UHPC assembled box culvert

Abstract

The utility model discloses a kind of UHPC assembled box culverts, this novel UHPC box culvert includes using coarse aggregate UHPC prefabrication, with waffle upper and lower bottom plate and web plate to form box, and set mortise and tenon joint, it makes full use of UHPC high compressive strength, waffle web light, high shear yield strength characteristics, and because of using UHPC, with superior toughness and ductility, overall deformation synergy, to improve the stability of structure, strength and material use efficiency.Simultaneously, because UHPC material is used, section size can be further reduced, material usage and overall weight are reduced, and field construction period is shortened.Moreover, because of using coarse aggregate UHPC material, it has significant potential advantages in engineering cost, durability and maintenance cost reduction, and has important economic benefits and social benefits.

Description

Technical Field

[0001] This utility model relates to the fields of ultra-high performance concrete with coarse aggregate, bridge engineering, and steel-concrete composite structures, and more specifically to a UHPC prefabricated box culvert. Background Technology

[0002] Traditional reinforced concrete composite box culvert structures are characterized by concrete bearing axial pressure and steel reinforcement skeleton bearing bending moment as the main stress characteristics. They have advantages such as high stiffness, high load-bearing capacity and beautiful appearance, and are one of the most widely used structural forms in current box culvert projects.

[0003] However, traditional NC composite box culverts still have some significant defects in construction and use: First, the concrete pouring operation of the bottom slab is inconvenient, especially the narrow space at the junction of the web and the bottom slab, making it difficult to guarantee the quality of concrete pouring; Second, the composite beam bridge deck is prone to cracking under external loads, especially in the positive bending moment zone, which seriously affects the stiffness, bearing capacity and durability of the structure; Third, the outer surface design of the box culvert is unreasonable, resulting in little interaction between the box culvert and the backfill soil. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of this utility model is to provide a new type of precast UHPC box culvert and its construction method. The precast UHPC box culvert and its construction method are conducive to facilitating the insertion and installation of the front and rear box culvert sections, reducing the self-weight of the box culvert, and improving its toughness and ductility.

[0005] The technical solution adopted by this utility model to solve its technical problem is:

[0006] A novel prefabricated box culvert with coarse aggregate UHPC is characterized in that: the box culvert includes a waffle-shaped upper top plate, a lower bottom plate, and web plates located on both sides of the upper top plate and the lower bottom plate; the front end of the box culvert section is provided with a tenon, and the rear end of the box culvert section is provided with a tenon that can be inserted with the tenon; the upper top plate, the lower bottom plate, the web plates, and the tenons are made of UHPC material.

[0007] Preferably, the upper top plate has a reserved maintenance opening in the middle.

[0008] Preferably, the upper top plate has several pre-embedded integrated lifting lugs located in the middle of the reserved maintenance opening.

[0009] Preferably, the aforementioned web plate is provided with a plurality of rectangular grooves arranged in a matrix.

[0010] Preferably, the corner node area of ​​the box culvert is provided with a reinforcing steel frame. The reinforcing steel frame includes the starting section steel bars installed at both ends of the box culvert and multiple longitudinal reinforcing bars connecting the starting section steel bars at both ends. The starting section steel bars are formed by splicing three sets of structural bars to form a triangle. Each set of structural bars consists of multiple parallel steel bars and structural stirrups spaced on the parallel steel bars.

[0011] Preferably, the front and rear end faces of the box culvert are parallel to each other or form an angle, and a waterproof rubber gasket is provided at the connection between the tenon and the tenon of the previous box culvert section.

[0012] Preferably, the box culverts mentioned above are prefabricated in the factory or cast on site.

[0013] Preferably, the above-mentioned UHPC material mix ratio (kg / m) 3 )as follows:

[0014]

[0015] The construction method of this novel precast UHPC box culvert is characterized by the following steps:

[0016] a. Based on the usage requirements and composition, conduct compatibility testing of UHPC containing coarse aggregate and determine its mix proportion;

[0017] b. Weld the internal steel mesh of the box culvert, and weld the pre-embedded integrated lifting lugs to the steel mesh of the top plate. Set up a reserved maintenance opening at the position of the top plate. Note that the steel mesh around the maintenance opening should be densified and the steel mesh should be formed in one piece.

[0018] c. Assemble the steel formwork and check its sealing performance. Then, pour the bottom slab, web slab, and top slab in sequence.

