Method and system for accurately positioning first beam section of segmental beam through short line matching method

Abstract

The invention provides a method and a system for accurately positioning a first beam section of a segmental beam by a short line matching method, which are used for optimizing a pier-side bracket opposite-pulling deformed steel bar tensioning construction process, enhancing the stability of a bracket and improving the mounting precision and the construction efficiency of the first beam section; before the first beam section is adjusted, the bracket is pre-pressed, and the influence of non-elastic deformation of the bracket on the positioning accuracy of the first beam section is eliminated; by controlling the axis deviation and flatness of the middle supporting legs, the influence of unbalance loading generated by the kiloton bridge girder erection machine on the line shape of the first beam section is avoided; the centering rod of the prism is regularly self-checked and corrected, so that measurement errors caused by inclination of the centering rod are eliminated; elevation control encryption adopts a zenith distance method, so that the precision is high, and linear control of segmental beam erection is facilitated; before a front auxiliary supporting leg of the bridge girder erection machine is in place and after a pier top block is hoisted, multi-measurement-back displacement monitoring is carried out on a pier body, and the accuracy of a line shape under the working condition is guaranteed. According to the method, the influence of each factor on the positioning precision of the first beam section is eliminated, so that the positioning precision of the first beam section is controlled within a standard allowable range.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge construction, and in particular relates to a method and system for accurately positioning the first beam section of a segmental beam using a short-line matching method. Background Art

[0002] The short-line matching method is difficult to control the cantilever line shape of segmental beams, and requires high precision. In particular, the installation precision of the first beam section is difficult to control, and has a great impact on the line shape of the completed bridge. One of the main reasons for many projects with unsatisfactory line shape control is the low installation precision of the first beam section. Once the first beam section has vertical and horizontal angular deviations, the baseline will be inaccurate, which will seriously affect the line shape of the entire T-beam section of the completed bridge. The change trend will be gradually amplified, resulting in misalignment of the joint section and large line shape deviation.

[0003] Currently, a bridge crane and overhead crane are typically used as a positioning construction system to adjust the plane and elevation of the first segment beam, thereby positioning the first segment. However, positioning the first segment using only the overhead crane has low accuracy and fails to meet regulatory requirements. This fails to fully utilize the advantages of segmental prefabricated adhesive-bonded simply supported box girders, hindering the widespread use of segmental adhesive-bonded simply supported box girders.

[0004] The reasons that affect the installation accuracy of the first beam section are as follows: 1. The tensioning of the threaded steel bars in the brackets beside the pier is not in place, resulting in poor stability and affecting the positioning accuracy of the first beam section; 2. The brackets beside the pier are not pre-stressed to eliminate inelastic deformation; 3. The positioning of the outriggers in the bridge erection machine deviates, resulting in eccentric loads and affecting the geometric posture of the first beam section; 4. The prism rod is not vertical, resulting in deviation in the measurement data; 5. The plane coordinate data of the monitoring instructions has not been converted into the coordinates of the bridge axis coordinate system, the direction of the beam adjustment is not intuitive, and it is easy to make mistakes, and the work efficiency is also low; 6. The incorrect method of selecting the elevation control point encryption method results in inaccurate measurement of the benchmark point, affecting the alignment of the first beam section; 7. The displacement of the pier body was not monitored before and after the auxiliary legs of the bridge erection machine were put into place, and no pre-deflection treatment was performed when adjusting the first beam section; 8. The vertical deviation of the pier body during construction was too large. After the large-tonnage bridge-building machine passed through the hole, the pier body was subjected to eccentric force, resulting in displacement of the geometric posture of the first beam section. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for accurately positioning the first section of a segmental beam using a short-line matching method, so as to overcome the above-mentioned technical problems existing in the prior art.

