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Using SCADA systems To Monitor Fixed Bridges and Drawbridges

By Ziad Alezabi

January 30, 2024

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Using SCADA systems To Monitor Fixed Bridges and Drawbridges

Bridges are an important invention that has helped to transport goods and people across water or gaps in the land. It has helped us overcome obstacles (literally). However, bridges are subject to many situations such as traffic loads and environmentals.

As a result, monitoring bridges is an indispensable precaution. Monitoring your bridge will allow you to constantly maintain it and tend to issues before they turn into something bigger.

Using RTUs to Monitor Your Bridge

To monitor your bridge effectively, you will have sensors in place that are outlined later in this article. These sensors need to feed their information to a device called a Remote Telemetry Unit (RTU). RTUs can take discrete and analog inputs which most sensors use.

Here is a list of a key function in an RTU:

  • Data collection: RTUs will collect data from your sensors that monitor your bridge.
  • Data processing: For example, if a wind speed sensor (aka an anemometer) sends a certain signal between 0.1-5 mA, your RTU will translate that amp measurement into useful information about the present wind speed before it communicates that data elsewhere.
  • Central communication: RTUs enable you to link to bi-directional communication. This can be achieved by connecting an RTU with a master alarm monitoring station. While not common, you can also link two RTUs together using Ethernet, serial, radio frequency, cellular, etc.
  • Alarm Handling: This is when an alarm fires in your bridge's SCADA (Supervisory Control and Data Acquisition) system. When such an event occurs, you will also want your RTU to send commands that deal with your alarms.

When shopping for an RTU, look for one that supports a 4-20 mA output range from your sensors. Most sensors in this field of monitoring output 0.1-5 mA. However, you want something that leaves room for unexpected events. Otherwise, you will not be getting accurate measurements or your RTU will be incompatible.

Monitor Your Bridge's Structural Integrity

The first thing that you will need to monitor is the integrity of your bridge's structure. This can also be referred to as SHM (Structural Health Monitoring). This would involve using sensors to monitor different factors such as:

SHM will show you if your bridge has accumulated any damage. Over time, wear and tear can make your bridge a liability which contains multiple structural weak points. This could compromise your bridge and the lives of the people who cross it.

You can measure the outlined factors with different types of sensors such as:

  • Strain Gauges: These gauges typically output analog signals proportional to the strain measured. To monitor them correctly, they need to be connected to an RTU through an analog input channel on the RTU itself. Once wired to the RTU, it would be converted from an analog signal to a digital value.
  • Load Cells: This type of sensor outputs analog signals that indicate the load they're measuring. They are treated similarly to Strain Gauges in how they connect to an RTU.
  • Fiber Optic Sensors: These sensors output digital or analog signals depending on how they're configured. If they output an analog signal, it would be treated the same as the strain gauge example above. If it is a digital signal, it would use a discrete input.

Once these sensors are inputted into an RTU analog or discrete channel, it is then processed and transmitted using protocols such as Modbus and DNP3.

Environmentals Monitoring

Environmentals such as wind and temperature affect your bridge. This is because of factors such as:

  • Thermal wear and tear: The bridge will expand during hot weather and contract in cold weather. This can cause fatigue in the structure itself. To monitor temperature, you could use a temperature sensor. It would be connected to an RTU discrete input channel.
  • Wind: Wind causes strain on a bridge, especially if it is a suspension bridge. You would use an anemometer (or wind speed sensor) to monitor the wind speed. If there are any unexpected spikes in the wind's speed, the RTU will send alerts for further investigation.
  • Vibration: Vibration is an important factor to monitor on a bridge. It can be caused by factors such as traffic loads or even natural events like earthquakes. To measure vibration, you would use an accelerometer sensor that outputs analog signals and is connected to an RTU's analog input.

Your bridge will be prone to outside weather year-round. This means that environmental monitoring should be implemented no matter what type of bridge you are monitoring. Not only is it crucial for fixed bridges (bridges with no moving parts), but it is just as important with drawbridges.

Monitoring Drawbridges

Remote monitoring and control of your drawbridge is a requirement. A bridge has many moving parts in it. This is because there are more moving parts, and therefore, there is more of a chance for something to break such as:

  • Movable spans: This is the main section of a drawbridge that raises and lowers when a draw bridge is open. This often uses a counterweight to balance out the movable span.
  • Lifting mechanisms: Such as gears, hydraulic cylinders/pistons, pulley systems, etc. are responsible for lowering and raising the movable span.
  • Locks: These hold the bridge in the closed position when there is no need for it to be open. If they fail, the movable span can move out of its intended position and damage both itself and other parts of the bridge.
  • Control systems: These systems are responsible for drawbridge operations in general. This would include things such as the timing of opening and closing, bridge position, and water level.
  • Safety Systems: Safety systems such as a bar that swings down and lights flashing to alert people not to cross a bridge, as well as audible alarms, are important for pedestrian safety. If they do not function well, human lives might be put in danger.

If you are unable to monitor and communicate with your bridge, you will not have control over it. Finding a good SCADA system manufacturer will help you install the correct configuration to remotely monitor and control your drawbridge.

How a load sensor would determine if a bridge is opened or closed

This can include position sensors to know whether a movable span is open or closed. This can be combined with load sensors for your counterweights and other pulling methods to monitor the load. Proximity sensors can also help you to know if a ship is approaching your bridge.

Finding The Right SCADA Systems Manufacturer

To reliably monitor your bridge, you would need a reliable SCADA manufacturer that can supply you with industry-tested equipment. To spot a good manufacturer, look for ones that provide:

  1. Great tech support that answers your concerns and problems promptly.
  2. In-depth documentation on their equipment.
  3. Site visits to understand how your existing system operates.
  4. Training seminars for your in-house maintenance and monitoring team.
  5. Customizability that prevents you from running into infrastructural limits and hampers your scalability.

Chances are, your bridge is either being monitored by a municipality or a military organization. This means that your scalability will help you future-proof your existing systems and tie them all together through Master Stations that allow you to have a centralized location to receive and annunciate all of the information you need.

Call DPS Today For Total Control And Visibility Over Your Bridge

DPS Telecom has been servicing major municipalities, transportation departments, and military bases since its inception. We offer you 40 years of expert technical support, as well as in-depth documentation and offered training.

We also pride ourselves on our ability to customize form factors to fit your specific needs. When a client does business with us, we want them to treat us like their own personal engineer.

If this sounds like something that you may be interested in further discussing, or if you perhaps have further questions that were not answered in this article, please feel free to reach out to me with any questions.

Even if we do not end up being the right fit for each other, I will still try my best to point you in the right direction.

Call today at 1-800-693-0351 or E-mail me at sales@dpstele.com

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Ziad Alezabi

Ziad Alezabi

Ziad Alezabi is a Application Documentarian at DPS Telecom. He reviews successful DPS client projects and reports on the best practices that you can use to successfully reach your own project goals.