A monitoring organization
Monitoring work is an important part of the supervision work, monitoring units under the supervision unit management. Monitoring involves design, construction, supervision and other units of work. The division of labor of each unit is as follows:
1. Command
Lead the monitoring and surveillance group of the project variable cross-section continuous girder bridge, coordinate the work of the member units, and convene the monitoring meeting in time.
2, the design unit
(1) to provide structural calculation data files, drawings, the final state of the internal force of the structure and the line, and with the monitoring unit *** with the signing of the monitoring of the theoretical line, into the bridge state of the main girder and the main pier to control the cross-section of the internal force and stress, the main beam of the cumulative deflection of the construction process to take into account the main pier deviation.
(2) Countersign the control instruction sheet issued by the control team.
(3) Discussing and deciding on major design modifications, and responsible for all kinds of calculations after changing the design.
3, the construction unit
(1) is responsible for the construction organization design and schedule, if there is a change in the original construction unit case should be put forward as early as possible.
(2) independent measurement and sampling, hanging basket deflection calculation and test.
(3) is responsible for concrete modulus of elasticity test.
(4) Responsible for bridge deck construction load investigation and control.
(5) Responsible for on-site protection of test elements and providing facilities for monitoring units for on-site testing.
(6) Responsible for the displacement test of main girders, main piers and all structures, and the test results will be remitted to the monitoring working group in time after the completion of each girder section.
4. Supervision unit
(1) summarize and verify the monitoring results of all parties in time, organize the working meeting of each section, and issue the monitoring instructions proposed by the monitoring unit.
(2) Monitor the measurement of main girder elevation and pier top deviation and abutment verticality.
(3) Provide measurement results of main girder section dimensions.
(4) Summarize the relevant monitoring results to the monitoring working group in time after the completion of each girder section.
5. Monitoring unit
(1) Prepare monitoring program.
(2) independently carry out the construction process of structural stress, strain and temperature, as well as the main girder elevation, the top of the pier off-set, the verticality of the abutment observation.
(3) Identify design parameter errors and make effective predictions.
(4) Optimization and adjustment analysis.
(5) Forecast the next stage of hanging basket elevation.
(6) Report to the leading group on major modifications in time and propose adjustment programs together with the design unit.
(7) Hand over the position and interface of monitoring elements within three months after the completion of the main bridge, and submit monitoring and surveillance documents and result reports.
Two, monitoring work procedures
1, the monitoring unit issued by the monitoring instruction form, reported to the senior resident supervising engineer to confirm the issuance to the construction unit for specific implementation;
2, 1/8L, 1/4L, 3/8L around the block, the merging section of the section of the monitoring instruction form, the design unit should be reviewed and signed by the design unit, and the other sections of the monitoring instruction form by the design unit for the record. For the record, the design unit should verbally notify the monitoring unit within 24 hours if there is any objection, and put forward written comments within 48 hours;
3. After the completion of a stage of construction, the supervisor will summarize the relevant data of all parties to the monitoring work group for a brief summary, and then enter the next stage of the construction work program.
Three, monitoring principles
Monitoring is to effectively control the bridge target, correct the various parameters affecting the bridge target in the construction process, to ensure that the bridge after the structural stress and line meet the design requirements.
1, force requirements. Reflecting the variable cross-section continuous bridge stress factors are mainly the main beam cross-section of the internal force (or stress) condition. Usually play a controlling role is the main beam of the upper and lower edge of the positive stress. Whether in the state of bridge formation or in the state of construction, to ensure that the maximum value of each cross-section stress is within the permissible range.
2, linear requirements. Line shape is mainly the elevation of the main beam. After the bridge (usually after long-term deformation stabilization) the elevation of the main beam to meet the requirements of the design elevation.
3, control means. Monitoring to use predictive control method. For the adjustment of the internal force (or stress) of the main girder, it is realized by strictly controlling the tension of the prestressing beam. For the adjustment of main girder line shape, realized by adjusting the elevation of standing mold. The change of main girder elevation caused by parameter error and other factors is corrected by adjusting the elevation of vertical mold.
