Prefabricated bridge piers using ultra-high performance concrete in complex stress areas and their construction methods

Abstract

The present invention discloses a prefabricated bridge pier using ultra-high performance concrete in a complex stress-bearing area, including an upper section, a middle section and a lower section, wherein the upper section and the lower section both include an ordinary concrete inner core and an UHPC (ultra-high performance concrete) outer core arranged outside the ordinary concrete inner core, the middle section is an ordinary reinforced concrete section, the lower end of the upper section and the upper end of the lower section are both provided with reserved longitudinal stress-bearing steel bars, the reserved longitudinal stress-bearing steel bars extend into the middle section and are connected to the longitudinal stress-bearing steel bars in the middle section, and the upper end of the upper section and the lower end of the lower section are both provided with reserved connectors. The present invention further discloses a construction method for the above-mentioned prefabricated bridge pier, including the steps of: S1, prefabricating an upper section and a lower section; S2, prefabricating a middle section and connecting the middle section and the lower section; S3, connecting the upper section and the middle section. The present invention has the advantages of good stress-bearing performance, good ductility, durability and economy.

Description

Technical Field

[0001] The invention relates to a bridge structure and a construction method thereof, and in particular to a prefabricated bridge pier using ultra-high performance concrete in a complex stress-bearing area and a construction method thereof. Background Art

[0002] Urban land is becoming increasingly scarce, and overpasses that take up space have been widely used. In order to reduce the space occupied under the bridge and increase the aesthetics, overpasses mostly use single-column piers. However, the torsional performance of this type of single-column pier continuous beam is poor, and it is easy to cause the bridge to overturn under eccentric load. In addition, bridge bearings have always been the weak link in the seismic performance of the bridge structure system. In all previous destructive earthquakes, earthquake damage to the bearings is common. Rigid frame bridges eliminate the bearings and connect the main beam and piers together, which can effectively improve the torsional performance of the main beam and avoid overturning damage and beam drop damage under earthquake action.

[0003] The rigid frame bridge connects the main bridge and the piers together. The longitudinal action of the main beam (including shrinkage creep, temperature change, braking force of the car, etc.) will be constrained by the piers. The piers of the rigid frame bridge are not only compressed, but also bent and torsion. Therefore, the connection between the piers and the beam body, and the piers and the abutments will be the most complex sections. Under the action of earthquakes, the forces on the piers of rigid frame bridges will be more complex.

[0004] The tensile strength of conventional concrete is about 1 / 10 of its compressive strength, so the concrete on the tensile side of a flexural member is prone to cracking. The tensile strength of ultra-high performance concrete (UHPC) is much greater than that of ordinary concrete, and it has the advantages of high ductility and high durability. Using ultra-high performance concrete for the piers of rigid frame bridges can effectively improve the stress of the piers, reduce the development of cracks, and improve the ductility and durability of the piers. UHPC has superior performance, but it is expensive, about 10 times the price of ordinary concrete. If UHPC is used on all piers, the piers will not have an economic advantage. In addition, the current labor costs are expensive, the on-site construction of concrete is noisy and dusty, and has a great impact on the environment, so the country vigorously promotes prefabricated components. However, the current prefabrication and assembly technology at home and abroad is mainly concentrated on the upper structure of building construction or bridges, and the actual application of prefabricated components for lower structures such as piers is not common. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a prefabricated bridge pier using ultra-high performance concrete in a complex stress-bearing area with good stress-bearing performance, good ductility, durability and economy.

[0006] The present invention further provides a construction method for prefabricated bridge piers using ultra-high performance concrete in the above-mentioned complex stress-bearing area.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A prefabricated bridge pier using ultra-high performance concrete in a complex stress-bearing area comprises an upper section, a middle section and a lower section, wherein the upper section and the lower section both comprise an ordinary concrete inner core and a UHPC outer core arranged outside the ordinary concrete inner core, the middle section is an ordinary reinforced concrete section, the lower end of the upper section and the upper end of the lower section are both provided with reserved longitudinal stress-bearing steel bars, the reserved longitudinal stress-bearing steel bars extend into the middle section and are connected to the longitudinal stress-bearing steel bars in the middle section, and the upper end of the upper section and the lower end of the lower section are both provided with reserved connecting pieces.

