Monitoring and early warning method and system for safety of large-span prefabricated box girder transportation structure

Abstract

The invention relates to the technical field of bridge construction monitoring, in particular to a safety monitoring and early warning method and system for a large-span prefabricated box girder transportation structure, and the method comprises the following steps: selecting four-point plane torsion resistance and structural stress as safety monitoring parameters of a large-span prefabricated box girder; a finite element model is adopted for analysis and calculation to obtain a control value of the four-point plane torsion resistance and a control value of the structural stress; and according to the control value of the four-point plane torsion resistance, the control value of the structural stress and the early warning range, the safety risk level of the large-span prefabricated box girder transportation structure is obtained. According to the method, calculation is carried out according to the newly set parameter four-point plane torsion degree, the structural safety risk level representing whether the large-span prefabricated box girder is cracked or not in the transportation process is obtained, and risks can be eliminated in time.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction, and in particular to a monitoring and early warning method and system for the safety of a large-span prefabricated box girder structure. Background Art

[0002] According to the current industry standards, bridges can be divided into super-large bridges, large bridges, medium bridges, small bridges and culverts, which are classified based on the total length of the multi-hole span and the single-hole span of the bridge. Among them, bridges with a total length of multi-hole span of 100 meters or more and a single-hole span of 40 meters or more are classified as long-span bridges.

[0003] At present, during the transportation process, the long-span prefabricated box girders are placed on the transportation equipment in the form of multi-point support. Factors such as asynchronous operation of the equipment, uneven ground, and time required for the hydraulic system to adapt to deformation will cause the stress and posture of the long-span prefabricated box girder structure to change, ultimately causing the risk of cracking of the box girder concrete. Concrete cracking has an adverse effect on the durability of the long-span prefabricated box girder, and thus affects the long-term performance and structural safety of the bridge.

[0004] At present, the construction control of prefabricated box girders generally uses stress and deformation as key monitoring parameters. Although stress and deformation can reflect the stress and deformation of the key sections of the box girder, they cannot guide the rapid decision-making of process adjustment when an early warning occurs, affecting the construction progress. The core problem of large concrete box girder transportation is the boundary support problem. Controlling the impact of boundary support changes on the beam body is the key to the safety of concrete box girder transportation structure. Summary of the invention

[0005] The purpose of the present invention is to provide a monitoring and early warning method and system for the safety of large-span prefabricated box girder transportation structure, to achieve the evaluation of the safety risk level of the large-span prefabricated box girder structure, and to provide decision support for rapid process adjustment, thereby solving the problem of easy cracking of large-span prefabricated box girders during transportation.

[0006] In order to achieve the purpose of the above invention, the present invention provides the following technical solutions: A monitoring and early warning method for the safety of a large-span prefabricated box girder transportation structure comprises the following steps: S1. Select four-point plane distortion and structural stress as the safety monitoring parameters of long-span prefabricated box girders; The step of obtaining the four-point plane distortion comprises: regarding the positions of the four corner points of the bottom plate of the long-span prefabricated box girder in the initial state as the zero-point positions of the elevation of the four corner points; Recording the relative elevation values ​​of the four corner points relative to the elevation zero point during the transportation of the long-span prefabricated box girder, adding the relative elevation values ​​of the diagonal corner points among the four corner points to obtain the sum of the relative elevation values ​​of the two groups of diagonal corner points; Calculate the absolute value of the difference between the sum of the relative elevation values ​​of the two sets of diagonal corner points, where the absolute value is the four-point plane distortion; S2, using a finite element model to analyze and calculate the maximum allowable value of the four-point plane distortion; using the maximum allowable value of the four-point plane distortion as the control value of the four-point plane distortion; S3, using a finite element model to analyze and calculate the initial structural stress at each key test point in the initial state of the long-span prefabricated box girder, and calculating the maximum allowable change value of the structural stress based on the initial structural stress; and using the maximum allowable change value as the control value of the structural stress; S4. Obtain the safety risk level of the large-span prefabricated box girder transportation structure according to the control value of the four-point plane distortion, the control value of the structural stress and the warning range.