Fourth, monitoring methods
In order to eliminate the inconsistency between design and actual construction caused by the inaccuracy of the value of the design parameter, the parameter should be identified and predicted in the construction process. For major design parameter errors, the design unit is brought to the theoretical design value modification, and for conventional parameter errors, adjustment is made through optimization.
1, design parameter identification
Through the comparison of measured and theoretical values of state variables (displacement and stress-strain) under typical construction conditions, as well as the analysis of the impact of design parameters, the amount of design parameter error is identified.
2. Prediction of design parameters
According to the error amount of design parameters of the constructed girder section, a suitable prediction method (gray model is recommended) is used to predict the possible error amount of design parameters of the future girder section.
3. Optimization adjustment
Monitoring is mainly based on controlling the main girder elevation and section bending moment, and the optimization adjustment also establishes the control objective function (and constraints) with these factors. Through the design parameter error on the bridge deformation and force analysis. Apply the optimization method, adjust the elevation of this girder section and the future girder section, make the bridge state as close as possible to the ideal design of the bridge state, and to ensure the safety of the force during the construction process.
V. Main contents of monitoring work
1. Construction simulation calculation
Adopting mature monitoring software, the bridge will be monitored and simulated to review the bridge formation state and construction state determined by the design calculation, i.e., real-time simulation of the construction process and formation of the corresponding construction simulation analysis and calculation files.
In accordance with the construction and design of the construction process, as well as the design of the basic parameters provided by the construction process for the installation of the calculations, the construction state and the bridge state of the structural stress and deformation of the control data. Mainly:
(1) the theoretical data of state variables under each construction state and bridge state: main girder elevation, pier top deviation and verticality of abutment as well as control section stress and strain.
(2) Theoretical values of monitoring data: elevation of main girder segments.
These data and design, design supervision and mutual proofreading to confirm that there is no error, and signed by both sides, as a variable cross-section continuous bridge monitoring the theoretical trajectory.
2, monitoring the collection of basic information test data
(1) the age of concrete for 3, 7, 14, 28, 90 days of the modulus of elasticity test as well as the strength of the specified requirements of the experiment; reinforced concrete weight; cantilever poured section of concrete square meters and the actual cross-section size.
(2) Climatic information: sunshine and rain, air temperature, wind direction and wind speed.
(3) Actual construction period and future schedule.
(4) Hanging basket pivot reaction force and other construction loads on the bridge layout location and value.
3, the construction process of structural displacement, stress, strain and temperature observation
1) construction of a girder section is called a stage, in order to improve the construction process of the hanging basket and the main concrete girder force, each stage is divided into four working conditions:
1) the hanging basket forward and positioning mold;
② half of the main girder concrete casting;
3 pouring all the concrete;
④Prestressing tensioning.
(2) The main tests are as follows:
① Main girder deflection observation
A Measuring point arrangement: three elevation observation points shall be set up at the top of each girder section with cantilevered end cross-section, which shall be used as the coordinate observation points at the same time. Measuring point shall be set up with short steel bar embedded and numbered with red paint. At the same time, three temporary elevation observation points are set up for the cantilever end section of the current cast-in-place beam section, which are used as the elevation of the bottom of the beam section, and the elevation relationship of the corresponding measurement points is given.
The upstream and downstream observation points are used as long-term monitoring observation points, while attention should be paid to the setting and protection of the shore reference point.
B test method: use precision level to measure the elevation of the measuring point. According to the theoretical calculation, it is determined that the frequency of retesting is once for 3 beam sections.
② pier top horizontal displacement and pier verticality measurement
A measurement point layout: the main pier top, bottom upstream and downstream of each set one to two measurement points, measurement point location in the pier top, bottom of the pier to facilitate the observation of the reliable position. Pier top and bottom observation points should be measured relative coordinates.
B test method: using total station measurement.
3 bridge pier settlement measurement
A measurement point layout: the main pier bearing platform downstream of each set one to two measurement points, measurement point location in the bearing platform to facilitate the observation of the reliable position.
B test method: use precision level to measure the elevation of the measuring point.
