A combined structure of pre-tensioned UHPC panels and concrete π-shaped beams and its construction method

Abstract

A combination structure of a pre-tensioned UHPC panel and a concrete π-beam and a construction method thereof relate to the technical field of box beams, comprising a UHPC panel and an ordinary reinforced concrete π-beam assembled with the UHPC panel to form a closed box beam structure, wherein the UHPC panel is provided with a pre-tensioned prestressed bundle, two groups of blocks are symmetrically provided on both sides of the panel edge of the UHPC panel, and the two groups of blocks symmetrically form a U-shaped groove assembled with the ordinary reinforced concrete π-beam, and the U-shaped groove is vertically provided with a panel reserved steel bar, and the web end of the ordinary reinforced concrete π-beam is vertically provided with a beam reserved steel bar overlapped with the panel reserved steel bar, and after the panel reserved steel bar is overlapped with the beam reserved steel bar, wet joint concrete is poured in the U-shaped groove. When the prestressed steel bar is tensioned on the ultra-high performance concrete panel according to the present invention, the panel is approximately in an axially compressed state, and the effect of applying prestress is very effective. Ordinary reinforced concrete π-beams are used in the compression zone of the combined structure, thereby reducing the overall cost of the structure.

Description

Technical Field

[0001] The present invention relates to the technical field of box beams, and in particular to a combined structure of a pre-tensioned UHPC plate and a concrete π-shaped beam and a construction method thereof. Background Art

[0002] Because small box girder structures have good torsional resistance, they are widely used in bridges between 25m and 40m. However, as the span increases, the weight of the small box girder structure also increases, which brings certain difficulties to transportation and lifting. Therefore, when the span increases to around 50m, it is necessary to adopt an open cross-section structure with a single web - a T-beam. However, the torsional resistance of T-beams is inevitably poor, and in order to ensure that the forces between the individual T-beams are shared, more cross-diaphragms are required, which brings certain difficulties to construction. In addition, as the span increases further, for example to 60m, the T-beam structure needs to adopt a higher beam height, and to increase torsional resistance, more requirements are placed on the beam spacing and cross-diaphragm arrangement. At this point, the T-beam is no longer suitable. Currently, the largest span used for T-beams is 50m. Therefore, for bridge spans over 40m, it is of certain practical significance to develop new prefabricated beam structures.

[0003] As understanding of ultra-high performance concrete (UHPC) deepens, more and more inventors are applying UHPC to main beam structures. UHPC possesses properties such as ultra-high strength, ultra-high toughness, and ultra-high durability. Applying UHPC to main beam structures can achieve lightweight structures while also increasing their service life. Consequently, various types of UHPC main beam structures have been invented. However, due to the high price of UHPC, a growing number of UHPC and conventional concrete combinations have emerged. Currently, a common combination of UHPC and conventional concrete is the combination of an UHPC U-beam and a conventional concrete top slab. This structure still presents certain problems. First, the usage of ultra-high performance concrete is still relatively high, and the web is also made of ultra-high performance concrete; second, regardless of whether the steel strands in the ultra-high performance concrete U-beam are pre-tensioned or post-tensioned, the U-beam is always an eccentrically compressed member, and generally a large eccentrically compressed member, that is, tensile stress will appear on the upper flange of the U-beam. When the tensile stress is large, in order to avoid cracking of the upper flange, it is still necessary to tension the steel strands at the upper flange position, that is, prestressed steel strands are also tensioned in the compression zone, so that the tensioning effect of the prestress is not effectively utilized; third, the construction of the beam, if factory assembly is used, will increase the weight of the member, resulting in certain difficulties in transportation and lifting, and limiting the increase in span; if an ordinary concrete top plate is cast on site, it is necessary to set up formwork supports on site, which brings a lot of trouble to the construction. Summary of the Invention

[0004] The purpose of the present invention is to propose a combined structure of pre-tensioned UHPC panels and concrete π-beams and a construction method thereof, so as to solve the technical problems existing in the background technology.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A combined structure of a pre-tensioned UHPC panel and a concrete π-shaped beam comprises a UHPC panel and an ordinary reinforced concrete π-shaped beam assembled with the UHPC panel to form a closed box beam structure, wherein the UHPC panel is provided with a pre-tensioned prestressed bundle, two groups of blocks are symmetrically arranged on both sides of the panel edge of the UHPC panel, and the two groups of blocks symmetrically form a U-shaped groove assembled with the ordinary reinforced concrete π-shaped beam, the U-shaped groove is vertically provided with a slab reserved steel bar, the web end of the ordinary reinforced concrete π-shaped beam is vertically provided with a beam reserved steel bar overlapped with the slab reserved steel bar, and after the slab reserved steel bar is overlapped with the beam reserved steel bar, wet joint concrete is poured in the U-shaped groove.

