Method for automatically measuring absolute elevation of large-span steel truss girder cantilever erection

Abstract

The invention discloses a method for automatically measuring the absolute elevation of large-span steel truss girder cantilever erection. The method is simple to operate and convenient to implement. Firstly, the datum point static level gauge is installed on the side face of a bridge tower, after steel truss girder sections are hoisted and connected, the static level gauge is installed at the measuring point position of the top face of the steel truss girder, then unmanned automatic measurement of the absolute elevation of the steel truss girder under various working conditions can be completed through the static level gauge, and data guidance is provided for cantilever assembly of the steel truss girder. The number of the static level gauges can be gradually increased or decreased according to the number of steel truss girder sections, continuous multi-section synchronous measurement of the absolute elevation of large-span steel truss girder cantilever erection is achieved, the influence of measurement errors caused by asynchronism of conventional measurement is eliminated, a large amount of repeated measurement work is reduced, meanwhile, the safety risk caused by long-term edge operation of personnel is avoided, and the working efficiency is improved. The influence of the external environment on the elevation measurement precision is reduced, the absolute elevation measurement efficiency and precision of steel truss girder cantilever erection are greatly improved, and the construction progress is accelerated.

Description

Technical Field

[0001] The invention relates to the technical field of construction measurement of cantilevered steel truss girder erection for a large span bridge, and in particular to an automatic measurement method for the absolute elevation of a cantilevered steel truss girder erection for a large span bridge. Background Art

[0002] During the cantilever erection of long-span steel truss bridges, vibrations caused by the external environment, wind, and construction impacts on the cantilever ends of the steel trusses result in the measurement of the absolute elevation of the steel trusses being performed under constant shaking conditions, making it difficult to ensure accurate measurement. Furthermore, the influence of construction machinery on the steel beam surface and poor line of sight during measurement require multiple station changes, resulting in low measurement efficiency and slow speed, which hinders the progress of the steel truss erection. Furthermore, during the cantilever erection of the steel truss beams, the cantilever ends of the steel trusses are affected by loads such as bridge cranes, causing downward deflection. Failure to accurately measure the absolute elevation of the cantilever ends of the steel trusses in real time and compare and correct them with the completed bridge alignment will directly affect subsequent cable construction and the overall alignment of the steel trusses. Therefore, it is particularly important to quickly and accurately measure the absolute elevation of the cantilever ends of the steel trusses during the cantilever erection process. This is to facilitate the timely detection of changes in the cantilever end posture of the steel trusses, provide data support for subsequent construction conditions, and ensure that the overall alignment of the steel trusses meets design and specification requirements.

[0003] Currently, conventional measurement methods have difficulty finding a stable location for instrument station setup when measuring the absolute elevation of the cantilever end of a steel truss beam. Furthermore, visibility is poor, requiring repeated measurements and multiple station changes, resulting in heavy fieldwork and sometimes reduced measurement accuracy. During cantilever erection, conventional measurement methods are unable to complete the measurement of all measuring points at the same time. When the measuring surface is shaking, errors can occur in the measurement data. Furthermore, to avoid environmental influences, conventional measurements require observations at night when the temperature is stable, shortening the effective measurement window. Furthermore, measurement personnel are required to place a ruler at the edge of the steel truss beam end, increasing safety risks for personnel and preventing continuous automatic observation. Consequently, the progress of steel truss erection is constrained.

[0004] For example, patent CN105783864A discloses a static level installation elevation preset measurement device and measurement method, wherein the measurement device consists of a reference water tank, a connecting pipe, a pressure gauge and two switch valves, wherein one switch valve is installed at the bottom of the reference water tank, the switch valve is connected to one end of the connecting pipe, and the other end of the connecting pipe is connected to the pressure gauge after passing through another switch valve; first, a static level installation point is selected, the reference water tank is fixed above the installation point, at a distance of no more than 1m, the switch valve installed on the reference water tank is closed, and the reference water tank is filled with water to 95%; the connecting pipe is connected to the switch valve on the reference water tank, the switch valve is opened, and after the connecting pipe is filled with water, the switch valve at the other end of the connecting pipe is closed, and a pressure gauge is installed; it is installed on site and cannot be applied to the absolute elevation measurement of cantilever erection of large-span steel trusses. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides an automatic measurement method for the absolute elevation of a cantilevered installation of a large-span steel truss beam, so as to achieve the purpose of improving the efficiency and accuracy of the field measurement of the absolute elevation of a cantilevered installation of a large-span steel truss beam.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] The method for automatically measuring the absolute elevation of a cantilevered long-span steel truss beam comprises the following steps:

