Joint structure of uhpnc bridge deck of continuous steel-concrete composite beam

Abstract

The application relates to the technical field of bridge engineering and provides a continuous steel-concrete composite beam UHPC-NC bridge deck slab joint structure, which comprises a steel beam, a UHPC bridge deck slab arranged in a negative bending moment area, a NC bridge deck slab arranged in a positive bending moment area, and a first shear nail and a second shear nail for connecting the UHPC bridge deck slab and the steel beam and connecting the NC bridge deck slab and the steel beam; the joint structure between the UHPC bridge deck slab and the NC bridge deck slab is a stepped joint; the vertical surface of the stepped joint is in the form of long upper part and short lower part; and steel fibers are continuously distributed on any section of the stepped joint. The stepped joint is designed, the vertical surface of the stepped joint is in the form of long upper part and short lower part, steel fibers are continuously distributed on any section of the stepped joint, the generation and expansion of cracks can be effectively inhibited and dispersed, and the joint has higher crack resistance and connection reliability.

Description

Technical Field

[0001] This application relates to the field of bridge engineering technology, and more specifically, to a joint structure for the deck of a continuous steel-concrete composite beam UHPC-NC bridge. Background Technology

[0002] Currently, steel-concrete composite beams have been widely used due to their ability to fully utilize the tensile properties of steel and the compressive properties of concrete, offering significant economic and technical advantages. However, the cracking of the concrete bridge deck in the negative bending moment zone of continuous steel-concrete composite beams remains a key technical challenge affecting structural durability.

[0003] The root cause of this problem lies in the poor tensile strength of ordinary concrete (NC), which makes it difficult to effectively resist the tensile stress caused by negative bending moments. Therefore, introducing new materials into the bridge deck in the negative bending moment zone is an effective approach. Ultra-high performance concrete (UHPC) possesses excellent tensile and compressive strength and outstanding durability. Applying it to the bridge deck in the negative bending moment zone of continuous steel-concrete composite beams can significantly improve its crack resistance, becoming an effective means to solve the cracking problem of bridge decks in the negative bending moment zone of large-span continuous steel-concrete composite beams.

[0004] However, due to differences between UHPC and NC in factors such as shrinkage, creep, pouring time, loading age, and ambient temperature, concrete cracking is still prone to occur at and around the joints between UHPC and NC bridge decks. These cracks not only weaken the connection and load-bearing capacity of the joints but may also cause internal steel (reinforcing bars) corrosion due to moisture infiltration, becoming a critical engineering challenge restricting the function and durability of UHPC bridge decks in the negative bending moment zone. Utility Model Content

[0005] To address the technical problem of easy cracking in the UHPC-NC joint structure of long-span steel-concrete composite beams in the positive and negative bending moment zones, this application proposes a continuous steel-concrete composite beam UHPC-NC bridge deck joint structure.

[0006] In view of this, this application proposes a joint structure for a continuous steel-concrete composite beam UHPC-NC bridge deck, comprising: a steel beam; a UHPC bridge deck, located in the negative bending moment zone, the UHPC bridge deck being connected to the steel beam via a first shear stud; and an NC bridge deck, located in the positive bending moment zone, the NC bridge deck being connected to the steel beam via a second shear stud; the joint structure between the UHPC bridge deck and the NC bridge deck is a stepped joint; wherein the stepped joint has an upper longer and lower shorter profile, and steel fibers are continuously distributed on any cross section of the stepped joint.

[0007] In some feasible embodiments, the top of the steel beam is provided with a flange plate, and the UHPC bridge deck includes: a bridge deck equal-thickness section and at least two bridge deck haunches disposed at the bottom of the bridge deck equal-thickness section; the bridge deck haunches are connected to the flange plate; the bridge deck equal-thickness section is connected between two adjacent bridge deck haunches.

[0008] In some feasible implementations, the bridge deck axle section has a thickness transition section outside the connection interface with the flange plate. The thickness transition section is a linear transition section that connects the bridge deck axle section and the equal-thickness section of the bridge deck.

[0009] In some feasible implementations, the stepped joint includes: an upper step, which is formed by extending from the end of the UHPC bridge deck; and a lower step, which is formed by extending from the end of the NC bridge deck.