[0007] Preferably, in step S4, the warning range includes a four-point plane distortion warning range and a structural stress warning range; The step of dividing the four-point plane distortion warning range includes: multiplying the control value of the four-point plane distortion by three different four-point plane distortion reduction coefficients to obtain three different four-point plane distortion warning values; The three different four-point plane distortion warning values ​​are set in descending order as the level I warning value, level II warning value, and level III warning value of the four-point plane distortion; The step of dividing the structural stress warning range includes: multiplying the control value of the structural stress by three different structural stress reduction coefficients to obtain three different structural stress warning values; setting the three different structural stress warning values ​​in order from large to small as level I warning value, level II warning value, and level III warning value of the structural stress.

[0008] Preferably, an early warning mechanism is established according to the early warning values ​​of the four-point plane distortion and the early warning values ​​of the structural stress; The early warning mechanism includes: issuing an early warning when any of the monitoring values ​​of the four-point plane distortion or the monitoring values ​​of the structural stress exceeds the respective early warning values; The monitoring value of the four-point plane distortion is the four-point plane distortion obtained in real time during the transportation of the long-span prefabricated box girder; The monitoring value of the structural stress is a change value of the structural stress obtained in real time during the transportation of the long-span prefabricated box girder relative to the structural stress in the initial state of the long-span prefabricated box girder.

[0009] Preferably, an early warning level is established according to the early warning mechanism, and if the early warning level is level I warning or the structural stress early warning level is level I warning, then the monitoring result is level I warning; If the warning level is level II warning or the structural stress warning level is level II warning, the monitoring result is level II warning; If the warning level is level III warning or the structural stress warning level is level III warning, the monitoring result is level III warning.

[0010] Preferably, the safety risk level of the large-span prefabricated box girder transportation structure is obtained according to the warning level; The safety risk levels of the large-span prefabricated box girder transportation structure include: When there is no warning, the safety risk level of the large-span prefabricated box girder transportation structure is at a low risk level; In the case of level I warning, the safety risk level of the large-span prefabricated box girder transportation structure is at a medium risk level; When the warning level is II, the safety risk level of the large-span prefabricated box girder transportation structure is at a high risk level; During the Level III warning, the safety risk level of the large-span prefabricated box girder transportation structure is at an extremely high risk level.

[0011] Preferably, the process is adjusted according to the safety risk level of the large-span prefabricated box girder transportation structure.

[0012] A monitoring and early warning system for the safety of large-span prefabricated box girder transportation structures, comprising: Sensors, used to collect relative elevation values ​​and structural stresses of four corner points of the long-span prefabricated box girder; A collector, connected to the sensor for collecting data from the sensor; The monitoring system obtains the safety risk level of the large-span prefabricated box girder transportation structure based on the control value of the four-point plane distortion, the control value of the structural stress and the early warning range.

[0013] Preferably, the sensor includes a displacement sensor and a stress sensor; The displacement sensor adopts a static level to obtain the relative elevation values ​​of the four corner points of the long-span prefabricated box girder; The stress sensor is used to obtain the structural stress of the long-span prefabricated box girder.

[0014] Preferably, it also includes an audible and visual alarm component for audible and visual alarm of the risk level of the large-span prefabricated box girder transportation structure.

[0015] Preferably, it also includes an adjusting component for adjusting the process of the large-span prefabricated box girder transportation structure in real time.

