Welcome to CFS, the comprehensive cold-formed steel component design software. The endless variety of shapes and sizes of cold-formed steel members, combined with the complex failure modes of this type of construction, results in difficult and time-consuming structural calculations to determine the strength of such members.
The American Iron and Steel Institute (AISI) has published numerous editions of the "Specification for the Design of Cold-Formed Steel Structural Members" over the years. The 1986 Edition introduced a significant change to member local buckling strength determination called the "Unified Approach". This approach requires the computation of effective widths for each element of the cross section, based on the slenderness of the element, the stress in the element, and the degree of edge stiffening. The effective section properties are then used to determine the strength. This is often an iterative process due to shifting of the neutral axis and thus changes in stress level.
The first version of CFS was written in 1987 to assist the engineer in performing these calculations. From the start, the primary goal was to handle any general shape of uniform material thickness. The internal calculations were developed from mathematically rigorous derivations for arbitrary shapes, including integration through the bend radius segments and across the material thickness. Furthermore, the calculations of torsional properties, which are often crucial in the determination of member strength, use exact integrations for thin-walled sections that incorporate the bend radius segments as well.
Just as important was the goal to make the application easy to use. A flexible method of defining cross section shapes was devised that simply requires the length and angle of consecutive connected elements, and the bend radius between each of them. Additionally, the graphical interface provides the user with immediate visual confirmation of the inputs as they are given.
The CFS application has evolved through changes in appearance and functionality, numerous enhancements, and changes to the specification provisions. Here is a history of published editions of the AISI Specification for the Design of Cold-Formed Steel Structural Members:
This version of CFS provides calculations based on all the above editions since 2001, including ASD and LRFD methods (U.S. and Mexico) and the LSD method (Canada). Also, the 2022 Edition of the ASCE Specification for the Design of Cold-Formed Stainless Steel Structural Members (ASCE 8-22) is used for ASD and LRFD methods with stainless steel materials.
It is strongly recommended that the user of this software have a good understanding of these specifications. CFS is intended to assist the engineer in performing the necessary structural calculations for cold-formed steel structures, and to increase your productivity. However, it cannot replace responsible engineering practice and judgment.
Great effort has been made to ensure that the computations performed by CFS are correct within the guidelines and assumptions stated in this documentation. The author takes no responsibility for any errors that occur. The interpretation of the output and the application of such data is solely the responsibility of the user.
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