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Monitoring bridge weather conditions

Supplier: Campbell Scientific Australia By: Steve Bailey
18 March, 2009

Bridge monitoring plays an important role in managing road and rail infrastructure, especially under extreme weather conditions.

Recently our technical team was asked to assist in designing a wind monitoring system suitable for rail bridge monitoring.

The site had sustained failure of a bridge pier during an extreme rainfall event. Due to temporary repairs made to the bridge, traffic across the bridge was not permitted under certain wind conditions.

Campbell Scientific Australia designed a wind monitoring system that accurately gauged the current wind conditions on-site, communicating with an existing telemetry system networked to the locomotives - alerting drivers to unsafe conditions when necessary.

Based on the site locations, the RM Young Wind Monitor was selected as the wind sensor due to its propeller style configuration and practical maintenance requirements. In order to provide the interface between the sensor and the SCADA communications network, the CR800 Campbell Scientific data logger, with Modbus protocol support was installed.

The data loggers were configured to measure both wind direction and wind speed. Once the nominated wind speed threshold is exceeded the data logger flags an alarm which is passed on to alert operators in the vicinity. All traffic across the rail bridge is halted until conditions return to a safer level. Access to this information in advance allows the rail operators to minimise down time and disruption to travel schedules.

The data logger system distributes data to a centralised depot and onwards through to the locomotive drivers, using the Modbus protocol over a radio network. The long range telemetry equipment at each of the sites adds a requirement for a significant power supply.

Due to the remote location and a lack of existing power infrastructure at the site, the only suitable option for powering the system was solar power. The high consumption of power led to the design of an impressive solar panel system. Each monitoring site was equipped with 190W of solar panels and batteries to provide a capacity of around 200 Amp hours.

The installation of the monitoring sites allow for more accurate, real time, reliable measurements that can be easily distributed to the relevant parts of the rail network and has led to safer driving conditions. 

Alternative sampling techniques with handheld wind instruments by locomotive drivers were also proposed. Handheld measurements would have caused inefficiency and provided justification to installing a permanent site system. The new system allows the client to save on fuel costs of stopping and starting locomotives unnecessarily and allows them to maintain a better management of their travel schedules, without sacrificing critical safety aspects.