[0016] Compared with the prior art, the present invention has the following beneficial effects: the present invention selects four-point plane distortion and structural stress as monitoring parameters, and obtains the safety risk level of the large-span prefabricated box girder transportation structure according to the control value of the four-point plane distortion, the control value of the structural stress and the early warning range; and provides process adjustment according to the safety risk level of the large-span prefabricated box girder transportation structure, effectively reducing the risk of cracking of the large-span prefabricated box girder during transportation, eliminating safety hazards and preventing accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of a monitoring and early warning method for the safety of large-span prefabricated box girder transportation structures; Figure 2 This is a schematic diagram of the large-span prefabricated box girder transportation structure of Example 1 of the present invention: Figure 3 Schematic diagram of the four-point plane distortion of the long-span prefabricated box girder in Example 1 of the present invention; Figure 4 Schematic diagram of a SPMT vehicle transporting a large-span prefabricated box girder according to Embodiment 1 of the present invention; Figure 5 It is a finite element model of the transportation of the large-span prefabricated box girder according to the first embodiment of the present invention; Figure 6 Schematic diagram of a monitoring and early warning system for the safety of a large-span prefabricated box girder transportation structure according to Embodiment 2 of the present invention; Figure 7 is a schematic diagram of the installation of a static level according to Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the installation of the stress sensor of Example 2 of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with test examples and specific implementation methods. However, this should not be understood as the scope of the above-mentioned subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0019] Example 1 This embodiment provides a monitoring and early warning method for safety control of a large-span prefabricated box girder transportation structure, the method comprising the following steps: like Figure 1 As shown, S1, four-point plane distortion and structural stress are selected as the safety monitoring parameters of the long-span prefabricated box girder; The advantage of using the four-point plane distortion as a monitoring parameter for the safety of the large-span prefabricated box girder transportation structure is that it can characterize the torsion condition of the large-span prefabricated box girder and guide the adjustment of the process; the structural stress can intuitively reflect the stress condition of the key section of the large-span prefabricated box girder, and thus the structural stress is used as another monitoring parameter for the safety of the large-span prefabricated box girder transportation structure.

[0020] The state of the long-span prefabricated box girder before transportation is taken as the initial state of the long-span prefabricated box girder, such as Figure 2 As shown, the long-span prefabricated box girder 1 is placed on the transportation equipment through the support beam 2, and the state of the long-span prefabricated box girder at this time is taken as the initial state of the long-span prefabricated box girder.

[0021] The plane formed by the four corner points of the bottom plate of the large-span prefabricated box girder is used as the four-point plane of the large-span prefabricated box girder. During the transportation of the large-span prefabricated box girder, the elevations of the four corner points will change. At this time, the spatial relationship of the four corner points can be divided into two situations: first, any three corner points form a plane, and the remaining corner point is also in the plane; second, any three corner points form a plane, and the remaining corner point is not in the plane.

[0022] like Figure 3 As shown, when the four-point plane is in the state shown in 5, that is, when the spatial relationship of the four corner points is the first case, the large-span prefabricated box girder does not produce torsion; when the four-point plane is in the state shown in 6, that is, when the spatial relationship of the four corner points is the second case, the large-span prefabricated box girder produces torsion, and the torsion is not conducive to the stress safety of the large-span prefabricated box girder, so the four-point plane distortion is introduced to characterize the torsion of the large-span prefabricated box girder.

[0023] The step of obtaining the four-point plane distortion comprises: regarding the positions of the four corner points of the bottom plate of the long-span prefabricated box girder in the initial state as the zero-point positions of the elevation of the four corner points; recording the relative elevation values ​​of the four corner points relative to the zero-point position during the transportation of the long-span prefabricated box girder, adding the relative elevation values ​​of the diagonal corner points of the four corner points to obtain the sum of the relative elevation values ​​of the two groups of diagonal corner points; calculating the absolute value of the difference between the sum of the relative elevation values ​​of the two groups of diagonal corner points, and the absolute value is the four-point plane distortion; Figure 4 As shown in the figure, the relative elevation values ​​of the four corner points of the long-span prefabricated box girder, corner point 1, corner point 2, corner point 3, and corner point 4 are Δ1, Δ2, Δ3, and Δ4 respectively, so the plane distortion of the four points is |(Δ1+Δ3)-(Δ2+Δ4)|.

[0024] The four-point plane distortion can guide the adjustment of the process, and the process adjustment includes: lowering the highest corner point or raising the lowest corner point through the process, and the height adjustment amount is the four-point plane distortion; Figure 4 As shown, assuming that the relative elevation values ​​of the four corner points, corner point 1, corner point 2, corner point 3, and corner point 4 are 5mm, -2mm, 4mm, and 1mm respectively, the distortion of the four-point plane is 10mm. By lowering corner point 1 or raising corner point 2, the adjustment amount is less than or equal to 10mm.

