Method for pushing bridge segments with guardrails

Abstract

The invention relates to the technical field of bridge construction, and particularly discloses a pushing method for a bridge segment with a guardrail, which forms a set of complete pushing construction method for the bridge segment with the guardrail by reasonably arranging a series of steps such as steel box girder hoisting, guide girder mounting, guardrail pouring, pushing operation, girder falling construction and the like. All the steps are tightly matched, the characteristics of a bridge structure and various factors in the construction process are fully considered, the broken-line-shaped front guide beam is adopted to adapt to bridge curve slippage, reasonable guardrail segmentation and anti-cracking measures are arranged to guarantee the guardrail quality, and the pushing precision is guaranteed through pushing and real-time deviation adjustment. The invention aims to solve the technical problem of how to effectively prevent the concrete guardrail from cracking due to complex stress in the pushing process in the pushing construction of the small-radius curve steel box girder.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, and in particular to a method for jacking bridge segments with guardrails. Background Technology

[0002] The incremental launching method is an important construction technique in modern bridge engineering. Its core principle involves setting up an assembly platform at one end of the bridge, prefabricating or assembling bridge segments in sections, and then using hydraulic launching equipment to gradually push the assembled beams along the bridge axis to the designed position. This method effectively reduces under-bridge work when constructing bridges that cross major traffic arteries, minimizing the impact on traffic and the surrounding environment; the construction site is also relatively concentrated, facilitating quality control.

[0003] This project involves the reconstruction of a highway, specifically including a main road that is already open to traffic (such as...). Figure 1 The main road between QD5 and QD6 (as shown) and a newly constructed but not yet open-to-traffic merging road (such as...) Figure 1 (The merging passage between QD4 and QD5 is shown). Since construction is prohibited above the main road (a restricted construction area), but is permitted on the merging passage, the construction passage was chosen to be located beneath the viaduct. However, the presence of the merging passage would affect the hoisting space for the steel beams and building materials above it. To avoid impacting traffic and construction safety, the bridge segments above both the main road and the merging passage were constructed using a jacking method.

[0004] CN110485251B discloses a steel structure bridge with integrated jacking and its construction method. The core of this scheme lies in the fact that the main bridge structure adopts a continuous steel beam, and that bridge deck ancillary facilities such as crash barriers and anti-throw nets are installed on the bridge body before the jacking construction. During the jacking process, the main bridge structure and ancillary facilities are advanced synchronously as a whole, crossing busy traffic areas such as highways and railways in one go.

[0005] However, the existing technology still has significant shortcomings in practical applications, especially in the incremental launching construction of small-radius curved steel box girders. First, the top reinforcing steel bars installed to resist negative bending moments increase the self-weight of the bridge structure, exacerbating the deflection at the cantilever end during the incremental launching stage. For small-radius curved sections with complex stress distribution, this amplifies the tensile stress borne by the concrete guardrail, thereby increasing the risk of cracking. Second, the technology adopts a cyclical process of installing steel beams segment by segment, pouring guardrails, installing anti-throw nets, and then launching. Although this achieves the synchronous advancement of auxiliary structures and the main structure, the process is tightly connected, lacks flexibility in construction organization, and fails to fully utilize the flow-line construction method to optimize the construction rhythm. There is still room for improvement in this key technical issue of improving overall construction efficiency.

[0006] Therefore, in the jacking construction of small-radius curved steel box girders, effectively preventing the concrete guardrails from cracking due to the complex stress during the jacking process has become a major technical problem that urgently needs to be solved. In addition, how to improve overall construction efficiency while ensuring structural safety and quality through optimized construction organization and the adoption of a continuous construction method has also become a secondary technical problem that needs to be addressed. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the technical problem solved by this invention is to provide a method for jacking bridge segments with guardrails. The main solution is to effectively prevent the concrete guardrails from cracking due to the complex stress during the jacking process of small-radius curved steel box girders. The secondary solution is to improve the overall construction efficiency while ensuring structural safety and quality by optimizing the construction organization and adopting a continuous construction method.

