Abstract
Bridge Monitoring is a crucial application for ensuring the safety of people. Bridges are vulnerable to various factors such as human activity, water action, and soil handling, which can compromise their integrity. Developing a reliable bridge monitoring system posed a significant challenge, particularly due to the presence of multiple measurement nodes, each with its specific points of measurement. Wired systems entail the installation of numerous cables along the bridge, further complicating the process.
To address these challenges, we adopted advanced smart sensors, including accelerometers, temperature sensors, and inclinometers. These innovative sensors are seamlessly integrated into our wireless interface, providing a comprehensive and efficient solution. Our wireless interface utilizes the NI400 with SigFox radio, which boasts low-power consumption, allowing prolonged battery operation. This wireless interface facilitates intelligent communication and interaction among sensors, devices, and cloud portals.
By harnessing the power of smart sensors and wireless interfaces, our bridge monitoring system empowers engineers and authorities to conduct effective structural health monitoring of bridges. With timely and accurate data, potential safety risks can be identified and addressed promptly, ensuring the continuous safety of bridges and the people who rely on them.
Purpose
Next Industries is an Italian data acquisition systems developer and manufacturer whose products deals also with structural monitoring applications. 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 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 the safety of people who cross the bridge. 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.
Correct planning is the basis for successful bridge monitoring, as the primary function of data acquisition is to ensure structure longevity and safety as well as timely focused intervention in case of damage. First of all, we had to decide which devices best fitted 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
The 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 points each; in the case of wired systems, this involves the presence of many cables running aside the bridge with the increased risk of fault possibility and noise introduction – thus degrading the sensor signal. A single data logger solution as a concentration point is deprecated.
To propose good and accurate 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 our work successfully.
NI-400 with SigFox radio is a low-power wireless interface that allows long-term battery operation and smart interaction among sensors, devices, and cloud portals. Next Industries has provided for this customer 3-channels smart sensors which were set up to send 3 acquisitions through Sigfox connection every 2 hours and which have allowed an accurate monitoring of the bridge.
A NI400 device was placed in every measure node, 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 analysis 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 Gauges, Gauges combinations, 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-400 SigFox, the following results have been achieved;
- Use of Smart Sensors, “intelligent” devices always on and with wireless connection
- Short, ordered cables
- Inexpensive radio subscription
- No radio infrastructure to be built, with better landscape impact and cost 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