Safety risk assessment and early warning method based on steel beam synchronous incremental launching construction

Abstract

The invention discloses a safety risk assessment and early warning method based on steel beam synchronous incremental launching construction, which sequentially comprises the steps of WBS work decomposition, typical accident analysis, safety risk identification, accident tree model establishment, Bayesian network topological structure establishment and the like. The method comprises the following steps: determining causal relevance between a safety risk accident result event and a basic event in a synchronous incremental launching construction process, performing probability analysis according to an accident result and an accident cause, calculating a sensitivity coefficient and a key risk factor, and realizing efficient identification and accurate confirmation of each key monitoring index in the construction process. According to the method, systematic establishment of a safety risk early warning system for synchronous incremental launching construction is ensured, effective identification and early warning of safety risks in the synchronous incremental launching construction process in the industry are ensured, the safety of the large-span long-connected steel beams in the synchronous incremental launching construction process is improved, safety accidents in the synchronous incremental launching process are effectively reduced, and the safety risk early warning effect is improved. And high efficiency and economical efficiency in the construction process are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of safety in synchronous jacking construction of steel beams, and more particularly to a safety risk assessment and early warning method based on synchronous jacking construction of steel beams. Background Art

[0002] In recent years, with the continuous development of the "four new technologies"—new materials, new technologies, new processes, and new equipment—my country's bridge construction has achieved continuous breakthroughs and rapid development, gradually presenting characteristics such as ultra-high, ultra-wide, large spans, long spans, and new structures. At the same time, bridge construction methods have also been continuously innovated and developed. Among them, the synchronous jacking method is widely used in multi-span, long-span steel box girder bridges due to its advantages such as high efficiency, good economy, high construction precision, and minimal construction impact. The synchronous jacking construction process, due to factors such as the design and layout of temporary support structures, the installation of jacking equipment, the synchronization and accuracy, and the compliance of personnel operations, often leads to various safety risks during construction, such as temporary support instability, excessive stress on steel beams and guide beams, local deformation or overturning of steel beams, steel beam posture deviation, jacking equipment failure, and hydraulic system leakage. In severe cases, it often leads to the overturning of steel beams or temporary structures during construction, causing serious structural damage. Therefore, there is an urgent need to find a safety risk assessment and early warning method based on the synchronous jacking construction of steel beams to solve the difficult problems of multi-factor coupling, dynamic evolution, hidden suddenness, significant environmental interference, and extremely serious consequences of safety risks in the synchronous jacking construction process of steel beams, and to achieve quantitative assessment and accurate early warning of safety risks in the synchronous jacking construction process. Summary of the Invention

[0003] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0004] Another object of the present invention is to provide a safety risk assessment and early warning method based on synchronous jacking construction of steel beams, so as to solve the technical problem of inaccurate safety risk assessment of synchronous jacking construction of steel beams in the prior art.

[0005] In order to achieve these purposes and other advantages according to the present invention, a safety risk assessment and early warning method based on synchronous jacking construction of steel beams is provided, comprising the following steps: S1. Determine and decompose the construction operation procedure of synchronous jacking of steel beams, and obtain a decomposition table of the construction operation procedures of synchronous lifting, synchronous jacking, and synchronous sliding; S2. Analyze typical accidents for each procedure in the construction operation procedure breakdown table and form a safety risk identification list; S3. Combine the construction procedure breakdown table in step S1 and the safety risk identification list in step S2 to form a synchronous jacking safety risk accident analysis table. Risk accidents are divided into jacking equipment risks, bridge structure and temporary structure risks, and natural environment risks. S4. For the synchronous jacking safety risk accident analysis table of step S3, based on the fault tree analysis method, steel beam instability is analyzed as the top event, and failure of steel beam jacking posture control, failure of steel beam horizontal pushing posture control, failure of steel beam lowering posture control, and failure of guide beam passing pier posture control are analyzed as intermediate events. The direct events that lead to the intermediate events are taken as basic events, and the top event and intermediate events are taken as result events to establish a fault tree model for synchronous jacking construction; S5. Establishing a Bayesian network topology structure based on the fault tree model, wherein the basic events, intermediate events, and top events in the fault tree model correspond to the root node, intermediate node, and leaf node in the Bayesian network topology structure, respectively; S6. Analyze the frequency of occurrence of basic events, use Genie software to simulate the Bayesian network model, obtain the probability of occurrence of top events, and perform sensitivity analysis to obtain key risk factors; S7. Determine key monitoring indicators based on key risk factors; S8. Establish risk warning rules and levels for key monitoring indicators, and assess safety risks in real time during the monitoring process. Preferably, the construction procedures of synchronous lifting, synchronous pushing and synchronous sliding in step S1 are broken down into details to obtain a construction procedure breakdown table of guide beam installation, steel beam lifting, assembly and docking, steel beam jacking construction, steel beam sliding forward, steel beam lowering construction and guide beam passing pier construction. Corresponding to step S2, the typical accident analysis of the guide beam installation process is a collapse accident, the typical accident analysis of the steel beam assembly and docking process is a mechanical injury accident, the typical accident analysis of the steel beam jacking construction process is a collapse accident, the typical accident analysis of the steel beam forward movement and advancement process is an object impact accident, the typical accident analysis of the steel beam lowering construction process is a collapse accident, and the typical accident analysis of the guide beam passing the temporary pier construction process is a height fall accident.