[0008] To solve the above problems, the technical solution adopted by the present invention is: a method for jacking bridge segments with guardrails, comprising the following ten specific implementation steps: Step 1: Establish assembly and jacking supports. The supports between the first and third piers are designated as the steel box girder assembly area. Step 2: Hoist the first segment of the front steel box girder onto the support within the assembly area; Step 3: Hoist the front guide beam onto the support within the assembly area; the connection between the front guide beam and the first section of the steel box girder is flush, and the extended part of the front guide beam has an angle with the connection part facing the direction of the jacking curve bend; Step 4: Hoist the remaining segments of the front steel box girder onto the support frame within the assembly area; Step 5: Cast the guardrail on the front steel box girder in sections on the support; the length of each guardrail section shall not exceed 1.5m, and a 0.5m post-casting zone shall be set between adjacent sections, with the post-casting zone distributed at intervals along the longitudinal direction of the bridge; at the same time, anti-crack structural measures shall be set at both ends of the guardrail. Step Six: Push the front steel box girder until the leading beam is erected on the fourth pier; Step 7: Hoist the rear steel box girder onto the support frame within the assembly area, and simultaneously pour the 0.5m post-cast area of ​​the front steel box girder guardrail; Step 8: Push the front and rear steel box girders forward to leave space for the hoisting of the rear guide beam within the assembly area. While hoisting the rear guide beam to the support within the assembly area, pour the guardrails on the rear steel box girder in sections. The length of each guardrail section should not exceed 1.5m, and a 0.5m post-pouring zone should be set between adjacent sections. The post-pouring zones should be distributed at intervals along the longitudinal direction of the bridge. At the same time, anti-crack structural measures should be set at both ends of the guardrail. Step 9: Push the entire steel box girder, consisting of the front and rear steel box girders, to the predetermined position; Step 10: Beam lowering and equipment dismantling; Compared with existing technologies, the beneficial effects of this solution are as follows: 1. In steps five and eight, this application explicitly requires that the length of each guardrail segment not exceed 1.5m, and sets a 0.5m post-cast zone between adjacent segments, with the post-cast zones distributed at intervals along the longitudinal direction of the bridge. This design effectively reduces concrete stress concentration and avoids cracking caused by integral casting and subsequent jacking. Furthermore, the anti-crack construction measures at both ends of the guardrail further enhance its crack resistance. 2. In step three, this application emphasizes that the extended portion of the guide beam and the connecting part have an angle pointing towards the bending direction of the jacking curve. This design allows the guide beam to better guide the steel box girder along the curved path, reducing torsional deformation and local stress during the jacking process, thereby reducing the risk of cracking due to complex stress on the guardrail. 3. In steps seven and eight, this application adopts a continuous construction organization. While hoisting the rear steel box girder, the post-cast area of ​​the front guardrail is poured (step seven). While hoisting the rear guide beam, the rear guardrail is poured in sections (step eight). This assembly line operation method reduces the waiting time between processes and improves the overall construction efficiency. 4. This application divides the jacking process into jacking the front steel box girder (step six) and jacking the entire steel box girder (step nine), allowing for subsequent construction preparations (such as hoisting the rear steel box girder and pouring the guardrail) in the intermediate stage, avoiding the traditional sequential construction and improving the on-site construction progress. 5. The method of this application is particularly suitable for jacking small-radius curved steel box girders, while the prior art focuses more on straight or large-radius curved bridges. Therefore, this application has better adaptability in the construction of complex-shaped bridges.

[0009] Furthermore, the crack-resistant structural measures include setting crack-resistant steel bars or locally incorporating fiber-reinforced concrete.

[0010] Furthermore, the front guide beam and the rear guide beam described in steps three and eight are both prefabricated guide beams, using a truss structure, composed of two welded H-shaped beams, with tie rods supporting and connecting the two guide beams, and openings in the web of the guide beam.

[0011] Furthermore, the jacking described in steps six and nine adopts the walking-type multi-point continuous jacking method, and walking-type jacking equipment is installed on the top of the fourth pier, fifth pier, sixth pier and the first support, third support, fourth support and sixth support.

[0012] Furthermore, during the jacking process described in steps six and nine, the deviation of the steel box girder is measured every 800mm after jacking forward. If the measured transverse and longitudinal deviation of the steel box girder is greater than 200mm, the transverse and longitudinal deviation of the steel box girder needs to be adjusted.

[0013] Furthermore, the beam lowering construction described in step ten includes setting up temporary supports and a hydraulic unloading device at the bottom of the steel box girder, and achieving smooth beam lowering through staged loading.

[0014] Furthermore, the front steel box girder includes the first to fourth steel box girder segments, and the rear steel box girder includes the fifth to eighth steel box girder segments. Attached Figure Description

[0015] Figure 1 This is a construction layout diagram for the jacking method of this application.

