Robustness Assessment of Reinforced Concrete Frames under Progressive Collapse Hazards: Novel Risk-Based Framework

Abstract

Robustness assessment is an important component for performance-based progressive collapse design. However, existing methods either do not consider the cascading failure feature of progress collapse, or fail to recognize the randomness in material, geometrical and loading parameters. This paper presents a novel robustness assessment methodology for progressive collapse design of reinforced concrete frames. The proposed methodology includes several novelties: First, it uses a new risk-based robustness index recently developed by the authors. The index quantifies the whole spectrum of risk caused by initiating hazardous events. Second, it includes a unique directional simulation technique, making probabilistic nonlinear pushdown analysis a computationally affordable task. Finally, the assessment can assist in determining if an enhancement design is warranted for such a low-probability-high-consequence event. The study examined four different frame designs to evaluate the effectiveness of seismic and progressive collapse design provisions. The Alternate Path Method (APM) was shown to improve structural robustness significantly, although achieved with considerable additional cost. Ductility designed for seismic loading was also shown to be beneficial for structural robustness against progressive collapse.