Split type bent cap and construction method thereof

Abstract

The invention discloses a split type bent cap and a construction method thereof, belongs to the field of bridge engineering, and solves the bottleneck problems in the aspects of weight, precision, efficiency, durability and the like in traditional bent cap construction. The method mainly solves the bottleneck problems in the aspects of weight, precision, efficiency, durability and the like in traditional capping beam construction, and meanwhile provides a key technical path for industrialization and greenization transformation of bridge engineering. The construction method comprises the steps that the bent cap unit is hoisted to the position above the bridge pier and slowly lowered, so that the connecting steel bars are inserted into the socket holes, and the placing faces are placed on the top of the bridge pier; after socket mounting is completed, the bent cap units are sequentially connected through the energy dissipation tie bars; and after connection is completed, high-strength concrete is poured into the socket hole through the cast-in-place notch, the bent cap unit and the pier are connected into a whole, and the containing groove is blocked. A traditional integral type cover beam is transformed into a split type structure, the cover beam is modularized into a plurality of standardized light cover beam units, and dependence on hoisting equipment is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of bridge engineering, and in particular relates to a split cap beam and a construction method thereof. Background Art

[0002] As bridge engineering develops towards high efficiency and assembly, the application of traditional prefabricated reinforced concrete cap beams in substructures has gradually exposed significant limitations. At present, bridge pier cap beams are mostly prefabricated in an integral manner. Due to the characteristics of concrete materials, their heavy weight leads to high transportation and hoisting costs. Especially in complex terrains such as mountainous areas and river crossings, heavy components place strict requirements on the bearing capacity of temporary supports and equipment performance. They are even forced to switch to cast-in-place technology due to site conditions, which seriously restricts construction efficiency. At the same time, traditional cap beams have extremely high installation accuracy requirements, and uncontrollable factors such as on-site foundation positioning deviation and splicing error can easily cause component dislocation, which not only affects the structural stress performance, but also requires additional manpower for adjustment, further increasing the construction period and cost. In addition, the production, transportation and installation of large prefabricated components rely on intensive resource investment. In the context of tightening environmental protection requirements and intensive engineering development, its extensive model is unsustainable. In response to the above pain points, ultra-high performance concrete (UHPC) provides a new path for lightweighting and performance improvement of cap beams with its high strength, light weight and strong durability. However, single UHPC prefabricated cap beam still faces problems such as being too large in overall size and complex node connections. Summary of the invention

[0003] The purpose of the present invention is to provide a split cap beam, which mainly solves the bottleneck problems in weight, precision, efficiency and durability in the construction of traditional cap beams, and at the same time provides a key technical path for the industrialization and green transformation of bridge engineering.

[0004] Another object of the present invention is to provide a construction method for a split cap beam.

[0005] The technical solution of the present invention is: a split cap beam, including multiple cap beam units, the multiple cap beam units are arranged side by side along the transverse bridge direction, adjacent cap beam units are connected by energy-absorbing tie rods, socket holes are opened on the lower surface of the cap beam unit, and cast-in-place grooves are opened on the upper surface of the cap beam unit, and the cast-in-place grooves are connected to the socket holes.

[0006] As a further improvement of the present invention, the cap beam unit is prefabricated by using C60 concrete combined with prestressing method, and a prestressed steel strand is arranged on the top of the cap beam unit.

[0007] As a further improvement of the present invention, a pre-embedded anchor is provided at the end of the cap beam unit, and the energy-absorbing tie rod is connected to the pre-embedded anchor by a fixing bolt.

[0008] As a further improvement of the present invention, it also includes an adjustable tensioning mechanism, which includes an adjustment hole, an adjustment bolt and an anti-loosening gasket. The adjustment hole is opened on the embedded anchor, and the energy-absorbing tie rod is fastened to the adjustment hole through the adjustment bolt and the anti-loosening gasket.

[0009] As a further improvement of the present invention, the socket is in the shape of a cavity that is small at the top and large at the bottom, a receiving groove is provided on the outer periphery of the bottom of the socket, and the bottom of the socket is a shelf surface.