[0016] Figure 2 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 1 .

[0017] Figure 3 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 2 .

[0018] Figure 4 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 3 .

[0019] Figure 5 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 4 .

[0020] Figure 6 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 5 .

[0021] Figure 7 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 6 .

[0022] Figure 8 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 7 .

[0023] Figure 9 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 8 .

[0024] Figure 10 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 9 .

[0025] Figure 11 This is a schematic diagram of the elevation of the jacking method used in this application. Figure 10 .

[0026] Figure 12 This is a schematic diagram of the elevation of the leading beam in this application.

[0027] Figure 13 This is a schematic diagram of the guide beam in this application.

[0028] Figure 14 This is a schematic diagram of the elevation of the guide beam in this application.

[0029] Figure 15 This is a schematic diagram of the rear guide beam of this application.

[0030] Figure 16 This is a schematic diagram of the guardrail segment structure during the jacking construction process of this application.

[0031] Figure 17 This is a schematic diagram of the guardrail cross-section during the jacking construction process of this application.

[0032] The reference numerals in the accompanying drawings include: The first steel box girder segment is GL1; the second steel box girder segment is GL2; the third steel box girder segment is GL3; the fourth steel box girder segment is GL4; the fifth steel box girder segment is GL5; the sixth steel box girder segment is GL6; the seventh steel box girder segment is GL7; and the eighth steel box girder segment is GL8.

[0033] Front guide beam QDL; rear guide beam HQL.

[0034] Pier 1 QD1; Pier 2 QD2; Pier 3 QD3; Pier 4 QD4; Pier 5 QD5; Pier 6 QD6; Pier 7 QD7.

[0035] First support ZJ1; Second support ZJ2; Third support ZJ3; Fourth support ZJ4; Fifth support ZJ5; Sixth support ZJ6; Seventh support ZJ7.

[0036] First guardrail HL1; Second guardrail HL2; Third guardrail HL3; Fourth guardrail HL4; Fifth guardrail HL5.

[0037] Area A (First Region); Area B (Second Region). Detailed Implementation

[0038] Example 1 As attached Figures 1 to 11 As shown in the embodiments of this application, a method for jacking bridge segments with guardrails includes the following ten specific implementation steps: Step 1: Establish assembly supports and jacking supports. The supports between the first pier QD1 and the third pier QD3 are set as the steel box girder assembly area. Step 2: Hoist the first segment of the front steel box girder, GL1, onto the support within the assembly area; Step 3: Hoist the front guide beam QDL onto the support within the assembly area; the connection between the front guide beam QDL and the first segment of the steel box girder GL1 is flush, and the extended part of the front guide beam QDL has an angle with the connection part facing the direction of the jacking curve bend; Step 4: Hoist the remaining segments of the front steel box girder onto the support frame within the assembly area; Step 5: Cast the guardrail on the front steel box girder in sections on the support; the length of each guardrail section shall not exceed 1.5m, and a 0.5m post-casting zone shall be set between adjacent sections, with the post-casting zone distributed at intervals along the longitudinal direction of the bridge; at the same time, anti-crack structural measures shall be set at both ends of the guardrail. Step 6: Push the front steel box girder until the front guide beam is erected on the fourth pier QD4; Step 7: Hoist the rear steel box girder onto the support frame within the assembly area, and simultaneously pour the 0.5m post-cast area of ​​the front steel box girder guardrail; Step 8: Push the front and rear steel box girders forward to leave space for the hoisting of the rear guide beam within the assembly area. While hoisting the rear guide beam to the support within the assembly area, pour the guardrails on the rear steel box girder in sections. The length of each guardrail section should not exceed 1.5m, and a 0.5m post-pouring zone should be set between adjacent sections. The post-pouring zones should be distributed at intervals along the longitudinal direction of the bridge. At the same time, anti-crack structural measures should be set at both ends of the guardrail. Step 9: Push the entire steel box girder, consisting of the front and rear steel box girders, to the predetermined position; Step 10: Beam lowering and equipment dismantling.

[0039] The guardrail is constructed in sections as described in steps five and eight. The length of the guardrail shall not exceed 1.5m and a 0.5m post-casting zone shall be set between adjacent sections. The post-casting zones shall be distributed at intervals along the longitudinal direction of the bridge. At the same time, anti-crack structural measures shall be set at both ends of the guardrail.

[0040] The bridge segment jacking process involves seven piers, namely the first pier QD1 to the seventh pier QD7.

