scope:

In a previous paper allowable stress formulas for the proportioning of web-tapered members were proposed. The allowable stress on compression and in bending wer defined by modifying the respective current AISC formulas for prismatic members. This was done by adjusting the length of a prismatic column or beam having the same cross-section dimensions as the smaller end of the tapered member, such that its critical stress was the same as the tapered column or beam. For the case of combined compression and bending of a tapered member, again the current AISC formulas were used with the substitution of Fay, Fey, and Fby and the modification of Cm. Also effective length factors for tapered columns were included in Ref. 1. This present paper deals with results of some further considerations of the allowable bending stress formula for tapered beams. There are basically two aspects which make AISC allowable bending stress formula conservative for laterally unsupported beams: the use of partial lateral buckling resistance of the beam (the designer works with the larger stress given by 1.5-6 or 1.5-7) and no allowance is given to end constraints different from siple supports