Box-type roadbed structure health monitoring method

Abstract

The invention relates to the technical field of box-type roadbed construction, in particular to a health monitoring method for a box-type roadbed structure. The method comprises static characteristic monitoring and train dynamic response characteristic monitoring. The static characteristic monitoring comprises displacement deformation monitoring of the box body and long-term temperature and stress monitoring of the box body; the train dynamic response characteristic monitoring comprises excitation monitoring and train dynamic response monitoring. According to the invention, through integration of static and dynamic multi-dimensional monitoring and accurate layout of key points, accurate perception and early warning of the health state of the whole life cycle of the box-type roadbed structure from the construction period to the operation period are realized, and the safety and the operation and maintenance intelligent level of high-speed railway infrastructures are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of box-type roadbed construction technology, and more specifically, to a method for monitoring the structural health of box-type roadbeds. Background Technology

[0002] With the rapid expansion and extension of my country's high-speed railway network, railway lines inevitably need to traverse challenging geological sections such as soft soil, deep silt, and high-intensity earthquake zones. Traditional embankment subgrades face difficulties in settlement control, poor stability, and a large workload for subsequent maintenance in these sections. To overcome these challenges, a new type of box-type subgrade structure has emerged. This structure uses a large cast-in-place or precast reinforced concrete box frame, which, through its strong overall rigidity and hollow characteristics, can effectively distribute loads, reduce uneven settlement, and provide solid support for the line.

[0003] However, as a load-bearing structure, the long-term safety and stability of the box girder are crucial. During long-term operation, it will continuously bear the weight of the superstructure, the dynamic load of repeated passing trains, and the multiple effects of the external environment (such as temperature, earthquakes, and geological changes). These factors may lead to cumulative settlement, concrete cracking, stress redistribution, and even fatigue damage, directly threatening the smooth and safe operation of high-speed trains. Currently, monitoring of conventional roadbeds is mostly focused on surface displacement or single index measurement, lacking systematic and comprehensive monitoring methods for large spatial thin-walled structures like box-type roadbeds. Traditional monitoring methods are insufficient to fully capture their static characteristics (such as overall deformation, long-term stress evolution, and temperature field distribution) and train dynamic response characteristics (such as dynamic response and vibration transmission laws under train load excitation). This lack of monitoring data makes it difficult for operation and maintenance departments to accurately assess the true health status of the structure, predict its long-term performance evolution, and promptly detect potential defects. Summary of the Invention

[0004] This invention provides a monitoring system for the dynamic response characteristics of box-type roadbeds, which can overcome some or all the defects of the prior art.

[0005] According to a method for health monitoring of a box-type roadbed structure, the present invention includes static characteristic monitoring and train dynamic response characteristic monitoring; static characteristic monitoring includes displacement deformation monitoring of the box and long-term temperature and stress monitoring of the box; train dynamic response characteristic monitoring includes vibration monitoring and train dynamic response monitoring.

[0006] During displacement and deformation monitoring, after the box-type roadbed is poured, displacement sensors and deflection deformation sensors are installed on the top, sides and bottom of the box-type roadbed respectively. The settlement, horizontal displacement and top plate deflection data of the box-type roadbed are monitored through the displacement sensors and deflection deformation sensors.

[0007] For long-term temperature and stress monitoring of the enclosure, each section of the enclosure is monitored separately. Each section has two monitoring sections with six monitoring points on each section. The two monitoring sections are the connection section between adjacent enclosures and the equally divided section located at the center of a single enclosure. The six monitoring points are located at the upper, middle, and lower parts of the monitoring sections, namely the upper, middle, and bottom parts of the enclosure cross-section. Before pouring concrete, the construction workers use a fiber optic grating sensor mounting device to attach the fiber optic grating sensor and thermometer to the steel reinforcement of the steel reinforcement frame. After the fiber optic grating sensor and thermometer are attached, concrete is poured to embed the fiber optic grating sensor and thermometer into the enclosure.

[0008] During vibration monitoring, after the box girder is completed and before the ballast is laid, 3 to 5 test sections are arranged for each box girder section. The test sections are the cross sections of the box girder. Five acceleration sensors are arranged on each test section. One acceleration sensor is located at the center of the lower side of the box girder top plate, one at each end of the box girder top plate, and one at the outer side of the bottom of the box girder web plate with a haunch.

