Tension-Field Design of Tapered Webs

This paper deals with the formulation of design guides for tapered webs based on post-buckling strength. Following the basic format and approach used in earlier studies and Baslers tension-field model, allowable stress expressions are derived for tapered webs. They are compared with the current AISC Specification. It is shown that for small or even moderately large tapering ratios, the average depth of the tapered segment can be used in the AISC prismatic girder design formula for tapered members. The results of this study can be used in the design of tapered roof girders of the gable frames commonly encountered. Beams and girders having small or moderate tapers comprise over 90% of tapered beams used in practice. The allowable shear stress of such beams may be obtained either by employing the present AISC provision based on tension-field acton, with the average depth replacing the uniform depth, Eq. (1a), or it may be obtained by employing Eq. (17) or(19). The latter expressions will give results that are somewhat more accurate.