[0006] Preferably, in step S3, the risks of the jacking equipment include oil leakage in the cylinder, oil leakage in the pump station, and entanglement of the steel strands; the structural risks include instability of the guide beam, instability of the steel beam, and instability of the temporary pier; and the natural environment risks include engineering geological and hydrological conditions and natural disasters.

[0007] Preferably, the judgment condition for failure of the steel beam pushing posture control is to meet any one of the following four conditions: Condition 1: Hydraulic system synchronization error: 1) The deviation between the single-point lifting displacement and the design value is greater than ±2mm; 2) The height difference between adjacent jacking points in the span direction is greater than 1mm / m or the height difference between adjacent jacking points is greater than L / 4000, where L is the span; Condition 2: Speed ​​difference at multiple jacking points: The speed difference at each jacking point is greater than 10% of the design value and lasts for more than 5 minutes; Condition 3: Geometric deformation of posture exceeds the limit: 1) Axis deviation: lateral offset of steel beam>10mm or lateral offset of steel beam>L / 5000; 2) Torsion angle: cross-sectional torsion angle > 0.5°, or linear distortion > 3 mm / m; 3) Local warping: When the jacking span is ≤30m, the local elevation difference between adjacent monitoring points is greater than 3mm; or when the jacking span is greater than 30m, the local elevation difference between adjacent monitoring points is greater than 5mm; Condition 4: Structural stress / strain exceeds the limit: 1) Material stress exceeds the limit: the measured stress of the steel beam is greater than 0.8fy, where fy is the yield strength of the steel; 2) Abnormal temporary support reaction: The deviation between the temporary pier support reaction and the theoretical value is greater than 15%, or single-point unloading or a sudden drop in reaction force occurs.

[0008] Preferably, the judgment condition for failure of the horizontal push posture control of the steel box girder is to meet any one of the following three conditions: Condition 1: Excessive horizontal axis deviation: If the real-time monitoring shows that the deviation between the center line of the beam and the design axis is continuously greater than 5mm and cannot be automatically reset, or if the real-time monitoring shows that the deviation between the center line of the beam and the design axis is continuously greater than 10mm, it is judged as a failure; Condition 2: Longitudinal linear deviation exceeds the limit: 1) Elevation error: When the jacking span is ≤50m, the deviation between the elevation of each support point and the design value is greater than ±3mm; when the jacking span is greater than 50m, the deviation between the elevation of each support point and the design value is greater than ±5mm; 2) Abnormal slope: the longitudinal slope change rate of the beam is greater than 0.5%; Condition 3: Torsion and plane angle exceed the limit: 1) Torsion angle: Section torsion angle > 0.5°, or beam end lateral displacement difference > 3mm / m; 2) Plane deflection angle: The angle between the longitudinal axis of the beam and the pushing direction is greater than 1°, or the lateral displacement rate is greater than 2mm / min.

[0009] Preferably, the judgment condition for failure of the steel box girder lowering posture control is to meet any one of the following four conditions: Condition 1: Synchronicity deviation exceeds the limit: 1) Single point drop displacement deviation: Deviation from the designed drop value>±2mm; 2) Speed ​​asynchrony: The difference in descent speed at each point is greater than 10% of the design value and lasts for more than 2 minutes; Condition 2: Abnormal posture geometry deformation: 1) Overall tilt: When the jacking span is ≤30m, the height difference between the two ends of the beam is greater than 5mm; when the jacking span is greater than 30m, the height difference between the two ends of the beam is greater than 10mm; 2) Local warping: local height difference between adjacent monitoring points>3mm; Condition 3: Temporary support system abnormality: 1) Imbalance of support reaction force: the deviation between the temporary pier reaction force and the theoretical value is greater than 15%, or a sudden drop in single-point reaction force is greater than 20%; 2) Support structure deformation: vertical displacement of temporary pier > 3mm, or horizontal displacement > 2mm; Condition 4: Steel box girder stress exceeds limit: 1) Key section stress: measured stress > 0.8fy; 2) Sudden change warning: stress change rate > 5MPa / min, or increase > 10%fy within 10 minutes.

