LaBoube, Roger A.

English

Missouri University of Science and Technology (Missouri S&T): Scholars' Mine

Missouri University of Science and Technology Scholars' Mine AISI-Specifications for the Design of Cold-Formed Steel Structural Members Wei-Wen Yu Center for Cold-Formed Steel Structures 01 Jan 2004 Summary Report: Strength of Single L-headers Roger A. LaBoube Missouri University of Science and Technology, laboube@mst.edu Follow this and additional works at: https://scholarsmine.mst.edu/ccfss-aisi-spec  Part of the Structural Engineering Commons Recommended Citation LaBoube, Roger A., "Summary Report: Strength of Single L-headers" (2004). AISI-Specifications for the Design of Cold-Formed Steel Structural Members. 76. https://scholarsmine.mst.edu/ccfss-aisi-spec/76 This Technical Report is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in AISI-Specifications for the Design of Cold-Formed Steel Structural Members by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact scholarsmine@mst.edu.                  research report  Summary Report:  Strength of Single L-Headers    R E S E A R C H  R E P O R T  R P 0 4 - 3   2 0 0 4  R E V I S I O N  2 0 0 6   American Iron and Steel Institute    Summary Report: Strength of Single L-Headers i DISCLAIMER The material contained herein has been developed by researchers based on their research findings and is for general information only.  The information in it should not be used without first securing competent advice with respect to its suitability for any given application.  The publication of the information is not intended as a representation or warranty on the part of the American Iron and Steel Institute, Steel Framing Alliance, or of any other person named herein, that the information is suitable for any general or particular use or of freedom from infringement of any patent or patents.  Anyone making use of the information assumes all liability arising from such use.                                    Copyright 2004 American Iron and Steel Institute / Steel Framing Alliance Revised Edition Copyright 2006 American Iron and Steel Institute / Steel Framing Alliance ii Summary Report: Strength of Single L-Headers PREFACE This report summarizes a previous test program conducted at the NAHB Research Center, and proposes a design methodology for single L-headers under gravity load. The findings provided a basis for the AISI Committee on Framing Standards to establish design options for single L-headers in the AISI Standard for Cold-Formed Steel Framing – Header Design.   Research Team Steel Framing Alliance Summary Report Strength of Single L-Headers R. A. LaBoube January 30, 2004   Introduction  Based on a test program performed at the NAHB Research Center (NAHB, 2003), a design methodology is proposed for single L-headers under gravity load.  This report briefly summarizes the NAHB test program and presents justification for a proposed design method.  NAHB Test Program  The test specimens were single span assemblies consisting of the top and bottom track, cripple stud, and simulated wall stud.  A single L-header was affixed to the top track as illustrated by Figure 1.    Page 1 of 4        Figure 1  Single L-Header Test Assembly  Using No. 8 self-drilling screws, the L-header was screw attached to both the top track and to each stud as depicted by Figure 1 and Figure 2.  Except that only a single L-header was installed, the construction of the tested assemblies met the installation requirements of the Header Standard (AISI, 2001), per Figure A1.1.2 for double L-headers.  Figure 2  Typical L-Header Attachment to Track  To simulate in-situ loading of the header, each single span assembly was subjected to concentrated load at the mid-span cripple stud (Figure 3).  Each assembly was tested to failure.   Figure 3  Load Application Evaluation of Test Data  A total of 18 single L-header assemblies were tested to failure.  Material tensile test properties are summarized in Table 1.       Page 2 of 4 Table 1 - Material Tensile Properties for the L-Headers   Each assembly was tested as an assumed simple span beam with a concentrated load at mid-span.  The test failure load, Pu, and the corresponding simple span moment is given in Table 2,  Mtest = PuL/4                     (1)  where L = 48 inches.  Using the AISI Specification (AISI, 1999), the elastic section modulus of the effective section calculated at f = Fy in the extreme compression fibers, Sec, was computed for each L-header test assembly.  Only the single L-header geometry was considered when computing Sec.   The nominal moment capacity, Mng, was computed using Eq. B3.1.1-1 from the 2001 Header Standard (AISI, 2001) as  Mng = Sec Fy                       (2)  where Fy = yield point as given in Table 1.      Page 3 of 4 Table 2 - Test and Analysis Results Section Fy Sec Mng Pu Mtest Mtest/Mn  ksi in3 in-kips kips in-kips  600L150-33 36.8 0.285 10.49 1.87 22.44 2.140 600L150-33 38.2 0.288 11.00 1.89 22.67 2.060 600L150-33 37.5 0.287 10.76 1.70 20.41 1.897 600L150-43 41.1 0.398 16.36 2.02 24.22 1.480 600L150-43 39.9 0.410 16.36 2.18 26.16 1.599 600L150-43 40.5 0.406 16.44 2.34 28.12 1.710 600L150-54 53.7 0.509 27.33 2.81 33.74 1.235 600L150-54 52.8 0.516 27.24 2.91 34.88 1.280 600L150-54 54.1 0.503 27.21 2.81 33.71 1.239 800L150-33 36.9 0.400 14.76 2.19 26.28 1.780 800L150-33 37.2 0.383 14.25 2.20 26.42 1.855 800L150-33 37.1 0.387 14.36 2.26 27.17 1.892 800L150-43 39.8 0.642 25.55 2.81 33.72 1.320 800L150-43 38.7 0.647 25.04 2.77 33.22 1.327 800L150-43 40.1 0.643 25.78 2.93 35.20 1.365 800L150-54 56.5 0.797 45.03 3.19 38.26 0.850 800L150-54 54.9 0.801 43.97 3.13 37.60 0.855 800L150-54 53.8 0.803 43.20 3.34 40.03 0.927      Mean 1.489      Std. Dev. 0.400      COV 0.2689   Conclusion  Based on the computed ratios of Mtest/Mng listed in Table 2, Equation 2 (Eq. B3.1.1-1 from the 2001 Header Standard) is an acceptable relationship for evaluating the gravity moment capacity of the single L-header assemblies tested, except for the 8 inch deep 54-mil L-headers which did not achieve design strength.  The design methodology should be adjusted to reflect this observed behavior.  Using the provision of Chapter F1 of the AISI specification, Ω = 1.67 and φ = 0.90.  These are the same factors prescribed in the 2001 Header Standard (AISI, 2001) for the design of double L-headers.   As with previously tested double L-headers, neither pure shear or combined bending and shear were failure modes in the test program.  Also, web crippling and combined bending and web crippling are precluded from occurring because of the requirement that concentrated load applications occur at cripple stud locations.  Recommendation  The 2001 Header Standard (AISI, 2001) should be revised to incorporate single L-headers within the ranges tested.  References  AISI (1999), Specification for the Design of Cold-Formed Steel Structural Members, 1996 Edition with 1999 Supplement, American Iron and Steel Institute, Washington, D.C.  AISI (2001), Standard for Cold-Formed Steel Framing – Header Design, American Iron and Steel Institute, Washington, D.C.  NAHB (2003), “Testing of Steel Single L-Headers”, U.S. Department of Housing and Urban Development, Washington, D.C.  Page 4 of 4                        1201 15th Street, NW Suite 320 Washington, DC 20005  www.steelframing.org  American Iron and Steel Institute   1140 Connecticut Avenue, NW Suite 705 Washington, DC 20036  www.steel.org    Research Report RP-04-3 

Summary Report: Strength of Single L-headers

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Summary Report: Strength of Single L-headers

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