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    Home > Coatings News > Paints and Coatings Market > Japan: hierarchical management and maintenance of the bridge "pension" each has its own autumn

    Japan: hierarchical management and maintenance of the bridge "pension" each has its own autumn

    • Last Update: 2020-11-17
    • Source: Internet
    • Author: User
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    As of 2015, the total number of highway bridges in Japan was 723,000 (with a bridge length of more than 2m), of which about 37,000, or 5%, were managed by the Ministry of Land, Transport and Transport; It can be learned that the urban township management of the bridge accounted for the largest proportion.
    japan bridge maintenance management is divided into several levels, there are the Ministry of Land and Transport management of bridges, highway companies to manage the bridge, the capital of the county and city management of bridges, such as . Highway Company is divided into the Capital Expressway Company, the four countries of Aozhou Contact Expressway Company, NEXCO East Japan Expressway Company and so on. Different bridge management levels and units, bridge management and testing practices are different, the focus is not the same.
    Three Bridges managed by the Ministry of Land, Transport
    The Ministry of Land and Transport is one of the central provincial offices in Japan, and in 2001 the Central Provincial Department was re-edited by the Ministry of Transport, the Ministry of Construction, the Hokkaido Development Department and the Ministry of Land and other organs, and its business scope includes land planning, rivers, cities, housing, roads, harbors and other construction and maintenance management.
    management of the bridge is one of its business scopes. Bridge management focuses on ensuring the safety of road users, preventing the killing of both sides of the road and third parties, and grasping the bridge's condition in a timely manner. For the bridge management has developed a regular inspection and maintenance management process, mainly from the usual inspection, regular inspection, intermediate inspection, special inspection, abnormal inspection and other aspects made some provisions.
    Ministry of Land and Transport has established the Comprehensive Institute of Land and Technology Policy (hereinafter referred to as the National Research Institute), one of its main tasks is to undertake technical seminars by national and local public organizations. The necessary knowledge and skills training, the preparation of training courses, the establishment of technical talk rooms corresponding to damage structures, technology development and so on are carried out by inspectors in management departments throughout the country.
    the bridge managed by the Ministry of Land, Transport and Transport, according to the inspection data, the various components that make up the bridge and the objective facts of the damage and deformation are evaluated, and the inspection records are left for each component inspection site. The inspection records shall be analyzed by the State General Research Institute, the characteristics of bridge deterioratation shall be mastered, and maintenance management plans shall be prepared.
    technical talks, civil technology materials are jointly edited by the National Research Institute and the Civil Engineering Research Institute, and technical information is shared with technical personnel as an example reference for "on-site learning maintenance and maintenance". In these technical materials, not only the injury phenomenon and countermeasure examples are introduced, but also records the technical personnel of the National Research Institute and the Civil Engineering Research Institute, the concerns about the damage structure, the contents of the investigation, and the judgment based on the results of the investigation.
    technology development, in order to carry out efficient and accurate inspection, maintenance and management of more than 720,000 road bridges, it is necessary not only to improve the technical level of technical personnel, but also to adopt new technologies. To this end, the Ministry of Land and Transport set up a robot technology, monitoring technology committee, its technology used in the field.
    2014, 10 plans were listed in the National Strategic New Invention Program (SIP), one of which is "Infrastructure Maintenance Management, Renewal, Control Technology". The five research and development projects necessary in the infrastructure maintenance and management process are: detection, monitoring and diagnosis technology, robot technology, information and communication technology, structural materials, inferior structure, repair and reinforcement technology, and asset management technology.
    The bridge management
    basic idea
    of the four-country liaison bridge company in Benzhou, almost all of the bridges managed by the four-country liaison bridge company are large-span sea bridge projects, but also by a number of large-span pull bridge, suspension bridge, arch bridge composed of bridge groups. Sea bridge, corrosion environment is more severe, deteriorating development is rapid, and the existing bridge inspection and maintenance of the best means is limited. In order to ensure that these large bridges are in good and healthy condition, a lot of manpower and material resources need to be invested and a lot of effort is required. Coupled with the fact that these bridges are on important trunk roads with no alternative lines, traffic cannot be disrupted during the repair process. Due to the large scale of the project, the need for large maintenance funds, can not be simply replaced and large-scale maintenance. Therefore, the management objective set by the company is to ensure that it can be used normally for more than 200 years. To this end, the concept of "asset management" is introduced, with "preventive maintenance" as the basic, with the goal of minimizing life cycle costs.
    the implementation of preventive conservation technology, the key is to do a good job of inspection, according to the inspection of the state of the structure. Thus, the PDCA cycle is implemented to summarize the data obtained during the inspection. Through the analysis of the data, the appropriate evaluation and deteriorating prediction. Based on these data, the maintenance plan is determined, the life cycle cost of the structure is minimized and the management efficiency is improved.
    the contents and methods of large-span bridge inspection
    1. Inspection system
    in the formulation of inspection system, and strive to check the high degree of business, long-term maintenance of the integrity of large-span bridges, etc. , is very important. In order to make a sound diagnosis, inspectors must have the necessary knowledge and skills to assess the construction and component status of a large span bridge.