[0008] S1. Select the model of static level;

[0009] S2. Assembly of static level;

[0010] S3. Determination of the base height constant of the static level;

[0011] S4. Calibration of the static level liquid level reference;

[0012] S5. On-site installation:

[0013] Set a benchmark point on the side of the bridge tower or the top surface of the stable structure on the pier top, install the benchmark point static level on the benchmark top surface, and install the steel beam surface static level at the measuring point on the top surface of the steel truss. The static levels are connected through a pressure-conducting liquid pipe.

[0014] S6. Filling liquid: introducing liquid into the pressure liquid pipe;

[0015] S7, data collection;

[0016] S8, synchronous measurement of liquid level;

[0017] S9. Data processing:

[0018] After the on-site data is automatically collected, it will be sent to the cloud platform for storage in real time. Users can download and process the monitoring data as needed, and calculate the absolute elevation of the first steel truss measurement point and the absolute elevation of each measurement point under subsequent working conditions.

[0019] Further:

[0020] In step S1, based on the longitudinal slope of the steel truss bridge and the pre-camber set during the erection of the steel beam, the range of the static level is comprehensively considered, and a static level with a range of 250-350mm is selected while ensuring accuracy and convenience.

[0021] In step S2, the static level includes a sensor, a liquid storage barrel and an adjustment base. When the adjustment base is installed, the horizontal bubble of the static level is adjusted to the center by adjusting the screw nut on the base, so that the measuring rod in the static level remains vertical, thereby reducing the friction resistance between the float and the measuring rod, improving observation accuracy and shortening data delay time.

[0022] In the S3 step, the adjustment base of the static level is connected by bolts. The adjustment base of each static level is rotated through the threaded hole of the bolt, and there may be errors in the position. In order to accurately obtain the height of the adjustment base for subsequent absolute elevation calculation, a precision level is used to measure the height from the liquid surface of each static level to the bottom of the base as a constant. The height constant should be repeatedly measured at different positions to improve the accuracy of the constant, and the heights of the bases of different static levels in the same line should be adjusted to be consistent.

[0023] In the S4 step, in order to ensure the consistency of the starting reference of the liquid level of the static levels in the same line, before the static levels are used, the first static level is used as the reference, and the liquid level data of the remaining static levels and the first static level are collected and the relative height difference is calculated. The relative height difference of the bottom of the static level base is measured by an electronic level to check the matching of the accuracy between the static levels in the same line. In order to improve the accuracy, static levels with large discreteness of the calibration results shall not be included in the same line.

[0024] In the step S6, ethylene glycol antifreeze is used as the transmission medium, and the antifreeze is introduced into the pressure guiding liquid pipe through the reserved filling port; after the filling is completed, a dedicated person should carefully check whether the liquid in the pressure guiding liquid pipe is full to avoid bubbles in the pressure guiding liquid pipe.

[0025] In the step S7, one end of the cable is connected to the data acquisition box, and the other end is connected to the reserved cable of the static level sensor; the system is debugged and the static level data acquisition time is set to achieve 24-hour continuous synchronous data acquisition to eliminate the vibration influence error caused by the conventional measurement method's inability to synchronously measure all measurement points.

[0026] In the step S8, when used for the first time, a time period of nighttime when the temperature difference is small and relatively stable is selected, and a precision instrument is used to measure the relative height from the liquid surface of the static level to the measuring point on the steel beam surface, which is used to calculate the absolute elevation of each measuring point in the first phase. When additional measuring points are subsequently added for the first time, the relative height measurement with the base point should be synchronized to facilitate determination of the initial absolute elevation of the newly added measuring points.

