The Role of Uncertainties in Structural Engineering Problems: How to Manage Them in Simulation and Design

The problem of how to manage uncertainties when modeling or designing an engineering structure is briefly addressed here. Uncertainties may be relevant in the case of real structures, due to intrinsic variability of mechanical and physical properties as well as to the lack of knowledge when information are scarce and/or subject to some errors, for instance related to the test procedure. It is shown that the two mentioned sources of uncertainties must be treated in different ways, being the first unavoidable, and the second dependent on the experimental procedure adopted by the experimentalist/analyst. Different kinds of uncertainties should be then treated in different ways. The use of probabilistic tools in the first case and fuzzy number methods for the latter is studied in the first example, concerning the estimate of the strength of the concrete from a number of compression tests. The second problem addressed here concerns the identification procedure of the mechanical properties of a simple structure from dynamic test results. Also in this case, uncertainties can be due to the intrinsic variability of the properties to be identified, but also to the errors introduced in the adopted experimental procedure. Some ideas of the next steps in the research will end the paper.