A truss reinforcement structure and monitoring method for composite beam bridges

Abstract

This invention provides a truss reinforcement structure and monitoring method for composite beam bridges. The truss reinforcement structure includes a load-bearing crossbeam, upper pads, and force-transmitting diagonal bracing assemblies. Multiple upper pads are horizontally spaced along the load-bearing crossbeam, and the reinforcing diagonal braces are correspondingly positioned with the upper pads. Carbon fiber fabric is applied to the surface of the load-bearing crossbeam, and multiple sensing elements are axially spaced at the interface between the carbon fiber fabric and the load-bearing crossbeam. Fiber Bragg grating sensors are correspondingly installed in the carbon fiber resistance measurement channels. The monitoring method includes forming a composite truss load-bearing system, axially bonding continuous unidirectional carbon fiber fabric to the surface of the crossbeam, deploying resistance measurement channels on the bridge to collect resistance change data, measuring the axial strain of the crossbeam using fiber Bragg grating sensors, compensating for the resistance change rate and strain distribution data, extracting structural response parameters, and determining whether the structure is in an abnormal state. This invention can improve the lateral load-bearing performance of composite beam bridges and achieve structural perception monitoring and safety status assessment.

Description

Technical Field

[0001] This invention relates to the field of truss reinforcement for composite beam bridges, and more particularly to a truss reinforcement structure and monitoring method for composite beam bridges. Background Technology

[0002] Currently, with the continuous increase in traffic load and the extension of service life, a large number of highway and railway bridges have experienced varying degrees of performance degradation and structural damage. In order to improve the load-bearing capacity and durability of bridges, truss-type reinforcement structures are widely used in the reinforcement projects of reinforced concrete beam bridges and composite beam bridges due to their advantages such as flexible construction, clear stress distribution, and convenient construction.

[0003] The structural form of a composite truss is a core factor determining its reinforcement effectiveness. Different configurations alter the force flow path within the bridge, significantly impacting load transfer efficiency in the longitudinal and lateral directions, stress distribution, and other aspects. Currently, typical configurations include triangular, X-shaped, and K-shaped structures, with the K-shaped configuration showing the best effect in reducing maximum deflection and distortion.

[0004] Traditional truss reinforcement structures often employ all-steel or steel-concrete composite forms. While these can significantly improve the bending stiffness and load-bearing capacity of the main beam, they still have the following shortcomings: They are relatively heavy, imposing secondary additional loads on the original structure, which is detrimental to the overall stress distribution of long-span bridges; corrosion is a significant problem, as steel components are prone to rusting in humid or chloride-rich environments, leading to a decline in reinforcement effectiveness over time; monitoring methods are independent, with structural reinforcement and health monitoring systems typically deployed separately, resulting in complex sensor installation, low reliability, and high maintenance costs; and they lack self-sensing capabilities, meaning the reinforced structure itself cannot directly reflect changes in bridge deformation or stress state.

[0005] It is evident that choosing the right material is a crucial decision for ensuring the reinforcement effect and long-term service performance of composite trusses. Existing composite trusses mainly utilize traditional materials such as steel, aluminum, and steel-concrete composite. Steel is widely used due to its high stiffness and strength, but its inherent defects are also prominent, including poor corrosion resistance, heavy weight, fatigue, and temperature sensitivity. Therefore, the application of metallic materials in composite trusses presents a dilemma in balancing strength, weight, and durability. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a truss reinforcement structure for composite beam bridges that can improve the lateral stress performance of composite beam bridges, and a monitoring method that can realize self-sensing monitoring and safety status assessment of the reinforcement structure of composite beam bridges.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A truss reinforcement structure for a composite beam bridge is characterized by comprising a load-bearing crossbeam connected to the bottom surface of adjacent main beams of the bridge, multiple upper pads disposed on the lower surface of the wet joints of the composite beam bridge, and multiple sets of force-transmitting diagonal bracing assemblies connecting the upper pads and the load-bearing crossbeams. The multiple upper pads are horizontally spaced along the load-bearing crossbeams, and the reinforcing diagonal bracings are correspondingly disposed with the upper pads to form a truss load-bearing assembly that improves the lateral force-bearing performance of the composite beam bridge. The surface of the load-bearing crossbeam is provided with carbon fiber fabric with the main force direction along the axial direction of the load-bearing crossbeam. Multiple sensing elements are spaced along the axial direction at the interface between the carbon fiber fabric and the load-bearing crossbeam to form a carbon fiber resistance measurement channel. A fiber optic grating sensor is correspondingly disposed in the carbon fiber resistance measurement channel.

[0008] Furthermore, multiple sensing elements are spaced apart perpendicular to the length direction of the load-bearing beam, and fiber Bragg grating sensors are arranged parallel to the length direction of the load-bearing beam. Multiple fiber Bragg grating sensors located in the same carbon fiber resistance measurement channel are arranged parallel to the electrode spacing.

[0009] Furthermore, the internal carbon fibers of the carbon fiber fabric are arranged parallel to the axial direction of the load-bearing beam to form a continuous unidirectional fiber fabric. The continuous unidirectional fiber fabric is bonded to the surface of the load-bearing beam to form a continuous adhesive layer with interfacial shear force transmission and deformation coordination capabilities.

[0010] Furthermore, the load-bearing beam is a glass fiber beam that achieves structural lightweighting, and the reinforcing diagonal brace is a steel-concrete composite diagonal brace.