[0027] In the step S9,

[0028] (1) Calculation of absolute elevation of each measuring point in the first phase:

[0029] H i初始 =H j+(jb i ) / 1000

[0030] Among them: H j is the absolute elevation of the reference point (m); j is the height from the current liquid level of the static level at the reference point to the top surface of the reference point (mm); b i The height from the current liquid level of the static level instrument to the top surface of each measuring point (mm);

[0031] (2) Subsequent calculation of absolute elevation of each measuring point under different working conditions:

[0032] Hi=H i初始 +(f j -f i ) / 1000

[0033] Among them: H i初始 is the initial absolute elevation value of each measuring point (m); f j is the current liquid level reading of the static level gauge at the reference point under the same working conditions (mm); f i It is the current liquid level reading (mm) of the static level instrument at each measuring point under the same working conditions.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] This method is simple to operate and easy to implement. Using this method, the benchmark static level is first installed on the side of the bridge tower. When the lifting of the steel truss segment is initially completed, the static level is installed at the measuring point on the top surface of the steel truss. Subsequently, the static level can be used to complete unmanned automatic measurement of the absolute elevation of the steel truss under various working conditions, providing data guidance for the cantilever assembly of the steel truss. There is no need for surveyors to carry a large number of heavy measuring instruments and accessories to climb to the steel truss bridge deck for manual measurement; and the number of static levels can be gradually increased or decreased according to the number of steel truss segments, realizing the cantilever assembly of large-span steel truss beams. The continuous multi-section synchronous automatic measurement of the absolute elevation of the boom eliminates the measurement error caused by the asynchrony of manual measurement under shaking working conditions, reduces a large amount of repeated measurement work, saves at least 2 surveyors and 1 high-precision total station, and avoids the safety risks of surveyors working near the edge for a long time, reduces the impact of the external environment on the accuracy of elevation measurement, and realizes 24-hour unmanned automatic continuous measurement, which greatly improves the efficiency and accuracy of the field measurement of the absolute elevation of the large-span steel truss cantilever erection, and accelerates the construction progress of the large-span steel truss cantilever erection. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The following is a brief description of the contents and symbols in the drawings of this specification:

[0037] Figure 1 Schematic diagram of the powerful magnet of the present invention.

[0038] Figure 2 Schematic diagram of the static level of the present invention.

[0039] Figure 3 Schematic diagram of the static level base height constant determination of the present invention.

[0040] Figure 4 This is a schematic diagram of the calibration of the liquid level of the static level instrument of the present invention.

[0041] Figure 5 This is a schematic diagram of on-site installation of the present invention.

[0042] Figure 6 Schematic diagram of synchronous measurement of liquid level height according to the present invention.

[0043] Figure 7 This is a schematic diagram of data annotation in the present invention. DETAILED DESCRIPTION

[0044] Conventional absolute elevation measurement for large-span steel truss girder erection requires the instrument to be set up in a stable position. During each measurement condition, the top surface of the steel truss is in a swaying state, making it difficult to find a stable position for instrument setup using conventional measurement methods. Furthermore, due to the large number of construction machinery and temporary components on the girder surface, visibility conditions are poor, and multiple station transfers are required to complete the elevation measurement task, resulting in a large field workload. Conventional measurement also prevents the elevation measurement of all measuring points from being completed at the same time. Due to the influence of the steel truss sway, the obtained elevation data has large errors, and the accuracy of the steel truss elevation measurement in a swaying state is unpredictable. During the entire steel truss cantilever erection period, there are multiple measurement conditions, resulting in low manual measurement efficiency and slow feedback. To mitigate the impact of the environment on measurement accuracy, conventional measurement methods require elevation measurements to be performed at night when the temperature and wind speed are stable. This results in a short effective measurement window, making continuous and rapid observation impossible with conventional methods, which constrains the progress of the steel truss erection project. Furthermore, surveyors need to set up a ruler at the edge of the steel girder at the cantilever end of the steel truss, increasing the safety risk to personnel.

[0045] The present invention proposes an automatic measurement method for the absolute elevation of the cantilever erection of a large-span steel truss girder. The method is simple to operate and easy to implement. Using this method, a reference point static level is first installed on the side of the bridge tower. When the steel truss girder segment is hoisted and connected, the static level is installed at the measuring point position on the top surface of the steel truss girder. Subsequently, the static level can be used to complete unmanned automatic measurement of the absolute elevation of the steel truss girder under various working conditions, providing data guidance for the assembly of the steel truss girder cantilever. The number of static levels can be gradually increased or decreased according to the number of steel truss girder segments, thereby realizing continuous multi-section synchronous measurement of the absolute elevation of the cantilever erection of a large-span steel truss girder, eliminating the measurement error caused by the asynchrony of conventional measurement, reducing a large amount of repeated measurement work, saving at least 2 surveyors, and avoiding the safety risks of personnel working near the edge for a long time, reducing the influence of the external environment on the elevation measurement accuracy, realizing 24-hour unmanned automatic continuous elevation measurement, greatly improving the efficiency and accuracy of the absolute elevation measurement of the cantilever erection of the steel truss girder, and accelerating the construction progress of the cantilever erection of the steel truss girder.

