A practical method for cable force classification and layout of cable-supported bridges based on dual objectives

Abstract

The invention discloses a practical method for classified layout of cable forces of a cable-supported bridge based on dual objectives, comprising the following steps: a. dual objective selection of cable safety reserve redundancy and structural robustness; b. practical classification into three categories of flexible long cables, rigid short cables and cables of medium length; c. dual objective layout implementation method of cable forces of the three categories of cables, wherein the rigid short cables mainly consider the safety reserve redundancy analysis method to judge whether the safety of the cables themselves meets the requirements of the specifications; the flexible long cables mainly consider the structural robustness analysis method to compare the vulnerable and weak characteristics of different cables; the cables of medium length respectively consider the safety reserve redundancy and structural robustness analysis methods, and comprehensively select the most unfavorable design; the invention can more specifically take into account cables of different lengths and different positions of cable-supported bridges, implement more targeted cable force layout for cables of the same length and different positions, maximize the safety of the cables themselves, reduce the loss of vulnerable and weak cables and their accessory devices, and make the cable force layout more scientific.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent construction and operation and maintenance of cable-supported bridges, and in particular to a practical method for classifying and arranging cable forces of cable-supported bridges based on dual objectives. Background Art

[0002] At present, safety accidents of large-span cable-supported bridges occasionally occur, and more systematic and scientific construction and operation and maintenance decisions are urgently needed. There are many cables, high construction costs, large losses of auxiliary devices, heavy maintenance tasks, and lagging passive detection and evaluation. The problem is difficult to be fundamentally solved. The main reasons for this phenomenon are the following two aspects:

[0003] 1. The structural system of cable-supported bridges is complex. The cables connecting different parts of the main beam are of different lengths and forces. When they share the load, the physical and vibration responses of different cables are difficult to be at the same level. Existing designs take economic factors into consideration. The rigid short cables have limited safety reserve redundancy and significant problems of bending, shearing, corrosion and fracture. The vibration response of the flexible long cables varies in a complex manner, and the vibration fatigue of the cables and the loss of the attached damping devices are prominent.

[0004] 2. Cable-supported bridges are often located in harsh environments, and are exposed to temperature, rain and other factors for a long time. Although anti-corrosion and vibration reduction technologies are improving, construction defects of varying degrees, such as scratches on cable sheaths, will significantly increase the accumulation of vibration fatigue damage and bending, shear and rust damage on cables of different lengths. If maintenance is not timely, cable breakage accidents are likely to occur.

[0005] Therefore, the present invention considers the typical diseases of long and short cables supporting bridges, and proposes a practical method for cable force classification and layout based on dual objectives for cables of different lengths and different positions. It is very necessary to implement more targeted cable force classification and layout. Summary of the invention

[0006] The purpose of the present invention is to further implement the scientific construction and maintenance decision-making of cable forces of cable-supported bridges, solve the problems of vibration fatigue damage of flexible long cables, bending, shear, corrosion and fracture of rigid short cables, and prominent limitations of passive detection and evaluation. A practical method for classification and layout of cable forces of cable-supported bridges based on dual objectives is proposed. For flexible long cables, structural robustness analysis is implemented considering parameters such as strength and stiffness. For rigid short cables, safety reserve redundancy analysis is implemented considering parameters such as strength and stiffness. For cables of moderate length, both safety reserve redundancy analysis and structural robustness analysis are comprehensively considered, thereby implementing more scientific construction and maintenance decisions.

