Semi-prefabricated segment assembly large cantilever prestressed concrete cover beam and construction method

Abstract

The invention discloses a semi-prefabricated segment assembled large cantilever prestressed concrete cover beam and a construction method, the semi-prefabricated segment assembled large cantilever prestressed concrete cover beam comprises a shell prefabricated part, a main beam prefabricated part and an ultra-high performance concrete connecting layer, the shell prefabricated part is formed by assembling three segments, and the main beam prefabricated part is formed by assembling three segments; splicing seams of the three sections of main beam prefabricated parts and splicing seams of the three sections of shell prefabricated parts are arranged in a staggered mode, corrugated pipes are arranged in the spliced main beam prefabricated parts, and prestressed steel strands penetrate through the corrugated pipes; an ultra-high-performance concrete connecting layer is formed in a cavity between the shell prefabricated part and the main beam prefabricated part through cast-in-place construction, and a steel reinforcement framework is further arranged in the ultra-high-performance concrete connecting layer. The structure is simple, the design is reasonable, the construction is convenient, and the comprehensive economic benefit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of precast segment assembly construction of bridges, and particularly relates to a semi-precast segment assembled large cantilever prestressed concrete capping beam and a construction method thereof. Background Art

[0002] With the development of China's transportation industry, large-scale ring roads mainly adopt viaduct construction technology to form leapfrog municipal roads. On the premise of ensuring sufficient driving width on the viaduct and large space and good visibility under the bridge, the concept of "large cantilever prestressed capping beam" emerges as the times require. The capping beams of urban viaduct bridges are relatively large in size. If the construction method of pouring concrete entirely on-site is adopted, formwork support and in-situ casting are required, which also face disadvantages such as long traffic interruption, large amount of high-altitude operations, and long construction period. If an integral precast scheme is adopted, the self-weight of the precast capping beam is very large, which requires high requirements for lifting equipment and transportation machinery and has poor construction adaptability. Therefore, for the large cantilever prestressed concrete capping beam structure, the technology of segmentally precasting and assembling prestressed concrete capping beams is an effective solution to solve the problems of transportation and hoisting of integrally cast-in-place capping beams and has been successfully applied in many engineering projects. However, the design of the large cantilever prestressed concrete capping beam structure faces key problems such as precast and assembled segment division, segment connection, and connection between segments and piers. It is necessary to combine the actual engineering situation to ensure the rationality and feasibility of the design. At the same time, since the longitudinal reinforcement of the segmentally precast and assembled capping beam is truncated, it may lead to discontinuous force transmission, and the joint is prone to water seepage, which is the key to affecting the mechanical properties of the segmentally precast capping beam.

[0003] For example, Chinese patent document CN202321099700.1, a segmentally precast and assembled capping beam, includes an intermediate segment placed at the upper end of a pier column and cantilever segments spliced with the left and right ends of the intermediate segment. The U-shaped stirrups of the pier column pass through the wire grooves of the intermediate segment for positioning, and the fixed steel pipes at both ends of the cantilever segments horizontally pass through the U-shaped stirrups until they are inserted into the fixed holes of the intermediate segment, so that the precast pier column, intermediate segment, and cantilever segments are assembled together. The convenience of hoisting and installation is achieved by dividing it into three segments. However, the overall mechanical properties of this technology are not good, especially the three segments cannot form a complete whole. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a semi-precast segment assembled large cantilever prestressed concrete capping beam and a construction method thereof, which can greatly reduce the quantity and engineering volume of the construction supports and formworks of the integrally cast-in-place concrete capping beam, and avoid the adverse effects brought by the weak mechanical properties at the segment joints of the integrally precast segment assembled capping beam.