    2. Types and frequencies of large-span bridge checks
    types and frequencies of inspections are shown in Table 1. Roving inspection and basic examination, according to the different parts of the inspection object, the frequency of inspection is also different. Therefore, it is important to develop an interim and medium-term inspection plan.
    the site and frequency of the tour is shown in Table 2. For each bridge, the circuit inspection line is set according to the inspection frequency and the inspection is performed. Figure 1 shows the part of the suspension bridge during the tour.
    Figure 1 Where the suspension bridge tour needs to be focused on inspection
    Basic inspection to the naked eye to observe the inspected site mainly, at the same time with the hand touch, gently tap to hear the sound, non-damaged inspection, and so on. Use a high-pixel camera when it is difficult to observe with the naked eye. Depending on the site of the inspection, the frequency of the examination is shown in Table 3.
    inspection of the bridge, mainly based on the line measurement of the bridge as a whole and the shape measurement of the composition components. The determination of the overall shape of a bridge mainly refers to the change of its shape along the vertical section, the relative position of the foundation, the relative distance between the main components, etc.
    inspection of large-span bridges, which are currently projected as shown in Table 4, are carried out regularly after 1, 3, 5 and 10 years after opening. So far, fine inspection has found no abnormality in the bridge (large deformation, boom pull changes, etc.). Figure 2 shows the results of the line measurement 11 years after the opening of the Shengkou Bridge. It can be seen from the figure that 11 years after opening, the bridge line shape, due to the effect of contraction and slow change, is 100mm lower than the initial value, but the expected change value is almost the same as at the beginning of the design. Therefore, it can be considered that there is no effect on the integrity of the bridge as a whole.
    Figure 2 Raw mouth bridge wire measurement results
    Main cable inspection
    1. Principles of main cable maintenance management
    The main cable of the suspension bridge is one of the most important components of the suspension bridge, after the bridge is completed, it is extremely difficult to replace the main cable. Therefore, effective anti-corrosion measures should be taken to extend its service life. At present, anti-corrosion measures are mainly used to deliver dry air to the main cable (Figure 3). The main cable air drying system distributes the dry air produced along the length of the main cable to the wire. In order to ensure that dry air can have proper air delivery spacing, proper air intake and air pressure, the main cable surface and the rope clamp to prevent air leakage measures are very important. In order to ensure the function of the gas delivery system, it is necessary to check the working conditions of the gas delivery system on a regular basis, observe the temperature and humidity environment inside the main cable and the corrosion of the main cable, and determine the soundness of the main cable accordingly.
    diagram of the main cable air delivery system in Figure 3
    2. Main cable inspection and internal humidity management of the main cable
    basic inspection of the main cable, it should be noted that:
    Is to open the main cable outside the entanglement package, check the vibration caused by air leakage;
    second is to check whether the bolts at the air supply protection layer, exhaust protection layer and the air supply pipe connection connector are loose and whether there are cracks in the pipe joints.
    is to check the main cable gas delivery equipment changes.
    in order to confirm that the inside of the main cable is dry, a representative checkpoint needs to be monitored for a long time. Monitoring holes are set up for representative monitoring points and humidity monitoring is carried out once a year to confirm whether the standard value of humidity control inside the main cable is below the annual average of 40% RH. Based on the monitoring results, the conservation management methods for the following year are determined. The long-term monitoring results of humidity inside the main cable of the Aoshi Strait Bridge are shown in Figure 4.
    4 Internal humidity monitoring results of the main cable
    sling inspection
    1. Maintenance management principle
    slings are designed to be replaceable. However, a full replacement would require significant maintenance costs. Therefore, with the goal of long life, the non-damage inspection method and maintenance method are developed.
    slings are divided into two types, namely wire rope and parallel wire. Parallel wire slings perform well in corrosion protection. For parallel wire rope slings, the three parts of the rope saddle area, anchoring area and general area are respectively managed for maintenance.
