On Thursday, September 27, 2018, Bastian Okto Bangkit SENTOSA, PhD student in Civil Engineering and Housing Sciences at the Laboratory for Design Optimization and Environmental Engineering (LOCIE), will defend his thesis entitled "Characterization of reinforced concrete structural elements through dynamic measurements."
The defense will take place at 1:30 p.m. in the HELIOS building, INES Training Room, on the Bourget-du-Lac campus.
Thesis summary
There are numerous dynamic measurement applications for existing buildings: checking the seismic vulnerability of structures, assessing the capacity of structures in post-seismic situations or after modifications to the surrounding area. Dynamic measurements are used to characterize the overall behavior of structures, which is linked, at the local level, to the behavior of structural elements. The work focused on studying the relationship between damage to reinforced concrete structural elements (beams, columns, and connections) and the decrease in the natural frequencies of the same structures. H- and T-shaped reinforced concrete frames were manufactured and tested in the laboratory under quasi-static cyclic loading. The displacements of the structures were determined simultaneously using displacement sensors and image analysis. After each loading/unloading cycle, dynamic measurements were taken using accelerometers. A multi-fiber model was developed to simulate the experimental results. Subsequently, analytical methods were also developed to quantify the damage state of the structures at the local and global levels. The introduction of stiffness factors at the connections allowed us to better approximate damage at the local scale. The decrease in natural frequencies is exploited using Rayleigh analysis and validated by experimental results. Finally, a global damage indicator is determined for each loading cycle. All these analytical results are used to correlate local behavior with the overall behavior of reinforced concrete structures. This approach can be used as a tool for evaluating structures and can be extended to the scale of a building. At LOCIE, we believe that the overall behavior of buildings is certainly influenced by soil-structure interaction, but at least as much by the quality of the connections between structural elements. There is a need to qualify these connections, whose variability in behavior can result from both implementation defects (reinforcement positioning, etc.) and structural aging. The main objective of this thesis is to propose a method for characterizing the connections between structural elements in order to calibrate a numerical model. These characterizations should be possible based on dynamic stress measurements. The first step in this work will be to characterize a connection on part of a structure. This will be done on a reinforced concrete portal frame. Subsequently, this method will be adapted to characterization within a building structure. To do this, we will use the concept of sub-models. A numerical model will be associated with this method for both the simple connection and the entire building. The thesis work will be based on the use and development of techniques for processing dynamic data; model reduction; laboratory experimentation (local scale and structural element scale); and multi-scale finite element numerical modeling.