[0010] Preferably, the judgment condition for failure of the guide beam passing through the pier posture control is to meet any one of the following three conditions: Condition 1: The guide beam axis is out of limit: 1) The deviation between the center line of the guide beam and the design axis of the pier top is greater than 10mm; 2) The gap between the pier top guide device and the guide beam is greater than 15mm; 3) The length of the front end of the guide beam overhanging the pier top is greater than the design value ±5%; Condition 2: The connection between the guide beam and the main beam is abnormal: 1) The vertical height difference between the guide beam and the main beam joint is greater than 3mm; 2) The stress at the connection part is greater than 0.7fy, or the strain is greater than 1500με; Condition 3: Failure of the temporary support system: the deviation between the support reaction force and the theoretical value is greater than 20%, or the reaction force of a single pier returns to zero.

[0011] Preferably, in step S6, the key risk factors in the process of synchronous jacking construction of steel beams are set as oil cylinder leakage m , Main beam stress is too large σ b , the guide beam stress is too large σ d , temporary pier stress is too large σ1, temporary pier displacement ΔX , oil leakage at pumping station n , Steel Strand Winding l , first establish the risk mathematical model through finite element software , then calculate the partial derivative, and then use the normalized sensitivity coefficient calculation formula , calculate the sensitivity coefficients of each risk factor and eliminate the dimension effect, among which is the benchmark value of the risk indicator, is the baseline value of the risk factor.

[0012] Preferably, in step S8, warning rules with different warning level thresholds, threshold triggering rules, time window rules, anomaly detection rules, and statistical rules are established for each key monitoring indicator, and the warning levels are 90%, 80%, 70%, and 60% of the theoretical values, respectively, and are divided into lower levels in sequence.

[0013] The present invention has at least the following beneficial effects: The safety risk assessment and early warning method based on the synchronous jacking construction of steel beams of the present invention sequentially performs the steps of WBS work decomposition, typical accident analysis, safety risk identification, accident tree model establishment, and Bayesian network topology structure establishment to determine the causal relationship between the safety risk accident result events and basic events in the synchronous jacking construction process, conducts probability analysis based on the accident results and the causes of the accidents, calculates the sensitivity coefficient and key risk factors, and realizes efficient identification and accurate confirmation of each key monitoring indicator in the construction process, thereby ensuring the systematic establishment of a safety risk early warning system for synchronous jacking construction, ensuring the effective identification and early warning of safety risks in the industry during the synchronous jacking construction process, improving the safety of large-span long-jointed steel beams during the synchronous jacking construction process, effectively reducing safety accidents during the synchronous jacking process, and ensuring high efficiency and economy during the construction process.

[0014] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic flow chart of the steps of the synchronous jacking construction safety risk assessment and early warning method of the present invention; Figure 2 This is a schematic diagram of a risk identification checklist for synchronous jacking construction operations according to the present invention; Figure 3 This is a schematic representation of the risk analysis of the types of safety accidents in the synchronous jacking construction of the present invention; Figure 4 This is a schematic diagram of a fault tree model for synchronous jacking construction according to the present invention; Figure 5 Schematic diagram of the Bayesian network topology model for synchronous jacking construction of the present invention; Figure 6 This is a schematic diagram of the conversion from a fault tree to a Bayesian network according to the present invention; Figure 7 Schematic diagram of key risk factors of synchronous jacking construction of the present invention; Figure 8 This is a schematic diagram of key monitoring indicators for synchronous jacking construction of the present invention; Figure 9 This is a schematic diagram of the synchronous jacking construction early warning system of the present invention; Figure 10 This is a schematic structural diagram of a first floating detection component according to an embodiment of the present invention.

[0016] Figure numerals in the specification: 1. first flexible sleeve, 2. first float, 3. first flexible blocking grid. DETAILED DESCRIPTION

[0017] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0018] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "horizontal", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0019] like Figure 1-9 As shown, the present invention provides a safety risk assessment and early warning method based on synchronous jacking construction of steel beams, comprising the following steps: S1. Determine and decompose the construction operation procedures for synchronous jacking of steel beams. Combined with the construction organization and environmental conditions at the site of the three-span steel box girder continuous beam bridge project, and based on the specific construction process flow of the synchronous jacking method for steel box beams, the synchronous lifting, synchronous jacking, and synchronous sliding are broken down into detailed details according to the operation activities, resulting in a decomposition table for the construction operation procedures for synchronous lifting, synchronous jacking, and synchronous sliding.

[0020] S2. Conduct typical accident analysis for each procedure in the construction procedure breakdown table. Use methods such as safety assessment team discussion, on-site investigation, expert consultation and review, and systematically analyze the typical risk accident types that may occur in each assessment unit based on the "Technical Regulations for Bridge Jacking Construction", "Guidelines for Highway Engineering Construction Safety Risk Assessment" and "Construction Hazard Source Identification and Risk Assessment Standards" to form a safety risk identification list.