[0011] Furthermore, the load-bearing crossbeam is connected to the bottom surface of the adjacent main beam via a connecting plate. The connecting plate has first bolt holes symmetrically distributed on both sides along the length of the load-bearing crossbeam. Each group of first bolt holes is evenly distributed along the length of the bottom of the beam bridge. The first bolt holes are used for bolting the connecting plate to the bottom surface of the main beam of the beam bridge. The upper pad has second bolt holes symmetrically distributed on both sides along the length of the load-bearing crossbeam. Each group of second bolt holes is evenly distributed along the length of the bottom of the beam bridge. The second bolt holes are used for bolting the upper pad to the wet joint of the beam bridge.

[0012] A method for monitoring the stress state of a bridge based on a truss reinforcement structure for a composite beam bridge includes the following steps: Step 1) Determine the arrangement position of the composite truss and the mounting hole positions of the connecting plate and the upper pad. Fix the connecting plate to the bottom surface of the main beam and the upper pad to the bottom surface of the wet joint according to the mounting hole positions. Connect the CFST diagonal brace between the upper pad and the GFRP crossbeam so that the CFST diagonal brace is arranged in a V-shape to form a composite truss force system. Step 2) Continuous unidirectional carbon fiber fabric is bonded along the axial direction on the surface of the GFRP beam so that the carbon fiber fabric and the GFRP beam form a cooperative force-bearing component. Step 3) Install resistance measurement channels on the bridge to collect resistance change data ΔR at multiple monitoring points along the fiber direction on the carbon fiber fabric, and measure the axial strain of the GFRP beam by using fiber optic grating sensors installed in the corresponding stress areas. Step 4) Calculate the theoretical resistance change value based on the axial strain measured by the fiber optic grating sensor, and compare it with the resistance change data ΔR to obtain the deviation value. Then, perform compensation processing on the resistance change rate and strain distribution data based on the deviation value to obtain the compensated resistance change rate and strain distribution data. Step 5): Extract structural response parameters based on the compensated resistance change rate and strain distribution data, and determine whether the structure is in an abnormal state based on the extracted structural response parameters.

[0013] Further, in step 4), the calculation expression for the theoretical resistance change value based on the axial strain measured by the fiber Bragg grating sensor is as follows: in, This is the theoretical resistance change value. The initial resistance, The parameter is the rate of change of resistance. The axial strain of the GFRP beam is measured by a fiber Bragg grating sensor.

[0014] Further, in step 4), the compensation processing of the resistance change rate and strain distribution data based on the deviation value includes: If the deviation value is within the preset allowable range, the least squares method is used to fit the resistance change data ΔR at each monitoring point to obtain the compensated resistance change rate distribution function: Where x is the position coordinate along the length direction of the GFRP beam (1), Let x be the rate of change of resistance after compensation. The initial resistance, Let n be the resistance change rate parameter of the k-th monitoring point, where k is the index of the monitoring point and n is the number of monitoring points. The compensated strain distribution data are calculated based on the compensated resistance change rate distribution function: in, This represents the axial strain at position x after compensation. The rate of change of resistance; If the deviation value exceeds the preset allowable range, based on the temperature change data of the monitored area... Temperature sensitivity coefficient Temperature compensation is applied to the actual measured axial strain data to obtain the temperature-compensated mechanical strain. Based on the temperature-compensated mechanical strain... Recalculate the theoretical resistance change value ,in, To determine the corrected theoretical resistance change value, the resistance change correction amount caused by temperature influence is determined based on the difference between the theoretical resistance change values ​​before and after compensation. This correction amount is then used to correct the resistance change rate data obtained from real-time monitoring.

[0015] Furthermore, based on temperature change data in the monitored area Temperature sensitivity coefficient Temperature compensation is performed on the measured axial strain data to obtain the temperature-compensated mechanical strain. The calculation expression is: in, The axial strain of the GFRP beam (1) measured by the fiber optic grating sensor (7); The calculation expression for the correction amount of the resistance change caused by the temperature effect is as follows: in, This is the resistance correction amount caused by temperature changes. This represents the theoretical change in resistance. The calculation expression for correcting the resistance change rate data obtained from real-time monitoring using the aforementioned resistance change correction amount is as follows: in, This is the corrected rate of change of resistance. This is the corrected resistance change data. This is to obtain the resistance change rate data in real time.

[0016] Further, in step 5), the structural response parameters include the compensated structural strain distribution, the beam deformation development trend, the resistance-strain deviation, and the local abnormal change rate; wherein, the compensated structural strain distribution is obtained by fitting the compensated resistance change rate data based on different monitoring points, the beam deformation development trend is determined based on the change state of the compensated axial strain at multiple monitoring points along the beam length direction, the resistance-strain deviation is calculated by the difference between the theoretical resistance change value and the measured resistance change value, and the local abnormal change rate is the difference or abrupt change value of the compensated resistance change rate at adjacent monitoring points; The step of determining whether a structure is in an abnormal state based on the extracted structural response parameters includes: comparing the structural response parameters with a preset threshold; when the structural response parameters exceed the corresponding preset threshold, outputting a structural anomaly warning message and the corresponding anomaly location; and obtaining the development trend of the structural stress state based on the changes in the structural response parameters at different monitoring times. The preset threshold is determined based on the allowable strain of the material, structural design standards, and historical monitoring data. Specifically, when the compensated structural strain distribution exceeds the allowable range, it is determined that the structure has an overall stress anomaly; when the local abnormal change rate exceeds the preset threshold, it is determined that the structure has local damage or interface anomalies; and when the compensated resistance-strain deviation exceeds the allowable range, it is determined that the structural cooperative stress performance has degraded.

