On Thursday, September 27, 2018, Bastian Okto Bangkit SENTOSA, a PhD student in Civil Engineering and Habitat Sciences at the Laboratory for Design Optimization and Environmental Engineering (LOCIE), will submit his thesis "Characterization of reinforced concrete structural elements by dynamic measurements".
The defense will take place at 1:30 pm, in the HELIOS building, Salle academics INES, on the Bourget-du-Lac campus.
Summary of the thesis
There are numerous applications for dynamic measurements on existing buildings, such as verifying the seismic vulnerability of structures, and monitoring the capacity of structures in post-seismic situations or after modifications to their surroundings. Dynamic measurements are used to characterize the overall behavior of structures, which is linked locally 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 natural frequencies of the same structures. H-shaped and T-shaped reinforced concrete portals were fabricated and tested in the laboratory under cyclic quasi-static loading. The displacements of the structures were determined simultaneously using displacement transducers and image analysis. After each loading/unloading cycle, dynamic measurements were taken using accelerometers. Multifiber modeling was developed to simulate the experimental results. Analytical methods were then developed to quantify the state of structural damage at local and global scales. The introduction of stiffness factors at the connection level has enabled 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 stress cycle. All these analytical results are used to correlate local behaviors with global behaviors of reinforced concrete structures. This approach can be used as a structural assessment tool and extended to the building scale. 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 behavioral variability can stem from both implementation faults (positioning of reinforcement, etc.) and structural aging. The main aim of this thesis is to propose a method for characterizing connections between structural elements, in order to be able to calibrate a numerical model. These characterizations were to be based on dynamic load measurements. The first step in this work will be to characterize a connection on a structural part. This will be done on a reinforced concrete portal frame. The method will then be adapted to characterize a building structure. To do this, we will use the concept of sub-models. A numerical model will be associated with this method, both for the single connection and for the building as a whole. The thesis work will be based on the use and development of techniques involving dynamic data processing; model reduction; laboratory experimentation (local scale and structural element scale) and multi-scale finite element numerical modeling.