An antisymmetric segment assembly continuous box girder external prestress arrangement system and a construction method thereof

Abstract

The application discloses a kind of antisymmetric segment assembly continuous box girder external prestress arrangement system and its construction method, and the continuous box girder structure includes box girder segment, anchoring crossbeam, steering block, external and internal prestressed steel bundle etc..External prestressed steel bundle is arranged in pairs according to structural spacing in transverse direction;The anchoring of the external prestressed steel bundle in pairs at the crossbeam is staggered up and down in vertical direction;Box girder segment is connected by prestressed steel bundle, and forms stressed structure.Structure stress is mainly external prestress, and the segment assembly continuous box girder external prestress arrangement system, by antisymmetric space cable arrangement, makes steel bundle anchoring point staggered orderly, reduces steel bundle additional flat bend and vertical bend type, optimizes steel bundle space cable type, makes steel bundle compact rule, improves external prestress space utilization efficiency, reduces design and construction difficulty.

Description

Technical Field

[0001] This invention relates to the field of civil engineering technology, and in particular to an antisymmetric segmental assembly continuous box girder external prestressing arrangement system and its construction method. Background Technology

[0002] With the rapid development of transportation infrastructure and the continuous improvement of bridge construction standards, the application of segmental assembled box girder bridges in the engineering construction field is also increasing. Segmental assembled continuous box girder bridges achieve industrialized bridge construction through factory prefabrication and on-site assembly technology, resulting in high construction efficiency, a green and environmentally friendly construction process, minimal disruption to existing traffic, and fewer constraints from on-site operating conditions, thus possessing broad application prospects.

[0003] Currently, there are two main structural systems for segmental assembled continuous box girders: span-by-span construction and cantilever assembly. Span-by-span construction of segmental assembled continuous box girders results in a large proportion of external prestressed steel strands, high on-site construction efficiency, and widespread application in spans up to 50m. Internal prestressed steel strands require grouting after tensioning and waiting for the grout to reach the required strength before subsequent construction can proceed. In contrast, the on-site construction process for external prestressed steel strands is simpler and more efficient; subsequent construction can begin immediately after the external prestressed steel strands are tensioned and anchored, reducing the on-site grouting and grout strength waiting period. Therefore, span-by-span assembly of segmental assembled box girders often adopts a construction method of first tensioning the external prestressed steel strands and then tensioning the internal prestressed steel strands. After the box girder segments are hoisted, the external prestressing forms the load-bearing structure, allowing subsequent bridge span construction to begin. At this point, the internal prestressing construction can be carried out simultaneously with subsequent bridge spans without affecting other processes. This construction method results in a large proportion of external prestressed steel strands and high on-site construction efficiency. External prestressed steel strands are arranged inside the box girder cavity, positioned and steered by steering blocks and crossbeams, and anchored to the crossbeams. To meet the needs of prestressing tensioning and local stress on the anchored crossbeams, the prestressing arrangement system and the selection of its anchoring points should consider the corresponding spatial structural requirements. Segmented box girders have a large proportion of external cables, resulting in a large number of steel strands. Especially at the central crossbeam position, since the steel strands on both sides of the bridge span need to be anchored and positioned / steered in the central crossbeam, the conflict between steel strands and anchorages is quite serious. To resolve the spatial conflict in steel strand arrangement, conventional methods generally involve adding additional horizontal bends or adjusting the alignment of the steel strands, leading to complex spatial alignment, low space utilization efficiency, wasted internal space of the box girder, and cumbersome design and construction. How to arrange more external prestressed steel strands within the limited internal space of the box girder and improve the space utilization efficiency of the steel strands is of great significance for segmented box girder structures. Summary of the Invention

[0004] The purpose of this invention is to provide an antisymmetric segmental assembly continuous box girder external prestressing arrangement system and its construction method. External prestressing steel strands are arranged in an antisymmetric manner at the middle crossbeam position, and the steel strand alignment is set according to the antisymmetric law to optimize the spatial cable shape of the steel strands, making the steel strands compact and regular, improving the space utilization efficiency of external prestressing, and reducing the design and construction difficulty.

