InquiryWhat are the bridge displacement monitoring devices?
Release time：
2025-07-30
Bridges, as core hubs of the transportation network, directly relate their structural safety to public safety and the economic lifeline. Displacement monitoring, as the core link of bridge health management
Bridges, as core hubs of the transportation network, directly relate their structural safety to public safety and the economic lifeline. Displacement monitoring, as the core link of bridge health management, provides scientific basis for assessing bridge conditions and formulating maintenance strategies by capturing deformation data of structures under the effects of load, temperature, geological activities, etc. With the integration of the Internet of Things, artificial intelligence, and high-precision sensing technology, bridge displacement monitoring equipment has formed a technical system covering all scenarios and dimensions.
1. Traditional displacement monitoring equipment: Continuous optimization of classic technology
1. Contact-type displacement meter: Accurate measurement of minute deformations
Contact-type displacement meters directly contact the measuring point through the mechanical structure, converting displacement into measurable physical quantities. The dial indicator, the thousandth indicator, and the deflection meter are the most commonly used mechanical instruments in bridge engineering. Their measuring range varies from 5 mm to dozens of centimeters, with a precision of up to the micrometer level. Such devices are suitable for measuring scenarios such as pier settlement, bearing sliding, and deflection of concrete beams, with the advantages of simple construction and low cost. For example, in bridge structure tests, the dial indicator is often used to monitor the relative displacement between components, while the deflection meter can measure the dynamic deformation of steel beams under vehicle load.
2. Total station: Accurate capture of three-dimensional coordinates
Total stations, as the "all-rounder" in bridge monitoring, integrate distance, angle, and elevation measurement, enabling the automatic acquisition and processing of three-dimensional coordinates. Its static angle measurement accuracy can reach ±0.5 seconds, with a distance measurement accuracy of 1 millimeter ±1ppm, making it suitable for scenarios such as bridge alignment monitoring and main tower deviation measurement. For example, in suspension bridge monitoring, total stations can regularly measure the coordinates of the main cable anchorage points to assess the stability of the anchorage system. Modern total stations also have automatic tracking capabilities, which can capture dynamic displacements in real time, providing data support for bridge vibration analysis.
3. Strain gauge: Classic scheme for large displacement measurement
The tension-type displacement gauge transmits the displacement of the measuring point through a taut steel wire, combined with a lever, friction wheel, or gear transmission mechanism to amplify the deformation, making it suitable for bridge construction inspection and long-term dynamic monitoring. Its typical applications include measuring the displacement of the beam end of large-span bridges and the settlement of the arch top of arch bridges, etc. For example, in the monitoring of cable-stayed bridges, the tension-type displacement gauge can be installed at the connection between the main beam and the tower to track the displacement changes of the cable anchor point in real time, providing a basis for cable tension adjustment.
ii. High-precision optical monitoring equipment: Breakthrough in non-contact measurement
1. Laser rangefinder: Remote monitoring with millimeter-level accuracy
Laser rangefinders achieve non-contact displacement measurement by emitting laser beams and measuring the reflection time. Their accuracy can reach ±0.1 millimeters, with an effective monitoring distance exceeding 500 meters, making them suitable for scenarios such as bridge mid-span deflection and pier inclination. For example, in the monitoring of continuous rigid frame bridges, laser rangefinders can be installed at the top of the bridge tower to assess the vertical deformation of the bridge by measuring the relative distance between the main beam and the tower top. However, laser rangefinders are sensitive to rainy and foggy weather, and their data reliability needs to be enhanced by combining environmental compensation algorithms.
2. Visual Displacement Monitor: AI-powered intelligent sensing
Visual displacement monitoring instruments utilize computer vision technology to capture and analyze target displacement at the measuring points through cameras, achieving non-contact, multi-point synchronous monitoring. Its advantages include no need for wiring or sensor installation, where only the target needs to be painted or a retroreflective plate needs to be installed at the measuring point, reducing costs by more than 30%. For example, in the monitoring of a cross-river bridge, the visual displacement monitoring instrument can be installed at the top of the bridge pier, covering all the measuring points of the bridge through a zoom lens, and outputting real-time data of horizontal displacement, vertical settlement, and tilt angle. Combined with deep learning algorithms, the system can automatically identify structural damages such as cracks and corrosion, achieving "monitoring-diagnosis" integration.