④Section steel stress or concrete strain observation
A test method
Strain gage using high-quality vibrating string strain gage, vibrating string strain gage using the corresponding special instrumentation testing. All test components have reliable calibration data.
B test point arrangement
The strain test points are arranged near the root of the main girder and the mid-span section in the left and right widths, and the test points are arranged appropriately in the side spans, sub-side spans and the L/4 section of the main span, taking into consideration of the symmetry of the structure and synchronization of the left and right widths of the construction; the test of the principal stress of the web plate near the counterbend point should be determined in consultation with the designer; the main girder has no fewer than 6 test points in each cross-section;
The test section at the top and the bottom of each pier are arranged one for the test section, and one test section for the top and bottom of the pier. Arrangement of a test section, for the high pier appropriate increase in test section; pier column each section of not less than 4 test points;
As the actual construction of the structure by the weight, basket stiffness, construction loads and other complex factors, it may be necessary to the actual condition of the structure, the appropriate adjustment of some sections.
⑤ Temperature field observation
A test method
The concrete should be pre-built in the fully automatic temperature data acquisition system collection. Temperature elements are pre-embedded in the standard section of the main beam to measure the temperature field distribution inside it.
B Measurement point arrangement
Main girder: choose two standard sections, each with 15 measurement points; abutment set up upper and lower 2 sections, the position can be adjusted appropriately;
C Test time
Choose representative weather during the construction period of the main girder to conduct 24 hours of continuous observation, e.g., choose a sunny, cloudy, and cloudy rainy day in each season.
6 Measurement of temperature effects on structural deformation and force
Test content: main girder elevation, pier top deflection and abutment perpendicularity as well as the related cross-section stress-strain.
Test time: synchronized with the temperature field observation.
4, design parameter error analysis and identification
(1) the influence of hanging basket stiffness on elevation;
(2) the influence of girder section self-weight error on the structure;
(3) the influence of girder and pier stiffness error on the structure;
(4) the influence of concrete shrinkage and creep on the structure;
(5) the influence of construction load variation on the structure;
(6) The effect of temperature;
(7) The effect of prestressing error.
5. Prediction of design parameter errors for future girder sections
6. Forecasting of the elevation of the main girder for the next stage of mold erection
7. Major design modifications
If there are large construction errors, the following major modifications may be required: major modifications to the design parameters; and major adjustments to the case of the merging construction unit.
Sixth, monitoring the implementation of procedures
1, monitoring the operating rules
1 main pier construction stage
According to the construction process, this stage of the main pier of the stress measurements, mainly based on the main observation, to master the state of the stress and its changes, and at the same time, to understand the main pier in the process of construction of the settlement and dislocation of the main pier, in order to prepare for the subsequent construction of the main girder to monitor.
The main content of the work is the stress observation of the buried section of strain gauge.
(2)Construction stage of 0# block of main girder
Because of the construction process of cast-in-place with bracket, the main content of monitoring is the elevation of the main girder before and after the fall of the bracket and the control of stress-strain changes in the cross-section.
(3) Main girder cantilever construction stage
The structural deformation of the main girder and the stress (strain) of the control section are mainly monitored during the construction of the main girder, of which the main test content of the structural deformation of the main girder includes: measurement of the elevation of the concrete formwork, measurement of the main girder displacement during the process of concrete pouring, and measurement of the geometric state after the completion of the construction of the section. The main test content of the main girder stress (strain) includes the stress (strain) of the main girder edge and the control section of the main span. The observation time is generally set from 0:00 a.m. to 5:00 a.m., and the measurement time is determined by the supervisor according to the weather condition of the day. The main girder is cantilever casting, each girder section as a stage, and each stage is divided into four working conditions.
①Positioning of Hanging Basket Standing Mould
The construction unit positioned the hanging basket according to the elevation of the standing mould in the monitoring instruction table, and then notified the supervisory and monitoring units to test its elevation value. The test content of this condition:
A main girder elevation: completed girder section (including measurement points on the hanging basket);
Requirements:
a, it must be ensured that the empty hanging basket is in the state of cantilever support, and there can be no reinforcement bars or construction loads on the hanging basket.
b, The time of testing should avoid the effects of localized temperature differences (at the time of day when the temperature field is most uniform within the structure).
c, elevation error of standing mold is required to be less than ±5mm.
