Maximising safety, minimising maintenance costs
Structural Health Monitoring of QEII Bridge for Connect Plus Services (CPS)
The Queen Elizabeth II Bridge is one of Europe’s largest cable supported bridges and is managed by Connect Plus Services (CPS) as part of the M25 network for which they are responsible.
CPS were concerned that vibration occurring on parts of the bridge would result in structural fatigue and increased maintenance costs.
Verification and condition monitoring are essential aspects of maintenance and ensure that any service disruption, plus the cost of managing inevitable structural wear and tear, can be kept to an absolute minimum.
AIS were contracted to take overall responsibility for the project, including working with the consultants – COWI – to specify the system including the specialist sensors. AIS and COWI then worked together to tender for the supply and fitting of the sensors with AIS responsible for placing and managing the sub-contract – including the rope technicians who were responsible for installing sensors on the cable stays.
The specific role of AIS beyond managing the project was to develop a monitoring and logging system able to complete a simultaneous analysis of multiple bridge components using high speed sensors – such as accelerometers – and then triggering logging of the data according to different weather conditions which are also monitored.
We can then make reliable predictions about the amplitude of vibrations plus their future frequencies of occurrence. This predictive power can save significant amounts of actual value when one considers the costs of stay replacement or strengthening.
Technical Manager at COWI
- Using the company’s SFW software toolset – the same software used to develop a site SCADA system for the Dartford River Crossing – AIS developed a PC based application to acquire data from structural sensors at very high speeds and process it so that only the most relevant information is logged for analysis.
- Five aspects of bridge behaviour are continuously, intelligently monitored to understand the impact of weather and long-term usage on bridge performance. Samples are taken at 200Hz from accelerometers across the bridge and on cable stays, 25Hz reading of tilt meters on pylons and road deck, and 1Hz readings of temperature, wind speed, humidity & rainfall.
- Data is collected from several data acquisition sub-systems all linked via a high-speed fibre based TCP/IP network. Ultra-precise synchronisation of data across the sub-systems means that vibration and other bridge data can be viewed and analysed as a single data set – important for the structural engineers who use this data for structural analysis.
- AIS integrated the data logging with a web application, enabling authorised specialists to access and download data. The system provides the data required for the CPS structural specialists to accurately forecast maintenance and operational costs in the shortest possible timeframe and take ameliorative action.
AIS’ added value as control system integrators
- Operated as main contractors for the complete project and took overall responsibility for the deliverables;
- AIS developed SCADA toolset – SFW – which has enabled the creation of a high speed data acquisition and logging application;
- Close cooperation with the structural consultants – COWI – meant that the system was designed and built specifically to support the data analysis.