Vibration Analysis for Model Calibration and Structural Condition Assessment of Cahora Bassa Dam Considering the Concrete Swelling Effects

This paper focuses on vibration-based analysis for model calibration and structural condition assessment of large concrete dams. The case study is the 170 m-high Cahora Bassa arch dam, Mozambique. In operation for almost 50 years, the dam presents deterioration signs due to concrete swelling, and in 2010 it was instrumented with a continuous dynamic monitoring system. In this work, the vibrations measured under ambient/operational conditions for more than a decade are analyzed in order to estimate the modal parameters of the dam, which are then used to calibrate and validate a new finite element model of the Cahora Bassa dam-reservoir-foundation system. After that, finite element analyses are performed to simulate the dynamic behavior of the dam for future years, considering a scenario of progressive damage due to concrete swelling. The presented results show that the dynamic performance of Cahora Bassa dam in normal operating conditions is not being affected by the existing concrete swelling phenomenon, and that vibration-based analysis can provide valuable data for detecting structural changes in concrete dams due to progressive deterioration.