[0006] To this end, the technical solutions provided by the present invention are as follows: A method for accurately locating the first beam section of a segmental beam using a short-line matching method includes the following steps: After the beam segments are prefabricated, the local coordinate values of the cast-in-place position control points of each beam segment are converted to the overall coordinate system of the installation alignment to obtain the target value of the alignment control during the installation phase. During the erection of the main beam, the alignment measurement points of the main beam are kept consistent with the prefabrication measurement points, and monitoring is carried out using stainless steel measurement points embedded during the prefabrication process. Before adjusting the first beam section, pre-stress the brackets beside the piers and arrange settlement monitoring points on the brackets to monitor pre-stress deformation; When using a total station to locate the first beam section, the prism centering rod is regularly self-checked and calibrated to eliminate measurement errors caused by the tilt of the centering rod; The symmetrical synchronous tensioning method is used to tension the threaded steel bars of the pier side bracket, and when there is a gap between the pier side bracket and the pier body, it is reinforced with support pads.

[0007] It also includes the use of the zenith distance method for elevation control encryption. The specific process is as follows: set up a total station at the pier base, set the instrument zenith distance to 90 degrees, erect a level rod at the pier base point, and measure the instrument multiple times to read the scale surface reading H 尺 , and then take the average; then adjust the instrument's zenith distance angle to 0 degrees, and measure the distance D from the instrument to the bottom of the beam top elevation to be determined. h , the elevation of the point to be determined is H 引 =H 基 +H 尺 +D h , H 基 It is the height of the pier bottom foundation.

[0008] It also includes multiple displacement monitoring of the pier body before the front auxiliary support legs of the bridge-building machine are put into place and after the pier top block is hoisted, calculating the longitudinal displacement, and comparing and analyzing it with the monitoring data to determine whether the actual monitoring values are consistent with the calculated theoretical values.

[0009] It also includes the use of epoxy mortar to promptly seal the gap between the bottom of the beam section and the pier top after the geometric posture of the first beam section is adjusted into place, and the secondary concrete pouring of the pier top block.

[0010] It also includes positioning the bridge-building machine before and after it passes through the hole by aligning the longitudinal and transverse axes of the legs and controlling their flatness, while controlling the longitudinal slope of the bridge-building machine at 1.8%.

[0011] During the positioning process of the first beam section, the center axis deviation error is controlled within 3mm, the top surface elevation error is controlled within 3mm, and the deviation direction remains in the same direction.

[0012] The control points include elevation control points located at both ends of two elevation control baselines and axis control points located at both ends of an axis control baseline.

[0013] The method to eliminate the measurement error caused by the tilt of the centering rod is as follows: first center the bubble of the centering rod, observe the plane coordinates by two rounds, take the average value, then rotate the centering rod 180 degrees, observe two more rounds, take the average value, and finally take the average value before and after rotation as the basis for controlling the axis of the pier top block.

[0014] When the symmetrical synchronous tensioning method is used to tension the threaded steel bars in the brackets beside the pier, after tensioning them once in sequence, they are checked and tensioned symmetrically one by one to ensure that the tensioning force of each threaded steel bar is qualified and the force is evenly distributed.

[0015] A positioning system for the precise positioning of the first section of a segmental beam using the short-line matching method includes: a pier-side bracket for transferring the weight of the beam to the pier to provide support during construction; a settlement monitoring point for detecting the pre-compression deformation of the pier-side bracket; and a total station for measuring the distance D from the bottom surface of the point to be determined at the top of the beam. h ; Level rod, used to measure the distance H between the total station and the leveling base point at the bottom of the pier 尺 ; A spirit level is set on the top of the beam to locate the point where the beam top elevation is to be determined; the elevation control point 8 and the axis control point 9 on the first beam section 6 are used to control the beam section top surface elevation and the center axis error respectively.

[0016] The beneficial effects of the present invention are: The short-line matching method provided by the present invention is a method for accurately positioning the first section of a segmental beam. By optimizing the construction process of tensioning the threaded steel bars with the brackets beside the piers, the stability of the brackets is enhanced, and deformation and stability failure during the installation of the first section of the beam are prevented, which affects the installation accuracy and construction efficiency of the first section of the beam. Before adjusting the first section of the beam, the brackets are pre-stressed to eliminate the influence of the inelastic deformation of the brackets on the positioning accuracy of the first section of the beam. By controlling the axis deviation and flatness of the middle support leg, the influence of the eccentric load of the thousand-ton bridge erection machine on the linear shape of the first section of the beam is avoided. The prism centering rod is regularly Self-checking and correction are used to eliminate measurement errors caused by the tilt of the centering rod; the zenith distance method is used for elevation control encryption, which has high accuracy and is conducive to the linear control of segmental beam erection; before the auxiliary legs in front of the bridge erection machine are put into place and after the pier top block is hoisted, the pier body is subjected to multiple displacement monitoring to ensure the accuracy of the linear shape under this working condition; the centerline deviation and the vertical elevation positioning accuracy are strictly controlled to improve the positioning accuracy of the first beam section and avoid affecting the changing trend of the geometric linear shape of subsequent segments; after the geometric posture of the first beam section is adjusted into place, the pier top block is poured with secondary concrete to play a role in timely fixation.

