Method for erecting whole section steel-UHPC composite beam of cable-stayed bridge

Abstract

The invention discloses a cable-stayed bridge integral section steel-UHPC composite beam erecting method which comprises the following steps that between the Nth beam section and the (N + 1) th beam section of an integral section steel-UHPC composite beam, steel top plates are connected through on-site weld joints, and UHPC bridge deck slabs are not connected temporarily; fixing a bridge deck crane on the (N + 1) th beam section, hoisting the (N + 2) th beam section to a specified position by the bridge deck crane, and welding a steel top plate between the (N + 1) th beam section and the (N + 1) th beam section; mounting and tensioning a stay cable of the (N + 2) th beam section; the deck crane moves forwards to the (N + 2) th beam section and conducts secondary tensioning on the stay cable of the (N + 2) th beam section to the designed cable force; reinforcing steel bars of the UHPC bridge deck slab between the Nth beam section and the (N + 1) th beam section are connected through reinforcing steel bar connecting pieces, UHPC is poured at the joint to form a UHPC wet joint, and the weld joint and the UHPC wet joint form a dry-wet combined joint; and the circulation is repeated until closure. According to the invention, the erection efficiency is obviously improved while the safe and reliable stress of the main beam is ensured.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology, and in particular relates to a method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges. Background Technology

[0002] Steel-concrete composite beams combine the advantages of steel and concrete structures and are widely used in long-span cable-stayed bridges. Ultra-high performance concrete (UHPC), due to its excellent compressive and tensile strength and durability, has been applied to composite beam bridge decks in recent years, which can significantly reduce the structural self-weight, improve span capacity and durability.

[0003] For long-span cable-stayed bridges, the main girder is often erected using a bridge deck crane for segmental cantilever assembly. Currently, for precast steel-UHPC composite beams, the wet jointing work during the erection process occupies the work area, leading to extended construction time and bottlenecks in construction efficiency. The traditional construction steps are usually as follows: first, hoist the new beam segment and weld the steel beam; second, pour and cure the wet joints of the UHPC bridge deck; only after the wet joints have strengthened can the bridge deck crane move forward and the next beam segment be hoisted. However, the on-site pouring and curing of UHPC still requires a sufficient strength growth period (usually several days). During this period, key processes such as bridge deck crane lifting of beams and beam segment positioning welding are forced to wait, meaning that the curing period of the wet joints is directly linked to the key construction steps, severely restricting the erection cycle of each segment and becoming a key bottleneck affecting overall efficiency. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges, which significantly improves the construction efficiency while ensuring the overall structural stress performance and joint reliability.

[0005] Technical solution: To achieve the above objectives, the present invention provides a method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges, comprising several steel-UHPC composite beam segments, and the method includes the following steps: S1. The steel top plate on the steel structure box girder between the Nth beam segment and the N+1th beam segment is fixedly connected by field weld to form the lower dry joint between the Nth beam segment and the N+1th beam segment. The UHPC bridge deck between the Nth beam segment and the N+1th beam segment is in an unconnected state. S2. Fix the bridge deck crane on the N+1 beam segment, and lift the N+2 beam segment to be installed by the bridge deck crane; the bridge deck crane lifts the N+2 beam segment to the designated position, and fixes the steel top plate on the steel structure box girder between the N+1 beam segment and the N+2 beam segment by on-site welding to form a dry joint between the N+1 beam segment and the N+2 beam segment; S3. Install the stay cables of the N+2 beam segment and perform one tensioning operation; S4. Move the bridge deck crane forward to the N+2 beam segment and perform secondary tensioning on the cable stays of the N+2 beam segment to achieve the design cable force; S5. Use steel connectors to connect the steel bars of the UHPC bridge deck between the Nth beam segment and the N+1th beam segment, and pour UHPC at the joint to form a wet joint of UHPC between the Nth beam segment and the N+1th beam segment. The dry joint between the Nth beam segment and the N+1th beam segment and the wet joint of UHPC constitute a dry-wet joint. S6. Repeat steps S1 to S5, and continue in this cycle until the closure is complete.

[0006] Optionally, the steel-UHPC composite beam segment includes a steel structure box girder at the bottom and a UHPC bridge deck at the top; the UHPC bridge deck is provided with modular steel mesh inside, the top of the steel structure box girder is provided with a steel top plate, and the upper surface of the steel top plate is provided with studs.

[0007] Optionally, the thickness of the UHPC bridge panel is 140~200mm.

[0008] Optionally, the width of the dry-wet joint is 150~300mm.

[0009] Optionally, the thickness of the steel top plate is 6~10mm.

[0010] Optionally, the steel top plate located at the dry-wet joint is a thickened steel plate, the thickness of which is 1.2 to 2 times the thickness of the steel top plate, and the width of the thickened steel plate on one side is 1 to 2 times the width of the dry-wet joint.