[0009] Train dynamic response monitoring includes box body dynamic displacement testing, box body vibration acceleration testing, and box body dynamic strain testing. During the box body dynamic displacement testing process, after the box body is poured, a trial run is conducted. Before the trial run, fiber optic dynamic displacement sensors are installed at the waist of the box body to test the box body displacement data.

[0010] During the vibration acceleration test of the enclosure, acceleration sensors are placed at the underside of the top plate of the enclosure, at the center of the top surface of the bottom plate of the enclosure, and at the underside of the outer side of the web plate of the enclosure; these sensors are used to detect the vibration characteristics of the enclosure structure under dynamic load.

[0011] This invention addresses the challenge that, during displacement deformation monitoring, a single measuring point can only reflect one-dimensional linear displacement. However, a box girder is a large spatial structure with complex three-dimensional deformation. By simultaneously placing measuring points on the top, sides, and bottom, the deformation state of the entire box girder in space can be reconstructed, allowing for accurate determination of whether it is uniformly settling, tilting, or undergoing torsional deformation. While sensors can be placed only on the top to measure settlement data, it's impossible to determine whether the settlement is due to overall foundation subsidence or the box girder's own bending deformation, potentially leading to misjudgments of the defect's nature. By comparing the top settlement data of different longitudinal sections of the box girder, longitudinal differential settlement can be calculated, a key factor causing track irregularities and affecting traffic safety. Furthermore, by comparing the settlement difference between the two sides of the box girder, the lateral torsion angle can be calculated, assessing whether torsional deformation has occurred.

[0012] During long-term temperature and stress monitoring of the enclosure, the connection section between adjacent enclosures is monitored, as this is the weakest link and critical stress point in the structure. Enclosures connected by expansion joints or hinges are prone to significant relative displacement and stress concentration under load and temperature changes, making them high-risk areas for cracks and damage. Monitoring this section can determine whether the enclosures are working collaboratively; the earliest detection of stress anomalies at this point indicates potential failure of the connection structure. Monitoring the equally divided section at the center of the enclosure is a representative section of the overall structural response. Under uniformly distributed loads, the bending moment is greatest at the center of the enclosure, resulting in the most unfavorable stress. Monitoring this section can directly detect the maximum tensile and compressive stresses that may occur in the structure, determining whether they exceed the material strength. Measuring points are distributed at the top, middle, and bottom of the enclosure. By monitoring the stress and temperature values ​​at the top (top plate), middle (web and waist), and bottom (bottom plate) of the section, a clear stress distribution diagram of the entire section can be drawn, determining whether the structure is under bending, compression, or tension. The bending moment can be calculated from the stress difference between the upper and lower edges, and the axial force can be calculated from the average stress at the upper and lower edges. This is the core of assessing the structural bearing capacity; the measuring points in the middle are more sensitive to the shear deformation of the web, which helps to assess the shear performance.

[0013] The testing is conducted before ballast laying. The ballast and track system themselves have a large mass, which will change the overall dynamic characteristics of the structure; their damping effect will also mask the damping of the structure itself. Testing before laying can eliminate the interference of these superstructures and measure the purest and most original dynamic characteristics of the box girder structure itself, namely natural frequency, mode shape, and damping ratio. One sensor is located at the center of the underside of the box girder top plate. This is the key point for capturing the vertical bending mode shape. In the fundamental mode shape, the amplitude is the largest and the signal is the strongest at this point, which can most sensitively measure the fundamental frequency of the structure. There are two sensors at each end of the box girder top plate. These two points, combined with the center point, can clearly capture the lateral bending mode shape and the torsional mode shape. The lateral bending mode shape can determine the overall sway of the box girder in the horizontal direction. For the torsional mode shape, when the box girder undergoes torsional deformation, the vibration directions at the two ends are opposite. By comparing the signal phase at the two ends, the torsional vibration can be clearly identified. There are two sensors at the underside of the bottom outer side of the box girder web plate. The underside is a stress concentration area with large stiffness changes and is very sensitive to dynamic response.

[0014] During train dynamic response monitoring, an initial health baseline is obtained at the start of operation to provide a basis for comparison in all subsequent diagnoses; by monitoring the dynamic displacement parameters of the waist, construction personnel can directly and sensitively assess changes in the overall stiffness of the structure, which is one of the most critical indicators for judging structural performance degradation; the use of fiber optic technology ensures the long-term stability, accuracy, and anti-interference of data in complex railway environments.