[0007] Furthermore, the prestressed bundle is a steel strand, a stress-relieving steel wire, a prestressed threaded steel bar or an FRP bundle.

[0008] Furthermore, the reserved steel bars of the plate are U-shaped steel bars, straight-end or pier-head steel bars.

[0009] Furthermore, the reserved steel bars of the beam are U-shaped steel bars, straight-end or pier-head steel bars.

[0010] Furthermore, the wet joint concrete is high-grade concrete above C60 or ultra-high performance concrete.

[0011] A construction method for a combined structure of a pre-tensioned UHPC panel and a concrete π-shaped beam comprises the following steps:

[0012] S1: Tension the prestressed tendons on the pre-tensioning pedestal, install the reinforcement cage of the UHPC panel, and set up the formwork;

[0013] S2: pouring ultra-high performance concrete, with reserved steel bars in the UHPC slab for connection with ordinary reinforced concrete π-beams;

[0014] S3: Remove the formwork and perform high-temperature curing on the UHPC panels. When the strength of the UHPC panels reaches the designed strength, release the prestressed tendons using the pre-tensioning method.

[0015] S4: Tie the steel skeleton of ordinary reinforced concrete π-beam and set up formwork;

[0016] S5: Cast ordinary reinforced concrete π-shaped beams, with reserved steel bars for connection with ultra-high performance concrete at the ends of the webs of the ordinary reinforced concrete π-shaped beams;

[0017] S6: Curing the ordinary reinforced concrete π-shaped beam until it reaches the design strength, completing the production of the π-shaped beam;

[0018] S7: transport the UHPC panels and ordinary reinforced concrete π-beams to the site respectively;

[0019] S8: Hoist the UHPC slab into place; hoist the ordinary reinforced concrete π-shaped beam and align it into the U-shaped groove; the reserved steel bars of the ordinary reinforced concrete π-shaped beam are arranged alternately with the reserved steel bars in the UHPC slab; pads can be placed in the U-shaped groove to support the upper ordinary reinforced concrete π-shaped beam;

[0020] S9: Pour wet joint concrete and wait until it reaches the design strength to complete the combination.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention proposes a combined structure of pre-tensioned ultra-high performance concrete slabs and conventional reinforced concrete π-shaped beams, and a construction method thereof. This combined structure places the pre-tensioned ultra-high performance concrete slabs in the tension zone. Leveraging the ultra-high compressive strength of ultra-high performance concrete, a larger number of prestressed steel strands are tensioned, thereby creating a larger reserve of prestress to resist increased loads later on. Furthermore, when the prestressed steel strands are tensioned on the ultra-high performance concrete slabs, the slabs are approximately in an axially compressed state, effectively applying prestress. Conventional reinforced concrete π-shaped beams are used in the compression zone of the combined structure, thereby reducing the overall cost of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 Schematic diagram of the structure of the UHPC board of the present invention;

[0025] Figure 2 This is a schematic structural diagram of a common reinforced concrete π-shaped beam according to the present invention;

[0026] Figure 3 This is a schematic diagram of the assembly structure of the UHPC board and ordinary reinforced concrete π-shaped beams of the present invention.