[0005] This invention is achieved through the following technical solution:

[0006] An anti-symmetrical segmental prestressed continuous box girder external prestressing arrangement system includes a multi-span continuous segmental prestressed box girder; wherein: the segmental prestressed continuous box girder includes box girder segments, internal prestressed steel strands, external prestressed steel strands, steering blocks, middle crossbeams, and end crossbeams; the box girder segments are connected to each other as a whole to form a load-bearing structure through the prestressing action of the internal and external prestressed steel strands; the external prestressed steel strands are arranged in pairs in the transverse direction according to the structural spacing; the anchorage of the paired external prestressed steel strands at the middle crossbeams is staggered vertically; the external prestressed steel strands are positioned and steered by the steering blocks and the middle crossbeams or the end crossbeams. The structural stress is mainly due to external prestressing, and the amount of external prestressed steel strands accounts for more than 70% of the total amount of prestressed steel strands. During construction, the external prestressed steel strands are tensioned first, and after the structure forms a load-bearing system, the internal prestressed steel strands are tensioned. Externally prestressed steel strands are anchored to the crossbeam, and the cable shape is changed by pre-embedding steering gears on the crossbeam and steering blocks.

[0007] As a further improvement to the technical solution of this invention, the paired external prestressed steel strands include front-hole paired steel strands and rear-hole paired steel strands; the front-hole paired steel strands and the rear-hole paired steel strands are arranged anti-symmetrically relative to the central crossbeam; the anchorage points of the front-hole paired steel strands on the central crossbeam are staggered vertically in opposite directions relative to the anchorage points of the rear-hole paired steel strands on the central crossbeam. The problem of conflicting anchorage points is solved through the variation in the vertical cable shape of the steel strands. Simultaneously, the paired steel strands ensure symmetrical balance of local forces at the crossbeam anchorage points.

[0008] As a further improvement to the technical solution of the present invention, the prestressed steel strands in the body are divided into side span cables, middle span cables, and two-span cables; the side span cables and the middle span cables are single-span steel strands, arranged in different bridge spans, and anchored at the crossbeams at both ends of the bridge span where the steel strands are located; the two-span cables are divided into two types according to the position of the steel strands: side span + middle span two-span strands and middle span + middle span two-span strands, with the two-span strands passing through the middle crossbeam and anchored at the corresponding two-end crossbeams.

[0009] As a further improvement to the technical solution of the present invention, the paired mid-span cable vertical bending cable types are anti-symmetrical to each other, the anchorage positions of the start and end points of a single steel strand are staggered vertically, and the cable type of the steel strand from the start point to the end point is consistent with the cable type of the corresponding steel strand from the end point to the start point.

[0010] As a further improvement to the technical solution of the present invention, the side span cables are arranged in pairs, namely the first span cable and the last span cable, and the cable types of the first span cable and the last span cable are arranged in an anti-symmetrical manner relative to the middle crossbeam.

[0011] As a further improvement to the technical solution of the present invention, when the two span cables are only arranged in the middle span, the cable types of the paired steel strands are arranged in an anti-symmetrical manner. If the two span cables are arranged in the first span + middle span, the cable types of the two span cables and the corresponding middle span + tail span cables are arranged in an anti-symmetrical manner.

[0012] As a further improvement to the technical solution of the present invention, when the number of spans of the box girder increases, the steel strands are arranged in a regular manner in an antisymmetric manner in different bridge spans.

[0013] As a further improvement to the technical solution of this invention, a construction method for an external prestressed arrangement system for anti-symmetric segmental assembly continuous box girder includes the following steps:

[0014] Step S1: Complete the construction of the substructure foundation and pier body, and at the same time complete the prefabrication of box girder segments, pier top crossbeams, end crossbeams and middle crossbeams in the prefabrication plant; when prefabricating box girder segments, reserve prestressed steel strand ducts and pre-embedded steering gears according to the prestressing layout requirements.

[0015] Step S2: The bridge erecting machine is moved to the construction span, and the precast segments of the top sections of piers No. 0, No. 1 and No. 2, namely the end crossbeams and the middle crossbeams, are installed using the side pier brackets. After adjusting the position, the crossbeam concrete is poured to achieve the pier-beam consolidation.

[0016] Step S3: Transfer the outriggers of the bridge erecting machine to the top segment of the pier, feed the beams with the beam transport vehicle, hoist all the box girder segments in sequence, and adjust the alignment; apply epoxy resin between the box girder segments in sequence, and tension the temporary fastening device.