[0015] During box girder vibration acceleration testing, the top plate directly bears the dynamic load from the track and ballast via supports, serving as the input point for vibration energy. Sensors positioned here can most directly and clearly capture the high-frequency vibrations generated by wheel-rail impact. For box girder structures, under train load, the center of the bottom plate is one of the areas with the greatest overall bending deformation. The acceleration data at this point can most clearly reflect the first-order vertical vibration frequency of the structure, which is a key indicator for assessing whether the overall stiffness of the structure has changed. Comparing the acceleration signals of the top and bottom plates, such as amplitude and phase, allows for analysis of the transmission and amplification effects of the dynamic response. The web plate is the main component bearing shear force, and the haunches connecting it to the top and bottom plates are also critical areas with complex and concentrated stress. The vibration characteristics of the web plate differ from bending vibration and better reflect the shear stiffness and shear frequency of the structure. When the train is unevenly loaded or the foundation on both sides of the box girder is uneven, the box girder will undergo torsional deformation. Sensors are placed symmetrically on both sides of the web. By comparing the phase of the signals from the two sides, the torsional vibration mode can be clearly identified. Furthermore, the web connects the top plate and the bottom plate, and abnormal vibration here can indicate whether there is damage or cracking in the connection between the top plate, web, and bottom plate.

[0016] This invention integrates multi-dimensional static and dynamic monitoring with precise deployment of key points, enabling accurate perception and early warning of the health status of box-type roadbed structures throughout their entire lifecycle, from construction to operation, significantly improving the safety and intelligent operation and maintenance level of high-speed railway infrastructure.

[0017] Preferably, one strain gauge is first placed at the center of the bottom surface of the top plate of the box and at the armholes on both sides, and then one strain gauge is placed at the center of the top surface of the bottom plate of the box. Strain gauges are placed on the inner and outer sides of the web plate of the box and at the upper and lower armholes. The inner side uses a strain gauge adjustment device. The construction personnel first fix the strain gauge adjustment device on the inner side of the web plate of the box. After the strain gauge adjustment device is fixed, the base plate is pushed to rotate along the rotation connection point of the first connecting block and the second connecting block through the adjustment mechanism to adjust the position of the three-dimensional strain gauge.

[0018] Through this invention, the core principle of the triaxial strain gauge is to calculate the principal stress and shear stress by measuring the strain in three known directions. The construction personnel can use the adjustment mechanism to ensure that the substrate is rotated to the preset precise angle, thereby avoiding the error of visual judgment when manually pasting and ensuring the theoretical correctness of the three strain gauge directions. Strain gauges installed at the center of the top and bottom plates jointly monitor the overall bending deformation of the box. When the center of the top plate is under compression and the center of the bottom plate is under tension, the box bends downward, and the measured data is a positive bending moment. When the center of the top plate is under tension and the center of the bottom plate is under compression, the box bends upward, and the measured data is a negative bending moment. By comparing the positive and negative bending moments, construction personnel can accurately calculate the magnitude of the overall bending moment and axial force. The web is the primary shear-resistant component. By measuring the differential deformation of strain gauges on the inner and outer sides, the magnitude of the shear force borne by the web can be directly calculated, which construction personnel use to assess the shear resistance of the box girder structure. The haunches, due to their abrupt geometric changes, are areas with complex stresses and are prone to shear cracks or diagonal cracks. Placing strain gauges at these locations allows for the earliest detection of abnormalities and the prevention of failure.

[0019] In areas such as the inner side of the box girder web, the stress is not a simple tension or compression, but a complex state of combined compression, tension, and shear. Triaxial strain gauges can simultaneously measure strain in three directions, thus helping construction personnel to accurately calculate the magnitude and direction of the principal stress and the maximum shear stress at that point. This allows construction personnel to prevent damage to the box girder in advance. The data measured by strain gauges at various locations can facilitate monitoring personnel in preventing damage to the box girder.

[0020] Preferably, the strain gauge at the haunch on the bottom surface of the top plate is used to monitor the stress concentration effect, and the strain gauge at the center of the top surface of the bottom plate is used to monitor the overall bending deformation.

[0021] This invention enables monitoring at the top plate's armpits to prevent localized cracking, and monitoring at the bottom plate's center to ensure overall stability.

[0022] Preferably, the triaxial strain rosettes on the inner side of the web are arranged at angles of 0°, 45°, and 90° for calculating principal stresses and shear stresses.