[0007] The technical solutions adopted to achieve the above objectives are:

[0008] A practical method for cable force classification and layout of cable-supported bridges based on dual objectives includes the following steps:

[0009] a. Dual-objective selection of safety reserve redundancy and structural robustness for cable layout

[0010] a1. Analyze the safety reserve redundancy of the cable based on different response parameters of the cable, and consider whether the response values ​​of the deflection / sag, stress, acceleration, and amplitude of the cable under the most unfavorable load combination are within the specification limit range and meet the design requirements, so as to ensure the safety of the cable itself; consider λ design Characterize different response parameter design values, λ max Characterizes the maximum value of the response parameter under the most unfavorable load combination, α represents the safety reserve redundancy, α=λ design / λ max ; If the safety reserve redundancy α>1, the design requirements are met and the cable itself is safe; if the safety reserve redundancy α<1, the design requirements are not met and the cable itself is unsafe; if the safety reserve redundancy α=1, the cable is in a critical state;

[0011] a2. Consider the structural robustness of different cable response parameters, and compare the changing characteristics of cable deflection, stress, acceleration, amplitude and other different response parameters under different earthquake, wind and vehicle moving loads. Although the response value is within the specification limit, it will still affect the driving comfort. In addition, if the cable response parameters change greatly, fatigue and cable end damper and other auxiliary device component losses will be high;

[0012] Considering R to represent the structural robustness, for different response parameters, considering the structural robustness of different responses, the structural robustness R calculation expression is R = (λ design —λ max ) / λ design , calculate the difference between the design value and the response value of the structure, and take the ratio of the difference to the design value of the structural response as the structural robustness evaluation index; when R is closer to 1, the structural robustness is good, and the structure or rod is not easy to be damaged. Conversely, the structure or rod is weak and vulnerable.

[0013] For multiple different cable structural robustness, the structural robustness of all cables must meet the requirements. It is necessary to comprehensively consider the structural robustness of each response parameter and compare the vulnerable and weak characteristics of different cables. Cables with smaller structural robustness are relatively vulnerable and weak. Under the long-term action of dynamic loads, they are prone to vibration fatigue and loss of cable end attachments, which require timely monitoring and maintenance. In this embodiment, the comparison of the robustness of different cable structures, let j = 1, 2, ... n represent different cable numbers, take the stress response parameter as an example, Right now Another example Right now At this time, the structural robustness based on stress index and All meet the requirements, but further comparison shows that That is, the cable j+1 structure has low robustness and is relatively fragile and weak. Under the long-term action of dynamic loads, repeated changes can easily cause vibration fatigue and loss of cable end attachments. It is necessary to comprehensively consider the structural robustness of each response parameter and compare the fragile and weak characteristics of different cables to minimize cable vibration fatigue and cable end attachment loss.

[0014] b. Division of different cables

[0015] In this patent, the cables of cable-supported bridges vary in length and force. The cables connecting the cross-section of the main beam mid-span area are usually longer (even up to hundreds of meters in length) and have greater force, while the cables connecting the cross-section of the main beam tower area are usually shorter and have less force. When long cables vibrate, the influence of bending stiffness can be ignored and they are considered flexible cables. Such cables have significant vibration response under external loads, and the cable vibration fatigue and accessory device loss are high. When short cables vibrate, the influence of bending stiffness is more prominent, and they are considered rigid cables. The probability of cable bending, shearing, rusting and wire breakage is high.

[0016] Through calculation and analysis of different factors such as cable length, bending stiffness, inclination, and mass per linear meter, the actual engineering division method is adopted. Cables with a length greater than or equal to 120m are considered flexible long cables, cables with a length less than or equal to 30m are considered rigid short cables, and cables with a length greater than 30m and less than 120m are considered cables of moderate length. Different cables require more targeted cable force layout methods to ensure the safety of the cables themselves while reducing losses.

[0017] c. Implementation method of layout of three types of cable forces considering dual objective factors

[0018] c1. For rigid short cables with a length of less than or equal to 30m, during the design calculation, reinforcement and verification stages, the physical and vibration response parameters of the cables are considered, and safety reserve redundancy analysis is carried out to determine whether the physical and vibration response values ​​are within the allowable range of the specification and whether they meet the design requirements; when the safety reserve redundancy α>1, the cable itself is safe, otherwise, the cable is unsafe;

[0019] c2. For flexible long cables with a length of 120m or more, during the design calculation, reinforcement, verification stage, long-term operation monitoring, and maintenance, the cable physics and vibration response parameters are mainly considered, and structural robustness analysis is carried out to compare the robustness R of different cable structures. Flexible long cables with low structural robustness have significant changes in cable response, are prone to vibration fatigue, and have large losses in auxiliary devices such as cable end dampers.

