Although there are many quality control/quality assurance (QC/QA) projects in the United States, we are still very interested in exploring the most effective bridge inspection system in other countries.
The inspection team is jointly funded by ASSHTO, FHwA and NCHRP. The plan is organized by the American Trade Promotion Company.
Topics of interest to the inspection team include:
(1) organizational structure and background;
(2) test data;
(3) Personnel qualifications;
(4) process control;
(5) equipment;
(6) documents.
2. Host country
The group held a series of meetings and field trips from June 6 to June 7, 2007. The team visited Finland, Denmark, Germany and France and met people from Sweden and Norway in Denmark.
On behalf of. These six countries were selected because of their leading practices in bridge evaluation, bridge management and quality assurance.
3. Investigation contents
The team is composed of 10 members, and studies European bridge detection methods, with emphasis on quality assurance. In this group, 3 representatives are from Federal Highway Administration (FHwA), 4 representatives are from State Department of Transportation (d0t), 65,438+0 representatives are from National Association of County Engineers (NACE), 65,438+0 representatives are from academia, and 65,438+0 representatives are structural engineering design consultants and report assistants. The project is jointly funded by ASSHTO, FHWA and NCHRP. The plan is organized by the American Trade Promotion Company.
3. 1 Review and summary of preliminary investigation results
On the whole, the research group found that European organizers have invested heavily in bridge inspection, and their bridge inspection projects should not only ensure the safety of highway users, but also ensure the durability and applicability to meet the needs, and increase infrastructure investment according to the existing list of old bridges. It mainly emphasizes quality inspection by qualified inspectors with clear objectives, regular calibration of inspectors, data collection procedures, and the use of appropriate equipment to evaluate the structural state. Most of the institutions visited have major procedures aimed at unifying inspection items, formulating multi-level inspection plans and procedures, conducting damage assessment and planned maintenance, and carrying out maintenance through inspection.
The inspection team identified many practices and techniques of bridge inspection, which are related to the above-mentioned topics of interest. These thematic areas are as follows. The ranking in this report is only for clarity, and has nothing to do with importance.
3.2 Detailed inspection reference and tools
Bridge inspectors can get many very detailed manuals and reference materials as tools. These measures include inspection manuals, maintenance manuals, maintenance manuals and guidelines for coding and recording data. In the American and European countries visited, the main method is visual inspection. Europeans use intuitive tools to record and encode data, make damage assessment, and carry out maintenance and repair to the greatest extent. Many manuals can be used as reference for testing and maintenance. It is necessary to focus on the investigation and provide a more unified evaluation level. All types of damage and quantification of performance indicators are accompanied by photos. These manuals contain many photos and pictures showing the damage and corresponding grades. Several countries have implemented quantitative standard concrete crack detection reports. The photos obtained by European inspectors from past inspections can be used for current inspections. The vehicles of the German inspection team are equipped with field equipment, offices and bridge records to support the operations of inspection points.
3.3 Report and data management
All countries visited implement standardized inspection reports, forms, terms and grades. Notable practices include using customizable inspection forms, standardized terms and rating standards provided by the bridge management system to provide inspectors, embedding inspection reports into digital photos, and requiring designers to determine the structure of key areas for inspection. At the scene, the inspector insisted on evaluating any damage that needed to be repaired. In this way, we can determine the annual appropriation and maintenance plan, and track maintenance orders. In Germany, inspectors use computer programs to select a structural condition from the drop-down menu to generate ratings. In Denmark, independent asset management policies, systems and practices have been established to better invest in the decision-making of major structural components.
3.4 Training and Certification of Bridge Inspectors
European countries adopt various methods to train and certify inspectors. All countries have technical education requirements for inspectors, and most require organizers to have engineering degrees. Many people specially train the required testing personnel to ensure the quality of testing and data. It is considered important to train project managers and conduct competency tests.
Maintain a core working group with bridge inspection expertise, and European owners are in a leading position in these fields. The experienced working group provides a core of personnel: (1) as a teacher to verify new employees and suppliers; (2) Providing quality assurance, analysis and evaluation work and representative offices; (3) Have continuously supplemented and developed reference materials to support the organization's plan.
3.5 Inspection Type and Frequency
All the countries visited have very clear inspection types and several clear inspection scopes.
A typical finding is that European institutions have made a technical decision to determine the inspection frequency. Usually this program includes the ability to detect groups. The countries of the visited host countries believe that the qualifications and experience of inspectors provide confidence for decision-making. The inspection cycle usually lasts for 5 or 6 years, but it reaches 9 years in France. Denmark and France use risk acceptance criteria to help determine the type and frequency of testing.
