Thesis defence A.V. van de Graaf: brittle failure
02 May 2017 10:00 - Location: Aula, TU Delft - By: webredactie TU Delft
Sequentially linear analysis for simulating brittle failure. Promotor 1: Prof.dr.ir. J.G. Rots (CiTG), Promotor 2: Dr.ir. M.A.N. Hendriks (NTNU, Noorwegen).
The numerical simulation of brittle failure at structural level using nonlinear finite element analysis remains a challenge due to robustness issues. To cope with convergence problems, sequentially linear analysis (SLA) was developed which exploits the fact that a linear analysis is numerically stable. By assuming a stepwise material degradation, the so-called saw-tooth law, we are able to approximate the nonlinear structural response by a series of scaled linear analyses. At the end of each linear analysis, the stiffness and material strength are reduced for the most affected point in the model which triggers a stress redistribution. In this dissertation, three topics are addressed to broaden the application of SLA. In the first place, an improved way to define saw-tooth laws is proposed. Saw-tooth laws are also generated for material models which had not been combined with SLA previously. In the second place, proposals are presented to account for Coulomb friction in SLA-based simulations. Finally, an alternative strategy is presented to deal with non-proportional loading which is based on a constrained optimization. The objectivity of the improvements and extensions is verified by analyzing four case studies. In addition, the effectiveness of the new developments is demonstrated for two larger examples, namely a masonry wall loaded in shear and a downsized masonry façade subjected to non- uniform settlements.
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