[0027] In the figure: 1. Prestressed tendons, 2. Slab reserved reinforcement, 3. Stop blocks, 4. UHPC slab, 5. Beam reserved reinforcement, 6. Ordinary reinforced concrete π-beam. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] like Figure 1-2 As shown, a combination structure of a pre-tensioned UHPC panel and a concrete π-beam comprises a UHPC panel 4 and an ordinary reinforced concrete π-beam 6 assembled with the UHPC panel 4 to form a closed box beam structure. The UHPC panel 4 is provided with a pre-tensioned prestressed bundle 1. Two groups of blocks 3 are symmetrically provided on both sides of the panel edge of the UHPC panel 4. The two groups of blocks symmetrically form a U-shaped groove assembled with the ordinary reinforced concrete π-beam 6, which is used as a template for post-cast wet joints. A slab reserved steel bar 2 is vertically provided in the U-shaped groove. A beam reserved steel bar 5 overlapped and connected to the slab reserved steel bar 2 is vertically provided at the web end of the ordinary reinforced concrete π-beam 6. After the slab reserved steel bar 2 is overlapped and connected to the beam reserved steel bar 5, wet joint concrete is poured in the U-shaped groove.

[0030] Specifically, as shown in the figure, the prestressed bundle 1 is a steel strand, a stress-relieving steel wire, a prestressed threaded steel bar, or an FRP bundle.

[0031] Specifically, as shown in the figure, the plate reserved steel bars 2 are U-shaped steel bars, straight-end or pier-head steel bars.

[0032] Specifically, as shown in the figure, the beam reserved steel bars 5 are U-shaped steel bars, straight-end or pier-head steel bars.

[0033] Specifically, as shown in the figure, the material of the post-cast wet joint can be high-grade concrete above C60, or ultra-high performance concrete; when the reserved steel bars are U-shaped, high-grade concrete above C60 should be used; when the reserved steel bars are straight-end or pier-head steel bars, ultra-high performance concrete should be used.

[0034] A construction method for a combined structure of a pre-tensioned UHPC panel and a concrete π-shaped beam comprises the following steps:

[0035] S1: Tensioning the prestressed tendons on the pre-tensioning pedestal, installing the reinforcement cage of the UHPC panel 4, and setting up the formwork;

[0036] S2: pouring ultra-high performance concrete, with reserved steel bars 2 in the UHPC slab 4 for connection with ordinary reinforced concrete π-shaped beams 6;

[0037] S3: De-moulding, high-temperature curing of the UHPC board 4, and release of prestressed tendons after the strength of the UHPC board 4 reaches the design strength;

[0038] S4: Tie the steel skeleton of the ordinary reinforced concrete π-shaped beam 6 and set up the formwork;

[0039] S5: Casting ordinary reinforced concrete π-shaped beam 6, with reserved beam reinforcement 5 for connection with ultra-high performance concrete at the end of the web of the ordinary reinforced concrete π-shaped beam 6;

[0040] S6: Curing the ordinary reinforced concrete π-shaped beam 6 until it reaches the design strength, completing the production of the π-shaped beam;

[0041] S7: transporting the UHPC slab 4 and the ordinary reinforced concrete π-shaped beam 6 to the site respectively;

[0042] S8: hoist the UHPC slab 4 into place; hoist the ordinary reinforced concrete π-shaped beam 6 and align the ordinary reinforced concrete π-shaped beam 6 into the U-shaped groove; the reserved steel bars of the ordinary reinforced concrete π-shaped beam 6 are arranged alternately with the reserved steel bars in the UHPC slab 4; a pad can be placed in the U-shaped groove to support the upper ordinary reinforced concrete π-shaped beam 6;

[0043] S9: Pour wet joint concrete and wait until it reaches the design strength to complete the combination.

[0044] The present invention proposes a combined structure of pre-tensioned ultra-high performance concrete slabs and conventional reinforced concrete π-shaped beams, and a construction method thereof. This combined structure places the pre-tensioned ultra-high performance concrete slabs in the tension zone. Leveraging the ultra-high compressive strength of ultra-high performance concrete, a larger number of prestressed steel strands are tensioned, thereby creating a larger reserve of prestress to resist increased loads later on. Furthermore, when the prestressed steel strands are tensioned on the ultra-high performance concrete slabs, the slabs are approximately in an axially compressed state, effectively applying prestress. Conventional reinforced concrete π-shaped beams are used in the compression zone of the combined structure, thereby reducing the overall cost of the structure.

[0045] The pre-tensioned UHPC slabs and conventional reinforced concrete π-beams were transported to the site separately and then connected using wet joints. This separate transportation reduced the weight of the components during transportation and hoisting, allowing for larger spans. The on-site wet joint casting eliminated the need for additional formwork, streamlining the construction process.