[0010] As a further improvement of the present invention, a key tooth groove is provided on the inner wall of the socket.

[0011] As a further improvement of the present invention, the key tooth groove adopts a spiral key tooth groove in a spiral line shape, or adopts an annular key tooth groove with a concave-convex tooth shape.

[0012] As a further improvement of the present invention, a pad stone is provided on the top of the cap beam unit, and a steel stopper is provided beside the outermost pad stones of the cap beam units on both sides, and the steel stopper is located on the inner side of the pad stone.

[0013] As a further improvement of the present invention, inwardly converging inclined surfaces are provided on both sides of the lower section of the cap beam unit.

[0014] A construction method for a split cap beam comprises the following steps: A. Reserve connecting steel bars on the top of the pier; B. Lift the cap beam unit to the top of the bridge pier, and then slowly lower it so that the connecting steel bar is socketed in the socket hole and the resting surface is placed on the top of the bridge pier; C. After completing the socket installation of each cap beam unit, connect each cap beam unit in sequence through energy-absorbing tie rods; D. After completing the connection between the cap beam units, pour high-strength concrete into the socket through the cast-in-place groove to connect the cap beam unit and the bridge pier as a whole, and seal the receiving groove.

[0015] The beneficial effects of the present invention are: 1. The present invention transforms the traditional integral cap beam into a split structure, and modularizes the cap beam into multiple standardized lightweight cap beam units, realizing the refined construction mode of "factory prefabrication - split transportation - on-site rapid assembly". This design can not only reduce the weight of a single piece by more than 60% and greatly reduce the dependence on lifting equipment, but also adapt to complex foundation conditions through modular adjustment, improve construction fault tolerance, and provide an innovative solution for the assembly of bridge substructures that is both economical and reliable.

[0016] 2. The present invention uses energy-absorbing tie rods to connect the cap beam units together, so that the cap beam of the present invention only bears negative bending moments, which solves the problem that traditional cap beams are prone to cracking. The energy-absorbing tie rods reduce the energy-absorbing characteristics, avoid the problem of mid-span deformation in traditional cap beams, and achieve earthquake-resistant functions. The energy-absorbing tie rods have a multi-level energy-absorbing protection mechanism and replaceable energy-absorbing components. Under medium and small earthquakes, the energy-absorbing tie rods mainly bear axial tension and compression forces, and only undergo elastic deformation to maintain the normal use function of the structure; under large earthquakes, the energy-absorbing tie rods will yield at the root bolt connection, and dissipate energy by forming a plastic hinge area; after a strong earthquake, if the deformation of the energy-absorbing tie rods or bolt connections exceeds the limit, they can be partially replaced without dismantling the entire structure, so that rapid repair can be achieved.

[0017] 3. The length of the energy-absorbing tie rod in the present invention can be adjusted according to the site requirements, which has greater flexibility and a wider range of applications. The present invention can also be used to widen an existing bridge by connecting the cap beam unit to the existing cap beam through the energy-absorbing tie rod.

[0018] 4. The cap beam unit in the present invention is prefabricated by prestressing method. Compared with the traditional post-tensioning method, the quality is easier to control, the loss of prestress is also easier to control, and one process of on-site construction is reduced, shortening the construction period.

[0019] 5. The present invention designs an adjustable tensioning mechanism. When installing the energy dissipation tie rod, the installation position and installation angle of the energy dissipation tie rod can be fine-tuned by adjusting the position of the adjusting bolt in the adjusting hole to eliminate construction errors and improve installation accuracy.

[0020] 6. The present invention arranges a keyway on the inner wall of the socket. Compared with the traditional socket process, the present invention greatly improves the shear resistance and integrity of the pier-beam node, realizes the coordinated optimization of the keyway structure and the grouting process, and is suitable for bridges in high-intensity earthquake zones.