[0019] d. The new UHPC box girder was steam-cured for 3 days, and the strength of the test blocks cured at the same time was checked;

[0020] e. Once the UHPC strength reaches 30% of the design strength, the steel formwork can be removed. Check the box for cracks and voids, repair them with UHPC mortar, and at the same time grind the burrs on the inner and outer box steel fibers.

[0021] In step c, the steel formwork for the box culvert is made of pressed steel plate to facilitate the formation of waffle-shaped panels during casting; in step b, the top plate is designed with openings, which can be used for internal inspection of the combined box culvert.

[0022] This utility model of a novel precast UHPC box culvert and its construction method has the following main advantages compared with the prior art:

[0023] 1. The box culverts in this application all adopt a waffle design, which is conducive to reducing self-weight, has a higher load-bearing efficiency than the traditional rectangular section, and has a good load distribution capacity. In addition, the UHPC material used has high toughness and ductility, and the whole can deform in a coordinated manner, thus slowing down cracking.

[0024] 2. The box culvert in this application has a simple structure, is easy to construct, and is relatively lightweight, making it convenient to transport and erect on site, which can significantly shorten the on-site construction time.

[0025] 3. The box culvert in this application is integrally cast using UHPC containing coarse aggregate, which has the characteristics of high rigidity and high bearing capacity. It can ensure the overall performance of the box culvert, giving it sufficient torsional stiffness to reduce the overall torsional distortion effect. It has clear stress performance, high versatility and convenient construction. In addition, the box culvert uses UHPC material with good durability, which can effectively reduce bridge maintenance costs and improve the bridge's life cycle, increasing its service life and traffic capacity.

[0026] 4. The rectangular groove shape on the outer surface of the box culvert in this application is conducive to enhancing the interaction with the backfill soil and effectively resisting the buoyancy caused by groundwater. Therefore, it is particularly suitable for box culvert projects with small and medium spans.

[0027] 5. The box culverts in this application can be prefabricated in factories, which avoids the problems of complex joint structure, difficult stress state control, and easy local failure of joints in cast-in-place box culverts, which restricts the overall bearing capacity. In traditional cast-in-place structures, the bearing capacity of the structure is often limited by the performance of the joints, making it difficult to give full play to the combined effect and overall resistance.

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0029] Figure 1 This is an overall schematic diagram of the present invention;

[0030] In the diagram: 1. Tenon; 2. Tenon; 3. Web plate; 4. Bottom plate; 5. Pre-reserved inspection port; 6. Pre-embedded integrated lifting lug; 31. Rectangular groove;

[0031] Figure 2 This is a front view diagram of a box culvert;

[0032] Figure 3 This is a schematic diagram of the steel reinforcement mesh inside the box culvert;

[0033] Figure 4 This is a schematic diagram of the steel reinforcement structure in the corner joint area of ​​the box culvert;

[0034] In the diagram: 71. Structural stirrups; 72. Initial cut-off reinforcement; 73. Structural reinforcement; 74. Load-bearing longitudinal reinforcement;

[0035] Figure 5 This is a schematic diagram of the end section of the box culvert;

[0036] In the diagram: 8. Enclosed box culvert segment;

[0037] Figure 6 This is a schematic diagram of a box culvert broken line segment;

[0038] In the diagram: 9. Broken-line box culvert segment;

[0039] Figure 7 A schematic diagram of the mold for a box culvert unit segment;

[0040] In the diagram: 81, aluminum alloy outer mold; 82, aluminum alloy inner mold; 83, tie bolt.

[0041] Figure 8 , 9 These are cross-sectional schematic diagrams of two embodiments of structural reinforcement. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited to the present invention.

[0043] This utility model relates to a novel prefabricated box culvert with coarse aggregate UHPC. The box culvert includes a waffle-shaped upper top plate 01, a lower bottom plate 4, and web plates 3 located on both sides of the upper top plate and the lower bottom plate. The front end of the box culvert section is provided with a tenon 1, and the rear end of the box culvert section is provided with a tenon 2 that can be inserted with the tenon. The upper top plate, lower bottom plate, web plates, and tenons are made of UHPC material.