[0021] S3. Combined with the construction procedure breakdown table of step S1 and the safety risk identification list of step S2, analyze the causes of accidents from the perspectives of equipment, structure and environment respectively to form a synchronous jacking safety risk accident analysis table. Risk accidents are divided into jacking equipment risks, bridge structure and temporary structure risks, and natural environment risks.

[0022] S4. For the synchronous jacking safety risk accident analysis table of step S3, based on the fault tree analysis method, the instability of the steel beam is taken as the top event, and the instability of the steel beam is analyzed. The failure of the steel beam jacking posture control, the failure of the steel beam horizontal pushing posture control, the failure of the steel beam lowering posture control, and the failure of the guide beam passing the pier posture control are taken as intermediate events. The intermediate events are analyzed. According to the synchronous jacking process of the steel box girder, the risk events at each level are identified step by step. The direct events that lead to the occurrence of the intermediate events are taken as basic events, and the top events and intermediate events are taken as result events. A complete set of fault trees is formed, and a fault tree model for synchronous jacking construction is established.

[0023] S5. Through the fault tree to Bayesian network transformation mapping method, a Bayesian network topology structure is established based on the fault tree model. The basic events, intermediate events and top events in the fault tree model correspond to the root node, intermediate node and leaf node in the Bayesian network topology structure respectively.

[0024] S6. Comprehensively adopt the method of combining expert investigation with survey data, make full use of the experience and knowledge of experts, and prepare questionnaires to interview relevant experts based on the "Technical Code for Bridge Jacking Construction", "Guidelines for Highway Engineering Construction Safety Risk Assessment" and "Construction Hazard Source Identification and Risk Assessment Standards" to obtain the occurrence frequency of each root node event in the Bayesian network, that is, analyze the occurrence frequency of basic events, use Genie software to simulate and calculate the Bayesian network model, obtain the probability of occurrence of the jacking event, perform sensitivity analysis to obtain key risk factors, and calculate the sensitivity coefficient of each risk factor.

[0025] S7. Determine key monitoring indicators based on key risk factors. Based on the seven key risk factors in the synchronous jacking construction of a three-span steel box girder continuous girder bridge, five key monitoring indicators and two important indicators were identified for the synchronous jacking construction process. The five key monitoring indicators are main beam stress, guide beam stress, temporary pier stress, oil cylinder leakage, and temporary pier displacement. The two important indicators are oil leakage from the pump station and strand entanglement. During the synchronous jacking construction of steel beams, the two key indicators of temporary pier displacement and main beam stress should be monitored. The real-time data status of these two key indicators can be used to assess the safety risk status of the synchronous jacking construction process in real time.

[0026] S8. Establish risk warning rules and levels for key monitoring indicators, and assess safety risks in real time during the monitoring process. Based on the actual project and the attributes and characteristics of each monitoring indicator, a warning system with different warning level thresholds, threshold triggering rules, anomaly detection rules, time window rules, and statistical rules is established for each key monitoring indicator. This enables accurate and effective graded warnings for safety risks during synchronous jacking construction. Furthermore, warning levels are categorized based on the severity and impact of safety incidents, and these warnings are sent to management personnel at different levels according to their level.

[0027] The safety risk assessment and early warning method based on the synchronous jacking construction of steel beams of the present invention sequentially performs the steps of WBS work decomposition, typical accident analysis, safety risk identification, accident tree model establishment, and Bayesian network topology structure establishment to determine the causal relationship between the safety risk accident result events and basic events in the synchronous jacking construction process, conducts probability analysis based on the accident results and the causes of the accidents, calculates the sensitivity coefficient and key risk factors, and realizes efficient identification and accurate confirmation of each key monitoring indicator in the construction process, thereby ensuring the systematic establishment of a safety risk early warning system for synchronous jacking construction, ensuring the effective identification and early warning of safety risks in the industry during the synchronous jacking construction process, improving the safety of large-span long-jointed steel beams during the synchronous jacking construction process, effectively reducing safety accidents during the synchronous jacking process, and ensuring high efficiency and economy during the construction process.

[0028] In another technical solution, Figure 2 As shown, the construction procedures of synchronous lifting, synchronous jacking and synchronous sliding in step S1 are broken down in detail, and a decomposition table of the construction procedures of guide beam installation, steel beam lifting, assembly and docking, steel beam jacking construction, steel beam sliding forward, steel beam lowering construction and guide beam passing pier construction is obtained. Corresponding to step S2, in the guide beam installation process, collapse accidents are mainly caused by the weak structural integrity; in the steel beam assembly and docking process, mechanical injury accidents are mainly caused by the cross operation of large machinery and frequent operations; in the steel beam jacking construction process, structural collapse accidents are mainly caused by steel beam instability, uneven force distribution of temporary pier support points, and jacking force error of jacking equipment; in the steel beam forward movement process, object impact accidents are mainly caused by the movement of the overall structure; in the steel beam lowering construction process, collapse accidents are mainly caused by uneven return force of each temporary pier support point, large local stress of the steel beam, and error in the jacking equipment lowering control; in the guide beam passing temporary pier construction process, falling accidents are mainly caused by the change of structural stress state.