In the plan, the host country will select time intervals on the basis of detailed inspection, conduct temporary maintenance inspection and check the qualifications of inspectors. However, the actual inspection frequency in the host country is shorter than the set frequency (longer than that in France), and the set frequency is related to many factors such as conditions, scale, structural type, use time, average daily traffic volume, complexity and so on, so as to better allocate resources such as manpower and capital.
3.6 Using reference bridge
Finland has a unique method to ensure quality. FINNRA adopted 106 bridges and 26 steel culvert bridges as control samples or a set of reference bridges. Experienced internal bridge inspectors collect raw data from these bridges to maintain consistency.
3.7 The collected data is used to meet various needs.
(1) Collect the data of bridge applicability and durability over a period of time.
(2) Collect similar bridge data for trend analysis and update the degradation model of bridge management system.
(3) By comparing the benchmark data, the quality of concrete bridge detection data can be controlled.
(4) Training and refresher training inspectors, evaluating the inspection level of inspectors, and comparing it with the average value of internal employees and all inspectors.
3.8 Non-destructive testing (NDT)
During the inspection, inspectors use nondestructive testing to help their condition coding. Detailed references of some institutions outline the correct use of nondestructive testing equipment and methods. It includes terms and definitions, defects and applications. In Germany, users use nondestructive testing products for independent evaluation. In addition, there are some very unique nondestructive testing technologies, such as Germany using specially configured ultrasonic shear wave sensors for clear defect observation.
When possible, some institutions also use the bridges to be demolished to evaluate the effect of nondestructive testing methods.
3.9 Causes of damage
Bridge inspection includes the inspector's investigation of the cause of damage, which is part of the inspector's inspection procedure. Inspectors are trained to evaluate the damage of structural units, evaluate the safety of users and the impact of damaged components on durability according to structural stability, and propose appropriate measures to solve the damage problem. With the knowledge of inspector structure and a definite sense of urgency, the organization can get direct short-term planning requirements. All agencies have procedures for taking action to find out whether there is a serious situation or based on a higher level of review and approval. In all cases, when problems are found in key structures, it is necessary to solve who is responsible for them to ensure public safety and avoid additional losses of facilities. Several other owners have carried out maintenance activities in this regard. Maintenance activities are usually tracked and recorded by all institutions on the bridge. This provides better management data related to the actual bridge and related structural costs.
More emphasis is placed on the causes of bridge defects. Compared with American practice, it is characterized by distinguishing between units and components, which is essentially the result of display defects. Europe has a more comprehensive disaster reduction strategy, that is, inspectors designate specific repair and reconstruction activities.
3. 10 Other
Another interesting project worth considering in the United States is the DVD used in Zhang Deguo. "Test according to DIN 1076". DVD is aimed at the public and outlines.
Reasons for inspection of bridges and structures. DVD not only provides an informative and comprehensive inspection process, but also seems to be a useful mechanism to obtain the support of bridge inspection and maintenance.
Secondly, the usual practice is that the organizers do not use special inspectors for the same bridge and rotate in the subsequent inspections. This method provides a new assessment of the bridge condition, thus providing more reliable or at least more confirmation of its real condition.
In the field investigation of bridge inspection, the details observed by the research team were incorporated into the bridge design process to facilitate bridge inspection. In GreatLinkBridge, Denmark, it is easy to get into the tower by elevator. Inspectors use monorails to transport inspection equipment in beams. Permanent inspection is a mobile device installed outside the structure. A shaft consisting of a measuring system is used to determine the position of the bearing. In addition, the design of the telescopic part is convenient for inspection. In Germany, concrete steps are built along the wing wall, so it is equally safe to walk along the slope. These details will help to carry out bridge maintenance activities.
Step 4 suggest
Based on the above findings, the group made the following preliminary general recommendations:
(1) Establish a reasonable benchmark for bridge detection frequency;
(2) determine the criteria and formulate national quality assurance/quality control procedures;
(3) Provide reference manuals for illustrations and photos;
(4) Develop comprehensive inspection and maintenance methods;
(5) exchange new discoveries and technologies in the investigation;
(6) Shear wave ultrasonic sensor.
In view of all these topics, concrete actions have been taken to determine the use of the survey results and serve the existing evaluation and inspection procedures of old bridges in the United States, with emphasis on improving quality control (QC) and quality assurance (QA).