[0041] The bridge's horizontal alignment is located at the following points: a transition curve (starting chainage: K0+855.96, ending chainage: K0+857.184, parameter A: 74.162, left-leaning), a circular curve (starting chainage: K0+857.184, ending chainage: K1+026.283, radius: 110m, left-leaning), a transition curve (starting chainage: K1+026.283, ending chainage: K1+076.283, parameter A: 121.687, left-leaning), and a circular curve (starting chainage: K1+076.283, ending chainage: K1+17). The longitudinal profile is located on a vertical curve with a radius of 175m and a leftward deviation, along with transition curves (starting station: K1+171.557, ending station: K1+221.557, parameter A: 93.541, leftward deviation), transition curves (starting station: K1+221.557, ending station: K1+291.557, parameter A: 167.332, rightward deviation), and circular curves (starting station: K1+291.557, ending station: K1+365.081, radius: 400m, rightward deviation). The longitudinal profile is located on a vertical curve with a radius of 1600m.

[0042] The fourth pier, QD4, has a chainage of K1+017, and the sixth pier, QD6, has a chainage of K1+089. The span of the bridge segment to be jacked is 30+42m, with a combined length of 72m. It is located between (circular curve (starting chainage: K0+857.184, ending chainage: K1+026.283, radius: 110m, left-leaning), transition curve (starting chainage: K1+026.283, ending chainage: K1+076.283, parameter A: 121.687, left-leaning), and circular curve (starting chainage: K1+076.283, ending chainage: K1+171.557, radius: 175m, left-leaning)). Therefore, the bridge segment to be jacked is located on a circular curve (R=110m, length approximately 9m), a transition curve (parameter A:121.687, left-leaning, length approximately 50m), and a circular curve (R=175m, length approximately 13m).

[0043] The steel box girder assembly platform is equipped with assembly supports and launching supports arranged according to a radius of 110m, and the launching curve is set according to a radius of 134.671m. Since the radius of the bridge segment being launched is relatively small, the deviation of the steel box girder is measured every 800mm during the launching process. If the transverse and longitudinal deviation of the steel box girder is greater than 200mm, the transverse and longitudinal deviation of the steel box girder needs to be adjusted.

[0044] The bridge segment jacking process involves seven supports, namely the first support ZJ1 to the seventh support ZJ7. Among them, the first support ZJ1, the third support ZJ3, the fourth support ZJ4, and the sixth support ZJ6 are jacking supports; the second support ZJ2, the fifth support ZJ5, and the seventh support ZJ7 are assembly supports.

[0045] The total height of the jacking support is 34.5m. The support uprights are made of Φ800 round pipes, the horizontal braces are made of Φ351*12 round pipes, the diagonal braces are made of Φ159*7 round pipes, and the horizontal braces are made of Φ159*7 round pipes. The top of the support uses four 630×176×13×22 I-beams. The jacking equipment rests on double 450x700 steel walers.

[0046] The jacking support is equipped with a jacking beam, which is made of three 630×176×13×22 I-beams made of Q235B steel. Because the steel box girder has a transverse slope and the left and right sides of the box are at different heights, a jacking beam is placed on top of the jacking equipment during jacking to ensure balanced force distribution. Simultaneously, rigid pads are added to the right side of the box to ensure it is level during jacking.

[0047] The total height of the assembled support frame is 34.5m. The support frame uprights are round pipes with a diameter of 800*16, the horizontal braces are round pipes with a diameter of 351*12, the diagonal braces are round pipes with a diameter of 159*7, the horizontal braces are round pipes with a diameter of 159*7, and the top of the support frame is made of double-splittered 630×176×13×22 I-beams.

[0048] As attached Figures 12 to 13 As shown, the guide beam QDL described in step three is a 31m prefabricated guide beam. The guide beam uses a truss structure, consisting of two welded H-beams connected by tie rods. Openings in the web of the guide beam reduce its weight. It is 31m long and 1.9m high. At the connection points of the guide beam segments, the upper and lower flanges and webs are connected using 10.9s-grade large hexagonal head M27 high-strength bolts and connecting plates. The upper and lower flanges of the guide beam are made of Q355C, and the rest are all Q355B. The guide beam is rigidly connected to the steel bridge. The main web of the guide beam is butt-welded to the web of the steel box girder using a full-penetration single-sided bevel weld, and the bottom plate of the guide beam is butt-welded to the bottom plate of the steel box girder using a full-penetration single-sided bevel weld. The guide beam is a prefabricated guide beam. Because of the large radius of curvature of the bridge surface, the connection between the leading beam QDL and the first segment of the steel box girder GL1 is flush. However, the extended part of the leading beam and the connection part have an angle in the direction of the jacking curve. The leading beam QDL is processed and installed according to the jacking radius by using this method of folding instead of bending, which can ensure that the bridge can slide normally along the bridge surface.

