Seismic and Structural Health Monitoring of Cahora Bassa Dam

This paper focuses on presenting a complete study on the dynamic behavior of Cahora Bassa dam (Mozambique), a 170 m high double curvature arch dam which has been under continuous vibrations monitoring since 2010. The installed Seismic and Structural Health Monitoring system was designed to continuously record acceleration time series in several locations in the dam body (crest gallery) and near the dam-rock interface, under ambient/operational vibrations and during seismic events, using uniaxial and triaxial accelerometers. The system was complemented with the development of software for automatic modal identification and automatic detection of seismic vibrations. The numerical simulations are carried out using a 3D finite element program, based on a solid-fluid coupled formulation to simulate the dam-reservoir-foundation system, considering dam-water dynamic interaction and propagation of pressure waves throughout the reservoir. The main experimental outputs are presented and compared with results from 3D finite element analysis, including the evolution of identified natural frequencies over time, vibration mode shapes, and the seismic response in accelerations. Finally the non-linear seismic behavior of Cahora Bassa dam is studied for an input accelerogram with a 0.6 g peak acceleration, considering the joints movements and a damage model for concrete.