Pier underpinning method for steel box girder

Abstract

The invention discloses a bridge pier underpinning method for a steel box girder, and relates to the technical field of bridge engineering. Aiming at the problems that the road clearance height is insufficient, the construction period is long and the structural stability is difficult to guarantee due to the existing bridge pier underpinning method, the bridge pier underpinning method of the steel box girder comprises the following steps of: respectively connecting cross beams on two sides of the cross beams of the existing steel box girder to extend and lengthen, supporting the other end of the extension section of the cross beam on a newly-arranged bridge pier upright post, and then, connecting the cross beams with the bridge pier upright post; a jack set is arranged between a new bridge pier stand column and a cross beam extending section, the jack set is synchronously pressurized to the value the same as the actual dead load vertical force in a grading mode through a hydraulic synchronous jacking system, it is ensured that the vertical force borne by an original bridge pier stand column top face support is transferred to the jack set, and finally a permanent support is installed on the top face of the new bridge pier stand column. And the jack set is synchronously unloaded, so that the existing bridge pier is supported on the newly-built bridge pier through the cross beam extension section.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge engineering, in particular to a method for supporting and replacing a pier of a steel box girder. BACKGROUND

[0002] With the rapid development of urban construction, the widening reconstruction and new construction of ground roads in the urban construction process are increasing, and the space position conflict between the road clearance limit and the existing bridge substructure is inevitable. Due to the limitation of the planning red line and the specification requirements of the road alignment, there is no way to avoid the existing bridge pier, so it is necessary to support and replace the existing bridge pier to move out of the proposed road driving range.

[0003] The existing pier supporting and replacing method mainly pours new frame-type pier columns and beams, and completes the supporting and replacing by system conversion to make the existing bridge girder fall on the new beam. However, in the application scenario of limited bridge clearance, the beam of the supporting and replacing structure may further occupy the bridge space, resulting in serious shortage of road clearance height. If the road is excavated to meet the road clearance, not only the conflict risk with existing underground facilities will be increased, but also the engineering investment will be greatly increased. In addition, the existing supporting and replacing construction technology also involves complex temporary support system, long construction period, great impact on traffic and difficult to guarantee the stability of the structure during load transfer. Therefore, how to complete the pier supporting and replacing in the application scenario of limited bridge clearance and guarantee the road traffic clearance requirement has become a technical problem to be solved. SUMMARY

[0004] In view of the problems that the existing pier supporting and replacing method leads to insufficient road clearance height, long construction period and difficult to guarantee the stability of the structure, the purpose of the present application is to provide a method for supporting and replacing a pier of a steel box girder, which not only solves the problem of pier supporting and replacing in the scenario of limited bridge clearance, but also avoids using temporary support structure, saves investment and has higher stability and safety.

[0005] The technical solution adopted by the present application to solve the technical problem is: a method for supporting and replacing a pier of a steel box girder, comprising the following steps:

[0006] S1: calculating and determining the cross-sectional size and length of the extension section of the existing steel box girder beam on both sides of the beam, and prefabricating and processing a beam extension section which can be aligned and spliced with the ends of the existing steel box girder beam;

[0007] S2: on-site construction of new bridge piers on both sides of the existing pier, on-site cutting of parts of the existing steel box girder beam that conflict with the beam extension section, welding and connecting the two beam extension sections on both sides of the existing steel box girder beam, and placing the ends of the beam extension section on the temporary supports at the center of the top surface of the new pier column, respectively;

[0008] S3: A jack group is arranged between the new pier column and the beam extension section, the jack group is synchronized to the same value as the actual vertical force of the dead load, the vertical force supported by the existing pier column top surface support is transferred to the jack group, and the jack group is locked;

[0009] S4: A permanent support is installed on the top surface of the new pier column, the jack group is simultaneously unloaded, the main beam of the existing bridge is supported on the permanent support through the beam extension section on both sides, and the jack group, the existing pier column top support, the existing pier column, and the clearance limit of the road under the bridge are removed.

