In Turkey, steel design guidelines have been updated two years ago. Specification for Design and Construction of Steel Structures superseded TS648 standard. The objective of this study is to determine whether the strength of a rolled I-shaped steel flexural member designed using TS648 is sufficient based on the "Specification" by comparing the design guidelines in both design documents. Even though there are some differences in the design philosophies of "Allowable Stress Design" used in TS648 and "Allowable Strength Design" used in the Specification, it is believed that under "working loads", the "allowable" values of internal forces/moments in structural steel members can be computed using the provisions given in both design documents and the results can be compared to evaluate whether a member designed using TS648 needs strengthening. With this purpose, the strength predictions of both design documents for rolled I-shaped members widely used in Turkey as flexural members under major/minor axis bending and shear in the plane of the web/flanges are computed for three different steel grades and different member lengths and the results are compared. It is shown that, for all studied sections and steel grades, TS648 gives more conservative results than the Specification in the design of members subjected to minor axis bending and shear in the plane of the web/flanges. On the other hand, for members subjected to major axis bending, TS648 may remain on unconservative side for some member lengths. However, it is recognized that, for all studied sections and steel grades, the strength predictions of TS648 are at most 13% greater than those of the Specification.