[0017] Step S4: Cast the wet joint next to the top segment of the pier, tension the external prestressed steel strands inside the box girder segment, and prepare the bridge erecting machine to move forward.

[0018] Step S5: The bridge erecting machine moves to the next span, installs the precast segment of the crossbeam at the top of pier No. 3, adjusts the position, and then pours the crossbeam concrete.

[0019] Step S6: Transfer the outriggers of the bridge erecting machine to the top segment of the pier, feed the beams with the beam transport vehicle, hoist all the box girder segments in sequence, and adjust the alignment; apply epoxy resin between the box girder segments in sequence, and tension the temporary fastening device.

[0020] Step S7: Cast the wet joint next to the top segment of the pier, tension the external prestressed steel strands inside the box girder segment, and prepare the bridge erecting machine to move forward.

[0021] Step S8: The bridge erecting machine moves forward and constructs the last span of the bridge in sequence according to steps S1 to S7.

[0022] Step S9: After one segment is completed, the prestressed steel strands are installed in the construction body.

[0023] Step S10: After the previous segment is completed, construct the remaining segments.

[0024] Compared with the prior art, the present invention has the following technical advantages:

[0025] 1. By using an anti-symmetrical arrangement of external prestressed steel strands, the anchorage points of the steel strands are spatially staggered. The anchorage is achieved through variations in the vertical cable shape, ensuring an orderly staggering of the anchorage points. This eliminates the need for additional horizontal bends to meet the requirements for anchorage spacing and tension. The steel strands are arranged in a regular and compact manner, reducing the anchorage space requirement and improving the space utilization efficiency of the external prestressed steel strands.

[0026] 2. Due to the reduction of flat bending of steel strands, the spatial alignment of steel strands is simple, the prestress loss is small, and the steel strand alignment of each span is regularly arranged. Consequently, the changes and types of steering gear curves are reduced, thereby reducing material procurement costs and construction positioning difficulty.

[0027] 3. The cable strand alignment exhibits a consistent pattern across different bridge spans, with minimal variation in cable type. This ensures a predictable design alignment for the cable strands, improving cable adjustment efficiency. Furthermore, the uniform cable type pattern and minimal variation enhance construction visibility and improve overall construction efficiency.

[0028] 4. Pairs of steel strands are longitudinally staggered and arranged in an anti-symmetrical manner at the anchorage point. The anchorage beam is in a locally balanced and symmetrical state, with small additional internal forces, which optimizes local stress, reduces the amount of steel reinforcement, and improves economy. Attached Figure Description

[0029] Figure 1 Elevation layout of the steel strands for the side span of the segmental assembled box girder;

[0030] Figure 2 Elevation layout of the steel strands in the mid-span of the segmental assembled box girder;

[0031] Figure 3 A schematic diagram of the anti-symmetrical elevation of the crossbeams in a pair of steel strands;

[0032] Figure 4 This is a schematic diagram of the cross-section of a pair of steel strands;

[0033] Figure 5 This is a detailed schematic diagram of the side span cables (first and last spans);

[0034] Figure 6 This is a schematic diagram of the mid-span cable;

[0035] Figure 7 A schematic diagram of the two-span cable layout (middle span + middle span);

[0036] Figure 8 This is a schematic diagram of the two-span cable layout (side span + middle span).

[0037] The numbers on the map are:

[0038] 1-Box girder segment; 1a-Cast-in-place wet joint; 2-End crossbeam; 3-Middle crossbeam; 4-Tuning block; 5-Internal prestressed steel strand; 6-External prestressed steel strand; 7-Steel strand; 8-Anchorage; 9-Pier. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0040] It should be noted that all directional indicators (such as up, down, left, right, front, back, upper end, lower end, top, bottom, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0041] In this invention, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination should be considered non-existent and not within the scope of protection claimed by this invention.

