A construction method and anchoring system for cantilever casting of asymmetric continuous box beam

Abstract

The invention discloses a construction method and anchoring system for cantilever casting of an asymmetric continuous box girder, including completing the construction of a rotating main pier and a secondary main pier in sequence according to a calculated design scheme, and constructing a lower anchoring structure in underground rocks; after completing the rotation of the bridge and the construction of the symmetrical section of the middle span, the casting of the middle span joint section is completed, and the hanging basket on the middle span close to the side span is retained; the upper anchoring structure is constructed for the box girder on the middle span close to one end of the middle span joint section, and the upper anchoring structure is connected with the lower anchoring structure to form a weight for the middle span box girder; according to monitoring instructions, the steel strand tensioning of each section in the asymmetric cantilever casting section is gradually completed through the upper anchoring structure; after completion, the side span joint section is cast and the steel strand is released. The invention reduces the length of the side span cast-in-place beam, adopts an eight-shaped friction pile with a high safety redundancy coefficient for anti-overturning, realizes the function of the prestressed steel strand to continuously and accurately adjust the balancing torque, and ensures that the stress of each section box girder is in the optimal state.

Description

Technical Field

[0001] The present invention relates to the field of bridge construction, and more specifically, to a construction method and anchoring system for cantilever casting of an asymmetric continuous box girder. Background Art

[0002] When the bridge across the high-speed railway line is rotated into place and the middle span is closed, in order to avoid the railway below, the middle span closure is as close to the secondary main pier as possible, resulting in a short T-structure cantilever length of the secondary main pier, a long cast-in-place length of the side span, and a large amount of side span brackets. At this time, counterweights are generally added to the middle span, and then asymmetric cantilever casting is performed on the side span to reduce the length of the side span bracket. Since the counterweight is a gravity effect, once there is a tendency to overturn toward the middle of the span, the counterweight will have a counter-effect, and the risk of uncontrollability is high; at the same time, the counterweight method is not conducive to adjusting the internal stress of the box girder.

[0003] There are generally two ways to deal with the unbalanced load of continuous beams.

[0004] 1. When pouring asymmetric continuous beams or joint sections, counterweights are used for balance, usually water tanks or precast concrete blocks. Water tank counterweights are usually used in joint construction. During the pouring of concrete at the joint mouth, waterproofing is continuously carried out to achieve a balance with the increase and decrease of the weight of the newly added concrete. During the unbalanced pouring of continuous beams, it is necessary to add weight during the pouring process, but it is inconvenient to inject water, so precast concrete blocks are generally used for counterweights. In this process, since the counterweight is the effect of gravity, once there is a tendency to overturn toward the middle of the span, the counterweight will have a counter-effect, and the risk of uncontrollable is high.

[0005] Second, in the symmetrical pouring construction of continuous beams, it is generally adopted to embed steel strands on the top of the pier or set anchor steel pipe piles to resist some unforeseen unbalanced moments during the symmetrical pouring process. However, this process is generally only used for small unbalanced loads in symmetrical cantilever pouring construction, and it is difficult to withstand the super-large unbalanced moments in the unbalanced cantilever pouring process. Summary of the invention

[0006] The purpose of the present invention is to provide a construction method and anchoring system for cantilever casting of an asymmetric continuous box girder, which reduces the length of the cast-in-place beam of the side span, adopts an eight-shaped friction pile with a high safety redundancy coefficient for anti-overturning, realizes the function of prestressed steel strands to continuously and accurately adjust the balancing torque, and ensures that the stress of each segment box girder is in an optimal state.

