The structural auscultation and monitoring It allows monitoring the evolution of bridges, tunnels, buildings, slopes and other infrastructures through the periodic or continuous measurement of displacements and deformations.
When there is a stable reference point and direct visibility to the point to be controlled, the laser distance sensors These measurements can be taken without physical contact with the structure. This feature is especially useful in hard-to-reach places, over long distances, or in installations where it is not feasible to place a mechanical transducer between the two measurement points.
Laser sensors Dimetix They can be integrated into instrumentation, data acquisition, and monitoring systems to control displacements, arrows, convergences and structural movements during the construction, load testing or operation of an infrastructure.
What can be measured with a laser sensor during auscultation?
Laser distance measurement can be used at different points in a system structural monitoring. The application depends on the geometry, the working distance, the required precision, and the movement that is to be detected.
| Infrastructure | Magnitude or phenomenon | Laser sensor application |
|---|---|---|
| Bridges and viaducts | Deflection and deformation | Tracking the movement of the board relative to a stable reference |
| Bridges | Relative displacement | Control between piles, pylons, deck or other structural elements |
| Tunnels | Convergence | Variation in distance between points of a section |
| Tunnels | Geometric deformation | Tracking of vault, gables or relationship between track and wall |
| Stacks and pillars | Displacement or change in position | Monitoring of structural elements during construction or load changes |
| Slopes and hillsides | Surface movement | Tracking rocks, boulders, or landmarks |
| Structures during construction | Deformation under load | Control during construction, movement, lifting or load testing |
Monitoring of bridges and viaducts: deflection, deformation and displacements
In the inspection of bridges and viaducts It may be necessary to monitor the evolution of the deck's deflection, structural deformations, or relative displacements between different elements of the structure.
A laser sensor installed on a stable point can periodically or continuously measure the distance to a reference point located on the monitored element. The evolution of this distance allows for the detection of movements during construction, operation of the infrastructure, or under specific load conditions.
- Control of the arrow or board displacement.
- Measurement of movements between a pile, pylon and board.
- Monitoring of deformations during load tests.
- Control of structures during construction, displacement or lifting operations.
- Integration of laser measurement points within systems SHM (Structural Health Monitoring).
Dimetix has documented applications specifically for structural monitoring of bridges. In the expansion of the Huey P. Long Bridge over the Mississippi River, ten laser distance sensors were used to measure in real time the deformation of large sections of lattice during their transport, lifting and placement.
This type of application demonstrates one of the advantages of laser measurement: obtaining displacement information at a distance without the need to physically connect the two points to be monitored using a transducer.
Monitoring of piles, pillars and structural elements
During construction work it may also be necessary to check if a bridge pier, pillar, facade, or other structural element Its position changes as a result of excavations, nearby works, load changes, or ground movements.
Using one or more sensors, the evolution of the displacement can be tracked and each reading compared to an initial reference position. This type of instrumentation allows for the detection of small position variations without physical contact with the monitored structure.
In one such application, Dimetix laser sensors were used to monitor the evolution of pillars located under a bridge while construction work was being carried out in a nearby area.
When the project requires monitoring several quantities, laser measurement can be combined with inclinometers, LVDT sensors, extensometers, piezometers and data acquisition systems.
Tunnel inspection and convergence control
He convergence control in tunnels It allows analyzing the variation in distance between different points of a section to determine if movements or deformations are occurring during the construction or operation of the infrastructure.
A laser measuring system can perform this tracking automatically when there is a line of sight between the sensor and the target. By comparing successive readings with an initial reference, it is possible to identify geometric variations in the monitored section.
- Measurement of convergence between points of a section.
- Control of vault and gable deformations.
- Geometric monitoring during excavation or construction.
- Control of the distance between the track and the tunnel wall.
- Detection of movements associated with works carried out on or near the tunnel.
Dimetix has a documented application of automated monitoring of a railway tunnel, Developed to detect potential structural deformations during infrastructure work, the sensors performed periodic distance measurements that could be integrated into the monitoring system.
Using multiple measurement points, a geometric reference of the section can be obtained and its evolution studied. Depending on the application, laser measurement can complement total stations, inclinometers, extensometers, and other common monitoring equipment.
Monitoring of slopes, hillsides and rock movements
The instrumentation and monitoring of slopes It allows the detection of changes that may indicate ground movements, landslides, or loss of stability.
