Three-dimensional displacement measuring device for new and old splicing wide joints of fabricated beam bridge

Abstract

The invention, which belongs to the technical field of bridge structure detection, discloses a three-dimensional displacement measurement device for a new and old widening joint of a fabricated beam bridge, comprising a single-degree-of-freedom displacement meter, a fixing assembly, an acquisition instrument and a data transmission link. The single-degree-of-freedom displacement meter is obliquely arranged and fixed on a new beam body and an old beam body on the two sides of a wet joint in a spanning manner through a fixing assembly, and initial distances are reserved at the two end points of the single-degree-of-freedom displacement meter in the x direction, the y direction and the z direction; according to the device, three-dimensional relative displacement is indirectly deduced through unidirectional length change on the basis of local tiny deformation characteristics within the range of 50 cm around a wet joint. By adopting the three-dimensional displacement measurement device for the new and old widening joint of the fabricated beam bridge, the problems of complex installation, high cost, poor adaptability, insufficient data transmission stability, low vertical initial height difference control precision and the like of the existing three-dimensional displacement measurement device in the monitoring of the new and old widening joint of the fabricated beam bridge are solved.

Description

Technical Field

[0001] This invention relates to the field of bridge monitoring structure technology, and in particular to a three-dimensional displacement measurement device for splicing joints between new and old sections of prefabricated beam bridges. Background Technology

[0002] In transportation infrastructure upgrading and renovation projects, prefabricated beam bridges are widely used in bridge widening and renovation projects due to their advantages such as high construction efficiency and easy quality control. The connection between the new and old beams usually adopts a wet joint structure to achieve coordinated stress distribution. The three-dimensional relative displacement of this joint area (including lateral (bridge cross section direction), longitudinal (bridge span direction) and vertical displacement) is the core indicator reflecting the coordinated working performance of the new and old beams and assessing the operational safety of the structure.

[0003] During operation, the bridge is affected by various factors such as alternating temperature changes, uneven foundation settlement, and repeated vehicle loads, which can easily cause relative deformation between the old and new beams on both sides of the wet joint. If this displacement exceeds the design allowable range, it may lead to cracking of the wet joint, corrosion of the reinforcing steel, or even safety hazards such as separation of the old and new beams. Therefore, long-term and accurate monitoring of the three-dimensional displacement of the wet joint area is necessary.

[0004] Currently, the mainstream approach in bridge three-dimensional displacement monitoring is the "multi-sensor orthogonal arrangement" technique. This involves installing independent displacement gauges in the x, y, and z orthogonal directions, collecting multiple sets of unidirectional displacement data, and then stitching and integrating them to achieve three-dimensional displacement measurement. However, this approach has the following significant drawbacks when applied to monitoring the joints between new and old sections of prefabricated beam bridges: Installation and calibration are difficult: the width of wet joints is usually only 20-50cm, the space is extremely small, and the orthogonal arrangement of multiple sensors requires multiple installation points to be reserved on the new and old beams. This not only easily interferes with on-site construction, but also the installation and calibration process of multiple sensors is complicated and difficult to adapt to the construction environment in a narrow space. Cost versus accuracy conflict: The configuration of multiple sensors leads to a significant increase in hardware procurement costs and on-site wiring costs. At the same time, the difference in response speed of different sensors can easily cause synchronization errors, which will accumulate during the data stitching process and affect the overall accuracy of three-dimensional displacement measurement. Poor scene adaptability: Installation errors are inevitable during the construction of new and old beams. Orthogonally arranged sensors are prone to deviation from the actual displacement direction of the beam due to initial installation position deviation, making it impossible to accurately capture the real displacement state. Insufficient data transmission stability: Traditional monitoring devices rely on a single wired link for data transmission. The complex operating environment of bridges makes cables susceptible to damage from vibration, corrosion, and external impacts, leading to data transmission interruptions and compromising the continuity of monitoring.

[0005] Therefore, there is an urgent need for a low-cost, highly adaptable three-dimensional displacement measurement device suitable for the splicing joints between new and old prefabricated beam bridges. Summary of the Invention

[0006] The purpose of this invention is to provide a three-dimensional displacement measurement device for the splicing joint between new and old sections of prefabricated beam bridges, which solves the problems of existing three-dimensional displacement measurement devices in monitoring the splicing joint between new and old sections of prefabricated beam bridges, such as complex installation, high cost, poor adaptability, insufficient data transmission stability, and low accuracy in controlling the initial vertical height difference.

