Moment-Rotation Response of Slender Steel I-Girders

Abstract

While it is well known that slender girders have less ductility than their compact counterparts, this reduction has not been explicitly quantified. This results in limitations on the use of slender girders, and consequently, potential reductions in economy. These limitations are particularly significant in the AASHTO moment redistribution procedures, which exclude the use of girders that fail to satisfy certain compactness requirements. Thus, this paper reports the results of finite-element analysis (FEA) that has been validated by experimental testing of a series of I-girders with plate width-to-thickness ratios and unbraced lengths exceeding the limits for use of these provisions. From the FEA results and the complementary experimental results, the ductility of this class of girders is quantified in terms of moment-rotation response. Furthermore, a moment-rotation model that may be used to represent the ductility of any I-girder that satisfies AASHTO’s criteria for general I-girders is proposed.