross-section elastic buckling solutions, determined
by tools such as CUFSM, as the primary input to the strength prediction.
The Direct Strength Method was created in the Thin-walled Structures
Research Group and much more information can be found on this page:
CUTWP is an elastic buckling analysis
tool employing only classical theory. Therefore classical global
flexural-torsional buckling solutions can be readily obtained while
ignoring cross-section distortion associated with local or distortional
buckling. The CUTWP tool may be downloaded from this web site:
All older versions of CUFSM,
including supporting materials are available in the
archive. Note CUFSM v2.5
and v2.6 provide standalone versions that run well on older PCs.
Note, the materials developed to
support CUFSM and the program CUFSM were both developed, in part,
through the sponsorship of research projects with the American Iron and
Steel Institute ( www.steel.org ) and
the National Science Foundation (
www.nsf.gov ). Any opinions, findings, and conclusions or
recommendations expressed in this material (or through this software)
are those of the author and do not necessarily reflect the views of the
National Science Foundation or the American Iron and Steel Institute.