Continuous small box girder structure with composite section in negative moment area and its construction method

Abstract

The present invention discloses a continuous small box girder structure with a composite section in the negative moment area and its construction method, including precast NC small box girders, mid-span connection sections, and precast UHPC channel plates; the precast UHPC channel plates are located in the negative moment area of the continuous beam, an empty groove is provided in the channel plate, and concave and convex connecting pieces are provided at the webs. The present invention significantly improves the cracking moment and durability of the concrete in the negative moment area, avoids the shrinkage cracking problem of cast-in-place UHPC in the negative moment area, can adapt to the scenario where the thicknesses of the NC plate and the UHPC plate are inconsistent, eliminates the formwork erection during the casting of the joints between the UHPC webs, can adapt to precast small box girders of various lengths, and is convenient for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of civil engineering, and particularly relates to a continuous small box girder structure with a composite section in the negative moment area and a construction method thereof. Background Art

[0002] UHPC has the characteristics of high compressive and tensile strength, strong impermeability, and good durability. In recent years, UHPC has been used in the transverse connection of prefabricated NC bridges, newly built full-UHPC bridges, and UHPC bridge decks. The prefabricated NC bridge with UHPC transverse connection can eliminate the steel bar welding at the transverse connection and speed up the construction speed; the full-UHPC bridge has a lower beam height, which can reduce the route elevation; the UHPC bridge deck has a larger stiffness, which can solve the fatigue cracking problem of orthotropic steel bridge decks.

[0003] UHPC has shown good performance in the bridge fields where it is applied and improved the performance of bridge structures. When UHPC is used in the negative moment area of a continuous small box girder bridge, it can significantly enhance the durability of the negative moment area, increase the cracking moment of the negative moment area, and reduce the amount of prestressed tendons. However, there are still some problems when UHPC is used in the negative moment area of a continuous small box girder bridge, such as: the thickness of the UHPC bridge deck is different from that of the NC bridge deck, the shrinkage of UHPC is large, and when it is only used for the bridge deck, UHPC cannot maximize the cracking moment of the section. Therefore, it is urgent to find a structural method to solve the above problems and apply UHPC to the negative moment area of a continuous small box girder bridge. Summary of the Invention

[0004] The purpose of the present invention is to provide a continuous small box girder structure with a composite section in the negative moment area and a construction method thereof to solve the problems existing in the above-mentioned prior art. This structural form uses a precast UHPC trough plate in the negative moment area. The precast plate makes the thickness of the UHPC plate the same as that of the NC plate by opening a hollow groove in the middle, and reduces the amount of UHPC through the hollow groove; the precast UHPC trough plate can effectively increase the cracking moment of the negative moment area, reduce the amount of prestressed steel bars, and improve the durability of the structure. In addition, the concave connectors in the precast UHPC trough plate can be used as templates during construction to speed up the construction speed, and the size of the fixed precast UHPC trough plate can be adapted to the requirements of different small box girder lengths by adjusting the extending length of the connectors, which is convenient for industrial production.

[0005] To achieve the above object, the present invention provides the following solution: The present invention provides a continuous small box girder structure with a composite section in the negative moment area, including a precast NC small box girder, a mid-support connection section, and a precast UHPC trough plate;

[0006] The adjacent precast NC small box girders are connected into one body through the middle support connection section. The precast NC small box girder includes an NC plate and an NC trough girder formed by one-time casting. The NC plate is located in the positive moment area of the continuous small box girder. Reinforcement connectors are provided at the top of the NC trough girder in the area where the NC plate is not installed.

[0007] The NC trough girder and the precast UHPC trough plate are connected together through the reinforcement connectors arranged on the NC trough girder. The precast UHPC trough plates are connected to the NC plate and to each other between adjacent precast UHPC trough plates by the UHPC poured at the joints to form one body.

[0008] The precast UHPC trough plates include four types: type A precast UHPC trough plate, type B precast UHPC trough plate, type C precast UHPC trough plate, and type D precast UHPC trough plate. The NC trough girder can be connected to the multi-segment spliced trough plate structure composed of type A precast UHPC trough plates and type B precast UHPC trough plates, or can be connected to the full-length type D precast UHPC trough plate. The middle support connection section can be in the form of a combined section composed of cast-in-place NC and type C precast UHPC trough plates, or in the form of a full section of cast-in-place UHPC.