[0007] The technical solution adopted by the present invention to solve this technical problem is: to provide a construction method for cantilever casting of an asymmetric continuous box beam, comprising the following steps:

[0008] Step 1: According to the calculated design plan, the construction of the rotating main pier and the secondary main pier is completed in sequence, and the lower anchoring structure of the anchoring system is constructed in the underground rock next to the secondary main pier;

[0009] Step 2: After the bridge is rotated into place and the construction of the symmetrical section of the middle span is completed, the pouring of the joint section of the middle span is completed, and the hanging basket close to the side span on the symmetrical section of the middle span is retained;

[0010] Step 3: construct the upper anchorage structure of the anchorage system for the box girder at one end of the middle span symmetrical section close to the middle span joint section, and connect the upper anchorage structure with the lower anchorage structure through a steel strand connector to form a weight for the middle span box girder;

[0011] Step 4: Carry out segmental construction of the asymmetric suspended cast-in-place section. According to the monitoring instructions, the steel strand tensioning of each segment is gradually completed through the upper anchor structure. The farther the steel strand is from the secondary main pier, the greater the tensioning force.

[0012] Step 5: After completing the pouring of the asymmetric suspended section and the side span joint section, release the steel strands.

[0013] Preferably, in the construction method of cantilever casting of asymmetric continuous box beam, in step 1, the lower anchor structure includes friction piles, anchor bodies, fixed anchors and embedded steel strands, and the construction of the lower anchor structure includes the following steps:

[0014] S1: insert the friction piles symmetrically and obliquely into the underground rock in pairs, set anchor bodies at the tops of the friction piles, and arrange steel cages around the friction piles and anchor bodies;

[0015] S2: pre-embed the fixed anchor in the anchor body at the anchoring position of the steel strand, one end of the pre-embedded steel strand is connected to the fixed anchor, and the other end is exposed from the top of the anchor body;

[0016] S3: Pour concrete for friction piles and anchor bodies and complete the setting of embedded steel strands.

[0017] Preferably, in the construction method of cantilever casting of an asymmetric continuous box girder, in step S2, the anchoring positions of the steel strands are arranged to be evenly arranged along the direction of the bridge according to the bridge segments, and to be arranged left and right along the transverse direction of the bridge.

[0018] Preferably, in the construction method of cantilever casting of the asymmetric continuous box girder, in the step 3, the upper anchoring structure includes a tool anchor, a through-hole jack, a working anchor, a concrete tooth block and an anchoring steel strand, and the specific construction of the step 3 includes the following steps:

[0019] S1: Pour concrete tooth blocks at the anchorage points of the middle span box girder web to level them, and reserve steel strand pipes in the box girder bottom plate and concrete tooth blocks;

[0020] S2: Pass the anchor steel strand through the steel strand pipe, and install a working anchor, a through-hole jack and a tool anchor on the outer shell of the anchor steel strand above the concrete tooth block in sequence;

[0021] S3: Connect the anchoring steel strand and the embedded steel strand through the steel strand connector, and tighten the steel strand using the through-hole jack.

[0022] Preferably, in the construction method of cantilever casting of an asymmetric continuous box girder, in step 4, the tensioning force of the steel strands during the construction of each section of the asymmetric cantilever casting section is increased sequentially.

[0023] The present invention also provides an anchoring system for implementing the above-mentioned construction method of cantilever casting of asymmetric continuous box beams, comprising: an upper anchoring structure arranged on the box beam and a lower anchoring structure arranged on underground rocks, wherein the upper anchoring structure comprises a concrete tooth block, a tool anchor, a through-hole jack, a working anchor and an anchoring steel strand, and the lower anchoring structure comprises a friction pile, an anchor body, a fixed anchor and a pre-buried steel strand;

[0024] Several of the friction piles are inserted into the underground rock symmetrically and tilted in pairs, so that every two symmetrically and tilted friction piles together form an eight-shaped structure, the anchor body is arranged above the friction pile, and several of the fixed anchors are arranged in the anchor body, one end of the embedded steel strand is connected to the fixed anchor, and the other end is exposed from the top of the anchor body, and several of the concrete tooth blocks are arranged on the web of the box beam, and steel strand pipes are reserved in the bottom plate of the box beam and the concrete tooth blocks. The anchoring steel strand passes through the steel strand pipe, and a working anchor, a through-hole jack and a tool anchor are arranged in sequence above the concrete tooth block, and the lower end of the anchoring steel strand is connected to the embedded steel strand through a steel strand connector.

[0025] Preferably, in the anchoring system, every two symmetrically inclined friction piles form a group, and there are 5 groups arranged in parallel along the direction of the bridge.