[0011] Optionally, the thickened steel plate is connected to the adjacent steel top plate by a weld.

[0012] Optionally, the steel bar connector is a Class I joint.

[0013] Optionally, the UHPC cast at the joint is a micro-expansion UHPC.

[0014] Optionally, a temporary steel plate for moving the bridge deck crane may be laid at the joint between the N+1 beam segment and the N+2 beam segment.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) This invention innovates the traditional paradigm that the curing of UHPC wet joints must occupy the critical construction period. Through the construction process of “the dry joint of the steel top plate first bears the construction load alone, and the UHPC wet joint then participates in the structural stress together”, the curing of wet joints between beam segments no longer affects the hoisting of subsequent beam segments, and the main beam erection period is greatly shortened. (2) During the construction phase of this invention, the steel top plate and weld of the beam segment connection bear the construction load. After the bridge deck crane moves forward, the UHPC wet joint is poured under the stress condition of small tensile stress between beam segments, which improves the construction efficiency of the main beam and at the same time ensures the structural safety. (3) In the case of areas with high local tensile stress, the present invention can enhance the load-bearing performance of the main beam structure by locally thickening the steel top plate, thereby greatly improving the safety of the structure; (4) This invention is applicable not only to cable-stayed bridges, but also to various bridge types such as cable-stayed-suspension cooperative system bridges, and has wide applicability. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the construction method of the present invention; Figure 2 This is an overall schematic diagram of the present invention; Figure 3 This is a schematic diagram of the steel-UHPC composite beam segment in this invention; Figure 4 This is a schematic diagram of the hoisting of the steel-UHPC composite beam segment in this invention; Figure 5 This is a schematic cross-sectional view of the connection between the steel-UHPC composite beam bridge deck and the bridge deck in this invention. Figure 6 This is a schematic diagram of the cross-section of the bridge deck connection at the locally thickened steel top plate of the steel-UHPC composite beam in this invention; Figure 7 This is a schematic diagram of the dry-wet joint section of the steel-UHPC composite beam bridge deck in this invention; Figure 8 This is a schematic diagram of the dry-wet joint section of the bridge deck at the locally thickened steel top plate of the steel-UHPC composite beam in this invention; In the diagram, the following components are included: steel-UHPC composite beam segment 1, dry-wet joint 2, stay cable 3, bridge deck crane 4, temporary steel plate 5, Nth beam segment 1-1, N+1th beam segment 1-2, N+2th beam segment 1-3, N+3th beam segment 1-4, steel structure box girder 101, UHPC bridge deck 102, modular steel mesh 103, stud 104, steel top plate 105, field weld 106, steel rebar connector 107, UHPC wet joint 108, thickened steel plate 109, and precast weld 110. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0018] In an embodiment of the present invention, a double-tower, double-cable-stayed steel-UHPC composite beam bridge with a main span of 900 meters is used as the engineering background to illustrate the specific implementation process of the present invention in detail. The main beam of this bridge adopts a construction scheme of integral segmental prefabrication and cantilever assembly by bridge deck crane.

[0019] like Figure 1 and Figure 2 As shown, the bridge is assembled symmetrically using a bridge deck crane 4. The bridge erection process is carried out in cycles, with one beam segment installed in each cycle. Figure 1 As shown, taking the installation of beam segment N+2 as an example, where N≥1, the construction process of a complete erection cycle is demonstrated.

[0020] The present invention discloses a method for erecting a monolithic segmental steel-UHPC composite beam for a cable-stayed bridge, comprising several steel-UHPC composite beam segments 1, each including a lower steel box girder 101 and an upper UHPC bridge deck 102; the UHPC bridge deck 102 is provided with modular steel mesh 103 inside, the top of the steel box girder 101 is provided with a steel top plate 105, and the upper surface of the steel top plate (105) is provided with studs 104; the UHPC bridge deck 102 is formed by integral concrete casting, and the steel box girder 101 and the UHPC bridge deck 102 are connected by studs 104.