[0010] In some feasible methods, the thickness of the upper step is not less than 50 mm and the length is not less than 150 mm.

[0011] In some feasible implementations, the NC bridge deck is provided with two layers of longitudinal reinforcement and two layers of transverse reinforcement, with the longitudinal reinforcement located inside the transverse reinforcement; the diameter of the longitudinal reinforcement is not less than 16mm, and the diameter of the transverse reinforcement of the NC bridge deck is not less than 22mm.

[0012] In some feasible ways, the longitudinal reinforcement of the NC bridge deck passes through the stepped joint and extends into the UHPC bridge deck, and the lap position of the longitudinal reinforcement in the UHPC bridge deck is not less than 2000mm away from the stepped joint.

[0013] In some feasible configurations, the UHPC bridge deck is provided with two layers of longitudinal reinforcement and two layers of transverse reinforcement, with the longitudinal reinforcement located inside the transverse reinforcement; the clear distance between the two layers of longitudinal reinforcement is not less than 30 mm, and is also not less than the nominal diameter of the longitudinal reinforcement and 1.5 times the length of the steel fiber.

[0014] In some feasible ways, the transverse reinforcement of the UHPC bridge deck is arranged along the entire length of the UHPC bridge deck, and the protective layer thickness of the transverse reinforcement is not less than 20mm.

[0015] In some feasible ways, the longitudinal reinforcement bars of the UHPC bridge deck pass through the stepped joint and extend into the NC bridge deck, and the lap position of the longitudinal reinforcement bars in the NC bridge deck is not less than 2000mm away from the stepped joint.

[0016] Compared with related technologies, this application has the following technical advantages: This application provides a continuous steel-concrete composite beam UHPC-NC bridge deck joint structure, including a steel beam, a UHPC bridge deck, and an NC bridge deck. By adopting a stepped joint design, its elevation is longer at the top and shorter at the bottom, ensuring continuous steel fiber distribution across any cross-section of the joint area. This eliminates the weak surface of traditional flat joints where there is no continuous steel fiber throughout the entire cross-section. The ultra-high steel fiber content in the UHPC bridge deck, combined with the stepped geometry, forms a three-dimensional micro-reinforced skeleton at the joint, significantly enhancing the tensile strength, toughness, and crack-limiting capacity of this area, effectively suppressing and dispersing the generation and propagation of cracks.

[0017] By applying UHPC to the negative moment zone of long-span continuous steel-concrete composite beams, its superior tensile properties are fully utilized, effectively solving the problem of easy cracking in the bridge deck in this area, thereby improving the overall safety and durability of the bridge structure. Compared with conventional flat joint construction, the stepped joint adopted in this application avoids the situation of discontinuous steel fibers throughout the cross-section, giving the joint higher crack resistance and connection reliability. By setting the UHPC-NC bridge deck joint in the low tensile stress zone or even the compressive stress zone of the structure, the risk of tensile cracking in the concrete of the joint and its surrounding area is further avoided. In addition, this structure eliminates the requirement for prestressed steel reinforcement in the concrete bridge deck of the negative moment zone, greatly simplifying the construction process and improving the feasibility of the project.

[0018] Additional aspects and advantages of this application will become apparent in the following description or may be learned by practice of this application. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 A schematic diagram of the joint structure of the continuous steel-concrete composite beam UHPC-NC bridge deck is shown in one embodiment of this application; Figure 2 yes Figure 1 The diagram shows a plan view of the joint structure of the deck of the UHPC-NC continuous steel-concrete composite beam bridge. Figure 3 yes Figure 1 Schematic diagram of the AA section structure; Figure 4 yes Figure 1 Schematic diagram of the BB cross-section structure; Figure 5 yes Figure 1 A schematic diagram of the CC section structure.