[0017] Compared with the prior art, the advantages of the present invention are as follows: (1) The composite beam bridge truss reinforcement structure of the present invention is provided with a load-bearing crossbeam, multiple upper pads and multiple sets of force transmission diagonal bracing groups. The multiple sets of force transmission diagonal bracing groups are connected between the upper pads and the load-bearing crossbeam to form a composite truss force-bearing assembly. Its structure is compact and simple, and the force transmission diagonal bracing groups and the load-bearing crossbeam achieve coordinated force and deformation coordination through the division of labor in the force path, so as to effectively improve the lateral force performance of the composite beam bridge.

[0018] (2) The surface of the load-bearing beam is covered with carbon fiber fabric. The continuous carbon fibers of the carbon fiber fabric have a piezoresistive effect, that is, its resistance will change reversibly with the change of the strain of the material. The main force direction of the carbon fiber fabric is set along the axial direction of the load-bearing beam. Similarly, the sensing element arranged along the axial direction can directly obtain the main strain information, which improves the monitoring accuracy and data reliability.

[0019] Meanwhile, multiple sensing elements enable the carbon fiber fabric to achieve self-sensing monitoring of the structure through resistance changes during stress deformation. That is, the strain information of the carbon fiber fabric in the main stress direction is obtained through the carbon fiber resistance measurement channel, and the strain information in the main stress direction (i.e., the resistance measurement signal) is checked and compensated by the fiber optic grating sensor. Thus, by detecting the resistance change, the internal stress and strain state can be reflected in real time, and even the occurrence and expansion of damage can be identified. It does not require the implantation of additional fragile sensors, fundamentally solving the interface compatibility and durability problems, and realizing the safe and reliable monitoring of carbon fiber fabric in the load-bearing beam in an axially distributed, full-cycle manner.

[0020] (3) The monitoring method of the present invention can monitor the resistance change state and axial strain state of the GFRP beam in real time. At the same time, it can compensate for the resistance change rate and strain distribution data by using the deviation value of the theoretical resistance change value calculated by the real-time monitored axial strain and the real-time detected resistance change data. It can obtain accurate resistance change rate and strain distribution data in real time, and then judge the abnormal state of the structure based on the compensated resistance change rate and strain distribution data. It can identify the abnormal state of the bridge structure in a timely and accurate manner, and realize the long-term self-sensing monitoring and safety status assessment of the composite beam bridge reinforcement structure. Attached Figure Description

[0021] The invention will now be described in more detail with reference to embodiments and the accompanying drawings. Figure 1 This is a schematic diagram of the truss reinforcement structure for composite beam bridges of the present invention in a specific application; Figure 2 This is a structural schematic diagram of the truss reinforcement structure for composite beam bridges of the present invention; Figure 3 This is a top view of the truss reinforcement structure for composite beam bridges according to the present invention; Figure 4 This is a schematic diagram showing the positional relationship between the load-bearing crossbeam and the carbon fiber fabric of this invention; Figure 5 This is a schematic diagram showing the positional relationship between the copper electrode and the fiber optic grating sensor of the present invention; Figure 6 This is a flowchart of the bridge stress state monitoring method of the present invention; Figure 7 This is a comparison diagram of the lateral load distribution coefficient of the present invention and that of traditional composite trusses.

[0022] The labels in the diagram represent: 1. Load-bearing beam; 2. Connecting plate; 3. Upper pad; 4. Reinforcing diagonal brace; 5. Carbon fiber fabric; 6. Copper electrode; 7. Fiber grating sensor. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of protection of the present invention.

[0024] Figures 1 to 7 An embodiment of the truss reinforcement structure for composite beam bridges of the present invention is shown, comprising a load-bearing crossbeam 1, upper pads 3, and a force-transmitting diagonal brace assembly. The load-bearing crossbeam 1 bears the tensile force of the bridge and is connected to the bottom surface of adjacent main beams of the bridge. Multiple upper pads 3 are disposed on the lower surface of the wet joints of the composite beam bridge, and are horizontally spaced along the crossbeam. The force-transmitting diagonal brace assembly transfers the upper load of the bridge to the load-bearing crossbeam 1. Multiple sets of force-transmitting diagonal braces are connected between the upper pads 3 and the load-bearing crossbeam 1. Reinforcing diagonal braces 4 are correspondingly arranged with the upper pads 3 to form a truss load-bearing assembly that improves the lateral load-bearing performance of the composite beam bridge. Its structure is compact and simple, and through the division of labor between the force-transmitting diagonal brace assembly and the load-bearing crossbeam 1 in the force path, it achieves coordinated force distribution and deformation coordination, effectively improving the lateral load-bearing performance of the composite beam bridge.

[0025] The upper pad 3 is reliably fixed to the original beam bridge structure. When the beam bridge structure is subjected to load during service, the upper pad 3 acts as a load transfer component, introducing the upper load into the lower truss force assembly and distributing the load to the adjacent main beams. This enhances the cooperative force-bearing performance of the original composite beam bridge, improves the problem of poor lateral connection, and improves the overall integrity of the original structure.

[0026] The surface of the load-bearing beam 1 of the present invention is provided with carbon fiber fabric 5 with the main force direction along the axial direction of the beam. Multiple sensing elements are arranged at intervals along the axial direction at the interface between the carbon fiber fabric 5 and the load-bearing beam 1 to form a carbon fiber resistance measurement channel. A fiber optic grating sensor 7 is correspondingly arranged in the carbon fiber resistance measurement channel.

[0027] The surface of the load-bearing beam 1 is covered with carbon fiber fabric 5. The continuous carbon fibers of the carbon fiber fabric 5 have a piezoresistive effect, that is, its resistance will change reversibly with the change of the strain on the material. The main force direction of the carbon fiber fabric 5 is set along the axial direction of the load-bearing beam 1. Similarly, the sensing element arranged along the axial direction can directly obtain the main strain information, which improves the monitoring accuracy and data reliability.

