Performance-based risk optimization approach for progressive collapse of reincorced cocrete buildings

Abstract

The design of reinforced concrete (RC) frames considering progressive collapse is a complex problem due to the large impact of element removal on structural loads, hence also on strengthening costs, in spite of its low probability of occurrence. The candidate and his supervisor in Brazil are pioneering the development of novel reliability-based cost-benefit analysis for such designs, as described in three recently published papers. It became evident to the authors that: a) usual design conditions must be considered as constraints in the optimization analysis; b) the large costs of strengthening a structure to support loss of a load-bearing element are only justified if the threat is significant (column loss probability above a given threshold level); and c) performance-based approaches are more representative of the damage progression than the simple consideration of failure-survival. The probability of complete loss of a column due to abnormal loading is naturally smaller than the probability of some damage to the same column, leading to loss of stiffness and partial load redistribution. A performance based approach to the progressive collapse problem would integrate the different threats which may cause column damage and their probabilities, and fragility curves accounting for partial damage states of such columns could be used. Therefore, in order to enhance our risk optimization of reinforced concrete structures subjected to progressive collapse due to column loss, we would like to count with the expertise of Prof. Fulvio Parisi, from the Department of Structures for Engineering and Architecture of University of Naples Federico II, Italy. Prof. Parisi is chosen for this research abroad due to his vast expertise in the probabilistic performance-based assessment of RC structures under progressive collapse. The expertise of Prof. Parisi is complementary to that of Prof. Beck, as Prof. Parisi is an expert in the linear and non-linear behavior of RC structures. The advice of Prof. Parisi will be fundamental to formulate the performance-based risk optimization objective functions, also the rational choice between specific methodologies regarding structural analysis. His specialties in seismic design, progressive collapse simulation and structural robustness would, by themselves, justify the overseas supervision by Dr. Parisi. However, his additional expertise in reliability analysis and risk assessment allows a much easier compatibilization between all the research fields involved in this proposal. Hence, the research that will be carried out during the internship period abroad aims to formulate and solve the optimal risk design problem of usual RC structures subjected to progressive collapse within an adequate performance-based approach, providing a clear advance of the frontiers of knowledge. (AU)