[0029] In another technical solution, Figure 3-7 As shown in step S3, the main risks for jacking equipment include oil cylinder leakage, oil pump station leakage, and stranded wire. The main structural risks include guide beam instability, steel beam instability, and temporary pier instability. The main environmental risks include engineering geological and hydrological conditions and natural disasters. The risk factors are ranked by importance to determine the key parameters to be monitored.

[0030] In another technical solution, Figure 3-6 As shown in the figure, the conditions for generating intermediate events are refined. The judgment condition for failure of the steel beam pushing posture control is to meet any one of the following four conditions: Condition 1: Hydraulic system synchronization error: 1) The deviation between the single-point lifting displacement and the design value is greater than ±2mm; 2) The height difference between adjacent jacking points in the span direction is greater than 1mm / m or the height difference between adjacent jacking points is greater than L / 4000, where L is the span; Condition 2: Speed ​​difference at multiple jacking points: The speed difference at each jacking point is greater than 10% of the design value and lasts for more than 5 minutes; Condition 3: Geometric deformation of posture exceeds the limit: 1) Axis deviation: lateral offset of steel beam>10mm or lateral offset of steel beam>L / 5000; 2) Torsion angle: cross-sectional torsion angle > 0.5°, or linear distortion > 3 mm / m; 3) Local warping: When the jacking span is ≤30m, the local elevation difference between adjacent monitoring points is greater than 3mm; or when the jacking span is greater than 30m, the local elevation difference between adjacent monitoring points is greater than 5mm; Condition 4: Structural stress / strain exceeds the limit: 1) Material stress exceeds the limit: the measured stress of the steel beam is greater than 0.8fy, where fy is the yield strength of the steel; 2) Abnormal temporary support reaction: The deviation between the temporary pier support reaction and the theoretical value is greater than 15%, or single-point unloading or a sudden drop in reaction force occurs.

[0031] The judgment condition for failure of the horizontal push attitude control of the steel box girder is to meet any one of the following three conditions: Condition 1: Excessive horizontal axis deviation: If the real-time monitoring shows that the deviation between the center line of the beam and the design axis is continuously greater than 5mm and cannot be automatically reset, or if the real-time monitoring shows that the deviation between the center line of the beam and the design axis is continuously greater than 10mm, it is judged as a failure; Condition 2: Longitudinal linear deviation exceeds the limit: 1) Elevation error: When the jacking span is ≤50m, the deviation between the elevation of each support point and the design value is greater than ±3mm; when the jacking span is greater than 50m, the deviation between the elevation of each support point and the design value is greater than ±5mm; 2) Abnormal slope: the longitudinal slope change rate of the beam is greater than 0.5%; Condition 3: Torsion and plane angle exceed the limit: 1) Torsion angle: Section torsion angle > 0.5°, or beam end lateral displacement difference > 3mm / m; 2) Plane deflection angle: The angle between the longitudinal axis of the beam and the pushing direction is greater than 1°, or the lateral displacement rate is greater than 2mm / min.

[0032] The judgment condition for failure of the steel box girder lowering posture control is to meet any one of the following four conditions: Condition 1: Synchronicity deviation exceeds the limit: 1) Single point drop displacement deviation: Deviation from the designed drop value>±2mm; 2) Speed ​​asynchrony: The difference in descent speed at each point is greater than 10% of the design value and lasts for more than 2 minutes; Condition 2: Abnormal posture geometry deformation: 1) Overall tilt: When the jacking span is ≤30m, the height difference between the two ends of the beam is greater than 5mm; when the jacking span is greater than 30m, the height difference between the two ends of the beam is greater than 10mm; 2) Local warping: local height difference between adjacent monitoring points>3mm; Condition 3: Temporary support system abnormality: 1) Imbalance of support reaction force: the deviation between the temporary pier reaction force and the theoretical value is greater than 15%, or a sudden drop in single-point reaction force is greater than 20%; 2) Support structure deformation: vertical displacement of temporary pier > 3mm, or horizontal displacement > 2mm; Condition 4: Steel box girder stress exceeds limit: 1) Key section stress: measured stress > 0.8fy; 2) Sudden change warning: stress change rate > 5MPa / min, or increase > 10%fy within 10 minutes.

