Statistical analysis and structural identification in concrete dam monitoring

Large dam monitoring systems are usually based on both boundary conditions (temperature, rainfall, water level, etc.) and structural responses (i.e. displacements, rotations, pore pressures, etc.). Statistical analysis tools are widely used to compare the current response of the dam to a whole string of recorded data, in order to highlight in a timely manner eventual unwanted behaviours. The main drawback of this approach is that the structural response quantities are related to the external loads using analytical functions, whose parameters do not have physical meaning. Another option is using the structural identification technique, based on finite element models of the structure, that can be usefully adopted to obtain an estimate of true physical parameters, such as the elastic Young modulus, an overall indicator of structural integrity.In this paper, some hollow buttress gravity dams, built in Italy some decades ago, have been considered. The horizontal upstream–downstream crest displacement with respect to the foundation of each buttress, generally recorded with an acceptable degree of accuracy by pendulum instruments, is mainly induced by variations of air temperature and reservoir water level. Eventual non-reversible effects, caused by the accumulation of permanent drifts due to concrete deterioration, can also be evidenced.Two different procedures have been compared: a statistical approach and a structural identification technique. Besides the additional advantages in terms of information about the structural integrity of the dams, the structural identification results provide also a higher degree of accuracy in predicting the future behaviour of the structure.