[0026] Preferably, in the anchoring system, the fixed anchors are arranged in a group of two on the left and right sides along the transverse direction of the bridge, and a total of four groups are arranged in parallel along the direction of the bridge.

[0027] Preferably, in the anchoring system, a limit plate is provided on the tool anchor, and the limit plate is sleeved outside the anchoring steel strand.

[0028] The present invention has at least the following beneficial effects:

[0029] 1. Under the construction condition that the continuous beam bridge is affected by the obstacle structure, the present invention solves the problem of asymmetric cantilever casting of the continuous beam bridge, reduces the length of the side span cast-in-place beam, saves the support construction cost, and reduces the risk of high-altitude support operation.

[0030] 2. The present invention realizes the function of continuous and precise adjustment of the balancing torque of the prestressed steel strands, ensuring that the stress of each segment box girder is in an optimal state, and to a great extent ensuring the bridge line shape and bridge stress of the continuous beam.

[0031] 3. The anti-overturning safety redundancy coefficient in the present invention is high. Since the rock anchor adopts an "eight"-shaped friction inclined pile, it can provide sufficient passive tension when the continuous beam is about to overturn, which is essentially different from the counterweight (gravity type) balance.

[0032] 4. The rock anchor in the present invention can be installed in advance, which is convenient for construction, saves construction time and improves construction efficiency.

[0033] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a construction schematic diagram of step 1 in a construction method for cantilever casting of an asymmetric continuous box girder in the present invention;

[0035] Figure 2 It is a construction schematic diagram of step 2 and step 3 in a construction method for cantilever casting of an asymmetric continuous box girder in the present invention;

[0036] Figure 3 It is a construction schematic diagram of the first section in step 4 of a construction method for cantilever casting of an asymmetric continuous box girder in the present invention;

[0037] Figure 4 It is a construction schematic diagram of the second section in step 4 of a construction method for cantilever casting of an asymmetric continuous box girder in the present invention;

[0038] Figure 5 It is a construction schematic diagram of step 5 in a construction method for cantilever casting of an asymmetric continuous box girder in the present invention;

[0039] Figure 6 It is a side view of a cantilever casting anchoring system of an asymmetric continuous box girder in the present invention;

[0040] Figure 7 It is a structural diagram of an upper anchoring structure in a cantilever casting anchoring system of an asymmetric continuous box girder in the present invention;

[0041] Figure 8 A structural diagram of a steel strand in a cantilever casting anchoring system of an asymmetric continuous box girder in the present invention;

[0042] Description of reference numerals: 1. rotating main pier, 2. secondary main pier, 3. lower anchorage structure, 31. friction pile, 32. anchor body, 33. fixed anchor, 34. embedded steel strand, 4. middle span symmetrical section, 5. middle span joint section, 6. hanging basket, 7. Steel strand, 71. The first group of steel strand, 72. The second group of steel strand, 73. The third group of steel strand, 74. The fourth group of steel strand, 8. The first segment, 9. The second segment, 10. Asymmetric suspended cast-in-place segment, 11. Side span joint segment, 12. Box girder, 13. Underground rock, 14. Upper anchoring structure, 141. Tool anchor, 142. Through-core jack, 143. Working anchor, 144. Concrete tooth block, 145. Anchor steel strand, 146. Steel strand pipeline, 147. Limit plate, 15. Box girder web, 16. Box girder bottom plate, 17. Steel strand connector. DETAILED DESCRIPTION

[0043] The present invention is described in detail and completely below in conjunction with the accompanying drawings. A person of ordinary skill in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly pointed out that the technical solutions and technical features provided in each part of the present invention, including the following description, can be combined with each other without conflict.

[0044] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0045] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, and its specific implementation process is as follows:

[0046] like Figure 1-5 As shown, the present invention provides a construction method for cantilever casting of an asymmetric continuous box girder, comprising the following steps:

[0047] Step 1: According to the calculated design plan, the construction of the rotating main pier 1 and the secondary main pier 2 is completed in sequence, and the lower anchoring structure 3 of the anchoring system is constructed in the underground rock 13 next to the secondary main pier 2; in this embodiment, a preferred solution is that the design plan can be calculated and analyzed in advance by the monitoring unit, and construction can be carried out after it is qualified.

