1 Check and measure the surrounding environment of the approach bridge.
(1) Check whether the connection between the main bridge and the approach bridge and the approach bridge (line) is normal and whether there is any change compared with the completed situation. 5 1- paper-net-welcome.
(2) Whether the bridge site and its adjacent waterways have changed. If necessary, it is also necessary to determine whether the velocity of the main channel and the clear width under the bridge have changed. Whether the local scour at piers and abutments is increased by 5 1- paper net-welcome.
(3) Whether there is scouring, sliding and damage on the rock cone slope filled at the bridgehead on both sides of the bank. 5 1- paper-net-welcome.
2. Measure the elevation and alignment of the guardrail bridge.
(1) The elevation of the bridge is related to the alignment, but there are differences. The former refers to the elevation value of a certain point, and the latter refers to the connection of relevant points of the bridge. A bridge with good design and construction quality should meet the design expectation. 5 1- paper-net-welcome.
(2) The main parts and items to be measured are: the elevation of the top surface of abutment bearing pad, the top surface of bearing platform and the bottom of beam; Whether the pier body is deviated or inclined in the longitudinal and transverse directions ① For cable-stayed bridges and suspension bridges, it is also necessary to measure whether the main tower body is deviated or inclined in the longitudinal and transverse directions; ② For suspension bridges, it is also necessary to measure the main cable shape; (3) The arch bridge should also measure the arch rib axis alignment 5 1- paper-net-welcome.
3, masonry beam arch inspection measurement
(1) Check the masonry for weathering, peeling, damage and cracks. Pay attention to the situation of variable cross section, reinforcement and repair and waterproof layer. Pay attention to the corrosion of steel bars at the peeling crack of masonry. 5 1- paper-net-welcome.
Reinforced concrete beams should focus on checking vertical cracks with a width greater than 0.2 mm, and pay attention to checking whether there are oblique cracks and longitudinal cracks along the direction. The change of camber of prestressed reinforced concrete beams should be observed, and whether there are vertical cracks perpendicular to the main reinforcement should be checked. 5 1- paper-net-welcome.
(2) The actual arch axis and arch ring (or arch rib) size of the arch bridge should be measured to check whether they have transverse (perpendicular to the route direction) cracks. 5 1- theory
4, steel structure inspection and measurement
(1) Check whether the paint coating of steel structure members is intact, such as peeling, peeling, rust spots, etc. It is easy to accumulate water and dust, or whether the parts that are not ventilated are rusted. The actual residual thickness of steel plate or member should be measured to consider the influence of section weakening. 5 1- paper-net-welcome.
(2) Check for cracks, perforations, bruises, hard bends, skewness, skin explosion and material interlayer. Pay attention to whether there are fatigue cracks in the following parts: the joint between the member under tension or repeated stress and the joint plate or the joint of the member (structure); Due to the damage, the section of the bar (structure) is weakened and the stress is concentrated; Angle steel connecting longitudinal beam and cross beam; Angle steel of upper flange of longitudinal beam without cover plate; Nodes of longitudinal connection system between main beams; The welding end of a single shear rivet and its nearby base material; U-shaped rib and diaphragm joint weld, etc. 5 1- paper-net-welcome.
(3) Check whether there is any abnormality in the big girth weld at the splicing of steel box girder (i.e. girth weld at the top plate, bottom plate and web plate of the same section) and the welding at the splicing section of U-shaped rib. 5 1- paper net-Welcome.
(4) Check the straightness of the bar. When the bending vector of the city pole is greater than the free length of the pole 1‰ and the bending vector of the tie bar is greater than the free length of the pole 1/500, we should pay attention to the bending influence of 5 1- paper-net-welcome.
(5) Check whether the rivet head is rusty or loose, and check whether the high-strength bolt is intact, loose or delayed; Whether there is any phenomenon of reducing friction due to corrosion or other reasons; And should pay close attention to the joint slip camber change 5 1- paper-net-welcome.
5, masonry inspection and measurement
Brick masonry is different from reinforced concrete, its tensile strength is small, and the brittle cracking load of the structure is close to or almost equal to the failure load. Therefore, when cracks occur in brick masonry due to load, it is often the failure feature or precursor of masonry.
6, pier and foundation inspection and measurement
(1) The main defects of pier and abutment are cracks, peeling, cavities, exposed and corroded steel bars, aging, deformation and displacement, etc.
(2) During inspection, measure and describe the specific location, width, length and depth of cracks and damage, and draw it as Figure 5 1- paper-net-welcome.
