Method and system for checking pre-flood hidden dangers and evaluating water damage risk of medium and small span bridges

Abstract

The invention relates to the technical field of bridge engineering detection and evaluation, in particular to a method and a system for checking pre-flood hidden dangers and evaluating flood damage risks of medium and small span bridges. According to the flood flow and the bridge inundation event information, obtaining a risk scoring result and a risk grade condition of bridge inundation; bridge structure instability information is collected to establish a bridge structure parameter analysis model, and then a risk scoring result and a risk grade condition of bridge superstructure deviation and bridge superstructure overturning are obtained; acquiring a bridge abutment collapse information set to obtain a risk scoring result and a risk grade condition of bridge abutment collapse and bridgehead panning events; and analyzing risk scoring results and risk grade conditions of bridge submerging, bridge superstructure deviation, bridge superstructure overturning, bridge abutment collapse and bridgehead washing events, and realizing hidden danger investigation and flood risk evaluation before medium-small-diameter cross flood through a systematic evaluation method.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering detection and evaluation, and in particular to a method and system for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges. Background Art

[0002] Bridges are a key component of the transportation network. Bridge risks exist not only during the construction phase, but also throughout the entire operation cycle. Therefore, accurate identification, scientific estimation, and comprehensive evaluation of bridge safety risks are important links in ensuring the safe construction of bridge projects. Bridge water damage is one of the key factors affecting the safe operation of bridges. Existing studies have shown that the generalized reliability analysis of bridges under flood disasters, the mechanism of bridge foundation water damage, and its reinforcement and protection strategies and targeted prevention and control measures are the core content of bridge water damage risk assessment. Once the stability of the bridge structure is damaged, it will bring immeasurable losses. Therefore, how to efficiently and accurately carry out bridge safety risk assessment, especially for small and medium span bridges, build intelligent evaluation models and systems, realize accurate identification and evaluation of risk levels of in-service bridges, and provide scientific and reliable technical support for managers, is an important trend and urgent need in the current technical field.

[0003] Although the existing highway engineering hydrological survey design and calculation specifications provide some basis and calculation methods, there is still a lack of a complete and systematic assessment system and method for bridge water damage risk assessment. Therefore, it is necessary to further study the bridge water damage risk assessment method and related technologies, further build a comprehensive and scientific assessment system, improve the safety and smoothness of bridge projects, and overcome the subjective influence of traditional methods. Summary of the invention

[0004] In view of the defects of existing methods and the shortcomings in practical applications, and the limitations of current methods for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges as well as their shortcomings in practical applications, the present invention proposes an assessment system to standardize the pre-flood hidden danger inspection and risk assessment of water damage of small and medium-span bridges, thereby ensuring the objectivity and accuracy of the assessment results and effectively reducing the influence of human subjective factors. In a first aspect, the present invention provides a method for pre-flood hidden danger inspection and water damage risk assessment for small and medium-span bridges, the method comprising the following steps: obtaining bridge flooding event information, determining the flood flow at the bridge deck elevation based on the bridge flooding event information, and obtaining a risk scoring result and a risk level of bridge flooding according to the flood flow and the bridge flooding event information; collecting bridge structure instability information, establishing a bridge structure parameter analysis model based on the bridge structure instability information and obtaining a parameter analysis result, and obtaining a risk scoring result and a risk level of bridge superstructure displacement and bridge superstructure overturning according to the parameter analysis result; obtaining a set of bridge pier collapse information, and obtaining a risk scoring result and a risk level of bridge pier collapse and bridge head washing events according to the bridge pier collapse information set; and comprehensively analyzing the risk scoring results and risk levels of bridge flooding, bridge superstructure displacement, bridge superstructure overturning, bridge pier collapse and bridge head washing events to achieve pre-flood hidden danger inspection and water damage risk assessment for small and medium-span bridges. The present invention comprehensively considers multiple risk analysis factors such as bridge flooding, superstructure displacement and overturning, pier collapse and bridge head scouring, forming a comprehensive and systematic risk assessment framework, which helps to accurately grasp the overall safety status of the bridge and take preventive measures in time.

[0005] Optionally, the obtaining of bridge flooding event information and determining the flood flow at the bridge deck elevation based on the bridge flooding event information comprises: obtaining bridge flooding event information, the bridge flooding event information including river channel boundary change information of the bridge position river section, bridge hole flow section compression information and bend superelevation inspection information; obtaining the flood flow at the bridge deck elevation based on the bridge position river section river channel boundary change information, the bridge hole flow section compression information and the bend superelevation inspection information; The flood flow satisfies the following relationship:

[0006] in, represents the typical flood flow, represents the Manning roughness coefficient, represents the average width of the river channel, It represents the average water depth of the section. Indicates the riverbed gradient of a river section.

[0007] The present invention analyzes flood flow and frequency through calculation formulas, which is conducive to early warning of potential flood risks and is of great significance for formulating disaster prevention and mitigation measures and ensuring safe operation of bridges.

[0008] Optionally, obtaining the risk scoring result and risk level of bridge inundation according to the flood flow and the bridge inundation event information includes: setting a risk assessment scale for bridge inundation based on the bridge inundation event information, and obtaining a risk scoring result for bridge inundation in combination with the risk assessment scale and the flood flow; determining the risk level of bridge inundation according to the risk scoring result for bridge inundation; The risk scoring result of the bridge flooding satisfies the following relationship:

[0009] in, represents the risk score result of bridge flooding, represents the typical flood frequency, The present invention quantifies the risk of bridge flooding into a specific scoring result, making the risk assessment result more intuitive and easy to understand, and helping to take preventive measures and response plans in a timely manner.

[0010] Optionally, the collecting of bridge structure instability information, establishing a bridge structure parameter analysis model based on the bridge structure instability information and obtaining parameter analysis results comprises: constructing a bridge structure parameter analysis model based on the bridge structure instability information, the bridge structure parameter analysis model comprising a water flow average velocity calculation function, a water flow pressure calculation function, a buoyancy calculation function, a lifting force calculation function and a floating object impact force calculation function; The water flow average velocity calculation function satisfies the following relationship:

[0011] in, It represents the average flow velocity of water on the water-facing surface of the beam. represents the transverse part coefficient of the flow velocity, represents the first vertical distribution coefficient, Indicates the water depth of the channel section. represents the beam section height, represents the second vertical distribution coefficient, represents the third vertical distribution coefficient, It represents the average flow velocity of any measuring line in the cross section. It represents the average flow velocity of the perpendicular line in the cross section; The flow water pressure calculation function satisfies the following relationship:

[0012] in, Surface water pressure, represents the water resistance coefficient of the bridge, It represents the projected area of ​​the bridge perpendicular to the water flow direction. represents the water flow density, It indicates the average flow velocity of water on the water-facing surface of the beam; The buoyancy calculation function satisfies the following relationship:

[0013] in, represents buoyancy, represents the water flow density, represents the acceleration due to gravity, Indicates the volume of water displaced by the bridge; The lifting force calculation function satisfies the following relationship:

[0014] in, Indicates the lifting force, Indicates the width of the bridge bottom. represents the length of the beam perpendicular to the direction of flood action, represents the water flow density, represents the acceleration due to gravity, Indicates the height of water in front of the bridge; The floating object impact force calculation function satisfies the following relationship:

[0015] in, Indicates the impact force of floating objects, represents the gravity of floating objects, Indicates the water flow velocity, represents the acceleration due to gravity, Indicates the impact time.

[0016] The present invention establishes a bridge structure parameter analysis model based on multiple parameters such as average water flow velocity, water pressure, buoyancy, lift force and impact force of floating objects, which can comprehensively and finely evaluate the structural stability of the bridge under flood conditions and help identify potential risks of structural instability.

[0017] Optionally, obtaining the risk scoring result and risk level of the bridge superstructure deviation and the bridge superstructure overturning according to the parameter analysis result includes: analyzing the horizontal force and friction acting on the support based on the parameter analysis result; The horizontal force satisfies the following relationship:

[0018] in, represents the horizontal force that will act on the support, Indicates the water pressure. Indicates the impact force of floating objects; The frictional resistance satisfies the following relationship:

[0019] in, is the friction force acting on the support, represents the friction coefficient, represents the number of forces perpendicular to the support, It represents the vertical reaction of the support under the total load effect.

[0020] The present invention can more accurately assess the risk of displacement and overturning of the bridge superstructure under flood conditions, help to timely solve structural instability problems, and provide technical guarantee for the safe operation of the bridge.

