PhD exam

Angelica Rosso defended successfully her PhD thesis "Out-of-plane stability of thin reinforced concrete walls under seismic loading". The members of his committee were Prof. M. Kowalsky (North Carolina State University, US), Prof. B. Stojadinovic (ETHZ), Prof. A. Muttoni (EPFL), Prof. T. Keller (EPFL, exam president) and Dr. João Almeida and Prof. Katrin Beyer (PhD advisors).

In her PhD thesis, Angelica treats the out-of-plane stability of reinforced concrete walls with only a single layer of vertical reinforcement. Such walls are frequently used in some South American countries, such as Colombia, in which construction material is relatively expensive. Existing research addresses only the out-of-plane stability of walls with two layers of reinforcement but walls with a single layer of reinforcement might be considerably more prone to such stability problems. The out-of-plane instability develops when the wall is subjected to cyclic in-plane loading, which leads to tension-compression loading in the boundary element.

The thesis starts by describing full-scale cyclic tests on thin single-layered walls under axial-shear-flexure, as well as an experimental program on axially loaded boundary elements. The analysis and interpretation of the advanced instrumentation data provide unique findings on the out-of-plane instability, both at the global and local levels. Angelica then resorts to state-of-the-art numerical simulation, using both nonlinear beam and shell elements, to further extend the results of the experimental tests. Resulting from these efforts, an improved equivalent boundary element model is proposed, which reliably estimates the critical tensile strain triggering out-of-plane wall instability. Angelica’s thesis concludes with the development of an advanced mechanical model for assessment purposes, which is based on a set of assumptions embodying the most important concepts and conclusions obtained throughout her work.