[0023] Through this invention, principal stress and shear stress can be accurately analyzed to determine the complex stress state inside the web, providing core data support for structural safety.

[0024] Preferably, temperature compensation strain gauges are arranged in the stress-free areas of the box.

[0025] Through this invention, strain gauges used for temperature compensation can eliminate measurement errors caused by temperature changes, ensuring the authenticity and accuracy of strain data. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the main body of the device in Example 1.

[0027] Figure 2 This is a schematic diagram of the triaxial strain flower in Example 1.

[0028] Figure 3 This is a schematic diagram of the frame in Example 1.

[0029] Figure 4 This is a schematic diagram of the slider in Example 1.

[0030] Figure 5 This is a schematic diagram of the threaded blind hole in Example 1.

[0031] Figure 6 This is a schematic diagram of the installation position of the strain gauge adjustment device in Example 1. Detailed Implementation

[0032] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0033] Example 1 This embodiment provides a method for health monitoring of box-type roadbed structures, including static characteristic monitoring and train dynamic response characteristic monitoring; static characteristic monitoring includes displacement deformation monitoring of the box and long-term temperature and stress monitoring of the box; train dynamic response characteristic monitoring includes vibration monitoring and train dynamic response monitoring.

[0034] During displacement and deformation monitoring, after the box-type roadbed is poured, displacement sensors and deflection deformation sensors are installed on the top, sides and bottom of the box-type roadbed respectively. The settlement, horizontal displacement and top plate deflection data of the box-type roadbed are monitored through the displacement sensors and deflection deformation sensors.

[0035] For long-term temperature and stress monitoring of the enclosure, each section of the enclosure is monitored separately. Each section has two monitoring sections with six monitoring points on each section. The two monitoring sections are the connection section between adjacent enclosures and the equally divided section located at the center of a single enclosure. The six monitoring points are located at the upper, middle, and lower parts of the monitoring sections, namely the upper, middle, and bottom parts of the enclosure cross-section. Before pouring concrete, the construction workers use a fiber optic grating sensor mounting device to attach the fiber optic grating sensor and thermometer to the steel reinforcement of the steel reinforcement frame. After the fiber optic grating sensor and thermometer are attached, concrete is poured to embed the fiber optic grating sensor and thermometer into the enclosure.

[0036] During vibration monitoring, after the box girder is completed and before the ballast is laid, 3 to 5 test sections are arranged for each box girder section. The test sections are the cross sections of the box girder. Five acceleration sensors are arranged on each test section. One acceleration sensor is located at the center of the lower side of the box girder top plate, one at each end of the box girder top plate, and one at the outer side of the bottom of the box girder web plate with a haunch.

[0037] Train dynamic response monitoring includes box body dynamic displacement testing, box body vibration acceleration testing, and box body dynamic strain testing. During the box body dynamic displacement testing process, after the box body is poured, a trial run is conducted. Before the trial run, fiber optic dynamic displacement sensors are installed at the waist of the box body to test the box body displacement data.

[0038] During the vibration acceleration test of the enclosure, acceleration sensors are placed at the underside of the top plate of the enclosure, at the center of the top surface of the bottom plate of the enclosure, and at the underside of the outer side of the web plate of the enclosure; these sensors are used to detect the vibration characteristics of the enclosure structure under dynamic load.

[0039] In this embodiment, during displacement deformation monitoring, a single measuring point can only reflect one-dimensional linear displacement, while a box-type roadbed is a large spatial structure whose deformation is a complex three-dimensional behavior. By simultaneously placing measuring points on the top, sides, and bottom, the deformation state of the entire box in space can be reconstructed, thereby accurately determining whether it is uniformly settling, tilting, or undergoing torsional deformation. If sensors are only placed on the top to measure settlement data, it is impossible to determine whether the settlement is caused by the overall subsidence of the foundation or by the bending deformation of the box itself, which may lead to misjudgment of the nature of the defect. By comparing the top settlement data of different longitudinal sections of the box, longitudinal differential settlement can be calculated, which is the core factor causing track irregularities and affecting driving safety. By comparing the settlement difference on both sides of the box, the lateral torsion angle of the box can be calculated to assess whether torsional deformation has occurred.