[0046] The specific implementation of the present invention will be further explained in detail below through description of embodiments with reference to the accompanying drawings.

[0047] 1. As Figures 1 to 7 As shown, the related devices used in this method include a strong magnet, a static level, a pressure-conducting liquid pipe, a transmission medium, a cable, and a data acquisition box.

[0048] 1. If Figure 1 As shown, a strong magnet;

[0049] It is a circular NdFeB magnet. To ensure suction and stability, the diameter is not less than 80mm, a circular hole is set in the middle, and it is equipped with connecting bolts and nuts.

[0050] 2. If Figure 2 As shown, a static level;

[0051] It is a magnetostrictive static level, including a static level adjustment base, a liquid storage barrel, a sensor, a float, a measuring rod, a vent pipe, a reserved cable, and a three-way joint; the connection operation is simple.

[0052] 3. Transmission medium;

[0053] Depending on the seasonal temperature of the project location, purified water or antifreeze can be selected as the transmission medium. When choosing purified water as the transmission medium, the extreme weather conditions in the location in recent years should be taken into consideration to avoid temperatures below zero, which would cause the purified water to freeze and render the static level inoperable. When choosing antifreeze as the transmission medium, the antifreeze must be from the same manufacturer, with the same ratio, and produced from the same batch. Mixing antifreeze from different manufacturers is strictly prohibited, as this will lead to inconsistent transmission medium specific gravity and uneven liquid levels.

[0054] 4. Pressure liquid pipe;

[0055] Use a nylon tube with a specific hardness and transparent material, with a diameter of inner diameter The diameter of the pressure liquid pipe should be compatible with the tee joint of the static level.

[0056] 5. Cables;

[0057] Use a four-core shielded cable, one end of which is connected to the cable connector reserved for the static level, and the other end is connected to the interface of the data acquisition box.

[0058] 6. Data collection box;

[0059] It includes a main controller, a wireless data transmission module (GPRS module), a sensor acquisition module, a chassis, etc.

[0060] The method for automatically measuring the absolute elevation of a cantilevered long-span steel truss beam according to the present invention comprises the following steps:

[0061] The first step is to choose the model of static level.

[0062] Based on the longitudinal slope of the steel truss bridge and the pre-camber set during the erection of the steel beam, and taking into comprehensive consideration the range of the static level, while ensuring accuracy and convenience, a static level with a range of 300mm is generally selected.

[0063] The second step is to assemble the static level.

[0064] The static level includes a sensor, a liquid storage barrel and an adjustment base. When installing the adjustment base, the horizontal bubble of the static level is adjusted to the center by adjusting the screw nut on the base, so that the measuring rod in the static level remains vertical, thereby reducing the friction resistance between the float and the measuring rod, improving observation accuracy and shortening data delay time.

[0065] The third step, such as Figure 3 As shown in the figure, the height constant of the base of the static level is determined.

[0066] The adjustment base of the static level is connected by bolts. The adjustment base of each static level is rotated through the bolt thread, and there may be errors in the position. In order to accurately obtain the height of the adjustment base for subsequent absolute elevation calculation, a precision level is used to measure the height from the liquid surface to the bottom of the base of each static level as a constant. The height constant should be repeatedly measured at different positions to improve the accuracy of the constant, and the heights of the bases of different static levels in the same line should be adjusted to be consistent.

[0067] c1=(a2-a1)-f1

[0068] Where: c1 is the height of the base of the static level (mm); a1 and a2 are the level rod readings (mm); f1 is the current liquid level reading of the static level (mm).

[0069] The fourth step is as follows Figure 4 As shown, the static level instrument liquid level is calibrated based on the reference.

[0070] To ensure the consistency of the starting reference of the liquid level of the static levels in the same line, before the static levels are used, the first static level is used as the reference to collect and calculate the relative height difference between the liquid level data of the remaining static levels and the first static level. The relative height difference of the bottom of the static level base is measured by a precision electronic level to check the accuracy matching between the static levels in the same line. To improve accuracy, static levels with large discreteness in calibration results shall not be included in the same line.

