Seismic and Structural Health Monitoring of Cabril dam. Software development for informed management

Abstract

Nowadays, the management and safety control of large dams is generally based on automatic monitoring, including the socalled seismic and structural health monitoring systems (SSHM), using the latest technology for automatic data measurement, acquisition and transmission. These systems should include software for automatic management and analysis of continuous monitoring data and software for numerical simulation of the dam dynamic behavior using 3D finite element models. This software should be designed to provide useful and reliable information to meet the needs and expectations of stakeholders, and to support the studies of researchers and engineers responsible for structural health monitoring. This paper is focused on the experience gathered from the SSHM system of Cabril dam, a 132 m high-arch dam, in Portugal, that has been under continuous dynamic monitoring since 2008. The importance of the software specifically developed for automatic modal identification, automatic detection of seismic vibrations (distinct from vibrations due to the operation of discharge gates and power groups), and automatic comparison between experimental data and computed results from a reference finite element model of the dam-reservoir-foundation system, is highlighted. This software includes: (1) the generation of graphics with the evolution of the identified natural frequencies over time and the comparison with calculated frequencies using different hypothesis for concrete damage evolution; and (2) a service to automatically send emails summarizing key dynamic monitoring results to stakeholders to provide the necessary support for informed management and engineering decision making. The main results from SSHM of Cabril dam are presented, namely regarding the evolution of modal parameter over time, considering the influence of water level variations, and the measured response during an earthquake event.