[0040] During long-term temperature and stress monitoring of the enclosure, the connection section between adjacent enclosures is monitored, as this is the weakest link and critical stress point in the structure. Enclosures connected by expansion joints or hinges are prone to significant relative displacement and stress concentration under load and temperature changes, making them high-risk areas for cracks and damage. Monitoring this section can determine whether the enclosures are working collaboratively; the earliest detection of stress anomalies at this point indicates potential failure of the connection structure. Monitoring the equally divided section at the center of the enclosure is a representative section of the overall structural response. Under uniformly distributed loads, the bending moment is greatest at the center of the enclosure, resulting in the most unfavorable stress. Monitoring this section can directly detect the maximum tensile and compressive stresses that may occur in the structure, determining whether they exceed the material strength. Measuring points are distributed at the top, middle, and bottom of the enclosure. By monitoring the stress and temperature values ​​at the top (top plate), middle (web and waist), and bottom (bottom plate) of the section, a clear stress distribution diagram of the entire section can be drawn, determining whether the structure is under bending, compression, or tension. The bending moment can be calculated from the stress difference between the upper and lower edges, and the axial force can be calculated from the average stress at the upper and lower edges. This is the core of assessing the structural bearing capacity; the measuring points in the middle are more sensitive to the shear deformation of the web, which helps to assess the shear performance.

[0041] The testing is conducted before ballast laying. The ballast and track system themselves have a large mass, which will change the overall dynamic characteristics of the structure; their damping effect will also mask the damping of the structure itself. Testing before laying can eliminate the interference of these superstructures and measure the purest and most original dynamic characteristics of the box girder structure itself, namely natural frequency, mode shape, and damping ratio. One sensor is located at the center of the underside of the box girder top plate. This is the key point for capturing the vertical bending mode shape. In the fundamental mode shape, the amplitude is the largest and the signal is the strongest at this point, which can most sensitively measure the fundamental frequency of the structure. There are two sensors at each end of the box girder top plate. These two points, combined with the center point, can clearly capture the lateral bending mode shape and the torsional mode shape. The lateral bending mode shape can determine the overall sway of the box girder in the horizontal direction. For the torsional mode shape, when the box girder undergoes torsional deformation, the vibration directions at the two ends are opposite. By comparing the signal phase at the two ends, the torsional vibration can be clearly identified. There are two sensors at the underside of the bottom outer side of the box girder web plate. The underside is a stress concentration area with large stiffness changes and is very sensitive to dynamic response.

[0042] During train dynamic response monitoring, an initial health baseline is obtained at the start of operation to provide a basis for comparison in all subsequent diagnoses; by monitoring the dynamic displacement parameters of the waist, construction personnel can directly and sensitively assess changes in the overall stiffness of the structure, which is one of the most critical indicators for judging structural performance degradation; the use of fiber optic technology ensures the long-term stability, accuracy, and anti-interference of data in complex railway environments.

[0043] During box girder vibration acceleration testing, the top plate directly bears the dynamic load from the track and ballast via supports, serving as the input point for vibration energy. Sensors positioned here can most directly and clearly capture the high-frequency vibrations generated by wheel-rail impact. For box girder structures, under train load, the center of the bottom plate is one of the areas with the greatest overall bending deformation. The acceleration data at this point can most clearly reflect the first-order vertical vibration frequency of the structure, which is a key indicator for assessing whether the overall stiffness of the structure has changed. Comparing the acceleration signals of the top and bottom plates, such as amplitude and phase, allows for analysis of the transmission and amplification effects of the dynamic response. The web plate is the main component bearing shear force, and the haunches connecting it to the top and bottom plates are also critical areas with complex and concentrated stress. The vibration characteristics of the web plate differ from bending vibration and better reflect the shear stiffness and shear frequency of the structure. When the train is unevenly loaded or the foundation on both sides of the box girder is uneven, the box girder will undergo torsional deformation. Sensors are placed symmetrically on both sides of the web. By comparing the phase of the signals from the two sides, the torsional vibration mode can be clearly identified. Furthermore, the web connects the top plate and the bottom plate, and abnormal vibration here can indicate whether there is damage or cracking in the connection between the top plate, web, and bottom plate.

[0044] This method integrates multi-dimensional static and dynamic monitoring with precise deployment of key points, enabling accurate perception and early warning of the health status of box-type roadbed structures throughout their entire lifecycle from construction to operation, significantly improving the safety and intelligent operation and maintenance level of high-speed railway infrastructure.

