The content of bridge inspection and inspection methods?

1 The significance of bridge inspection

Bridges in the long-term use of the process will inevitably occur a variety of structural damage, bridge inspection is to assess the bridge according to the actual situation, it mainly has the following two important significance:

One is through the use of the bridge condition, defects and damages to the bridge for a comprehensive, detailed, in-depth on-site inspection, clear defects and damages of the nature of the site, parts, Severity and development trend, looking for defects and damage to the causes, in order to analyze and evaluate the defects and damage to the bridge performance and bearing capacity of the impact of the bridge maintenance, reinforcement and transformation design to provide timely, targeted first-hand information.

The second is through the comprehensive testing of bridges, systematically collect the current bridge technical data, accumulation of technical information, to enrich the bridge database, strengthen the scientific management of bridges and improve the technical level of bridges to provide the necessary conditions; through the rational design of the detection method, supplemented by the deployment of long-term monitoring equipment, and gradually establish a bridge health monitoring system, to ensure that the bridge long-term safe operation, in order to give full play to its best economic and social benefits. economic and social benefits.

2. Bridge testing based on

Bridge testing is mainly based on the Chinese people's **** and the country, the Ministry of Transportation and the Ministry of Construction and other standards issued by the standards and norms, the relevant technical standards of the norms are as follows:

(1) "highway project quality appraisal methods" Jiaohua Highway No. 446;

(2) "Highway Maintenance Technical Specification) ( JTJ73-96);

(3) "Highway Engineering Technical Standards" (JTGB01-2003);

(4) "Methods of Identification of Old Highway Bridges Bearing Capacity (Trial) Bridge Design Guidelines" (CJJ11-93);

(5) "Design Load Standards for Urban Bridges" (CJJ77-98) JTJ073.

3 Types of Bridge Inspection

The types of bridge inspection are divided into three kinds: recurrent inspection, periodic inspection and special inspection. Regular inspection refers to the road section inspector or bridge maintenance personnel in a variety of weather conditions to observe the bridge, the purpose is to ensure that the bridge structure functions normally, so that the structure can be timely maintenance and emergency treatment, and report on some major problems. Regular inspection is to rely on experienced full-time bridge inspection engineers to visually observe the bridge, supplemented by necessary tools, conventional measuring instruments, cameras and other equipment, etc., to determine the cause of the disease in the field, to make a quality rating, and to estimate the scope and method of repairs required, or to put forward proposals to limit traffic, is a comprehensive inspection of the quality of the bridge structure to track the situation on a regular basis. Special inspection is a comprehensive inspection, strength measurement and deficiency measurement of the bridge by experts based on certain physical and chemical non-destructive inspection methods for various special reasons, aiming at finding out the definite cause, degree and scope of damage, analyzing the consequences of damage and the dangers that potential defects may bring to the structure.

4 bridge inspection content

4.1 inspection points

Bridge inspection can usually be based on the bridge type to determine the main points of the investigation, such as girder bridges, the inspection points are: cracks in the middle part of the span, deflection; end of the diagonal cracks; the condition of the main girder joints; the appearance of the quality of the components and so on. Arch bridge inspection points are: arch ring vault cracks, pier displacement, etc., through the appearance of the inspection can be analyzed to determine the cause of bridge disease.

4.2 Inspection content

Bridges can be divided into superstructure, substructure and subsidiary structure in general. The superstructure in the girder bridge mainly refers to the main girder; substructure including piers, abutments, foundations and bearing platforms, piles, etc.; ancillary structures have bridge deck, railings, expansion joints, etc.. Each part has its own stress characteristics, disease also has some **** sex, if the appearance of the disease is not conventional, should be carefully studied to find out the cause of the disease.

The content of bridge superstructure testing includes hollow slab girder concrete strength, hollow slab girder concrete carbonation depth and girder crack condition and distribution pattern. Bridge substructure testing content includes dun platform crack condition and distribution pattern and frame abutment weathering, spalling, cracking, misalignment, sinking and horizontal displacement or rotation. Bridge deck system inspection content includes bridge deck pavement, sidewalks, railings, drainage facilities and expansion joints. Mainly from the following aspects to check: the deck pavement has no cracks, spalling, puddle water, potholes, waves and bulging; sidewalks and edges have no spalling, damage; railing system has no impact damage, loosening, cracking, downward deflection, arching, skewed and members of the concrete cracking; yamen surface water drainage facilities have no damage, blocking and leakage; expansion joints are not broken, whether its function is normal and so on. Bridge bearing test content includes bearing function is intact, whether the component is complete and clean; base, beam bottom, roller concrete is cracked; seat plate, toothed plate there is no de-welding; there is no fracture, misalignment and dehollowing phenomenon; rubber bearing is aging, deformation, failure and so on.

4.3 Detection steps

First of all, the bridge survey and calculation, if the data collection. Data collection involves a lot of details, such as design data inside the calculations, design drawings, revised drawings and geological data, etc.; construction data inside the various stages of the completion of drawings, completion instructions, material test data and construction records, completion and acceptance data, etc.; other maintenance, maintenance data include the history of the passage of the special vehicles, the traffic volume, maintenance and repair data, etc..