[0010] The pier underpinning method of the steel box girder of the application first connects the beam extension sections on both sides of the existing steel box girder beam to lengthen the beam, supports the other end of the beam extension section on the newly set pier column, then arranges a jack group between the new pier column and the beam extension section, synchronously pressurizes the jack group to the same value as the actual vertical force of the dead load through the hydraulic synchronous jacking system, ensures that the vertical force supported by the original pier column top surface support is transferred to the jack group, and finally installs a permanent support on the top surface of the new pier column, synchronously unloads the jack group, so that the existing pier is supported on the newly built pier through the beam extension section; The pier underpinning method of the steel box girder has at least the following beneficial effects:

[0011] 1. The beam extension section replaces the traditional underpinning beam, the existing steel box girder beam is lengthened by the beam extension section, the other end of the beam extension section is supported on the newly set pier column, the bridge clearance is avoided, the elevation of the road surface under the bridge is ensured, and the problem of pier underpinning in the scene where the bridge clearance is limited is solved;

[0012] 2. A jack group is arranged between the new pier column and the beam extension section, during the underpinning construction process, the load borne by the existing pier is directly transferred to the newly built pier by using the jack group, without the need for additional temporary construction support, avoiding the secondary underpinning construction of the conventional scheme, saving the construction period and construction cost, and having higher stability and safety;

[0013] 3. During the underpinning construction process, the hydraulic synchronous jacking system using differential speed control technology can control two jack groups at the same time, solve the problem of inconsistent bearing capacity on both sides of the beam and difficult synchronization of jacking, ensure that the main beam of the existing bridge does not occur lateral torsion, and avoid the generation of additional internal forces in the main beam which are not conducive to the safety of the structure.

[0014] Further, in the step S1, the prefabricated processing of the beam extension section is as follows: collecting the three-dimensional data of the existing steel box girder, including using three-dimensional laser scanning technology to conduct three-dimensional spatial positioning surveying and mapping of the existing steel box girder, determining the accurate position of each component of the existing steel box girder, establishing a refined model of the existing steel box girder through finite element analysis software, and combining with the actual situation, conducting overall stress analysis of the existing steel box girder to calculate and determine the cross-sectional size and length of the beam extension section located on both sides of the beam of the existing steel box girder.

[0015] Further, in the step S1, the beam extension section adopts a box-shaped steel structure and is made of steel materials of the same grade as the existing steel box girder.

[0016] Further, in the step S2, the web plate of the beam extension section is aligned with the partition plate of the beam of the existing steel box girder, the top plate and the bottom plate of the beam extension section are respectively aligned with the top plate and the bottom plate of the beam of the existing steel box girder, and the welding seam between the beam extension section and the beam of the existing steel box girder adopts full penetration.

[0017] Further, in the step S3, one jack set is arranged between the top surface of each new bridge pier column and the bottom surface of each beam extension section, each jack set includes two jacks arranged on both sides of the temporary support along the width direction of the bridge deck, and the number and type of the jacks of the two jack sets are the same.

[0018] Further, in the step S3, the jacking process of the jack set is implemented in stages, the number of stages is determined according to the size of the theoretical calculation value of the overall model of the existing steel box girder, and an emergency mechanical locking device is arranged for each jack.

[0019] Further, in the step S3, the jack set adopts differential speed control technology to realize hydraulic synchronous jacking.

[0020] Further, in the step S4, the permanent support installation step is as follows: first pouring support cushion stones on the top surface of the new bridge pier column, then connecting leveling steel plates on the top of the permanent support, and then installing the bottom of the permanent support on the support cushion stones. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A cross-sectional view of the original bridge pier in an example of the pier underpinning method of the steel box girder of the present application;

[0022] Figure 2 A construction process diagram of an example of the pier underpinning method of the steel box girder of the present application;

[0023] Figure 3 A-A cross-sectional view of Figure 2 ;

[0024] Figure 4This is a schematic diagram of the steel box girder pier underpinning construction after completion according to an example of the present invention.