7. Basic inspection
When the settlement, inclination and displacement of piers and abutments occur, it is necessary to detect and discuss the foundation. 5 1- bridge completion detection is difficult and troublesome. Static sounding and drilling sampling methods can also be used to test the load plate, but it is difficult to do it in situ. Often just near the foundation. Rock foundation can be tested at the outcrop of bedrock. five
8. Test content
8. 1 deck system
Bridge deck system includes bridge deck pavement, sidewalks, railings, drainage facilities and expansion joints. Check mainly from the following aspects:
(1) Whether there are cracks, peeling, pits, waves, bulges and other water accumulation phenomena on the bridge deck pavement;
(2) The sidewalks and kerbs are free from peeling and damage;
(3) Whether the railing system is damaged, loose, cracked, bent, arched, skewed or cracked in concrete;
(4) Bridge deck drainage facilities are damaged, blocked and leaking;
(5) Whether the expansion joint is damaged and its function is normal.
8.2 Superstructure
(1) concrete strength of cast-in-place concrete beam;
(2) carbonation depth of cast-in-place concrete beam;
(3) The crack condition and distribution law of the beam.
8.3 substructure
(1) pier and abutment cracks and their distribution;
(2) Weathering, peeling, cracking, dislocation, sinking, horizontal displacement or rotation of the frame pier.
8.4 support
(1) Whether the bearing function is in good condition;
(2) Whether the parts are complete and clean;
(3) Whether the concrete of the base, beam bottom and roller shaft is damaged;
(4) Whether the seat plate and the toothed plate are welded off;
(5) Whether there are fractures, dislocations and holes;
(6) Whether the rubber bearing is aging, deformed or invalid.
9. Concrete inspection and evaluation methods
9. 1 concrete strength testing
Using a rebound instrument, the measuring area is selected by sampling. The measuring area is mainly selected in the most unfavorable part of the component, and the measuring area is within 0.2m×0.2m, and the measuring points are evenly distributed in it. According to Technical Specification for Testing Compressive Strength of Concrete by Rebound Method (JG/T23—200 1), each survey area takes 16 rebound values.
9.2 Measurement of carbonation depth of concrete
At or near the measuring area where the rebound value is measured, drill a hole with a diameter of 1 6mm and a depth of15mm with an impact drill, clean it, and drop phenolphthalein alcohol solution with a concentration of1on the edge of the cut-out part. After a short pause, use vernier caliper or steel ruler to measure the distance between the interface of carbonized and uncarbonized concrete and the concrete surface for 3 ~ 4 times, and each reading is accurate to 65438 0 mm. ..
9.3 Crack detection
Observe and measure the crack width with a graduated magnifying glass.
9.4 compressive strength test of cast-in-place concrete
The strength of concrete is determined by the carbonation correction method of rebound value. Comprehensive determination of concrete strength by carbonation resilience refers to a method of measuring the rebound value and carbonation depth of structural concrete in the same measurement area with a rebound instrument, and then correcting the rebound value with carbonation depth, thus calculating the concrete strength in the measurement area. This method has the following characteristics: reducing the influence of age and moisture content, making up for the deficiency of each parameter and improving the measurement accuracy. This bridge adopts sampling inspection method, and selects representative members for inspection as the reference value of concrete strength of this bridge. Measure the carbonation depth value and rebound value in each measuring area respectively.
10. Evaluation method of bridge bearing capacity
At present, the evaluation of bridge bearing capacity can be divided into four categories: empirical evaluation method based on disease investigation, analytical calculation method, comprehensive analysis method and load test method.
10. 1 Empirical evaluation method based on disease investigation
The main basis of this method is Technical Specification for Highway Maintenance (JTJ 073-96). On the basis of bridge inspection, through the investigation of the technical condition, the nature, location, severity and development trend of bridge defects and damages, the main causes of defects and damages are found out, and the influence of existing defects and damages on bridge quality and service bearing capacity is analyzed and evaluated, so as to provide reliable technical data and basis for bridge maintenance and reinforcement design. This method requires on-site inspectors to have rich engineering experience and professional knowledge.
10.2 analysis and calculation method
This method mainly evaluates the bearing capacity according to the measured material properties, structural geometric dimensions, supporting conditions, appearance defects and traffic load, and according to the calculation theory of bridge structure. It is a method to quantitatively understand the bearing capacity of old bridges. Scholars at home and abroad have done a lot of research work, and many countries tend to use the "identification coefficient" to evaluate the bearing capacity.
With the development of computer technology, especially the finite element theory of reinforced concrete, the finite element calculation method has attracted the attention of scholars all over the world. Compile finite element calculation program or use general finite element analysis software to calculate the actual bearing capacity of the bridge through computer simulation of the actual bridge load test. The evaluation steps are as follows: ① Bridge investigation; (2) Determine the loading form and divide the units; ③ Graded loading calculation; ④ Assess the bearing capacity.
10.3 comprehensive analysis method
On the basis of bridge inspection, this method non-destructively measures the concrete strength, concrete carbonation depth, concrete chloride ion content, concrete resistivity, reinforced concrete cover thickness and steel corrosion in structural concrete, checks the reduced structural bearing capacity, comprehensively analyzes the calculation results and structural cracks and other appearance conditions, and evaluates the structural material condition.