[0021] Optionally, the risk scoring results and risk level of the bridge superstructure displacement and the bridge superstructure overturning obtained according to the parameter analysis results include: obtaining the risk scoring results of the bridge superstructure displacement and the bridge superstructure overturning according to the horizontal force, the friction and the parameter analysis results; determining the risk level of the bridge superstructure displacement and the bridge superstructure overturning according to the risk scoring results of the bridge superstructure displacement and the bridge superstructure overturning; The risk scoring result of the bridge superstructure deviation satisfies the following relationship:

[0022] in, represents the risk score result of the bridge superstructure deflection, represents the typical flood frequency, A risk assessment scale that represents the deflection of the bridge superstructure; The risk scoring result of the overturning of the bridge superstructure satisfies the following relationship:

[0023] in, represents the risk score result of bridge superstructure overturning, represents the typical flood frequency, Represents the risk assessment scale of overturning of bridge superstructure.

[0024] The present invention obtains risk scoring results based on physical principles and mathematical formulas, further ensuring the scientificity and accuracy of the evaluation results and improving the reliability of the evaluation results.

[0025] Optionally, the acquiring of the bridge pier collapse information set and obtaining the risk scoring results and risk level of the bridge pier collapse and bridge head scouring events based on the bridge pier collapse information set include: collecting bridge pier base scouring hidden danger information, bridge abutment foundation scouring hidden danger information and bridge head scouring hidden danger investigation information to acquire the bridge pier collapse information set; analyzing the total scouring depth, the lowest scouring line elevation and the safe burial elevation of the bridge pier based on the bridge pier collapse information set; The total scouring depth satisfies the following relationship:

[0026] in, represents the total scour depth of the bridge pier, Indicates the natural scouring depth of the river section at the bridge location. Indicates the general scouring depth of the river section at the bridge location. Indicates the local scour depth of the river section at the bridge location; The elevation of the lowest scour line satisfies the following relationship:

[0027] in, Indicates the lowest scour line elevation, represents the design water level elevation, Indicates the local scour depth of the river section at the bridge location; The safe embedding elevation satisfies the following relationship:

[0028] in, Indicates the minimum safe embedding elevation of bridge piers and abutment foundations. Indicates the base design elevation, Indicates the minimum burial depth.

[0029] The present invention quantitatively analyzes the total scouring depth, the lowest scouring line elevation and the safe embedding elevation of the bridge piers and abutments, and can more accurately assess the risks of bridge pier collapse and bridgehead scouring events.

[0030] Optionally, the acquiring of a bridge pier collapse information set and obtaining risk scoring results and risk level conditions of bridge pier collapse and bridge head scouring events based on the bridge pier collapse information set include: obtaining risk scoring results of bridge pier collapse and bridge head scouring events based on the total scouring depth, the lowest scouring line elevation and the safe burial elevation; analyzing the risk level conditions of bridge pier collapse and bridge head scouring events based on the risk scoring results of bridge pier collapse and bridge head scouring events; The risk scoring result of the bridge pier collapse satisfies the following relationship:

[0031] in, represents the risk score result of bridge pier collapse, represents the typical flood frequency, Represents the risk assessment scale of bridge pier collapse.

[0032] The present invention introduces a risk assessment scale to improve the accuracy and reliability of the assessment result, which is conducive to early warning of bridge pier collapse and bridge head scouring risks.

[0033] Optionally, the risk scoring result of the bridgehead flushing event satisfies the following relationship:

[0034] in, It represents the risk score result of the bridgehead washing event. represents the typical flood frequency, The invention sets the risk assessment scale and calculation formula for different events, which is helpful to promote the standardization process in the field of bridge risk management and promote the standardization and systematization of risk management methods.

[0035] In the second aspect, the present invention also provides a system for pre-flood hazard inspection and water damage risk assessment of small and medium-span bridges, which can efficiently execute the pre-flood hazard inspection and water damage risk assessment method of small and medium-span bridges provided by the present invention. The above system includes an input device, a processor, an output device and a memory, wherein the input device, the processor, the output device and the memory are interconnected, the memory includes a computer-readable storage medium as described in the first aspect of the present invention, the memory is used to store a computer program, the computer program includes program instructions, and the processor is configured to call the above program instructions. The pre-flood hazard inspection and water damage risk assessment system for small and medium-span bridges provided by the present invention has a compact structure, strong applicability, and greatly improves the operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of the method for troubleshooting and water damage risk assessment of small and medium-span bridges before flood season of the present invention; Figure 2 It is a schematic diagram of the framework of the water damage risk calculation process in the method for troubleshooting and water damage risk assessment of small and medium-span bridges before flood season of the present invention; Figure 3 It is a schematic diagram of the resistance of the upper structure of the beam bridge in the method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges of the present invention; Figure 4 It is a schematic diagram of the natural scour measurement method in the method for troubleshooting and water damage risk assessment of small and medium-span bridges before flood season of the present invention; Figure 5 It is a schematic diagram of the general scour and abutment scour measurement method in the method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges of the present invention; Figure 6 It is a schematic diagram of a local scour measurement method in the method for troubleshooting and water damage risk assessment of small and medium-span bridges before flood season of the present invention; Figure 7 A schematic diagram of the bridge approach encroaching the river channel in the method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges of the present invention; Figure 8 It is a schematic diagram of the direction of water flow affected by the regulation project in the method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges of the present invention; Fig. 9 It is a schematic diagram of vortex scouring at the junction of the bridge head and the slope protection in the method for troubleshooting and water damage risk assessment of small and medium-span bridges before flood season of the present invention; Fig.10 It is a structural schematic diagram of the delay selection system between mine blasting holes of the present invention. DETAILED DESCRIPTION

[0037] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not need to be adopted to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, software or methods are not specifically described.

[0038] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. In addition, it should be understood by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale.

[0039] See also Figure 1In view of the limitations and shortcomings of the current methods for the investigation of hidden dangers and water damage risk assessment of small and medium-span bridges before the flood season, the present invention proposes a systematic risk assessment system and quantitative analysis method, which standardizes and optimizes the process of water damage hidden danger investigation and risk assessment of small and medium-span bridges before the flood season, ensures the objectivity and accuracy of the assessment results, and reduces the influence of subjective factors on the assessment results. The present invention provides a method for the investigation of hidden dangers and water damage risk assessment of small and medium-span bridges before the flood season, and the method comprises the following steps: S1. Obtain bridge flooding event information, determine the flood flow at the bridge deck elevation based on the bridge flooding event information, and obtain the risk score result and risk level of bridge flooding based on the flood flow and bridge flooding event information. The implementation steps and specific contents are as follows: In this embodiment, bridge water damage events mainly include bridge flooding, superstructure instability, pier collapse and other types of events. Before the flood season arrives, hidden dangers inspection and risk assessment need to be carried out for different events.

[0040] The above-mentioned hidden danger inspection work mainly includes the following links: first, data collection to ensure the integrity of bridge-related information; second, on-site surveys and visits to understand the current status of the bridge and the surrounding environment; then, information data analysis to analyze the collected information on different events; finally, water damage event evaluation, score prediction and comprehensive judgment are carried out to further determine the water damage risk and safety level faced by the bridge.

[0041] The process of bridge pre-flood water damage risk assessment includes two parts: typical flood estimation and water damage risk calculation. For bridges whose flood data information has not been updated for more than ten years, typical flood flow must be recalculated; and the process of water damage risk calculation needs to follow a specific process. For the above water damage risk calculation process, please refer to Figure 2 .

[0042] When using the pre-flood hidden danger inspection and water damage risk assessment method for small and medium-span bridges to conduct risk assessment, the typical flood frequency should be selected by referring to the data information in Table 1.

[0043] Table 1 Typical flood frequency table recommended for bridge water damage risk assessment Evaluation Order Typical flood frequency fn 1 1 / 10 2 1 / 25 3 1 / 50 4 1 / 75 5 1 / 100 Based on the information in Table 1, we can know that the typical flood frequency is expressed as When conducting a bridge water damage risk assessment, the typical flood flow selected cannot be lower than the design flood flow. If the actual selected flow is lower than the design value, the design flood flow must be used to assess the risk event to ensure the accuracy and comprehensiveness of the assessment results.

[0044] In an optional embodiment, bridge flooding event information is obtained, and the above-mentioned bridge flooding event information mainly includes the change information of the river channel boundary of the bridge section, the compression situation information of the bridge hole flow section and the superelevation inspection information of the bend.

[0045] Collect information on changes in river boundary at the bridge location.

[0046] The flood carrying capacity of the river section at the bridge location is significantly affected by the riverbed boundary parameters, especially the riverbed roughness coefficient and the riverbed gradient. When the riverbed roughness coefficient increases or the riverbed gradient decreases, the flood carrying capacity of the river section will be weakened. In order to accurately determine the riverbed roughness coefficient of the river section at the bridge location, it is necessary to investigate the riverbed cover layer and vegetation characteristics in the area 10 times the bridge length upstream and downstream of the bridge axis but not less than 500 meters. The relationship between the above characteristics and the riverbed Manning's roughness coefficient can be obtained and confirmed by referring to the Manning's roughness table. For river sections with special geological or ecological characteristics, the research results in the field of Manning's roughness coefficient value technology of natural rivers can be used for reference to obtain more accurate roughness coefficient estimation results. Based on the above investigation and analysis methods, the flood carrying characteristics of the river section at the bridge location can be more comprehensively understood, providing a favorable basis for bridge design and flood risk prediction.