[0007] To achieve the above objectives, this invention provides a three-dimensional displacement measurement device for the splicing joint between new and old beams in prefabricated beam bridges. The device includes a single-degree-of-freedom displacement gauge, a fixing component, a data acquisition instrument, and a data transmission link. The fixing component includes high-strength anchors, adjusting nuts, and a ball joint structure. The adjusting nut is pre-screwed into the embedded reinforcing bars on one side of the beam to form a preset initial height difference in the z-direction. The single-degree-of-freedom displacement gauge is obliquely spanned and fixed to the new and old beams on both sides of the wet joint via the fixing component, with initial distances reserved at its two endpoints in the x, y, and z directions. The data transmission link is used to upload the measurement data from the single-degree-of-freedom displacement gauge to a remote server. The device indirectly derives the three-dimensional relative displacement based on the localized micro-deformation characteristics within a 50cm radius around the wet joint through unidirectional length changes.

[0008] Preferably, the adjusting nut is an M16 high-precision nut. By adjusting its screwing height on the pre-embedded steel bar, the anchors on both sides of the wet joint form a preset initial distance in the z direction, with an adjustment accuracy of ≤±1mm.

[0009] Preferably, the high-strength anchor is of model M16 and made of No. 45 steel. One end of the anchor is mechanically connected to the pre-embedded steel bars of the old and new beams, and the other end is hinged to the endpoint of the single-degree-of-freedom displacement meter through a ball joint structure, so that the single-degree-of-freedom displacement meter can move synchronously with the deformation of the beam.

[0010] Preferably, the installation direction of the single-degree-of-freedom displacement gauge is defined by spherical coordinate initial parameters, which include the horizontal rotation angle. Vertical corner and initial length During installation, the above parameters are recorded and stored in the data acquisition instrument for the purpose of deriving three-dimensional relative displacement.

[0011] Preferably, the single-degree-of-freedom displacement gauge is a wire-type displacement gauge with a range of ±5mm and an accuracy of 0.01mm.

[0012] Preferably, the pre-embedded steel bar has a diameter of 14-16mm, an exposed length of 13-15cm, and a verticality deviation of ≤0.5° after being implanted into the beam.

[0013] Preferably, the data transmission link includes a shielded cable, a secondary cable, and a 4G network link; the measurement data of the single-degree-of-freedom displacement meter is transmitted to the data acquisition instrument via the shielded cable, and the data acquisition instrument uploads the data to the remote server database via the secondary cable or a 4G wireless module.

[0014] Preferably, the data acquisition device is a waterproof data acquisition device with a sampling frequency of 1Hz and an integrated offline cache module (cache capacity ≥ 100,000 records). It automatically retransmits missing data after the network is restored. The data acquisition device is powered by a 220V AC power supply or a solar panel.

[0015] Preferably, this device is suitable for scenarios where beam deformation within a 50cm radius around the wet joint is negligible, and the horizontal rotation angle change Δ of the single-degree-of-freedom displacement gauge during the operation period is... θ Vertical rotation angle change Δ Φ and length change Δ l It is a tiny quantity, and Δ l The direction of change is consistent with the initial installation direction of the single-degree-of-freedom displacement gauge.

[0016] Therefore, the present invention employs the aforementioned three-dimensional displacement measuring device for splicing joints between new and old sections of prefabricated beam bridges, and the technical effects are as follows: 1) Simplified structure: A single-degree-of-freedom displacement meter is used instead of a multi-sensor combination. Three-dimensional measurement is achieved through spatial geometric relationships, reducing the number of hardware components by more than 50% and reducing installation complexity and cost; 2) Precise Height Control: By adjusting the vertical height difference of the pre-set anchors using the nut, precise control of the initial distance in the z-direction is achieved, which is the initial vertical rotation angle. Precise measurements provide a structural foundation and improve the accuracy of three-dimensional displacement conversion; 3) Strong scene adaptability: The oblique installation scheme is designed for the narrow space of wet joints. The anchor and ball joint structure ensure the synchronous deformation and solve the measurement deviation problem caused by construction error in traditional orthogonal installation. 4) Reliable data transmission: The "wired + 4G wireless" dual transmission mode ensures data continuity, and the offline caching function avoids data loss due to network interruption; 5) Measurement accuracy assurance: Based on the theoretical model of the assumption of local small deformation, combined with the initial parameter calibration of spherical coordinates, the three-dimensional displacement measurement error is controlled within 0.1mm, which meets the accuracy requirements of engineering monitoring.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an embodiment of a three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to the present invention. Figure 2 This is the present invention. Figure 1 Side view of the cross section at point AA; Figure 3 This is a schematic diagram of the installation parameters of an embodiment of a three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to the present invention.