[0005] To solve the above technical problems, the technical solution of the present invention is: A semi-precast segment assembled large-cantilever prestressed concrete cap beam, characterized in that: it includes an outer shell precast member, a main beam precast member and an ultra-high performance concrete connection layer. Among them, the outer shell precast member is composed of three segments assembled, and mechanical connection and anti-leakage grouting are carried out at the splicing joints of adjacent two segments of the outer shell precast member. The outer shell precast member is a reinforced concrete precast member with a U-shaped cross-section, and the outer shell precast member is placed on the top of the pier. Shear keys are arranged on the inner surface of the outer shell precast member and are roughened; the main beam precast member is composed of three segments assembled, and the splicing joints of the three segments of the main beam precast member are staggered from the splicing joints of the three segments of the outer shell precast member, and there are corrugated pipes in the assembled main beam precast member. By threading prestressed steel strand bundles in the corrugated pipes, the three segments of the main beam precast member are formed into one body under the tension of the prestressed steel strand bundles; shear keys or / and roughened surfaces are arranged on the surface of the outer shell precast member or / and the main beam precast member; and an ultra-high performance concrete connection layer is formed by in-situ construction in the cavity between the outer shell precast member and the main beam precast member, and a steel reinforcement cage is also arranged in the ultra-high performance concrete connection layer.

[0006] Reinforcement perforations for connecting with the main reinforcement of the pier are arranged on the outer shell precast member or / and the main beam precast member, and welded connection or grouting connection is carried out.

[0007] The mechanical connection of adjacent main reinforcements at the splicing joint of two segments of the outer shell precast member is completed through steel reinforcement sleeves.

[0008] The steel reinforcement cage and the shear keys are auxiliarily fixed by welding or tying.

[0009] A stepped concave-convex fit is arranged at the splicing surface of the main beam precast member.

[0010] The corrugated pipes between adjacent main beam precast members are connected by socket connection.

[0011] The cross-section of the ultra-high performance concrete connection layer is a square shape surrounded by four sides or a U-shaped surrounded by three sides.

[0012] A construction method for a semi-precast segment assembled large-cantilever prestressed concrete cap beam, characterized by including the following steps: (1) According to the specific dimensions of the cap beam and the layout of the prestressed steel strand bundles, the cap beam drawing is disassembled to form precast drawings of the outer shell precast member and the main beam precast member; (2) Precast the outer shell precast member and the main beam precast member in the precast yard; (3) Set up temporary supports, and complete the hoisting of the three segments of the outer shell precast member, so that the three segments of the outer shell precast member are placed on the pier and the temporary supports, use steel reinforcement sleeves to mechanically connect the three segments of the outer shell precast member, and use joint mortar or joint rubber strips for joint filling.

[0013] (4) Bind the steel reinforcement cage inside the outer shell precast member to form a U-shaped steel reinforcement skeleton, and set a cushion block at the bottom of the steel reinforcement skeleton for rigid support of the main beam precast member.

[0014] (5) Lift the main beam precast member, lift it in the order of first in the middle and then on both sides, and make the splicing joint neat. During the alignment process, align the corrugated pipes in adjacent segments by socket connection, and use end forms at both ends of the capping beam to seal the casting space between the main beam precast member and the outer shell precast member to form a space to be cast.

[0015] (6) Cast in place into the space to be cast with ultra-high performance concrete, and use ramming tools for ramming operations. After the casting is completed, make the capping beam form a horizontal upper surface.

[0016] (7) After the ultra-high performance concrete is cured to reach the design strength, tension the prestressed steel strand bundle and seal the anchor to complete the construction.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This technology adopts a large cantilever prestressed concrete capping beam with semi-precast segment assembly and semi-in-situ casting. Its structural form of using reinforced concrete precast members and local wet connection construction with ultra-high concrete can solve the problems of complex construction and numerous processes of the overall in-situ casting large cantilever prestressed concrete capping beam, overcome the difficulties of transportation and hoisting of the overall precast capping beam, and avoid the unfavorable factors of the stress of the segment joints of the segment precast capping beam. It will improve the safety of the construction process of the traditional large cantilever prestressed concrete capping beam, greatly reduce the quantity and engineering volume of the construction supports and formworks for the in-situ casting concrete capping beam on the whole site, and avoid the adverse effects brought by the segment joints of the fully precast segment assembly capping beam, having obvious economic and social benefits. The structure of the present invention is simple, the design is reasonable, the construction is convenient, and the comprehensive economic benefit is improved.

