Remote moisture monitoring of timber bridges: a case study

Abstract

This paper reports on the remote moisture monitorin g of a timber traffic bridge in Switzerland. Timber has been a structural material for bridges for centuries, exploiting its high ratio of bending strength to we ight. Numerous examples throughout the world demonstrate the durability of timber; if designed and monitored adequately. But timber is biodegradable, and it is recommended for timber bridges that inspections are carried out at regular intervals; until recently, such inspections were carried out exclusively throu gh on-site visits. An automated remote monitoring system provides a more efficient way to enable a sound structural assessment with continuous records of almost any re quired parameter. This is of special interest to owners of bridges, who must ens ure the on-going safety of their structures. In the case study, a concept to experim entally gather relevant moisture data was developed, at different locations of the s tructure as well as different depths inside individual members; additionally, climate va riables are recorded and related to the moisture content measurements. A data record ing system was installed and all data is automatically and remotely transferred to a server. A web interface provides continuous information on the structure’s condition , and allows identifying gradual changes over a period of time. The presented case-s tudy provides valuable information on applications and limitations of remo te moisture measurement systems for timber bridges.