CFS Version 4 Changes
Released January 2003

2001 AISI Specification

CFS now supports the 2001 Edition of the AISI Standard "North American Specification for the Design of Cold-Formed Steel Structural Members". This includes ASD and LRFD for U.S. and Mexico, as well as LSD for Canada. CFS continues to support ASD and LRFD for the 1996 Specification with Supplement 1 (1999). Specific changes from 1999 to 2001 are as follows:

  • Section A2.1 Additional materials (ASTM A1003, A1008, A1011). Changed SQ designations to SS. Changed HSLA designations to HSLAS.
  • Section B2.1 l calculation is presented differently.
  • Section B2.3 Change to effective width calculation for ho/bo>4.
  • Section B4.2 Change to plate buckling coefficient calculation.
  • Section B5.1 New provision for mutliple intermediate stiffeners.
  • Section C2 Canada provisions differ from U.S.
  • Section C3.1 Canada fb factor is different from U.S.
  • Section C3.1.2 Cb and CTF are no longer required to be 1 for combined axial and bending.
  • Section C3.2.1 Changes to shear strength equations.
  • Section C3.4 All new web-crippling strength provisions. A new web-crippling parameter is introduced: whether the bearing flange is fastened to the support. Additional web classifications are defined: cee, zee, hat, deck.
  • Section C3.5 Changes to web-crippling interaction equations.
  • Section C4 Canada fc factor is different from U.S.
  • Section C4.5 New provision for modified KL/r on built-up members.
  • Section C4.6 Canada fc factor is different from U.S.
  • Section C5.2 The additional PL/1000 moment on angle sections is not required if fully effective.
  • Section C6.1 Canada fb factor is different from U.S.
  • Section C6.2 Canada fc factor is different from U.S.
2002 ASCE Specification

CFS Version 4.1 supports the 2002 Edition of the ASCE Specification for the Design of Cold-Formed Steel Structural Members (ASCE-8-02). Specific changes from 1990 to 2002 are as follows:

  • Section 2.4.2 Calculation of plate buckling coefficient, k, is presented differently.
  • Section 3.3.1.2 Change to calculation of Cb.
  • Section 3.5 fc has been removed from the magnification factor a.
  • Appendix A Additional materials: UNS S20400 Annealed and UNS S20400 1/4 Hard.
Section Enhancements
  • The default thickness for new sections is now based on the last thickness used.
  • The bend radius inputs are clarified as being the inside bend radius.
  • If you change section geometry after setting an override for Cw or J, a caution message will be displayed when calculations are performed.
  • When an old section file is opened containing elements with 'Single' webs, a caution message is displayed informing you to review the web types since there are additional classifications now.
  • Torsion warping stress properties wn and Sw can be calculated for open and closed shapes (Version 4.11).
Analysis Enhancements
  • The Analysis Wizard now allows up to 20 spans (the limit was previously 10 spans).
  • The Analysis Wizard now lets you define the load angle for beam analyses.
  • Mutliple sets of load combinations are available from which to choose, including ASCE-7-98 (ASD and LRFD), ASCE-7-95 (ASD and LRFD), AISI 2001 LSD, AISI 1996 (ASD and LRFD), and IBC 2000 (ASD and LRFD). The Analysis Wizard will also let you choose which combinations within a set to include in the analysis.
  • User-defined load combinations can also be created and saved for use in new analyses.
  • There is now an option to use inflection points as brace points, specific to each load combination.
  • The graphic display of the analysis members now provides a visual representation of fully braced regions and one-flange bracing.
  • When changing a member start or end point, supports and loads will move with it upon user confirmation.
  • The limits on input values for member lengths and applied loads have been expanded so that any realistic values can be entered.
  • Shear, moment, and deflection diagrams show the magnitude at any point along the member length as you move the mouse pointer over the diagrams.
  • Diagrams are now available as envelope diagrams of all combinations.
  • You can view a text report for the reactions, shears, moments, deflections, and inflection points associated with a set of diagrams.
Other Enhancements
  • CFS runs in "light" mode until a license for the full version is obtained. Licensing can be provided using a key code specific to each user in lieu of a hardware lock.
  • A copy of the license order form is included with the program.
  • Several of the 1996 AISI Design Manual examples are included with the software.
  • All library sections have been updated to use the new web classifications required for the 2001 Specification.
  • The section library builder is now included in CFS. So you can create your own libraries of commonly used shapes.
  • On reports for member checks and web-crippling checks, interaction equations that exceed their limits are shown in red.
  • On web-crippling reports, strengths are calculated even if some Specification limits have been exceeded. Messages are still provided for exceeded limits.
  • When copying an entire report, the report heading is included for pasting into another application.
  • Page numbers have been added to printouts to help keep long reports in order.
  • The size and position of the input windows is saved for the next time you start CFS.
  • Program settings are stored based on your computer login, so different users can retain their individual settings on the same computer.
Section Corrections
  • Due to an AISI Specification interpretation issued in August 2000, a change was made in CFS for determining when the strength increase due to cold work of forming is allowed. Rather than checking simply for a fully effective section, the element reduction factor, r, must be 1 for all elements. An edge stiffener can still have a reduction in area even when r is 1, but this does not prevent the use of the strength increase. Additionally, the check for r=1 is performed at the stress Fya instead of Fy. If satisfied at Fy but not at Fya, the highest value of Fya is determined for which r=1 for all elements.
  • Previously, the fully braced axial compressive strength was calculated using the effective net section, and the overall buckling strength was calculated using the effective full section. This has been corrected to agree with the Specification so that the effective section is always calculated from the net section.
  • Minor correction to the calculation of plate buckling coefficient k for multiple intermediate stiffeners.
  • Minor correction to the calculation of qs for shear strength calculation with holes.
  • Consecutive collinear elements are now treated as elements with intermediate stiffeners of zero size.
  • Material properties are limited to a yield strain of 0.005. This limit was incorrectly applied to shear yield, but the shear yield must still be less than the tensile yield.
Analysis Corrections
  • The moment reduction, R, should not be applied to the negative moment regions adjacent to supports.
  • For cantilevers, set Cb and Cm to 1. But CTF can be less than 1.
  • For fully braced analysis beams, set Cb and Cm to 1 for display (has no effect on strength).
Other Corrections
  • Corrected printout error with concentrated load magnitudes.
  • Sometimes the web-crippling check could show a distance to the end of the member as a small negative number. This is now shown as 0.
  • The selected design method and specification are now saved for the next time you start CFS.
  • For some computers with Windows 2000 or later operating systems, the display of the report fonts was faulty.
  • SSMA Library Changes:
    • S125 sections use a 3/16" lip now instead of a 3/8" lip.
    • Hole sizes changed to D/2 or 2", whichever is smaller.
    • Section 1000S162-68 web depth was corrected to 10" (33 and 50 ksi).
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