[0017] The present invention eliminates the influence of various factors on the positioning accuracy of the first beam section, thereby ensuring that the positioning accuracy of the first beam section is controlled within the allowable range of the specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the pier side bracket installation; Figure 2 Layout diagram of deformation monitoring points of brackets beside piers; Figure 3 This is a schematic diagram of the control of the longitudinal and transverse axes of the middle outrigger; Figure 4 This is a schematic diagram of height transfer using the zenith distance method; Figure 5 This is the schematic diagram of the hoisting of the first beam section; Figure 6 It is the measured data of the pre-deflection monitoring of a certain joint consolidation pier; Figure 7 It is the theoretical data for monitoring the pre-deviation of a certain joint consolidation pier; Figure 8 It is a linear control point arrangement diagram; Figure 9 This is a schematic diagram of the bottom blocking of the first beam section of the consolidation pier.

[0019] In the figure: 1. Pier side bracket; 2. Settlement monitoring point; 3. Total station; 4. Level; 5. Spirit level; 6. First beam section; 7. Front auxiliary support leg; 8. Elevation control point; 9. Axis control point; 10. Beam bottom sealing; 11. Bridge erection machine. DETAILED DESCRIPTION

[0020] The following describes the embodiments of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0021] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided so as to provide a thorough and complete disclosure of the present invention and fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0022] Unless otherwise specified, the terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have meanings consistent with the context of their relevant fields and should not be interpreted as idealized or overly formal.

[0023] Example 1 The present invention provides a method for accurately positioning the first beam section of a segmental beam using a short-line matching method, comprising the following steps: After the beam segments are prefabricated, the local coordinate values of the cast-in-place position control points of each beam segment are converted to the overall coordinate system of the installation alignment to obtain the target value of the alignment control during the installation phase. During the erection of the main beam, the alignment measurement points of the main beam are kept consistent with the prefabrication measurement points, and monitoring is carried out using stainless steel measurement points embedded during the prefabrication process, thus achieving a smooth connection between the prefabrication monitoring data and the erection monitoring. The overall coordinate target geometry database will be provided to the construction department in the form of drawings for geometric monitoring of the entire bridge assembly process. Before adjusting the first beam section 6, pre-compress the bracket 1 beside the pier and arrange settlement monitoring point 2 on the bracket to monitor the pre-compression deformation; eliminate the influence of the bracket's inelastic deformation on the positioning accuracy of the first beam section 6, and the settlement monitoring point 2 is as follows: Figure 2 As shown; When the total station 3 is used to locate the first beam section 6, the prism centering rod is regularly self-checked and calibrated to eliminate the measurement error caused by the tilt of the centering rod; The symmetrical synchronous tensioning method is used to tension the threaded steel bars of the pier side bracket 1, and when there is a gap between the pier side bracket 1 and the pier body, it is reinforced with support pads.

[0024] When the symmetrical synchronous tensioning method is used to tension the threaded steel bars of the pier bracket 1, after tensioning them once in sequence, they should be checked and tensioned symmetrically one by one to ensure that the tension of each threaded steel bar is qualified and the force is evenly distributed. This will enhance the stability of the bracket. At the same time, check whether there is a gap between the bracket components and the pier body. If there is a gap, support pads should be used to reinforce the bracket to prevent deformation and stability failure during the installation of the first beam section 6, which will affect the installation accuracy and construction efficiency of the first beam section 6. Figure 1 shown.

[0025] Example 2 Based on Example 1, this embodiment provides a method for accurately positioning the first section of a segmental beam using a short-line matching method, and also includes elevation control encryption using a zenith distance method.