[0025] The numbers in the figure are as follows:

[0026] Existing pier column 1; existing steel box girder crossbeam 2; cantilever web 21; lower flange plate 24; outer side baffle 25; partition 26; crossbeam extension 4; web 42 of crossbeam extension; existing pier support 5; new pier 30; new pier pile foundation 31; new pier cap 32; new pier column 34; jack assembly 35; temporary support 36; support pad 37; leveling steel plate 39; permanent support 38; ground line 50; clearance limit of road under the bridge 60. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are highly simplified and not to exact scale, and are intended solely to facilitate and clearly illustrate the embodiments of the present invention. For ease of description, the terms "upper" and "lower" will be used in the following text in the same direction as in the accompanying drawings, but this does not constitute a limitation of the present invention.

[0028] Combine Figures 1 to 4 The method for underpinning a steel box girder pier of the present invention is described in detail in the following steps:

[0029] S1: Calculate and determine the cross-sectional dimensions and lengths of the beam extension sections 4 on both sides of the existing steel box beam 2, and prefabricate in the factory two beam extension sections 4 that can be aligned and spliced ​​with both ends of the existing steel box beam 2;

[0030] S2: If Figure 2 As shown, new bridge piers 30 are constructed on both sides of the existing bridge piers on site to replace the existing bridge piers. The new bridge piers 30 include new bridge pier pile foundations 31, new bridge pier caps 32, and new bridge pier columns 34 connected in sequence from bottom to top. After the construction of the new bridge piers 30 is completed, the existing bridge surface is temporarily controlled. The parts of the existing steel box girder cross beam 2 that conflict with the cross beam extension section 4 are cut on site, including the cantilever web 21, the lower flange plate 24, and the outer side baffle 25. The existing steel box girder cross beam 2 is polished and cleaned at the intended welding position. The two cross beam extension sections 4 are welded to the two sides of the existing steel box girder cross beam 2, and the two ends of the cross beam extension section 4 are respectively placed on temporary supports 36 at the center of the top surface of the new bridge pier column 34.

[0031] S3: If Figure 3 As shown, a jack group 35 is arranged between the top surface of the new pier column 34 and the bottom surface of the crossbeam extension section 4. The jack groups 35 are synchronously and stepwise pressurized to the same value as the actual dead load vertical force through a hydraulic synchronous jacking system, ensuring that the vertical force supported by the top surface support of the existing pier column 1 is transferred to the jack group 35, and the height of the jack group 35 is locked;

[0032] S4: As Figure 4 As shown, permanent supports 38 are installed on the top surface of the new pier column 34, and the jack group 35 is simultaneously unloaded, so that the main beam of the existing bridge is supported on the permanent supports 38 through the crossbeam extension sections 4 on both sides. The jack group 35, the top surface supports of the existing pier column 1, and the existing pier column 1 are removed, and the ground is cleaned and restored, completing the replacement of the existing pier support and the clearance limit 60 of the road under the bridge.

[0033] The present invention provides a method for underpinning a pier of a steel box girder. First, a crossbeam extension section 4 is connected to both sides of the existing steel box girder crossbeam 2 to lengthen the crossbeam. The other end of the crossbeam extension section 4 is supported on a newly erected pier column. Then, a jack assembly 35 is arranged between the new pier column 34 and the crossbeam extension section 4. The jack assembly 35 is synchronously and staged pressurized to a value equal to the actual dead load vertical force via a hydraulic synchronous jacking system, ensuring that the vertical force supported by the top surface support of the original pier column is transferred to the jack assembly 35. Finally, a permanent support 38 is installed on the top surface of the new pier column 34, and the jack assembly 35 is simultaneously unloaded, so that the existing pier is supported on the newly built pier 30 via the crossbeam extension section 4. This method for underpinning a pier of a steel box girder has at least the following beneficial effects:

[0034] 1. The traditional underpinning beam is replaced by the beam extension 4. The existing steel box girder beam 2 is extended and lengthened by the beam extension 4. The other end of the beam extension 4 is supported on the newly established pier column, avoiding encroachment on the clearance under the bridge and ensuring that the elevation of the road surface under the bridge remains unchanged. This solves the problem of pier underpinning in scenarios with limited clearance under the bridge.