[0020] in, Figures 1 to 5 The correspondence between the reference numerals and component names in the attached drawings is as follows: 1-UHPC bridge deck, 2-NC bridge deck, 3-Stepped joint, 4-Steel beam, 5-First shear stud, 6-Second shear stud, 7-Bridge deck haunch section, 8-Bridge deck equal thickness section, 9-Upper step, 10-Lower step, 11-Longitudinal reinforcement of UHPC bridge deck, 12-Transverse reinforcement of UHPC bridge deck, 13-Longitudinal reinforcement of NC bridge deck, 14-Transverse reinforcement of NC bridge deck. Detailed Implementation

[0021] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0023] The following reference Figures 1 to 5 This application describes the joint construction of the continuous steel-concrete composite beam UHPC-NC bridge deck according to some embodiments.

[0024] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, this application proposes a joint structure for a continuous steel-concrete composite beam UHPC-NC bridge deck, comprising: a steel beam 4; a UHPC bridge deck 1, located in the negative bending moment zone, the UHPC bridge deck 1 being connected to the steel beam 4 via a first shear stud 5; an NC bridge deck 2, located in the positive bending moment zone, the NC bridge deck 2 being connected to the steel beam 4 via a second shear stud 6; the joint structure between the UHPC bridge deck 1 and the NC bridge deck 2 is a stepped joint 3; wherein, the stepped joint 3 has a shape that is longer at the top and shorter at the bottom, and steel fibers are continuously distributed on any cross section of the stepped joint 3.

[0025] The continuous steel-concrete composite beam UHPC-NC bridge deck joint structure provided in this application includes a steel beam 4, a UHPC bridge deck 1, and an NC bridge deck 2. The UHPC bridge deck 1 is positioned in the negative bending moment zone, while the NC bridge deck 2 is positioned in the positive bending moment zone, fully utilizing the properties of both materials. The high strength and high toughness of UHPC effectively resist tensile stress in the negative bending moment zone, reducing crack formation; the NC bridge deck 2 offers good economic efficiency, and its use in the positive bending moment zone reduces costs. The overall structure exhibits more rational stress distribution, improving load-bearing capacity and stability.

[0026] By employing stepped joint 3, the facade exhibits a shape that is longer at the top and shorter at the bottom, ensuring continuous steel fiber distribution across any cross-section in the joint area. This eliminates the weak points of the entire cross-section lacking steel fibers. The ultra-high steel fiber content in the UHPC bridge deck 1, combined with the stepped geometry, is equivalent to setting up a three-dimensional micro-reinforced skeleton at the joint, enhancing the tensile strength, toughness, and crack-limiting capacity of the joint, effectively suppressing and dispersing the generation and propagation of cracks.

[0027] This application integrates the advantages of materials with mechanical principles, achieving a synergistic improvement in joint crack resistance, overall structural durability, ease of construction, and engineering economy, providing an advanced and reliable solution for the development of long-span continuous steel-concrete composite beams. By comprehensively utilizing UHPC and NC materials, material costs and engineering expenses are reduced while ensuring structural performance, thus improving economic efficiency. Simultaneously, it guarantees bridge quality and safety, reduces subsequent maintenance costs, and has significant social benefits.

[0028] like Figure 3 As shown, in some embodiments provided in this application, the top of the steel beam 4 is provided with a flange plate, and the UHPC bridge deck 1 includes: a bridge deck equal thickness section 8 and at least two bridge deck axle sections 7 disposed at the bottom of the bridge deck equal thickness section 8; the bridge deck axle sections 7 are connected to the flange plate; the bridge deck equal thickness section 8 is connected between two adjacent bridge deck axle sections 7.

[0029] In this embodiment, the bridge deck haunch segment 7 serves as the connection transition zone between the UHPC bridge deck 1 and the flange plate of the steel beam 4, providing a larger concrete bearing area and a smoother stiffness transition. This allows for more effective transfer of the stress from the bridge deck to the steel beam 4, reducing stress concentration in the connection area and thus enhancing the overall stress performance and reliability of the negative bending moment zone composite structure.

[0030] The equal-thickness section 8 of the bridge deck located between the axle segments can be finely thinned according to the actual stress requirements of the negative bending moment zone. Without sacrificing the load-bearing capacity of critical areas, the permanent load on the bridge superstructure is reduced to the maximum extent. This plays an important role in reducing the dead load effect of long-span bridges, improving the structural stress state, and saving expensive UHPC materials, resulting in significant economic benefits.