[0048] Step 2: After the bridge is rotated into place and the construction of the middle span symmetrical section 4 is completed, the casting of the middle span joint section 5 is completed, and the hanging basket 6 on the middle span symmetrical section 4 close to the side span is retained, and the hanging basket close to the middle span joint section 5 is removed;

[0049] Step 3: construct the upper anchoring structure 14 of the anchoring system for the box girder 12 at one end of the middle span symmetrical section 4 close to the middle span joint section 5, and connect the upper anchoring structure 14 with the lower anchoring structure 15 through the steel strand connector 17 to form a weight for the middle span box girder 12;

[0050] Step 4: Perform segmented construction of the asymmetric suspended casting section 10. According to the monitoring instructions, the upper anchor structure 14 gradually completes the tensioning of the steel strands 7 of each segment. The farther the steel strands 7 are from the secondary main pier 2, the greater the tensioning force. In this embodiment, a preferred implementation scheme is that the steel strands 7 are composed of anchored steel strands 145 in the upper anchor structure 14 and embedded steel strands 34 in the lower anchor structure 3 connected by steel strand connectors 17. By adjusting the stress of the steel strands 7 during the continuous suspended casting process, the stress of the mid-span box girder 12 is adjusted to ensure structural safety.

[0051] Step 5: After the asymmetric suspended casting section 10 and the side span closure section 11 are cast, the steel strands 7 are released. The upper anchor structure 14 and the lower anchor structure 3 do not need to be removed.

[0052] Furthermore, in the construction method of cantilever casting of the asymmetric continuous box girder, in the step 1, the lower anchor structure 3 includes a friction pile 31, an anchor body 32, a fixed anchor 33 and a pre-buried steel strand 34, and the construction of the lower anchor structure 3 includes the following steps:

[0053] S1: insert the friction piles 31 symmetrically and obliquely into the underground rock 13 in pairs, set the anchor body 32 at the top of the friction pile 31, and arrange steel cages around the friction pile 31 and the anchor body 32; in this embodiment, since the rock anchor adopts the "eight"-shaped friction pile 31, it can provide sufficient passive tension when the continuous beam is about to overturn.

[0054] S2: pre-embed the fixed anchor 33 at the anchoring position of the steel strand in the anchor body 32, one end of the pre-embedded steel strand 34 is connected to the fixed anchor 33, and the other end is exposed from the top of the anchor body 32;

[0055] S3: Concrete pouring of the friction pile 31 and the anchor body 32 is performed to complete the installation of the embedded steel strand 34.

[0056] Furthermore, in the construction method of cantilever casting of asymmetric continuous box beam, in step S2, the anchoring positions of the steel strands are arranged evenly along the bridge direction according to the bridge segments, and are arranged left and right along the bridge transverse direction. By continuously arranging the steel strands 7 along the segments, the anchoring system can better adapt to the deformation and stress changes of the box beam 12 during the asymmetric casting process.

[0057] Furthermore, in the construction method of cantilever casting of the asymmetric continuous box girder, in the step three, the upper anchoring structure 14 includes a tool anchor 141, a through-hole jack 142, a working anchor 143, a concrete tooth block 144 and an anchoring steel strand 145, and the specific construction of the step three includes the following steps:

[0058] S1: Cast concrete tooth blocks 144 at the anchor points of the middle span box girder web 15 to level them, and reserve steel strand pipes 146 in the box girder bottom plate 16 and the concrete tooth blocks 144;

[0059] S2: Pass the anchoring steel strand 145 through the steel strand pipe 146, and install the working anchor 143, the through-hole jack 142 and the tool anchor 141 on the outer shell of the anchoring steel strand 145 above the concrete tooth block 144 in sequence;

[0060] S3: Connect the anchoring steel strand 145 to the embedded steel strand 34 through the steel strand connector 17, tighten the steel strand 7 through the through-core jack 142, and tension or relax it according to the measured data. The through-core jack 142 can adjust the stress at any time according to the monitoring data, so that the anchoring force can be adjusted flexibly during the construction process.