[0049] As attached Figures 14 to 15 As shown, the rear guide beam HDL mentioned in step eight adopts a 15m prefabricated guide beam. The guide beam uses a truss structure and is composed of two welded H-beams. The two guide beams are connected by tie rods. The web of the guide beam has openings to reduce its weight. The total length is 15m, the width is 7.5m, and the height is 1.9m. The upper and lower flange plates of the guide beam are made of Q355C, and the rest are all made of Q355B. The guide beam is rigidly connected to the steel bridge. The main limb web of the guide beam and the web of the steel box girder are butt welded with full penetration single-sided bevel welds. The bottom plate of the guide beam and the bottom plate of the steel box girder are butt welded with full penetration single-sided bevel welds.

[0050] The guardrail is constructed in sections as described in steps five and eight. Each section of guardrail is no more than 1.5m long and a 0.5m post-casting zone is set between adjacent sections. The post-casting zones are distributed at intervals along the longitudinal direction of the bridge. Crack-resistant structural measures are set at both ends of each section of guardrail, such as setting crack-resistant steel bars or locally adding fiber concrete, to prevent the guardrail from cracking during the jacking process.

[0051] Because the bridge is located on multiple transition curves and circular curves, and the on-site construction space is relatively small, the bridge segments to be jacked up are divided into eight segments along the longitudinal direction of the main bridge, namely the first to the eighth steel box girder GL8. The first to the fourth steel box girder segments are called the front steel box girder, and the fifth to the eighth steel box girder segments are called the rear steel box girder. This allows for segmented manufacturing, hoisting, and assembly, enabling each segment to better adapt to the curve alignment while allowing construction to be carried out in a smaller operating space.

[0052] The bridge segment jacking was carried out using a walking-type multi-point continuous jacking method. The pier columns between the first pier QD1, the second pier QD2, and the third pier QD3 were used to set up the steel box girder assembly area. Within the assembly area, a 220-ton truck crane was used to assemble the steel box girder segments and install the leading beam QDL. Walking-type jacking equipment was installed on the top of the fourth pier QD4, the fifth pier QD5, the sixth pier QD6, and the first support ZJ1, the third support ZJ3, the fourth support ZJ4, and the sixth support ZJ6.

[0053] During the periodic jacking process described in steps six and nine, the deviation of the steel box girder is measured every 800mm after jacking forward. If the transverse and longitudinal deviation of the steel box girder is greater than 200mm, the transverse and longitudinal deviation of the steel box girder needs to be adjusted.

[0054] Step 10 describes the beam lowering construction, which includes setting up temporary supports and a hydraulic unloading device at the bottom of the steel box girder, and achieving smooth beam lowering through staged loading.

[0055] During the lowering process, the loading speed of the hydraulic unloading device must be strictly controlled to ensure the smooth descent of the steel box girder. After the girder is in place, the guide beam, supports, and jacking equipment are removed, completing the jacking construction of the entire bridge segment. When lowering the steel box girder, the hydraulic jacks simultaneously lift it, with the stroke controlled within 50mm, lifting the girder. A 10mm thick steel pad is then removed from the top of the temporary support, and the jacks retract simultaneously, allowing the steel box girder to fall onto the temporary support. This process is repeated until the steel box girder reaches the permanent support, completing the lowering of the steel box girder.

[0056] Before the formal jacking construction, a stress analysis of the jacking process of the steel box girder of the bridge jacking segment was carried out based on the preset working conditions.

[0057] The jacking process of the steel box girder was simulated and analyzed based on preset working conditions. The overall structural analysis was performed using the ABAQUS calculation program to analyze different working conditions. The preset working conditions considered the simultaneous jacking of the bridge deck and guardrail. By simulating the jacking process, the strength and deformation of the steel box girder were understood, and potential problems were identified and corresponding measures were taken in a timely manner.