B Pouring 1/2 concrete
The test content of this condition:
Elevation of main girder: this girder section;
Requirement: control the quantity of 1/2 concrete.
(This condition measurement is mainly to grasp the main girder in the process of pouring whether there is any abnormal situation occurs, do not do precision requirements, according to the actual construction conditions, can be slightly removed)
C poured concrete
This condition test content:
a main girder elevation;
b pier top off-set and abutment verticality.
Requirements:
a, avoiding temperature influence;
b, controlling the elevation error at ±3cm.
D, main girder pre-stressing tensioning is completed
The test content of this condition:
a main girder elevation: completed girder section;
b pier top deviation and abutment perpendicularity;
c controlling section Stress strain.
Requirements:
a. Avoid the influence of temperature;
b. Elevation error is controlled at ±3cm.
4. Construction stage of the closing section
Construction of the closing section is the key stage of the whole bridge, which needs to be strictly monitored and the main content is the elevation of the main girder and control of the change of the section stress and strain. Therefore, it is divided into the following three conditions:
Condition ⅠInstallation of the balancing weight of the closing section
Condition ⅡPouring of the concrete of the closing section and tensioning of the prestressing bundles of the closing section
Condition ⅢRemoval of the balancing weight
Specific operation details are as follows:
(1)Installation of the closing hangers and balancing weight
The weights of the hanging baskets, the position of the hanging basket during the closing are important for the main girder construction, which will affect the elevation and control of stress-strain changes of the section. When the position of the hanging basket on the main beam elevation and control section of the stress has a great impact on the final closing construction unit case construction unit must be with the monitoring unit **** with the decision.
This condition test content:
Elevation of vertical mold: double-check the accuracy of the elevation of vertical mold; the elevation of the beams at both ends of the section.
Requirements:
The error of elevation of vertical mold should be less than ±5mm;
Take care to avoid the influence of local temperature difference during the test.
(2) Pouring of concrete for merging
The test content of this condition:
Elevation of 3 beams at each end of merging section;
Requirements:
a. Elevation of the bottom mold on the hanging basket should be controlled within ±3cm;
b. Elevation control is the main concern;
Take care of the effect of the difference in temperature of the sunshine and pay attention to the temperature effect during testing. of the correction.
(3) after the removal of the hanger
The condition test content:
①Elevation of three beams at each end of the merging section;
②Temperature measurement.
Requirements:
a, hanging basket on the bottom mold elevation error control within ± 3cm;
b, control the amount of 1/2 concrete;
c, pay attention to avoiding the effect of sunlight temperature difference and pay attention to the correction of temperature effects.
5, the second phase of constant load construction stage
This stage of the main bridge construction has been basically completed, the main work is to monitor the changes in the structure and the theoretical calculations whether it is consistent with the following three conditions:
① Removal of brackets, hanging baskets;
② bridge deck pavement, guardrail, lighting and other loads.
Working conditions ① and ② are mainly tested as follows:
a, the elevation of the main girder at the quarter point;
b, the control of sectional stress;
c, the pier top deviation and abutment verticality test;
d, the observation of abutment settlement
③Working conditions are completed after the completion of the main bridge, and the bridge is comprehensively re-tested, and the re-testing is also as the Monitoring unit of the completion of acceptance. The test contents are:
a, the elevation of the main girder's eight points;
b, the control section stress;
c, the pier top deviation and abutment verticality test;
d, the observation of abutment settlement
6, the stage of monitoring and acceptance
Prestressing tensioning is completed before the moving of hanging baskets, which is the end of the construction of a stage of a variable cross-section continuous bridge Mark. After the completion of a girder section, the controlling party will gather all the observation data, and the monitoring working group will issue the next girder section monitoring instruction sheet, and make a brief comment on the control situation of the previous girder section. The instruction sheet is signed by the senior resident supervising engineer and then proceeds to the construction of the next girder section.