Three, Satellite navigation and optical fiber sensing: wide area coverage innovation.
1. GNSS displacement monitoring station: Real-time guardian of global positioning
GNSS (Global Navigation Satellite System) displacement monitoring stations achieve real-time tracking of bridge three-dimensional coordinates at the millimeter level by receiving satellite signals. Its core advantages include wide coverage and high automation, making it suitable for long-term monitoring of large bridges such as those crossing canyons and seas. For example, in the monitoring of the Hangzhou Bay Cross-Sea Bridge, the GNSS receiver can simultaneously track the transverse displacement and longitudinal settlement of the southbound navigation bridge, and combined with meteorological station data, establish a displacement-environment correlation model to provide decision support for traffic control during typhoons.
2. Fiber Optic Grating Sensor: Embedded monitoring with anti-interference capability
Fiber Bragg grating sensors reflect structural strain and displacement by measuring the wavelength change of the grating, and they have the characteristics of anti-electromagnetic interference and long service life. They can be embedded in concrete to monitor the extension of fine cracks, or pasted on the surface of steel beams to capture dynamic deformation. For example, in the monitoring of the main cable of a suspension bridge, fiber Bragg grating sensors can be arranged along the cable to sense the strain distribution of the cable in real time, providing data support for cable tension adjustment and fatigue assessment.
IV. Intelligent Integrated Monitoring System: Future Directions of Multi-Technology Convergence
1. Hybrid monitoring scheme: complementary precision sensing
Modern bridge monitoring often adopts a hybrid scheme of "GNSS + fiber + vision", combining the advantages of different technologies to achieve full-scene coverage. For example, in the monitoring of a certain cable-stayed bridge, dual-axis tilt sensors and GNSS receivers are installed at the top of the bridge tower, fiber grating sensors and laser rangefinders are set in the middle of the main girder, and strain-type settlement meters are embedded at the bridge abutment, and the environmental noise is eliminated through data fusion algorithm to generate displacement trend curve, and the alarm is automatically triggered when the displacement exceeds the threshold.
2. Edge computing and digital twin: Support for intelligent decision-making
The introduction of edge computing gateways and AI algorithms enables monitoring devices to have local data processing capabilities, which can eliminate abnormal values in real time and predict the service life of structures. For example, in the BIM+GIS integrated analysis platform, the three-dimensional digital model of bridges can dynamically simulate displacement data, combined with historical load information, to evaluate the remaining bearing capacity of structures and provide optimization suggestions for reinforcement design.
5. Key Considerations for Equipment Selection and Deployment
1. Sensor deployment strategy
Displacement sensors should be preferentially arranged at key load-bearing points such as the top of the bridge pier and the end of the cantilever beam, avoiding areas where vehicles can directly crush. For example, in the monitoring of interchanges on soft soil foundations, uneven settlement of the bridge pier needs to be monitored as a priority, and reinforcement procedures should be initiated if the cumulative settlement exceeds 20 millimeters.
2. Power Supply and Communication Scheme
It is recommended to use solar panels and batteries as dual backups for power supply to ensure continuous operation for more than 30 days during the rainy season. Data transmission can be combined with 4G, LoRa, and Beidou short message to adapt to remote areas without public network coverage. For example, in the monitoring of bridge across canyons, Beidou ground augmentation micro基站在 positioning accuracy can be improved to the millimeter level, ensuring the stability of data transmission.
3. Environmental adaptability design
The equipment shall have an IP67 protection level, a lightning protection level that meets the IEC61643 standard, and a grounding resistance of less than 4 ohms. For example, in areas with severe acid rain corrosion, the sensor housing should be made of 316L stainless steel to extend the service life.
The technological evolution of bridge displacement monitoring equipment embodies the transition from single-parameter measurement to multi-dimensional sensing, and from manual patrol to intelligent early warning. With the deep integration of AI and the Internet of Things, future monitoring systems will possess self-awareness, self-diagnosis, and self-repair capabilities, providing stronger technical support for the full-life cycle health management of bridges.
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