[0043] An anti-symmetrical segmental prestressed continuous box girder external prestressing arrangement system includes a multi-span continuous segmental prestressed box girder; wherein: the segmental prestressed continuous box girder includes box girder segments, internal prestressed steel strands, external prestressed steel strands, steering blocks, middle crossbeams, and end crossbeams; the box girder segments are connected to each other as a whole to form a load-bearing structure through the prestressing action of the internal and external prestressed steel strands; the external prestressed steel strands are arranged in pairs in the transverse direction according to the structural spacing; the anchorage of the paired external prestressed steel strands at the middle crossbeams is staggered vertically; the external prestressed steel strands are positioned and steered by the steering blocks and the middle crossbeams or the end crossbeams. The structural stress is mainly due to external prestressing, and the amount of external prestressed steel strands accounts for more than 70% of the total amount of prestressed steel strands. During construction, the external prestressed steel strands are tensioned first, and after the structure forms a load-bearing system, the internal prestressed steel strands are tensioned. Externally prestressed steel strands are anchored to the crossbeam, and the cable shape is changed by pre-embedding steering gears on the crossbeam and steering blocks.

[0044] Specifically, in this embodiment, the paired external prestressed steel strands include front-hole paired steel strands and rear-hole paired steel strands; the front-hole paired steel strands and the rear-hole paired steel strands are arranged anti-symmetrically relative to the central crossbeam; the anchorage points of the front-hole paired steel strands on the central crossbeam are staggered vertically in opposite directions relative to the anchorage points of the rear-hole paired steel strands on the central crossbeam. The variation in the vertical cable shape of the steel strands resolves the conflict problem at the anchorage points. Simultaneously, the paired steel strands ensure symmetrical and balanced local forces at the crossbeam anchorage points.

[0045] Specifically, in this embodiment, the prestressed steel strands are divided into side span cables, middle span cables, and two-span cables. The side span cables and the middle span cables are single-span steel strands, arranged in different bridge spans, and anchored at the crossbeams at both ends of the bridge span where the steel strands are located. The two-span cables are divided into two types according to the position of the steel strands: side span + middle span two-span strands and middle span + middle span two-span strands. The two-span strands pass through the middle crossbeam and are anchored at the corresponding two-end crossbeams.

[0046] Specifically, in this embodiment, the paired mid-span cables are anti-symmetrical, the anchorage positions of the start and end points of a single steel strand are staggered, and the cable type of the steel strand from the start point to the end point is consistent with the cable type of the corresponding steel strand from the end point to the start point.

[0047] Specifically, in this embodiment, the side span cables are arranged in pairs, namely the first span cable and the last span cable, and the cable types of the first span cable and the last span cable are arranged in an anti-symmetrical manner relative to the middle crossbeam.

[0048] Specifically, in this embodiment, when the two-span cables are only arranged in the middle span, the cable types of the paired steel strands are arranged in an anti-symmetrical manner. If the two-span cables are arranged in the first span and the middle span, the cable types of the two-span cables and the corresponding middle span and the last span cables are arranged in an anti-symmetrical manner.

[0049] Specifically, in this embodiment, as the number of spans of the box girder increases, the steel strands are arranged in a regular anti-symmetric manner across different bridge spans.

[0050] Specifically, in this embodiment, a construction method for an external prestressed arrangement system for anti-symmetric segmental assembly continuous box girder includes the following steps:

[0051] Step S1: Complete the construction of the substructure foundation and pier body, and at the same time complete the prefabrication of box girder segments, pier top crossbeams, end crossbeams and middle crossbeams in the prefabrication plant; when prefabricating box girder segments, reserve prestressed steel strand ducts and pre-embedded steering gears according to the prestressing layout requirements.

[0052] Step S2: The bridge erecting machine is moved to the construction span, and the precast segments of the top sections of piers No. 0, No. 1 and No. 2, namely the end crossbeams and the middle crossbeams, are installed using the side pier brackets. After adjusting the position, the crossbeam concrete is poured to achieve the pier-beam consolidation.

[0053] Step S3: Transfer the outriggers of the bridge erecting machine to the top segment of the pier, feed the beams with the beam transport vehicle, hoist all the box girder segments in sequence, and adjust the alignment; apply epoxy resin between the box girder segments in sequence, and tension the temporary fastening device.

[0054] Step S4: Cast the wet joint next to the top segment of the pier, tension the external prestressed steel strands inside the box girder segment, and prepare the bridge erecting machine to move forward.

[0055] Step S5: The bridge erecting machine moves to the next span, installs the precast segment of the crossbeam at the top of pier No. 3, adjusts the position, and then pours the crossbeam concrete.

[0056] Step S6: Transfer the outriggers of the bridge erecting machine to the top segment of the pier, feed the beams with the beam transport vehicle, hoist all the box girder segments in sequence, and adjust the alignment; apply epoxy resin between the box girder segments in sequence, and tension the temporary fastening device.