[0047] In order to accurately determine the riverbed gradient of the river section where the bridge is located, it is necessary to measure the riverbed elevation of the deepest point of the section at a position one time the length of the bridge upstream and downstream of the bridge axis. Subsequently, the riverbed gradient of the river section is analyzed using the above two elevation values.

[0048] The calculation formula for the riverbed gradient of a river section in the embodiment satisfies the following relationship:

[0049] in, represents the riverbed gradient of the river section, Indicates the riverbed elevation at the deepest point of the flow section upstream of the bridge axis. Indicates the riverbed elevation at the deepest point of the flow section downstream of the bridge axis. Indicates the length of the river section.

[0050] Collect information on the compression of the bridge opening flow section.

[0051] When investigating the compression of the flow-through section of a bridge opening, it is necessary to pay attention to several major factors that lead to the reduction of the section. These factors include but are not limited to the illegal occupation of the space under the bridge by human activities, the elevation of the riverbed under the bridge due to sediment accumulation, and the clogging of the bridge opening by floating objects in the water flow. The combined effect of these factors further leads to a significant reduction in the effective flow-through section of the bridge opening.

[0052] Obtain information on superelevation inspection of curved roads.

[0053] For bridge construction projects located in curved river sections, it is necessary to measure the curvature radius of the river bend where the bridge is located and the width of the river at the bridge axis. In addition, the superelevation phenomenon caused by the bend can be quantitatively calculated by the corresponding formula. The calculation formula for the superelevation of the bend in the embodiment is as follows:

[0054] in, Indicates the superelevation value of the curve. represents the average width of the river channel, represents the average flow velocity of the cross section, represents the acceleration due to gravity, Indicates the radius of the curve.

[0055] Based on the above-mentioned information on changes in the river boundary of the bridge section, the compression information of the bridge opening flow section and the superelevation inspection information of the curve, the flood flow at the bridge deck elevation is obtained.

[0056] By analyzing the current river boundary conditions and the status of the bridge, the minimum flood flow that causes the bridge deck to be flooded can be determined, and the corresponding occurrence frequency can be assigned to the above flow accordingly.

[0057] Based on the current conditions of the bridge and the river and the typical flood frequency data in Table 1, the embodiment follows the guiding principles of the Highway Engineering Hydrological Survey and Design Specifications (JTG C30-2015) to further calculate the water surface elevation at the bridge location. The relevant calculation steps and contents are as follows: The flood level under typical flood conditions can be directly obtained by consulting the existing water level and flow relationship curve at the bridge section, or by using the typical flood flow calculation formula. The determination of the flood level needs to be based on the measurement results of the average water depth of the section. The above flood level can be obtained by To express.

[0058] The above flood flow, i.e. the calculation formula of typical flood flow, satisfies the following relationship:

[0059] in, represents the typical flood flow, represents the Manning roughness coefficient, represents the average width of the river channel, It represents the average water depth of the section. Indicates the riverbed gradient of the river section; The calculation of the backwater height can be carried out according to the relevant contents of the Highway Engineering Survey and Design Specifications (JTJ062-91). The above backwater height can be calculated using To express.

[0060] The water surface elevation at the bridge location can be calculated from the flood level and the backwater height. For bridges located in river bends, additional consideration should be given to the superelevation value caused by the bend to ensure the accuracy of the water surface elevation calculation. The water surface elevation at the above bridge location can be calculated using Expressed and satisfying the following relationship;

[0061] in, represents the water surface elevation at the bridge location, Indicates flood level, Indicates the height of waterlogging. Indicates the superelevation value of the curve.

[0062] A risk assessment scale for bridge flooding is set based on the above bridge flooding event information, and a risk scoring result for bridge flooding is obtained by combining the risk assessment scale and flood flow; and the risk level of bridge flooding is determined based on the risk scoring result for bridge flooding.

[0063] According to the requirements of the bridge flooding risk grading assessment standard and combined with the bridge flooding event information, an assessment scale for evaluating the bridge flooding risk can be determined. In the embodiment, an assessment standard and scale for quantifying the bridge flooding risk is set based on the bridge flooding risk grading assessment criteria and with reference to the flooding event information experienced by the bridge.

[0064] For information on the grading assessment standards for bridge flooding risks in the embodiments, please refer to Table 2.

[0065] Table 2 Information table of bridge flooding risk classification assessment standards

[0066] In Table 2, represents the typical flood frequency, represents the bridge deck elevation, represents the water surface elevation at the bridge location, Represents the bridge height, where the bridge deck elevation and bridge height can be obtained by measuring related values.

[0067] Table 2 uses This ratio is used as the basis for assessing the risk of bridge flooding. according to The ratio of the flooding risk is divided into four levels, using the assessment scale The values ​​are 1, 2, 3, and 4. The smaller the value, the higher the flooding risk. 0 o'clock is a special case, indicating that an accident has occurred.

[0068] when When the ratio is greater than or equal to 0.6, the assessment scale is 1, indicating that the bridge has no risk of flooding, which means that the bridge deck is far above the water surface even if a flood occurs.

[0069] when When the ratio is between 0.2 and 0.6, the assessment scale is 2, indicating that the risk of bridge flooding is very low. At this time, the bridge deck is still above the water surface by a certain distance, but relative to the risk-free state.

[0070] when When the ratio is between 0 and 0.2, the assessment scale is 3, indicating that the risk of bridge flooding is very high, which means that the bridge deck is very close to the water surface and floods can easily submerge the bridge deck.

[0071] when When the ratio is less than or equal to 0, the assessment scale is 4, indicating that the bridge has been flooded, indicating that the water level is higher than the bridge deck and the bridge has been flooded.

[0072] In practical applications, based on The ratio and the assessment standards in Table 2 can be used to quickly determine the flooding risk level of the bridge, which helps to take necessary early warning and response measures in a timely manner to ensure the safety of the bridge during floods and provides a powerful tool for bridge flooding risk assessment.

[0073] Based on the bridge flooding risk grading assessment standard information provided in Table 2, the scoring result of the bridge flooding risk can be obtained. The risk scoring result of the bridge flooding in the embodiment satisfies the following relationship:

[0074] in, represents the risk score result of bridge flooding, represents the typical flood frequency, Represents the risk assessment scale for bridge flooding.

[0075] The risk score result of bridge flooding is determined by multiplying the typical flood frequency by the risk assessment scale of bridge flooding. In the embodiment, standardized assessment standards and relationship formulas are used to ensure the objectivity and fairness of the assessment process of bridge flooding risk, reduce the influence of human factors, and more accurately calculate the risk score of bridge flooding, thereby improving the reliability of the assessment result. At the same time, the risk score of bridge flooding is quickly and accurately calculated, which helps decision makers take corresponding preventive measures or formulate emergency plans according to the risk score.

[0076] The assessment of the flooding risk level of a bridge should be carried out in accordance with the standards in Table 3.

[0077] Table 3 Bridge flooding risk level table

[0078] Based on the information in Table 3, it can be seen that the anti-flooding risk level of the bridge is based on the risk score of bridge flooding. When the scoring result When the score is less than or equal to 0.25, the flooding risk level of the bridge is rated as level 1, i.e. high risk; when the score is When the score is between 0.25 and 0.4, the flooding risk level of the bridge is rated as Level 2, i.e. medium risk; when the score is between 0.25 and 0.4, the flooding risk level of the bridge is rated as Level 2, i.e. medium risk. When it is greater than or equal to 0.4, the bridge's anti-flooding risk level is rated as level three, which means low risk.

[0079] Furthermore, the risk scoring and level situation analysis method for bridge flooding in this embodiment is only an optional condition of the present invention. In one or some other embodiments, the risk scoring and level situation analysis method for bridge flooding can be adjusted according to the information characteristics and risk scoring requirements of the bridge flooding event, which helps to ensure the accuracy and practicality of the evaluation results, while promoting the development and progress of risk assessment technology in the field of bridge engineering.

[0080] S2. Collect the instability information of the bridge structure, establish a bridge structure parameter analysis model based on the instability information of the bridge structure and obtain the parameter analysis results, and obtain the risk scoring results and risk level of the bridge superstructure displacement and bridge superstructure overturning according to the above parameter analysis results. The specific steps and implementation contents are as follows: First, it is necessary to collect information on the instability of the bridge structure.

[0081] When conducting a bridge safety assessment, it is necessary to collect information about the stability of the bridge structure. In the embodiment, the flow velocity and density of the water flow and the impact of floating objects are mainly checked.

[0082] If the riverbed gradient of the current river channel is larger than the natural state before the bridge was built, or the riverbed roughness coefficient is reduced, then under the same flow conditions, the flow rate of the river water may be faster. The same method mentioned above can be used to investigate the riverbed gradient and roughness coefficient. For bridges that have experienced debris flows before and after construction, the density of the debris flow can be estimated by measuring the volume of debris flow residues or conducting on-site investigations and visits.