Variable cross-section continuous bridge construction about 5 girder section after a monitoring summary, the design parameters for a systematic adjustment.
Seven, monitoring the accuracy, principles and overall requirements
1, control accuracy and principles
1 control instructions and allowable error
①Mold erection and prestressing tensioning must be completed in a relatively stable and uniform temperature field during the day (generally before sunrise);
②Allowable error in elevation of the mold erection: (+/-) 5 mm;
③Prestressing tensioning should be done in a relatively stable and uniform temperature field during the day. p>
3) Control range of prestressing extension: (-5%, +10%)
(2) Local linear control requirements
Relative elevation error of adjacent segments not more than 0.3% (additional longitudinal slope)
(3) Control error of poured girder segments as well as the main girder system after the bridge is completed
Elevation error: (+/-) L/5000, where L is the span diameter.
(4) The weight control requirement of main girder
The error of cross sectional dimension of main girder is strictly controlled according to the requirement of construction regulations.
(5) Control accuracy of main pier
Allowable construction errors: axial deviation (+/-)10mm, section size (+/-)20mm, inclination H/3000, allowable deviation of elevation at the top of pier (+/-)10mm.
(6)
Other
①Axis of main girder: Allowable deviation of main girder center line in horizontal direction (+/-)10mm, allowable deviation of elevation (+/-) 10mm, and allowable deviation of elevation (+/-)10mm. Elevation allowable deviation (+/-) 10mm;
② bridge deck flatness: allowable deviation (+/-) 8mm (two-meter ruler test).
3 beam section shall not appear cracks.
2, the implementation of the general requirements
1) strict control of construction temporary load. The bridge crane must be driven to the position of 0# girder section during the test, and the stacking of materials is required to be fixed and quantitative.
(2) Measurement is carried out in parallel by the construction unit and the monitoring unit so as to facilitate timely proofreading at the site, while monitoring is carried out by the supervisory party.
(3) All observation records shall indicate the working condition (construction status), date, time, weather, air temperature, special construction loads on the bridge deck and other sudden change factors.
(4) After the completion of each construction condition, the construction unit and the monitoring unit shall independently carry out tests at the same time, and the supervisory party shall make random checks according to the specified frequency to confirm that the measurement results are correct before proceeding to the construction of the next condition.
(5) The test work before and after the main girder hanging basket erection and prestressing tensioning must avoid the influence of sunshine temperature difference.
(6) After the end of prestressing tensioning and lowering of the hanging basket, the parties concerned summarize the data to the monitoring unit, which analyzes the data and then issues the control instruction sheet for the next girder section.
(7) In monitoring the theoretical trajectory in line with the design and monitoring **** with the confirmation of the monitoring, the design unit in 1/8L, 1/4L, 3/8L around the block, the merging section, should be in accordance with the actual construction parameters to review the monitoring unit to monitor the instructions provided by the instruction sheet, and signed; other beam section design unit for the record. Monitoring parameter measured value and theoretical value more than the upper limit of the difference, the design unit and monitoring unit should be calculated separately, and analyze the reasons, adjust the relevant design parameters, monitoring instruction sheet design unit and monitoring unit should be signed.
(8) The control instruction form shall be executed only after the senior resident supervising engineer has signed and recognized it, and only then the construction of the next girder section can be carried out.
(9) After the completion of each girder section, a comprehensive crack inspection shall be carried out on the completed girder section, and the construction shall be stopped when cracks are found, and reported to the monitoring and management team and the leading team.
(10) construction instruction form in 7 copies, respectively, by the command (2 copies), design, supervision (2 copies), construction, monitoring and preservation.
3, construction monitoring early warning system
In the actual construction, due to the influence of various factors, monitoring parameters measured value and the theoretical value of the difference will occur, through effective monitoring, this difference will not be very large, but taking into account the influence of certain non-deterministic factors, determine the upper limit of the difference, to ensure the bridge structural safety, control and monitoring of the smooth progress of the bridge is very necessary. The relevant monitoring parameters and their difference limits in each construction stage are shown in the following table.