[0031] The axle segment focuses on interface connection, while the equal-thickness segment dominates the span stress, resulting in clear structural functional zoning. This facilitates the organization of formwork engineering and concrete pouring, ensuring the molding quality of the UHPC. Simultaneously, the optimized stress pattern reduces the risk of concrete cracking, further guaranteeing the long-term durability of the structure.

[0032] like Figure 3As shown, in some embodiments provided in this application, the bridge deck axle section 7 is provided with a thickness transition section outside the connection interface with the flange plate. The thickness transition section is a linear transition section, connecting the bridge deck axle section 7 and the bridge deck equal thickness section 8.

[0033] In this embodiment, the linear transition section forms a stiffness buffer zone between the bridge deck axle section 7 (with greater thickness) and the bridge deck equal-thickness section 8 (with less thickness). This zone can efficiently conduct and diffuse the concentrated stress transmitted from the steel beam 4 to the bridge deck, effectively avoiding stress concentration at the abrupt change in cross-section. This significantly reduces the risk of concrete cracking and enhances the durability and reliability of the negative bending moment zone structure.

[0034] The linear transition design simplifies formwork fabrication and installation, and facilitates the smooth filling of the mold cavity by ultra-high performance concrete (UHPC) during pouring, ensuring its density and final molding quality. From a structural efficiency perspective, the variation in slab thickness strictly follows stress requirements, achieving optimal material distribution and contributing to minimizing the self-weight of the bridge deck while ensuring the strength of critical connection areas.

[0035] like Figure 1 As shown, in some embodiments provided in this application, the stepped joint 3 includes: an upper step 9, which is formed by extending from the end of the UHPC bridge deck 1; and a lower step 10, which is formed by extending from the end of the NC bridge deck 2.

[0036] In this embodiment, the upper step 9 is formed by extending the high-strength UHPC bridge deck 1, which can better withstand the complex stress in the negative bending moment zone and effectively transfer the upper load to the lower structure; the lower step 10 is formed by extending the NC bridge deck 2, which can stably bear the force transferred from the upper part and disperse it to the steel beam 4 by means of its own characteristics, so as to realize the smooth transmission of force, reduce local stress concentration, and improve the overall structural bearing capacity.

[0037] The stepped structure increases the contact area of ​​the joint, and together with the continuously distributed steel fibers inside, it improves the shear and tensile strength of the joint, effectively inhibits the generation and propagation of cracks, and enhances the durability and crack resistance of the joint.

[0038] like Figure 1 As shown, in some embodiments provided in this application, the thickness of the upper step 9 is not less than 50 mm and the length is not less than 150 mm.

[0039] In this embodiment, the 50mm thick UHPC layer can effectively resist the tensile stress in the negative bending moment zone, has strong compressive strength, can bear the local compressive stress generated by vehicle load, and avoid crushing damage at the joint.

[0040] The 150mm long transition section makes the stress distribution at the interface between UHPC and NC more uniform, and the stepped structure disperses the concentrated stress to steel beam 4, reducing the peak stress at the joint edge by 30% and reducing the risk of cracking.

[0041] like Figure 1 As shown, in some embodiments provided in this application, the NC bridge deck 2 is provided with two layers of longitudinal steel bars and two layers of transverse steel bars, and the longitudinal steel bars are located inside the transverse steel bars; the diameter of the longitudinal steel bars 13 of the NC bridge deck is not less than 16mm, and the diameter of the transverse steel bars 14 of the NC bridge deck is not less than 22mm.

[0042] In this embodiment, the longitudinal reinforcement is placed inside the transverse reinforcement, bringing it closer to the neutral axis at the center of the slab thickness. This allows it to more effectively withstand tensile stress under positive bending moment, fully utilizing the tensile strength of the longitudinal reinforcement. Simultaneously, the diameter of the transverse reinforcement 14 in the NC bridge deck is limited to no less than 22mm, and the diameter of the longitudinal reinforcement 13 in the NC bridge deck is no less than 16mm. This is a refined design based on the actual stress characteristics of the bridge deck. In the composite beam system, the bridge deck acts as a flange, primarily bearing the longitudinal shear flow between the steel beam 4 and the concrete transmitted by shear studs. Laterally, it acts as a multi-span continuous slab, typically experiencing larger transverse bending moments. The thicker transverse reinforcement significantly improves the transverse bending stiffness and bearing capacity of the bridge deck, ensuring its local stress safety under complex loads.

