Detection technology and application of concrete bridge?

The detection technology of concrete bridge and its application are very important. The reasonable application of detection technology can record detailed data, and every detail is very important. Zhong Da Consulting will introduce the detection technology and application of concrete bridges to you.

With the development of economy, more and more concrete bridges are erected on urban and rural roads. In the process of concrete bridge construction, due to material defects, construction errors and the erosion of the use environment, many bridges are damaged with the extension of time, and the annual cost for maintenance and reconstruction increases year by year. Bridges such as Beijing Dabeiyao Bridge and Xizhimen Overpass were overhauled, demolished and rebuilt in less than 20 years, which wasted a lot of money. Therefore, bridge quality inspection is a very important work to avoid waste of funds and reduce engineering accidents, and this inspection technology has attracted more and more attention.

At present, bridge structure testing is a process of testing, testing, judging and evaluating the bearing capacity, material quality and working performance of new and existing bridge structures. The main contents include two aspects: on the one hand, the overall performance and functional state detection of new bridge structures, including the identification of structural bearing capacity and service performance; On the other hand, it is the detection of the disaster resistance and disaster prevention ability of existing bridges in the operation process, including the identification of the bearing capacity and service performance under the conditions of flood, fire and earthquake in the use process; On the other hand, it is the detection of various properties of bridge structural materials, including the analysis and judgment of physical, chemical and mechanical properties of materials and the causes of defects.

1. Bridge detection instruments and equipment

Instruments, equipment, test components and technologies for bridge inspection are important guarantees for bridge inspection, and must be scientific and accurate. In the static load and dynamic load tests, the main test contents include the magnitude of force, the distribution and magnitude of various stresses on the cross section of the structure, the damage of local structure, the dynamic stress, natural vibration characteristics and dynamic deflection of the structure under dynamic load.

Test instruments include electric tester, optical instrument, entrance instrument, mechanical test instrument, servo instrument, etc. Specific instruments include direct reading, automatic recording, analog and digital. In bridge detection, it is required to reasonably select the measuring range, precision, sensitivity and anti-interference ability of the instrument, and the instrument should be as simple, portable, durable and versatile as possible. The specific selection should be based on the environment where the bridge is located and the requirements for determining specific parameters. Commonly used test instruments include dynamometer, strain gauge, displacement gauge, inclinometer, vibrometer and so on.

2. Detection of bearing capacity and service performance of new and old bridge structures

The detection of bearing capacity and service performance of new bridges and existing bridges mainly includes acceptance of new bridges and evaluation of existing bridges after various disasters.

The overall performance test of highway bridge structure can be divided into static load test and dynamic load test according to the stress state. Bridge static load test is to test the static displacement, static strain, cracks and other parameters of the structure by applying static load at the designated position on the bridge, so as to infer the working performance and service performance of the bridge structure under load; Dynamic load test is to excite the vibration of the bridge structure by some exciting way, and measure the natural frequency, damping ratio, vibration mode, dynamic impact coefficient and traffic direction of the bridge structure, so as to judge the overall stiffness and traffic performance of the bridge structure. Static load test and dynamic load test are two kinds of tests, although the purpose and content of the test are different, but they are equally important for comprehensively analyzing and mastering the working performance of bridge structures.

As far as the influence of tests on structures is concerned, bridge tests can be divided into destructive tests and non-destructive tests. Generally speaking, there are some specific problems in the destruction test of prototype structure, both in cost and method, especially after the structure enters the destruction stage. Therefore, most appraisal tests are nondestructive testing. However, in some cases, in order to achieve the predetermined test purpose, it is often necessary to carry out destructive tests to master the test data such as structural behavior and failure form when the test structure enters the plastic stage or even the failure stage. At this time, the model structure is mostly taken as the object, which is carried out in the laboratory to facilitate loading, control, measurement and analysis, so as to summarize the laws with universal significance and popularize them to the prototype structure.

According to the duration of the test, it can be divided into long-term test and short-term test. Identification tests and general research tests mostly adopt short-term test methods, while long-term test methods only adopt those influencing factors that must be observed for a long time, such as shrinkage and creep performance of concrete structures and settlement of bridge foundations. In addition, for large-scale bridge structures or newly-built bridge structures, the information of long-term service performance of these structures is often accumulated through long-term observation or regular inspection.