[0009] As a further improvement of the above technical solution:

[0010] The lengths of the upper segment and the lower segment are greater than or equal to 1 m, and the thickness of the UHPC outer core is greater than or equal to 10 cm.

[0011] If the diameter of the longitudinal stress-bearing steel bars is d, the length of the reserved longitudinal stress-bearing steel bars is greater than or equal to 33d, the length of the reserved longitudinal stress-bearing steel bars in the upper segment or the lower segment is ≥8d, and the length of the reserved longitudinal stress-bearing steel bars extending into the middle segment is greater than or equal to 25d.

[0012] The reserved connecting piece is a reserved sleeve.

[0013] The ordinary concrete inner core is ordinary concrete with a strength not less than C30.

[0014] A construction method for the above-mentioned prefabricated bridge piers using ultra-high performance concrete in the complex stress-bearing area comprises the following steps:

[0015] S1. Prefabricate upper and lower segments:

[0016] S1.1. Assemble the upper and lower segment formworks and install the reserved longitudinal stress reinforcement and reserved connectors;

[0017] S1.2, pouring UHPC of the upper and lower segments, curing and demoulding;

[0018] S1.3, pouring ordinary concrete of the lower section and curing and removing the formwork;

[0019] S2, Prefabricated middle section:

[0020] S2.1. Assemble the middle segment formwork on the top surface of the lower segment and install the steel cage. The lower end of the steel cage overlaps the reserved longitudinal stress reinforcement of the lower segment. The height of the middle segment formwork is h3, h3>h1, where h1 is the design height of the middle segment;

[0021] S2.2, pouring ordinary concrete in the middle section for the first time, the first pouring height is h1-h2, where h2 is preferably greater than or equal to the length of the reserved longitudinal stress-bearing steel bars in the upper section extending into the middle section;

[0022] S3, connect the upper segment and the middle segment:

[0023] S3.1. Lift the UHPC outer core of the upper segment and turn it 180°, then insert it into the formwork of the middle segment. The reserved longitudinal stress-bearing steel bars of the upper segment are overlapped with the upper end of the steel cage.

[0024] S3.2, the second pouring of ordinary concrete in the middle section, the second pouring height is h2;

[0025] S3.3, pouring ordinary concrete of the upper section and curing;

[0026] S3.4. Remove the lifting device of the upper section and the formwork of the middle section.

[0027] Compared with the prior art, the advantages of the present invention are as follows: the prefabricated piers of the complex stress-bearing area disclosed in the present invention adopt ultra-high performance concrete, including an upper segment, a middle segment and a lower segment, wherein the upper segment and the lower segment of the complex stress-bearing area are both double-layer structures of a UHPC outer core combined with an ordinary concrete inner core, and the middle segment adopts ordinary reinforced concrete. The UHPC outer core utilizes its good tensile and deformation properties to greatly improve the stress-bearing performance of the complex stress-bearing area of ​​the pier, which can effectively reduce the amount of steel used in the structure, reduce the occurrence and development of cracks, increase the ductility and seismic resistance of the pier, and provide a certain hoop effect for the ordinary concrete in the inner core, thereby improving the compressive strength of ordinary concrete; UHPC is used only in the complex stress-bearing area, so that the prefabricated pier has better economy at the same time, and the prefabricated structure makes the construction and installation of the pier body more convenient and the quality is more reliable.