[0019] Figure Labels 1. Single-degree-of-freedom displacement gauge; 2. Wet joint; 3. High-strength anchors. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "comprising" or "including," and similar terms used in this invention, mean that the element or object preceding the term encompasses the elements or objects listed following the term and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] Example 1 I. Implementation Scenarios: This embodiment is applied to the widening and renovation project of a prefabricated concrete T-beam bridge on a highway. Both the old and new beams are prestressed concrete T-beams. The width of wet joint 2 is 35cm and the height of the beam is 1.8m. It is necessary to conduct long-term monitoring of the three-dimensional relative displacement of the wet joint 2 area in the lateral (y-direction), longitudinal (x-direction), and vertical (z-direction) directions. The monitoring period is 5 years, and the measurement error is required to be ≤0.1mm. The data transmission must be continuous and uninterrupted.

[0023] II. Component Preparation: According to the technical solution and claims, the following components shall be prepared: Single-degree-of-freedom displacement gauge 1: A wire-type displacement gauge is selected, with a range of ±5mm, a measurement accuracy of 0.01mm, an IP67 protection rating, and is suitable for the humid outdoor environment of bridges. Fixing components: M16 high-strength anchor 3 (material 45 steel, tensile strength ≥600MPa), M16 high-precision adjusting nut (precision grade 6H), stainless steel ball joint structure (wear resistance coefficient ≤0.05); Embedded steel bars: HRB400 grade threaded steel bars, 15mm in diameter, 14cm exposed length, with rust removal treatment on the surface; Data Acquisition Unit: Waterproof data acquisition unit with a sampling frequency of 1Hz, integrating an RS485 wired transmission module, a 4G full network wireless module, and an 8GB offline cache module with a cache capacity of ≥100,000 records, meeting the requirements for 24-hour continuous storage; Transmission cables: shielded twisted pair (interference immunity level ≥120dB), secondary cables (flame retardant level B1); Auxiliary equipment: total station (measurement accuracy ±0.5mm), digital height gauge (accuracy ±0.01mm), solar panel (30W power, suitable for outdoor scenarios without mains power), server (deployed in the project monitoring center, supporting TCP / IP protocol data reception).

[0024] III. Installation and Debugging Process (e.g.) Figures 1-3 (as shown) (I) Beam pretreatment and embedded steel reinforcement insertion: At the corresponding positions on the old beam on the left and the new beam on the right of wet joint 2 (15cm from the edge of wet joint 2), a diamond drilling machine is used to drill holes with a diameter of 18mm and a depth of 10cm. The verticality deviation of the drilling is ≤0.3° (meeting the requirement of ≤0.5°). Clean the dust and debris from the borehole, inject anchoring adhesive (compressive strength ≥30MPa), insert the pre-embedded steel bars into the hole, ensure that the steel bars are firmly bonded to the beam concrete, and control the exposed length to 14cm. After the anchoring adhesive has cured for 72 hours to reach the design strength, proceed with the subsequent installation.

[0025] (II) Installation of adjusting nuts and calibration of vertical height difference: According to the initial vertical rotation angle of the design =40°, combined with the initial length of the displacement gauge installation. =45cm, the required initial height difference in the z-direction is calculated to be 3.8cm; M16 high-precision adjusting nuts were pre-screwed into the pre-embedded steel bars of the old beam on the left side. The elevation of the top surface of the nut was monitored in real time using a digital height gauge. The nut was gradually adjusted to the preset height. Finally, the vertical height difference between the top surface of the nut and the top surface of the pre-embedded steel bar on the right side was 3.8cm, and the error was controlled within ±0.3mm (meeting the adjustment accuracy requirement of ≤±1mm).

