Monitoring the Structural Health of the Rion-Antirion Bridge Using the LabVIEW Real-Time Module

 Read in  |   Print

"Because of the large number of input channels and the adverse operational environment, we used the NI PXI/SCXI chassis and LabVIEW Real-Time to perform the task. The resulting system houses and performs signal conditioning, data acquisition and processing, program control, and data storage and transmission with a high degree of reliability."

- Bernard Basile, Advitam, Inc.

The Challenge:
Developing a structural monitoring system to measure and define the behavior of the Rion-Antirion Bridge during normal operation, strong winds, and earthquakes.

The Solution:
Using a combination of four PXI/SCXI chassis linked with the NI LabVIEW Real-Time Module to incorporate the conditioning, acquisition, processing, control, storage, and sharing of measurements.

Author(s):
Bernard Basile - Advitam, Inc.

At Advitam, a subsidiary of VINCI Construction, we develop asset management, civil engineering, and structural monitoring services with a focus on occurrence detection and risk analysis methods. We designed and implemented a structural monitoring system for the Rion-Antirion Bridge, which spans the Corinth Strait and links Peloponnese in southern Greece to the Greek mainland. At 2,883 m (9,458 ft) long, the bridge is frequently exposed to heavy lateral wind forces. It is also located in an area of high seismic activity with each end on different tectonic plates, resulting in a relative movement of almost 2 cm per year.

We designed a monitoring system that could operate in this harsh environment while providing a reliable, continuous data stream to record measurements and events that can affect the bridge’s structural integrity.

Implementation

We began the project three years before the bridge opened. We began with a risk analysis to define which elements of the bridge were critical and in need of monitoring, then we identified which sensors were required and where we could place them on the bridge, including the following:

  • 3D accelerometers on the deck, pylons, stay cables, and on the ground to characterize wind movements and seismic tremors
  • Strain gages and load cells on the stay cables and their gussets
  • Displacement sensors on the expansion joints to measure the thermal expansion of the deck
  • Water-level sensors on the pylon bases to detect infiltration
  • Temperature sensors in the deck to detect freezing conditions
  • Linear variable differential transducer (LVDT) sensors on the stay cables to measure movement
  • Load cells on the restrainers for recalibration in the event of an earthquake
  • Two weather stations to measure wind intensity, direction, air temperature, and relative humidity

With the addition of a power supply and a lightning conductor control, the required system needed a total of 372 measurement channels. It also had to be capable of acquisition and simultaneous dynamic processing of multiple signals for permanent monitoring while presenting a user-friendly interface and well-designed output reports. Because of the large number of input channels and the adverse operational environment, we used the NI PXI/SCXI chassis and LabVIEW Real-Time. The resulting system houses and performs signal conditioning, data acquisition and processing, program control, and data storage and transmission with a high degree of reliability. Each of the bridge’s four pylons is equipped with an NI PXI-1010 chassis with eight PXI slots and four SCXI slots, an NI PXI-8175 controller, SCXI signal conditioning modules linked to the sensors, an NI PXI-6040E module to acquire the data, and an NI PXI-8423/2 module to integrate the data from the weather station in RS485. The LabVIEW Real-Time Module runs on each PXI controller to ensure the acquisition and scaling of the measurements and compare them to fixed or variable thresholds to trigger alarms if necessary. The four systems are linked through a fiber-optic Ethernet network to a control PC installed in the operations building.

Each PXI device continuously acquires data and creates history files that are regularly sent to the control PC. When a threshold goes past its limit, a selective acquisition unit with real-time recording starts on each chassis. A pretrigger mechanism is also incorporated to identify and record the events that occurred immediately before the alarm.

The interface on the control PC offers different windows to the user, including a synoptic view of the bridge that shows measurement points. Those points are typically displayed in green, but change to red when a threshold goes past its particular limit. The interface also includes automatic and expert function analysis. We can remotely access the computer via a modem to access information or redefine monitoring parameters.

Successful Development of a Structural Monitoring System

Our system is fully functional and the customer is extremely satisfied. It has already inspired a similar monitoring system for the Millau Viaduct in France. We will continue to optimize the system, and we intend to offer customized versions for other monitoring systems in the near future.

Author Information:
Bernard Basile
Advitam, Inc.
France
Tel: +33 1 01 46 01 85 00
bbasile@advitam-group.com

Bookmark and Share


Explore the NI Developer Community

Discover and collaborate on the latest example code and tutorials with a worldwide community of engineers and scientists.

‌Check‌ out‌ the‌ NI‌ Community


Who is National Instruments?

National Instruments provides a graphical system design platform for test, control, and embedded design applications that is transforming the way engineers and scientists design, prototype, and deploy systems.

‌Learn‌ more‌ about‌ NI