5, the implementation of key projects
5. 1 Establish a reasonable reference frequency for bridge inspection.
The investigation team suggested establishing a nationally recognized benchmark to determine the frequency of bridge inspection, which is based on safety, condition, design, age structure and judgment of the project. Different levels of inspection work and specifications
The environment should be combined with clear standards to serve the education, training and qualification certification of inspectors. Combined with the needs of different levels, we can choose 6 years or other appropriate frequency for more comprehensive and in-depth inspection. And in a more limited range, in a shorter time interval, to provide more effective inspection, improve the overall quality, in order to use resources more effectively. State or federal agencies can choose to use it as an optional tool for new bridges, and it can also be used in a wider range. In the final implementation process, it may be necessary to revise the current National Bridge Inspection Standard (NBIS) regulations formulated by FHWA.
The investigation team also suggested that all problems should be reviewed and corrected, which was formulated by the power and field test bridge Committee according to NCHRP standards. The statement on this issue, entitled "Formulation of Bridge Inspection Policy Based on Reliability", provides the concept and process of benchmark research determined by the investigation team. This is the research project of # 1, which is selected by the Bridge and Structure Sub-committee as the NCHRP problem statement, and it was put forward at the annual meeting of Delaware in 2007. This project has been approved, and it is planned to be implemented in NCHRP 12—82-82 "Developing Bridge Inspection Policy Based on Reliability" in fiscal year 2009.
The purpose of this study is to formulate a reasonable method to determine the appropriate inspection frequency of highway bridges. These methods will consider the reliability of the bridge system, including the design, detailed information, materials, age and function of the bridge, so as to determine the expected performance of the bridge and the degradation of the bridge and bridge units. Implementing the grading inspection method is a method to improve the overall efficiency. This method will help to determine the inspection interval before the deterioration begins. This will enable bridge owners to invest their limited resources in the most dangerous bridges.
The current practice has a great impact on the inspection and monitoring of existing resources. The successful application of this research achievement in the most risky bridges in the United States is expected to improve the safety and reliability of highway bridges in the United States and make bridge owners decide to concentrate their resources on dangerous bridges. The implementation of this study is expected to realize the policies and requirements for improving the existing bridge detection.
5.2 Formulation of Standards for Quality Assurance/Quality Control The investigation team also recommended the formulation of national quality control/quality assurance standards for use by national and local institutions. These guides will be prepared for internal staff, and similar guides can be used as part of the bridge inspection service contract. On the same subject as above, the proposal was submitted to the AASHTO Subcommittee on Bridges and Structures in August 2007. This project is implemented by AASHT0 and the bridge inspection standard designated as NCHRP 20-07/Task 252.
This project will study whether it is necessary to formulate better practices and improve quality control (QC) and quality assurance (QA) according to the requirements of National Bridge Inspection Standard (NBIS), so as to improve the safety of highway bridges, improve the quality and reliability of bridge inspection, and gradually promote the management of inspection plan. Due to the limited experience of state transportation departments in quality control/quality assurance, this project will meet the requirements of NBIS, allowing States to choose appropriate specifications. The contractor has been selected to carry out this work and is working out a detailed list of quality control/quality assurance suggestions for bridge inspection. The timetable will include the resources and performance measures required for each proposed practice. The project is expected to be completed in April 2009.
5.3 Provide reference manuals with illustrations and photos.
As mentioned above, many very detailed manuals and reference materials with a lot of explanations can be used as tools for bridge inspectors. The investigation team suggested expanding the use of illustrations and photos to describe the condition of the bridge, so as to improve the accuracy and consistency of the inspection. To support this recommendation, the inspection team investigated the FHWA branch office to determine which countries included photos and illustrations in their inspection manuals. The results show that among the contacts of 52 countries and regions, the report shows that 65,438+04 countries used inspection or coding manuals with some photos and illustrations, of which 23 countries answered no and another 65,438+00 countries or regions did not respond to the survey.
In addition, the investigation team needs to conduct a feasibility study to develop a method to expand the use of illustrations and reference documents.
The feasibility study of these objectives is:
(1) provides an ideal improvement for future coding guidelines and inspection manuals;
(2) To explore the extent to which the core content of AASHTO is used to guide local institutions in various states and the whole country;
(3) Investigate relevant documents to improve inspection procedures and provide additional resources and inspectors;
(4) Summarize the advanced practices of other industries and the improvement of quality assurance/quality control procedures by using illustrations, photos and reference manuals.