[0043] In some embodiments provided in this application, the longitudinal steel bars 13 of the NC bridge deck pass through the stepped joint 3 and extend into the UHPC bridge deck 1, and the lap position of the longitudinal steel bars in the UHPC bridge deck 1 is not less than 2000mm away from the stepped joint 3.

[0044] In this embodiment, the longitudinal steel bars 13 of the NC bridge deck continuously pass through the stepped joint 3 and are anchored in the UHPC bridge deck 1, effectively transferring the tensile force in the positive bending moment zone to the negative bending moment zone, avoiding abrupt changes in stress at the joint interface, and ensuring the integrity of the composite beam working together in the span and support areas.

[0045] Placing the lap joint at least 2000mm away from the joint actively avoids areas of high stress. Under load, the area near the joint is a region of stress concentration and complex deformation. By moving the lap joint of the reinforcing steel (an inherently relatively weak link) to this location, placing it in a low-stress zone of the structure, the risk of premature failure or slippage and cracking of the lapped section of reinforcing steel and concrete due to excessive stress is significantly reduced. This is analogous to installing the most leaky joint of a water pipe in the location of least pressure, greatly improving the reliability of the connection.

[0046] In some embodiments provided in this application, the UHPC bridge deck 1 is provided with two layers of longitudinal steel bars and two layers of transverse steel bars, with the longitudinal steel bars located inside the transverse steel bars; the clear distance between the two layers of longitudinal steel bars is not less than 30 mm, and is not less than the nominal diameter of the longitudinal steel bar and 1.5 times the length of the steel fiber.

[0047] In this embodiment, the clear distance between longitudinal reinforcing bars is limited to not less than the diameter of the reinforcing bar and 1.5 times the length of the steel fiber. This creates a decisive condition for the smooth flow of steel fibers during casting, preventing them from tangling or blocking each other in areas with dense reinforcing bars. An unobstructed "passage channel" is established for the steel fibers, allowing them to be uniformly distributed in a three-dimensional random direction. Therefore, when the UHPC bridge deck 1 is under stress, millions of steel fibers can effectively play a bridging role, inhibiting the development of microcracks. This is the fundamental prerequisite for achieving the ultra-high toughness and post-cracking load-bearing capacity of the UHPC bridge deck 1.

[0048] A minimum clear spacing of 30mm avoids dead zones in the pouring process caused by excessively dense reinforcement, allowing ultra-high performance concrete (UHPC), a material that is typically highly fluid but also highly viscous, to fully fill all voids and form a dense structure. This ensures that the material properties calculated in theory are fully realized in the actual structure. The minimum 30mm clear spacing also allows the concrete and steel fibers to fully encapsulate each rebar, providing not only excellent bond anchorage but also creating a multi-layered composite reinforcement system. The rebar is responsible for macroscopic load-bearing capacity, while the densely distributed steel fibers control microscopic cracks and bear post-cracking stress. Together, they transform the superior compressive, tensile, and fatigue resistance of UHPC into excellent overall structural durability and safety reserves.

[0049] In some embodiments provided in this application, the transverse reinforcing bars 12 of the UHPC bridge deck are arranged along the entire length of the UHPC bridge deck 1, and the protective layer thickness of the transverse reinforcing bars is not less than 20mm.

[0050] In this embodiment, the protective layer thickness of the transverse reinforcing bars 12 of the UHPC bridge deck is not less than 20mm, providing a sufficiently thick UHPC protective layer for the reinforcing bars. UHPC itself has extremely high density and impermeability. Combined with the sufficient protective layer thickness, it can effectively isolate the intrusion of corrosive media such as moisture and chloride ions, fundamentally preventing the corrosion of the reinforcing bars and ensuring the ultra-long service life of the UHPC bridge deck 1 in harsh environments.

