Overview
Roads and bridges are an integral part of the transport system, and the quality of roads and bridges often affects the safety and quality of operation of the entire road, making the management of the maintenance of bridges extremely important。
Currently, the maintenance management of bridges is mainly the cleaning of bridges and the repair of pit tanks; the inspection of bridges is based on manual visual checks and manual scoring to determine the condition of the bridge structures。
If the actual performance of the bridge is to be judged more accurately, to provide a basis for strengthening or overhauling the bridge, and on the basis of examination of the appearance of the disease of the bridge, it is necessary to conduct a further test and load test of the bridge structure material。
The scientific management of bridges is important, and in the event of a bridge accident, not only economic damage and greater political impact, emphasis must be placed on bridge detection, understanding of the procedures, detection projects and methods of detection of bridges and the acquisition of experimental data processing and analytical methods to improve the management of bridges。
The pilot testing of bridges provides immediate data and a basis for conservation management, which is extensive, technically complex and difficult, and the introduction of advanced detection equipment can significantly improve the accuracy and efficiency of the testing。
Ii. Bridge inspection
Bridge inspection, primarily a survey of the state of bridge technology, i. E. The nature, location, severity and trends of the defects and damage to the bridge, identifies the main causes of the defects and damage, analyses and evaluates its impact on the quality of the bridge and the use of carrying capacity, and provides reliable technical data and a basis for the repair and reinforcement of the bridge。
Bridge inspection is therefore an essential and essential component of bridge assessment, maintenance, repair and strengthening, and is a reliable assurance of the viability and correctness of the maintenance and reinforcement programme。
In accordance with the scope, depth, manner and purpose of the inspection, bridge inspections are divided into two main categories: frequent inspection of bridges and inspection of bridge structures。
1. Frequent inspection of bridges
Bridges are regularly inspected, including daily visits and regular inspections of bridges。
Daily inspection of bridges, usually once a month, is carried out by section maintenance personnel or bridge maintenance personnel. The aim is to keep abreast of the technical state of the bridge, to ensure that the bridge structure is functional, to detect problems and respond in a timely manner, and to report on bridges requiring further inspection and maintenance. Following storms and floods, bridges are inspected more frequently。
Bridges are inspected regularly, with a cycle of approximately three to five years. The objective is to regularly collect dynamic data on the technical state of the bridge structure, to include a bridge maintenance management system, to provide basic data for assessing the use of the bridge and to develop specific bridge maintenance plans. Regular inspections are usually organized by maintenance engineers with a certain level of inspection experience and trained in bridge inspection, familiar with bridge design, construction, etc。
While frequent inspection of bridges is also done using simple tools or instruments, it is mainly based on visual inspection of the appearance of the bridges, which is mostly based on surface phenomena and experience. Both types of inspections are carried out mainly by bridge management。
2. Special inspection of bridges (bridge structure)
The special inspection of bridges, which is based on regular inspection of bridges, provides a further accurate determination of the technical condition of the bridge, with technical personnel using specialized detection equipment, detection, detection and detection of the bridge using non-destructive detection techniques, in order to determine the cause, extent and extent of the damage, analyse the consequences of the damage and the potential hazards to the bridge structure, and provide a basis for assessing the durability and carrying capacity of the bridge and for determining the implementation programme for the maintenance works。
The following four situations usually require special inspection of the bridge:
(1) when the cause of the disease and carrying capacity of the bridge cannot be determined by frequent inspection of the bridge
(2) prior to major bridge maintenance reinforcement work
(3) in the aftermath of major natural disasters, accidents and special events such as over-heavy vehicles crossing bridges
(4) when the actual performance of the bridge structure needs to be assessed。
The special inspection of bridges (the inspection of the bridge structure) typically consists of three components: the inspection of damage to the exterior of the bridge, the detection of the bridge structure and materials, and the test of the bridge load。
Iii. Work processes and projects for the detection of bridges
1. The bridge detection process consists of three main phases:
Phase i: preparation phase. This includes commissioning, data collection, site surveys and the preparation of four elements of a bridge testing programme。
Phase ii: the external testing phase. Mainly equipment installation and data collection。
