CUFSM Elastic Buckling of Thin-Walled Structures

professor ben schafer's thin-walled structures research group - johns hopkins university

Menu:
Background
What's new (version 3.12)
Tutorials
Download
standalone version
Matlab open source version
License and Distribution
Referencing CUFSM
Direct Strength Method
CUFSM vs. CUTWP

Sponsors

Screen shots from version 3.12:

input screen

properties and applied loading screen

post-processing results screen

input screen with new cFSM on

classification results in post-processor via cFSM

model results for D only analysis in post-processor

CUFSM

Elastic Buckling Analysis of Thin-walled Members

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.

Background
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 interactive manner.

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, b cross-section properties provided for user convenience have been corrected.)

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.

Tutorials

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, available through AISI or the Steel Framing Alliance and discussed further in this paper.

CUFSM 3.12 Tutorials

Download all hyperlinked tutorials in ppt format (start with the table of contents!)

Download all tutorials without hyperlinks in pdf format

Download individual tutorials only (see below)

Table of contents (ppt) (pdf)

Frequently Asked Questions - What is CUFSM? Why use it? (ppt) (pdf)

Overview of CUFSM features (ppt) (pdf)

Tutorial 1 - Learn the basics and interpret results (ppt) (pdf)

Tutorial 2 - Build a model from scratch and find Pcr (ppt) (pdf)

Tutorial 3 - Build a model using the template and find Mcr (ppt) (pdf)

Advanced Functions - B. conditions, springs, constraints, cFSM (ppt) (pdf)

Advanced Ideas - Defining buckling modes, higher modes.. (ppt) (pdf)

Advanced Matlab - Calling CUFSM from your own code (ppt) (pdf) (m-file)

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.

Download CUFSM version 3.12
Standalone version for PCs

download executable version
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 machines (preliminary testing on Win Vista also has been successfully completed.) 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 vcredist_x86.exe (available 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)

Matlab open source version for any platform

+ download all m-files

Installation: 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 source, Academic Free License v 1.2. Please provide a reference to the author (Ben Schafer) and note the version you are using. Archive of older CUFSM versions are also available for download. Contact schafer@jhu.edu with problems.

Referencing CUFSM
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: DSM homepage.

CUFSM vs. CUTWP

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: CUTWP homepage.

Archive

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.

Sponsors

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.

05/06/08 - schafer@jhu.edu -