[0028] Meanwhile, multiple sensing elements enable the carbon fiber fabric 5 to achieve self-sensing monitoring of the structure through resistance changes during deformation under stress. Specifically, the strain information of the carbon fiber fabric 5 in the main stress direction is obtained through the carbon fiber resistance measurement channel, and the strain information in the main stress direction (i.e., the resistance measurement signal) is checked and compensated by the fiber optic grating sensor 7. Thus, by detecting resistance changes, the internal stress and strain state can be reflected in real time, and even the occurrence and expansion of damage can be identified. It does not require the additional implantation of fragile sensors (such as strain gauges, displacement gauges, etc.), but utilizes the piezoresistive effect of the carbon fiber material itself to embed the sensing function into the structural material, avoiding the interface failure problem between the sensor and the structure. This fundamentally solves the interface compatibility and durability problems, and realizes the axial distributed, full-cycle safe and reliable monitoring of the carbon fiber fabric 5 in the load-bearing beam 1, improving the reliability and durability of the monitoring system in the long-term service environment of the bridge.

[0029] Furthermore, such as Figure 5 As shown, multiple sensing elements are spaced apart perpendicular to the length of the load-bearing beam, and fiber Bragg grating sensors 7 are arranged parallel to the length of the load-bearing beam. Multiple fiber Bragg grating sensors 7 located in the same carbon fiber resistance measurement channel are arranged parallel to the electrodes at intervals. This allows for more accurate and timely acquisition of strain information in the main stress direction of the carbon fiber fabric 5, thus better reflecting changes in the internal stress and strain state of the carbon fiber fabric 5. It enables multi-source fusion monitoring of electrical and optical signals, facilitating a comprehensive assessment of the stress state, deformation development, and potential damage of composite truss components, thereby constructing an integrated "reinforcement-monitoring-early warning" reinforcement system.

[0030] In this embodiment, the sensing element is a copper electrode 6.

[0031] Furthermore, the carbon fibers inside the carbon fiber fabric 5 are arranged parallel to each other along the axial direction of the beam to form a continuous unidirectional fiber fabric. This continuous unidirectional fiber fabric, after being prestressed, is bonded to the surface of the load-bearing beam 1 to form a continuous bonding layer. This continuous bonding layer has the ability to transfer interfacial shear force and coordinate deformation, thereby achieving strain coordination and synergistic stress distribution between the carbon fiber fabric 5 and the load-bearing beam 1, improving the problem of weak lateral connections, and optimizing lateral force transmission and overall stress state. Prestress is applied to the carbon fiber fabric 5 during the reinforcement construction process, allowing it to participate in stress distribution from the early stages of structural service, thus improving the overall stiffness and crack control capability of the composite truss beam.

[0032] When the structure deforms under load, the resistance value of the carbon fiber fabric 5 changes reversibly with its axial strain, thereby enabling real-time sensing of the stress state of the composite truss beam.

[0033] Carbon fiber fabric 5 serves as both a structural reinforcement component and a self-sensing monitoring component. In other words, carbon fiber fabric 5 acts as both a load-bearing component and a sensing carrier. Its resistance change can reflect the stress and deformation state of the composite truss beam. Through the resistance-strain coupling characteristics, the reinforced structure and the structural detection system are integrated, thereby realizing the self-sensing monitoring of the reinforced structure.

[0034] Preferably, the carbon fiber fabric 5 is bonded to the load-bearing beam 1 using an epoxy-based adhesive, and the epoxy-based adhesive forms a continuous adhesive layer between the two. The sensing element is disposed at the bonding interface between the load-bearing beam 1 and the carbon fiber fabric 5.

[0035] In this embodiment, the load-bearing beam 1 is a fiberglass beam; the reinforcing brace 4 is a steel-concrete composite brace, that is, the reinforcing brace 4 is composed of an outer steel pipe and an inner filling concrete. Preferably, the reinforcing brace 4 uses micro-expansion self-compacting high-performance concrete as the inner filling material of the steel pipe. The combined effect of the steel pipe and the inner filling concrete gives the reinforcing brace 4 the advantages of high load-bearing capacity and stability, and can effectively transfer the load from the upper pad 3 downward.

[0036] The combination of fiberglass beams and steel-concrete composite bracing allows the truss load-bearing components to overcome the limitations of metallic materials, achieving superior reinforcement effects. This enables both health monitoring and improved structural load-bearing capacity. Furthermore, by optimizing the material distribution and structural form of the truss load-bearing components, material usage and structural weight are minimized while ensuring safe use. Simultaneously, axial strain data of the beams is collected and transmitted to a back-end analysis system for structural health assessment and early warning. This achieves lightweighting while constructing an integrated reinforcement-monitoring system.

[0037] Meanwhile, fiberglass beams possess high specific strength, excellent fatigue resistance, and a low coefficient of thermal expansion, effectively avoiding the fatigue and temperature sensitivity issues inherent in existing steel materials. Furthermore, they exhibit superior corrosion resistance, enabling them to withstand corrosion in harsh environments and achieving efficient, durable, and lightweight reinforcement of beam bridges. Therefore, this invention achieves lightweighting of the reinforcement system itself and synergistically integrates structural reinforcement and self-sensing detection.