Phase iii: analysis phase. This involves statistical analysis and calculations based on data collected from outside industry and the preparation of bridge inspection reports。
The detection of bridges needs to be carried out from inside and inside in order to understand and determine the actual performance of the bridges and to provide a scientific basis for their daily maintenance and reinforcement。
2. Bridge field testing project
Bridge exterior testing includes inspection of the exterior disease of the bridge, detection of bridge structure materials and testing of bridge loads。
1. Inspection of the appearance of the bridge
In accordance with the ministry of transport's technical instructions for road conservation (jtj 073-96) and the technology for periodic inspection of roads and bridges (ministry of transport roads), the aim of which is to provide a preliminary and basic understanding of the damage to the structure of the bridge, and to rate and rate the damage to the bridge to provide the basis for the next inspection of the material of the bridge structure。
2. Material testing of bridge structures
On the basis of examination of the appearance and disease of the bridge, further inspection of the bridge's structural material is carried out on the more damaged bridges. The aim is to gain an in-depth understanding of the working state and potential adverse effects of the bridge's structural materials and to predict trends and provide a technical basis for judging the durability and reliability of the bridge. Material testing of the bridge structure focused on the erosion of the bridge structure and the detection of concrete strength。
(1) concrete intensity testing
Reaction or ultrasound。
Concrete intensity is measured by means of a return-to-bull device for concrete surface values, an ultrasound instrument for sound speed within concrete, and by extrapolating concrete strength based on the correlation between concrete strength (r) and the return value and the rate of ultrasound transmission in concrete (v). The impact of carbonation depth is taken into account when using a echo. Concrete intensity is an important indicator of bridge structure。
(2) steel erosion detection
Tests include rusting of steel; concrete chlorine ion content; concrete electrical resistance; and concrete carbonation depth。
Steel corrosive detection is an integrated assessment of the state of steel corrosiveness in the bridge structure by testing the environmental conditions of the bars (e. G., chlorine ion content in concrete, concrete electrical resistance, carbonation depth, etc.) and their own natural electrical levels. It is also an important parameter for assessing the bridge structure。
(3) steel band distribution and concrete protection thickness detection
Structured materials are tested using various specialized instruments for steel bars and concrete materials of the bridge structure, field sampling, recording of detection data, assessment of the criteria for measuring the bridge structure material and the working state of the bridge structure material, together with a preliminary analysis of its causes。
Bridge load test (action static test)
Following the examination of the bridges for appearanceal diseases and the testing of structural materials, a bridge load test was conducted on the basis of the results of the tests on the bridges, which were severely damaged and had poor structural material condition. The purpose is to determine the actual carrying capacity of the bridge structure by directly loading the bridge by design load and by testing the actual response of the bridge to the adverse load to further analyse and understand the working state of the bridge。
The dynamic effects of the bridge and the conditions for its use in the vehicle load are determined by means of a drive-by test to determine the parameters of the structural power properties of the bridge and the forced vibration response as a function of the power load。
The static test is based on different types of bridge, different design loads, and different loads are designed on the basis of the principle of equivalence. By actually loading the bridge, the deformation and receptivity of the adverse cross-section of the bridge are detected, thus inducing the actual working state of the bridge structure and the use of load capacity。
The method of the bridge load test is the installation of various sensors on the main control transects of the bridge structure and the recording of the bridge receptivity and deformation data through the instrumentation of specified loads。
The implementation of the bridge load test has four phases: the programme design phase, the test preparation phase, the loading test phase and the analysis phase. It reads:
(1) design phase of the programme: through information analysis and on-site survey, a detailed test test programme for the bridge has been developed, specifying the purpose of the test and the specific test content to guide the inspection of the bridge。
(2) test preparation phase: installation of various sensors and instruments on site。
(3) load test phase: load test, collect data。
(4) analysis phase: data statistics, calculations and analysis, preparation of bridge inspection reports。
Iv. Conclusions and basis for the analysis of the data from the bridge inspection
The findings of the analysis of the bridge data include three aspects:
1. Findings of the evaluation of the condition of bridge structure materials