[0026] (III) Installation of anchors and displacement gauges: The high-strength anchor 3 is fixed to the pre-embedded steel bar by thread connection (the bottom of the left anchor is tightly fitted with the top surface of the adjusting nut, and the right anchor is directly fixed to the top of the pre-embedded steel bar). Tighten with a torque wrench, and tighten the torque ≥80N·m to ensure that the anchor is not loose. Insert the ball joint structures at both ends of the single-degree-of-freedom displacement gauge 1 into the grooves of the left and right side anchors respectively, tighten the locking bolts, and check the installation status of the displacement gauge: ensure that the displacement gauge is obliquely straddling both sides of the wet joint 2 without bending or excessive stretching, and that the two ends are reserved with initial distances in the x, y, and z directions, and that the ball joint structure can rotate flexibly without restricting the transmission of beam deformation.

[0027] (iv) Parameter calibration and entry: The three-dimensional coordinates of the two ends of the displacement gauge were measured using a total station: coordinates of the left end point (x1=0m, y1=0m, z1=0.038m) and coordinates of the right end point (x2=0.085m, y2=0.062m, z2=0m). The initial parameters are calculated based on three-dimensional coordinates, using the following formula: initial length : Substituting the coordinates, we get: l 0 = 0.45m; Horizontal corner (The angle between the single-degree-of-freedom displacement gauge and the x-axis in the xy-plane): Substituting the coordinates, we get: ≈36.5°; Vertical corner : Substituting the coordinates, we get: ≈40°; The calculated initial length l 0. Horizontal turning angle θ 0. Vertical corner Initial parameters are entered into the storage module via the RS485 interface of the data acquisition instrument to complete parameter calibration.

[0028] (v) Transmission link setup and debugging: Use shielded twisted-pair cable to connect the signal output end of the single-degree-of-freedom displacement meter 1 to the signal input end of the data acquisition instrument. The cable is fixed along the side of the beam to avoid direct exposure to the bridge deck pavement layer, and the bending radius is ≥10cm. The data acquisition device is installed in a protective box (IP65 protection level) on the side of the beam and connected to a solar panel for power supply to ensure that the output voltage is stable at 12V; Configure the 4G module APN parameters of the data acquisition device, establish a TCP / IP connection with the monitoring center server, and set the data upload mode to "wired priority + wireless backup": in areas where bridge deck wiring conditions permit, connect the data acquisition device to the bridge centralized processing equipment through a secondary cable; in remote bridge sections in the field, automatically switch to 4G wireless transmission, and set the data upload interval to 1 minute / time; Debugging the offline caching function: After disconnecting the 4G network, the data acquisition instrument automatically stores the measurement data. After the network is restored, the missing data is retransmitted within 10 seconds to verify the reliability of the cache.

[0029] IV. Data Processing and Three-Dimensional Displacement Calculation: Displacement gauge monitors the change in length Δ during the operation period in real time. l After converting the analog signal into a digital signal, it is transmitted to the data acquisition instrument via a shielded cable; The data acquisition instrument filters the raw data to remove 50Hz power frequency interference and high-frequency noise generated by vehicle vibration, obtaining effective Δ... l data; Valid data is uploaded to the monitoring center server via wired or 4G wireless link, and the server retrieves the pre-stored initial parameters. =36.5° =40°, calculate the three-dimensional relative displacement using the following formula: Longitudinal displacement Δx=Δ l ×sin ×cos ; Lateral displacement Δy=Δ l ×sin ×sin ; Vertical displacement Δz=Δ l ×cos ; Example calculation: When the displacement gauge measures Δ l When the value is 2.5mm, substituting into the formula, we get Δx = 2.5 × sin40° × cos36.5° ≈ 1.6mm, Δy = 2.5 × sin40° × sin36.5° ≈ 1.2mm, and Δz = 2.5 × cos40° ≈ 1.9mm. After calibration, the measurement error is 0.08mm, which meets the accuracy requirement of ≤0.1mm.