[0051] The long transverse steel bars act like "hoops" to connect the entire UHPC bridge deck 1 into one unit. This not only improves the transverse stiffness and load distribution capacity of the bridge deck itself, but more importantly, it forms a spatial steel reinforcement network together with the longitudinal steel bars. This effectively constrains the deformation of the concrete, improves the combined effect of the bridge deck and the steel beam 4, and enhances the overall integrity of the structure under complex stress conditions.

[0052] In some embodiments provided in this application, the longitudinal steel bars 11 of the UHPC bridge deck pass through the stepped joint 3 and extend into the NC bridge deck 2, and the lap position of the longitudinal steel bars in the NC bridge deck 2 is not less than 2000mm away from the stepped joint 3.

[0053] In this embodiment, when the longitudinal reinforcement 11 of the UHPC bridge deck passes through the joint and extends into the NC bridge deck 2, it combines with the structure where the NC plate reinforcement extends into the UHPC plate, forming a mutually intersecting and mutually anchored reinforcement network on both sides of the joint. This allows internal forces to be efficiently and continuously transferred between the UHPC and NC bridge deck 2 through the bidirectional reinforcement system, regardless of load changes, greatly enhancing the force transmission efficiency and structural integrity of the joint, and preventing the joint from becoming a weak point in the load-bearing structure.

[0054] Setting the lap joint at a distance of at least 2000mm from the joint is crucial, as the area near the joint is prone to stress concentration and complex deformation due to abrupt changes in material properties and geometry. By relocating this relatively weak link—the lap joint—to a low-stress zone, away from the peak bending moment and shear force surfaces, premature failure of the lap joint under high peak stress is effectively prevented, thus significantly improving the long-term safety reserve and fatigue resistance of the joint structure.

[0055] Meanwhile, the high stress from the UHPC side is transferred to the NC area through the steel bars and effectively diffused, reducing the stress burden on the UHPC body at the joint, allowing different materials to perform their respective functions and work together to ensure the long-term durability of the joint area.

[0056] like Figures 1 to 5 As shown in the specific embodiment, this application provides a continuous steel-concrete composite beam UHPC-NC bridge deck joint structure, which is set between the negative bending moment zone UHPC bridge deck 1 and the positive bending moment zone NC bridge deck 2 of the large-span continuous steel-concrete composite beam, including UHPC bridge deck 1, NC bridge deck 2 and UHPC-NC bridge deck 2 joint.

[0057] UHPC bridge deck 1 is installed in the negative bending moment zone of the long-span continuous composite beam bridge and is connected to the steel beam 4 by shear studs. UHPC bridge deck 1 has a variable cross-section in cross-section, including bridge deck haunch section 7 and bridge deck section of equal thickness 8. UHPC bridge deck 1 can be formed by cast-in-place or precast process according to the actual construction requirements of the project, and steam curing is adopted.

[0058] The UHPC bridge deck 1 haunch section is located at the connection between the bridge deck and the steel beam 4. The thickness of the plate at the connection position with the flange plate of the steel beam 4 is the same as the thickness of the NC bridge deck 2. The remaining part adopts a variable thickness form, with the thickness gradually changing from the thickness of the NC bridge deck 2 to the thickness of the equal-thickness section of the UHPC bridge deck 1.

[0059] The thickness of the UHPC bridge deck section 1, which is located between the haunches on both sides, is determined by comprehensively considering the crack resistance performance in the negative bending moment zone, the local stress requirements, and the structural provisions for the arrangement of reinforcement in the current code.

[0060] NC bridge deck 2 is located in the positive bending moment zone of the long-span continuous composite beam bridge and is connected to the steel beam 4 by shear studs. NC bridge deck 2 adopts a uniform thickness arrangement, and its thickness is reasonably determined based on the overall structural stress, local stress, and structural design requirements. NC bridge deck 2 can be formed using cast-in-place or precast processes according to the actual construction requirements of the project.

[0061] The UHPC-NC bridge deck 2 joint is located between the UHPC bridge deck 1 and the NC bridge deck 2, and is designed as a stepped joint 3. The joint facade is longer at the top and shorter at the bottom to ensure that there is a continuous distribution of steel fibers on any cross section of the joint area. The thickness of the upper part of the step is not less than 50mm, and the step length is not less than 150mm.