[0033] The judgment condition for the failure of the guide beam's attitude control when passing the pier is to meet any one of the following three conditions: Condition 1: The guide beam axis is out of limit: 1) The deviation between the center line of the guide beam and the design axis of the pier top is greater than 10mm; 2) The gap between the pier top guide device and the guide beam is greater than 15mm; 3) The length of the front end of the guide beam overhanging the pier top is greater than the design value ±5%; Condition 2: The connection between the guide beam and the main beam is abnormal: 1) The vertical height difference between the guide beam and the main beam joint is greater than 3mm; 2) The stress at the connection part is greater than 0.7fy, or the strain is greater than 1500με; Condition 3: Failure of the temporary support system: the deviation between the support reaction force and the theoretical value is greater than 20%, or the reaction force of a single pier returns to zero.

[0034] In another technical solution, Figure 7-8 As shown in step S6, the key risk factors in the process of synchronous jacking construction of steel beams are set as oil cylinder leakage m , Main beam stress is too large σ b , the guide beam stress is too large σ d , temporary pier stress is too large σ1, temporary pier displacement ΔX , oil leakage at pumping station n , Steel Strand Winding l , first establish the risk mathematical model through finite element software , then calculate the partial derivative, and then use the normalized sensitivity coefficient calculation formula , calculate the sensitivity coefficients of each risk factor and eliminate the dimension effect, among which is the benchmark value of the risk indicator, is the baseline value of the risk factor.

[0035] Let’s take the finite element software to establish a mathematical model as an example and calculate the partial derivatives: , then the sensitivity coefficients of the two risk factors of oil cylinder leakage and main beam excessive stress are .

[0036] In another technical solution, Figure 9 As shown, in step S8, for each key monitoring indicator, different warning level thresholds, threshold triggering rules, time window rules, anomaly detection rules, and statistical rules are established. The warning levels are 90%, 80%, 70%, and 60% of the theoretical values, respectively, and the levels are divided downward in sequence. The values ​​of the different warning level thresholds for each key monitoring indicator are set according to the theoretical values ​​of each key monitoring indicator. For example, the warning thresholds for the red, orange, yellow, and blue levels can be 90%, 80%, 70%, and 60% of the theoretical values, respectively.

[0037] In another technical solution, Figure 10 As shown, the same node where each intermediate event and basic event is located is sorted to obtain an initial probability sorting, a first floating detection piece is set at the bottom of the front end of the guide beam, and a second floating detection piece is set at the space between the steel beam and the truss supporting the jack at the jacking jack. The first floating detection piece includes a first flexible sleeve 1 and a first float 2 located in the first flexible sleeve. The first flexible sleeve 1 is detachably connected to the bottom of the front end of the guide beam, and the top of the first flexible sleeve 1 is connected to a first flexible block 3. The gas density in the first float 2 is slightly less than the air density, and it floats on the upper side of the first flexible sleeve 1. The second floating detection piece includes a second flexible sleeve and a second float located in the second flexible sleeve. The bottom of the flexible sleeve is detachably connected to the truss at the corresponding position. The detachable connection can be temporarily bonded and a traction rope is set to facilitate quick recovery or pulling it out in case of an accident. The second float can float stably in the air. The top periphery and the bottom periphery of the second flexible sleeve are respectively connected with sliding bars. A detection camera is also set up through the corner bracket support at the steel beam jacking construction site. The detection camera is set toward the first float and the second float for detection and is used for real-time monitoring of jitter or displacement. The detection camera is connected to a remote terminal for communication. An identification module is set in the remote terminal. The detection camera transmits the image to the remote terminal in real time, and the identification module is used to determine whether the first float and the second float are shaking or displacing up and down.

[0038] If there is an obvious position change, it means that there is a safety risk in the pushing process. The positions of the first float and the second float are set corresponding to the obvious position change, which correspond to the monitoring objects in the intermediate events or basic events respectively. They are re-sorted to obtain real-time probability sorting, and the Bayesian network topology structure is rearranged to solve the key risk factors and sensitivity coefficients, and the importance of the key monitoring indicators is rearranged.

[0039] By setting the first float and the second float, the gas filled into the balloon will generate enough buoyancy to make the first float and the second float keep slightly floating or at least descending in the middle of the air, and arrange the measuring point position corresponding to the key detection index where the uncertain monitoring data has priority over other monitoring data, and set the first float in the air. The first flexible block on the first flexible sleeve can be set with a larger grid, and it is only necessary to ensure that the first float with an inner diameter smaller than the first flexible sleeve does not float up and leave the first flexible sleeve. The bottom of the first flexible sleeve and the second flexible sleeve are sealed or set with blocks as needed to ensure that the opening degree of the bottom is not higher than the opening degree of the top. For the larger force or jitter change of the guide beam, it will affect the air pressure and capacity change in the first flexible sleeve in a smaller space, thereby the first float The ball is sensitive to changes, resulting in displacement or jitter. Similarly, during the normal translation process of the steel beam, the internal air capacity of the second flexible sleeve is generally stable. When an abnormality occurs in the translation process of the steel beam, the second flexible sleeve in the smaller space is squeezed, and the internal gas state changes, driving the second float to move or jitter in the space. Therefore, the first float and the second float, which are sensitive to the air state in the smaller space, are used to judge whether the corresponding position has problems or changes that are not easy to detect during the process, and to zoom in and find possible problem measurement points in advance, so as to re-sort the basic conventional key risk factors, improve the scientific nature and early prediction of safety assessment and early warning, and timely adjust key monitoring indicators and important monitoring indicators. In addition, the measurement point structure is simple, the cost is low, and the monitoring changes are easy to detect.