[0071] △=(a1-a2)-(f1-f2)

[0072] Where: a1 and a2 are the level rod readings (mm); f1 and f2 are the current liquid level readings of the hydrostatic level (mm).

[0073] Step 5: Figure 5 As shown, on-site installation.

[0074] A reference point is set on the side of the bridge tower or the top surface of the stable structure on the pier top, and the static level of the reference point is installed on the reference top surface of the reference point. The strong magnet of the static level on the steel beam surface is adsorbed on the measuring point position on the top surface of the steel truss beam, and the static levels are connected through a pressure-conducting liquid pipe.

[0075] Step 6: Pour in liquid.

[0076] To prevent the transmission medium from freezing during low winter construction temperatures, which could cause the static level to malfunction, ethylene glycol antifreeze can be used as the transmission medium. Introduce the antifreeze into the pressure-conducting fluid pipe through the reserved filling port. After filling, a dedicated person should carefully check that the pressure-conducting fluid pipe is full of liquid. Air bubbles in the pipe can distort the static level monitoring data.

[0077] Step 7: Data collection.

[0078] Connect one end of the cable to the data acquisition box and the other end to the reserved cable for the static level sensor. Debug the system and set the static level data acquisition time to achieve 24-hour continuous synchronous data acquisition to eliminate the vibration error caused by conventional measurement methods that cannot synchronize measurement of all measurement points.

[0079] Step 8: Figure 6 As shown, the liquid level is measured synchronously.

[0080] When using it for the first time, choose a time period at night when the temperature difference is small and relatively stable, and use precision instruments to measure the relative height from the liquid surface of the static level to the measuring point on the steel beam surface (the height from the liquid surface of the benchmark static level to the benchmark point) to calculate the absolute elevation of each measuring point in the first phase. When adding measuring points for the first time, the relative height should be measured synchronously with the base point to determine the initial absolute elevation of the newly added measuring points.

[0081] Step 9: data processing.

[0082] After the on-site data is automatically collected, it will be sent to the cloud platform for storage in real time. Users can download and process the monitoring data as needed, and calculate the absolute elevation of the first steel truss measurement point and the absolute elevation of each measurement point under subsequent working conditions.

[0083] (1) Calculation of absolute elevation of each measuring point in the first phase:

[0084] H i初始 =H j +(jb i ) / 1000

[0085] Among them: H j is the absolute elevation of the reference point (m); j is the height from the current liquid level of the static level at the reference point to the top surface of the reference point (mm); b i The height from the current liquid level of the static level instrument to the top surface of each measuring point (mm);

[0086] (2) Subsequent calculation of absolute elevation of each measuring point under different working conditions:

[0087] Hi=H i初始 +(f j -f i ) / 1000

[0088] Among them: H i初始 is the initial absolute elevation value of each measuring point (m); f j is the current liquid level reading of the static level gauge at the reference point under the same working conditions (mm); f i It is the current liquid level reading (mm) of the static level instrument at each measuring point under the same working conditions.

[0089] Using this method, the benchmark static level is first installed on the side of the bridge tower. When the lifting of the steel truss segment is initially completed, the static level is installed at the measuring point on the top surface of the steel truss. Subsequently, the static level can be used to complete unmanned automatic measurement of the absolute elevation of the steel truss under various working conditions, providing data guidance for the cantilever assembly of the steel truss. There is no need for surveyors to carry a large number of heavy measuring instruments and accessories to climb to the steel truss bridge deck for manual measurement.

[0090] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A method for automatically measuring the absolute elevation of a large-span steel truss cantilever erection, characterized by: The following steps are involved: S1. Select the model of static level; S2. Assembly of static level; S3. Determination of the base height constant of the static level; S4. Calibration of the static level liquid level reference; S5. On-site installation: Set a benchmark point on the side of the bridge tower or the top surface of the stable structure on the pier top, install the benchmark point static level on the benchmark top surface, and install the steel beam surface static level at the measuring point on the top surface of the steel truss. The static levels are connected through a pressure-conducting liquid pipe. S6. Filling liquid: introducing liquid into the pressure liquid pipe; S7, data collection; S8, synchronous measurement of liquid level; S9. Data processing: After the on-site data is automatically collected, it will be sent to the cloud platform for storage in real time. Users can download and process the monitoring data as needed, and calculate the absolute elevation of the first steel truss measurement point and the absolute elevation of each measurement point under subsequent working conditions.