[0035] 2. A jack assembly 35 is arranged between the new pier column 34 and the crossbeam extension 4. During the underpinning construction process, the jack assembly 35 is used to directly transfer the load borne by the existing pier to the new pier 30, eliminating the need for additional temporary support. This avoids the secondary underpinning construction required in conventional solutions, shortening construction time and costs while also providing greater stability and safety.

[0036] 3. During the underpinning construction process, the hydraulic synchronous jacking system using differential speed control technology can simultaneously control two jack groups 35, solving the problem of inconsistent bearing capacity on both sides of the beam and making synchronous jacking difficult. This ensures that the main beam of the existing bridge does not experience lateral torsion and avoids the generation of additional internal forces in the main beam that are detrimental to structural safety.

[0037] The steel box girder pier underpinning method is particularly suitable for pier underpinning projects with limited underbridge clearance, such as urban road reconstruction and subway construction. It has significant economic and social benefits and broad application prospects.

[0038] In the step S1, the prefabricated extension section 4 of the cross beam is processed as follows: collecting the three-dimensional data of the existing steel box girder, including three-dimensional spatial positioning surveying of the existing steel box girder by using three-dimensional laser scanning technology, determining the accurate positions of each component of the existing steel box girder, establishing a refined model of the existing steel box girder by using finite element analysis software, conducting overall stress analysis of the existing steel box girder in combination with the actual situation on site, calculating and determining the extension implementation scheme of the cross beam 2 of the existing steel box girder, and reasonably determining the cross-sectional size and length of the cross beam extension section 4 located on both sides of the cross beam 2 of the existing steel box girder, so as to ensure that the cross beam 2 of the existing steel box girder and the cross beam extension sections 4 on both sides can be tightly connected.

[0039] In the step S1, the cross beam extension section 4 adopts a box-shaped steel structure and is made of steel materials of the same grade as the existing steel box girder.

[0040] In the step S2, as shown in Figure 2 , the web plate 42 of the cross beam extension section 4 is aligned with the partition plate 26 of the cross beam 2 of the existing steel box girder, the top plate and the bottom plate of the cross beam extension section 4 are respectively aligned with the top plate and the bottom plate of the cross beam 2 of the existing steel box girder, and the welding seams between the cross beam extension section 4 and the cross beam 2 of the existing steel box girder adopt full penetration.

[0041] In the step S3, as shown in Figure 2 and Figure 3 , one jack group 35 is arranged between the top surface of each new pier column 34 and the bottom surface of each cross beam extension section 4, each jack group 35 includes two jacks arranged on both sides of the temporary support 36 along the width direction of the bridge deck, the number and type of the jacks of the two jack groups 35 are the same, so that the jack group 35 not only avoids the installation space of the permanent support 38, but also makes the stress of the cross beam extension section 4 more balanced.

[0042] In the step S3, the process of the jack group 35 for jacking should be implemented in stages, and the number of stages should be determined according to the size of the theoretical calculation value of the overall model of the existing steel box girder. In this embodiment, the jack group 35 is loaded in five stages (such as 20%, 40%, 60%, 80%, and 100%), and each stage of loading should be carried out slowly, and the jacks should be provided with an emergency mechanical locking device.

[0043] In the step S3, considering that the lengths of the cross beam extension sections 4 on both sides of the cross beam 2 of the existing steel box girder are different, the actual vertical constant load forces at the two ends of the cross beam extension section 4 will be different, and the jack group 35 needs to use differential speed control technology to realize hydraulic synchronous jacking, and the displacement of the existing steel box girder is monitored in real time, so that the elevation of the existing steel box girder is dynamically kept balanced. The above-mentioned differential speed control technology refers to the independent but coordinated speed adjustment of multiple interrelated hydraulic jacks, so that they can realize synchronous jacking.