[0045] This embodiment provides a strain gauge adjustment device, including a device body 100. The device body 100 includes a frame 110, and a base plate 150 is provided inside the frame 110. A plurality of strain gauges 120 are provided at one end face of the base plate 150. The base plate 150 and the plurality of strain gauges 120 together form a triaxial strain rosette. A first connecting block 230 is provided on the side wall of the base plate 150, and a second connecting block 350 rotatably connected to the first connecting block 230 is provided on the inner side wall of the frame 110. An adjustment mechanism is provided on the side wall of the frame 110, which is used to push the base plate 150 to rotate along the rotatable connection.

[0046] In this embodiment, when using the strain gauge adjustment device, the construction worker first fixes the frame 110 to the box by passing screws through the bolt holes 170 at the four corners of the frame 110. After the frame 110 is fixed, the construction worker rotates the bolt 130 located below the frame 110, so that the bolt 130 enters the threaded blind hole 510 on the mounting block 140. During the process of the bolt 130 entering the threaded blind hole 510, the bolt 130 will push the sliding member 380 to move along the strip-shaped through hole 320. At this time, the cylinder 410 on the sliding member 380 will press against the base plate 150. The inclined surface 210 at the end allows the substrate 150 to rotate along the rotational connection between the first connecting block 230 and the second connecting block 350, thereby fine-tuning the position of the substrate 150 and preventing the triaxial strain gauge on the substrate 150 from tilting and affecting subsequent measurement data. The adjustment device includes the substrate 150, on which the triaxial strain gauge is first firmly attached. This structure provides better rigid support, allowing the strain to be transferred more completely and losslessly from the concrete structure surface to the strain gauge through the device base, reducing signal attenuation caused by adhesive layer thickness or unevenness.

[0047] After the sliding member 380 located below the frame 110 is adjusted by the construction personnel, the construction personnel then rotate the bolt 130 located on the side wall of the frame 110. As the bolt 130 enters the mounting block 140, it pushes the sliding member 380, causing the cylinder 410 on the sliding member 380 to press against the inclined surface 210 on the side wall of the substrate 150. This, in conjunction with the sliding member 380 below the frame 110, clamps and fixes the substrate 150, preventing the substrate 150 from moving.

[0048] In this embodiment, the adjustment mechanism includes a pushing component disposed on the adjacent side wall of the frame 110. The pushing component includes a mounting block 140. A strip-shaped through hole 320 is provided on the side wall of the frame 110 along the length direction of the side wall of the frame 110. One end of the mounting block 140 near the strip-shaped through hole 320 is recessed inward to form a threaded blind hole 510. A sliding member 380 is provided at the strip-shaped through hole 320 and passes through the strip-shaped through hole 320. A bolt 130 is provided at the threaded blind hole 510 and is used to push the sliding member 380 to move along the strip-shaped through hole 320.

[0049] In this embodiment, the construction worker rotates the bolt 130, causing the nut on the bolt 130 to push the round block 430 to move. The movement of the round block 430 causes the connecting rod 420 to move along the strip-shaped through hole 320. The cross-section of the strip-shaped through hole 320 is rectangular, and the cross-section of the connecting rod 420 is also rectangular, thereby preventing the connecting rod 420 from shaking when moving and improving the stability of the sliding member 380 when moving.

[0050] In this embodiment, the sliding member 380 includes a connecting rod 420 passing through the strip-shaped through hole 320. The end of the connecting rod 420 near the bolt 130 is provided with a round block 430, and the round block 430 is provided with a limiting hole 440 for the bolt 130 to pass through. The end of the connecting rod 420 away from the round block 430 is provided with a cylinder 410. The end of the substrate 150 near the cylinder 410 is provided with an inclined surface 210 arranged along the length direction of the side wall of the substrate 150.

[0051] In this embodiment, the thickness of the round block 430 is less than the width of the strip-shaped through hole 320. When installing the sliding component 380, the construction personnel pass the connecting rod 420 and the round block 430 through the strip-shaped through hole 320 on the frame 110, and then insert the bolt 130 through the limiting hole 440 on the round block 430 into the threaded blind hole 510 on the mounting block 140; thus, it is convenient for the installer to install the sliding component 380 onto the frame 110.

[0052] In this embodiment, the frame 110 is rectangular in shape, and each of the four corners of the frame 110 is provided with a connecting plate 160 connected to the frame 110, and the connecting plate 160 is provided with bolt holes 170.