[0083] In addition, the risk of floating objects hitting the bridge needs to be checked. If there is a riverside town or parking lot within 1 km upstream of the bridge, it is necessary to assess whether the relevant area is at risk of being flooded. If there is a corresponding risk, it must be considered that during floods, vehicles may float with the water flow and cause additional impact forces on the bridge.

[0084] Similarly, if there is a dock within 1 km upstream of the bridge, it is necessary to estimate the impact force on the bridge based on the type and level of the docked ships. At the same time, if there is a forest farm or timber storage yard upstream, it is necessary to estimate the possible impact force on the bridge based on the size of the timber.

[0085] Then, a bridge structure parameter analysis model is constructed based on the bridge structure instability information. The bridge structure parameter analysis model in the embodiment mainly includes a water average flow velocity calculation function, a water pressure calculation function, a buoyancy calculation function, a lifting force calculation function, and a floating object impact force calculation function. The specific contents are as follows: The core of bridge impact instability risk assessment is to analyze the relationship between the resistance of the bridge superstructure and the force of the flood. If the force generated by the flood exceeds the resistance of the bridge superstructure, then when the corresponding bridge encounters the corresponding flood, its superstructure is at risk of instability. In the embodiment, a beam bridge is taken as an example. For the schematic diagram of the beam bridge superstructure resistance, please refer to Figure 3 , where xyo is the schematic coordinate system, Indicates the tipping angle.

[0086] Further analysis shows that the key factor leading to the instability of the bridge superstructure is the excessive force of the water flow. The loads imposed by the water flow on the bridge superstructure mainly include the pressure generated by the flowing water, the upward force, the buoyancy that makes the structure float, and the impact force generated when floating objects collide. In order to quantify the relevant water flow forces, this embodiment constructs a bridge structure parameter analysis model based on the instability information of the bridge structure.

[0087] Based on the instability information of the bridge structure, the average flow velocity of the water on the water-facing surface of the beam is analyzed. The calculation function of the average flow velocity of the water needs to satisfy the following relationship:

[0088] in, It represents the average flow velocity of water on the water-facing surface of the beam. represents the transverse part coefficient of the flow velocity, represents the first vertical distribution coefficient, Indicates the water depth of the channel section. represents the height of the beam section, represents the second vertical distribution coefficient, represents the third vertical distribution coefficient, It represents the average flow velocity of any measuring line in the cross section. It represents the average flow velocity of the perpendicular line in the cross section; Regarding the transverse velocity coefficient n, its value range is defined between 0.975 and 1.03. The above coefficient reflects the lateral distribution characteristics of water flow velocity in relevant calculations, that is, the transverse velocity coefficient is between 0.975 and 1.03, which can be used to adjust or indicate the change of water flow velocity in the lateral direction on the water-facing surface of the bridge beam.

[0089] The first vertical distribution coefficient satisfies the following relationship:

[0090] in, represents the first vertical distribution coefficient, is the Froude number.

[0091] The second vertical distribution coefficient satisfies the following relationship:

[0092] in, represents the second vertical distribution coefficient, is the Froude number.

[0093] The third vertical distribution coefficient satisfies the following relationship:

[0094] in, represents the third vertical distribution coefficient, is the Froude number.

[0095] The above Froude number satisfies the following relationship:

[0096] in, represents the average flow velocity of the cross section, represents the acceleration due to gravity, Indicates the water depth of the channel section.

[0097] The water pressure calculation function satisfies the following relationship:

[0098] in, Surface water pressure, represents the water resistance coefficient of the bridge, It represents the projected area of ​​the bridge perpendicular to the water flow direction. represents the water flow density, It indicates the average flow velocity of water on the water-facing surface of the beam; The numerical range of the above-mentioned bridge water resistance coefficient needs to be defined between 2.0 and 2.2, which means that in the relevant water flow analysis, the obstruction of the bridge to the water flow can be quantified by the bridge water resistance coefficient K, and the coefficient value is not less than 2.0 and not more than 2.2.

[0099] The buoyancy calculation function satisfies the following relationship:

[0100] in, represents buoyancy, represents the water flow density, represents the acceleration due to gravity, Indicates the volume of water displaced by the bridge; The lift force calculation function satisfies the following relationship:

[0101] in, Indicates the lifting force, Indicates the width of the bridge bottom. represents the length of the beam perpendicular to the direction of flood action, represents the water flow density, represents the acceleration due to gravity, Indicates the height of water in front of the bridge; In this embodiment, the relevant data of the height of the waterlogging in front of the bridge can adopt the waterlogging value that has been calculated previously.

[0102] The floating object impact force calculation function satisfies the following relationship:

[0103] in, Indicates the impact force of floating objects, represents the gravity of floating objects, Indicates the water flow velocity, represents the acceleration due to gravity, Indicates the impact time.

[0104] The unit of gravity of floating objects is kilonewton (kN). This gravity value needs to be determined based on the actual situation of floating objects in the river or through field investigation.

[0105] The estimation of the impact time should be determined based on the existing actual data. If there is a lack of specific data, a reasonable time value can be set, which can be 1 second. In addition, the instability damage that may be caused by water flow to the bridge superstructure mainly includes the displacement and overturning of the bridge structure, which is specifically manifested in the displacement phenomenon and overturning risk of the structure.

[0106] Through the calculation function of average water velocity, water pressure, buoyancy, lifting force and floating object impact force in the bridge structure parameter analysis model, the analysis results of different bridge structure parameters can be accurately obtained based on the above parameter calculation functions. The above calculation functions are mainly based on the principles of fluid mechanics, structural mechanics, etc., and can comprehensively consider the influence of various factors such as water velocity, pressure, buoyancy, impact force, etc. on the bridge structure, thereby providing more accurate parameter analysis results. Based on this, we can more clearly understand the stress conditions of the bridge under different working conditions, which helps to improve the authenticity of the bridge stability and safety analysis results.

[0107] Then, based on the above parameter analysis results, the horizontal force and friction acting on the support are analyzed. The specific contents are as follows: Based on the analysis results of different bridge structure parameters, the relationship between the horizontal force acting on the support and the friction resistance is further explored. Once the horizontal force on the support exceeds the limit of its friction resistance, the support will slide, which will cause the beam to drift or dislocate.

[0108] In the embodiment, a horizontal force analysis function is established based on the water pressure, the impact force of floating objects and related data information. The horizontal force analysis function needs to satisfy the following relationship:

[0109] in, represents the horizontal force that will act on the support, Indicates the water pressure. Indicates the impact force of floating objects; Furthermore, the frictional resistance satisfies the following relationship:

[0110] in, is the friction force acting on the support, represents the friction coefficient, represents the number of forces perpendicular to the support, It represents the vertical reaction of the support under the total load effect.

[0111] Calculating the horizontal forces and friction acting on the supports can more accurately predict the behavior of the bridge under different working conditions, including but not limited to the sliding tendency of the supports and the stability of the beams, which helps to make more reasonable decisions during the design and construction process and effectively analyze the overall performance and safety of the bridge.

[0112] Finally, the risk scoring results of bridge superstructure displacement and bridge superstructure overturning are obtained according to the results of horizontal force, friction and parameter analysis; and the risk level of bridge superstructure displacement and bridge superstructure overturning is determined according to the risk scoring results of bridge superstructure displacement and bridge superstructure overturning.

[0113] In an optional embodiment, the assessment level of the bridge superstructure offset risk is determined according to the content specified in the bridge superstructure offset risk grading assessment standard, and the bridge superstructure offset risk grading assessment information is further improved based on the horizontal force and friction resistance on the support, please see Table 4.

[0114] Table 4 Bridge superstructure deflection risk classification standard table

[0115] In Table 4, represents the horizontal force that will act on the support, Represents the frictional resistance acting on the support.

[0116] Rating scale according to The ratio of the bias risk is divided into four levels, using the assessment scale The value is 1, 2, 3, or 4, where a larger value indicates a higher risk of deviation.

[0117] when When the ratio is between 0 and 0.3, the assessment scale is 1, indicating that there is no risk of displacement of the bridge superstructure.

[0118] when When the ratio is between 0.3 and 0.6, the assessment scale is 2, indicating that the risk of bridge superstructure displacement is very low.

[0119] when When the ratio is between 0.6 and 1.0, the assessment scale is 3, indicating that the risk of bridge superstructure deviation is very high and corresponding measures need to be taken in time to prevent the occurrence of deviation.

[0120] when When the ratio is greater than or equal to 1.0, the assessment scale is 4, indicating that the bridge superstructure has experienced a displacement accident or is in an emergency state of imminent displacement.