[0021] 7. The construction method of the present invention is simple and convenient, and no on-site welding is required, which reduces the construction difficulty. After the connection steel bars reserved on the top of the pier are inserted into the socket holes of the cap beam, they are consolidated by grouting high-strength concrete, which can achieve rapid installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the three-dimensional structure of the split cap beam of the present invention; Figure 2 It is a schematic diagram of the elevation structure of the split cap beam of the present invention; Figure 3 It is a structural schematic diagram of the adjustable tensioning mechanism in the present invention; Figure 4 It is a structural schematic diagram of the shelf surface in the present invention; Figure 5 It is a structural schematic diagram of the spiral key tooth groove in the present invention; Figure 6 It is a structural schematic diagram of the concave-convex key tooth groove in the present invention; Figure 7 It is a schematic diagram of the side structure of the split cap beam of the present invention; Figure 8 It is a construction schematic diagram of the split cap beam of the present invention; Fig. 9 It is the moment envelope diagram of the split cap beam of the present invention under earthquake action; Fig.10 It is the moment envelope diagram of the traditional integral cap beam under earthquake action.

[0023] In the figure, 1-cap beam unit; 2-energy absorption tie rod; 3-socket; 4-cast-in-place notch; 5-embedded anchor; 6-key groove; 7-fixing bolt; 8-adjusting bolt; 9-adjusting hole; 10-anti-loosening gasket; 11-accommodating groove; 12-bridge pier; 13-pad stone; 14-rubber bearing; 15-steel block; 16-connecting steel bar; 17-prestressed steel strand; 18-resting surface; 19-inclined surface. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] Embodiment 1, like Figure 1-5 As shown, a split cap beam comprises a plurality of cap beam units 1, which are arranged side by side along the transverse direction of the bridge, and adjacent cap beam units 1 are connected by steel energy-absorbing tie rods 2, and a socket hole 3 is provided on the lower surface of the cap beam unit 1, and a cast-in-place notch 4 is provided on the upper surface of the cap beam unit 1, and the cast-in-place notch 4 is connected to the socket hole 3. The cast-in-place notch 4 can be used as a pouring port or as an exhaust port.

[0026] In this embodiment, two cap beam units 1 are provided.

[0027] The cap beam unit 1 is prefabricated with C60 concrete combined with prestressing by pre-tensioning method, and a prestressed steel strand 17 is arranged on the top of the cap beam unit 1. The cap beam of the present invention serves as a lower structure, and the amount of prestress can be minimized. Moreover, the force system of the cap beam of the present invention is a full negative bending moment force system, which is different from the positive and negative bending moment alternating force system of the traditional integral cap beam. The prestressed steel strand 17 only needs to be arranged on the top. In this embodiment, the main beam adopts UHPC light I-beam, which is a lightweight and high-strength structure, and weighs about 50% of the weight of the traditional small box beam structure. The main beam and the cap beam of the present invention form a stiffness matching system.

[0028] The end of the cap beam unit 1 is provided with an embedded anchor 5, and the energy dissipation tie rod 2 is connected to the embedded anchor 5 by a fixing bolt 7. The embedded anchor 5 is made of fatigue-resistant steel.

[0029] It also includes an adjustable tensioning mechanism, which includes an adjustment hole 9, an adjustment bolt 8 and an anti-loosening washer 10. The adjustment hole 9 is opened on the embedded anchor 5, and the energy dissipation tie rod 2 is fastened to the adjustment hole 9 through the adjustment bolt 8 and the anti-loosening washer 10. In this embodiment, the adjustment hole 9 is a cross-shaped hole.

[0030] The socket 3 is a hollow shape that is small at the top and large at the bottom. On the one hand, it can effectively reduce the difficulty of disengaging the built-in core mold when prefabricating the cap beam; on the other hand, it can save the amount of cast-in-place concrete at the construction site. A receiving groove 11 is provided on the outer periphery of the bottom of the socket 3, and the bottom of the socket 3 is a shelf surface 18. The pier 12 extends into the receiving groove 11, and the shelf surface 18 is placed on the top of the pier 12. On the one hand, the receiving groove 11 can accommodate piers 12 of different diameters. In this embodiment, it can adapt to piers with diameters of 1.0m~1.1m, and can adapt to position deviations during installation; on the other hand, when pouring concrete in the socket 3, the receiving groove 11 can also play a venting role.

