The technology enables engineers, project managers and other stakeholders to capture near real-time data and be notified instantly if movement occurs outside of tolerance parameters.
The safety and efficiency gains of these wireless platforms such as Senceive, distributed locally in Australia, New Zealand and Indonesia by Aptella, are significant. When compared with traditional monitoring methods that utilise optical total stations, wireless solutions offer greater flexibility and options to scale to even the largest of projects. The small nodes and sensors can be mounted to any surface and have a 10 to 15-year battery life, making them ideal for large projects and hazardous or inaccessible landscapes as they require less maintenance that traditional methods.
Senceive solutions combine three key elements: sensor nodes placed on or nearby areas to be monitored for movement; a solar-powered cellular communication gateway to collate data from the nodes and transmit to cloud-based servers; and lastly an online portal for customers to manage and analyse the data.
For high risk, remote or hard to access areas, there is also an option to integrate cameras with the monitoring platform to give users eyes on the scene when movement is detected. With an instant visual of the scenario, in addition to movement data, the platform helps stakeholders differentiate between a false alarm or something more serious and respond appropriately and efficiently.
In New Zealand, Senceive technology was deployed on the North Island Main Truck Route to monitor 160kilometres of track and three existing rail overbridges.
The setup included 82 tilt sensors installed on the rail tracks and a further 10 fitted to monitor the three overbridges. All 82 track sensors were installed by a team of three surveyors in approximately five hours, significantly faster than the time it would have taken to install total stations and optical targets to the rail.
Three-quarters of the monitored section of track was fitted with timber sleepers, many of which were degraded and needed spot replacements during nightshifts as the project progressed. An advantage of the Senceive sensors was that they could be quickly detached from the old sleeper and reinstalled onto the replacement in time for rail services to resume during the day.
Track corrugation on the remaining quarter of the monitored track, where Senceive nodes were fitted to concrete sleepers, required technical assistance from the Aptella team to find a solution.
The corrugation caused the nodes to detect irrelevant movement and vibration, so a scale factor was calculated to dampen the x-axis values that were being reported and achieve accurate tilt measurements.
Upon completion of the monitoring project, the nodes were unclipped from their mounts and available for redeployment on the next project.
New York City was severely affected by Hurricane Sandy in 2012. Considered the fourth most expensive storm in U.S. history, the storm damaged around 100,000 homes and businesses and the economic losses were estimated at around $19 billion for NYC alone.
The city’s infrastructure is still recovering, including tunnels and bridges which were affected by substantial flooding.
The NYCTA Rail Bridge in Jamaica Bay, NY is an elevated commuter subway which serves MTA line A customers and provides a link between the communities of the Rockaway Peninsula and Brooklyn and Queens. Works were planned to replace ageing pier fenders, with monitoring required to ensure stability during the replacement process.
A conventional optical based monitoring method was originally specified to monitor both track and pier deflection, but this method was determined to be unfeasible. The closest location for a stable reference point was over 2,000 linear feet from the bridge, precluding traditional survey methods such as robotic survey which relies on line-of-sight and availability of backsights (or reference points). Also, these types of systems need repeated maintenance which would have been complicated due to access issues.
The Big Apple Group NY (Big Apple), which specialises in construction quality assurance and control, proposed an alternative approach using Senceive wireless monitoring technology.
Site access and installation was challenging, with track outages not possible, and only short access windows available in between trains. The discreet monitoring system from Senceive including sensors and two data communication gateways were quickly installed within available access windows, without having to deal with bulky equipment and external power systems.
A total of 56 tilt sensors were installed every 20 feet along the track to measure changes in twist and crosslevel displacements. A further 10 triaxial tilt sensors and 20 optical displacement sensors were installed on five of the piers to measure pier rotation and displacement. The two cellular gateways with internal batteries and small 20-watt solar panels were installed on opposite ends of the bridge for continuous data collection.
The use of Senceive’s wireless monitoring technology helped the construction team keep the bridge open throughout the upgrade work by providing insight into the structural stability of the tracks and piers. It helped engineers and other stakeholders proceed with confidence that they will be immediately alerted of any concerning movements. With long-life batteries and very low power consumption, this type of system can be re-used on further projects.
The value of wireless monitoring was demonstrated at Barnehurst on Network Rail’s Bexleyheath line in 2019. Around 200 Senceive triaxial tilt sensors and seven cellular cameras were installed on the slope above the track. In the early hours of Monday 11th February some of the nodes detected slow and gradual ground movement.
The system, now known as InfraGuardTM, automatically requested further data samples from nearby nodes to see if the initial small movements were widespread. It also “told” the gateway to stay open in order to transmit data and minimise any lag in decision making. These smart characteristics combined to provide a picture of the situation at any point in time. With alerts and alarms from sensors and images from the cameras being automatically sent to the route engineers as trigger points were breached, it provided an early indication of the potential for failure. The embankment collapsed a few hours later, it left a tree and debris on the track, but everyone was ready and the line was closed to traffic. Repairs were completed and the line was re-opened a week later.
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