[0121] In practical applications, the horizontal force on the bridge superstructure and the friction on the supports can be calculated, and combined with the evaluation criteria in Table 4, the risk level of bridge excursion can be quickly determined, which helps to take necessary maintenance and reinforcement measures in a timely manner to ensure the stability and safety of the bridge.

[0122] Taking into account the typical flood frequency and the excursion risk assessment scale, the risk scoring result of the excursion of the bridge superstructure satisfies the following relationship;

[0123] in, represents the risk score result of the bridge superstructure deflection, represents the typical flood frequency, A risk assessment scale that represents the deflection of the bridge superstructure; By determining the displacement risk assessment scale according to the provisions of Table 4 and combining it with the specific flood frequency, the displacement risk of the bridge superstructure when facing different flood frequencies can be analyzed, that is, the risk score result of the displacement of the bridge superstructure can be obtained.

[0124] The assessment of the risk level of instability of the bridge superstructure should be carried out in accordance with the relevant provisions in Table 5.

[0125] Table 5 Risk level table for preventing superstructure instability

[0126] Based on Table 5 and related information, the instability risk of the bridge superstructure can be assessed.

[0127] The risk score results of the bridge superstructure deflection can be compared with the score range in Table 5. If the risk score result of the bridge superstructure deflection is less than or equal to 0.25, the anti-instability risk level of the bridge superstructure is rated as level 1; If the risk score result of the bridge superstructure deflection is between 0.25 and 0.4 (including 0.25 but excluding 0.4), the risk level is rated as Level 2. If it is greater than or equal to 0.4, the risk level can be assessed as level three. The above assessment method provides a clear and quantitative standard, which helps to accurately evaluate and predict the resistance capacity of the bridge superstructure when facing the risk of instability.

[0128] In an optional embodiment, the buoyancy of still water will weaken the anti-overturning ability of the beam, while the horizontal impact force exerted by the flood on the bridge will produce a huge lateral overturning moment. At this time, the superstructure of the bridge faces the risk of overturning damage. In order to quantify the above risk, the structural stability moment is introduced in the embodiment and structural overturning moment , and determine the assessment scale of the overturning risk of bridge superstructures based on the relevant provisions of the bridge superstructure overturning risk classification assessment standard.

[0129] For the above-mentioned bridge superstructure overturning risk classification assessment information, please refer to Table 6.

[0130] Table 6 Bridge superstructure overturning risk classification standard table

[0131] Table 6 represents the structural stability moment, Represents the overturning moment of the structure.

[0132] Two moments are used in Table 6 as the basis for assessing the overturning risk of the bridge superstructure. according to The capsizing risk is divided into four levels using the assessment scale It is represented by values ​​of 1, 2, 3, or 4, where a larger value indicates a higher risk of capsizing.

[0133] when When the ratio is between 0 and 0.3, the assessment scale is 1, indicating that there is no risk of overturning of the bridge superstructure.

[0134] when When the ratio is between 0.3 and 0.6, the assessment scale is 2, indicating that the risk of overturning of the bridge superstructure is very low.

[0135] when When the ratio is between 0.6 and 1.0, the assessment scale is 3, indicating that the risk of overturning of the bridge superstructure is very high and requires close attention and appropriate measures.

[0136] when When the ratio is greater than or equal to 1.0, the assessment scale is 4, indicating that the bridge superstructure is on the verge of overturning or an accident has already occurred.

[0137] In practical applications, the overturning risk level of the bridge can be quickly determined according to the assessment criteria in Table 6, so that corresponding maintenance and reinforcement measures can be taken to ensure the safe operation of the bridge.

[0138] Due to the comparative relationship between the reduction of the anti-overturning moment caused by the still water buoyancy and the lateral overturning moment generated by the horizontal impact force of the flood, the information in Table 6 can be used in the embodiment to evaluate the overturning risk of the bridge superstructure.

[0139] The above risk scoring results of bridge superstructure overturning satisfy the following relationship:

[0140] in, represents the risk score result of bridge superstructure overturning, represents the typical flood frequency, Represents the risk assessment scale of overturning of bridge superstructure.

[0141] The capsizing risk assessment scale is determined based on the information in Table 6 and relevant regulations.

[0142] The scoring results of the overturning risk of bridge superstructures are mainly determined based on the typical flood frequency and the relevant risk assessment scale. The risk scoring results of bridge superstructure overturning represent the quantitative assessment results of the overturning risk of bridge superstructures when facing different flood frequencies.

[0143] The assessment of the overturning risk level of the bridge superstructure should be carried out in accordance with the relevant provisions in Table 7.

[0144] Table 7 Risk level table for preventing superstructure instability

[0145] Based on the information in Table 7, if the risk score result of bridge superstructure overturning is If the risk score of the bridge superstructure overturning is less than or equal to 0.25, the risk level of the bridge superstructure overturning resistance is rated as level 1, indicating a low risk. If the risk score result of the bridge superstructure overturning is between 0.25 and 0.4 (including 0.25 but not including 0.4), the risk level is rated as Level 2, indicating moderate risk. If it is greater than or equal to 0.4, the risk level is rated as Level 3, indicating a higher risk. This rating system provides a clear quantitative standard that helps to better understand and evaluate the safety status of bridges when facing the risk of superstructure overturning.

[0146] Furthermore, in the present embodiment, the specific analysis steps of the displacement and overturning of the bridge superstructure are merely an optional condition of the present invention. In one or some other embodiments, the specific analysis steps of the displacement and overturning of the bridge superstructure may be optimized according to the actual situation of the instability of the bridge structure and the different attribute characteristics of the bridge structure parameters. Different bridge structures have different instability modes and structural parameters. The optimization of the analysis steps enables the pre-flood hidden danger inspection and water damage risk assessment method for small and medium-span bridges of the present invention to adapt to various complex situations, thereby improving the applicability and practicality of the above-mentioned evaluation method.

[0147] S3. Obtain a set of bridge pier collapse information, and obtain risk scoring results and risk levels of bridge pier collapse and bridgehead scouring events based on the bridge pier collapse information. The specific implementation steps and related contents are as follows: Collect information on scour hazards at the base of bridge piers, scour hazards at the foundation of abutments, and scouring hazards at the bridge head to obtain a set of information on bridge pier collapse; analyze the total scour depth, lowest scour line elevation, and safe burial elevation of bridge piers based on the above-mentioned bridge pier collapse information set.

[0148] Collect information on hidden dangers of scour at the base of bridge piers.

[0149] The core of the investigation of scour risk information of bridge pier base is to identify and deal with the risks brought by natural scour, general scour and local scour of the riverbed. The above scour phenomena work together to form the lowest scour line of the bridge pier facing the flow surface, and the total scour depth is the sum of the three scour depths.

[0150] Factors that need to be paid attention to for the natural scour hazards of bridge piers include but are not limited to the current status of scour depth, the existence of sand mining pits, changes in the erosion base level at the river section outlet, and the evolution of the river bend. In order to effectively investigate and collect relevant hazard information, the following methods can be adopted: A natural scour depth measurement method is used in the embodiment, see Figure 4 .

[0151] based on Figure 4 It can be seen that the measurement method is to measure the elevation of the deepest point of the river section at a position 1 times the length of the bridge pier upstream and downstream of the bridge axis; then, compare the elevation with the elevation of the deepest point of the same section before the bridge was built to calculate the elevation difference; finally, take the average of the elevation difference between the upstream and downstream sections to obtain an estimated value of the natural scour depth.

[0152] On-site surveys are required within half a kilometer upstream and downstream of the bridge axis to confirm whether there are pits formed by sand mining activities. Once a sand mining pit is found, its maximum depth must be measured immediately to assess its impact on the stability of the bridge piers.

[0153] For the riverbed within 1 km downstream of the bridge axis, special attention should be paid to whether there are stepped non-rock riverbed elevation drop points. Such drop points may be formed by natural processes such as water scouring and riverbed sediment transportation. After the drop point is found, the riverbed elevation difference upstream and downstream of the mutation point should be measured to understand the changes in the riverbed morphology.

[0154] For bridges located in curved river sections, it is necessary to accurately measure the curvature radius at the top of the curve and the natural river width. The above parameters are crucial for evaluating the stability and anti-scouring ability of the bridge in the curved river section.

[0155] In terms of general scour hazards of bridge piers, it is necessary to pay attention to the current status of scour depth, whether the bridge hole is compressed, whether the gradation of the riverbed cover has changed, etc. Relevant factors may affect the scour resistance of the bridge piers. Therefore, detailed investigation and measurement are needed to timely discover and deal with potential scour hazards.

[0156] The general scour depth measurement method is also used in the examples. Figure 5 , where s represents the clear span.

[0157] based on Figure 5 Information Analysis The measurement steps of general scour depth are: first determine the position of the river channel deep line in the bridge hole and measure the elevation of the middle point of this position. Then, calculate the difference between this elevation and the average elevation of the two measuring points of natural scour. The above difference is the general scour depth at the bridge pier.