[0040] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A safety risk assessment and early warning method based on synchronous jacking construction of steel beams, characterized in that: The steps include: S1. Determine and decompose the construction operation procedure of synchronous jacking of steel beams, and obtain a decomposition table of the construction operation procedures of synchronous lifting, synchronous jacking, and synchronous sliding; S2. Analyze typical accidents for each procedure in the construction operation procedure breakdown table to form a safety risk identification list; S3. Combine the construction procedure breakdown table in step S1 and the safety risk identification list in step S2 to form a synchronous jacking safety risk accident analysis table. Risk accidents are divided into jacking equipment risks, bridge structure and temporary structure risks, and natural environment risks. S4. For the synchronous jacking safety risk accident analysis table of step S3, based on the fault tree analysis method, steel beam instability is analyzed as the top event, and failure of steel beam jacking posture control, failure of steel beam horizontal pushing posture control, failure of steel beam lowering posture control, and failure of guide beam passing pier posture control are analyzed as intermediate events. The direct events that lead to the intermediate events are taken as basic events, and the top event and intermediate events are taken as result events to establish a fault tree model for synchronous jacking construction; S5. Establishing a Bayesian network topology structure based on the fault tree model, wherein the basic events, intermediate events, and top events in the fault tree model correspond to the root node, intermediate node, and leaf node in the Bayesian network topology structure, respectively; S6. Analyze the frequency of occurrence of basic events, use Genie software to simulate the Bayesian network model, obtain the probability of occurrence of top events, and perform sensitivity analysis to obtain key risk factors; S7. Determine key monitoring indicators based on key risk factors; S8. Establish risk warning rules and levels for key monitoring indicators, and assess safety risks in real time during the monitoring process.

2. The safety risk assessment and early warning method based on synchronous jacking construction of steel beams according to claim 1 is characterized in that: The construction procedures of synchronous lifting, synchronous pushing and synchronous sliding in step S1 are broken down into details, and a construction procedure breakdown table of guide beam installation, steel beam lifting, assembly and docking, steel beam jacking construction, steel beam sliding forward, steel beam lowering construction and guide beam passing pier construction is obtained. Corresponding to step S2, the typical accident analysis of the guide beam installation process is a collapse accident, the typical accident analysis of the steel beam assembly and docking process is a mechanical injury accident, the typical accident analysis of the steel beam jacking construction process is a collapse accident, the typical accident analysis of the steel beam forward movement and advancement process is an object impact accident, the typical accident analysis of the steel beam lowering construction process is a collapse accident, and the typical accident analysis of the guide beam passing the temporary pier construction process is a height fall accident.

3. The safety risk assessment and early warning method based on synchronous jacking construction of steel beams according to claim 1 is characterized in that: In step S3, the risks of jacking equipment include oil cylinder leakage, oil pump station leakage, and steel strand entanglement; structural risks include guide beam instability, steel beam instability, and temporary pier instability; and natural environment risks include engineering geological and hydrological conditions and natural disasters.

4. The safety risk assessment and early warning method based on synchronous jacking construction of steel beams according to claim 1 is characterized in that: The judgment condition for failure of the steel beam pushing posture control is to meet any one of the following four conditions: Condition 1: Hydraulic system synchronization error: 1) The deviation between the single-point lifting displacement and the design value is greater than ±2mm; 2) The height difference between adjacent jacking points in the span direction is greater than 1mm / m or the height difference between adjacent jacking points is greater than L / 4000, where L is the span; Condition 2: Speed ​​difference at multiple jacking points: The speed difference at each jacking point is greater than 10% of the design value and lasts for more than 5 minutes; Condition 3: Geometric deformation of posture exceeds the limit: 1) Axis deviation: lateral offset of steel beam>10mm or lateral offset of steel beam>L / 5000; 2) Torsion angle: cross-sectional torsion angle > 0.5°, or linear distortion > 3 mm / m; 3) Local warping: When the jacking span is ≤30m, the local elevation difference between adjacent monitoring points is greater than 3mm; or when the jacking span is greater than 30m, the local elevation difference between adjacent monitoring points is greater than 5mm; Condition 4: Structural stress / strain exceeds the limit: 1) Material stress exceeds the limit: the measured stress of the steel beam is greater than 0.8fy, where fy is the yield strength of the steel; 2) Abnormal temporary support reaction: The deviation between the temporary pier support reaction and the theoretical value is greater than 15%, or single-point unloading or a sudden drop in reaction force occurs.

