Non-destructive testing of a cable-stayed bridge in Lisbon

This paper discusses objectives, methodologies and results from a campaign of non-destructive investigations per- formed on a cable-stayed bridge in Lisbon (Portugal). Among the investigations held, the campaign encompassed dynamic testing of the stay cables, to identify their natural vibration frequencies and to estimate the tension force. A frequency-domain output-only approach was carried out to identify the natural frequencies of the cables and, subsequently, on the basis of the flat taut string model, the cables tension force was estimated. In an advantageous and cost-effective way, vibration tests were carried out without the inter- ruption of the vehicular traffic. Results of the testing campaign were finally incorporated in the bridge condition assessment and used to provide both short- and long-term maintenance prescriptions.