Condition survey and evaluation of an early post-tensioned bridge verified after removal

Abstract

In southern Switzerland, a post-tensioned concrete bridge built in 1952 showed signs of improper grouting of the ducts and subsequent corrosion of the prestressing steels. That is why a monitoring system was installed to detect wire breaks based on acoustic emission analysis. The monitoring revealed a wire break about every 35 days, and the owner decided to prop the bridge by additional piers and to replace it. The demolition of the bridge was used to establish a detailed condition survey of both the concrete and the reinforcement, especially the tendons. Consequently, excellent data are available on the actual condition of the bridge prior to removal. This information was used to calculate the structural capacity of the bridge and possible failure scenarios depending on applied traffic loads and ongoing deterioration. This paper presents the results of these calculations, based on a general description of the structure and the history of past maintenance and evaluation activities.

Keywords::

• concrete structures
• corrosion
• demolition
• monitoring
• structural safety
• time dependence

Acknowledgements

This work is based on the results of a master thesis delivered by Stephan Fäh and supervised by Thomas Wolf. Financial support was provided by the bridge research initiative of the Swiss Federal Road Office (FEDRO) and the Canton of Graubünden. All these contributions are highly appreciated.

Notes

^1. Email: [email protected]