Measures of structural redundancy in reinforced concrete buildings. II: Redundancy response modification factor R-R

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 R-R 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.