[0021] The method includes the following steps: S1. The steel top plate 105 on the steel box girder between the Nth beam segment 1-1 and the N+1th beam segment 1-2 is fixedly connected by field weld 106 to form the lower dry joint between the Nth beam segment 1-1 and the N+1th beam segment 1-2. At this time, the connection status between the Nth beam segment 1-1 and the N+1th beam segment 1-2 is as follows: the steel top plate 105 on the lower steel box girder 101 has been fixed by field weld 106 in the previous cycle, but the upper UHPC bridge deck joint has not been treated and is in a temporary state of "dry connection only". S2. Fix the bridge deck crane 4 on the N+1 beam segment 1-2, and lift the N+2 beam segment 1-3 to be installed; the bridge deck crane 4 lifts the N+2 beam segment 1-3 to the designated position for precise positioning; the steel top plate 105 on the steel structure box girder between the N+1 beam segment 1-2 and the N+2 beam segment 1-3 is fixedly connected by on-site weld 106 to form a dry joint between the N+1 beam segment 1-1 and the N+2 beam segment 1-2, which constitutes the dry joint of the wet joint to be poured in the next cycle; S3. Tension the stay cables 3 of the N+2 beam segment 1-3 once to enable the beam segment to initially bear the load, adjust the main beam alignment, and lay temporary steel plates 5 at the joint between the N+1 beam segment 1-2 and the N+2 beam segment 1-3 to prevent the bridge deck crane from affecting the joint when it moves forward; remove the temporary steel plates 5 after the bridge deck crane has passed. S4. Move the bridge deck crane forward and anchor it on the N+2 beam segment 1-3, which has already been initially stressed. Then, perform secondary tensioning on the stay cables of the N+2 beam segment 1-3 to achieve the design cable force. At this point, the N+2 beam segment has become a stable new working surface, and preparations for the hoisting of the N+3 beam segment can begin immediately.

[0022] S5. After step S4 is completed, the tensile stress between beam segment N-1 and beam segment N+1-2 is relatively stable and under non-critical stress conditions. Work begins at the joint between beam segment N-1 and beam segment N+1-2. Steel connectors 107 are used to connect the steel bars of the UHPC bridge deck between beam segment N-1 and beam segment N+1-2. UHPC is poured at the joint to form a wet joint 108 between beam segment N-1 and beam segment N+1-2. The dry joint between beam segment N-1 and beam segment N+1-2 and the wet joint form a dry-wet joint 2. The curing period of the wet joint is completely parallel to the critical process of the next cycle of beam segment hoisting, without interference, thus separating the wet joint construction from the critical path affecting the construction period. S6. Using the N+2 beam segment 1-3 as the new anchor point, repeat steps S1 to S5, and repeat until the beam is closed.

[0023] In this embodiment, the width of the dry-wet joint 2 is 150-300mm. The thickness of the UHPC bridge deck 102 is 140-200mm. The thickness of the steel top plate 105 is 6-10mm. The steel top plate 105 located at the dry-wet joint 2 is a thickened steel plate 109, the thickness of which is 1.2-2 times the thickness of the steel top plate 105. The width of the thickened steel plate 109 on one side is 1-2 times the width of the dry-wet joint 2. The thickened steel plate 109 and the steel top plate 105 are connected by a prefabricated weld 110. The reinforcing bar connector 107 is a primary joint. The UHPC cast at the joint is a micro-expansion UHPC.

[0024] like Figure 3 As shown, each prefabricated steel-UHPC composite beam segment 1 is an industrialized standard segment. Its lower part is a steel structure box girder 101, and its top is a prefabricated UHPC bridge deck 102. Prefabricated steel mesh 103 is embedded within the UHPC bridge deck 102. A steel top plate 105 is provided on the top of the steel structure box girder 101, on which numerous studs 104 are welded. In the prefabrication plant, the bridge deck 102 and the studs 104 on the steel top plate 105 are firmly connected by casting UHPC, forming a shear-resistant connection, thus constituting a complete composite beam segment.

[0025] like Figure 5 and Figure 7As shown, the dry-wet joint 2 is a double-layer composite structure. The lower dry joint is connected by steel top plates 105 of the two beam segments through field welds 106. During the construction phase, it mainly bears tensile stress to ensure structural continuity. The upper wet joint is connected by UHPC bridge deck 102 of the two beam segments through a field-cast UHPC wet joint 108, with the internal reinforcement continuous through steel reinforcement connectors 107. The joint width is designed to be 300mm, and micro-expansion UHPC is used for casting to ensure the durability of the joint.

[0026] For beam segments with large negative bending moments and significant tensile stress on the bridge deck, such as the base of the bridge tower and the top of the auxiliary piers, the dry joints need to be reinforced. For example... Figure 6 and Figure 8 As shown, during factory prefabrication, a thickened steel plate 109 is used in the 300mm wide area at the joint. The thickness of the thickened steel plate is twice that of the original 8mm top plate, i.e., 16mm, and the width on one side is once the joint width, i.e., 300mm. Calculations show that increasing the steel plate thickness from 8mm to 16mm can reduce the tensile stress at the joint by 40%. The thickened steel plate 109 is connected to the steel top plate 105 via a prefabricated weld 110 to ensure processing quality. During on-site welding of the joint, the thickened steel plates 109 on both sides are connected by weld 106, ensuring complete penetration of the thickened steel plates 109 on both sides. This significantly increases the effective thickness of the steel top plate in this area, enabling it to safely withstand greater local tensile stress during construction and ensuring the safety and reliability of the joint during subsequent beam hoisting.