[0009] Both the type A precast UHPC trough plate and the type B precast UHPC trough plate include a UHPC hollow plate and a UHPC web. Concave connectors are used at the front and rear ends of the UHPC web of the type A precast UHPC trough plate. Convex connectors and concave connectors are respectively used at the front and rear ends of the UHPC web of the type B precast UHPC trough plate. The type C precast UHPC trough plate includes a UHPC solid plate and a UHPC web. Convex connectors are used at the front and rear ends of the UHPC web of the type C precast UHPC trough plate. The type D precast UHPC trough plate includes a UHPC hollow plate and a UHPC web. Concave connectors are used at the front and rear ends of the UHPC web of the type D precast UHPC trough plate.

[0010] Preferably, the concave connector is located outside the UHPC web. The inner wall width of the concave connector is the same as the width of the UHPC web. The length of the concave connector is 1.5 - 2.5 times the joint length of adjacent UHPC hollow plates. The convex connector is located inside the UHPC web. The width of the convex connector is 0.5 - 0.8 times the width of the UHPC web. The length of the convex connector is 0.3 - 1.3 times the joint length of adjacent UHPC hollow plates. The convex connector extends into the concave connector of the adjacent precast UHPC trough plate, and the UHPC web adjacent to the convex connector is in contact with the inner wall of the concave connector of the adjacent precast UHPC trough plate.

[0011] Preferably, the UHPC hollow slab is provided with an empty groove in the middle of the slab; the thickness of the UHPC hollow slab at the longitudinal edge of the beam is the same as that of the NC slab; the thickness of the UHPC solid slab is the same as that of the UHPC hollow slab at the longitudinal edge of the beam.

[0012] Preferably, the precast UHPC channel slab is provided with reserved holes for connectors; the steel bar connectors on the NC channel beam are placed in the reserved holes for connectors; the reserved holes for connectors are filled with UHPC.

[0013] Preferably, the joint between the precast UHPC channel slab and the NC slab is provided with joint steel bars; the joints between adjacent precast UHPC channel slabs are provided with joint steel bars.

[0014] The construction method of the continuous small box girder structure with a composite section in the negative moment area is applied to the continuous small box girder structure with a composite section in the negative moment area as described above, and includes the following steps:

[0015] 1) Produce precast NC small box girders and precast UHPC channel slabs in the factory according to the design dimensions;

[0016] 2) Place the precast UHPC channel slab in the designed position;

[0017] 3) Pour UHPC into the reserved holes for connectors and joints to form a simply supported small box girder;

[0018] 4) Erector the simply supported small box girder to the designed position and install the middle support connection section to form a continuous small box girder structure with a composite section in the negative moment area.

[0019] The present invention has achieved the following beneficial technical effects compared with the prior art:

[0020] 1. Compared with only laying UHPC on the bridge deck, using UHPC in some areas of the web can make full use of the tensile material properties of UHPC and improve the cracking moment in the negative moment area.

[0021] 2. Compared with the UHPC slab with equal thickness, the UHPC hollow slab can not only adapt to the thickness of the NC slab at the edge, but also reduce the consumption of UHPC material through the groove.

[0022] 3. The concave connectors arranged at the UHPC web can be used as the side formwork of the web during construction, which can speed up the construction speed. The shape and structure of the concave and convex connectors can also enhance the connection of the UHPC web. In addition, the penetration length of the connectors is adjustable, and the joint width between the precast UHPC slabs is variable, so that the precast UHPC channel slabs with the same size can adapt to different small box girder lengths, which is convenient for industrial production.

[0023] 4. Compared with the cast-in-place UHPC trough slab in the negative moment section, the precast UHPC trough slab is convenient for industrial production and can avoid the concrete cracking caused by the too long cast-in-place UHPC section.

[0024] 5. Compared with the NC bridge deck used in the negative moment area, the UHPC trough slab can enhance the resistance to environmental erosion from the bridge deck and improve the durability of the bridge.

