The effects of the element ductility capacity, the flexibility of beams (in terms of the beam span-to-beam depth ratio), the flexibility of columns (in terms of column slenderness ratio), and the level of gravity loads on the structural redundancy of plane frames are studied. A simplified expression to evaluate the redundancy response modification factor RR and account for the effects of plan and vertical irregularity on the strength of framing systems in a direct and scientific manner is presented. The required parameters involved in the expression can be obtained from a nonlinear pushover analysis of a structure. The redundancy response modification factor is evaluated for a group of two-dimensional frames with 3, 5, and 7 stories and 1, 2. 4, and 6 bays. Finally a simplified expression for the reliability or safety index p is formulated and applied to the same group of structures.
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