[0025] The structural stress can directly reflect the stress condition of the key section of the long-span prefabricated box girder, such as Figure 2 As shown, the long-span prefabricated box girder 1 has a negative bending moment at the support beam 2, so the section at the support beam 2 is used as the key test section for structural stress, and the risk of concrete cracking on the top surface of the top plate at the support beam 2 is relatively large, especially near the mid-span support beam where the risk of cracking is greatest. Therefore, the top surface of the top plate at the support beam 2 is used as the key test point for structural stress, that is, the location of the stress sensor 4.

[0026] S2. Calculate the maximum allowable value of the four-point plane distortion by using a finite element model; and use the maximum allowable value of the four-point plane distortion as the control value of the four-point plane distortion.

[0027] like Figure 5 As shown, a finite element model of the large-span prefabricated box girder transportation is established, and the maximum structural stress allowed by the specification is obtained according to the provisions of the current relevant national standards for prestressed concrete components; the maximum allowable value of the four-point plane distortion is obtained according to the maximum structural stress allowed by the specification and the finite element model; the maximum allowable value of the four-point plane distortion is used as the control value of the four-point plane distortion.

[0028] For example, according to Article 6.3.1 of my country's "Design Code for Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" JTGD62-2004, the principal tensile stress of the concrete generated by the combination of short-term effects and prestressing of Class A prestressed concrete members is ≤0.7 f tk =2.0MPa, select 2.0MPa as the maximum structural stress allowed by the specification, and assume that under the constraint condition of the maximum structural stress allowed by the specification, the four-point plane distortion corresponding to the finite element model is 50mm, then take 50mm as the control value of the four-point plane distortion.

[0029] S3, using a finite element model to analyze and calculate the initial structural stress at each key test point in the initial state of the long-span prefabricated box girder, and calculating the maximum allowable change value of the structural stress based on the initial structural stress; and using the maximum allowable change value as the control value of the structural stress; like Figure 5As shown, a finite element model for the transportation of the long-span prefabricated box girder is established; finite element calculation is performed according to the finite element model to obtain the initial structural stresses of each key test point corresponding to each key test point in the initial state of the long-span prefabricated box girder; the maximum value of the initial structural stresses of each key test point is selected as the maximum initial structural stress value; according to the provisions of the relevant current national standards for prestressed concrete components, the maximum structural stress allowed by the specification is obtained; the difference between the maximum structural stress and the maximum initial structural stress is used as the maximum allowable change value of the structural stress.

[0030] For example, according to Article 6.3.1 of my country's "Design Code for Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" JTGD62-2004, the principal tensile stress of the concrete generated by the combination of short-term effects and prestressing of Class A prestressed concrete members is ≤0.7 f tk =2.0MPa, 2.0MPa is selected as the maximum allowable structural stress of the specification, and the initial structural stress at each key test point in the initial state of the long-span prefabricated box girder is calculated using the finite element model to obtain the initial structural stress at each key test point. Assuming that the maximum value of the initial structural stress of each key test point is -3.0MPa (negative value indicates compression), the maximum value of the initial structural stress is taken as the maximum initial structural stress, and the maximum allowable change of the structural stress is 2.0MPa-(-3MPa)=5.0MPa, and the control value of the structural stress is 5.0MPa.

[0031] S4. Obtain the safety risk level of the large-span prefabricated box girder transportation structure according to the control value of the four-point plane distortion, the control value of the structural stress and the warning range.

[0032] The warning range includes a four-point plane distortion warning range and a structural stress warning range.