[0044] In the step S4, the permanent support 38 is installed in the following steps: first, the support cushion stone 37 is cast on the top surface of the new pier column 34, then the leveling steel plate 39 is connected on the top of the permanent support 38, and finally the bottom of the permanent support 38 is installed on the support cushion stone 37, and the permanent support 38 and the leveling steel plate 39 on the top thereof jointly form a complete support system.

[0045] The above description is only a description of the preferred embodiments of the present application, and is not any limitation on the scope of the present application. Any modification or change made by a person of ordinary skill in the art according to the above disclosure is within the scope of the claims.

Claims

1. A method for underpinning a steel box girder pier, characterized in that: Here are the steps: S1: Calculate and determine the cross-sectional dimensions and lengths of the beam extensions on both sides of the existing steel box girder crossbeam, and prefabricate the beam extensions so that they can be aligned and spliced ​​with both ends of the existing steel box girder crossbeam; S2: On-site construction of new piers located on both sides of the existing piers. Parts of the existing steel box girder that conflict with the crossbeam extensions were cut on-site. The two crossbeam extensions were welded to the two sides of the existing steel box girder. The ends of the crossbeam extensions were placed on temporary supports at the center of the top surface of the new pier columns. S3: Arrange jack groups between the new pier columns and the beam extensions, synchronize the jack groups to the same value as the actual dead load vertical force, transfer the vertical force supported by the existing pier column top surface supports to the jack groups, and lock the jack groups; S4: Install permanent supports on the top surface of the new pier column and simultaneously unload the jack group so that the main beam of the existing bridge is supported on the permanent supports through the crossbeam extension sections on both sides. Remove the jack group, the top support of the existing pier column, the existing pier column, and the clearance limit of the road under the bridge.

2. The method for underpinning a steel box girder pier according to claim 1, characterized in that: In step S1, the steps of prefabricating the crossbeam extension section are as follows: collecting three-dimensional data of the existing steel box girder, including using three-dimensional laser scanning technology to perform three-dimensional spatial positioning and mapping of the existing steel box girder, determining the accurate positions of various components of the existing steel box girder, establishing a refined model of the existing steel box girder through finite element analysis software, and conducting an overall force analysis of the existing steel box girder in combination with actual on-site conditions, and calculating and determining the cross-sectional dimensions and lengths of the crossbeam extension sections located on both sides of the crossbeam of the existing steel box girder.

3. The method for underpinning a steel box girder pier according to claim 1, characterized in that: In step S1, the crossbeam extension section adopts a box-shaped steel structure and is made of the same grade of steel as the existing steel box beam.

4. The method for underpinning a steel box girder pier according to claim 1, characterized in that: In step S2, the web of the crossbeam extension section is aligned with the partition of the existing steel box girder crossbeam, the top plate and bottom plate of the crossbeam extension section are aligned with the top plate and bottom plate of the existing steel box girder crossbeam respectively, and the weld between the crossbeam extension section and the existing steel box girder crossbeam adopts full penetration.

5. The method for underpinning a steel box girder pier according to claim 1, characterized in that: In step S3, one jack group is respectively arranged between the top surfaces of the two new pier columns and the bottom surfaces of the two beam extension sections. Each jack group includes two jacks arranged on both sides of the temporary support along the width direction of the bridge deck. The number and model of jacks in the two jack groups are the same.

6. The method for underpinning a steel box girder pier according to claim 1, characterized in that: In step S3, the jacking process of the jack group is implemented in stages, and the number of stages should be determined according to the size of the theoretical calculation value of the existing steel box girder overall model, and each jack is provided with an emergency mechanical locking device.

7. The method for underpinning a steel box girder pier according to claim 1, characterized in that: In step S3, the jack group uses differential speed control technology to achieve hydraulic synchronous jacking.

8. The method for underpinning a steel box girder pier according to claim 1, characterized in that: In step S4, the permanent support installation steps are as follows: first, cast the support pedestal stone on the top surface of the new pier column, then connect the leveling steel plate to the top of the permanent support, and then install the bottom of the permanent support on the support pedestal stone.

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