The current condition of the bridge structure material is analysed and clearly assessed based on the results of the testing of the bridge structure material. The focus is on concrete strength, steel erosion and the appearance of bridges。
Conclusions of the evaluation of the bridge capacity
The current carrying capacity of bridges is assessed, clearly concluded and classified through the testing and accounting of bridges。
3. Projections and recommendations for the working status of bridges
An analysis of the results of the monitoring of the status of the bridge provides a forecast of the future status of the bridge, identifies possible trends and provides recommendations for future bridge maintenance。
Data collection for bridge detection
Bridge detection data are both the result of and the basis for analysis of technical tests. The testing of the accuracy of the collected data has a direct impact on the quality of the inspection。
In order to ensure the reliability of data collection at the bridge, the following five aspects must be addressed:
1. Preparation of a programme for the inspection of bridges, the proper selection of holes and the detection of faults
2. Use of tested and qualified detection equipment
3. The correct use of bridge inspection equipment in accordance with operational protocols
4. Installation of sensors in strict compliance with operational protocols
5. During the testing process, the data are loaded and read according to procedure, with close attention to data changes。
The following issues should be noted in the implementation of bridge tests:
One. Testing sample
This includes test detection of the bridge hole, selection of test faults and sample detection. The test is to select a representative bridge across the bridge, such as a more severely damaged and structurally ill bridge. The payload test fault typically selects the bridge structure with the main force to control the faults, such as the mid-point, the feeder, and the 1/4-phase. When testing bridge structure materials, steel and concrete seepages should be selected to be heavier, representative and universal areas should be sampled, and sample quantities should be measured according to the sampling frequency of the individual detection projects。
Sensors
Bridge inspection data are collected by sensors installed in various parts of the bridge structure, so the quality of the sensor directly affects the evaluation of the bridge. Sensors are the first level of data collection, the location and quality of their installation directly affect the quality of the data from the bridge inspection, so the sensor is to be wired strictly in accordance with the location determined by the bridge inspection programme and operate strictly in accordance with operational protocols and requirements. When you paste the transformer, the flatting and pasting quality of the concrete floor, the insulation electrical resistance, etc., are critical, and steps such as grinding the floor, lashing the film, stickers, blockages, seals, etc., must be gradual and must not be reduced or reduced。
3. Instruments
The instrumentation used for test testing must be certified for use。
Signal line
All signal cables used in the tests must be wired and grouped according to cable resistance。
Load vehicles
The load vehicle for the test shall be given a separate weight for each axis, measuring the axle range; the required stop is in place; and the speed of the load test shall be accurate and stable。
6. Wiring
The placement of the bridge on board during the static test must be precise。
7. Data collection for the motion static test
Special attention must be paid to the extremes or anomalies that appear in the live-loading test of the bridge, and data on the recovery of the unmounted bridge structure cannot be ignored, as it reflects the elastic working state of the bridge structure and should therefore be guaranteed that the number and duration of stable readings adequately reflect the recovery of the structure. The collection of dynamic static test data must be “stabilized first”. In addition, in order to prevent data instability and drift during loading tests, preloading should be carried out and the data should be recorded after structural deformation has stabilized, followed by the next process to ensure the quality of data collection at the bridge check。
8. Environmental impacts
The test environmental impact factors, such as a load test that does not allow for large seismic sources around the test site, the passage of pedestrian vehicles on the bridge is not permitted and, if it is not possible to avoid it, detailed records are to be made and data processing is to be eliminated. The static test requires a smaller temperature change in the environment, so it is appropriate to do so at night. For key data, tests can be conducted using different equipment to measure at the same time, using different combinations of instruments for different structural models, with a desirable effect. In the course of a bridge scratch, three measurement methods can be used, one for a connection tube, the other for an electrometer and the other for a pv. By way of practical comparison, we feel that the electrostatic shift is highly accurate, but it is difficult to install; the connection tube is simple, easy and suitable for a bridge that is clean and high below the bridge and cannot be constructed at water depths; and the pv calibration can be used for the static-carving test, but the station setting will be limited。