[0018] The following further describes the present invention in detail with reference to the drawings and specific embodiments. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention; Figure 2 It is a front elevation view of the outer shell precast member in an embodiment of the present invention; Figure 3 It is a plan view of the outer shell precast member in an embodiment of the present invention; Figure 4 It is a front elevation view of the rectangular cross-section prestressed concrete member in an embodiment of the present invention; Figure 5 It is a plan view of the rectangular cross-section prestressed concrete member in an embodiment of the present invention; Figure 6 This is a schematic diagram of the mid-span cross-section of the outer shell precast component in the embodiment of the present invention, showing the effect after being filled with ultra-high performance concrete; Figure 7 This is a schematic diagram of the mid-span cross-section of the outer shell precast component in the embodiment of the present invention, showing the effect before being filled with ultra-high performance concrete; Figure 8 This is a schematic diagram of the cantilever end cross-section of the outer shell precast component in the embodiment of the present invention, showing the effect after being filled with ultra-high performance concrete; Figure 9 This is a schematic diagram of the cantilever end cross-section of the outer shell precast component in the embodiment of the present invention, showing the effect before being filled with ultra-high performance concrete.

[0020] In the figure: 10 Outer shell precast component, 11 Bottom plate, 12 Side plate, 13 Shear key, 14 Short steel bars, 15 Steel bar sleeves, 16 Joint mortar, 101 Mid-span outer shell precast component, 102 Cantilever outer shell precast component, 103 Steel bar perforations, 20 Main beam precast component, 21 Bellows, 22 Insertion sleeve, 23 Step lap surface, 24 Reserved jacks, 201 Mid-span precast component, 202 End-side precast component, 30 Ultra-high performance concrete connection layer, 31 Steel bar skeleton, 32 Spacers, 40 Temporary support, 50 Pier, 51 Reserved steel bars. Detailed implementation manners

[0021] To make the above features and advantages of the present invention more obvious and understandable, specific embodiments are hereinafter given and described in detail in conjunction with the accompanying drawings as follows.

[0022] Such as Figures 1 to 9As shown, a semi-precast segmental assembled large cantilever prestressed concrete capping beam is systematically presented. This capping beam is constructed by means of prefabrication on the ground, high-altitude assembly and local construction with ultra-high performance concrete. The spatial physical structure of this prestressed concrete capping beam consists of three parts: an outer shell precast member 10, an internal main beam precast member 20 (precast and formed), and an ultra-high performance concrete connection layer 30 (cast-in-place construction). Among them, the outer shell precast member 10 and the main beam precast member 20 are formed by the precast process of ordinary reinforced concrete. This precast process is precast and formed in the factory, fabricated and hoisted in segments, which can effectively reduce the cost of precast molds and hoisting. By additionally building temporary supports 40 on both sides of the pier, with the hoisting operation of a crane, the high-altitude erection of the above-mentioned outer shell precast member 10 and main beam precast member 20 is completed. This erection process is an assembled construction in the form of building blocks and forms a casting cavity. In this casting cavity, hardening connection is completed by casting ultra-high performance concrete in situ, forming a complete capping beam that combines semi-precast and semi-cast-in-place processes. The mechanical properties of this capping beam are intact, having the dual advantages of traditional cast-in-place concrete capping beams and prestressed precast capping beams, that is, the combination of the advantages of mechanical properties and construction processes. The following will be described in detail with reference to the structural specification drawings.