[0057] Step S7: Cast the wet joint next to the top segment of the pier, tension the external prestressed steel strands inside the box girder segment, and prepare the bridge erecting machine to move forward.

[0058] Step S8: The bridge erecting machine moves forward and constructs the last span of the bridge in sequence according to steps S1 to S7.

[0059] Step S9: After one segment is completed, the prestressed steel strands are installed in the construction body.

[0060] Step S10: After the previous segment is completed, construct the remaining segments.

[0061] Example 1:

[0062] like Figure 1 , 2The anti-symmetric external prestressed arrangement system shown in the diagram comprises a box girder segment 1, internal prestressed steel strands 5, external prestressed steel strands 6, steering blocks 4, middle crossbeams 3, and end crossbeams 2. The box girder segments 1 are connected by the prestressing action of the prestressing strands to form a load-bearing structure.

[0063] In this embodiment, the prestressed steel strand system for segmental continuous box girders is divided into two types: internal prestressing and external prestressing. Among them, external prestressed steel strands account for a larger proportion, accounting for more than 70% of the total steel strand usage.

[0064] In this embodiment, the anchorage vertical directions of the paired external prestressed steel strands 6 at the middle crossbeam 3 are staggered. The paired steel strands with the front holes and the paired steel strands with the rear holes are arranged anti-symmetrically relative to the middle crossbeam. The anchorage points of the paired steel strands with the front holes on the middle crossbeam are staggered vertically in the opposite direction to the anchorage points of the paired steel strands with the rear holes on the middle crossbeam. Figures 3-4 As shown, the paired steel strands T1a and T1b in the front hole and the paired steel strands T2a and T2b in the rear hole are arranged in pairs. The anchorage points of T1a and T1b at the middle crossbeam are staggered vertically, while the anchorage points of T2a and T2b are staggered vertically in the opposite direction relative to T1a and T1b. Spatially, the paired steel strands T1a and T1b in the front hole and the paired steel strands T2a and T2b in the rear hole are arranged anti-symmetrically relative to the middle crossbeam, that is, the vertical bend of T1a is symmetrical to that of T2b, and the vertical bend of T1b is symmetrical to that of T2a. The lateral position of T1a corresponds to that of T2a, and the lateral position of T1b corresponds to that of T2b. Figure 3 The structure includes steel strands 7 and anchorages 8.

[0065] In this embodiment, the externally prestressed steel strands are classified into side span cables (TA type), mid span cables (TB type), and two span cables (TC type), and all steel strands are arranged in pairs. For example... Figures 5-8 As shown, the side span cable TA is divided into TAa and TAb, the middle span cable TB is divided into TBa and TBb, and the two span cables TC are divided into TCa and TCb, all arranged in pairs.

[0066] In this embodiment, the mid-span cable type is anti-symmetrical. For example... Figure 6 As shown, the cable shapes of TBa and TBb steel strands are anti-symmetrical; the anchorage positions of the start and end points of TBa and TBb steel strands are staggered vertically, and the cable shape of the TBa steel strand from the start point to the end point is the same as that of the TBb steel strand from the end point to the start point.

[0067] In this embodiment, the side span cable can be further divided into the first span cable and the tail span cable. Figure 5 The first span cables TAa and Tab, and their corresponding tail span cables, are antisymmetric relative to the centerline of the central crossbeam. This antisymmetric relationship between the first and tail span cables and the central crossbeam is similar to the arrangement of general steel strands in the front and rear holes, see [reference needed]. Figures 3-4 As shown.

[0068] In this embodiment, the two-span TC cable type combines the characteristics of both side-span and mid-span cables. Figure 7 and Figure 8 When TC is only arranged in the middle span, the cable types of the paired steel strands TCa and TCb are antisymmetric to each other. If the two spans of cables are arranged in the side and middle spans, the cable types of the two spans TCa and TCb are antisymmetric to the corresponding middle and tail span cables.

[0069] In this embodiment, when the number of spans of the box girder increases, i.e., when it is a multi-span continuous box girder, the vertical bending of the steel strands is arranged in a consistent and regular manner according to the antisymmetric method described above.