[0025] In summary, the continuous small box girder structure with a composite section in the negative moment area of the present invention has a relatively high cracking moment in the negative moment area, good durability, low UHPC material consumption, and relatively convenient construction performance. Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 is a three-dimensional schematic diagram of a continuous small box girder structure with a composite section in the negative moment area;

[0028] Figure 2 is a three-dimensional schematic diagram of a precast NC small box girder;

[0029] Figure 3 is a three-dimensional top view of a Type B precast UHPC trough slab;

[0030] Figure 4 is a three-dimensional bottom view of a Type B precast UHPC trough slab;

[0031] Figure 5 is a three-dimensional top view of a Type C precast UHPC trough slab;

[0032] Figure 6 is a three-dimensional bottom view of a Type C precast UHPC trough slab;

[0033] Figure 7 is a three-dimensional schematic diagram of a continuous small box girder structure with a composite section in the negative moment area;

[0034] Figure 8 is a three-dimensional bottom view of a Type D precast UHPC trough slab;

[0035] Among them, 1 is a precast NC small box girder, 2 is the cast-in-place NC at the middle support, 3 is a precast UHPC trough plate of type A, 4 is a precast UHPC trough plate of type B, 5 is a precast UHPC trough plate of type C, 6 is an NC plate, 7 is an NC trough girder, 8 is a steel bar connector, 9 is a reserved hole for the connector, 10 is a concave connection, 11 is a convex connection, 12 is a UHPC web, 13 is a UHPC hollow plate, 14 is an empty trough, 15 is a UHPC solid plate, 16 is the steel bar at the joint, 17 is a precast UHPC trough plate of type D, and 18 is a cast-in-place UHPC connection section. Specific implementation manner

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] The purpose of the present invention is to provide a continuous small box girder structure with a composite section in the negative moment area and its construction method to solve the problems existing in the above-mentioned prior art. In this structural form, precast UHPC trough plates are used in the negative moment area. The precast plate makes the thickness of the UHPC plate the same as that of the NC plate by opening an empty trough in the middle, and reduces the UHPC consumption through the empty trough; the precast UHPC trough plate can effectively increase the cracking moment in the negative moment area, reduce the amount of prestressed tendons, and improve the durability of the structure. In addition, the concave connectors in the precast UHPC trough plate can be used as templates during construction to speed up the construction speed, and the fixed size of the precast UHPC trough plate can be adapted to the requirements of different small box girder lengths by adjusting the extending length of the connectors, which is convenient for industrial production.

[0038] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the drawings and specific implementation manners.

[0039] Embodiment 1

[0040] As Figure 1-6As shown in the figure, this embodiment provides a continuous small box girder structure with a composite section in the negative moment area, including a precast NC small box girder 1, a cast-in-place NC 2 at the middle support, a type-A precast UHPC trough plate 3, a type-B precast UHPC trough plate 4, and a type-C precast UHPC trough plate 5. Adjacent precast NC small box girders 1 are connected into one body through the cast-in-place NC 2 at the middle support. The NC trough girder 7 is connected to the type-A precast UHPC trough plate 3, the type-B precast UHPC trough plate 4, and the type-C precast UHPC trough plate 5 through steel bar connectors 8 arranged on the NC trough girder 7. At the joint between the type-A precast UHPC trough plate 3 and the NC plate 6, there is a joint steel bar 16. At the joints between the type-A precast UHPC trough plate 3 and the type-B precast UHPC trough plate 4, and between the type-B precast UHPC trough plate 4 and the type-C precast UHPC trough plate 5, there are joint steel bars 16. The type-A precast UHPC trough plate 3, the type-A precast UHPC trough plate 3 and the type-B precast UHPC trough plate 4, and the type-B precast UHPC trough plate 4 and the type-C precast UHPC trough plate 5 are connected into one body through UHPC grouted at the joints.

[0041] As Figure 2 shown, the precast NC small box girder 1 is composed of an NC plate 6 and an NC trough girder 7, and is formed by one-time casting; the NC plate 6 is located in the positive moment area of the continuous small box girder; at the top of the NC trough girder 7, there are steel bar connectors 8 for connection in the area where the NC plate 6 is not installed.