[0030] V. Verification of Implementation Results: This embodiment, through the above installation and debugging process, achieves long-term stable monitoring of three-dimensional displacement in the wet joint area. The verification results are as follows: Ease of installation: The unit displacement meter and simplified fixing components require only 2 installation points, reducing installation time by 60% compared to traditional multi-sensor solutions, and eliminating construction interference issues; Cost control: Hardware quantity reduced by more than 50%, cabling cost reduced by 40%, and no complex calibration equipment required; Measurement accuracy: The three-dimensional displacement measurement error is stable between 0.05-0.09mm, which meets the accuracy requirements for engineering monitoring; Data stability: The dual transmission modes of "wired + 4G wireless" and offline caching function ensure no data loss within a 5-year monitoring period and a transmission interruption rate of 0. Scene adaptability: The angled installation scheme is suitable for narrow wet joint spaces of 35cm, and the ball joint structure effectively offsets construction errors and has good deformation synchronization.

[0031] Therefore, the present invention adopts the above-mentioned three-dimensional displacement measuring device for the splicing joint between new and old prefabricated beam bridges, which solves the problems of complex installation, high cost, poor adaptability, insufficient data transmission stability and low accuracy of vertical initial height difference control of existing three-dimensional displacement measuring devices in the monitoring of splicing joints between new and old prefabricated beam bridges.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A three-dimensional displacement measuring device for splicing joints between new and old sections of prefabricated beam bridges, characterized in that: The device includes a single-degree-of-freedom displacement gauge, a fixing component, a data acquisition instrument, and a data transmission link. The fixing component includes high-strength anchors, adjusting nuts, and a ball joint structure. The adjusting nut is pre-screwed into the embedded steel bars of one side of the beam to form a preset initial height difference in the z-direction. The single-degree-of-freedom displacement gauge is obliquely spanned and fixed to the old and new beams on both sides of the wet joint through the fixing component, with its two ends reserved with initial distances in the x, y, and z directions. The data transmission link is used to upload the measurement data of the single-degree-of-freedom displacement gauge to a remote server. The device indirectly derives the three-dimensional relative displacement based on the local small deformation characteristics within a 50cm range around the wet joint through unidirectional length changes.

2. The three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to claim 1, characterized in that: The adjusting nut is an M16 high-precision nut. By adjusting its screwing height on the pre-embedded steel bar, the anchors on both sides of the wet joint form a preset initial distance in the z direction, with an adjustment accuracy of ≤±1mm.

3. The three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to claim 1, characterized in that: The high-strength anchor is of model M16 and made of No. 45 steel. One end of the anchor is mechanically connected to the pre-embedded steel bars of the old and new beams, and the other end is hinged to the endpoint of the single-degree-of-freedom displacement gauge through a ball joint structure, so that the single-degree-of-freedom displacement gauge can move synchronously with the deformation of the beam.

4. The three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to claim 1, characterized in that: The installation direction of the single-degree-of-freedom displacement gauge is defined by spherical coordinate initial parameters, which include the horizontal rotation angle. Vertical corner and initial length During installation, the above parameters are recorded and stored in the data acquisition instrument for the purpose of deriving three-dimensional relative displacement.

5. A three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to claim 1, characterized in that: The single-degree-of-freedom displacement gauge is a wire-type displacement gauge with a range of ±5mm and an accuracy of 0.01mm.

6. A three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to claim 1, characterized in that: The pre-embedded steel bars have a diameter of 14-16mm, an exposed length of 13-15cm, and a verticality deviation of ≤0.5° after being implanted into the beam.

7. A three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to claim 1, characterized in that: The data transmission link includes a shielded cable, a secondary cable, and a 4G network link; the measurement data of the single-degree-of-freedom displacement meter is transmitted to the data acquisition instrument via the shielded cable, and the data acquisition instrument uploads the data to the remote server database via the secondary cable or a 4G wireless module.

8. A three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to claim 1, characterized in that: The data acquisition device is waterproof, with a sampling frequency of 1Hz, and integrates an offline cache module. It automatically retransmits missing data after the network is restored. The data acquisition device is powered by a 220V AC power supply or a solar panel.

9. A three-dimensional displacement measuring device for splicing new and old joints in prefabricated beam bridges according to claim 1, characterized in that: This device is suitable for scenarios where beam deformation is negligible within a 50cm radius around wet joints, and the horizontal rotation Δ of a single-degree-of-freedom displacement gauge during operation. θ Vertical rotation angle change Δ Φ and length change Δ l It is a tiny quantity, and Δ l The direction of change is consistent with the initial installation direction of the single-degree-of-freedom displacement gauge.

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