[0158] The compression of the flow-passing section of the bridge opening needs to be investigated. The content of this investigation is the same as that described above, and it mainly focuses on whether the bridge opening is compressed and the degree of compression.

[0159] In order to further understand the gradation of the riverbed cover, it is necessary to conduct measurements. This measurement process can refer to the river bed sediment and bed sand test procedures (SL 43-92) to further ensure the accuracy and reliability of the measurement results.

[0160] The local flushing measurement method is also used in the examples. Figure 6 .

[0161] In order to accurately determine the local scour depth of the bridge pier, the embodiment follows Figure 6 The measurement operation is carried out according to the method shown. That is, at least three measuring points are selected on the side of each pier near the pier column on the flow-facing surface, and their elevations are recorded. Then, the elevations of the general scour measurement points are subtracted from the elevations of these measuring points, and the maximum value of the obtained elevation difference is identified as the local scour depth of the pier.

[0162] For non-cylindrical single pier structures, it is necessary to pay attention to the measurement of its water flow attack angle. The above measurement process involves the determination of the angle between the longitudinal axis of the pier and the deep channel line of the upstream river. This angle is the water flow attack angle.

[0163] For bridges whose pier shapes have changed due to damage or reinforcement, the embodiment refers to the appendix information in the Highway Engineering Hydrological Survey and Design Specification (JTG C30-2015) to determine their pier shape coefficients and calculated widths, which helps to accurately assess the scour risk of the piers.

[0164] The same approach as for general scour risk investigation of bridge piers is used when measuring the gradation of the riverbed cover. This step aims to understand the composition and distribution of the riverbed material in order to better predict and assess the scour of the bridge piers.

[0165] Obtain information on hidden dangers of scour of bridge abutment foundations.

[0166] The investigation and acquisition of the scouring hazard information of the abutment foundation in the embodiment involves multiple aspects, which mainly include the scouring caused by the natural evolution of the riverbed, general scouring and local scouring, which together determine the total scouring depth of the abutment.

[0167] The factors that need to be paid attention to for the natural scour hazards of bridge abutments are similar to those for bridge piers, including the current status of scour depth, the existence of sand mining pits, changes in the erosion base level at the river section outlet, and the evolution of river bends. The specific implementation methods for checking related hazards can refer to the inspection methods and data collection processes for natural scour hazards of bridge piers.

[0168] The inspection of general scour hazards of bridge abutments also has many similarities with that of bridge piers, among which the main concerns are the current status of scour depth, whether the bridge hole is compressed, and whether the gradation of the riverbed cover layer has changed. The inspection methods and data acquisition methods of the above hazards can also refer to the general scour hazards of bridge piers.

[0169] More detailed investigation measures are needed to address the hidden dangers of local scouring on bridge abutments. First, Figure 6 The method shown in the figure is used to measure the local scour depth of the abutment foundation, that is, to determine the elevation difference between the deepest point in the scour pit and the riverbed outside the scour pit. Secondly, it is necessary to measure the angle of attack of the water flow near the abutment. The above steps are the same as the measurement of the angle of attack of the water flow in the general scour hazard inspection of the pier. For bridges whose abutment shape has changed due to damage or reinforcement, the relevant tables in the Highway Engineering Hydrological Survey and Design Code (JTG C30-2015) should be referred to to determine their abutment shape coefficient. In addition, it is necessary to measure the flow blocking width corresponding to the abutment and embankment, and evaluate the changes in the gradation of the riverbed cover layer. The above inspection steps and technical methods are similar to the corresponding steps for local scour hazards of the pier.

[0170] Collect information on the inspection of hidden dangers of bridgehead cleaning.

[0171] For the bridgehead encroaching on the river channel in the embodiment, please refer to Figure 7 .

[0172] Figure 7 The bridge shown has the problem of bridgehead encroaching the river channel, and it is necessary to investigate the hidden dangers of bridgehead scouring and collect information, which includes two aspects: on the one hand, assess the potential risk of flood scouring on the bridgehead approach, which involves analyzing whether the flood may directly impact and affect the approach roadbed of the bridgehead under a specific flow rate and velocity, thereby causing safety hazards. On the other hand, check whether the junction area between the approach and the upstream and downstream river banks is prone to form vertical axis vortices and cause scouring. The vertical axis vortex is the rotational movement generated by the water flow under specific terrain conditions. The above movement will erode the soil of the riverbank and the bridgehead, resulting in structural instability. Therefore, it is necessary to pay close attention to whether there are conditions for the formation of vortices in the junction area, and whether the vortex may cause scouring damage to the bridgehead. Based on this, the hidden dangers of bridgehead scouring can be more comprehensively assessed, and corresponding prevention and control measures can be taken to ensure the safety and stability of the bridge.

[0173] The potential risks of water flow directly impacting the bridge approach mainly include: due to the upstream river channel regulation structure or flood control facilities, especially the layout changes of groins and diversion dikes, as well as the natural swing of the main river channel, the mainstream flow direction of the flood may change. For the changes in the mainstream flow direction, please refer to Figure 8 When faced with such risks, the lowest vertical height at the toe of the approach waterfront surface should be measured.

[0174] Where the approach meets the upstream and downstream riverbanks, if there is a potential risk of whirlpool scouring, it is mainly because the necessary diversion dikes on the upstream or downstream sides are not built, or the original diversion dikes have been damaged. For a schematic diagram of whirlpool scouring, please refer to Fig. 9 When faced with the above situation, it is necessary to measure the lowest vertical height where the approach road meets the river bank in order to conduct subsequent risk assessment and safety prediction.

[0175] In this embodiment, the steps for calculating the local scour depth of the river section at the bridge location based on the bridge pier collapse information set are as follows: For the local scour depth at the bridge pier, the formula in the Highway Engineering Hydrological Survey and Design Code (JTG C30-2015) can be referred to for calculation.

[0176] The local scour depth at the abutment can be calculated using the formula in the same specification.

[0177] For scour calculations under special circumstances, you can also refer to the relevant content of the specifications.

[0178] In addition, the total scour depth of bridge piers can also be obtained through corresponding calculation methods.

[0179] The total scouring depth in the embodiment satisfies the following relationship:

[0180] in, represents the total scour depth of the bridge pier, Indicates the natural scouring depth of the river section at the bridge location. Indicates the general scouring depth of the river section at the bridge location. Indicates the local scour depth of the river section at the bridge location; The lowest scour line elevation satisfies the following relationship:

[0181] in, Indicates the lowest scour line elevation, represents the design water level elevation, Indicates the local scour depth of the river section at the bridge location; The safe burial elevation satisfies the following relationship:

[0182] in, Indicates the minimum safe embedding elevation of bridge piers and abutment foundations. Indicates the base design elevation, Indicates the minimum burial depth.

[0183] Finally, the risk scoring results of bridge pier collapse and bridge head scouring events were obtained based on the total scouring depth, the lowest scouring line elevation and the safe burial elevation. At the same time, the risk levels of bridge pier collapse and bridge head scouring events were analyzed based on the risk scoring results of bridge pier collapse and bridge head scouring events.

[0184] In this embodiment, risk assessment plays an important role in preventing bridge pier collapse events. When conducting risk assessment of bridge collapse under the current scour depth condition, it is first necessary to accumulate the current depths of natural scour, general scour, and local scour experienced by the bridge pier to obtain the total scour depth, and calculate the elevation of the lowest scour line accordingly. Subsequently, the elevation is compared with the lowest safe burial elevation. If the elevation of the lowest scour line is lower than the safety standard, it means that the current bridge is in an unsafe state and there is a high risk of collapse, and protective measures need to be taken immediately.

[0185] When conducting a risk assessment of bridge pier collapse due to excessive scouring, it is necessary to calculate the natural scouring depth, general scouring depth, and local scouring depth of the bridge piers based on the current river and bridge structure conditions and combined with different flood frequencies. The specific flood conditions that lead to bridge pier collapse can be determined through the above process.

[0186] This embodiment follows the following principles when calculating the natural scour depth of the river section at the bridge location: If there is a sand mining pit within half a kilometer upstream and downstream of the bridge axis, the general scour depth is based on the current maximum depth of the sand mining pit. If there is a stepped non-rock riverbed with a sudden drop in riverbed elevation within 1 kilometer downstream of the bridge axis, the natural scour depth is the difference between the current downstream natural scour measurement point elevation and the downstream riverbed sudden drop point elevation. For the natural scour depth caused by the evolution of the bend, the relevant formula in the Highway Engineering Hydrological Survey and Design Specifications (JTG C30-2015) can be referred to for calculation.

[0187] For the above risk classification assessment information on the possible excessive scouring of bridge piers and abutments, which may lead to pier collapse, please refer to Table 8 Table 8 Risk grading assessment standard for bridge pier collapse caused by excessive scouring

[0188] Table 8 Indicates the minimum safe embedding elevation of bridge piers and abutment foundations. Indicates the lowest scour line elevation.