[0033] The step of dividing the four-point plane distortion warning range includes: selecting three different four-point plane distortion reduction coefficients by themselves, and the values ​​of the four-point plane distortion reduction coefficients are between 0 and 1; multiplying the control value of the four-point plane distortion by the three different selected four-point plane distortion reduction coefficients to obtain three different four-point plane distortion warning values; setting the three different four-point plane distortion warning values ​​in order from large to small as the level I warning value, level II warning value, and level III warning value of the four-point plane distortion; assuming that the three different four-point plane distortion reduction coefficients of the selected area are 0.5, 0.7, and 0.9 respectively; when the control value of the four-point plane torsion is 50mm, the level I warning value, level II warning value, and level III warning value of the four-point plane distortion are 25mm, 35mm, and 45mm respectively.

[0034] The step of dividing the structural stress warning range includes: selecting three different structural stress reduction coefficients by oneself, and the values ​​of the structural stress reduction coefficients are between 0 and 1; multiplying the control value of the structural stress by the three different selected structural stress reduction coefficients to obtain three different structural stress warning values; setting the three different structural stress warning values ​​in order from small to large as the level I warning value, level II warning value, and level III warning value of the structural stress respectively; considering that there is a certain safety reserve during warning, the structural stress reduction coefficients can be set to 0.7, 0.8, and 0.9 respectively; when the control value of the structural stress is 5.0MPa, the level I warning value, level II warning value, and level III warning value of the structural stress are 3.5MPa, 4.0MPa, and 4.5MPa respectively.

[0035] An early warning mechanism is established according to the early warning values ​​of the four-point plane distortion and the early warning value of the structural stress; the early warning mechanism includes: an early warning is implemented when any monitoring value of the monitoring value of the four-point plane distortion or the monitoring value of the structural stress exceeds the respective early warning values; a method for obtaining the monitoring value of the four-point plane distortion: the relative elevation values ​​of the four corner points collected in real time during the transportation of the large-span prefabricated box girder are calculated to obtain the four-point plane distortion obtained in real time, and the four-point plane distortion obtained in real time is used as the monitoring value of the four-point plane distortion; a method for obtaining the monitoring value of the structural stress: the structural stress obtained at each key test point during the transportation of the large-span box girder is respectively subtracted from the structural stress of each key test point in the initial state of the large-span prefabricated box girder to obtain the change value of the structural stress of each key test point, and the change value of the structural stress of each key test point is used as the monitoring value of the structural stress; if any value of the change value of the structural stress of each key test point exceeds the early warning value of the structural stress, it is deemed that the monitoring value of the structural stress exceeds the early warning value of the structural stress.

[0036] According to the early warning mechanism, early warning levels are established, and the early warning levels include: level I early warning, level II early warning, and level III early warning; the level I early warning includes: any of the monitoring values ​​of the four-point plane distortion or the monitoring values ​​of the structural stress exceeds the respective level I early warning value; the level II early warning includes: any of the monitoring values ​​of the four-point plane distortion or the monitoring values ​​of the structural stress exceeds the respective level II early warning value; the level III early warning includes: any of the monitoring values ​​of the four-point plane distortion or the monitoring values ​​of the structural stress exceeds the respective level III early warning value; Figure 4As shown, assuming that the relative elevation values ​​of the four corner points, corner point 1, corner point 2, corner point 3, and corner point 4 are 10mm, -15mm, 30mm, and 15mm respectively, the four-point plane distortion value is 40mm, which exceeds the level II warning value of 35mm of the four-point plane distortion. Assuming that the change value of the structural stress at this time is 4MPa, which exceeds the level I warning value of 3.5MPa of the structural stress, the warning level at this time is level II warning.

[0037] The safety risk level of the large-span prefabricated box girder transportation structure is obtained according to the warning level; the safety risk level of the large-span prefabricated box girder transportation structure includes: when there is no warning, the safety risk level of the large-span prefabricated box girder transportation structure is at a low risk level; when there is a level I warning, the safety risk level of the large-span prefabricated box girder transportation structure is at a medium risk level; when there is a level II warning, the safety risk level of the large-span prefabricated box girder transportation structure is at a high risk level; when there is a level III warning, the safety risk level of the large-span prefabricated box girder transportation structure is at an extremely high risk level.