[0044] UHPC materials can be formulated using existing formulations, or using the formulations described in this application. The specific mixing ratio (kg / m3) of the UHPC material in this application is as follows:

[0045]

[0046] After adopting the aforementioned UHPC material, due to its high toughness and ductility, the web and the upper and lower bottom plates have stronger overall integrity, and the two can deform together. Furthermore, the use of this UHPC material reduces the cross-sectional area of ​​the bridge deck, which can significantly reduce the structural self-weight, improve the seismic performance of the box culvert, and greatly reduce the amount of transportation and on-site hoisting work. In addition, the potential advantages of UHPC containing coarse aggregate in terms of durability result in a significant reduction in the cost and maintenance cost of the new UHPC composite box culvert.

[0047] The box culvert can be prefabricated in the factory or cast on site. The factory prefabrication avoids the problems of complex node structure, difficult stress state control, and easy local failure of nodes in cast-in-place box culverts, which restrict the overall bearing capacity. In traditional cast-in-place structures, the bearing capacity of the structure is often limited by the performance of nodes, making it difficult to give full play to the combined effect and overall resistance.

[0048] The upper top plate has a reserved maintenance opening 5 in the middle, and several pre-embedded integrated lifting lugs 6 are provided on the side of the reserved maintenance opening in the middle of the upper top plate. The reserved maintenance opening 5 facilitates personnel access for maintenance, and the pre-embedded integrated lifting lugs 6 facilitate hoisting.

[0049] The web plate 3 and the bottom plate 4 are provided with multiple rectangular grooves 31 arranged in a matrix. The rectangular grooves 31 on the outer surface of the box culvert are conducive to enhancing the interaction with the backfill soil and effectively resisting the buoyancy caused by groundwater. Therefore, it is particularly suitable for small and medium span box culvert projects.

[0050] The corner node area of ​​the box culvert (the corner node area refers to the four corners of the box culvert) is equipped with a reinforcing steel frame 7. The reinforcing steel frame 7 includes the starting section steel bars 72 installed at the corners (four corners) of both ends (the front and rear ends) of the box culvert, and multiple longitudinal reinforcing bars 74 connecting the starting section steel bars at both ends. The longitudinal reinforcing bars 74 are set along the length of the box culvert. The starting section steel bars are formed by splicing three sets of structural bars 73 to form a triangle. Each set of structural bars 73 consists of multiple parallel steel bars 75 (a section of straight steel bar) and structural stirrups 71 arranged perpendicularly on the parallel steel bars at intervals. The cross-section of the structural bars 73 and the structural stirrups 71 can be rectangular or straight. When it is rectangular, the structural stirrups 71 are the rectangular frame, and the parallel steel bars 75 are arranged perpendicularly on the four sides of the rectangular frame. When it is straight, the structural stirrups 71 are a straight section of steel bar, and the structural stirrups 71 intersect the parallel steel bars 75 perpendicularly.

[0051] To meet different usage requirements, the front and rear end faces of the box culvert are either parallel or form an angle. Since the duct for installing the box culvert is not always straight, box culverts with an angled front and rear end faces are required at bends (e.g.,...). Figure 5 , 6 (As shown).

[0052] To ensure a sealed and waterproof connection between adjacent box culvert sections, a waterproof rubber gasket is installed at the connection point between the tenon 1 and the tenon 2 of the preceding box culvert section.

[0053] This utility model relates to a novel precast UHPC box culvert and its construction method. It mainly addresses the shortcomings of conventional reinforced concrete composite box culverts, such as large self-weight, high requirements for foundation, poor seismic performance, and the common problem that the top slab and web cannot deform in tandem, leading to easy cracking of the concrete slab in the positive bending moment region.

[0054] The construction method of this utility model for a novel precast UHPC box culvert is as follows: First, the location of the box culvert is marked out using the open excavation method, and the foundation is hardened to ensure that its bearing capacity meets the requirements.

[0055] At the prefabrication yard, determine the box culvert dimensions according to project requirements, tie the reinforcing mesh and erect the formwork, and check the sealing of the formwork. When tying the reinforcing mesh, pay attention to the reserved inspection port position on the top slab, and the reinforcing bars in this area need to be densified, and lifting lugs should be welded around it. After installing the structural stirrups 71, structural bars 73 and stressed longitudinal bars 74 in the corner node area, the whole structure needs to be measured and fine-tuned.