[0189] Based on the analysis of pier collapse risk classification and bridge pier collapse information, it can be seen that in the above classification and assessment standards, two key elevation ratios are used as the basis for risk assessment. According to these ratios, the risks are divided into four levels and the assessment scales are used respectively. The numerical values ​​1, 2, 3, and 4 are used to represent it.

[0190] when When the ratio is between 0 and 0.3, the assessment scale is 1, indicating no risk, which means that the foundation depth of the piers and abutments is deep enough, and even if scouring occurs, it will not pose a threat to the stability of the bridge.

[0191] when When the ratio is between 0.3 and 0.6, the rating scale is 2, indicating that the risk is very low. Although scour may have a certain impact on the bridge, overall, the stability of the bridge can still be guaranteed.

[0192] when When the ratio is between 0.6 and 1.0, the assessment scale is 3, indicating a very high risk. This means that the scouring has approached or reached the foundation burial depth of the piers and abutments, and the stability of the bridge may be seriously threatened.

[0193] when When the ratio is greater than or equal to 1.0, the assessment scale is 4, indicating that an accident has occurred, indicating that the scouring has exceeded the foundation burial depth of the piers and abutments, and the bridge may have collapsed or is about to collapse.

[0194] Therefore, by comparing The ratio of and reference to the risk grading standards in Table 8 can accurately assess the risk of bridge pier collapse due to excessive scouring, which is crucial for the safe management and maintenance of bridges and helps relevant personnel take timely measures to reduce risks and ensure the safe operation of bridges.

[0195] The risk scoring results of the above bridge pier collapse satisfy the following relationship:

[0196] in, represents the risk score result of bridge pier collapse, represents the typical flood frequency, Represents the risk assessment scale of bridge pier collapse.

[0197] The risk assessment scale of pier collapse can be determined based on the information in Table 8 and relevant regulations.

[0198] The risk scoring results of bridge pier collapse are mainly determined based on typical flood frequencies and related risk assessment scales. The risk scoring results of bridge pier collapse take into account possible flood frequencies, including low-frequency, medium-frequency and high-frequency flood events. By comparing the flood frequencies considered in the design of bridge piers with the actual flood frequencies that may occur, the stability and safety of the piers under extreme weather conditions can be evaluated.

[0199] The risk assessment of bridge pier collapse resistance should be carried out in accordance with the relevant provisions in Table 9.

[0200] Table 9 Risk level of bridge pier collapse

[0201] Similarly, the risk assessment of the bridgehead scouring event requires the following risk assessment and analysis steps: First, based on the relevant information set and method, the water surface height at the bridge location under typical flood frequency can be calculated. ,This step is the basis for evaluating the impact of flood on bridge head scouring.

[0202] Next, in order to understand the susceptibility of the approach and the river bank to scour, it is necessary to obtain the lowest elevation of the slope foot of the approach facing the water, or the lowest elevation at the junction of the approach and the river bank through field measurements, and record it as The above elevation data are crucial for assessing whether floods will cause scouring risks to the bridge head.

[0203] Finally, according to the obtained water surface elevation, minimum elevation and the risk assessment criteria in Table 10, the risk assessment scale of the bridge head scouring event can be determined, which can intuitively reflect the risk level of the bridge head scouring event under different flood frequencies and scouring conditions.

[0204] For the risk classification information of the bridgehead flushing event in the embodiment, please refer to Table 10.

[0205] Table 10 Risk grading standard for bridgehead scouring incidents

[0206] Table 10 It indicates the lowest elevation of the toe of the approach facing the water or the lowest elevation of the junction between the approach and the river bank. Indicates the water surface elevation at the bridge location when typical flood frequency occurs.

[0207] In the embodiment, the risk of bridge head scouring events is graded and assessed based on the information in Table 10. Table 10 provides a clear risk grading and assessment standard for bridge head scouring events, which divides the risk level according to two key elevation ratios. The risk is divided into two levels according to the ratio, and the assessment scales are used respectively. The values ​​1 and 4 are used to represent it.

[0208] when When the ratio is between 0 and 1.0, the assessment scale is 1, indicating that no scouring event occurs at the bridge head, which means that under typical flood frequencies, the elevation of the waterfront slope foot or the riverbank junction of the bridge head is higher than or equal to the water surface elevation, so scouring events will not occur.

[0209] when When the ratio is greater than or equal to 1.0, the assessment scale is 4, indicating that a bridge head scouring event has occurred. This means that under typical flood frequencies, the elevation of the waterfront slope foot or the riverbank junction of the bridge head is lower than the water surface elevation, so scouring events will occur, which may cause damage to the bridge structure.

[0210] By comparison By referring to the risk grading criteria in Table 10, it is possible to quickly and accurately determine whether a scouring event will occur at the bridge head under a typical flood frequency. The above evaluation method is crucial for the safety management and maintenance of bridges, because scouring events may lead to the exposure and weakening of the bridge foundation, thereby threatening the overall stability of the bridge. Therefore, it is necessary to take necessary preventive and response measures in a timely manner, such as strengthening the toe of the water-facing surface and improving riverbank protection, which is of great significance for reducing the risk of scouring events at the bridge head.

[0211] The risk scoring result of the above-mentioned bridgehead washing event in the embodiment satisfies the following relationship:

[0212] in, It represents the risk score result of the bridgehead washing event. represents the typical flood frequency, Represents the risk assessment scale of bridgehead scouring events.

[0213] The risk assessment scale for bridgehead scouring events was determined based on the information in Table 10 and relevant regulations.

[0214] The above risk score calculation formula for bridge head scouring events takes into account the typical flood frequency and the risk assessment scale of bridge head scouring events. These two key factors mean that the risk score not only takes into account the possibility of flood occurrence, that is, the flood frequency, but also takes into account the actual threat level posed by the flood to the bridgehead, that is, the risk assessment scale. The above calculation formula makes the risk score results more comprehensive and accurate.

[0215] Furthermore, the analysis method of bridge pier collapse and bridge head washing events in the present embodiment is merely an optional condition of the present invention. In one or some other embodiments, the analysis method of bridge pier collapse and bridge head washing events may be optimized based on the actual situation of the information set and the degree of influence of different risk scoring results. Different bridges face different risks and challenges. Optimizing the analysis method may more accurately identify potential risks and take corresponding measures, thereby helping to ensure the safety and reliability of the bridge.

[0216] S4. Comprehensively analyze the risk scoring results and risk levels of bridge flooding, bridge superstructure displacement, bridge superstructure overturning, bridge pier collapse and bridge head scouring events to achieve hidden danger inspection and water damage risk assessment for small and medium span bridges before the flood season. The specific steps and related contents are as follows: In the embodiment, firstly, corresponding risk assessment models are applied to calculate the bridge flooding, bridge superstructure displacement, bridge superstructure overturning, bridge pier collapse and bridge head scouring events respectively.

[0217] Secondly, determine the risk score. The risk scores of different events are determined based on the model calculation results. The above scores reflect the possibility of the event and the severity of the potential consequences.

[0218] Next, risk level classification and classification criteria are formulated. Reasonable risk level classification criteria are formulated according to the distribution of risk scores. In the embodiment, the above criteria fully consider the severity and frequency of events.

[0219] Finally, the risk level needs to be divided. According to the classification criteria, the risk score of each event is converted into a corresponding risk level, including low risk, medium risk, high risk or extreme risk.

[0220] After that, it is necessary to comprehensively collect different risk scoring results and risk level analysis information for comprehensive analysis and evaluation. This application adopts a multi-factor comprehensive analysis mechanism, which comprehensively considers the risk scores and risk levels of bridge flooding, bridge superstructure displacement, bridge superstructure overturning, bridge pier collapse and bridge head scouring events, as well as their mutual influence and correlation. At the same time, based on the results of the comprehensive analysis, the overall risk of the bridge is evaluated, which also includes the weight allocation of different risk events, priority sorting, and identification and evaluation of potential risks.

[0221] Finally, formulate a response strategy. Based on the overall risk assessment results, identify the potential hazards of the bridge before the flood season, such as structural defects, poor drainage, insufficient protective facilities, etc.; formulate specific response measures for the identified hazards, such as strengthening the structure, improving the drainage system, adding protective facilities, etc.; implementation and monitoring require implementation in accordance with the formulated measures, and continuous monitoring of the bridge status to ensure the effectiveness of the measures.

[0222] In addition, continuous improvement and feedback are required. The actual effect evaluation should be carried out. After the flood season, the effect of the implemented measures should be evaluated, including but not limited to the elimination of hidden dangers and the improvement of bridge safety performance. Experience summary is also required to summarize the lessons learned from this risk assessment and hidden danger investigation to provide reference for future bridge safety management. In terms of continuous optimization, the risk assessment model and response strategy can be continuously optimized based on the evaluation results and experience summary, so as to improve the scientificity and effectiveness of the hidden danger investigation and water damage risk assessment methods for small and medium-span bridges before the flood season.