The ultimate goal is to determine a long-term project through FHWA or NCHRP, develop and improve testing resources, and use photos and illustrations as tools to promote highway bridge testing throughout the country. To this end, FHWA initiated a project:
(1) Evaluate and supplement the illustrations and photos used by various states as shown in the Illustration Manual (IM) to improve accuracy and consistency, including other industries evaluated in bridge inspection;
(2) set up a group to determine that the main traffic officials should attend the meeting to determine the best practices;
(3) Work with officials of the transportation department who have specific experience in formulating inspection specifications for graphic bridges;
(4) The inspection method will be included in the training and education plan of the manual, so that the manual update and legislative/management problems need to be solved to implement the recommendations of the research report;
(5) It is suggested to revise the inspection manual and guide of FHWA Bridge step by step.
The project started in the spring of 2008. It is expected that all the work will be completed on August 1 day, 2008.
5.4 Development of comprehensive inspection and maintenance methods
As mentioned above, most European institutions visited take the inspection leading to the investigation of the cause of damage as one of the bridge inspection steps. Train inspectors to evaluate structural unit damage, structural stability, user safety and the impact on the durability of damaged parts.
In order to support the transition to similar practices in the United States, the investigation team suggested exploring the preparation of a manual to provide a series of maintenance suggestions related to specific inspection conditions. This manual can be used to improve the training of inspectors and to inspect and maintain structures. Finland, for example, uses this manual.
The maintenance instructions of the administrative bridge are provided to the inspector (Figure 1) to help confirm the structural damage and understand the appropriate maintenance procedures after observation. This manual will be helpful to make contact inspection rating and maintenance activities. The team also suggested exploring how to use manuals based on the existing core content of AASHT0 to achieve these goals. Other strategies recommended by the Action Team include more extensive implementation of nondestructive evaluation (NDT) within the scope of daily inspection of bridges to help provide better inspection means, more extensive evaluation of bridge conditions, and integration of inspection and maintenance. The team suggested that the National Highway Research Institute (NHI) training class discuss the nondestructive testing of highway bridges. In addition, the panelists suggested that practitioners should consider attending the meeting. For example, in February 2008, a conference on "Structural Materials Technology: Application of Non-destructive Testing Technology in Roads and Bridges" will be held in Oakland, California. Meetings like this usually include a routine seminar on nondestructive testing technology.
5.5 Exchange new discoveries and technologies in research activities.
Other valuable items are as follows:
(1) crack mapping and two-dimensional range representation are used to better explain the development of cracks in concrete structures with time;
(2) Applying nondestructive testing technology to provide brief technical data to help inspectors determine potential nondestructive testing solutions;
(3) Some countries can obtain the data of vehicles on the bridge, and the bridge inspection in the United States should also be done;
(4) The sustainable bridge project is funded by the European Union, and it has made great efforts in exploring the nondestructive testing bridge condition assessment. The information obtained from this project is very valuable to American practitioners.
In addition, during the investigation, it was found that Finland is unique in implementing some very innovative quality assurance/quality control activities. It is suggested to have more technical exchanges with representatives of Finnish Highway Administration.
5.6 Shear Wave Ultrasonic Sensor
Ultrasonic shear wave sensor (Figure 2) images the sound waves embedded in the internal features of concrete structure, which was demonstrated in investigation and interview. This technology was originally developed and produced in Russia and was not listed in the United States. This technology may be applied to some situations in the United States, including cavity detection after grouting of post-tensioned prestressed pipeline and more traditional applications, such as pulse velocity and layered detection. Pilot or demonstration projects can help transfer this technology to the United States. The NCHRPIDEA project or interested state transportation departments can provide funds to apply this technology in the United States. Technology transfer activities should be used to support the development of projects and demonstrate the technology in the United States. German Instruments has obtained the right to transfer this technology in the United States. If possible, the United States should supervise and support this technology.
5.7 Summary
Recently, the collapse of the 1-35w bridge in Minneapolis, Minnesota, USA, concentrated on the methods and practices to ensure the safety of highway bridges in the United States. In view of this country's concern and public pressure, there is still a lot of work to be done in the future in ensuring the safety of bridges and studying how to improve the current practices and practices. The results of the survey will certainly be helpful to this work.
Although the author does not think that the collapse of the 1-35 bridge directly led to the national inspection standards for bridges, it created an environment to encourage FHWA and owners to review the current practices and make appropriate and necessary modifications. We must take action to restore public confidence. Besides, it makes a lot of business sense.
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