Laser sensors can be used when the movement to be monitored occurs on a surface visible from a stable measuring point. The sensor repeatedly measures the distance to the target, allowing its evolution over time to be analyzed.
Possible applications include tracking rocky blocks, slopes, embankments, landslides, areas at risk of landslides and other points where a stable measurement reference can be defined.
Dimetix documents applications in which its sensors are used to control rock formations located on railway infrastructure and also large blocks of rock whose movement downslope must be monitored.
It is important to differentiate this application from other geotechnical instrumentation techniques. A laser sensor allows for the measurement of primarily visible surface movements from the installation point. When it is necessary to study internal ground movements, inclination at different depths or water pressure, specific technologies such as geotechnical inclinometers, extensometers or piezometers must be used.
Advantages of laser measurement in structural monitoring
One of the main advantages of laser sensors over many conventional displacement transducers is that they perform the measurement without physical contact with the monitored element.
- Non-contact measurement.
- Possibility of working remotely.
- Install the sensor in a protected or accessible area.
- Automatic and continuous reading.
- Integration with PLCs, dataloggers, and acquisition systems.
- Possibility of working on a natural surface or on a reflective reference, depending on distance and model.
- Measuring points where it would be difficult to physically connect a displacement transducer.
Dimetrix DPE-10-500 sensor for long-range applications
One of the models that can be used in long-distance monitoring applications is the Dimetrix DPE-10-500. This sensor combines millimeter precision, high measurement speed, and a range of up to 500 meters when using a reflective sheet.
| Feature | Dimetrix DPE-10-500 |
|---|---|
| Typical accuracy 2σ | ±1 mm |
| Typical repeatability 2σ | ±0.3 mm |
| Range on natural surfaces | 0.05 at approximately 100 m |
| Range on reflective sheeting | approximately 0.5 to 500 m |
| Maximum measuring speed | 250 Hz |
| Maximum output speed | 1 kHz |
| Digital interfaces | RS-232, RS-422, RS-485, SSI and USB |
| Analog output | 0/4–20 mA |
| Operating temperature | -40 to +60 °C |
| Protection | IP65 |
In industrial systems, it is also possible to integrate sensor data with communication networks and control systems using the corresponding modules or interfaces. For example, integration with structural monitoring systems has been used in such projects. PROFINET to transmit the measurement to higher control and acquisition systems.
The choice of model should not be based solely on the maximum range. Other factors to consider include the area to be measured, the required accuracy, environmental conditions, read speed, installation geometry, and the available communication interface.
When should you use a laser sensor and when should you use another technology?
The laser sensor is especially suitable when there is direct line of sight, Mechanical contact must be avoided, and the reference point is located at a considerable distance. However, it does not necessarily replace other instruments used in auscultation.
| Need for measurement | Technology that may be suitable |
|---|---|
| Remote and contactless displacement | Laser distance sensor |
| Small displacements between two nearby points | LVDT, extensometer or displacement transducer |
| Tilt or rotation of a structure | Inclinometer or clinometer |
| Internal ground movements | Geotechnical inclinometer |
| Interstitial pressure or water level | Piezometer |
| multi-point geodetic control | Total station or GNSS system, depending on the application |
For this reason, in a project of structural auscultation and monitoring It is common to combine different technologies within the same measurement system.
Integration with acquisition and monitoring systems
Dimetix laser sensors have industrial interfaces that allow distance measurement to be incorporated into PLCs, data loggers, acquisition equipment, or monitoring software.
This allows historical data to be stored, trends to be represented, measurements to be compared with reference values, and alarms to be generated when a displacement exceeds the limits established for the project.
In permanent monitoring systems, the laser sensor can be part of an instrumentation network along with inclinometers, extensometers, LVDTs, environmental sensors, piezometers, and other measuring equipment.
Sensor selection for an auscultation project
To correctly define a measurement solution, it is necessary to know at least the working distance, expected displacement, required accuracy, target surface, environmental conditions, reading frequency, and data acquisition system.
GUEMISA can help select the most suitable Dimetix sensor and measurement technology based on the actual conditions of each installation.
If you are developing a project of bridge inspection, tunnel monitoring, convergence control, structure monitoring, or slope instrumentation, You can provide us with the application data to study the most appropriate measurement solution.