# The Dynamic Response of an Arch Dam During a Record Low-Intensity Earthquake
## 5 Conclusions  
Evaluating the dynamic behavior of structures is an important tool because it makes it possible to detect the structural changes that have occurred during a specific period, based on the evolution of the dynamic behavior. Forced vibration tests on concrete dams to determine dynamic behavior continue to be one of the most reliable techniques in this area. Complementing these results with the installation of continuous dynamic and seismic monitoring systems provides a robust experimental methodology to assess structural behavior.  
To interpret the results of the dynamic monitoring of the Baixo Sabor dam, a numerical model was developed, representing the dam-foundation-reservoir system. In this model, the reservoir is discretized with finite elements, which makes it possible to simulate the effect of the interaction of the water with the dam and the foundation more accurately than the traditional [PERSON]'s method of added masses. Various discretizations of the reservoir were made, corresponding to different water levels. The values of the eigenfrequencies determined numerically showed good agreement with the results of the forced vibration tests for two water levels, as well as the subsequent continuous dynamic monitoring.  
The numerical model thus experimentally calibrated was used to analyze the behavior of the dam during a low-intensity earthquake recorded by the seismic monitoring system. The numerical simulation of the event requires appropriate dynamic boundary conditions to avoid wave reflections. The lateral boundaries are linked to free-field meshes and the bottom boundary is a non-reflecting boundary where the seismic input is applied in the form of a stress record. The recorded response in the seismometer located at the dam foundation allows for the verification of the input records applied at the model base to simulate the seismic event. The numerical model response showed generally good agreement with the experimental values, namely in terms of the peak values at various points along the crest.  
The present study shows the model's ability to reproduce the effects of an earthquake on the dam, even if only a low-intensity event has been recorded so far. The model is also intended to analyze the dam's response to the larger earthquakes considered in the design. In that case, the vertical contraction joints may separate, the dam-water interface will undergo larger movements, and slip may possibly take place at the foundation joint, thus taking full advantage of the nonlinear capabilities of the code. The mechanical model employed to simulate the dam-reservoir interaction is certainly a simplified one. For a high-intensity earthquake, further research is essential to assess its validity and evaluate the need for more elaborate constitutive relations to describe the behavior of the water elements and the dam-water interface. While arch dams under seismic action have drawn the most attention from researchers, the same approach may be extended to other types of concrete dams with rock mass foundations, such as gravity or buttress dams.  
Conceptualization, J.P.G. and J.V.L.; methodology, J.P.G. and J.V.L.; investigation, J.P.G.; writing--original draft preparation, J.P.G.; writing--review and editing, J.V.L. All authors have read and agreed to the published version of the manuscript.  
The support of the Portuguese National Laboratory for Civil Engineering (LNEC), through the research project SSDAM--Seismic safety assessment of concrete and masonry dams (0402/1102/24146).  
Data Availability Statement: Data is unavailable due to privacy restrictions.  
The authors would like to acknowledge Movhera/ENGIE for allowing us to present some of the results of the study and monitoring of the dynamic behavior.  
The authors declare no conflicts of interest.