[0031] The inner wall of the socket 3 is provided with a key groove 6. The key groove 6 adopts a spiral key groove in the shape of a spiral line. Figure 5 As shown, its cross section is trapezoidal, or a ring key groove with concave and convex tooth shape is used as shown Figure 6 As shown, its cross section is rectangular.

[0032] A pad stone 13 is provided on the top of the cap beam unit 1, and a rubber support 14 is provided on the pad stone 13. A steel stopper 15 for preventing the beam from falling is provided beside the outermost pad stone 13 of the cap beam units 1 on both sides. The steel stopper 15 is located inside the pad stone 13 to shorten the length of the cap beam unit 1, reduce the weight of the cap beam unit 1, and facilitate hoisting construction. Compared with traditional concrete stops, the steel stopper 15 has a better energy dissipation mechanism, and the steel has self-restoring force, and can return to its original state after impact, and can withstand repeated impacts.

[0033] The cap beam of the present invention is a fully negative moment stress-bearing structure, therefore, inwardly converging inclined surfaces 19 are provided on both sides of the lower section of the cap beam unit 1 to reduce the amount of concrete used at the positive moment, reduce deadweight, and make the structure stronger and more economical.

[0034] A construction method for a split cap beam comprises the following steps: A. Connection steel bars 16 are reserved at the top of pier 12. Figure 8 As shown; B. Lift the cap beam unit 1 to the top of the bridge pier 12, and then slowly lower it so that the connecting steel bar 16 is socketed in the socket hole 3 and the resting surface 18 is placed on the top of the bridge pier 12; C. After completing the socket installation of each cap beam unit 1, connect each cap beam unit 1 in sequence through the energy dissipation tie rod 2. When connecting, first adjust the position of the adjusting bolt 8 in the adjusting hole 9, thereby fine-tuning the installation position and angle of the energy dissipation tie rod, and then tighten the adjusting bolt 8 with the anti-loosening gasket 10 to achieve preliminary positioning, and then drill holes on the energy dissipation tie rod 2 and the embedded anchor 5 and install the fixing bolt 7; D. After completing the connection between the cap beam units 1, pour high-strength concrete into the socket 3 through the cast-in-place notch 4 to connect the cap beam unit 1 and the bridge pier 12 as a whole, and seal the receiving groove 11.

[0035] The present invention transforms the traditional integral cap beam into a split structure, and replaces the traditional solid casting structure with an energy-absorbing tie rod 2 to reduce the amount of concrete, reduce the hoisting weight, and save costs. The energy-absorbing tie rod 2 not only serves to connect the cap beam unit 1, but also serves as an anti-seismic energy-absorbing component to improve the anti-seismic performance of the cap beam.

[0036] The following is a comparison of the moment envelope diagram of the split cap beam of the present invention under earthquake action ( Fig. 9 ) and the moment envelope diagram of the traditional integral cap beam under earthquake action ( Fig.10 ), unit kN·m. Fig. 9 , Fig.10 It can be seen that under the same earthquake action, the maximum bending moment at the top of the traditional integral cap beam is 359.5 kN·m, the maximum bending moment at the top of the pier is 175.5 kN·m, and the maximum bending moment at the bottom of the pier is 142.4 kN·m; after adopting the split cap beam containing the energy-absorbing tie rod 2 of the present invention, the maximum bending moment at the top of the cap beam is 321.2 kN·m, and the internal force is reduced by 10.7%; the maximum bending moment at the top of the pier is 39.4 kN·m, and the internal force is reduced by 77.5%; the maximum bending moment at the bottom of the pier is 124.1 kN·m, and the internal force is reduced by 12.9%.

[0037] The above data prove that, under the same conditions, (1) The split cap beam of the present invention adopts an energy-absorbing tie rod 2, which weakens the mid-span stiffness of the cap beam and transfers the peak value of the bending moment to both sides of the pier top, resulting in a moment redistribution effect. Only negative bending moment occurs in the cap beam. At the same time, the layout of the prestressed steel strands 17 forms a coordinated anti-bending mechanism, which effectively reduces the maximum peak value of the negative bending moment.

