(1) Select a preliminary member size with a section modulus, S,
S >/= M/Fdy
and bf/2tf complies with the structural steel being
(2) Calculate Py and the ratio P/Py. Determine the maximum
allowable d/tw ratio and compare it to that of the
section chosen. If the allowable d/tw ratio is less than
that of the trial section, choose a new trial section.
(3) Check the shear capacity of the web. Determine the
area, Aw, and the allowable dynamic shear stress,
Calculate the web shear capacity, Vp, and compare
design shear, V. If inadequate, choose a new trial
and return to Step 2.
(4) Determine the radii of gyration, rx and ry, and plastic
section modulus, Z, of the trial section from the AISC
(5) Calculate the following quantities using the various design
(a) Equivalent plastic resisting moment:
Mp = FdyZ
(b) Effective slenderness ratios, K*lx/rx and
K*ly/ry. For the effective length factor, K, see
Section 1.8 of the Commentary on the AISC
(c) Allowable axial stress, Fa, corresponding to the
larger value of K*l/r.
(d) Allowable moment, Mm, from Equation (109a) or (109b).
(e) F'e and "Euler" buckling load, Pe.
(f) Plastic axial load, Pp, and ultimate axial load,
(g) Coefficient, Cm, (Section 1.6.1, AISC Specification).
(6) Using the quantities obtained in Step 5, the applied
moment, M, and axial load, P, check the interaction
formulas, Equations (107) and (108). Both formulas must be
satisfied for the trial section to be adequate.