[0028] The invention discloses a construction method for prefabricated bridge piers using ultra-high performance concrete in complex stress-bearing areas. The UHPC outer core of the upper segment and the UHPC outer core of the lower segment are manufactured simultaneously, and ordinary concrete on the upper portion of the middle segment and ordinary concrete on the upper segment are poured continuously, which can effectively reduce the number of joints and seams and quickly and conveniently complete the manufacture of the prefabricated bridge piers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic structural diagram of a prefabricated bridge pier using ultra-high performance concrete in a complex stress-bearing area of ​​the present invention.

[0030] Figure 2 It is a structural schematic diagram of the upper segment and the lower segment in the present invention.

[0031] Figure 3 It is a structural schematic diagram of the templates of the upper section and the lower section of the construction method of the present invention.

[0032] Figure 4 It is a structural schematic diagram of the positioning steel bars of the upper section and the lower section of the construction method of the present invention.

[0033] Figure 5 It is a structural schematic diagram of the middle section of the construction method of the present invention.

[0034] The numbers in the figure represent: 1. upper segment; 2. middle segment; 3. lower segment; 4. ordinary concrete inner core; 5. UHPC outer core; 6. reserved longitudinal stress-bearing steel bars; 7. longitudinal stress-bearing steel bars; 8. reserved connectors; 9. upper and lower segment formwork; 91. outer formwork; 92. inner formwork; 93. bottom formwork; 94. positioning steel bars; 95. sleeve positioning plate; 10. steel cage; 11. middle segment formwork. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Figures 1 to 5 An embodiment of the prefabricated bridge pier using ultra-high performance concrete in a complex stress-bearing area of ​​the present invention and a construction method thereof is shown. The specific construction process is as follows:

[0037] (1) The upper and lower segment templates 9 of the UHPC outer core 5 of the upper segment 1 and the lower segment 3 are respectively erected and installed. First, the inner template 92 of the UHPC outer core 5 is erected on the flat steel bottom template 93. The inner template 92 is composed of two semicircular steel plates; the outer template 91 is composed of two semicircular steel plates. During assembly, it is necessary to ensure that the inner template 92 and the outer template 91 are stable and spliced ​​in place. Of course, in other embodiments, as the cross-section of the bridge pier changes, the upper and lower segment templates 9 are not limited to cylindrical shapes, but can also be conventional pier column forms such as rectangles and ellipses.

[0038] (2) Reserved sleeve erection. The reserved sleeve of the upper segment 1 is used to connect with the cap beam or main beam after being transported to the construction site, and the reserved sleeve of the lower segment 3 is connected with the reserved steel bars of the cap. The cap beam (or main beam) and the cap can be prefabricated or constructed by cast-in-place method. The sleeve positioning plate 95 is installed on the bottom template 93 of the upper segment 1 and the lower segment 3. The reserved hole position on the sleeve positioning plate 95 is determined according to the distribution of the load-bearing steel bars of the connecting components such as the cap beam (or main beam) and the cap. The reserved sleeve is inserted into the hole position of the sleeve positioning plate 95. The length of the reserved sleeve is taken as 10d1 according to the specification JGJ355-2015 (d1 is the diameter of the load-bearing steel bars in the connecting component). After the overall construction of the prefabricated pier is completed and transported to the construction site, the sleeve grouting method can be used to connect with the connecting components such as the cap beam (or main beam) and the cap. The sleeve grouting method has a relatively mature construction process and will not be described in detail. Of course, in other embodiments, other forms of reserved connection members 8 may be used to achieve reliable connection between the prefabricated piers and the abutments and cap beams (or main beams).