3. Various performance tests of bridge structure material concrete.

At present, concrete is one of the most widely used bridge structural materials in China. It is a mixed material composed of cement, sand, stone, water, additives and additives. After weighing, stirring, transporting, pouring, molding and curing, the strength is formed. Due to the complexity of its constituent materials and numerous procedures, the physical and mechanical properties of concrete after setting and hardening may be quite different from the design. At present, for the quality of Confucius concrete, the performance of concrete is mainly tested from several aspects: first, whether the strength of concrete meets the design requirements; The other is to detect whether the defects of concrete members affect the bearing capacity of the structure; The other is to detect the geometric size of concrete members, the position and quantity of internal reinforcement, corrosion state and so on. , and whether the size and reinforcement of components meet the design and specification requirements; There are other properties of concrete members, including thermal performance of buildings, waterproof and sound insulation.

3. 1 concrete strength determination.

For the determination of concrete strength, the current detection methods mainly include rebound method, ultrasonic method, ultrasonic-rebound comprehensive method, penetration method, pull-out method, fracture method, core sampling detection method and so on. Rebound method, ultrasonic method and their synthesis method belong to nondestructive testing methods, and the strength of structural concrete is estimated by using the relationship between some physical quantities of concrete and strength. The instruments used are simple and convenient to operate, and are widely used in engineering field. Penetration method, pull-out method, fracture method, core sample test method and so on. All of them are semi-destructive methods, which cause some damage to the structure, and the number and scope of tests are limited. Generally speaking, a small number of tests are carried out on components with less stress and unimportant to correct the concrete strength measured by non-destructive methods.

3.2 Inspection of material defects of components.

Common defects in parts include cracks, chipping, spalling, delamination, honeycomb, cavities, environmental erosion and steel corrosion. Among them, the defects exposed by components can be visually detected by means of appropriate tools or measuring tools and other auxiliary equipment. Ultrasonic pulse velocity method can be used to detect cracks, cavities, slag inclusion and fire damage in steel, weld and concrete. Acoustic detection method refers to tapping the component with a tool and listening to the difference of its sound to judge whether the component is damaged. This method is relatively simple and is commonly used in general inspection. Pulse radar electromagnetic echo method is an effective method to detect asphalt concrete bridge deck. Infrared thermal imager can also be used to measure the infrared energy radiated by various parts of concrete components, and the thermal image formed according to the temperature field distribution on the surface of the components can directly show the discontinuous defects in the joint between concrete and structure.

3.3 The geometric dimensions of concrete members, the position and quantity of internal steel bars, and corrosion shall be detected.

The geometric dimensions of concrete members can be measured by simple length measuring tools such as meter ruler; The detection of steel bars in concrete is carried out by magnetic measurement, which is based on the method that steel bars or embedded iron pieces will affect the magnetic field. Mainly detect the position, diameter, quantity, stirrup spacing and thickness of concrete protective layer of steel bars, and check whether it meets the design and specification requirements. The modified state of steel bars in concrete members can be detected by electrical measurement, and the corrosion state of steel bars can also be indirectly detected by detecting the resistivity and alkalinity of concrete and the content of concrete in corrosive media.

3.4 Other performance tests of concrete members. The thermal performance, waterproof, sound insulation and other physical properties of concrete members can be detected by various instruments.

4. Evaluate or reinforce according to the detected structure.

Through the data results of various tests, the detection bridge is evaluated and identified. Firstly, the environment and present situation of the bridge are investigated to obtain the maintenance and disaster situation of the bridge; Then understand the situation of bridge design, be familiar with the construction drawings of buildings and structures, and test the performance of structural concrete materials, such as the above strength, size, reinforcement, defects, etc., whether they meet the design and specification requirements; According to the results of investigation and material test, a calculation model is established to calculate whether it meets the requirements of bearing capacity and deformation; Through static and dynamic load tests, the working performance of the bridge under load and load is tested.

When the bridge structure can't meet the requirements of bearing capacity and traffic capacity (increased traffic volume, post-disaster, etc. ), the bridge needs reinforcement or technical transformation. Common reinforcement techniques include reducing dead load, strengthening critical members, supplementing new members, improving the original structural stress system or strengthening main load-bearing structural members, so as to improve the overall bearing capacity of the bridge; Common technical transformations include structural reinforcement to meet the requirements of bearing capacity, bridge deck widening to meet the requirements of traffic capacity, and structural mechanical performance improvement to meet the requirements of use. Bridge reinforcement and technical transformation should be combined with test data to obtain an economical and feasible scheme.

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