[0020] c3. For cables with a length greater than 30m and less than 120m, during the maintenance and operation phase of monitoring, testing and evaluation, it is necessary to consider the cable physics and vibration response parameters, implement safety reserve redundancy analysis and structural robustness analysis, and take the most unfavorable design of the two. This kind of thinking is helpful to take into account the rigidity and flexibility characteristics of long and short cables and develop a new cable-supported bridge structure system.

[0021] The dual-objective layout implementation method of cable forces considering different lengths can not only ensure the safety reserve redundancy of the cable itself, so that the maximum response value under the most unfavorable load combination is less than the corresponding response design value, but also ensure the robustness of the structure, compare the vulnerable and weak change characteristics of different cables, and minimize the vibration fatigue of vulnerable and weak cables and the loss of cable end accessories.

[0022] The beneficial effects of the present invention are:

[0023] The present invention is a practical method for classified layout of cable forces of cable-supported bridges based on dual objectives. The dual objectives of cable safety reserve redundancy and structural robustness are selected, and the cable design calculation and cable force changes during long-term operation are taken into account, and the vulnerable and weak characteristics of the cables are fully grasped for classification and decision-making; the cable length, bending stiffness, inclination, mass per linear meter and other factors are considered for calculation and analysis, and the cables are further divided into three categories: flexible long cables, rigid short cables and cables of moderate length; for cables of different lengths, a dual-objective layout implementation method of cable forces is proposed. The flexible long cables mainly consider the cable physics and vibration response parameters, and the structural robustness analysis is implemented to compare the cable lengths of different cables. Vulnerable and weak characteristics; For rigid short cables, main considerations are the physical and vibration response parameters of the cables, and the physical and vibration response values ​​are analyzed within the allowable range to determine the safety reserve redundancy of the cables themselves; For cables of moderate length, it is necessary to consider the physical and vibration response parameters of the cables respectively, implement safety reserve redundancy analysis and structural robustness analysis, and take the most unfavorable design of the two; The present invention can more specifically take into account cables of different lengths and positions in cable-supported bridges, and implement more targeted cable force layout for cables of the same length and different positions, thereby maximizing the safety of the cables themselves, reducing the loss of vulnerable and weak cables and their ancillary devices, and making the cable force layout more scientific. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The method flow diagram of the present invention is shown in FIG.

[0025] Figure 2 This is a diagram of the cable arrangement of a common harp-type (parallel) cable-stayed bridge;

[0026] Figure 3 for Figure 2 Schematic diagram of the dual-objective cable force layout method for response analysis and robustness analysis of long and short cables of medium cable-stayed bridges. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings.

[0028] A practical method for cable force classification and layout of cable-supported bridges based on dual objectives includes the following steps:

[0029] a. Dual-objective selection of safety reserve redundancy and structural robustness for cable layout

[0030] a1. Analyze the safety reserve redundancy of the cable based on different response parameters of the cable, and consider whether the response values ​​of the deflection / sag, stress, acceleration, and amplitude of the cable under the most unfavorable load combination are within the specification limit range and meet the design requirements, so as to ensure the safety of the cable itself; consider λ design Characterize different response parameter design values, λ max Characterizes the maximum value of the response parameter under the most unfavorable load combination, α represents the safety reserve redundancy, α=λ design / λ max ; If the safety reserve redundancy α>1, the design requirements are met and the cable itself is safe; if the safety reserve redundancy α<1, the design requirements are not met and the cable itself is unsafe; if the safety reserve redundancy α=1, the cable is in a critical state;