[0023] The outer shell precast member 10, the cross-section of this outer shell precast member is a U-shaped reinforced concrete precast part, and its vertical cross-section is a U-shaped profile, hence the name, the outer shell precast member. That is, this outer shell precast member 10 is composed of a bottom plate 11 and side plates 12 on both sides, which is a reinforced concrete precast member, and the internal space is for placing the main beam precast member. Preferably, roughening treatment is carried out on the inner surface of this outer shell precast member 10 (including the inner surface of the bottom plate 11 and the inner surface of the side plates 12) to form a roughened surface. At the same time, shear keys 13 are precast on the inner surface of the outer shell precast member. These shear keys 13 are shear studs or short reinforcing bars. That is, a part of this shear key is embedded inside this outer shell precast member, and the other part is exposed in the in-situ casting space of the internal ultra-high performance concrete to form a shear key. The existence of this shear key further improves the bonding strength with the cast-in-place ultra-high performance concrete, especially improving the shear performance of the bonding surface between the two. In the embodiment of the present invention, the design of the shear key facilitates better interfacial connection with the cast-in-place ultra-high performance concrete.

[0024] The outer shell precast member 10 in this embodiment is composed of a three-section outer shell precast member, that is, it can be divided into a mid-span outer shell precast member 101 and a cantilever outer shell precast member 102 according to different positions. And short steel bars 14 with a length of not less than ten centimeters are reserved at the docking surfaces of two adjacent sections of the outer shell precast members. During the docking process of the two outer shell precast members, the two short steel bars 14 are mechanically connected by a steel bar sleeve 15 (steel bar socket), that is, the steel bar sleeve 15 is used to mechanically fix the exposed connecting short steel bars 14 of the two sections of the outer shell precast members 1. And the splicing joint is locally caulked and sealed with caulking mortar 16 or a self-expanding sealing strip to prevent slurry leakage at the splicing joint (during the construction process of cast-in-place ultra-high performance concrete). After the above construction is completed, the three-section outer shell precast members form a complete outer shell precast member 10, and the three-section design further reduces the prefabrication difficulty, as well as the hoisting and transportation difficulties, and has higher feasibility.

[0025] Further, both ends of the mid-span outer shell precast member 101 and one end of the cantilever outer shell precast member 102 are lapped on two piers. That is, both ends of the mid-span outer shell precast member 101 and the cantilever outer shell precast member respectively occupy half of the lapping position of the pier. And steel bar perforations 103 are provided on the bottom plate of the outer shell precast member at the lapping or placing position. The existence of the steel bar perforations enables the reserved steel bars 51 at the top of the pier 50 to pass through the steel bar perforations and be inserted and connected with the reserved jacks in the internal mid-span main beam precast member. After connection, the pier is mechanically fixed or grouted and fixed with the internal mid-section main beam precast member, and they are connected into one body. That is, there is also a rigid connection between the above-mentioned mid-section main beam precast member and the reserved steel bars of the pier.

[0026] The main beam precast member 20 is placed in the internal channel of the outer shell precast member 10. The main beam precast member 20 is a solid reinforced concrete structure with a rectangular cross-section, and corrugated pipes are provided inside the main beam precast member. To reduce the hoisting and transportation difficulties of the main beam precast member, the main beam precast member 20 is composed of three-section concrete precast members on the left, middle, and right. Specifically, the three-section concrete members are all solid reinforced concrete precast members, and corrugated pipes 21 are reserved inside. And the corrugated pipes 21 in two adjacent sections of the concrete members are mutually connected. After being installed in place, the corrugated pipes 21 between two adjacent segments are aligned, and a socket 22 is used for socket connection to form a channel convenient for the construction of prestressed steel strands.

[0027] In an embodiment of the present invention, three-section main girder precast members 20 overlap with each other to form a continuous main girder. For the convenience of description, they are divided into a mid-span precast member 201 and end-side precast members 202. A stepped lap joint surface 23 is provided at the lap joint surface between the unilateral precast members at both ends and the mid-span precast member. A bracket-like connection is formed through the cooperation of two steps, which improves the butting speed of the two, and this has a positive significance for high-altitude operations.

