Quantification of the effects of different uncertainty sources on the seismic fragility functions of masonry-infilled RC frames

Abstract

The presence of masonry infills is known to have a significant effect when assessing the seismic vulnerability of reinforced concrete (RC) structures, and including these elements in the numerical modelling has become imperative. In computationally-intense probabilistic analyses such as those integrated in performance-based earthquake engineering (PBEE) frameworks, the simulation of the masonry infills is often performed using the single strut approach/technique. Despite the advantages of this modelling approach, it can be related to several sources of uncertainty that can impact probabilistic performance results such as fragility functions. In this context, the proposed study examines the effect of the uncertainty associated to the parameters of the strut model representing the infills, and to the definition of global limit state thresholds reflecting the lateral deformation capacity of infilled structures. The study considers RC structures of different sizes and with different infill configurations, and the relative importance of both sources of uncertainty is analysed by comparing fragility functions defined for different limit states. The comparisons are first performed qualitatively followed by a statistical analysis based on the results of several two-sample tests. Results indicate that, depending on the infill modelling options and on the way limit state values are considered, the corresponding fragility functions can be significantly different. These results highlight the need for further research dedicated to the uncertainty quantification and propagation associated with limit state values for infilled structures and with empirical models that provide parameters for simulating the behaviour of infills under earthquake loading.