Secondly, it is the bearing capacity calculation. When the overall characteristics of the bridge after some understanding, but also should do some of the necessary calculations. Calculation of the principle of the relevant technical specifications, but it should be noted that some specific parameters should be based on the actual bridge, the discount should be discounted, if necessary, should also consider certain favorable factors. Through the calculation, we can judge whether the safe bearing capacity of the bridge structure meets the design requirements and evaluate the construction quality and operation conditions of the bridge. As for old bridges, we can explore their bearing potential and make recommendations for reinforcement or reconstruction of active bridges that cannot meet the requirements.

5 Methods of bridge inspection

5.1 Rebound inspection method. Rebound method is the use of rebound meters to detect the compressive strength of concrete. The rebound meter is a mechanical non-destructive inspection instrument, because the compressive strength of concrete and its surface hardness there is a certain relationship between the rebound meter of the hammer by a certain elasticity of the blow on the concrete surface, the rebound height (through the rebound meter read rebound value) and the concrete surface hardness into a certain proportional relationship. With the rebound method to detect the compressive strength of concrete equipment is simple, easy to operate, rapid testing, so in the field of direct measurement in the use of more.

5.2 dynamic test method. Bridge detection dynamic load test is the basic test of the power determination evaluation method, the content is mainly structural dynamic characteristics and dynamic load response test and analysis, measurement of the main part of the structural dynamic effect of the largest components of the dynamic stress and dynamic deformation of the control cross-section. Generally speaking, the testing program mainly includes bridge dynamic characteristic modal parameter test (frequency, vibration shape, damping ratio) and bridge dynamic response test (dynamic deflection, dynamic stress, acceleration, impact coefficient). Determination of the intrinsic frequency of the bridge structure is relatively simple, only the first-order frequency of the structure, the structure is more complex power analysis, should also consider the second, third and higher-order frequency. Bridge intrinsic frequency can be determined directly through the test system measured and recorded on the power spectrogram of the peak, time domain course curve or its autocorrelation diagram. The dynamic stiffness of the load-bearing structure can also be deduced from the fundamental frequency.

The test of the impact coefficient is usually done by determining the dynamic strain or deflection of the structure. Before the test, in the span of the beam (or the maximum displacement, strain) arrangement of resistance strain gauge or strain gauge, and through the dynamic strain gauge connected to the computer. During the test, a loaded vehicle is driven from the measurement point at a certain speed, and the real-time signal of its output strain over time is recorded. In general, the output strain results at various vehicle speeds should be tested and recorded for analysis and comparison. Generally speaking, the bridge in the span L for 30-70m, the vehicle and the bridge of the self-oscillation frequency is close to, easy to produce *** vibration, in a single vehicle under the action of the impact coefficient is particularly large; impact coefficient with the reduction of the damping ratio increases, the smaller the damping ratio, the impact coefficient of the bridge by the impact of the bridge is more pronounced, the impact coefficient of the pre-stressed concrete beam bridge is greater than that of the same span of the reinforced concrete The impact coefficient of prestressed concrete girder bridge is larger than that of reinforced concrete girder bridge of the same span, which need to be noted in the test in order to better analyze the test results of impact coefficient. In fact, the measured vehicle impact coefficient is not only related to the structure itself, but also to the nature of the test vehicle, road surface smoothness and vehicle speed. The vehicle load itself is a vibration system with mass, and when it travels on the bridge, it produces coupled vehicle and bridge vibration with the bridge. Due to the complexity of the vehicle dynamic characteristics, as well as the discrete nature of the bridge damping and the randomness of the unevenness of the bridge, the same bridge many different tests, the measured impact coefficient is not the same.

5.3 Load test. Bridge power load test refers to the use of power loads such as traveling car load or other power load on the bridge structure, in order to measure the dynamic characteristics of the structure, so as to determine the bridge structure in the power load by the impact and vibration effects of the test. Usually, the vehicle loading method is adopted to determine the strain, deflection and crack of the beam, and the actual bearing capacity of the bridge is judged according to the comparison and analysis of the test results and the calculated value of the sink. This load test is non-destructive, according to the nature of the role of the test load, usually divided into static load test and dynamic load test, the former reflects the bridge in the static load under the action of the structural performance, the latter reflects the dynamic performance of the bridge structure static load test. Static load test is a static load acting on the bridge at a specified location. In order to be able to test the structure of the static strain. Static displacement and cracks, etc. In order to deduce the bridge structure under the action of the load of the working state and the use of the ability of the test. The general analysis and evaluation work mainly includes the evaluation of the working condition of the structure, the strength and stability of the structure, foundations and foundations, structural rigidity requirements, cracks and so on.

6 Conclusion

Bridge inspection is a requirement for quite detailed work, bridge inspection methods are many, the inspector should not only have a wealth of practical field experience, but also have a solid theoretical foundation as a guide. Only by fully combining theory and practice, coupled with the tacit cooperation between the conductor and the various test personnel, in order to do a good job of inspection and obtain satisfactory data to make an accurate assessment.

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