10.4 load test method
As mentioned above, the empirical evaluation method and comprehensive analysis method based on disease investigation are effective for the preliminary evaluation of bridge bearing capacity, especially for the overall evaluation of the whole bridge, the classification of bridge types and the determination of priorities for maintenance and reinforcement. However, for important large bridges, further load tests are needed.
Determine the actual carrying capacity. The load test method has the longest application history in bridge structure evaluation. Its main advantages are intuitive and reliable, so it is often used in the research of new structures and the evaluation of bridge quality. In the evaluation of old bridges, it is often used in the evaluation and research work under the condition that the actual working state of bridges is not clear, in order to make up for the deficiency of the evaluation method based on appearance investigation and comprehensive analysis. However, in general, it is necessary to close the route when carrying out the load test, which is costly and time-consuming, and the load test can only be carried out on important large bridges. This load test is non-destructive. According to the nature of test load, it is usually divided into static load test and dynamic load test. The former reflects the structural performance of the bridge under static load, while the latter reflects the dynamic performance of the bridge structure. Static load test usually uses vehicle to measure the strain, deflection and crack of beam. According to the comparative analysis of test results and theoretical calculation values, the actual bearing capacity of the bridge can be judged.
1- paper net-Welcome.
Two methods of bridge detection and positioning
The process of adjusting or modifying the theoretical model of the structure to make the modified modal parameters consistent with the experiment is the finite element model update 5 1- paper net-
In bridge monitoring, the model updating method is mainly used to comprehensively compare the vibration response records of experimental structures with the calculation results of the original model. By directly or indirectly measuring modal parameters, acceleration time history records, etc., the stiffness and mass information in the model are continuously updated through conditional optimization constraints. The main methods are as follows:
(1) matrix method is the earliest and most mature method to modify the overall matrix of calculation model. It has the characteristics of high precision and easy realization. The main disadvantage is that the physical meaning of the modified model is not clear, and the strip characteristics of the original finite element model are lost. This means that it belongs to Boehlmann/baruch optimal method 5 1- It's up to you.
(2) The sub-matrix correction method corrects the structural stiffness by defining the correction coefficient of the word matrix or the element matrix to be corrected and adjusting the correction coefficient of the word matrix. The biggest advantage of this method is that the modified stiffness matrix still maintains the symmetry sparsity of the original matrix 5 1- paper-net-welcome.
(3) The structural parameters are modified by sensitivity method, and the finite element model is modified by modifying structural design parameters, such as elastic modulus E and cross-sectional area A..
2 Fingerprint analysis to find the dynamic fingerprints related to the dynamic characteristics of the structure and judge the real state of the structure through these fingerprint changes 5 1- on you
In on-line monitoring, frequency is the easiest to obtain modal parameters with high accuracy, so it is the simplest to identify whether the structure is damaged by monitoring the change of frequency. In addition, vibration mode can also be used for structural damage. The accuracy of vibration mode test is lower than that of frequency, but vibration mode contains more damage information. There are many ways to judge whether the structure is damaged by vibration mode. MACCOMAeCMSDI and flexibility matrix method 5 1- paper-net-welcome!
However, a large number of model and actual structural experiments show that the natural frequency changes little due to structural damage, but the modal form changes obviously. In general, the natural frequency changes within 5%. It is generally believed that the natural frequency is directly used as the monitoring fingerprint of the bridge, while the modal shape is sensitive to the local stiffness, but it is difficult to measure it accurately. MACCOMACCMS and others all encounter the same problem by relying on vibration-type dynamic fingerprints. Some people have established various bridge performance evaluation expert systems based on fuzzy theory and structural reliability theory, but first of all, they must establish various specifications and expert databases.
Concluding remarks
Bridge inspection is a dangerous work at high altitude with complex technology, difficult operation and high technology content, and the engineers and technicians who undertake the task have great responsibilities. Only by fully combining practice with theory can engineers and technicians make correct detection and evaluation of bridges and design feasible reinforcement methods, thus improving the service capacity of bridges and prolonging their service life.
3. Test basis
Bridge inspection is mainly based on the standards and specifications issued by People's Republic of China (PRC), Ministry of Communications and Ministry of Construction, and the relevant technical standards are as follows:
(1) Technical Specification for Highway Maintenance (JTJ 073-96);
(2) Technical Standard for Highway Engineering (JTGB 01-2003);
(3) Appraisal Method for Bearing Capacity of Old Highway Bridges (Trial) (1998);
(4) Standard for Test Methods of Concrete Structures (GB 50152-92);
(5) Technical Specification for Testing Compressive Strength of Concrete by Rebound Method (JTJ/T23-2001);
(6) Standard for Quality Inspection and Evaluation of Highway Engineering (JTJ 071-98);
(7) General Code for Design of Highway Bridges and Culverts (JTGD 60-2004);
(8) Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts (JTGD 62-2004);
(9) Code for Design of Urban Bridges (CJJ1I-93);
(10) design load standard for urban bridges (CJJ77—98)JTJ073.
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