I. Overview of Bridge Quality Inspection
Bridge quality inspection mainly uses special inspection technology and equipment to inspect the parts with obvious disease characteristics and the typical stress parts of the bridge in depth and in detail. Through quality inspection, we can master the technical condition and working condition of the bridge more comprehensively. Quality inspection generally includes the following aspects:
1. Measurement of geometric state parameters of bridge: mainly measure the overall linear shape of the structure and evaluate the stiffness of the bridge from a macro perspective;
2. Investigation on the change of bridge structure dead load: mainly investigate the structure size, deck pavement thickness and other additional loads on the bridge;
3. Concrete strength testing: generally, rebound method, ultrasonic rebound synthesis method and core sampling method are used to comprehensively evaluate concrete strength;
4. Detection of steel bar distribution: use a steel bar detector to detect the distribution of steel bars and the thickness of concrete protective layer;
5. Determination of corrosion potential of steel bars: select key stressed parts to check the corrosion potential of steel bars and judge the possibility of corrosion of steel bars;
Second, the problems existing in the quality inspection work
1. Lack of understanding of the importance of quality inspection, some quality inspection practitioners are not serious and responsible, do not pay attention to accuracy, but are careless and perfunctory.
2. Quality inspectors have low professional quality, low detection technology level and lack of internal senior management personnel and technical measures.
3. The testing equipment is aging, and the introduction of advanced testing instruments and equipment is lacking. The introduction of advanced equipment is an important guarantee to further improve the testing quality.
Third, measures to improve bridge quality testing
1. Close the design.
It is necessary to clarify technical standards and strengthen standard work. Design data, construction specifications, operating procedures, process points, quality inspection methods and evaluation standards of various projects, as well as engineering supervision methods and implementation details. Unified to the construction unit and the construction unit, so that everyone has a clear goal, rules to follow, laws to follow; Modern engineering construction should pay attention to technical aesthetics and emphasize the overall consideration of aesthetic function and practical function; The construction organization design, construction scheme and other documents prepared by each construction unit shall be sent to the construction unit and supervision engineer before the start of construction.
2. Improve the quality of testers, and improve quality inspection institutions and engineering quality management system.
First of all, through technical training, let all personnel involved in the construction master the construction technology and technical requirements of each construction process, so as to know what they are doing, how to do it and to what extent. Secondly, perfecting the legal system is an important guarantee to improve the quality of highway engineering. For laws and regulations, China has promulgated the Highway Law and related industry standards. This requires the transportation authorities to strictly control these quality inspection institutions. Adhere to strict examination and approval, regular inspection and regular evaluation. Resolutely rectify or ban unreasonable quality inspection units, and never be soft.
3. Grasp the determination of construction control parameters
Construction control parameters usually refer to some key data that can guide construction and control construction quality. For example, the optimum water content and maximum density of subgrade filler are the key parameters to guide construction and control compaction quality. The accuracy of these parameters will directly affect the quality of subgrade engineering. Therefore, when determining parameters by means of test detection, we should take it seriously, strictly follow the test detection rules, and strive to eliminate test errors, improve test accuracy and ensure the accuracy and reliability of test data. Secondly, the quality control of road materials. Raw materials, semi-finished products and finished products (such as fillers, sand, stones, cement, steel bars and prefabricated components, etc.). ) should be in accordance with the relevant test and inspection procedures and technical regulations for inspection. It can only be used after inspection. It is forbidden to use unqualified materials.
4. The quality control of site construction process should be fair.
In the process of construction, the quality control of the project mainly includes self-inspection by the construction unit, random inspection by the supervisor and government supervision. First of all, for the construction party, it is necessary to establish a relatively perfect test and detection system, establish a site laboratory, equip relevant test and detection personnel, have special personnel in charge, conduct full-time quality inspection and adhere to the self-inspection system. For supervisors, it is necessary to truly implement the three-level supervision before, during and after the event, especially the supervision in advance, so as to prevent problems before they occur and solve them in time. In the process of supervision, make full use of the relevant test equipment in the laboratory of supervision center, take test detection as an effective means, and strictly control the quality, so as to control the construction quality. For regulators, it is necessary to really play the role of government supervision, conduct spot checks and timely acceptance evaluation. Find problems and solve them in time. Grasp the typical example, set an example, and safeguard the seriousness, authority and impartiality of the government's supervision over highway engineering quality.