[0026] The specific process of the zenith distance method is as follows: set up a total station 3 at the pier bottom pedestal position, set the instrument zenith distance to 90 degrees, erect a level rod 4 at the pier bottom leveling base point, set a level rod 5 on the beam top, and measure the instrument multiple times to read the scale surface reading H 尺 , and then take the average; then adjust the instrument's zenith distance angle to 0 degrees, and measure the distance D from the instrument to the bottom of the beam top elevation to be determined. h , the elevation of the point to be determined is H 引 =H 基 +H 尺 +D h , H 基 is the height of the pier bottom cap. Figure 4 shown.

[0027] This method utilizes only the precise distance measurement capabilities of a high-precision total station 3, eliminating the need for angle measurement or refractive index correction. This method offers high accuracy and facilitates alignment control during segmental beam erection. During implementation, joint surveys of additional elevation control points will be strengthened to ensure smooth bridge closure.

[0028] Example 3 Based on Example 1, this embodiment provides a method for accurately positioning the first section of a segmental beam using the short-line matching method, which also includes performing multiple displacement monitoring on the pier body before the front auxiliary support leg 7 of the bridge-building machine 11 is in place and after the pier top block is hoisted, calculating the longitudinal displacement, and comparing and analyzing it with the monitoring data to determine whether the actual monitoring value is consistent with the calculated theoretical value.

[0029] The schematic diagram of the hoisting of the first beam section 6 is as follows Figure 5 As shown, the front auxiliary support leg 7 of the bridge erection machine 11 is positioned on one side of the bracket. When the first beam section 6 is hoisted, the maximum load is 300t, and the pier body will have an eccentric load phenomenon. During construction, monitoring work should be done well, that is, before the front auxiliary support leg 7 of the bridge erection machine 11 is in place and after the pier top block is hoisted, the pier body should be monitored for multiple displacement measurements to calculate the longitudinal displacement (such as Figure 7 ), and monitoring data (such as Figure 6 Comparative analysis is conducted to determine whether the monitored measured values are consistent with the calculated theoretical values, ensuring the accuracy of the line shape under this working condition. This is especially important in high pier areas where the displacement of the pier body due to eccentric loads is large. Monitoring and calculation are particularly important to ensure both the line shape of the completed bridge and the safety of the structure.

[0030] Example 4 Based on Example 1, this embodiment provides a method for accurately positioning the first section of a segmental beam using the short-line matching method, which also includes using epoxy mortar to promptly seal the gap between the bottom of the beam section and the pier top after the geometric posture of the first section 6 is adjusted into place, and performing secondary concrete pouring of the pier top block.

[0031] like Figure 9 As shown, the gap between the bottom of the beam section and the pier top is blocked, and the beam bottom blocking 10 is completed, which plays a role of timely fixing.

[0032] Example 5 Based on Example 1, this example provides a method for accurately positioning the first section of a segmental beam using the short-line matching method, which also includes positioning the bridge-building machine 11 by aligning the longitudinal and transverse axes of the support legs and controlling their flatness before and after the bridge-building machine 11 passes through the hole, while controlling the longitudinal slope of the bridge-building machine 11 at 1.8%.

[0033] The schematic diagram of the control of the longitudinal and transverse axes of the middle support leg is as follows: Figure 3As shown, before the bridge-building machine 11 passes through the hole, the longitudinal and transverse axes of the middle leg are accurately laid out. After passing through the hole, the axis deviation and flatness of the middle leg are strictly controlled to avoid the influence of the eccentric load of the thousand-ton bridge-building machine 11 on the linear shape of the first beam section 6, thereby ensuring the linear shape of the completed bridge and smooth closure.

[0034] Example 6 Based on Example 1, this example provides a method for accurately positioning the first section of a segmental beam using a short-line matching method. During the positioning of the first section 6, the center axis deviation error is controlled within 3 mm, the top surface elevation error is controlled within 3 mm, and the deviation direction remains unidirectional.