[0061] Furthermore, in the construction method of cantilever casting of the asymmetric continuous box girder, in the step 4, the tension of the steel strands 7 during the construction of each section of the asymmetric cantilever casting section 10 is increased successively. In this embodiment, a preferred implementation scheme is that during the casting of the first section 8, according to the monitoring instructions, the first group of steel strands 71 ​​are gradually tensioned to 10% of the controlled prestress, the second group of steel strands 72 are tensioned to 8% of the controlled prestress, the third group of steel strands 73 are tensioned to 6% of the controlled prestress, and the fourth group of steel strands 74 are tensioned to 4% of the controlled prestress, and the farther the steel strands 7 are from the secondary main pier 2, the greater the tension of the steel strands 7;

[0062] During the pouring of the second section 9, according to the monitoring instructions, the first group of steel strands 71 ​​are gradually tensioned to 14% of the controlled prestress, the second group of steel strands 72 are tensioned to 12% of the controlled prestress, the third group of steel strands 73 are tensioned to 10% of the controlled prestress, and the fourth group of steel strands 74 are tensioned to 8% of the controlled prestress.

[0063] Repeat the above steps until the asymmetric suspended casting section 10 is cast.

[0064] like Figure 6-8As shown, the present invention also provides an anchoring system for implementing the above-mentioned construction method of cantilever casting of asymmetric continuous box beams, comprising: an upper anchoring structure 14 arranged on the box beam 12 and a lower anchoring structure 3 arranged on the underground rock 13, wherein the upper anchoring structure 14 comprises a concrete tooth block 144, a tool anchor 141, a through-core jack 142, a working anchor 143 and an anchoring steel strand 145, and the lower anchoring structure 3 comprises a friction pile 31, an anchor body 32, a fixed anchor 33 and a pre-buried steel strand 34;

[0065] A plurality of the friction piles 31 are inserted into the underground rock 13 symmetrically and tilted in pairs, so that every two symmetrically and tilted friction piles 31 together form an eight-shaped structure, an anchor body 32 is arranged above the friction pile 31, a plurality of the fixed anchors 33 are arranged in the anchor body 32, one end of the embedded steel strand 34 is connected to the fixed anchor 33, and the other end is exposed from the top of the anchor body 32, a plurality of the concrete tooth blocks 144 are arranged at the box beam web 15, a steel strand pipe 146 is reserved in the box beam bottom plate 16 and the concrete tooth block 144, and the anchoring steel strand 145 passes through the steel strand pipe 146, and a working anchor 143, a through-hole jack 142 and a tool anchor 141 are arranged in sequence above the concrete tooth block 144, and the lower end of the anchoring steel strand 145 is connected to the embedded steel strand 34 through a steel strand connector 17.

[0066] Furthermore, in the anchoring system, every two symmetrically inclined friction piles 31 form a group, and there are 5 groups arranged in parallel along the direction of the bridge.

[0067] Furthermore, in the anchoring system, the fixed anchors 33 are arranged in a group of two on the left and right sides along the transverse direction of the bridge, and a total of four groups are arranged in parallel along the direction of the bridge.

[0068] Furthermore, in the anchoring system, a limit plate 147 is provided on the tool anchor 141 , and the limit plate 147 is sleeved outside the anchoring steel strand 145 , and the limit plate 147 is used to control the clip in the tool anchor 141 to fall out.

