“How safe and robust are our existing structures?” Although a lot of research concerning the structural safety level has been performed during the last decades, solving this issue for existing structures is still a challenging problem which engineers are more and more often confronted with. This is mainly because there is still not a proper framework established for assessing the safety of ageing or even deteriorated structures, nor is it clear how to deal with the numerous uncertainties occurring in the assessment process.
Consequently, assessing robustness for such structures becomes even more difficult and much more research efforts are needed. Nevertheless, there is an urgent need for such analyses, as the numerous casualties of the World Trade Center collapse in New York on September 11th, 2001 are an unfortunate reminder of the major societal impact a progressive collapse can have. Therefore, this research project will develop a fullprobabilistic methodology for quantifying the safety level and robustness of existing structures, accounting for membrane actions and using numerical simulations based on Bayesian updating techniques to cope with the extremely high structural complexity and the high number of uncertainties involved. As a result, the developed methodology will offer a tool to designers to take proper decisions and will constitute an important step forward into the development of robustness-oriented structural assessment guidelines for existing structures.