[0038] The process is adjusted according to the safety risk level of the large-span prefabricated box girder transportation structure; the adjustment of the process includes: when the safety risk level of the large-span prefabricated box girder transportation structure is at a low risk level, no adjustment is made; when the safety risk level of the large-span prefabricated box girder transportation structure is at a medium risk level, attention is paid to the changes in the four-point plane distortion or structural stress, and no adjustment is made; when the safety risk level of the large-span prefabricated box girder transportation structure is at a high risk level, the operation speed of the transportation equipment is slowed down, and the adjustment of the process is guided by the relative elevation values ​​of the four corner points and the four-point plane distortion; when the safety of the large-span prefabricated box girder transportation structure is at an extremely high risk level, the operation of the transportation equipment is stopped, and the adjustment of the process is guided by the relative elevation values ​​of the four corner points and the four-point plane distortion, until the structural safety level drops below the medium level, the transportation equipment can be started to continue to move forward; Figure 4As shown, assuming that the relative elevation values ​​of the four corner points, corner point 1, corner point 2, corner point 3, and corner point 4 are 10mm, -15mm, 30mm, and 15mm respectively, the four-point plane distortion value is 40mm, which exceeds the II-level warning value of 35mm of the four-point plane distortion. Assuming that the change value of the structural stress at this time is 4MPa, which exceeds the I-level warning value of the structural stress of 3.5MPa, the warning level at this time is II-level warning, and the safety risk level of the large-span prefabricated box girder transportation structure is at a high risk level. Slow down the running speed of the transportation equipment, and guide the adjustment of the process according to the relative elevation values ​​of the four corner points and the four-point plane distortion, that is, reduce the oil pressure in the B2 and D2 areas to reduce the corner point 3 or increase the oil pressure in the B1 and D1 areas to increase the corner point 2, and the adjustment amount is less than or equal to 40m m; assuming that the relative elevation values ​​of the four corner points, corner point 1, corner point 2, corner point 3, and corner point 4 are -15mm, 10mm, 15mm, and 30mm respectively, the four-point plane distortion value is 40mm, which exceeds the Level II warning value of 35mm of the four-point plane distortion. Assuming that the change value of the structural stress at this time is 4MPa, which exceeds the Level I warning value of 3.5MPa of the structural stress, the warning level at this time is Level II warning, and the safety risk level of the large-span prefabricated box girder transportation structure is at a high risk level. Slow down the operating speed of the transportation equipment, and guide the process adjustment according to the relative elevation values ​​of the four corner points and the four-point plane distortion, that is, reduce the oil pressure in areas A2 and C2 to lower corner point 4 or increase the oil pressure in areas A1 and C1 to raise corner point 1, and the adjustment amount is less than or equal to 40mm.

[0039] Example 2 The present embodiment provides a monitoring and early warning system for the safety control of the transportation structure of large-span prefabricated box girders, comprising: a sensor for collecting relative elevation values ​​and structural stresses of four corner points of the large-span prefabricated box girders; a collector for communicating with the sensor and collecting data collected by the sensor; a monitoring system for obtaining the safety risk level of the transportation structure of large-span prefabricated box girders according to the control value of the plane distortion at the four points, the control value of the structural stress and the early warning range.