[0035] Six control points (4 elevation control points 8 and 2 axis control points 9) are set at the two ends of the two elevation control baselines and the two ends of the axis control baseline. Figure 8 As shown in the figure, during the main girder erection process, the linear measurement points of the main girder should be basically consistent with the prefabrication measurement points. Monitoring is performed using stainless steel measurement points embedded during the prefabrication process to ensure a seamless connection between prefabrication monitoring data and erection monitoring. The overall coordinate target geometry database will be provided to the construction department in the form of drawings for geometric monitoring of the entire bridge assembly process.

[0036] During the measurement and monitoring implementation, the coordinates of the drawing coordinate system have no correlation with the mileage and offset. In order to facilitate on-site measurement and adjustment, the monitoring coordinates under the drawing coordinate system need to be converted into coordinates in the form of route mileage and offset. The coordinate conversion should be performed using software, and the review system should be strictly implemented during the process. The converted coordinates can only be used after review.

[0037] Example 7 Based on Example 1, this example provides a method for accurately positioning the first section of a segmental beam using a short-line matching method. The method for eliminating the measurement error caused by the inclination of the centering rod is as follows: first center the bubble of the centering rod, observe the plane coordinates using two rounds, take the average value, then rotate the centering rod 180 degrees, observe two rounds again, take the average value, and finally take the average value before and after the rotation as the basis for controlling the axis of the pier top block.

[0038] The centering rod serves as the basis for controlling the axis of the pier top block. Otherwise, the measurement data will have large errors, and the adjustment value data will be irregular and lack logic.

[0039] Example 8 This embodiment also provides a positioning system for the above-mentioned short-line matching method for accurately positioning the first section of the segmental beam, comprising: a pier-side bracket 1 for transferring the weight of the beam to the pier to provide support during construction; a settlement monitoring point 2 for detecting the pre-compression deformation of the pier-side bracket; and a total station 3 for measuring the distance D from the bottom surface of the point to be determined at the top of the beam. hLevel rod 4, used to measure the distance H between the total station and the leveling base point at the bottom of the pier 尺 ; A level ruler 5 is set on the top of the beam to locate the point where the beam top elevation is to be determined; the elevation control point 8 and the axis control point 9 on the first section of the beam segment 6 are used to control the elevation of the top surface of the beam segment and the error of the center axis respectively.

[0040] The present invention optimizes the construction process of tensioning the threaded steel bars by the bracket 1 beside the pier to enhance the stability of the bracket, prevent deformation and stability failure during the installation of the first beam section 6, and affect the installation accuracy and construction efficiency of the first beam section 6; before adjusting the first beam section 6, the bracket is pre-pressed to eliminate the influence of the bracket's inelastic deformation on the positioning accuracy of the first beam section 6; by controlling the axis deviation and flatness of the middle support leg, the influence of the eccentric load of the thousand-ton bridge erection machine 11 on the linear shape of the first beam section 6 is avoided; the prism centering rod is regularly self-checked and corrected to eliminate the tilt of the centering rod The measurement error caused by the inclination; the elevation control encryption adopts the zenith distance method, which has high accuracy and is conducive to the linear control of the segmental beam erection; before the auxiliary support leg 7 in front of the bridge erection machine 11 is in place and after the pier top block is hoisted, the pier body is subjected to multiple displacement monitoring to ensure the accuracy of the linear shape under this working condition; the center line deviation and the vertical elevation positioning accuracy are strictly controlled to improve the positioning accuracy of the first beam segment 6 and avoid affecting the changing trend of the geometric linear shape of subsequent segments; after the geometric posture of the first beam segment 6 is adjusted into place, the secondary concrete pouring of the pier top block is carried out to play a role in timely fixation.

[0041] The present invention eliminates the influence of various factors on the positioning accuracy of the first beam section 6, thereby ensuring that the positioning accuracy of the first beam section 6 is controlled within the allowable range of the specification.

[0042] The above examples are merely illustrative of the present invention and do not limit the scope of protection of the present invention. Any design that is identical or similar to the present invention falls within the scope of protection of the present invention.