[0042] The precast UHPC trough plates include three types: type-A precast UHPC trough plate 3, type-B precast UHPC trough plate 4, and type-C precast UHPC trough plate 5. As Figures 3-4 shown, the type-B precast UHPC trough plate 4 includes a UHPC hollow plate 13 and a UHPC web 12. At the front and rear ends of the UHPC web 12 of the type-B precast UHPC trough plate 4, convex connectors 11 and concave connectors 10 are respectively adopted. The type-A precast UHPC trough plate 3 is similar to the type-B precast UHPC trough plate 4, and includes a UHPC hollow plate 13 and a UHPC web 12. At the front and rear ends of the UHPC web 12 of the type-A precast UHPC trough plate 3, concave connectors 10 are adopted.

[0043] As Figure 4As shown in the figure, the UHPC hollow slab 13 is provided with a hollow groove 14 in the middle of the slab, which can effectively reduce the consumption of UHPC materials; the thickness of the UHPC hollow slab 13 at the longitudinal edge of the beam is the same as that of the NC slab 6, which can adapt to the relatively thick NC slab without sudden change in cross-sectional shape. The B-type precast UHPC channel slab 4 is provided with a reserved hole 9 for the connector; the steel bar connector 8 on the NC channel beam 7 is placed in the reserved hole 9 for the connector; the reserved hole 9 for the connector is filled with UHPC. The concave connector 10 is located outside the UHPC web 12, the inner wall width of which is the same as the width of the UHPC web 12, and its length is 1.5 times the length of the joint between adjacent UHPC hollow slabs 13. The concave connector can be used as a formwork when pouring the joint of the UHPC web 12, simplifying the construction process. The convex connector 11 is located inside the UHPC web 12, the width of which is 0.8 times the width of the UHPC web 12, and its length is 0.5 times the length of the joint between adjacent UHPC hollow slabs 13. The convex connector 11 extends into the concave connector 10 of the adjacent precast UHPC channel slab, and the UHPC web 12 adjacent to the convex connector 11 is in contact with the inner wall of the concave connector 10 of the adjacent precast UHPC channel slab.

[0044] As Figure 5 , 6 shown, the C-type precast UHPC channel slab 5 includes a UHPC solid slab 15 and a UHPC web 12, and the front and rear ends of the UHPC web 12 adopt convex connectors 11. The thickness of the UHPC solid slab 15 is the same as the thickness of the UHPC hollow slab 13 at the longitudinal edge of the beam.

[0045] The construction method of the continuous small box girder structure with a composite cross-section in the negative moment area includes the following steps:

[0046] 1) Produce precast NC small box girders 1, A-type precast UHPC channel slabs 3, B-type precast UHPC channel slabs 4, and C-type precast UHPC channel slabs 5 in the factory according to the design dimensions;

[0047] 2) Place the A-type precast UHPC channel slab 3 and the B-type precast UHPC channel slab 4 at the designed positions;

[0048] 3) Pour UHPC into the reserved holes 9 for the connectors and the joints to form a simply supported small box girder;

[0049] 4) Erect the simply supported small box girder to the designed position, pour the cast-in-place NC2 at the middle support, and after the concrete strength reaches the designed strength, install the C-type precast UHPC channel slab 5, and pour UHPC into the reserved holes 9 for the connectors and the joints to form a continuous small box girder structure with a composite cross-section in the negative moment area.

[0050] Example 2

[0051] As Figure 7As shown in the figure, this embodiment provides a continuous small box girder structure with a composite cross-section in the negative moment area. Different from the previous embodiment, in this embodiment, the precast segment of the negative moment uses a D-shaped precast UHPC trough plate 17 instead of the multi-segment precast plates composed of the A-shaped precast UHPC trough plate 3 and the B-shaped precast UHPC trough plate 4, as Figure 8 shown. The combined cross-section form of the mid-support connection segment composed of the cast-in-place NC2 at the mid-support and the C-shaped precast UHPC trough plate 5 is changed to the cast-in-place UHPC connection segment 18.

[0052] The construction method of the continuous small box girder structure with a composite cross-section in the negative moment area includes the following steps:

[0053] 1) Produce precast NC small box girders 1 and D-shaped precast UHPC trough plates 17 in the factory according to the design dimensions;

[0054] 2) Place the D-shaped precast UHPC trough plate 17 at the designed position;

[0055] 3) Pour UHPC into the reserved holes 9 of the connectors and the joints to form a simply supported small box girder;

[0056] 4) Erector the simply supported small box girder to the designed position, cast the cast-in-place UHPC connection segment 18, and form a continuous small box girder structure with a composite cross-section in the negative moment area after the concrete strength reaches the designed strength.