[0062] All longitudinal reinforcement bars in NC bridge deck 2 should extend beyond the UHPC-NC joint, and the lap position of all longitudinal reinforcement bars should be no less than 2000mm away from the joint.

[0063] In practical applications, this application provides a continuous steel-concrete composite beam UHPC The NC bridge deck joint structure includes UHPC bridge deck 1 and NC bridge deck 2. The two are interconnected to form a stepped UHPC. NC bridge deck 2 joint. UHPC bridge deck 1 and NC bridge deck 2 are connected to steel beam 4 by shear studs to form a composite structure to share the load.

[0064] UHPC bridge deck 1 is installed in the negative bending moment zone of long-span continuous steel-concrete composite beams. Utilizing the excellent tensile strength of UHPC, it resists the tensile stress caused by negative bending moments, eliminating the need for prestressed steel reinforcement and keeping the bridge deck in a crack-free or slightly cracked state. This meets the stress performance requirements of the negative bending moment zone, ensuring structural safety and durability. The UHPC bridge deck 1 can be formed using cast-in-place or precast processes and cured with steam. After casting, a membrane is applied to maintain moisture, followed by low-temperature steam curing at 50–60℃ for at least 72 hours.

[0065] NC bridge deck 2 is located in the positive bending moment zone and adopts a uniform thickness design, with a deck thickness of 270mm, determined based on the overall structural stress, local stress, and construction requirements. NC bridge deck 2 can be formed using cast-in-place or precast processes. Internally, it has upper and lower layers of longitudinal reinforcement and upper and lower layers of transverse reinforcement, with the longitudinal reinforcement located inside the transverse reinforcement; the diameter of the longitudinal reinforcement is not less than 16mm, and the diameter of the transverse reinforcement is not less than 22mm.

[0066] To reduce structural weight, save materials, and lower costs, the UHPC bridge deck 1 adopts a variable cross-section, including a haunch section 7 and a constant-thickness section 8. The haunch section connects the UHPC bridge deck 1 to the steel beam 4, and its thickness at the connection point with the steel beam 4 is the same as that of the NC bridge deck 2, which is 270mm. The constant-thickness section 8 has a thickness of 170mm, taking into account the crack resistance in the negative bending moment zone, local stress, and the structural requirements for reinforcement arrangement in the code. On both sides of the haunch section, outside the connection range with the steel beam 4, there are linear transition sections with a length of 200mm each, with starting and ending thicknesses of 270mm and 170mm respectively.

[0067] The UHPC bridge deck 1 contains two layers of longitudinal reinforcement and two layers of transverse reinforcement, with the longitudinal reinforcement located inside the transverse reinforcement. The clear spacing between each layer of longitudinal reinforcement is not less than 30mm, and not less than the diameter of the reinforcement and 1.5 times the length of the steel fiber. The transverse reinforcement is arranged along the entire length of the bridge deck, with a clear protective layer thickness of not less than 20mm.

[0068] UHPC The NC bridge deck 2 joint is a stepped joint 3, with a shape that is longer at the top and shorter at the bottom. This ensures that steel fibers are continuously distributed across any cross-section of the joint area, thus avoiding the weakness of traditional straight joints where there are no steel fibers across the entire cross-section. The upper part of the joint step is a UHPC plate with a thickness of not less than 50mm, and the lower part is an NC plate. The step length is not less than 150mm. All longitudinal reinforcements in the UHPC bridge deck 1 should extend beyond the joint, and the lap position between the UHPC reinforcements and the longitudinal reinforcements in the NC bridge deck 2 should be not less than 2000mm from the joint.

[0069] This application provides a continuous steel-concrete composite beam UHPC The construction method for NC bridge deck joints includes the following steps: Step 1: Fabricate the steel beams, transport and hoist them in sections, connect them into a continuous beam on site, and apply the topcoat to the steel beams on-site. Then, carry out the jacking construction. Step 2: Cast the NC bridge deck on site and cure it under natural conditions until its strength reaches 95% of the design strength; Step 3: Cast the UHPC bridge deck in the negative bending moment zone on site. After casting, cover it with a film to keep it moist and use low-temperature steam curing. Demold it after it reaches the specified strength. Step 4: Carry out the fulcrum lowering construction, followed by bridge deck paving and ancillary works construction, and finally complete the bridge.

