On efficient design of earthquake resistant moment frames

This paper introduces a number of simple findings that lead to the efficient design of system based earthquake resisting moment frames. A system based design is defined as one that leads to minimum drift and minimum weight solutions, for code recognized seismic frameworks, without resorting to complicated numerical analysis. These findings are used to form an algorithm, which in turn leads to closed form solutions for system-specific performance-based design of earthquake resisting moment frames. The results of some of these findings may be summarized as follows; the efficient design of a representative closed loop sub-frame is one involving beams and columns of equal strength and stiffness, a design may be said to be efficient when the demand/capacity ratios of all of its members are as close to unity as possible, the magnitude of a mid-span concentrated load may be considered small if it is less than half its plastic collapse value acting alone on the same beam.