[0046] This composite structure is a closed box-type structure, which improves its torsional resistance compared to open sections such as T-beams and I-beams. Although closed, it is divided into two separate sections during fabrication and transportation. Both sections have open cross-sections, simplifying fabrication and facilitating demolding. Furthermore, transporting the two sections significantly reduces the component's weight and avoids the issue of span limitations due to beam weight. The two sections are also easily connected on site, eliminating the need for formwork and avoiding construction complications.

[0047] Compared with the traditional ultra-high performance concrete-ordinary concrete composite structure, this structure concentrates the ultra-high performance concrete material on the bottom plate of the composite component, that is, the tension zone of the composite structure; through the ultra-high compressive performance of ultra-high performance concrete, a large amount of prestress is reserved, so that it can withstand later loads, including the upper ordinary concrete π-shaped beam, secondary load and +- live load. In addition, since the prestressing is only applied in the bottom plate, the prestressing effect is more effective, which greatly improves the bearing capacity of the structure and has good economy.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0049] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A combined structure of pre-tensioned UHPC panels and concrete π-beams, characterized in that: The invention comprises a UHPC plate (4) and an ordinary reinforced concrete π-shaped beam (6) assembled with the UHPC plate (4) to form a closed box beam structure, wherein a prestressed beam (1) of a pre-tensioning method is arranged in the UHPC plate (4), two groups of stoppers (3) are symmetrically arranged on both sides of the plate edge of the UHPC plate (4), and the two groups of stoppers symmetrically form a U-shaped groove assembled with the ordinary reinforced concrete π-shaped beam (6), a plate reserved steel bar (2) is vertically arranged in the U-shaped groove, and a beam reserved steel bar (5) overlapped and connected with the plate reserved steel bar (2) is vertically arranged at the web end of the ordinary reinforced concrete π-shaped beam (6), and after the plate reserved steel bar (2) is overlapped and connected with the beam reserved steel bar (5), wet joint concrete is poured in the U-shaped groove; the plate reserved steel bar (2) is a U-shaped steel bar, a straight end or a pier head type steel bar; and the beam reserved steel bar (5) is a U-shaped steel bar, a straight end or a pier head type steel bar.

2. The combined structure of pre-tensioned UHPC panels and concrete π-beams according to claim 1, characterized in that: The prestressed bundle (1) is a steel strand or an FRP bundle.

3. The combined structure of pre-tensioned UHPC panels and concrete π-shaped beams according to claim 1, characterized in that: The wet joint concrete is high-grade concrete above C60.

4. A construction method for a combined structure of a pre-tensioned UHPC panel and a concrete π-beam according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: tensioning the prestressed tendons on the pre-tensioning pedestal, installing the reinforcement cage of the UHPC panel (4), and setting up the formwork; S2: pouring ultra-high performance concrete, with reserved steel bars (2) in the UHPC slab (4) for connection with ordinary reinforced concrete π-shaped beams (6); S3: removing the formwork, performing high temperature curing on the UHPC board (4), and releasing the prestressed tendons after the strength of the UHPC board (4) reaches the design strength; S4: Tie the steel frame of the ordinary reinforced concrete π-shaped beam (6) and set up the formwork; S5: Casting an ordinary reinforced concrete π-shaped beam (6), with a beam reserved steel bar (5) reserved at the end of the web of the ordinary reinforced concrete π-shaped beam (6) for connection with the ultra-high performance concrete; S6: Curing the ordinary reinforced concrete π-shaped beam (6) until it reaches the design strength, completing the production of the π-shaped beam; S7: transporting the UHPC board (4) and the ordinary reinforced concrete π-shaped beam (6) to the site respectively; S8: hoisting the UHPC plate (4) into place; hoisting the ordinary reinforced concrete π-shaped beam (6), aligning the ordinary reinforced concrete π-shaped beam (6) into the U-shaped groove; the reserved steel bars of the ordinary reinforced concrete π-shaped beam (6) and the reserved steel bars in the UHPC plate (4) are arranged in a staggered manner; a pad can be placed in the U-shaped groove to support the upper ordinary reinforced concrete π-shaped beam (6); S9: Pour wet joint concrete and wait until it reaches the design strength to complete the combination.

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