[0053] In this embodiment, when the construction personnel connect the frame 110 to the box, they align the connecting plates 160 at the four corners of the frame 110 with the pre-embedded holes on the box, so that the bolt holes 170 on the connecting plates 160 are connected to the pre-embedded holes. Then, the screws are inserted into the pre-embedded holes through the bolt holes 170 to fix the frame 110 to the box.

[0054] In this embodiment, the second connecting block 350 is provided with two parallel mounting plates 340, and the mounting plate 360 ​​is provided with mounting holes 360; the two mounting plates 340 and the second connecting block together form a limiting interval 370 for the first connecting block 230 to extend into; the first connecting block 230 is provided with a rotating column 240 that passes through the mounting hole 360.

[0055] In this embodiment, the second connecting block 350 is welded to the two mounting plates 340. When assembling the substrate 150 and the frame 110, the first connecting block 230 on the substrate 150 is first inserted into the limiting interval 370, and then the rotating column 240 is glued to the first connecting block 230 through the mounting hole 360. This makes it convenient for the installer to connect the substrate 150 and the frame 110.

[0056] In this embodiment, the sliding member 380 is made of stainless steel, and the cylinder 410 and the block 430 are welded to the connecting rod 420.

[0057] Through this embodiment, the stainless steel structure has high strength, which can extend the service life of the sliding component 380.

[0058] like Figure 6 As shown, in this embodiment, firstly, one strain gauge 120 is arranged at the center of the bottom surface of the top plate of the box and at the armholes on both sides. Then, one strain gauge 120 is arranged at the center of the top surface of the bottom plate of the box. Strain gauges 120 are arranged on the inner and outer sides of the web plate of the box and at the upper and lower armholes. The inner side adopts a strain gauge 120 adjustment device. The construction personnel first fix the strain gauge 120 adjustment device on the inner side of the web plate of the box. After the strain gauge 120 adjustment device is fixed, the base plate 150 is pushed to rotate along the rotation connection point of the first connecting block 230 and the second connecting block 350 through the adjustment mechanism to adjust the position of the three-dimensional strain gauge.

[0059] In this embodiment, the core principle of the triaxial strain gauge is to calculate the principal stress and shear stress by measuring the strain in three known directions. The construction personnel use the adjustment mechanism to ensure that the substrate is rotated to the preset precise angle, thereby avoiding the error of visual judgment when manually pasting and ensuring the theoretical correctness of the three strain gauges in the 120° direction. Strain gauges 120, installed at the center of the top slab and the center of the bottom slab, jointly monitor the overall bending deformation of the box. When the center of the top slab is under compression and the center of the bottom slab is under tension, the box bends downward, and the measured data is a positive bending moment. When the center of the top slab is under tension and the center of the bottom slab is under compression, the box bends upward, and the measured data is a negative bending moment. By comparing the positive and negative bending moments, construction personnel can accurately calculate the magnitude of the overall bending moment and axial force. The web is the main shear-resistant component. By measuring the differential deformation, the inner and outer strain gauges 120 can directly calculate the magnitude of the shear force borne by the web, which construction personnel use to assess the shear resistance of the box girder structure. The haunches, due to their abrupt geometric changes, are areas with more complex stresses and are prone to shear cracks or diagonal cracks. Placing strain gauges 120 at these locations allows for the earliest detection of abnormalities and the prevention of failure.

[0060] In areas such as the inner side of the box girder web, the stress is not simple tension and compression, but a complex state of combined compression, tension, and shear. A triaxial strain gauge can simultaneously measure strain in three directions, helping construction personnel to accurately calculate the magnitude and direction of the principal stresses and the maximum shear stress at that point. This allows construction personnel to prevent damage to the box girder in advance. Data measured by strain gauges at various locations (120mm) facilitates monitoring and preventative measures against box girder damage.

[0061] In this embodiment, the strain gauge 120 at the underside of the top plate is used to monitor the stress concentration effect, and the strain gauge 120 at the center of the top surface of the bottom plate is used to monitor the overall bending deformation.

[0062] In this embodiment, monitoring at the top plate's haunch prevents localized cracking, while monitoring at the bottom plate's center ensures overall stability.

[0063] In this embodiment, the triaxial strain rosettes on the inner side of the web are arranged at angles of 0°, 45°, and 90°, which are used to calculate the principal stress and shear stress.