Claims

1. A method for accurately locating the first section of a segmental beam using a short-line matching method, characterized by: The following processes are included: After the beam segments are prefabricated, the local coordinate values of the cast-in-place position control points of each beam segment are converted to the overall coordinate system of the installation alignment to obtain the target value of the alignment control during the installation phase. During the erection of the main beam, the alignment measurement points of the main beam are kept consistent with the prefabrication measurement points, and monitoring is carried out using stainless steel measurement points embedded during the prefabrication process. Before adjusting the first beam section, pre-stress the brackets beside the piers and arrange settlement monitoring points on the brackets to monitor pre-stress deformation; When using a total station to locate the first beam section, the prism centering rod is regularly self-checked and calibrated to eliminate measurement errors caused by the tilt of the centering rod; The symmetrical synchronous tensioning method is used to tension the threaded steel bars of the pier side bracket, and when there is a gap between the pier side bracket and the pier body, it is reinforced with support pads.

2. The method for accurately positioning the first section of a segmental beam using a short-line matching method according to claim 1 is characterized in that: It also includes the use of the zenith distance method for elevation control encryption. The specific process is as follows: set up a total station at the pier base, set the instrument zenith distance to 90 degrees, erect a level rod at the pier base point, and measure the instrument multiple times to read the scale surface reading H 尺 Then take the average value; then adjust the instrument zenith distance angle to 0 degrees, and measure the distance D from the instrument to the bottom surface of the beam top elevation to be determined. h , the elevation of the point to be determined is H 引 =H 基 +H 尺 +D h , H 基 It is the height of the pier bottom foundation.

3. The method for accurately positioning the first section of a segmental beam using a short-line matching method according to claim 1 is characterized by: It also includes multiple displacement monitoring of the pier body before the front auxiliary support legs of the bridge-building machine are put into place and after the pier top block is hoisted, calculating the longitudinal displacement, and comparing and analyzing it with the monitoring data to determine whether the actual monitoring values are consistent with the calculated theoretical values.

4. The method for accurately positioning the first section of a segmental beam using a short-line matching method according to claim 1 is characterized by: It also includes the use of epoxy mortar to promptly seal the gap between the bottom of the beam section and the pier top after the geometric posture of the first beam section is adjusted into place, and the secondary concrete pouring of the pier top block.

5. The method for accurately positioning the first section of a segmental beam using a short-line matching method according to claim 1 is characterized in that: It also includes positioning the bridge-building machine before and after it passes through the hole by aligning the longitudinal and transverse axes of the legs and controlling their flatness, while controlling the longitudinal slope of the bridge-building machine at 1.8%.

6. The method for accurately positioning the first section of a segmental beam using a short-line matching method according to claim 1 is characterized by: During the positioning process of the first beam section, the center axis deviation error is controlled within 3mm, the top surface elevation error is controlled within 3mm, and the deviation direction remains in the same direction.

7. The method for accurately positioning the first section of a segmental beam using a short-line matching method according to claim 1 is characterized by: The control points include elevation control points located at both ends of two elevation control baselines and axis control points located at both ends of an axis control baseline.

8. The method for accurately positioning the first section of a segmental beam using a short-line matching method according to claim 1 is characterized in that: The method to eliminate the measurement error caused by the tilt of the centering rod is as follows: first center the bubble of the centering rod, observe the plane coordinates by two rounds, take the average value, then rotate the centering rod 180 degrees, observe two more rounds, take the average value, and finally take the average value before and after rotation as the basis for controlling the axis of the pier top block.

9. The method for accurately positioning the first section of a segmental beam using a short-line matching method according to claim 2, characterized in that: When the symmetrical synchronous tensioning method is used to tension the threaded steel bars in the brackets beside the pier, after tensioning them once in sequence, they are checked and tensioned symmetrically one by one to ensure that the tensioning force of each threaded steel bar is qualified and the force is evenly distributed.

10. A positioning system for the method for accurately positioning the first section of a segmental beam using a short-line matching method according to any one of claims 1 to 9, characterized in that: include: Pier side brackets are used to transfer the weight of the beam to the piers and provide support during construction; Settlement monitoring point, used to detect the pre-compression deformation of the bracket beside the pier; total station, used to measure the distance D from the bottom surface of the point to be determined at the top of the beam h ; Level rod, used to measure the distance H between the total station and the leveling base point at the bottom of the pier 尺 ; A spirit level is set on the top of the beam to locate the point where the beam top elevation is to be determined; the elevation control point 8 and the axis control point 9 on the first beam section 6 are used to control the beam section top surface elevation and the center axis error respectively.

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