[0027] This invention transforms the traditional serial operation mode into a parallel operation mode, shortening the pure erection cycle of a single segment. At the same time, through local reinforcement design, it ensures the structural safety and final joint quality throughout the construction process, achieving a dual improvement in efficiency and performance.

[0028] This invention aims to solve the problem of low erection efficiency caused by the maintenance of wet joints in UHPC (Ultra-High-Pressure Concrete) bridges occupying critical construction periods in traditional processes. By reconstructing the construction process, in each erection cycle, a new beam segment is first hoisted using a bridge deck crane and its lower steel box girder (including the steel top plate) is welded to form a dry joint. After the stay cables are tensioned and the crane is moved forward, the UHPC bridge deck reinforcement is connected and the wet joint is poured at the previous joint where the steel top plate has been welded, thus forming a dry-wet combined joint. This invention allows the wet joint maintenance period to run concurrently with the preparation work for the hoisting of the next beam segment, significantly shortening the construction cycle. At the same time, measures such as locally thickening the steel top plate can be adopted for high tensile stress areas of the entire bridge, ensuring structural safety and long-term performance of the joints during construction.

Claims

1. A method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges, characterized in that, The method includes several steel-UHPC composite beam segments (1), and includes the following steps: S1. The steel top plate (105) on the steel structure box girder between the Nth beam segment (1-1) and the N+1th beam segment (1-2) is fixedly connected by field weld (106) to form the lower dry joint between the Nth beam segment (1-1) and the N+1th beam segment (1-2). The UHPC bridge deck between the Nth beam segment (1-1) and the N+1th beam segment (1-2) is in an unconnected state. S2. Fix the bridge deck crane (4) on the N+1 beam segment (1-2), and lift the N+2 beam segment (1-3) to be installed; the bridge deck crane (4) lifts the N+2 beam segment (1-3) to the designated position, and fixes the steel top plate (105) on the steel structure box girder between the N+1 beam segment (1-2) and the N+2 beam segment (1-3) with field welds (106) to form a dry joint between the N+1 beam segment (1-1) and the N+2 beam segment (1-2); S3. Install the stay cable (3) of the N+2 beam segment (1-3) and perform one tensioning; S4. Move the bridge deck crane forward to the N+2 beam segment (1-3) and perform secondary tensioning on the stay cables of the N+2 beam segment (1-3) to achieve the design cable force; S5. Use steel connectors (107) to connect the steel bars of the UHPC bridge deck between the Nth beam segment (1-1) and the N+1th beam segment (1-2), and pour UHPC at the joint to form a UHPC wet joint (108) between the Nth beam segment (1-1) and the N+1th beam segment (1-2). The dry joint between the Nth beam segment (1-1) and the N+1th beam segment (1-2) and the UHPC wet joint constitute a dry-wet joint (2). S6. Repeat steps S1 to S5, and continue in this cycle until the closure is complete.

2. The method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges according to claim 1, characterized in that: The integral segmental steel-UHPC composite beam segment (1) includes a steel structure box girder (101) at the bottom and a UHPC bridge deck (102) at the top; the UHPC bridge deck (102) is provided with modular steel mesh (103) inside, the steel structure box girder (101) is provided with a steel top plate (105) on the top, and the upper surface of the steel top plate (105) is provided with studs (104).

3. The method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges according to claim 2, characterized in that: The thickness of the UHPC bridge panel (102) is 100~200mm.

4. The method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges according to claim 1, characterized in that: The width of the dry-wet joint (2) is 150~300mm.

5. The method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges according to claim 1, characterized in that: The thickness of the steel top plate (105) is 6~10mm.

6. The method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges according to claim 1, characterized in that: The steel top plate (105) located at the dry-wet joint (2) is a thickened steel plate (109). The thickness of the thickened steel plate (109) is 1.2 to 2 times the thickness of the steel top plate (105), and the width of the thickened steel plate (109) on one side is 1 to 2 times the width of the dry-wet joint (2).

7. The method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges according to claim 6, characterized in that: The thickened steel plate (109) is connected to the adjacent steel top plate (105) by a weld (110).

8. The method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges according to claim 1, characterized in that: The steel bar connector (107) is a Class I joint.

9. The method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges according to claim 1, characterized in that: The UHPC cast at the joint is a micro-expansion UHPC.

10. The method for erecting integral segmental steel-UHPC composite beams for cable-stayed bridges according to claim 1, characterized in that: Temporary steel plates (5) for moving the bridge deck crane are laid at the joint between the N+1 beam segment (1-2) and the N+2 beam segment (1-3).

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