[0070] This invention also discloses a construction method for the segmental assembly of continuous box girders using the aforementioned antisymmetric external prestressing system, the method comprising the following steps:

[0071] 1. Complete the construction of the substructure foundation and pier 9. Simultaneously, complete the prefabrication of box girder segment 1, pier top crossbeam segment end crossbeam 2, and middle crossbeam 3 in the prefabrication plant. During the prefabrication of box girder segments, prestressed steel strand ducts and pre-embedded steering gears are reserved according to the prestressing layout requirements.

[0072] 2. The bridge erecting machine was moved to the construction span, and the precast segments of the top sections of piers 0, 1, and 2 (i.e., end crossbeam 2 and middle crossbeam 3) were installed using the pier-side brackets. After adjusting their positions, the crossbeam concrete was poured to achieve pier-beam consolidation. Because the pier-top crossbeam segments are solid structures with significant weight, hoisting is difficult. To reduce the weight of the crossbeams during hoisting, they were precast as hollow sections, and the concrete was poured after hoisting.

[0073] 3. Transfer the outriggers of the bridge erecting machine to the top segment of the pier, feed the beams with the beam transport vehicle, and hoist all box girder segments 1 in sequence, adjusting the alignment; apply epoxy resin between segments in sequence, and tension the temporary fastening devices.

[0074] 4. Casting the wet joint 1a next to the pier top segment, tensioning the external prestressed steel strands 6 inside the tensioned beam segment, and preparing the bridge erecting machine to move forward.

[0075] 5. The bridge erecting machine moves to the next span, installs the precast segment of the top crossbeam 3 of pier No. 3, adjusts the position, and then pours the crossbeam concrete.

[0076] 6. Transfer the outriggers of the bridge erecting machine to the top segment of the pier, feed the beams with the beam transport vehicle, and hoist all box girder segments 1 in sequence, adjusting the alignment; apply epoxy resin between segments in sequence, and tension the temporary fastening devices.

[0077] 7. Casting wet joints next to the pier top segment, tensioning external prestressed steel strands 6 inside the tensioned beam segment, and preparing the bridge erecting machine to move forward.

[0078] 8. The bridge erecting machine moves forward and continues construction in the above steps until the last span of this connecting bridge.

[0079] 9. After one segment is completed, the prestressed steel strands 5 are installed in the construction body.

[0080] 10. After the previous segment is completed, proceed with the construction of the remaining segments.

[0081] Compared with existing technologies, this invention provides an anti-symmetric segmental assembly continuous box girder external prestressing arrangement system and its construction method. External prestressing tendons are arranged anti-symmetrically at the central crossbeam position, and the tendon alignment is set according to the anti-symmetric principle, optimizing the spatial cable shape of the tendons, making the tendons compact and regular, improving the space utilization efficiency of external prestressing, and reducing design and construction difficulty. This invention has the following beneficial effects:

[0082] 1. By using an anti-symmetrical arrangement of external prestressed steel strands, the anchorage points of the steel strands are spatially staggered. The anchorage is achieved through variations in the vertical cable shape, ensuring an orderly staggering of the anchorage points. This eliminates the need for additional horizontal bends to meet the requirements for anchorage spacing and tension. The steel strands are arranged in a regular and compact manner, reducing the anchorage space requirement and improving the space utilization efficiency of the external prestressed steel strands.

[0083] 2. Due to the reduction of flat bending of steel strands, the spatial alignment of steel strands is simple, the prestress loss is small, and the steel strand alignment of each span is regularly arranged. Consequently, the changes and types of steering gear curves are reduced, thereby reducing material procurement costs and construction positioning difficulty.

[0084] 3. The cable strand alignment exhibits a consistent pattern across different bridge spans, with minimal variation in cable type. This ensures a predictable design alignment for the cable strands, improving cable adjustment efficiency. Furthermore, the uniform cable type pattern and minimal variation enhance construction visibility and improve overall construction efficiency.

[0085] 4. Pairs of steel strands are longitudinally staggered and arranged in an anti-symmetrical manner at the anchorage point. The anchorage beam is in a locally balanced and symmetrical state, with small additional internal forces, which optimizes local stress, reduces the amount of steel reinforcement, and improves economy.