    2. Inspection method
    sling inspection method is as follows - visual inspection, non-damage inspection, other additional investigation.
    for wire rope slings, non-damaged inspections can be carried out when the degree of internal corrosion is not judged by the appearance inspection alone. Now, non-break inspection mainly uses the full magnetic flux method. Other additional investigations include chemical analysis of attached corrosive substances, water quality analysis of stagnant water, etc.
    All Magnetic Flux Method - strong magnetization of the steel rope of a strong magnet, measurement of the magnetic beam flowing inside the rope, evaluation of the reduction of the area of the rope break due to corrosion through the ratio relationship between the magnetic beam and the broken area. The principle is as shown in Figure 5.
    Figure 5 Principles of Monitoring the Full Magnetic Flux Method
    Span bridge soundness evaluation
    sound evaluation, based on the principle of preventive conservation, through maintenance management and efficient maintenance, to seek long life. The classification of soundness evaluations is shown in table 5. In the table, the provisions on soundness evaluation in the "Road and Bridge Inspection Keys" of the Ministry of Land and Transport are listed.
    Hanging bridge soundness evaluation, its evaluation grade is divided into the main components (beams, towers, ropes and other 6 components), secondary components (shrink device and other 6 components), as shown in Table 5, respectively, 0 to 5, and the weight of 2 to 10 set for each component. The four-country contact bridge highway company of the state on the soundness of the suspension bridge evaluation, when the evaluation level of about 4, think that the carrying capacity, durability is good. In the health assessment of the Ministry of Land and Transport, I. or II. is normal. Although the use of suspension bridge years, the form of the energetic beam is different, but the general direction of sound change is basically similar. According to preventive maintenance, the improvement index is not greatly reduced, carrying capacity, durability, etc. are not a problem.
    the Capital Expressway Company's bridge
    1. The particularity of maintenance management
    The bridges managed by the company have special features such as high ratio of structures, large number of old structures, huge traffic volume, high mixing rate of large vehicles, and a large number of ancillary facilities.
    2. The purpose of
    to prevent the injury caused by the loss, the expansion of the injury, to ensure the safety of the structure. Fully understand the path of injury, determine the likelihood that the same injury will occur in other similar areas, or the progress of damage at the associated site. According to this purpose, through the inspectors to judge: the structure should have the ability, highway users' safety and comfortable and fast walking, the safety of the area and surrounding residents, the safety of the viapass off the street and facilities users.
    3. The key inspection parts of the steel structure
    Most of the bridges of the capital highway are steel bridges, the main areas prone to damage are: steel bridge panels, the main beam and beam intersection, the main beam and the end beam intersection, the support, the end of the beam and so on.
    4. The determination of the
    of structural damage is mainly based on the performance required by the structure, especially the safety of the structure. The safety of structure refers to the safety of the main structure, walking safety, public safety, etc., measured by the "low" or "unsafe state" of safety, as measured by table 6. According to this idea, the damage of civil structures is divided into four levels, namely:
    level A, in order to restore safety, emergency response measures must be
    taken

    ;
    5. The U ribs and welding parts of the U-panel of the steel bridge panel crack semi-automatic ultrasonic exploration device (SAUT)
    steel bridge panel, as shown in Figure 6, are prone to fatigue damage, fatigue cracks from the root of the U-rib weld and develop towards the thickness of the panel. Therefore, it is necessary to detect the direction of crack development through detection and take measures to control its development. Recently developed a semi-automatic ultrasonic detection device that can effectively detect its cracks, the cluster-type 70-degree angle probe, placed under the bridge panel U rib weld, can detect the depth of more than 6mm crack development.
    figure 6 Steel bridge panel U rib weld SAUT detection
    conclusion
    In the 1980s and 1990s, at the peak of Bridge Construction in Japan, a large number of bridges were built, and a number of bridge projects with influence in the international bridge industry were built. Now, the peak of bridge construction has passed, the 60's to 70's built bridges have gradually entered the "middle-old age." For example, the large-scale cross-sea bridge managed by the four-country liaison bridge company in the state has been in operation for nearly 30 years, and the bridge managed by the Capital Expressway Company has been in operation for more than 50 years, about 10.6%. Therefore, it is the main task to carry out scientific maintenance and management of bridges and improve the durability of bridges. As mentioned earlier, Japan in the maintenance and management of bridges, from the Ministry of Land and Transport, the prefectures and cities and the relevant highway companies, all levels attach great importance to, have developed a detailed maintenance management methods, the National Research Institute in bridge maintenance management has played a very important role. In the four-country liaison bridge company in the state, the concept of asset management, preventive conservation ideas, to minimize life cycle costs as the goal, etc. , are worthy of reference.
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