[0028] In an embodiment of the present invention, corrugated pipes are prefabricated inside the main girder precast member 20, and these corrugated pipes are also the threading channels for subsequent prestressed steel strand bundles 23. Moreover, during the butting process of the above three-section rectangular cross-section reinforced concrete members, the corresponding corrugated pipes are connected by socket connection to facilitate the smooth threading.

[0029] In an embodiment of the present invention, the segment joints of the main girder precast member 20 and the segment joints of the outer shell precast member 10 cannot be on the same cross-section and need to be staggered by a certain distance.

[0030] In this embodiment, the mid-span precast member 201 completely covers the two segment joints of the outer shell precast member 10, and a reserved socket 24 for mechanical cooperation with the reserved steel bars 51 is provided in the mid-span precast member 201.

[0031] In this embodiment, the outer shell precast member 10 forms four-point supports at the bridge pier 50 and the temporary support 40. Moreover, the U-shaped structure in the outer shell precast member itself has reliable anti-bending performance and has sufficient stability to bear its own weight and the weight of the main girder precast member 20 inside it.

[0032] After the above outer shell precast member 10 is constructed, it forms a casting formwork for ultra-high performance concrete. By placing the main girder precast member 20 inside, through the three-section designed main girder precast member, and combining with the prestressed steel strand construction process, the three-section main girder precast members are assembled into a whole, cooperating with the sealing of the side formwork at both ends, and finally forming a casting space for ultra-high performance concrete. Through the solidification of this ultra-high performance concrete, the main girder precast member inside and the outer shell precast member outside are connected into a whole.

[0033] After the construction of the cast-in-place ultra-high performance concrete, an ultra-high performance concrete connection layer 30 is formed covering the main girder precast member in the four directions of up, down, left, and right. Moreover, the layer thickness of the ultra-high performance concrete connection layer 30 should not be less than the wall thickness of the outer shell precast member 10 to provide sufficient transitional connection performance. Through the hardening of the ultra-high performance concrete connection layer 30, the main girder precast member 20 inside and the outer shell precast member outside are integrated, making the inside and outside of the capping beam connected into a whole to jointly bear the load.

[0034] After construction, the capping beam in this embodiment has relatively strong overall performance. Among them, the U-shaped outer shell precast member 10 provides the external formwork for the structural construction process. All the prestressed steel strand bundles of the capping beam are arranged inside the main beam precast member, and the ends of both ends of the prestressed steel strand bundles are buried in the cast-in-place ultra-high performance concrete to form the middle layer of the capping beam.

[0035] Furthermore, in the embodiment of the present invention, a steel bar skeleton 31 is arranged inside the ultra-high performance concrete connection layer 30, and this steel bar skeleton is arranged inside the middle layer by on-site binding. The reserved steel bars 51 of the pier are bound or welded and fixed with the steel bar skeleton in the ultra-high performance concrete connection layer 30, further improving the overall mechanical performance of the capping beam.

[0036] Lay the left, middle and right three main beam precast members 20 in the middle of the U-shaped outer shell precast member, try to be centered, and place a plurality of permanent positioning pads between the two, so that a proper distance is maintained between the two, and a space sufficient to pour ultra-high concrete is formed to avoid the influence of ramming operation on the position.

[0037] In the embodiment of the present invention, the excellent mechanical properties of the ultra-high performance concrete are utilized to improve the overall mechanical performance of the capping beam.