[0039] (3) The reserved longitudinal stress-bearing steel bars 6 are erected. Positioning steel bars 94 are erected on the top of the upper and lower segment templates 9. In this embodiment, the positioning steel bars 94 include an equilateral triangle and a circumscribed circle of the outer periphery of the equilateral triangle, which has a simple structure and reliable positioning. The reserved longitudinal stress-bearing steel bars 6 are welded on the positioning steel bars 94. The position of the reserved longitudinal stress-bearing steel bars 6 is consistent with the longitudinal stress-bearing steel bars 7 of the middle segment 2 and is arranged according to design requirements. In this embodiment, the length of the reserved longitudinal stress-bearing steel bars 6 is 45d (d is the diameter of the longitudinal stress-bearing steel bars 7 of the middle segment 2), of which 15d of the length extends into the upper segment 1 and the lower segment 3; 30d of the length extends out of the top surface of the upper segment 1 and the lower segment 3 to overlap with the longitudinal stress-bearing steel bars 7 of the middle segment 2. Of course, in other embodiments, the total length of the reserved longitudinal stress-bearing steel bars 6 can also be adjusted appropriately.

[0040] (4) Casting and curing of UHPC outer core 5. Pour the stirred UHPC from the upper side of the inner formwork 92 and the outer formwork 91 at a uniform and slow speed to form the UHPC outer core 5. After the casting and vibration are completed, cover with a film and let it stand for 24 hours for natural curing. After the UHPC outer core 5 is formed, demould. Cover the UHPC outer core 5 component after demoulding with an insulation film and steam cure for 48 hours.

[0041] (5) Casting of the ordinary concrete inner core 4 of the lower segment 3. After the curing of the UHPC outer core 5 of the lower segment 3 is completed, ordinary concrete with a strength not less than C30 (the specific strength grade of ordinary concrete is determined according to the design requirements, and C40 in this embodiment) is cast inward, and then naturally cured. The ordinary concrete inner core 4 of the upper segment 1 is not cast in this construction stage.

[0042] The middle section 2 is a common reinforced concrete member. The structural dimensions of the middle section 2 are set according to the design requirements, and the height h1 is determined by the design length of the pier column h-4m (the recommended length of the upper section 1 and the lower section 3 is 2m).

[0043] Because of the connection with the upper segment 1 and the lower segment 3, its construction process is different from that of ordinary concrete components. The specific construction process is as follows:

[0044] (1) Lower segment 3 is placed in place. The lower segment 3, which has been cast with ordinary concrete core 4 and cured, is hoisted onto the pier precast platform.

[0045] (2) Set up the middle section formwork 11 and the steel cage 10. Set up the middle section formwork 11 on the top surface of the lower section 3. The height of the middle section formwork 11 is h3, and the height above the middle section 2 is 25 cm. Tie and weld the longitudinal stress-bearing steel bars 7 and spiral steel bars according to the design requirements to form the steel cage 10, and hoist the steel cage 10 into the middle section formwork 11 and install it in place. Pay attention to the overlap between the longitudinal stress-bearing steel bars 7 of the middle section 2 and the reserved longitudinal stress-bearing steel bars 6 of the lower section 3. The overlap length is 30d.

[0046] (3) Pouring ordinary concrete for middle section 2. The ordinary concrete for middle section 2 is poured in two times according to the conventional pouring method. The first pouring height is 75 cm lower than the design height of middle section 2.

[0047] (4) The upper segment 1 is in place. The UHPC outer core 5 of the upper segment 1 that has been cured is lifted and turned 180 degrees. The reserved longitudinal stress reinforcement 6 with a length of 30d is vertically downward. The upper segment 1 is inserted into the raised part of the middle segment formwork 11, and attention is paid to the overlap between the reserved longitudinal stress reinforcement 6 and the longitudinal stress reinforcement 7 of the middle segment 2. The lifting device is not removed, and the verticality and plane position of the upper segment 1 are ensured.

[0048] (5) Ordinary concrete pouring of middle section 2. The second pouring of ordinary concrete of middle section 2 is carried out until it is flush with the designed height. The concrete height of this section is 75 cm.

[0049] (6) Pour the core concrete of the upper segment.

[0050] (7) Curing and demoulding. After pouring is completed, the integral pier is naturally cured. When the concrete reaches a certain strength, the lifting device of the upper segment 1 is removed and the formwork 11 of the middle segment is removed.