[0057] It should be noted that for those skilled in the art, obviously, the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention, and any reference signs in the claims should not be regarded as limiting the claims involved.

[0058] Specific examples are used in the present invention to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. The continuous small box girder structure with a composite section is adopted in the negative moment area, and its characteristics are as follows: It includes precast NC small box girders, mid - support connection segments and precast UHPC trough plates; Adjacent precast NC small box girders are connected into one body through mid - support connection segments. The precast NC small box girder includes an NC plate and an NC trough beam formed by one - time casting. The NC plate is located in the positive moment area of the continuous small box girder. Reinforcement connectors are provided at the top of the NC trough beam in the area where the NC plate is not installed; The NC trough beam and the precast UHPC trough plate are connected together through the reinforcement connectors arranged on the NC trough beam. The precast UHPC trough plate and the NC plate, as well as adjacent precast UHPC trough plates, are connected into one body through UHPC grouted at the joints; The precast UHPC trough plate includes four types: Type A precast UHPC trough plate, Type B precast UHPC trough plate, Type C precast UHPC trough plate and Type D precast UHPC trough plate. The NC trough beam can be connected to the multi - segment spliced trough plate structure composed of Type A precast UHPC trough plate and Type B precast UHPC trough plate, or can also be connected to the full - length Type D precast UHPC trough plate. The mid - support connection segment can be in the form of a combined section composed of cast - in - place NC and Type C precast UHPC trough plate, or can also be in the form of a full - section of cast - in - place UHPC; Both the Type A precast UHPC trough plate and the Type B precast UHPC trough plate include a UHPC hollow plate and UHPC webs. Concave connectors are used at the front and rear ends of the UHPC webs of the Type A precast UHPC trough plate. Convex connectors and concave connectors are respectively used at the front and rear ends of the UHPC webs of the Type B precast UHPC trough plate. The Type C precast UHPC trough plate includes a UHPC solid plate and UHPC webs. Convex connectors are used at the front and rear ends of the UHPC webs of the Type C precast UHPC trough plate. The Type D precast UHPC trough plate includes a UHPC hollow plate and UHPC webs. Concave connectors are used at the front and rear ends of the UHPC webs of the Type D precast UHPC trough plate; The UHPC hollow plate is provided with an empty groove in the middle of the plate; the thickness of the UHPC hollow plate at the longitudinal edge of the beam is the same as the thickness of the NC plate; the thickness of the UHPC solid plate is the same as the thickness of the UHPC hollow plate at the longitudinal edge of the beam; the precast UHPC trough plate is provided with reserved holes for connectors; the reinforcement connectors on the NC trough beam are placed in the reserved holes for connectors; UHPC is grouted in the reserved holes for connectors; The concave connector is located outside the UHPC web. The inner wall width of the concave connector is the same as the width of the UHPC web. The length of the concave connector is 1.5 - 2.5 times the joint length of adjacent UHPC hollow plates; the convex connector is located inside the UHPC web. The width of the convex connector is 0.5 - 0.8 times the width of the UHPC web. The length of the convex connector is 0.3 - 1.3 times the joint length of adjacent UHPC hollow plates; the convex connector extends into the concave connector of the adjacent precast UHPC trough plate, and the UHPC web adjacent to the convex connector is in contact with the inner wall of the concave connector of the adjacent precast UHPC trough plate.

2. The continuous small box girder structure with a composite section in the negative moment area according to claim 1, characterized in that: Reinforcing bars are provided at the joints between the precast UHPC channel slabs and the NC slabs; reinforcing bars are provided at the joints between adjacent precast UHPC channel slabs.

3. Construction method of continuous small box girder structure with composite section in negative moment area, applied to the continuous small box girder structure with composite section in negative moment area described in any one of claims 1-2, characterized in that It includes the following steps: 1) Produce precast NC small box girders and precast UHPC channel slabs in the factory according to the design dimensions; 2) Place the precast UHPC channel slabs in the designed positions; 3) Pour UHPC into the reserved holes of the connectors and the joints to form simply supported small box girders; 4) Erector the simply supported small box girders to the designed positions, and install the mid-support connection sections to form a continuous small box girder structure with a composite section in the negative moment area.

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