1. Project overview
The total length of the bridge is 396m, and the span arrangement is16m+18× 20m+16m. The upper part is an assembled tubular T-beam, and the lower part is a double-column pier of1×1.2m. Each pier foundation is made of two φ 1.2m drilled concrete. Design technical standard: bridge deck width: clear 9m (roadway) +2×0.25m (safety belt); Design load: automobile grade 20; Loading: trailer I100; Seismic intensity: 8-degree fortification.
2. Contents and methods of detection
2. 1 travelling beam: ① inspection contents: disease status, whether there are cracks, damage, peeling, exposed tendons, leakage and honeycomb pits; ② Detection method: The disease is mainly detected by visual inspection, supplemented by telescope, magnifying glass and graduated magnifying glass.
2.2 Pier and foundation: ① Inspection contents: whether the pier body is cracked, whether the surface is weathered and peeled off, whether there are cavities, pits and exposed tendons, and whether there are skew, settlement and bulging; Whether the pile foundation is exposed and whether the surface concrete falls off due to water erosion.
② Detection method: Excavate the pile foundation of No.8 pier and observe its diseases. Mainly visual inspection, supplemented by conventional testing instruments and tools, such as inclinometer, steel tape measure, etc.
3. Test results
3. 1 travelling beam: Through the visual inspection and telescope observation of the whole bridge, the travelling beam is basically intact, and the transverse connection of the assembled tubular T-beam is firm, and there is no dislocation of diaphragm. There is no obvious damage, concrete spalling, exposed reinforcement and honeycomb pits on the beam. With the help of the full-house support in the eighth span, the cracks of four T-beams in the middle span were observed in detail. Twenty-eight cracks were observed, the width of which was 0.03 mm ~ 0.06 mm, far less than the allowable value of 0.25 mm, and the concrete cracking of T-beam was not serious.
3.2 Pier abutment and foundation: ① Pier column: the verticality is good, the concrete of No.9 upstream pier column is slightly damaged, the concrete is peeled off, and the steel bar is exposed. The upstream pier columns of 1 1, 12, 15 are slightly weathered, and coarse aggregate can be seen. (2) Foundation: The foundation was seriously scoured, and the bottom of the cap of pier 6 ~ 13 was hollowed out. The exposed length of the top of pile foundation No.8 ~ 1 1 is about 1m, and the top of pile foundation is eroded to some extent. The concrete surface layer falls off, and the coarse aggregate is clearly visible, but no steel bars are exposed during testing. During the construction of pile caps, the formwork support is poor and the concrete surface is rough.
4. Comprehensive evaluation conclusions and recommendations
From the quality inspection results, it can be seen that the roadway beam is basically intact, and the T-beam body has no obvious damage, concrete peeling, exposed reinforcement, honeycomb and pits, so it is not necessary to carry out reinforcement treatment.
Bridge inspection is the key to project quality management, an important management means for highway construction enterprises to save project costs and improve social reputation, and also an important guarantee for the country to build high-quality and high-standard highway projects. Doing a good job in quality inspection is not only related to the real situation of project quality, but also provides an important basis for project quality evaluation and completion acceptance, and also provides important reference materials for management and maintenance in the process of project use. The staff are required to have rich on-site practical experience and a solid theoretical foundation as guidance. Therefore, only by fully combining theory with practice, coupled with the tacit cooperation between commanders and testers, can we do a good job in testing and obtain satisfactory data.
This paper introduces the content of "Quality Inspection of Highway and Bridge Engineering". Welcome to Zhong Da for more information.
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