2. The method for automatically measuring the absolute height of a cantilevered long-span steel truss as claimed in claim 1, characterized in that: In step S1, based on the longitudinal slope of the steel truss bridge and the pre-camber set during the erection of the steel beam, the range of the static level is comprehensively considered, and a static level with a range of 250-350mm is selected while ensuring accuracy and convenience.

3. The method for automatically measuring the absolute height of a cantilevered long-span steel truss as claimed in claim 1, characterized in that: In step S2, the static level includes a sensor, a liquid storage barrel and an adjustment base. When the adjustment base is installed, the horizontal bubble of the static level is adjusted to the center by adjusting the screw nut on the base, so that the measuring rod in the static level remains vertical, thereby reducing the friction resistance between the float and the measuring rod, improving observation accuracy and shortening data delay time.

4. The method for automatically measuring the absolute height of a cantilevered long-span steel truss as claimed in claim 3, characterized in that: In the S3 step, the adjustment base of the static level is connected by bolts. The adjustment base of each static level is rotated through the threaded hole of the bolt, and there may be errors in the position. In order to accurately obtain the height of the adjustment base for subsequent absolute elevation calculation, a precision level is used to measure the height from the liquid surface of each static level to the bottom of the base as a constant. The height constant should be repeatedly measured at different positions to improve the accuracy of the constant, and the heights of the bases of different static levels in the same line should be adjusted to be consistent.

5. The method for automatically measuring the absolute height of a cantilevered long-span steel truss as claimed in claim 4, characterized in that: In the S4 step, in order to ensure the consistency of the starting reference of the liquid level of the static levels in the same line, before the static levels are used, the first static level is used as the reference, and the liquid level data of the remaining static levels and the first static level are collected and the relative height difference is calculated. The relative height difference of the bottom of the static level base is measured by an electronic level to check the matching of the accuracy between the static levels in the same line. In order to improve the accuracy, static levels with large discreteness of the calibration results shall not be included in the same line.

6. The method for automatically measuring the absolute height of a cantilevered long-span steel truss as claimed in claim 1, characterized in that: In the step S6, ethylene glycol antifreeze is used as the transmission medium, and the antifreeze is introduced into the pressure guiding liquid pipe through the reserved filling port; after the filling is completed, a dedicated person should carefully check whether the liquid in the pressure guiding liquid pipe is full to avoid bubbles in the pressure guiding liquid pipe.

7. The method for automatically measuring the absolute height of a cantilevered long-span steel truss as claimed in claim 1, characterized in that: In the step S7, one end of the cable is connected to the data acquisition box, and the other end is connected to the reserved cable of the static level sensor; the system is debugged and the static level data acquisition time is set to achieve 24-hour continuous synchronous data acquisition to eliminate the vibration influence error caused by the conventional measurement method's inability to synchronously measure all measurement points.

8. The method for automatically measuring the absolute height of a cantilevered long-span steel truss as claimed in claim 1, characterized in that: In the step S8, when used for the first time, a time period of nighttime when the temperature difference is small and relatively stable is selected, and a precision instrument is used to measure the relative height from the liquid surface of the static level to the measuring point on the steel beam surface, which is used to calculate the absolute elevation of each measuring point in the first phase. When additional measuring points are subsequently added for the first time, the relative height measurement with the base point should be synchronized to facilitate determination of the initial absolute elevation of the newly added measuring points.

9. The method for automatically measuring the absolute height of a cantilevered long-span steel truss as claimed in claim 1, characterized in that: In the step S9, (1) Calculation of absolute elevation of each measuring point in the first phase: H i初始 =H j +(j-b i ) / 1000 Among them: H j is the absolute elevation of the reference point (m); j is the height from the current liquid level of the static level at the reference point to the top surface of the reference point (mm); b i The height from the current liquid level of the static level instrument to the top surface of each measuring point (mm); (2) Subsequent calculation of absolute elevation of each measuring point under different working conditions: Hi=H i初始 +(f j -f i ) / 1000 Among them: H i初始 is the initial absolute elevation value of each measuring point (m); f j is the current liquid level reading of the static level gauge at the reference point under the same working conditions (mm); f i It is the current liquid level reading (mm) of the static level instrument at each measuring point under the same working conditions.

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