[0038] In this embodiment, the load-bearing crossbeam 1 is connected to the bottom surface of the adjacent main beam via a connecting plate 2. First bolt holes are symmetrically arranged on both sides of the connecting plate 2 along the length of the load-bearing crossbeam 1. Each group of first bolt holes is evenly spaced along the length of the bottom of the beam bridge. These first bolt holes are used for bolting the connecting plate 2 to the bottom surface of the main beam of the beam bridge. The lower part of the upper pad 3 is welded to the reinforcing diagonal brace 4. Second bolt holes are symmetrically arranged on both sides of the upper pad 3 along the length of the load-bearing crossbeam 1. Each group of second bolt holes is evenly spaced along the length of the bottom of the beam bridge. These second bolt holes are used for bolting the upper pad 3 to the wet joint of the beam bridge.

[0039] In this embodiment, the force transmission diagonal bracing group is arranged in a V-shape symmetrically between the load-bearing crossbeam 1 and the upper pad 3.

[0040] In this embodiment, when the beam bridge is subjected to load, the connecting plate 2 and the upper pad plate 3 will transfer the load to the load-bearing crossbeam 1 at the bottom, and finally distribute the load to the adjacent main beams. This enhances the cooperative stress performance of the original composite beam bridge, improves the problem of poor lateral connection, and improves the overall integrity of the original structure. It can effectively improve the lateral connection and stress state of the composite beam bridge, make the main beams of the composite beam bridge tend to cooperate in stress, and improve the overall integrity and load-bearing capacity.

[0041] When the composite beam bridge deforms under load, the load-bearing beam 1 generates axial strain. This strain is transmitted to the carbon fiber fabric 5 through interfacial shear, causing changes in the internal conductive pathways of the carbon fibers. The resistance value of the carbon fiber fabric changes regularly with the magnitude of the strain. By collecting and analyzing the resistance changes of the carbon fiber fabric 5, the stress state and deformation development trend of the composite truss beam can be inverted.

[0042] This embodiment further provides a method for monitoring the stress state of bridges based on the aforementioned composite beam bridge truss reinforcement structure, such as... Figure 6 As shown, it includes the following steps: Step 1) Determine the arrangement position of the composite truss and the installation hole positions of the connecting plate 2 and the upper pad 3. Fix the connecting plate 2 to the bottom surface of the main beam and the upper pad 3 to the bottom surface of the wet joint according to the installation hole positions. Connect the CFST diagonal brace 4 between the upper pad 3 and the GFRP beam 1 so that the CFST diagonal brace 4 forms a truss force system. The CFST diagonal brace 4 is arranged in a V-shape symmetrical arrangement to realize the transverse load transfer and structural collaborative force bearing. Step 2) Continuous unidirectional carbon fiber fabric 5 is pasted axially on the surface of GFRP beam 1 so that carbon fiber fabric 5 and GFRP beam 1 form a cooperative force-bearing component. Step 3) Install resistance measurement channels on the bridge to collect resistance change data ΔR of carbon fiber fabric 5 along the fiber direction, and measure the axial strain of GFRP beam 1 by fiber optic grating sensor 7 installed in the corresponding stress area. Step 4): Calculate the theoretical resistance change value based on the axial strain measured by fiber Bragg grating sensor 7. The theoretical resistance change value With resistance change data obtained from real-time monitoring The deviation value is obtained by comparison. Based on the deviation value, the resistance change rate and strain distribution data are compensated to obtain the compensated resistance change rate and strain distribution data. Step 5): Extract structural response parameters based on the compensated resistance change rate and strain distribution data, and determine whether the structure is in an abnormal state based on the extracted structural response parameters.

[0043] In this embodiment, step 1) may specifically include the following steps: Step 1.1) Monitor and evaluate the composite beam bridge to be reinforced. Determine the arrangement position and spacing of the composite truss based on the main beam spacing, wet joint location and lateral stress performance, and determine the installation hole positions of the connecting plate 2 and the upper pad plate 3. Step 1.2): Lay out and drill holes on the bottom surface of the main beam and the bottom surface of the wet joint according to the determined installation hole positions; Step 1.3) Roughen the bottom surface of the main beam and the bottom surface of the wet joint, and apply structural adhesive to the surface to improve the bonding performance of the connection interface; Step 1.4) Fix the connecting plate 2 to the bottom surface of the main beam with bolts, and fix the upper pad 3 to the bottom surface of the wet joint; Step 1.5) Connect the CFST diagonal brace 4 between the upper pad 3 and the GFRP beam 1, so that the CFST diagonal brace 4 is arranged in a V-shape to form a composite truss force system.

[0044] In this embodiment, in step 2), when the continuous unidirectional carbon fiber fabric 5 is pasted axially on the surface of the GFRP beam 1, an epoxy-based adhesive is used to form a bonding interface that can transmit interfacial shear force, so that the carbon fiber fabric 5 and the GFRP beam 1 form a co-force-bearing component.

[0045] In this embodiment, in step 3), multiple sets of resistance measurement channels and fiber optic grating sensors 7 are set along the length of the beam to form a monitoring unit, thereby achieving multi-point synchronous monitoring. The resistance measurement channels can be made of copper electrodes to collect the resistance change data ΔR of the carbon fiber fabric 5 along the fiber direction during the use of the bridge structure. Correspondingly, the axial strain of the GFRP beam 1 is simultaneously measured by the fiber optic grating sensors 7 deployed in the corresponding stress area, so that the resistance change state and axial strain state of the GFRP beam 1 can be monitored in real time.

[0046] In this embodiment, step 4) involves the following specific steps for calculating the theoretical resistance change: First, based on the relationship between the resistance change of carbon fiber fabric and the axial strain of GFRP beam, a resistance-strain coupling model is established: (1) in, The initial resistance, This is the change in resistance. The parameter is the rate of change of resistance. Let be the axial strain of GFRP beam 1.