[0038] (2) The split cap beam of the present invention actively adjusts the load transfer path through the axial tensile and compressive deformation of the energy-absorbing tie rod 2, thereby significantly reducing the bending moment at the top of the pier, thereby avoiding the formation of a plastic hinge at the top of the pier and significantly improving the seismic safety reserve of the pier column.

[0039] (3) The split cap beam of the present invention reduces the bending moment at the bottom of the pier, indicating that the earthquake energy is dissipated by the deformation of the energy-absorbing tie rod 2 and the pier itself, rather than the pier resisting and absorbing the seismic energy alone. According to the characteristic that the yield point of the energy-absorbing tie rod 2 is lower than that of the pier, the energy-absorbing tie rod 2 yields first under the action of a strong earthquake, forming a plastic hinge area to further dissipate energy, verifying the concept of "multi-level energy dissipation".

Claims

1. A split cap beam, characterized in that: The invention comprises a plurality of cap beam units (1), wherein the plurality of cap beam units (1) are arranged side by side along the transverse direction of the bridge, and adjacent cap beam units (1) are connected via energy-absorbing tie rods (2). A socket hole (3) is provided on the lower surface of the cap beam unit (1), and a cast-in-place groove (4) is provided on the upper surface of the cap beam unit (1), and the cast-in-place groove (4) is connected to the socket hole (3).

2. A split cap beam according to claim 1, characterized in that: The cap beam unit (1) is prefabricated using C60 concrete combined with prestressing by the pre-tensioning method, and a prestressed steel strand (17) is arranged on the top of the cap beam unit (1).

3. A split cap beam according to claim 1 or 2, characterized in that: The end of the cap beam unit (1) is provided with a pre-embedded anchor piece (5), and the energy dissipation tie rod (2) is connected to the pre-embedded anchor piece (5) via a fixing bolt (7).

4. A split cap beam according to claim 3, characterized in that: It also includes an adjustable tensioning mechanism, which includes an adjustment hole (9), an adjustment bolt (8) and an anti-loosening gasket (10). The adjustment hole (9) is formed on the embedded anchor (5), and the energy dissipation tie rod (2) is fastened to the adjustment hole (9) via the adjustment bolt (8) and the anti-loosening gasket (10).

5. The split cap beam according to claim 4, characterized in that: The socket hole (3) is in the shape of a cavity that is smaller at the top and larger at the bottom. A receiving groove (11) is provided on the outer periphery of the bottom of the socket hole (3). The bottom of the socket hole (3) is a shelf surface (18).

6. A split cap beam according to claim 5, characterized in that: The inner wall of the socket hole (3) is provided with a key tooth groove (6).

7. The split cap beam according to claim 6, characterized in that: The key tooth groove (6) adopts a spiral key tooth groove in the shape of a spiral line, or adopts an annular key tooth groove in the shape of a concave-convex tooth.

8. The split cap beam according to claim 7, characterized in that: A pad stone (13) is provided on the top of the cap beam unit (1), and a steel stopper (15) is provided beside the outermost pad stone (13) of the cap beam units (1) on both sides, and the steel stopper (15) is located at an inner side of the pad stone (13).

9. The split cap beam according to claim 8, characterized in that: Inwardly converging inclined surfaces (19) are provided on both sides of the lower section of the cap beam unit (1).

10. A construction method for a split cap beam, characterized in that The following steps are involved: A. A connection steel bar (16) is reserved at the top of the pier (12); B. Lifting the cap beam unit (1) to the top of the bridge pier (12), and then slowly lowering it so that the connecting steel bar (16) is socketed in the socket hole (3) and the resting surface (18) is placed on the top of the bridge pier (12); C. After the socket-and-spigot installation of each cap beam unit (1) is completed, the cap beam units (1) are connected in sequence through the energy-absorbing tie rod (2); D. After the connection between the cap beam units (1) is completed, high-strength concrete is poured into the socket hole (3) through the cast-in-place notch (4), the cap beam unit (1) and the bridge pier (12) are connected as a whole, and the receiving groove (11) is sealed.

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