[0038] A construction method for a semi-precast segment assembled large cantilever prestressed concrete capping beam includes the following steps: (1) According to the specific dimensions, weight and layout of the prestressed steel strand bundles of the capping beam, divide the capping beam into an outer shell precast member, a main beam precast member, and an ultra-high performance concrete connection layer outside the capping beam, and carry out the design and drawing of the drawings. Among them, according to the weight, transportation and hoisting conditions of the outer shell precast member and the main beam precast member, divide the outer shell precast member and the main beam precast member into three outer shell precast members, and divide the main beam precast member into three rectangular cross-section prestressed concrete segments. The segment joints of the outer shell precast member and the segment joints of the rectangular cross-section prestressed concrete member cannot be on the same cross-section and need to be staggered by a certain distance, that is, the splicing joints are staggered.

[0039] (2) Prefabricate and form the outer shell precast member and the main beam precast member in the factory according to the requirements of the drawings, and reserve a prestressed steel strand bundle channel in the main beam precast member.

[0040] (3) Manufacture the obtained outer shell precast member, in which a steel bar perforation is reserved at the bottom of the outer shell precast member. This steel bar perforation is a vertically arranged hole, and its function is to allow the reserved steel bars at the top of the pier to pass through, that is, to pass through the hole from bottom to top. The main bars at the segment joints need to reserve a certain length according to the segment joint width to form short steel bars 14 for the connection of the main bars between segments in the later stage. The inner surface of the outer shell precast member is made into a rough surface and provided with several shear keys 13 to facilitate better interface connection with the cast-in-place ultra-high performance concrete.

[0041] (4) Prefabricate main girder precast components according to the segmented section dimensions. Corrugated pipes are embedded inside the main girder precast components, and bracket structures are provided at the overlapping surfaces between the main girder precast components, which are used to assist the rapid docking of two main girder precast components during the construction stage.

[0042] (5) After the concrete strength of each precast segment reaches the design strength, transport and hoist the precast U-shaped outer shell precast components and erect them on the piers and temporary piers at the bottom of the capping beam. The reserved steel bars at the top of the pier need to pass through the holes reserved at the bottom of the outer shell precast components. Connect the short steel bars 14 between the outer shell precast components with steel bar sleeves, so as to form a mechanical connection between the three U-shaped outer shell precast components. During this process, ensure that the three U-shaped outer shell precast components are in a straight line, and use sealing materials to fill the joints at the splicing seams between adjacent two U-shaped outer shell precast components.

[0043] (6) Bind the steel bar skeleton of the middle layer of the capping beam according to the specific dimensions. The steel bar skeleton covers at least the bottom of the middle layer of the capping beam, and several permanent positioning pads are arranged at the bottom of the middle layer of the capping beam to form an auxiliary support for the outer shell precast components and the rectangular cross-section reinforced concrete components.

[0044] (7) Transport and hoist the rectangular cross-section reinforced concrete component and place it on the permanent positioning pads 32, and ensure that the reserved steel bars at the top of the pier are fixed to the reserved steel bars on the rectangular cross-section reinforced concrete component. Connect the corrugated pipes embedded between adjacent segments through socket connection with corrugated pipes to form a prestressed pipe-passing channel. Connect the main steel bars between the precast rectangular cross-section reinforced concrete components with steel bar sleeves.

[0045] (8) Bind the steel bar skeleton of the top layer of the capping beam according to the specific dimensions. Use end forms to seal the two ends of the U-shaped reinforced concrete outer shell composed of three sections. Specifically, the end form is a U-shaped formwork, which is fixed at the end for temporary sealing.

[0046] (9) Cast the concrete of the middle layer and the top layer of the capping beam with ultra-high performance concrete, fill the space, and use a vibrator to compact it.

[0047] (10) After the ultra-high performance concrete cures to reach the design strength, tension the prestressed steel strand bundles and seal the anchors, and continue to cure until it is completely hardened to complete the construction.