[0047] Since the carbon fiber fabric and the GFRP beam 1 form a cooperative stress relationship through the bonding interface, under the condition of reliable interface bonding, the strain of the carbon fiber fabric is approximately consistent with the axial strain of the GFRP beam 1. Therefore, the axial strain measured by the fiber optic grating sensor 7 is... As axial strain The measured value, i.e. The actual axial strain data of the GFRP beam 1 measured by the fiber optic grating sensor 7 at the corresponding monitoring position is used as the benchmark value of the true strain of the structure, and the theoretical resistance change value is calculated. ; Axial strain measured based on fiber optic grating sensor (7) And the theoretical resistance change value calculated by the above resistance-strain coupling model: (2) in, This represents the theoretical change in resistance.

[0048] Further, the theoretical resistance change value With resistance change data obtained from real-time monitoring By comparing the results, the deviation values ​​were obtained: (3) The resistance change rate and strain distribution data are compensated based on the deviation value.

[0049] In this embodiment, compensation processing is performed on the resistance change rate and strain distribution data based on the deviation value, specifically including: If the deviation is within the preset allowable range, the least squares method is used to fit the resistance change rate data at each measuring point to obtain the compensated resistance change rate distribution function: (4) Where X is the position coordinate along the length of GFRP beam 1. The initial resistance, This is the change in resistance. Let n be the resistance change rate parameter of the k-th monitoring point, where k is the index of the monitoring point and n is the number of monitoring points.

[0050] The compensated strain distribution data are calculated based on the compensated resistance change rate. (5) in, This is the resistance change rate parameter.

[0051] When the deviation exceeds the preset allowable range, temperature correction is applied to the strain data based on the temperature-sensitive characteristics of the fiber Bragg grating sensor, reducing the impact of environmental factors on the monitoring results. Since the strain data measured by the fiber Bragg grating sensor includes both mechanical strain caused by structural stress and temperature strain caused by changes in ambient temperature, the temperature change data of the monitoring area is used as a basis for temperature correction. and temperature sensitivity coefficient Modify the data according to the actual strain to obtain the temperature-compensated mechanical strain: (6) in The axial strain, i.e. the total strain, of the GFRP beam (1) measured by the fiber optic grating sensor is given. For temperature sensitivity coefficient, For temperature change data, This refers to the compensated mechanical strain.

[0052] Based on compensated mechanical strain Recalculate the theoretical resistance change: (7) in, This represents the theoretical resistance change after compensation.

[0053] Based on the difference between the theoretical resistance changes before and after temperature compensation, determine the correction amount for the resistance change caused by temperature effects: (8) in This is the resistance correction amount caused by temperature changes.

[0054] The resistance change data obtained from real-time monitoring Subtracting the temperature correction, we obtain the corrected resistance change data: (9) And calculate the corrected rate of change of resistance: (10) Based on the corrected resistance change rate data, the distribution function was refitted and strain inversion was performed to reduce the impact of environmental temperature changes on the monitoring results.

[0055] The above compensation process can reduce the impact of environmental factors, local interface fluctuations, and measurement errors on monitoring results, and improve the consistency and stability of resistance change rate and strain distribution data.

[0056] In this example, structural response parameters are extracted based on the compensated resistance change rate data and compensated strain distribution data obtained in step 4). The structural response parameters include the compensated structural strain distribution, beam deformation development trend, resistance-strain deviation, and local abnormal change rate.

[0057] Specifically, the compensated structural strain distribution can be obtained by fitting the compensated resistance change rate data at different monitoring points. For example, the compensated structural strain distribution can be expressed as: (11) In the formula, This represents the axial strain at position x after compensation. Let x be the rate of change of resistance after compensation. This is the resistance change rate parameter.

[0058] The beam deformation development trend is based on the compensated strain distribution data. The variation pattern along the length of the GFRP beam (1) is determined. Specifically, multiple monitoring points can be selected along the length of the GFRP beam (1). The compensated axial strain at each monitoring point was obtained. Furthermore, the strain change rate between adjacent monitoring points is used as an indicator of deformation development; for example, the calculation expression can be expressed as: (12) in, Let be the strain change rate of the i-th monitoring segment. When the strain change rate of a certain segment is... When the gradient continuously increases or exceeds the preset threshold, it is determined that there is a local abnormal stress trend in that section; when the gradient of each section... When the distribution is gradual and does not exceed the threshold, the deformation trend of the beam is considered to be stable.

[0059] The resistance-strain deviation can be specifically calculated based on the compensated measured resistance change and the steadily compensated theoretical resistance change: (13) in, The compensated resistance-strain deviation, This is the corrected resistance change data. This represents the theoretical resistance change after temperature compensation.

[0060] The rate of local anomaly is determined by the difference in resistance change rates after compensation at adjacent monitoring points, or by the degree of abrupt change. For example, the degree of abrupt change can be calculated using the following formula: (14) when If the preset mutation threshold is exceeded, it is determined that there is local damage or interface abnormality in the corresponding section.

[0061] Based on the compensated structural strain distribution, resistance-strain deviation, and local abnormal change rate, the structural stress state is comprehensively determined. Specifically, the overall structural stress state can be judged based on the compensated structural strain distribution; the beam deformation development trend is determined based on the variation law of the compensated strain distribution along the beam length; local damage or interface anomalies can be identified based on the local abnormal change rate; and the cooperative stress performance state is evaluated based on the compensated resistance-strain deviation. The preset threshold can be determined based on the material's allowable strain, structural design standards, finite element results, experimental data, and historical monitoring data.