[0069] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A construction method for cantilever casting of an asymmetric continuous box girder, characterized in that: The steps include: Step 1: According to the calculated design plan, the construction of the rotating main pier and the secondary main pier is completed in sequence, and the lower anchoring structure of the anchoring system is constructed in the underground rock next to the secondary main pier; Step 2: After the bridge is rotated into place and the construction of the symmetrical section of the middle span is completed, the pouring of the joint section of the middle span is completed, and the hanging basket close to the side span on the symmetrical section of the middle span is retained; Step 3: construct the upper anchorage structure of the anchorage system for the box girder at one end of the middle span symmetrical section close to the middle span joint section, and connect the upper anchorage structure with the lower anchorage structure through a steel strand connector to form a weight for the middle span box girder; Step 4: Carry out segmental construction of the asymmetric suspended cast-in-place section. According to the monitoring instructions, the steel strand tensioning of each segment is gradually completed through the upper anchor structure. The farther the steel strand is from the secondary main pier, the greater the tensioning force. Step 5: After the asymmetric suspended section and the side span closure section are cast, release the steel strands; In the step 1, the lower anchor structure includes a friction pile, an anchor body, a fixed anchor and a pre-buried steel strand, and the construction of the lower anchor structure includes the following steps: S1: insert the friction piles symmetrically and obliquely into the underground rock in pairs, set anchor bodies at the top of the friction piles, and arrange steel cages around the friction piles and the anchor bodies; S2: pre-embed the fixed anchor in the anchor body at the anchoring position of the steel strand, one end of the pre-embedded steel strand is connected to the fixed anchor, and the other end is exposed from the top of the anchor body; S3: Concrete pouring of friction piles and anchor bodies is carried out to complete the setting of pre-buried steel strands; In step 3, the upper anchoring structure includes a tool anchor, a through-hole jack, a working anchor, a concrete tooth block and an anchoring steel strand. The specific construction of step 3 includes the following steps: S1: Pour concrete tooth blocks at the anchorage points of the middle span box girder web to level them, and reserve steel strand pipes in the box girder bottom plate and concrete tooth blocks; S2: Pass the anchor steel strand through the steel strand pipe, and install a working anchor, a through-hole jack and a tool anchor on the outer shell of the anchor steel strand above the concrete tooth block in sequence; S3: Connect the anchoring steel strand and the embedded steel strand through the steel strand connector, and tighten the steel strand using the through-hole jack.

2. The construction method for cantilever casting of an asymmetric continuous box beam according to claim 1, characterized in that: In step S2 of step one, the anchoring positions of the steel strands are arranged to be evenly arranged along the direction of the bridge according to the bridge segments, and to be arranged left and right along the transverse direction of the bridge.

3. The construction method for cantilever casting of an asymmetric continuous box beam according to claim 1, characterized in that: In the step 4, the tensioning force of the steel strands during the construction of each section of the asymmetric suspended casting section is increased successively.

4. Anchoring system, characterized in that, A construction method for cantilever casting of an asymmetric continuous box girder as claimed in any one of claims 1 to 3, comprising: an upper anchoring structure arranged on the box girder and a lower anchoring structure arranged on underground rock, wherein the upper anchoring structure comprises a concrete tooth block, a tool anchor, a through-hole jack, a working anchor and an anchoring steel strand, and the lower anchoring structure comprises a friction pile, an anchor body, a fixed anchor and a pre-buried steel strand; Several of the friction piles are inserted into the underground rock symmetrically and tilted in pairs, so that every two symmetrically and tilted friction piles together form an eight-shaped structure, the anchor body is arranged above the friction pile, and several of the fixed anchors are arranged in the anchor body, one end of the embedded steel strand is connected to the fixed anchor, and the other end is exposed from the top of the anchor body, and several of the concrete tooth blocks are arranged on the web of the box beam, and steel strand pipes are reserved in the bottom plate of the box beam and the concrete tooth blocks. The anchoring steel strand passes through the steel strand pipe, and a working anchor, a through-hole jack and a tool anchor are arranged in sequence above the concrete tooth block, and the lower end of the anchoring steel strand is connected to the embedded steel strand through a steel strand connector.

5. The anchoring system according to claim 4, characterized in that: Every two symmetrically inclined friction piles form a group, and there are 5 groups arranged in parallel along the direction of the bridge.

6. The anchoring system according to claim 4, characterized in that: The fixed anchors are arranged in a group of two on the left and right sides along the transverse direction of the bridge, and a total of four groups are arranged in parallel along the direction of the bridge.

7. The anchoring system according to claim 4, characterized in that: A limit plate is arranged on the tool anchor, and the limit plate is sleeved outside the anchoring steel strand.

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