[0031] a2. Consider the structural robustness of different cable response parameters, and compare the changing characteristics of cable deflection, stress, acceleration, amplitude and other different response parameters under different earthquake, wind and vehicle moving loads. Although the response value is within the specification limit, it will still affect the driving comfort. In addition, if the cable response parameters change greatly, fatigue and cable end damper and other auxiliary device component losses will be high;

[0032] Considering R to represent the structural robustness, for different response parameters, considering the structural robustness of different responses, the structural robustness R calculation expression is R = (λ design —λ max ) / λ design , calculate the difference between the design value and the response value of the structure, and take the ratio of the difference to the design value of the structural response as the structural robustness evaluation index; when R is closer to 1, the structural robustness is good, and the structure or rod is not easy to be damaged. Conversely, the structure or rod is weak and vulnerable.

[0033] For multiple different cable structural robustness, the structural robustness of all cables must meet the requirements. It is necessary to comprehensively consider the structural robustness of each response parameter and compare the vulnerable and weak characteristics of different cables. Cables with smaller structural robustness are relatively vulnerable and weak. Under the long-term action of dynamic loads, they are prone to vibration fatigue and loss of cable end attachments. Comparison of the structural robustness of different cables, let j = 1, 2, ... n represent different cable numbers, take stress response parameters as an example, although the structural robustness and Satisfy the requirements, further comparison is needed. That is, the cable j+1 structure has low robustness and is relatively fragile and weak. Under the long-term action of dynamic loads, repeated changes can easily cause vibration fatigue and loss of cable end attachments. It is necessary to comprehensively consider the structural robustness of each response parameter and compare the fragile and weak characteristics of different cables to minimize cable vibration fatigue and cable end attachment loss.

[0034] b. Division of different cables

[0035] In this patent, the cables of cable-supported bridges vary in length and force. The cables connecting the cross-section of the main beam mid-span area are usually longer (even up to hundreds of meters in length) and have greater force, while the cables connecting the cross-section of the main beam tower area are usually shorter and have less force. When long cables vibrate, the influence of bending stiffness can be ignored and they are considered flexible cables. Such cables have significant vibration response under external loads, and the cable vibration fatigue and accessory device loss are high. When short cables vibrate, the influence of bending stiffness is more prominent, and they are considered rigid cables. The probability of cable bending, shearing, rusting and wire breakage is high.

[0036] Through calculation and analysis of different factors such as cable length, bending stiffness, inclination, and mass per linear meter, the actual engineering division method is adopted. Cables with a length greater than or equal to 120m are considered flexible long cables, cables with a length less than or equal to 30m are considered rigid short cables, and cables with a length greater than 30m and less than 120m are considered cables of moderate length. Different cables require more targeted cable force layout methods to ensure the safety of the cables themselves while reducing losses.

[0037] c. Implementation method of layout of three types of cable forces considering dual objective factors

[0038] c1. For rigid short cables with a length of less than or equal to 30m, during the design calculation, reinforcement and verification stages, the physical and vibration response parameters of the cables are considered, and safety reserve redundancy analysis is carried out to determine whether the physical and vibration response values ​​are within the allowable range of the specification and whether they meet the design requirements; when the safety reserve redundancy α>1, the cable itself is safe, otherwise, the cable is unsafe;

[0039] c2. For flexible long cables with a length of 120m or more, during the design calculation, reinforcement, verification stage, long-term operation monitoring, and maintenance, the cable physics and vibration response parameters are mainly considered, and structural robustness analysis is carried out to compare the robustness R of different cable structures. Flexible long cables with low structural robustness have significant changes in cable response, are prone to vibration fatigue, and have large losses in auxiliary devices such as cable end dampers.

[0040] c3. For cables with a length greater than 30m and less than 120m, during the maintenance and operation phase of monitoring, testing and evaluation, it is necessary to consider the cable physics and vibration response parameters, implement safety reserve redundancy analysis and structural robustness analysis, and take the most unfavorable design of the two. This kind of thinking is helpful to take into account the rigidity and flexibility characteristics of long and short cables and develop a new cable-supported bridge structure system.

