25 Ene Phd thesis: Low-cycle fatigue prediction of elastoplastic energy dissipators for earthquake resistant structures
Enric Simon Madrenas defended his PhD thesis entitled “Low-cycle fatigue prediction of elastoplastic energy dissipators for earthquake resistant structures”, advised by Dr. Francesc Xavier Cahís Carola, researcher of AMADE. The defence was held at the Polytechnic School of the University of Girona on November 17, 2021.
The elastoplastic energy dissipators, also known as hysteretic energy dissipators, have been increasingly introduced in earthquake-resistant structures. They are easy to exchange devices able to concentrate most of the earthquake energy input, allowing both lateral deformation and damage control of buildings. The energy dissipation is due to sustained plastic deformation produced in cyclic deformation reversals in earthquake episodes. Reliable devices would sustain stable deformation in a sufficient number of cycles with no sign of deterioration until their last hysteresis loops. Low-cycle fatigue models are meant to predict their failure.
The increasing computational power allows modeling the response of buildings in earthquakes through non-linear dynamic analysis. This analysis becomes simpler when plasticity is mainly concentrated in elements and when their response is predictable. When it comes to elastoplastic devices, there are different models to predict their hysteretic response thought time and sustaining plastic deformation. The more accurate are these models, the more accurate will be the overall response of a structural system and the sustained damage of their dissipation devices.
Focused on providing reliable tools to predict fatigue failure in elastoplastic devices, this thesis has analyzed both the response of low-cycle fatigue models and hysteretic models. Departing from the state-of-the-art of both fields, we have selected which models would be more appropriate to model the response and fatigue of elastoplastic energy dissipators, and we have proved its validity by comparing its predictions with experimental data. Finally, we have proposed two new low cycle-fatigue models which are able to accurately predict the failure of devices whose dissipative part stands a nearly uniformly distributed plastic deformation produced by uniaxial stress. Among such devices are the Buckling-Restrained Braces, the more used nowadays, and the well-known TADAS and ADAS devices.