Abstract
Bridge Monitoring is a critical application to ensure safety for people who cross. A bridge is in fact subject not only to excavations or soil handling provided by human activity, but also to water action(s) around pillars. One of the main problems we had to face to develop this system was the presence of many nodes of measure with different measure point each; in case of wired systems, this involves the presence of many cables running aside the bridge. In this case we have use different smart sensors like accelerometers, temperature sensors and inclinometers, all connected to our wireless interface. NI-203 with SigFox radio is a low power wireless interface that allows long time battery operation and smart interaction among sensors, devices, cloud portal.
Purpose
Next Industries is an Italian data acquisition systems developer and manufacturer, whose products deals also with structural monitoring application. The Company is young, born in 2014, but it has already had experience in geotechnical applications; so when it was requested to deal with the monitoring system of a bridge, it has accepted the challenge, strong with its skilled staff and the most modern technologies now on the market.
Bridge Monitoring is a critical application to ensure safety for people who cross. A bridge is in fact subject not only to excavations or soil handling provided by human activity, but also to water action(s) around pillars.
A correct planning is the basis for a successfull bridge monitoring, as primary function of data acquisition is to ensure structure longevity, safety as well as timely focused intervention in case of damage. First of all, we had to decide which devices best fitted with the application and we found some sensor types:
- Accelerometer, used to monitor vibrations
- Linear Potentiometer, used to monitor expansion joint(s) position and movement
- Temperature sensors
- Inclinometers, used to monitor grade and tilt
Strain gauge is also a useful tool, but we decided not to use it, because it needs to be embedded in concrete to work properly and to monitor the curing process, so it needs to be placed during construction.
Then, we had to face the problem of many nodes of measure with different measure point each; in case of wired systems, this involves the presence of many cables running aside the bridge with the increases risk of fault possibility and of noise introduction – thus degrading the sensor signal. A single datalogger solution as concentration point is deprecated.
In order to propose a good and accured monitoring solutions, we had to keep clear in mind the critical parameters for the whole monitoring system (sensors and interface);
- Precision (consistency), accuracy (correctness), resolution and absence of drift
- Durability, low power consumption for long lasting unattended recordings
- Ease of readings, for fast data interpretation and presentation
Next Industries is the second Italian Company with a Sigfox-ready device; thanks to the union between Next’s and Sigfox’s technologies it is possible to build up wireless networks with “intelligent” devices always on and small amounts of data sending. Exactly what we needed to complete successfully our work.
NI-203 with SigFox radio is a low power wireless interface that allows long time battery operation and smart interaction among sensors, devices, cloud portal. Next Industries has provided for this customer 3-channels smart sensors which were setted up to send 3 acquisitions through Sigfox connection every 2 hours and which have allowed an accurate monitoring of the bridge.
A NI-203 device was placed in every measure node, in order to monitor every joint, pillar and truss; all these recorded data have been stored and shown through Next Industries’ IoT Cloud Web Portal, which also enables mail alarms and data analisys together with real time control of field devices. One of the most appreciated features of this Portal is the possibility to create different dashboards and to customize them through widgets like: Gauge, Gauges combination, Inclinometers, Line Charts, Histograms, Tables, Maps (to geolocalize sensor/daq system), Images (for example, a picture of the bridge with sensor’s reading overlay where each sensor position is showed). Thanks to the use of NI-203 SigFox, the following results have been achieved;
- Use of Smart Sensors, “intelligent” devices always on and with wireless connection
- Short, ordered cables
- Unexpensive radio subscription
- No radio infrastructure to be built, with better landscape impact and costs reduction
- Cloud/Personal server capabilities for easy data reading
- Long lasting batteries
- Wide choice of compatible sensors (4..20mA, Ratiometric, Vibrating Wire, 0-10V, NTC, TC, RS485 Modbus) that, becoming SMART, enable more accurate and automated collection of environmental data with less erroneous noise amongst the recorded information
- High resolution, accuracy and precision for more reliable measures