[0062] Specifically, determining whether a structure is in an abnormal state based on the extracted structural response parameters includes: comparing the structural response parameters with preset thresholds; when the compensated structural strain distribution exceeds the allowable range, it is determined that the structure has an overall stress anomaly; when the local abnormal change rate exceeds the preset threshold, it is determined that the structure has local damage or interface anomalies; when the compensated resistance-strain deviation exceeds the allowable range, it is determined that the structure's cooperative stress performance has degraded. Furthermore, while identifying abnormal states, the abnormal region can be determined by combining the monitoring locations corresponding to the abnormal parameters, and the development trend of the structural stress state can be analyzed based on the changing patterns of the structural response parameters at different monitoring times. Corresponding structural state assessment results and early warning information are then output, thereby achieving long-term self-sensing monitoring and safety assessment of the composite beam bridge reinforcement.

[0063] This invention achieves multi-source fusion analysis of monitoring data through cross-validation of resistance signals, fiber optic strain signals, and temperature information. First, the theoretical resistance change is calculated based on the strain data measured by the fiber optic grating sensor, and the deviation is obtained by comparing it with the measured resistance. Second, the temperature-sensitive characteristics of the fiber optic grating sensor are used to decouple the measured strain from temperature, thereby distinguishing the effects of structural stress changes and environmental temperature changes. Furthermore, through consistency error and rate of change analysis, the monitoring signals are classified and discriminated, enabling the differentiation and identification of structural stress state, environmental influences, and interface damage.

[0064] like Figure 7 As shown, a comparative analysis is conducted on the lateral load distribution factor (LDF) of an unreinforced box girder bridge, a box girder bridge reinforced with a CFST frame, and a box girder bridge reinforced with the composite truss of this invention under the same load conditions. The results show that: In the unreinforced state, the LDF values ​​of each main beam are generally large, and there are significant differences between different main beams, indicating that the vehicle load is mainly concentrated in local main beams, the lateral distribution capacity is weak, and the overall structure is poor.

[0065] After reinforcement with the CFST frame, the LDF values ​​at each measuring point were lower than those in the unreinforced state, indicating that the lateral load distribution capacity was improved to a certain extent. However, there were still some differences between different main beams, indicating that although the reinforcement method improved the overall stiffness, it had limited improvement on the lateral coordinated deformation capacity.

[0066] After reinforcement using the composite truss of this invention, the LDF values ​​at each measuring point were significantly reduced, and the LDF distribution among different main beams was more uniform, indicating that the lateral load could be more rationally distributed among the main beams, and the lateral connectivity of the structure was significantly improved. Further analysis of the data at each measuring point showed that the LDF reduction of the present invention was more significant at the main beams near the loading position, while the LDF of the main beams farther from the loading position increased, indicating that the load distribution changed from concentrated distribution to collaborative sharing among multiple beams, demonstrating better lateral force transmission performance. At the same time, the LDF change curves at each measuring point were flatter, indicating that the stress distribution of the structure tended to be uniform, effectively reducing the phenomenon of local stress concentration. Compared with the traditional CFST frame reinforcement, the present invention forms a composite truss system through GFRP beams and CFST diagonal braces, which introduces a certain deformation coordination capability while ensuring overall stiffness, and can form a multi-path force transmission mechanism, so that the lateral load is distributed stepwise among the main beams, thereby significantly improving the lateral stress performance. Therefore, this invention can not only effectively reduce the lateral load distribution coefficient, but also improve its distribution uniformity, realizing the transformation from "local stress" to "overall coordinated stress", thereby significantly improving the lateral connection performance and structural safety of composite beam bridges.

[0067] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A truss reinforcement structure for composite beam bridges, characterized in that, The structure includes a load-bearing crossbeam connected to the bottom surface of adjacent main beams of the beam bridge, multiple upper pads disposed on the lower surface of the wet joint of the composite beam bridge, and multiple sets of force-transmitting diagonal braces connected between the upper pads and the load-bearing crossbeams. The multiple upper pads are horizontally spaced along the load-bearing crossbeams, and the reinforcing diagonal braces are correspondingly disposed with the upper pads to form a truss load-bearing assembly that improves the lateral force performance of the composite beam bridge. The surface of the load-bearing crossbeam is provided with carbon fiber fabric with the main force direction along the axial direction of the load-bearing crossbeam. Multiple sensing elements are spaced along the axial direction at the interface between the carbon fiber fabric and the load-bearing crossbeam to form a carbon fiber resistance measurement channel. The carbon fiber resistance measurement channel is equipped with a fiber optic grating sensor.

2. The truss reinforcement structure for composite beam bridges according to claim 1, characterized in that, Multiple sensing elements are spaced apart perpendicular to the length direction of the load-bearing beam, and fiber Bragg grating sensors are arranged parallel to the length direction of the load-bearing beam. Multiple fiber Bragg grating sensors located in the same carbon fiber resistance measurement channel are arranged parallel to the electrodes.

3. The truss reinforcement structure for composite beam bridges according to claim 1, characterized in that, The carbon fibers inside the carbon fiber fabric are arranged parallel to each other along the axial direction of the load-bearing beam to form a continuous unidirectional fiber fabric. The continuous unidirectional fiber fabric is bonded to the surface of the load-bearing beam to form a continuous adhesive layer with interfacial shear force transmission and deformation coordination capabilities.

4. The truss reinforcement structure for composite beam bridges according to any one of claims 1 to 3, characterized in that, The load-bearing beam is a glass fiber beam to achieve structural lightweighting, and the reinforcing diagonal brace is a steel tube concrete diagonal brace.