[0056] The box culvert mold is installed by bolts through the pre-drilled holes and the pre-drilled holes in the wall panels. The bolts are tightened with nuts to fix the mold. After demolding, the pre-drilled holes in the wall panels are sealed with UHPC mortar. The internal support of the mold can be provided by inflatable airbags.

[0057] After the formwork construction is completed, the UHPC containing coarse aggregate is poured. Before pouring the UHPC, a trial mix should be carried out to determine that its performance meets the requirements. The pouring is done as a whole.

[0058] The new precast UHPC box culvert can be cured using conventional curing methods or by steam curing at 90℃ for 48 hours. After curing, the formwork should be removed. When removing the formwork, attention should be paid to checking whether there are any defects in the box body. Defects can be repaired with UHPC mortar, and attention should be paid to grinding the exposed steel fibers on the surface of the box body.

[0059] Finally, the new prefabricated UHPC box culvert is placed on the excavated foundation.

[0060] This invention addresses the fundamental problems of traditional reinforced concrete box culverts, including their large self-weight, thick upper and lower bottom slabs and webs, and the inability of these components to deform in tandem, by addressing the design, construction, and maintenance stages. The adoption of this structural box culvert and construction method effectively avoids localized failures, concrete slab cracking, poor overall load-bearing capacity, and high maintenance costs. It also significantly reduces maintenance time and saves considerable manpower and resources, while extending the service life of the box culvert. This invention offers advantages such as simple construction, short construction period, high operability, strong applicability, ease of promotion in the existing bridge construction field, and wide applicability.

[0061] The above-described preferred embodiments further illustrate the purpose, technical solution, and advantages of this utility model. It should be understood that the above description is only a preferred embodiment of this utility model and is not intended to limit this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A novel UHPC prefabricated box culvert containing coarse aggregate, characterized in that: The box culvert includes a waffle-shaped top plate (01), a bottom plate (4), and a web plate (3) located on both sides of the top plate and the bottom plate. The front end of the box culvert section is provided with a tenon (1), and the rear end of the box culvert section is provided with a tenon (2) that can be inserted with the tenon. The top plate, bottom plate, web plate, and tenon are made of UHPC material.

2. The novel UHPC prefabricated box culvert with coarse aggregate according to claim 1, characterized in that: The upper top plate is provided with a reserved maintenance opening (5) in the middle.

3. The novel UHPC prefabricated box culvert with coarse aggregate according to claim 2, characterized in that: The upper top plate has several pre-embedded integrated lifting lugs (6) located on the side of the reserved maintenance opening in the middle.

4. The novel UHPC prefabricated box culvert with coarse aggregate according to claim 3, characterized in that: The web (3) and the bottom plate (4) are provided with a plurality of rectangular grooves (31) arranged in a matrix.

5. The novel coarse aggregate UHPC prefabricated box culvert according to claim 4, characterized in that: The corner node area of ​​the box culvert is provided with a reinforcing steel frame (7). The reinforcing steel frame (7) includes the starting section steel bars (72) installed at both ends of the box culvert and multiple stressed longitudinal bars (74) connecting the starting section steel bars at both ends. The starting section steel bars are spliced ​​together by three sets of structural bars (73) to form a triangle. Each set of structural bars (73) consists of multiple parallel steel bars and structural stirrups (71) spaced on the parallel steel bars.

6. The novel UHPC prefabricated box culvert with coarse aggregate according to claim 5, characterized in that: The cross-sections of the structural reinforcement (73) and structural stirrups (71) are rectangular. The structural stirrups (71) are rectangular frames, and the parallel steel bars (75) are arranged vertically on the four sides of the rectangular frames.

7. The novel coarse aggregate UHPC prefabricated box culvert according to claim 5, characterized in that: The cross-sections of the structural reinforcement (73) and the structural stirrup (71) are straight. The structural stirrup (71) is a straight section of steel bar. The structural stirrup (71) intersects the parallel steel bar (75) perpendicularly.

8. The novel coarse aggregate UHPC prefabricated box culvert according to claim 1, 2, 3, 4 or 5, characterized in that: The front and rear end faces of the box culvert are parallel to each other or form an angle, and a waterproof rubber gasket is provided at the connection between the tenon (1) and the tenon (2) of the previous box culvert section.

9. The novel coarse aggregate UHPC prefabricated box culvert according to claim 1, 2, 3, 4 or 5, characterized in that: The box culverts are manufactured either prefabricated in the factory or cast on site.

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