[0040] like Figure 6 As shown, sensors are arranged at monitoring points, which are the four corner points of the long-span prefabricated box girder and the key test points of the structural stress, and the sensors include displacement sensors and stress sensors; Figure 2 As shown, the displacement sensor adopts a static level 3, which is arranged at the four corner points of the long-span prefabricated box girder 1; Figure 7 As shown, a static level support 31 is installed at the intersection of the bottom plate and the web of the long-span prefabricated box girder 1 through bolts 32 and nuts 33, and a static level 3 is installed on the support 31 to obtain the relative elevation values ​​of the four corner points; Figure 2As shown, the stress sensor 4 is installed on the top surface of the top plate of each supporting beam 2 of the long-span prefabricated box beam 1, as shown in FIG. Figure 8 As shown, the stress sensor 4 is arranged along the longitudinal direction of the long-span prefabricated box girder, and is used to obtain the structural stress of the long-span prefabricated box girder; the sensor transmits the relative elevation values ​​of the four corner points and the structural stress collected to the collector; the collector transmits the relative elevation values ​​of the four corner points and the structural stress transmitted by the sensor to the monitoring system; the monitoring system can receive and process the data collected by the collector, obtain the monitoring value of the four-point plane distortion and the monitoring value of the structural stress, and obtain the safety risk level of the transportation structure of the long-span prefabricated box girder according to the control value of the four-point plane distortion, the control value of the structural stress and the warning range; the monitoring system comprises: information transmission equipment, a host computer system, data processing software, an audible and visual alarm device, a process adjustment instruction, and a mobile power supply; the information transmission equipment is used to transmit the data collected by the collector to the host computer system, and the host computer system is connected to the collector through the information transmission equipment; the host computer system obtains the transportation structure of the long-span prefabricated box girder according to the control value of the four-point plane distortion, the control value of the structural stress and the warning range. The data processing software is installed on the host computer system, processes the data collected by the acquisition instrument to obtain the monitoring values ​​of the four-point plane distortion and the monitoring values ​​of the structural stress, and transmits the monitoring values ​​of the four-point plane distortion and the monitoring values ​​of the structural stress to the host computer system; the sound and light alarm device is connected to the host computer system for communication, and realizes the sound and light alarm according to the safety risk level of the large-span prefabricated box girder transportation structure obtained by the host computer system. Assuming that the safety risk level of the large-span prefabricated box girder transportation structure is medium risk, the sound and light alarm system The system flashes a yellow light and voice broadcasts "medium risk". Assuming that the safety risk level of the large-span prefabricated box girder transportation structure is high risk, the sound and light alarm system flashes a red light and voice broadcasts "high risk"; the process adjustment instruction adjusts the process according to the safety risk level of the large-span prefabricated box girder transportation structure obtained by the host computer system to reduce the safety risk level of the large-span prefabricated box girder transportation structure. The specific process adjustment steps of the process adjustment instruction can be displayed on the host computer system; the mobile power supply supplies power to the collector and the information transmission equipment.

[0041] The above description is only a preferred embodiment of the present invention. It should be pointed out that those skilled in the art can make improvements without departing from the principle of the present invention, and the improvements should also be regarded as within the protection scope of the present invention.

Claims

1. A monitoring and early warning method for the safety of a large-span prefabricated box girder transportation structure, characterized in that: The following steps are involved: S1. Select four-point plane distortion and structural stress as the safety monitoring parameters of long-span prefabricated box girders; The step of obtaining the four-point plane distortion comprises: regarding the positions of the four corner points of the bottom plate of the long-span prefabricated box girder in the initial state as the zero-point positions of the elevation of the four corner points; Recording the relative elevation values ​​of the four corner points relative to the elevation zero point during the transportation of the long-span prefabricated box girder, adding the relative elevation values ​​of the diagonal corner points among the four corner points to obtain the sum of the relative elevation values ​​of the two groups of diagonal corner points; Calculate the absolute value of the difference between the sum of the relative elevation values ​​of the two sets of diagonal corner points, where the absolute value is the four-point plane distortion; S2, using a finite element model to analyze and calculate the maximum allowable value of the four-point plane distortion; using the maximum allowable value of the four-point plane distortion as the control value of the four-point plane distortion; S3, using a finite element model to analyze and calculate the initial structural stress at each key test point in the initial state of the long-span prefabricated box girder, and calculating the maximum allowable change value of the structural stress based on the initial structural stress; and using the maximum allowable change value as the control value of the structural stress; S4. Obtain the safety risk level of the large-span prefabricated box girder transportation structure according to the control value of the four-point plane distortion, the control value of the structural stress and the warning range.