5. The truss reinforcement structure for composite beam bridges according to any one of claims 1 to 3, characterized in that, The load-bearing crossbeam is connected to the bottom surface of the adjacent main beam via a connecting plate. The connecting plate has first bolt holes symmetrically distributed on both sides along the length of the load-bearing crossbeam. Each group of first bolt holes is evenly distributed along the length of the bottom of the beam bridge. The first bolt holes are used for bolting the connecting plate to the bottom surface of the main beam of the beam bridge. The upper pad has second bolt holes symmetrically distributed on both sides along the length of the load-bearing crossbeam. Each group of second bolt holes is evenly distributed along the length of the bottom of the beam bridge. The second bolt holes are used for bolting the upper pad to the wet joint of the beam bridge.

6. A method for monitoring the stress state of bridges based on truss reinforcement structures for composite beam bridges, characterized in that, Includes the following steps: Step 1) Determine the arrangement position of the composite truss and the mounting hole positions of the connecting plate and the upper pad. Fix the connecting plate to the bottom surface of the main beam and the upper pad to the bottom surface of the wet joint according to the mounting hole positions. Connect the CFST diagonal brace between the upper pad and the GFRP crossbeam so that the CFST diagonal brace is arranged in a V-shape to form a composite truss force system. Step 2) Continuous unidirectional carbon fiber fabric is bonded along the axial direction on the surface of the GFRP beam so that the carbon fiber fabric and the GFRP beam form a cooperative force-bearing component. Step 3) Install resistance measurement channels on the bridge to collect resistance change data ΔR at multiple monitoring points along the fiber direction on the carbon fiber fabric, and measure the axial strain of the GFRP beam by using fiber optic grating sensors installed in the corresponding stress areas. Step 4) Calculate the theoretical resistance change value based on the axial strain measured by the fiber optic grating sensor, and compare it with the resistance change data ΔR to obtain the deviation value. Then, perform compensation processing on the resistance change rate and strain distribution data based on the deviation value to obtain the compensated resistance change rate and strain distribution data. Step 5): Extract structural response parameters based on the compensated resistance change rate and strain distribution data, and determine whether the structure is in an abnormal state based on the extracted structural response parameters.

7. The method for monitoring the stress state of a bridge according to claim 6, characterized in that, In step 4), the calculation expression for the theoretical resistance change value based on the axial strain measured by the fiber Bragg grating sensor is as follows: in, This is the theoretical resistance change value. The initial resistance, The parameter is the rate of change of resistance. The axial strain of the GFRP beam is measured by a fiber Bragg grating sensor.

8. The method for monitoring the stress state of a bridge according to claim 6, characterized in that, Step 4) involves compensating the resistance change rate and strain distribution data based on the deviation value, including: If the deviation value is within the preset allowable range, the least squares method is used to fit the resistance change data ΔR at each monitoring point to obtain the compensated resistance change rate distribution function: Where x is the position coordinate along the length of the GFRP beam. Let x be the rate of change of resistance after compensation. The initial resistance, Let n be the resistance change rate parameter of the k-th monitoring point, where k is the index of the monitoring point and n is the number of monitoring points. The compensated strain distribution data are calculated based on the compensated resistance change rate distribution function: in, This represents the axial strain at position x after compensation. The rate of change of resistance; If the deviation value exceeds the preset allowable range, based on the temperature change data of the monitored area... Temperature sensitivity coefficient Temperature compensation is applied to the actual measured axial strain data to obtain the temperature-compensated mechanical strain. Based on the temperature-compensated mechanical strain... Recalculate the theoretical resistance change value ,in, To determine the corrected theoretical resistance change value, the resistance change correction amount caused by temperature influence is determined based on the difference between the theoretical resistance change values ​​before and after compensation. This correction amount is then used to correct the resistance change rate data obtained from real-time monitoring.

9. The method for monitoring the stress state of a bridge according to claim 8, characterized in that, Based on temperature change data in the monitored area Temperature sensitivity coefficient Temperature compensation is performed on the measured axial strain data to obtain the temperature-compensated mechanical strain. The calculation expression is: in, The axial strain of the GFRP beam measured by the fiber Bragg grating sensor; The calculation expression for the correction amount of the resistance change caused by the temperature effect is as follows: in, This is the resistance correction amount caused by temperature changes. This represents the theoretical change in resistance. The calculation expression for correcting the resistance change rate data obtained from real-time monitoring using the aforementioned resistance change correction amount is as follows: in, This is the corrected rate of change of resistance. This is the corrected resistance change data. This is to obtain the resistance change rate data in real time.

10. The method for monitoring the stress state of a bridge according to any one of claims 6 to 9, characterized in that, In step 5), the structural response parameters include the compensated structural strain distribution, the beam deformation development trend, the resistance-strain deviation, and the local abnormal change rate; wherein, the compensated structural strain distribution is obtained by fitting the compensated resistance change rate data based on different monitoring points, the beam deformation development trend is determined based on the change state of the compensated axial strain at multiple monitoring points along the beam length direction, the resistance-strain deviation is calculated by the difference between the theoretical resistance change value and the measured resistance change value, and the local abnormal change rate is the difference or abrupt change value of the compensated resistance change rate at adjacent monitoring points; The step of determining whether a structure is in an abnormal state based on the extracted structural response parameters includes: comparing the structural response parameters with a preset threshold; when the structural response parameters exceed the corresponding preset threshold, outputting a structural anomaly warning message and the corresponding anomaly location; and obtaining the development trend of the structural stress state based on the changes in the structural response parameters at different monitoring times. The preset threshold is determined based on the allowable strain of the material, structural design standards, and historical monitoring data. Specifically, when the compensated structural strain distribution exceeds the allowable range, it is determined that the structure has an overall stress anomaly; when the local abnormal change rate exceeds the preset threshold, it is determined that the structure has local damage or interface anomalies; and when the compensated resistance-strain deviation exceeds the allowable range, it is determined that the structural cooperative stress performance has degraded.

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