[0086] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An anti-symmetric segmental assembly continuous box girder external prestressing arrangement system, comprising a multi-span continuous segmental assembly continuous box girder; characterized in that: The segmental assembled continuous box girder includes box girder segments, internal prestressed steel strands, external prestressed steel strands, steering blocks, middle crossbeams, and end crossbeams. The box girder segments are connected as a whole to form a load-bearing structure by the prestressing action of the internal and external prestressed steel strands. The external prestressed steel strands are arranged in pairs in the transverse direction according to the structural spacing. The anchorage of the pairs of external prestressed steel strands at the middle crossbeams is staggered vertically. The external prestressed steel strands are positioned and steered by the steering blocks and the middle crossbeams or the end crossbeams. The paired external prestressed steel strands include front hole paired steel strands and rear hole paired steel strands; the front hole paired steel strands and the rear hole paired steel strands are arranged anti-symmetrically with respect to the middle crossbeam; the anchorage points of the front hole paired steel strands on the middle crossbeam are staggered vertically in opposite directions with respect to the anchorage points of the rear hole paired steel strands on the middle crossbeam. The prestressed steel strands in the body are divided into side span cables, middle span cables, and two-span cables; the side span cables and the middle span cables are single-span steel strands, arranged in different bridge spans, and anchored at the crossbeams at both ends of the bridge span where the steel strands are located; the two-span cables are divided into two types according to the position of the steel strands: side span + middle span two-span strands and middle span + middle span two-span strands, with the two-span strands passing through the middle crossbeam and anchored at the corresponding two-end crossbeams; The paired mid-span cable vertical bends are anti-symmetrical to each other, and the anchorage positions of the start and end points of a single steel strand are staggered vertically. The cable type of the steel strand from the start point to the end point is consistent with the cable type of the corresponding steel strand from the end point to the start point. The side span cables are arranged in pairs, divided into first span cables and last span cables. The cable types of the first span cables and last span cables are arranged in an anti-symmetrical manner relative to the middle crossbeam. When the two-span cables are only arranged in the middle span, the cable types of the paired steel strands are arranged in an anti-symmetrical manner. If the two-span cables are arranged in the first span and the middle span, the cable types of the two-span cables and the corresponding middle span and the last span are arranged in an anti-symmetrical manner.

2. The anti-symmetric segmental assembly continuous box girder external prestressing arrangement system according to claim 1, characterized in that: As the number of spans of the box girder increases, the steel strands are arranged in a regular anti-symmetric manner across different bridge spans.

3. A construction method employing the anti-symmetric segmental assembly continuous box girder external prestressing arrangement system as described in claim 1 or 2, characterized in that, Includes the following steps: Step S1: Complete the construction of the substructure foundation and pier body, and at the same time complete the prefabrication of box girder segments, pier top crossbeams, end crossbeams and middle crossbeams in the prefabrication plant; when prefabricating box girder segments, reserve prestressed steel strand ducts and pre-embedded steering gears according to the prestressing layout requirements. Step S2: The bridge erecting machine is moved to the construction span, and the precast segments of the top sections of piers No. 0, No. 1 and No. 2, namely the end crossbeams and the middle crossbeams, are installed using the side pier brackets. After adjusting the position, the crossbeam concrete is poured to achieve the pier-beam consolidation. Step S3: Transfer the outriggers of the bridge erecting machine to the top segment of the pier, feed the beams with the beam transport vehicle, hoist all the box girder segments in sequence, and adjust the alignment; apply epoxy resin between the box girder segments in sequence, and tension the temporary fastening device. Step S4: Cast the wet joint next to the top segment of the pier, tension the external prestressed steel strands inside the box girder segment, and prepare the bridge erecting machine to move forward. Step S5: The bridge erecting machine moves to the next span, installs the precast segment of the crossbeam at the top of pier No. 3, adjusts the position, and then pours the crossbeam concrete. Step S6: Transfer the outriggers of the bridge erecting machine to the top segment of the pier, feed the beams with the beam transport vehicle, hoist all the box girder segments in sequence, and adjust the alignment; apply epoxy resin between the box girder segments in sequence, and tension the temporary fastening device. Step S7: Cast the wet joint next to the top segment of the pier, tension the external prestressed steel strands inside the box girder segment, and prepare the bridge erecting machine to move forward. Step S8: The bridge erecting machine moves forward and constructs the last span of the bridge in sequence according to steps S1 to S7. Step S9: After one segment is completed, the prestressed steel strands are installed in the construction body. Step S10: After the previous segment is completed, construct the remaining segments.

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