A Beginner's Guide to the Steel Construction Manual, 14^{th} ed. Chapter 8  Bending Members © 2006, 2007, 2008, 2011 T. Bartlett Quimby 

Section 8.3.2 Shear Strength Limit State Last Revised: 11/04/2014 The computation for the shear strength of steel sections is found in SCM Chapter G. Section G2 investigates the prebuckling strength of stiffened and unstiffened webs. Section G3 considers post buckling strength (or the strength related to tension field action). This text focuses of section G2. The Limit State The basic limit state follows the standard form. The statement of the limit states and the associated reduction factor and factor of safety are given here:
The values of V_{u} and V_{a} are the LRFD and ASD factored shears, respectively, applied to the member. In this case V_{n} is the nominal shear strength of the member is computed using SCM equation J31: V_{n} = 0.6F_{y}A_{w}C_{v} Where:
Computing A_{w} The computation of A_{w} is dependent on the type of member and the direction of the shear on the cross section.
Computing C_{v} Since C_{v} accounts for buckling behavior of the web, it must account for the standard three ranges of the buckling curve. The general slenderness parameters, l_{p} and l_{r}, can be extracted from equations found in SCM G2.1(b):
The general member slenderness, l, is h/t_{w}. When l < l_{p} then the member is compact, is not subject to shear buckling, and C_{v} = 1 (SCM Eq G23). When l_{p} < l < l_{r} then the member is noncompact, is subject to inelastic buckling, and C_{v} is determined using the linear transition equation SCM Eq G24. This equation is a linear interpolation between the limits of the inelastic region. When l_{r} < l then the member is slender, is subject to elastic buckling, and C_{v} is determined using the Euler style equation SCM Eq G25. A part of the computation is the term k_{v}. The specification for the computation of k_{v} is found in SCM G2.1(b)(i & ii). For angles and rectangular HSS & box members this factor is further specified in SCM G4 and G5. This factor accounts for the presence of stiffeners. It is a function of the clear distance between stiffeners, a, and h. Note that increasing k_{v} increases the slenderness limits l_{p} and l_{r}, thus increasing the shear strength of noncompact and slender webs by shifting the buckling curve to the right. Sample Spreadsheet Calculation The following spreadsheet example computes the shear capacity, V_{n}, for a typical W section. The input values are in the grey shaded cells and the result in the yellow highlighted cell.
<<< Previous Section <<< >>> Next Section >>>
