Partial-Span Live Loading Effects on the Design of Multistory Multibay Steel Moment Frames

A critical live load pattern is the live load pattern that will produce the maximum axial force and/or bending moment in a structural member under consideration. Structural engineers commonly select the critical live load pattern from full-span live load patterns rather than partial-span live load patterns. In order to identify the most critical live load pattern, a three-story, two-bay steel moment frame design example is presented in this paper. In this design example, both first-order and second-order analyses are used for the determination of the required strength of the columns, while the effective length method is used for the determination of the design strength of the columns. The results of the example indicate that the effects caused by partial-span live load patterns are more critical than those caused by full-span live load patterns, not only in the computation of the required strength of the structural members, but also in the calculation of the maximum lateral displacement of the entire frame.