[0058] Specifically, the stress analysis during the simulated jacking process includes eight preset working conditions, namely: Working condition 1: The front end of the guide beam QDL will be pushed onto the support of the fourth pier QD4, with a maximum cantilever of about 30m.

[0059] Working condition 2: The front end of the guide beam QDL will be pushed onto the support of the fifth pier QD5, with a maximum cantilever of about 30m.

[0060] Condition 3: The front end of the guide beam QDL will be pushed onto the support frame of the sixth pier QD6, with a maximum cantilever of approximately 42m.

[0061] Condition 4: After the jacking is completed, the front guide beam QDL and the rear guide beam HDL are removed.

[0062] Condition 5: The sixth pier is located at the front end of the QDL leading beam.

[0063] Condition 6: The front end of the QDL leading beam passes the sixth pier by 10m.

[0064] Condition 7: The leading beam QDL passes the sixth pier by 20m.

[0065] Condition 8: The leading beam QDL passes the sixth pier by 30m.

[0066] The analysis summary of the eight working conditions obtained by the ABAQUS calculation program is as follows:

[0067] As attached Figures 16 to 17 As shown, in order to analyze the stress of the concrete guardrail during the jacking construction, a spatial finite element model of the composite beam segment with guardrail was established using ABAQUS. The segment model length is 15m. The bridge deck and concrete guardrail of the model are built using solid elements, and the steel beam is built using shell elements. The element size is about 0.1m, and the bridge deck is divided into two layers of elements in the thickness direction. The boundary conditions include: (1) applying the corresponding displacement boundary at the end of the ABAQUS segment model (the overall calculation model is based on the displacement at 7.5m to the left and right of the top of pier #5 under the maximum cantilever condition) to more realistically reflect the stress of the structure; (2) applying vertical surface constraints at the bottom of the steel beam at 7.5m of the segment model to reflect the influence of the support. The segmented casting of the guardrail is adopted. The guardrail segment length is considered for verification in three cases: 2.5m, 2.0m and 1.5m. Five guardrail segments are established in the model, namely the first guardrail HL1 to the fifth guardrail HL5, with a 0.5m post-cast section reserved between the guardrails.

[0068] According to Saint-Venant's principle, the stress distribution within a distance of one beam height from the boundary condition is affected by the boundary. Furthermore, the vertical constraints in this model are located in the middle of the model. Therefore, this analysis focuses on the results within the regions of the second guardrail HL2 and the third guardrail HL3. When analyzing the guardrail results, the first region A and the second region B are distinguished.

[0069] When using a 2.5m guardrail scheme, based on the Mises stress results of the bridge deck and concrete guardrail, it can be seen that the tensile stress range of the bridge deck in the areas from the second guardrail HL2 to the fourth guardrail HL4 is 4~8.5MPa, with the tensile stress in the bridge deck in the area of ​​the third guardrail HL3 ranging from 6~8.5MPa, and the local tensile stress in the post-cast area of ​​the guardrail reaching 10.4MPa; the tensile stress at the bottom of the concrete guardrail, except for a few corner units reaching 5.10MPa, is basically in the range of 1.5~4.5MPa, the tensile stress in the first area A of the guardrail is in the range of 1.8~4.5MPa, and the tensile stress in the second area B of the guardrail is within 1.8MPa.

[0070] When using a 2.0m guardrail scheme, based on the Mises stress results of the bridge deck and concrete guardrail, it can be seen that the tensile stress range of the bridge deck in the areas from the second guardrail HL2 to the fourth guardrail HL4 is 4~8.5MPa, with the tensile stress in the bridge deck in the area of ​​the third guardrail HL3 ranging from 6~8.5MPa, and the local tensile stress in the post-cast area of ​​the guardrail reaching 9.51MPa; the tensile stress at the bottom of the concrete guardrail, except for a few corner units reaching 4.72MPa, is basically in the range of 1.5~4.0MPa, the tensile stress in the first area A of the guardrail is in the range of 1.5~4.0MPa, and the tensile stress in the second area B of the guardrail is within 1.5MPa.

[0071] When using a 1.5m guardrail scheme, based on the Mises stress results of the bridge deck and concrete guardrail, it can be seen that the tensile stress range of the bridge deck in the areas from the second guardrail HL2 to the fourth guardrail HL4 is 4~8.5MPa, with the tensile stress in the bridge deck in the area of ​​the third guardrail HL3 ranging from 6~8.5MPa, and the local tensile stress in the post-cast area of ​​the guardrail reaching 9.25MPa; the tensile stress at the bottom of the concrete guardrail, except for a few corner units reaching 4.26MPa, is basically in the range of 1.5~3.5MPa, the tensile stress in the first area A of the guardrail is in the range of 1.2~3.5MPa, and the tensile stress in the second area B of the guardrail is within 1.2MPa.