[0051] (8) Storage and preservation of bridge piers. Prefabricated and cured bridge piers do not require special preservation and can be stacked on a flat site with the number of layers not exceeding three.

[0052] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. A construction method for prefabricated bridge piers using ultra-high performance concrete in complex stress-bearing areas, characterized in that: A prefabricated bridge pier using ultra-high performance concrete in a complex stress-bearing area comprises an upper segment (1), a middle segment (2) and a lower segment (3), wherein the upper segment (1) and the lower segment (3) both comprise an ordinary concrete inner core (4) and an UHPC outer core (5) arranged outside the ordinary concrete inner core (4), wherein the middle segment (2) is an ordinary reinforced concrete segment, wherein the lower end of the upper segment (1) and the upper end of the lower segment (3) are both provided with reserved longitudinal stress-bearing steel bars (6), wherein the reserved longitudinal stress-bearing steel bars (6) extend into the middle segment (2) and are connected to the longitudinal stress-bearing steel bars (7) in the middle segment (2), wherein the upper end of the upper segment (1) and the lower end of the lower segment (3) are both provided with reserved connecting pieces (8), and the construction method comprises the following steps: S1, prefabricated upper segment (1) and lower segment (3): S1.1, assemble the upper and lower segment formwork (9), and install the reserved longitudinal stress-bearing steel bars (6) and the reserved connection pieces (8); S1.2, pouring the UHPC of the upper segment (1) and the lower segment (3), curing and removing the formwork; S1.3, pouring ordinary concrete of the lower section (3), curing and removing the formwork; S2, prefabricated middle segment (2): S2.

1. Assemble the middle segment template (11) on the top surface of the lower segment (3) and install the steel cage (10). The lower end of the steel cage (10) overlaps the reserved longitudinal stress-bearing steel bars (6) of the lower segment (3). The height of the middle segment template (11) is h3, h3>h1, where h1 is the design height of the middle segment (2); S2.2, first pouring of ordinary concrete in the middle section (2), first pouring height h1-h2; S3, connect the upper segment (1) and the middle segment (2): S3.

1. Lift the UHPC outer core (5) of the upper segment (1) and turn it 180°, then insert it into the middle segment formwork (11), and overlap the reserved longitudinal stress-bearing steel bars (6) of the upper segment (1) with the upper end of the steel cage (10); S3.2, pouring the ordinary concrete of the middle section (2) for the second time, the second pouring height is h2; S3.3, pouring ordinary concrete of the upper section (1) and curing; S3.

4. Remove the lifting device of the upper segment (1) and the formwork (9) of the middle segment (2).

2. The construction method of prefabricated bridge piers using ultra-high performance concrete in complex stress-bearing areas according to claim 1 is characterized by: The lengths of the upper segment (1) and the lower segment (3) are greater than or equal to 1 m, and the thickness of the UHPC outer core (5) is greater than or equal to 10 cm.

3. The construction method of prefabricated bridge piers using ultra-high performance concrete in complex stress-bearing areas according to claim 1 or 2, characterized in that: If the diameter of the longitudinal stress-bearing steel bar (7) is d, the length of the reserved longitudinal stress-bearing steel bar (6) is greater than or equal to 33d, the length of the reserved longitudinal stress-bearing steel bar (6) located in the upper segment (1) or the lower segment (3) is ≥8d, and the length of the reserved longitudinal stress-bearing steel bar (6) extending into the middle segment (2) is greater than or equal to 25d.

4. The construction method of prefabricated bridge piers using ultra-high performance concrete in complex stress-bearing areas according to claim 3 is characterized by: The reserved connecting piece (8) is a reserved sleeve.

5. The construction method of prefabricated bridge piers using ultra-high performance concrete in complex stress-bearing areas according to claim 1 or 2, characterized in that: The ordinary concrete inner core (4) is ordinary concrete with a strength not less than C30.

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