[0070] In this application, the term "multiple" refers to two or more unless otherwise expressly defined. The terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0071] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0072] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A joint structure for the deck of a continuous steel-concrete composite beam UHPC-NC bridge, characterized in that, include: steel beams; UHPC bridge deck, located in the negative bending moment zone, is connected to the steel beam by a first shear stud; An NC bridge deck is located in the positive bending moment zone, and the NC bridge deck is connected to the steel beam by a second shear stud. The joint between the UHPC bridge deck and the NC bridge deck is a stepped joint. The stepped joint has a shape that is longer at the top and shorter at the bottom, and there are continuously distributed steel fibers on any cross section of the stepped joint.

2. The joint structure of the UHPC-NC bridge deck of the continuous steel-concrete composite beam according to claim 1, characterized in that, The top of the steel beam is provided with a flange plate, and the UHPC bridge deck includes: a bridge deck equal thickness section and at least two bridge deck haunches disposed at the bottom of the bridge deck equal thickness section; The bridge deck axle section is connected to the flange plate; The equal-thickness section of the bridge deck is connected between two adjacent bridge deck axle sections.

3. The joint structure of the UHPC-NC bridge deck of the continuous steel-concrete composite beam according to claim 2, characterized in that, The bridge deck axle section has a thickness transition section outside the connection interface with the flange plate. The thickness transition section is a linear transition section that connects the bridge deck axle section and the equal-thickness section of the bridge deck.

4. The joint structure of the UHPC-NC bridge deck of the continuous steel-concrete composite beam according to claim 1, characterized in that, The stepped joint includes: Upper step, which is formed by extending from the end of the UHPC bridge deck; The lower step extends from the end of the NC bridge deck.

5. The joint structure of the UHPC-NC bridge deck of the continuous steel-concrete composite beam according to claim 4, characterized in that, The thickness of the upper step is not less than 50mm and the length is not less than 150mm.

6. The joint structure of the UHPC-NC bridge deck of the continuous steel-concrete composite beam according to claim 1, characterized in that, The NC bridge deck is provided with two layers of longitudinal steel bars and two layers of transverse steel bars, with the longitudinal steel bars located inside the transverse steel bars; the diameter of the longitudinal steel bars is not less than 16mm, and the diameter of the transverse steel bars of the NC bridge deck is not less than 22mm.

7. The joint structure of the UHPC-NC bridge deck of the continuous steel-concrete composite beam according to claim 6, characterized in that, The longitudinal reinforcement bars of the NC bridge deck pass through the stepped joint and extend into the UHPC bridge deck, and the lap position of the longitudinal reinforcement bars in the UHPC bridge deck is not less than 2000mm away from the stepped joint.

8. The joint structure of the UHPC-NC bridge deck of a continuous steel-concrete composite beam according to any one of claims 1 to 7, characterized in that, The UHPC bridge deck is provided with two layers of longitudinal steel bars and two layers of transverse steel bars, with the longitudinal steel bars located inside the transverse steel bars. The clear distance between the upper and lower layers of longitudinal reinforcing bars shall not be less than 30mm, and shall also not be less than the nominal diameter of the longitudinal reinforcing bars and 1.5 times the length of the steel fibers.

9. The joint structure of the UHPC-NC bridge deck of the continuous steel-concrete composite beam according to claim 8, characterized in that, The transverse reinforcing bars of the UHPC bridge deck are arranged along the entire length of the UHPC bridge deck, and the protective layer thickness of the transverse reinforcing bars is not less than 20mm.

10. The joint structure of the UHPC-NC bridge deck of the continuous steel-concrete composite beam according to claim 8, characterized in that, The longitudinal reinforcement bars of the UHPC bridge deck all pass through the stepped joint and extend into the NC bridge deck, and the lap position of the longitudinal reinforcement bars in the NC bridge deck is not less than 2000mm away from the stepped joint.

Images