[0041] like Figure 1As shown, it is a flow chart of a cable force classification layout method for cable-supported bridges based on dual objectives, including dual objective selection analysis of cable force safety reserve redundancy and structural robustness; three practical classifications of long cables, short cables and cables of moderate length; dual objective layout implementation methods for three types of cable forces, wherein flexible long cables mainly consider cable physics and vibration response parameters, and implement structural robustness analysis, that is, the range of physical and vibration response changes is within the allowable range; rigid short cables mainly consider cable physics and vibration response parameters, and implement safety reserve redundancy analysis, that is, the physical and vibration response values ​​are within the allowable range; for cables of moderate length, it is necessary to consider cable physics and vibration response parameters respectively, implement structural robustness analysis and safety reserve redundancy analysis, and take the most unfavorable design of the two; the present invention can more specifically take into account cables of different lengths and different positions of cable-supported bridges, implement more targeted cable force layout for cables of the same length and different positions, and make the cable force layout more scientific.

[0042] Figure 2 This is a schematic diagram of a common harp-type (parallel) cable-stayed bridge and cables. The main beam is l long, and 8 types of cables of different lengths are symmetrically arranged at equal intervals, with a total of 32 cables. Cables WB1 to WB8 are arranged on the west side span (WB), cables WZ1 to WZ8 are arranged on the west side of the middle span (WZ), cables EZ1 to EZ8 are arranged on the east side of the middle span (EZ), and cables EB1 to EB8 are arranged on the east side span (EB). The length of cable 1# is about 13.8m, the length of cable 2# is 28.9m, the length of cable 3# is 44.1m, the length of cable 4# is 59.3m, the length of cable 5# is 74.4m, the length of cable 6# is 89.6m, the length of cable 7# is 104.8m, and the length of cable 8# is 119.9m. Parameters such as the bulk density of each cable are selected according to conventional methods. The cables are further classified into 1# and 2# rigid short cables, 3#-6# cables are medium length cables, and 7# and 8# cables are flexible long cables. According to engineering experience, the damage is more concentrated, among which the flexible long cables are prone to fatigue damage due to repeated vibration. As the service cycle increases, the damage accumulates, and the damper and other auxiliary devices are greatly damaged. Rigid short cables are prone to rust and breakage due to rain, temperature and environment.

[0043] Figure 3 yes Figure 2 The dual-objective layout method of cables of different lengths and different positions in a common harp-type (parallel) cable-stayed bridge. The maximum physical and vibration response of the cable is λ max The corresponding response parameter values ​​of each cable under the most unfavorable design load are i is the number of 8 types of cables with different lengths, i=1,2,3,4,5,6,7,8.

[0044] Referring to the traditional structural response analysis method, That is, under the most unfavorable load combination, the response parameters of each cable are within the design allowable range, and the structure is safe. For example, the cable is made of steel strands, considering the cable stress σ, let the cable stress limit σ designThe value is 1860MPa, which is required That is, the safety degree is greater than 1, so that the requirements are met and further mathematical transformation is performed. Right now It can be seen that the structural robustness That is, structural safety. It can be widely used in the design, reinforcement and verification stages under the most unfavorable load combination to meet requirements and ensure safety.

[0045] However, unlike theoretical design calculations, in engineering practice, during the long-term operation of the flexible structural system, the structural response of the flexible 1# long cable increases significantly and changes repeatedly under the external loads, especially moving loads, earthquakes, and wind loads. Significantly increased, close to σ design When the structural safety factor is close to 1, the structure is in a critical state. As the response increases further, the damper and other auxiliary devices will be damaged. On the other hand, repeated changes will also cause fatigue damage to the steel strands, and even breakage of wires and cables.