During the construction process, the measured value of the monitoring parameters and the theoretical value of the deviation is greater than the upper limit in the table, the construction should be immediately suspended, the construction monitoring working group meeting should be held, all parties should actively cooperate with the monitoring unit, carefully analyze the situation, find out the reasons and determine the final solution.
Eight, monitoring and assurance system and measures
1, monitoring system assurance system
1) the monitoring unit should be the quality management objectives of the decomposition of the refinement, the implementation of the job responsibility system.
(2) Each monitoring unit should establish a perfect equipment, instruments and materials management system
(3) Each monitoring unit should establish a perfect document and information management system
(4) Each monitoring unit should establish a perfect monitoring management system
(5) Each monitoring unit should establish a perfect education and training system
2, monitoring technology assurance system
(1) Monitoring unit program approval and technical review system
①Monitoring technical documents are organized and prepared by the person in charge of technology. Monitoring calculations using powerful, reliable and accurate calculation results, the application of mature professional software. The preparation of technical documents to implement a strict review system.
② monitoring technical documents must be reported to the site 15 days before the start of the review. And reported to the project manager for approval.
③ monitoring technical documents must be approved by the supervision and other levels of approval and according to the approval of the views of the revision and improvement, and approved by the command before implementation.
(2) monitoring technology, quality delivery system
Technology, quality of the delivery system is a basic work of technical management, through the technical delivery, so that the technical work of the transfer of information to achieve a comprehensive and accurate. Submission must be in the form of a combination of written visa and language expression, can be divided into the following cases:
①Implementation of the construction monitoring unit case preparation is completed, and approval, led by the project leader, the person in charge of technology to organize all personnel to study the program carefully, and technical, quality, safety written submission, listing the monitoring parts and monitoring points. Technical personnel must do not clear briefing is not on duty, no visa is not on duty.
②In the construction process, all occurrences of technical programs, monitoring results, etc. in the grass-roots level to convey information, must be technical briefing.
(3) monitoring technology guarantee measures
①The deformation observation reference point set must be stable and reliable, and regularly check its stability, and strengthen the protection of monitoring facilities.
②All deformation observation should read the initial value. Stress and internal force measurement should be buried in the elements, immediately measured the initial value. Stress testing and deformation observations are synchronized.
3 monitoring should be carried out according to plan, step by step, in strict accordance with the construction monitoring unit case implementation, the use of instruments in the monitoring process should ensure its accuracy and reliability.
④Organization of experienced professional engineers and technicians to monitor the construction, good monitoring records and data preservation, and submitted to the supervisor for review. When it is found that the value of early warning monitoring is exceeded, report to the supervisor and take remedial measures in time.
⑤ For a large amount of measurement information, use the computer to introduce calculation and drawing software for on-site data processing and drawing, and timely use of measurement information feedback to guide the construction of the project. Ensure the whole process of safe construction.
6 construction monitoring specifically includes several major stages such as prediction, monitoring and feedback, the monitoring results of the use of inverse analysis and positive analysis method for prediction and evaluation, in order to predict the construction parameters, to carry out a comprehensive analysis of judgment, prediction of the safety of the structure, to guide the construction, feedback design.
(4) Monitoring technology management measures
①Organization of monitoring
Because of the importance and complexity of monitoring work, it is necessary to select enough technicians with rich monitoring experience and the ability to calculate and analyze the force to serve as the monitoring work, analyze and study the monitoring data; carry out a detailed division of labor within the monitoring team, so that each one of them is responsible for their own duties.
②Management of monitoring
In order to ensure the accuracy of the monitoring results and accelerate the feedback speed, all the monitoring data are managed by computer. According to the temporal curve regression results, the establishment of monitoring and measurement management level, and monitoring results in the form of daily reports in a timely manner, regularly submitted to the supervising engineer, the design unit to monitor the weekly (monthly) report, with the corresponding measurement point temporal curve graphs, the construction of the week (month) to evaluate the construction situation and put forward construction proposals.
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