[0223] Through the above steps, we can have a more comprehensive understanding of the risk scoring results and comprehensive analysis and evaluation process of risk levels for bridge flooding, bridge superstructure displacement, bridge superstructure overturning, bridge pier collapse and bridge head scouring events, thereby providing more scientific and comprehensive support for pre-flood hazard inspections and water damage risk assessments for small and medium-span bridges.

[0224] See also Fig.10 In an optional embodiment, the present invention further provides a system for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges. The system includes a processor, an input device, an output device and a memory. The processor, the input device, the output device and the memory are interconnected, wherein the memory is used to store a computer program, and the computer program includes program instructions. The processor is configured to call the above program instructions to execute the specific steps of the pre-flood hidden danger inspection and water damage risk assessment method for small and medium-span bridges and related embodiments provided by the present invention. The pre-flood hidden danger inspection and water damage risk assessment system for small and medium-span bridges of the present invention has a complete structure and is objective and stable.

[0225] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for pre-flood hidden danger inspection and water damage risk assessment for small and medium-span bridges, characterized by: The steps include: Acquire bridge flooding event information, determine the flood flow at the bridge deck elevation based on the bridge flooding event information, and obtain a risk scoring result and risk level of bridge flooding according to the flood flow and the bridge flooding event information; Collecting bridge structure instability information, establishing a bridge structure parameter analysis model based on the bridge structure instability information and obtaining parameter analysis results, and obtaining risk scoring results and risk level conditions of bridge superstructure displacement and bridge superstructure overturning according to the parameter analysis results; Acquire a bridge pier collapse information set, and obtain risk scoring results and risk level conditions of bridge pier collapse and bridge head scouring events based on the bridge pier collapse information set; A comprehensive analysis is conducted on the risk scoring results and risk levels of bridge flooding, bridge superstructure displacement, bridge superstructure overturning, bridge pier collapse and bridge head scouring incidents, in order to achieve hidden danger inspection and water damage risk assessment for small and medium spans before the flood season.

2. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 1 is characterized in that: The obtaining of bridge flooding event information and determining the flood flow at the bridge deck elevation based on the bridge flooding event information comprises: Obtaining bridge flooding event information, wherein the bridge flooding event information includes information on changes in river channel boundaries at the bridge location, river section compression information, and curve superelevation inspection information; Based on the river channel boundary change information of the bridge section, the bridge opening flow section compression information and the curve superelevation inspection information, the flood flow at the bridge deck elevation is obtained; The flood flow satisfies the following relationship: ， in, represents the typical flood flow, represents the Manning roughness coefficient, represents the average width of the river channel, It represents the average water depth of the section. Indicates the riverbed gradient of a river section.

3. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 2 is characterized in that: The risk scoring result and risk level of bridge flooding obtained according to the flood flow and the bridge flooding event information include: Setting a risk assessment scale for bridge flooding based on the bridge flooding event information, and obtaining a risk score result for bridge flooding by combining the risk assessment scale and the flood flow; Determine the risk level of bridge flooding according to the risk scoring result of bridge flooding; The risk scoring result of the bridge flooding satisfies the following relationship: ， in, represents the risk score result of bridge flooding, represents the typical flood frequency, Represents the risk assessment scale for bridge flooding.

4. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 1 is characterized in that: The collecting of the bridge structure instability information, establishing a bridge structure parameter analysis model based on the bridge structure instability information and obtaining the parameter analysis results comprises: Constructing a bridge structure parameter analysis model based on the bridge structure instability information, the bridge structure parameter analysis model including a water flow average velocity calculation function, a water flow pressure calculation function, a buoyancy calculation function, a lifting force calculation function and a floating object impact force calculation function; The water flow average velocity calculation function satisfies the following relationship: ， in, It represents the average flow velocity of water on the water-facing surface of the beam. represents the transverse part coefficient of the flow velocity, represents the first vertical distribution coefficient, Indicates the water depth of the channel section. represents the beam section height, represents the second vertical distribution coefficient, represents the third vertical distribution coefficient, It represents the average flow velocity of any measuring line in the cross section. It represents the average flow velocity of the vertical line in the cross section; The flow water pressure calculation function satisfies the following relationship: ， in, Surface water pressure, represents the water resistance coefficient of the bridge, It represents the projected area of ​​the bridge perpendicular to the water flow direction. represents the water flow density, It indicates the average flow velocity of water on the water-facing surface of the beam; The buoyancy calculation function satisfies the following relationship: ， in, represents buoyancy, represents the water flow density, represents the acceleration due to gravity, Indicates the volume of water displaced by the bridge; The lifting force calculation function satisfies the following relationship: ， in, Indicates the lifting force, Indicates the width of the bridge bottom. represents the length of the beam perpendicular to the direction of flood action, represents the water flow density, represents the acceleration due to gravity, Indicates the height of water in front of the bridge; The floating object impact force calculation function satisfies the following relationship: ， in, Indicates the impact force of floating objects, represents the gravity of floating objects, Indicates the water flow velocity, represents the acceleration due to gravity, Indicates the impact time.

5. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 4 is characterized in that: The risk scoring results and risk level of bridge superstructure deviation and bridge superstructure overturning obtained according to the parameter analysis results include: Analyze the horizontal force and friction acting on the support based on the parameter analysis results; The horizontal force satisfies the following relationship: ， in, represents the horizontal force that will act on the support, Indicates the water pressure. Indicates the impact force of floating objects; The frictional resistance satisfies the following relationship: ， in, is the friction force acting on the support, represents the friction coefficient, represents the number of forces perpendicular to the support, It represents the vertical reaction of the support under the total load effect.

6. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 5 is characterized in that: The risk scoring results and risk level of bridge superstructure deviation and bridge superstructure overturning obtained according to the parameter analysis results include: Obtain risk scoring results of bridge superstructure displacement and bridge superstructure overturning according to the horizontal force, the friction resistance and the parameter analysis results; Determine the risk level of the bridge superstructure displacement and the bridge superstructure overturning according to the risk scoring results of the bridge superstructure displacement and the bridge superstructure overturning; The risk scoring result of the bridge superstructure deviation satisfies the following relationship: ， in, represents the risk score result of the bridge superstructure deflection, represents the typical flood frequency, A risk assessment scale that represents the deflection of the bridge superstructure; The risk scoring result of the overturning of the bridge superstructure satisfies the following relationship: ， in, represents the risk score result of bridge superstructure overturning, represents the typical flood frequency, Represents the risk assessment scale of overturning of bridge superstructure.

7. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges as claimed in claim 1 is characterized in that: The acquisition of the bridge pier collapse information set and the acquisition of the risk scoring results and risk level of the bridge pier collapse and bridge head scouring events based on the bridge pier collapse information set include: Collect information on hidden dangers of scouring at the base of bridge piers, hidden dangers of scouring at the abutment foundation, and hidden dangers of scouring at the bridge head to obtain a collection of information on bridge pier and abutment collapse; Analyzing the total scouring depth, the lowest scouring line elevation and the safe burial elevation of the bridge pier based on the bridge pier collapse information set; The total scouring depth satisfies the following relationship: ， in, represents the total scour depth of the bridge pier, Indicates the natural scouring depth of the river section at the bridge location. Indicates the general scouring depth of the river section at the bridge location. Indicates the local scour depth of the river section at the bridge location; The elevation of the lowest scour line satisfies the following relationship: ， in, Indicates the lowest scour line elevation, represents the design water level elevation, Indicates the local scour depth of the river section at the bridge location; The safe embedding elevation satisfies the following relationship: ， in, Indicates the minimum safe embedding elevation of bridge piers and abutment foundations. Indicates the base design elevation, Indicates the minimum burial depth.

8. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 7 is characterized in that: The acquisition of the bridge pier collapse information set and the acquisition of the risk scoring results and risk level of the bridge pier collapse and bridge head scouring events based on the bridge pier collapse information set include: Based on the total scouring depth, the lowest scouring line elevation and the safe embedding elevation, a risk scoring result of bridge pier collapse and bridge head scouring events is obtained; According to the risk scoring results of bridge pier collapse and bridge head scouring events, the risk level of bridge pier collapse and bridge head scouring events was analyzed; The risk scoring result of the bridge pier collapse satisfies the following relationship: ， in, represents the risk score result of bridge pier collapse, represents the typical flood frequency, Represents the risk assessment scale of bridge pier collapse.

9. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 8 is characterized in that: The risk scoring result of the bridgehead washing event satisfies the following relationship: ， in, It represents the risk score result of the bridgehead washing event. represents the typical flood frequency, Represents the risk assessment scale of bridgehead scouring events.

10. Pre-flood hidden danger inspection and water damage risk assessment system for small and medium span bridges, characterized by: The system includes a processor, an input device, an output device and a memory, wherein the processor, the input device, the output device and the memory are interconnected, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is configured to call the program instructions to execute the method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges as described in any one of claims 1-9.

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