[0046] The structural robustness R of different flexible cables under external loads, especially moving loads, earthquakes, and wind loads i The difference is significant, and the comparison shows the vulnerable and weak characteristics of different cables. The vulnerable and weak cables have prominent vibration fatigue characteristics and large losses in the auxiliary devices, which require special attention in maintenance and operation work such as monitoring, testing and evaluation.

[0047] This embodiment does not impose any formal limitation on the shape, material, structure, etc. of the present invention. Any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0048] 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 make equivalent replacements for some of the technical features therein, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A practical method for cable force classification and layout of cable-supported bridges based on dual objectives, characterized in that: The steps include: a. Dual-objective selection of safety reserve redundancy and structural robustness for cable layout a1. Analyze the safety reserve redundancy of the cable based on different response parameters of the cable, and consider whether the response values ​​of the deflection / sag, stress, acceleration, and amplitude of the cable under the most unfavorable load combination are within the specification limit range and meet the design requirements, so as to ensure the safety of the cable itself; consider λ design Characterize different response parameter design values, λ max Characterizes the maximum value of the response parameter under the most unfavorable load combination, α represents the safety reserve redundancy, α=λ design / λ max ; If the safety reserve redundancy α>1, the design requirements are met and the cable itself is safe; if the safety reserve redundancy α<1, the design requirements are not met and the cable itself is unsafe; if the safety reserve redundancy α=1, the cable is in a critical state; a2. Consider the structural robustness of different response parameters of the cable, compare the change characteristics of the cable's deflection, stress, acceleration, amplitude and other different response parameters under different earthquake, wind and vehicle moving loads, and use the structural robustness R calculation expression as R = (λ design —λ max ) / λ design , R∈[0,1], calculate the difference between the design value and the response value of the structure, and use the ratio of the difference to the design value of the structural response as the structural robustness evaluation index; when R is closer to 1, the structural robustness is good, and the structure or rod is not easy to be damaged. Conversely, the structure or rod is weak and vulnerable. b. Division of different cables Through calculation and analysis of different factors such as cable length, bending stiffness, inclination angle, and mass per linear meter, the actual engineering classification method is adopted, and cables with a length greater than or equal to 120m are considered to be flexible long cables, cables with a length less than or equal to 30m are considered to be rigid short cables, and cables with a length greater than 30m and less than 120m are considered to be cables of moderate length. c. Implementation method of layout of three types of cable forces considering dual objective factors c1. For rigid short cables with a length of less than or equal to 30m, during the design calculation, reinforcement and verification stages, the physical and vibration response parameters of the cables are considered, and safety reserve redundancy analysis is carried out to determine whether the physical and vibration response values ​​are within the allowable range of the specification and whether they meet the design requirements; when the safety reserve redundancy α>1, the cable itself is safe, otherwise, the cable is unsafe; c2. For flexible long cables with a length of 120m or more, during the design calculation, reinforcement, verification stage, long-term operation monitoring, and maintenance, the cable physics and vibration response parameters are mainly considered, and structural robustness analysis is carried out to compare the robustness R of different cable structures; flexible long cables with low structural robustness have significant changes in cable response, are prone to vibration fatigue, and have large cable end damper losses; c3. For cables with a length greater than 30m and less than 120m, during the maintenance and operation phase of monitoring, testing and evaluation, it is necessary to consider the cable physical and vibration response parameters, implement safety reserve redundancy analysis and structural robustness analysis, and take the most unfavorable design of the two.

2. A practical method for cable force classification and layout of cable-supported bridges based on dual objectives according to claim 1, characterized in that: In step a2, for the structural robustness of multiple different cables, the structural robustness of all cables must meet the requirements. The structural robustness of each response parameter needs to be comprehensively considered, and the fragile and weak characteristics of different cables are compared. The cables with smaller structural robustness are relatively fragile and weak. Under the long-term action of dynamic loads, they are prone to vibration fatigue and loss of cable end accessories, and need to be monitored and maintained in time.

Images