2. The method for monitoring and early warning of the safety of a large-span prefabricated box girder transportation structure according to claim 1 is characterized in that: In step S4, the warning range includes a four-point plane distortion warning range and a structural stress warning range; The step of dividing the four-point plane distortion warning range includes: multiplying the control value of the four-point plane distortion by three different four-point plane distortion reduction coefficients to obtain three different four-point plane distortion warning values; The three different four-point plane distortion warning values ​​are set in descending order as the level I warning value, level II warning value, and level III warning value of the four-point plane distortion; The step of dividing the structural stress warning range includes: multiplying the control value of the structural stress by three different structural stress reduction coefficients to obtain three different structural stress warning values; setting the three different structural stress warning values ​​in order from large to small as level I warning value, level II warning value, and level III warning value of the structural stress.

3. The method for monitoring and early warning of the safety of a large-span prefabricated box girder transportation structure according to claim 2 is characterized in that: Establishing an early warning mechanism according to the early warning values ​​of the four-point plane distortion and the early warning values ​​of the structural stress; The early warning mechanism includes: issuing an early warning when any of the monitoring values ​​of the four-point plane distortion or the monitoring values ​​of the structural stress exceeds the respective early warning values; The monitoring value of the four-point plane distortion is the four-point plane distortion obtained in real time during the transportation of the long-span prefabricated box girder; The monitoring value of the structural stress is a change value of the structural stress obtained in real time during the transportation of the long-span prefabricated box girder relative to the structural stress in the initial state of the long-span prefabricated box girder.

4. The method for monitoring and early warning of the safety of a large-span prefabricated box girder transportation structure according to claim 3 is characterized in that: According to the early warning mechanism, an early warning level is established. If the early warning level is level I warning or the structural stress early warning level is level I warning, the monitoring result is level I warning; If the warning level is level II warning or the structural stress warning level is level II warning, the monitoring result is level II warning; If the warning level is level III warning or the structural stress warning level is level III warning, the monitoring result is level III warning.

5. The method for monitoring and early warning of the safety of a large-span prefabricated box girder transportation structure according to claim 4 is characterized in that: According to the warning level, the safety risk level of the large-span prefabricated box girder transportation structure is obtained; The safety risk levels of the large-span prefabricated box girder transportation structure include: When there is no warning, the safety risk level of the large-span prefabricated box girder transportation structure is at a low risk level; In the case of level I warning, the safety risk level of the large-span prefabricated box girder transportation structure is at a medium risk level; When the warning level is II, the safety risk level of the large-span prefabricated box girder transportation structure is at a high risk level; During the Level III warning, the safety risk level of the large-span prefabricated box girder transportation structure is at an extremely high risk level.

6. The method for monitoring and early warning of the safety of a large-span prefabricated box girder transportation structure according to claim 5 is characterized in that: The process is adjusted according to the safety risk level of the large-span prefabricated box girder transportation structure.

7. A monitoring and early warning system for the safety of large-span prefabricated box girder transportation structure, used to implement the method described in any one of claims 1 to 6, characterized in that: include: Sensors, used to collect relative elevation values ​​and structural stresses of four corner points of the long-span prefabricated box girder; A collector, connected to the sensor for collecting data from the sensor; The monitoring system obtains the safety risk level of the large-span prefabricated box girder transportation structure based on the control value of the four-point plane distortion, the control value of the structural stress and the early warning range.

8. The monitoring and early warning system for the safety of transport structure of large-span prefabricated box beams according to claim 7 is characterized in that: The sensor includes a displacement sensor and a stress sensor; The displacement sensor adopts a static level to obtain the relative elevation values ​​of the four corner points of the long-span prefabricated box girder; The stress sensor is used to obtain the structural stress of the long-span prefabricated box girder.

9. The monitoring and early warning system for the safety of transport structure of large-span prefabricated box beams according to claim 7 is characterized in that: It also includes an audible and visual alarm component for audible and visual alarm of the risk level of the large-span prefabricated box girder transportation structure.

10. The monitoring and early warning system for the safety of transport structure of large-span prefabricated box beams according to claim 7 is characterized in that: It also includes an adjusting component for adjusting the process of the large-span prefabricated box girder transportation structure in real time.

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