[0048] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those skilled in the relevant art to the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A semi-precast segment assembled large cantilever prestressed concrete capping beam, characterized in that: It includes a shell precast member (10), a main beam precast member (20), and an ultra-high performance concrete connection layer (30). Among them, the shell precast member (10) is composed of three segments assembled together, and mechanical connection and slurry leakage prevention caulking are carried out at the splicing joints of adjacent two segments of the shell precast member. The shell precast member is a reinforced concrete precast member with a U-shaped cross-section, and the shell precast member is placed on the top of the bridge pier; the main beam precast member (20) is composed of three segments assembled together, and the splicing joints of the three segments of the main beam precast member are staggered from the splicing joints of the three segments of the shell precast member, and there is a corrugated pipe in the assembled main beam precast member. By threading a prestressed steel strand bundle through the corrugated pipe, the three segments of the main beam precast member (20) are formed into one body under the tension of the prestressed steel strand bundle; shear keys or / and roughened surfaces are arranged on the surface of the shell precast member or / and the main beam precast member; and an ultra-high performance concrete connection layer (30) is formed by in-situ construction in the cavity between the shell precast member and the main beam precast member, and a steel bar skeleton (31) is also arranged in the ultra-high performance concrete connection layer.

2. A semi-precast segment assembled large cantilever prestressed concrete capping beam according to claim 1, wherein, Reinforcing bar perforations for connecting with the main reinforcement bars of the bridge pier are arranged on the shell precast member (10) or / and the main beam precast member (20), and welded connection or grouting connection is carried out.

3. A semi-precast segment assembled large cantilever prestressed concrete capping beam according to claim 1, characterized in that, The mechanical connection of adjacent main reinforcement bars is completed through a reinforcing bar sleeve at the splicing joint of two segments of the shell precast member.

4. A semi-precast segment assembled large cantilever prestressed concrete capping beam according to claim 1, characterized in that: The steel bar skeleton (31) and the shear key are auxiliarily fixed by welding or binding.

5. A semi-precast segment assembled large cantilever prestressed concrete capping beam according to claim 1, characterized in that: A stepped concave-convex fit is arranged at the splicing surface of the main beam precast member.

6. The semi-precast segment assembled large cantilever prestressed concrete capping beam according to claim 1, wherein: The corrugated pipes between adjacent main beam precast members are connected by socket connection.

7. A semi-precast segment assembled large cantilever prestressed concrete capping beam according to claim 1, characterized in that: The cross-section of the ultra-high performance concrete connection layer is in a box shape surrounded by four sides or a U shape surrounded by three sides.

8. A construction method for a semi-precast segment assembled large cantilever prestressed concrete capping beam, characterized in that, It includes the following steps: (1) According to the specific dimensions of the capping beam and the layout of the prestressed steel strand bundle, the capping beam drawing is disassembled to form the prefabrication drawings of the shell precast member (10) and the main beam precast member (20); (2) The prefabrication of the shell precast member (10) and the main beam precast member (20) is carried out in the prefabrication yard; (3) The erection of temporary supports is carried out, and the hoisting of the three segments of the shell precast member is completed, so that the three segments of the shell precast member are placed on the bridge pier and the temporary supports. Mechanical connection of the three segments of the shell precast member is carried out using reinforcing bar sleeves, and caulking is carried out using caulking mortar or caulking rubber strips; (4) The steel reinforcement cage is bound inside the shell precast member to form a U-shaped steel bar skeleton, and a cushion block is arranged at the bottom of the steel bar skeleton. The cushion block rigidly supports the main beam precast member; (5) Hoist the main beam precast member, hoist it in the order of first in the middle and then on both sides, and make the splicing joints neat. During the alignment process, the corrugated pipes in adjacent segments are aligned and connected by socket connection. At both ends of the capping beam, end forms are used to block the pouring space between the main beam precast member and the shell precast member to form a space to be poured; (6) Pour in-situ into the space to be poured using ultra-high performance concrete, and use ramming tools for ramming operations. After pouring, the capping beam forms a horizontal upper surface; After the ultra-high performance concrete is cured to reach the design strength, the prestressed steel strand bundles are tensioned and the anchor heads are sealed to complete the construction.

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