[0072] The above analysis results are summarized in the table below. Considering the comprehensive calculation results and actual construction operability, a 1.5m segmented guardrail design is adopted, and the risk of guardrail cracking during the jacking construction process is controllable. Furthermore, anti-crack reinforcement bars are installed in the first area A of the guardrail, or fiber-reinforced concrete is incorporated locally to further enhance the guardrail's crack resistance.

[0073]

[0074] The implementation principle of this embodiment is as follows: by rationally arranging a series of steps such as steel box girder hoisting, guide beam installation, guardrail pouring, jacking operation, girder lowering construction, and simulation analysis, a complete method for jacking bridge segments with guardrails is formed. Each step is closely coordinated, fully considering the characteristics of the bridge structure and various factors during construction. A polygonal guide beam (QDL) is used to adapt to the bridge's curved slippage; reasonable guardrail segmentation and crack-resistant measures are set to ensure guardrail quality; periodic jacking and real-time offset adjustment ensure jacking accuracy; and simulation analysis of preset working conditions is conducted to predict structural safety in advance.

[0075] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for jacking bridge segments with guardrails, characterized in that: It includes the following ten specific implementation steps: Step 1: Establish assembly and jacking supports. The supports between the first and third piers are designated as the steel box girder assembly area. Step 2: Hoist the first segment of the front steel box girder onto the support within the assembly area; Step 3: Hoist the front guide beam onto the support within the assembly area; the connection between the front guide beam and the first section of the steel box girder is flush, and the extended part of the front guide beam has an angle with the connection part facing the direction of the jacking curve bend; Step 4: Hoist the remaining segments of the front steel box girder onto the support frame within the assembly area; Step 5: Cast the guardrails on the front steel box girder in sections on the support frame; Step Six: Push the front steel box girder until the leading beam is erected on the fourth pier; Step 7: Hoist the rear steel box girder onto the support frame within the assembly area, and simultaneously pour the 0.5m post-cast area of ​​the front steel box girder guardrail; Step 8: Push the front and rear steel box girders forward to leave space for the rear guide beam in the assembly area. While hoisting the rear guide beam to the support in the assembly area, pour the guardrail on the rear steel box girder in sections. Step 9: Push the entire steel box girder, consisting of the front and rear steel box girders, to the predetermined position; Step 10: Beam lowering and equipment dismantling; In the segmented pouring construction of the guardrail described in steps five and eight, the length of the guardrail shall not exceed 1.5m and a 0.5m post-pouring zone shall be set between adjacent sections. The post-pouring zones shall be distributed at intervals along the longitudinal direction of the bridge. At the same time, anti-crack structural measures shall be set at both ends of the guardrail.

2. The bridge segment jacking method according to claim 1, characterized in that: The crack-resistant structural measures include installing crack-resistant steel bars or locally incorporating fiber-reinforced concrete.

3. The bridge segment jacking method according to claim 1, characterized in that: The front and rear guide beams described in steps three and eight are both prefabricated guide beams with a truss structure, consisting of two welded H-shaped beams. The two guide beams are connected by tie rods, and the web of the guide beam has openings.

4. The bridge segment jacking method according to claim 1, characterized in that: Steps six and nine describe the jacking method, which employs a walking-type multi-point continuous jacking method. Walking-type jacking equipment is installed on the top of the fourth, fifth, and sixth piers and the first, third, fourth, and sixth supports.

5. The bridge segment jacking method according to claim 1, characterized in that: During the jacking process described in steps six and nine, the deviation of the steel box girder is measured every 800mm after jacking forward. If the transverse and longitudinal deviation of the steel box girder is greater than 200mm, the transverse and longitudinal deviation of the steel box girder needs to be adjusted.

6. The bridge segment jacking method according to claim 1, characterized in that: Step 10 describes the beam lowering construction, which includes setting up temporary supports and a hydraulic unloading device at the bottom of the steel box girder, and achieving smooth beam lowering through staged loading.

7. The bridge segment jacking method according to claim 1, characterized in that: The front steel box girder includes the first to fourth steel box girder segments, and the rear steel box girder includes the fifth to eighth steel box girder segments.

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