Condition assessment of bridges using monitoring data

In the last years, significant interest has been vested in the possibility of using Structural health monitoring (SHM) as a standardized tool in bridge engineering. Structural Health Monitoring is an emerging field in engineering that gathers together several techniques such as structural dynamics, materials, signal processing, or microelectronics. Sensors, data, and simulation tools come together under the umbrella of SHM to offer - at every moment during the life of a structure - a diagnosis of its health and prognosis of its remaining life. This thesis has been developed within the group of Structural dynamics and monitoring at ETH Zurich, under the supervision of Prof.Dr. Eleni Chatzi. The aim of this thesis has been to try to assess the condition of a bridge, used as case study, in order to detect changes in modal parameters and correlate them with possible types of damage, especially the ones caused by environmental (temperature) and operational (traffic) variability of modal parameters. Furthermore, a performance indicator of the health of a structure, such as fatigue, has been studied in this work in order to relate possible damage accumulation to the environmental and operational condition. For the purposes of these studies, a major bridge infrastructure in Switzerland has been analysed. Additional knowledge and information were essential though, before the intended calculations could be performed. This study contributes to the development of an analysis process for SHM-based condition assessment for an existing structure, thereby defining further methodologies and strategies for maintenance and repair of bridges. In addition, it provides relevant information for design purposes about the influence of seasonal behaviour of action effects and traffic loads on the stiffness and different fatigue damage throughout a reference period for the long span bridge under investigation, pointing the way to implementing such methods for bridge infrastructure.