5. The safety risk assessment and early warning method based on synchronous jacking construction of steel beams according to claim 1 is characterized in that: The judgment condition for failure of the horizontal push attitude control of the steel box girder is to meet any one of the following three conditions: Condition 1: Excessive horizontal axis deviation: If the real-time monitoring shows that the deviation between the center line of the beam and the design axis is continuously greater than 5mm and cannot be automatically reset, or if the real-time monitoring shows that the deviation between the center line of the beam and the design axis is continuously greater than 10mm, it is judged as a failure; Condition 2: Longitudinal linear deviation exceeds the limit: 1) Elevation error: When the jacking span is ≤50m, the deviation between the elevation of each support point and the design value is greater than ±3mm; when the jacking span is greater than 50m, the deviation between the elevation of each support point and the design value is greater than ±5mm; 2) Abnormal slope: the longitudinal slope change rate of the beam is greater than 0.5%; Condition 3: Torsion and plane angle exceed the limit: 1) Torsion angle: Section torsion angle > 0.5°, or beam end lateral displacement difference > 3mm / m; 2) Plane deflection angle: The angle between the longitudinal axis of the beam and the pushing direction is greater than 1°, or the lateral displacement rate is greater than 2mm / min.

6. The safety risk assessment and early warning method based on synchronous jacking construction of steel beams according to claim 1 is characterized in that: The judgment condition for failure of the steel box girder lowering posture control is to meet any one of the following four conditions: Condition 1: Synchronicity deviation exceeds the limit: 1) Single point drop displacement deviation: Deviation from the designed drop value>±2mm; 2) Speed ​​asynchrony: The difference in descent speed at each point is greater than 10% of the design value and lasts for more than 2 minutes; Condition 2: Abnormal posture geometry deformation: 1) Overall tilt: When the jacking span is ≤30m, the height difference between the two ends of the beam is greater than 5mm; when the jacking span is greater than 30m, the height difference between the two ends of the beam is greater than 10mm; 2) Local warping: local height difference between adjacent monitoring points>3mm; Condition 3: Temporary support system abnormality: 1) Imbalance of support reaction force: the deviation between the temporary pier reaction force and the theoretical value is greater than 15%, or a sudden drop in single-point reaction force is greater than 20%; 2) Support structure deformation: vertical displacement of temporary pier > 3mm, or horizontal displacement > 2mm; Condition 4: Steel box girder stress exceeds limit: 1) Critical section stress: Measured stress>0.8fy; 2) Sudden change warning: stress change rate > 5MPa / min, or increase > 10%fy within 10 minutes.

7. The safety risk assessment and early warning method based on synchronous jacking construction of steel beams according to claim 1 is characterized in that: The judgment condition for the failure of the guide beam's attitude control when passing the pier is to meet any one of the following three conditions: Condition 1: The guide beam axis is out of limit: 1) The deviation between the center line of the guide beam and the design axis of the pier top is greater than 10mm; 2) The gap between the pier top guide device and the guide beam is greater than 15mm; 3) The length of the front end of the guide beam overhanging the pier top is greater than the design value ±5%; Condition 2: The connection between the guide beam and the main beam is abnormal: 1) The vertical height difference between the guide beam and the main beam joint is greater than 3mm; 2) The stress at the connection part is greater than 0.7fy, or the strain is greater than 1500με; Condition 3: Failure of the temporary support system: the deviation between the support reaction force and the theoretical value is greater than 20%, or the reaction force of a single pier returns to zero.

8. The safety risk assessment and early warning method based on synchronous jacking construction of steel beams according to claim 1 is characterized in that: In step S6, the key risk factors during the steel beam synchronous jacking construction process are set as oil cylinder leakage m , Main beam stress is too large σ b , the guide beam stress is too large σ d , temporary pier stress is too large σ1, temporary pier displacement ΔX , oil leakage at pumping station n , Steel Strand Winding l , first through the finite element software Establish a risk mathematical model, then calculate the partial derivatives, and then use the normalized sensitivity coefficient calculation formula , calculate the sensitivity coefficients of each risk factor and eliminate the dimension effect, among which R 0 is the baseline value of the risk indicator. x i0 is the baseline value of the risk factor.

9. The safety risk assessment and early warning method based on synchronous jacking construction of steel beams according to claim 1, characterized in that: In step S8, for each key monitoring indicator, warning rules with different warning level thresholds, threshold triggering rules, time window rules, anomaly detection rules, and statistical rules are established. The warning levels are 90%, 80%, 70%, and 60% of the theoretical values, respectively, and are divided into lower levels in turn.

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