[0064] Through this embodiment, principal stress and shear stress can be accurately analyzed to determine the complex stress state inside the web, providing core data support for structural safety.

[0065] In this embodiment, temperature compensation strain gauges 120 are arranged in the stress-free area of ​​the box.

[0066] Through this embodiment, the strain gauge 120 used for temperature compensation can eliminate measurement errors caused by temperature changes, ensuring the authenticity and accuracy of strain data.

[0067] It is readily understood that those skilled in the art can combine, split, or reorganize the embodiments provided in this application to obtain other embodiments, all of which do not exceed the protection scope of this application.

[0068] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the embodiments shown are only part of the embodiments of the present invention. The actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for monitoring the health of a box culvert structure, the method comprising: The monitoring includes static force characteristic monitoring and train dynamic response characteristic monitoring; the static force characteristic monitoring includes box displacement deformation monitoring and long-term temperature and stress monitoring of the box; the train dynamic response characteristic monitoring includes excitation monitoring and train dynamic response monitoring.

2. The method of claim 1, wherein: In the displacement deformation monitoring, displacement sensors and deflection deformation sensors are arranged on the top, both sides and bottom of the box-type roadbed after the box-type roadbed is poured, and the displacement sensors and deflection deformation sensors are used to monitor the box-type roadbed settlement, horizontal displacement and roof deflection data.

3. The method of claim 1, wherein: In the long-term temperature and stress monitoring of the box, each box is monitored, wherein 2 monitoring sections are arranged in each box, and 6 monitoring points are arranged on the 2 monitoring sections; the 2 monitoring sections are the connecting sections of adjacent boxes and the equally divided sections at the center of a single box; the 6 monitoring points are located at the upper, middle and lower parts of the monitoring sections, i.e. the upper, waist and bottom parts of the cross section of the box; before pouring the concrete, the construction personnel bind the fiber Bragg grating sensors and thermometers on the steel bars of the steel reinforcement framework through the installation device of the fiber Bragg grating sensors on the steel bars; after the fiber Bragg grating sensors and thermometers are bound, the concrete is poured, and the fiber Bragg grating sensors and thermometers are buried in the box.

4. The method of claim 1, wherein: In the excitation monitoring, 3-5 test sections are arranged in each box after the box is completed and before the ballast is laid, and the test sections are the cross sections of the box; 5 acceleration sensors are arranged on each test section, and the 5 acceleration sensors are arranged at the center of the lower side of the roof of the box, at both ends of the roof of the box, and at the haunches outside the bottom of the web of the box.

5. The method of claim 1, wherein: The train dynamic response monitoring includes box dynamic displacement test, box vibration acceleration test and box dynamic strain test; in the box dynamic displacement test, after the box is poured, the test is carried out, and before the test, the fiber dynamic displacement sensors are installed at the waist of the box to test the displacement data of the box.

6. The method of claim 5, wherein: In the box vibration acceleration test, the acceleration sensors are arranged at the haunches of the bottom surface of the roof of the box, at the center of the top surface of the bottom plate of the box and at the haunches outside the web of the box; the acceleration sensors are used to detect the vibration characteristic data of the box structure under the action of dynamic load.

7. The method of claim 5, wherein: In the box dynamic strain test, first, 1 strain gauge (120) is arranged at the center and both sides of the haunches of the bottom surface of the roof of the box, and then 1 strain gauge (120) is arranged at the center of the top surface of the bottom plate of the box; strain gauges (120) are arranged at the inner and outer sides and upper and lower haunches of the web of the box, wherein the inner side adopts a strain gauge (120) adjusting device, and the construction personnel first fix the strain gauge (120) adjusting device at the inner side of the web of the box; after the strain gauge (120) adjusting device is fixed, the base plate (150) is rotated along the rotation connection point of the first connecting block (230) and the second connecting block (350) through the adjusting mechanism to adjust the position of the three-way strain flower.

8. The method of claim 7, wherein: The strain gauges (120) at the haunches of the bottom surface of the roof are used to monitor the stress concentration effect, and the strain gauges (120) at the center of the top surface of the bottom plate are used to monitor the overall bending deformation.

9. The method of claim 8, wherein: The three-way strain flowers at the inner side of the web are arranged at angles of 0°, 45° and 90°, and are used to calculate the principal stress and shear stress.

10. The method of claim 8, wherein: The temperature compensation strain gauge (120) is arranged in a stress-free zone of the box body.

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