Prefabricated partially clad steel-UHPC composite bridge structure and construction method thereof

Abstract

The application provides an assembled partially coated steel-UHPC combined bridge structure and a construction method thereof, and belongs to the technical field of structural members. The bridge structure comprises a partially coated steel beam component, a bridge deck slab and a post-poured slot opening. Steel bars in the steel beam component are connected with the steel beam through through holes at the web of the steel beam. Multiple shear key units are arranged at intervals at the upper opening of the steel beam. The bottom die in the shear key unit is arranged at the upper opening of the steel beam and encloses the inner side of the web to form a post-poured space. The inverted U-shaped shear member encloses a square body above the upper side of the bottom die and is connected with the steel bars and embedded in the post-poured concrete. The bridge deck slab is provided with a post-poured slot opening corresponding to the shear key unit. The shear key unit, the steel bars and the steel beam form a multidimensional three-dimensional connection structure, which improves the bearing strength of the bridge and effectively transmits shear force. The post-poured concrete covers the entire three-dimensional connection structure and is glued with the bridge deck slab to form an integral whole, thereby increasing the connection strength and improving the shear strength.

Description

Technical Field

[0001] This invention belongs to the field of structural component technology, specifically relating to prefabricated partially clad steel-UHPC composite bridge structures and their construction methods. Background Technology

[0002] Steel-concrete composite beam bridges avoid the disadvantages of traditional steel and concrete bridges, such as heavy weight and numerous defects. They fully combine the mechanical properties of concrete and steel, and their application scope is increasing. For example, the patent application CN112663486A, "Steel-concrete composite beam structure and construction method with steel beam heightened in negative bending moment zone", uses steel formwork or profiled steel sheet as bottom formwork. The bridge deck steel mesh is tied on the bottom formwork. The transverse steel bars in the negative bending moment zone penetrate the web of the steel beam, and the longitudinal steel bars penetrate the upper flange of the beam height transition section. Then, concrete is poured to form a beam structure in which the steel beam is embedded in the concrete bridge deck. The above-mentioned composite beam structure requires a lot of on-site pouring work, which is complex and has a long construction period. The new type of prefabricated steel-concrete composite bridge adopts a bridge combination form with a steel main beam below and a concrete bridge deck above. By using prefabricated components in the factory, the assembly construction, including the connection between the slab and the beam and the connection between the bridge decks, is carried out on site, which reduces the on-site construction procedures and shortens the construction period. For example, the patent application CN115233536A, "A Lightweight Prefabricated Steel-UHPC Composite Beam and Its Assembly and Disassembly Method", discloses a lightweight prefabricated steel-UHPC composite beam, including a UHPC bridge deck and a steel main beam. A steel bottom plate is provided below the UHPC bridge deck, and an upper flange plate is provided above the steel main beam. Through holes are opened in the same position on the steel bottom plate and the upper flange plate. T-bolts pass through the through holes of the steel bottom plate and the upper flange plate to connect the bridge deck and the steel main beam to form a steel-UHPC composite beam. Compared with conventional precast bridges, the steel-UHPC composite beams reduce the amount of steel by 40%, the weight by about 50%, and the cost by 20%. However, the stress on the T-bolts at the connection nodes of the composite beams is more complex. When subjected to shear force at the plate-beam interface, relative slippage occurs between the interface of the steel beam and the concrete bridge deck, and the T-bolts deform. This poses significant fatigue risks and stress concentration phenomena, which affect the stiffness and load-bearing capacity of the composite beams. The shear strength of the interface cannot guarantee the integrity of the bridge structure, which can easily lead to interface failure risks. The service life of the composite beams is difficult to meet the durability requirements of modern bridge engineering. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a prefabricated partially clad steel-UHPC composite bridge structure and its construction method, which does not use a stud structure to connect the bridge deck and the steel main beam, thereby avoiding the fatigue risk and stress concentration at the stud connection nodes when the steel beam and the concrete bridge deck slide relative to each other, and improving the service life of the bridge.

[0004] The present invention discloses a prefabricated partially clad steel-UHPC composite bridge structure, which includes steel beam members and bridge deck. The bridge deck includes a steel reinforcement skeleton and a concrete layer covering the steel reinforcement skeleton. The steel reinforcement skeleton includes longitudinal steel bars and transverse steel bars that are connected to each other.

[0005] The steel beam component includes a steel beam, reinforcing bars, and a UHPC layer; the web of the steel beam has through holes, through which the reinforcing bars pass and connect to the steel beam; the outer side of the steel beam is covered with the UHPC layer.

[0006] The steel beam has an opening at its upper end, and multiple shear key units are spaced apart at the opening. Each shear key unit includes a bottom formwork and four shear members. The bottom formwork is located at the opening at the upper end of the steel beam and forms a casting space with the inner side of the web of the steel beam. The shear members are inverted U-shaped. The shear members form a square shape above the upper side of the bottom formwork and are connected to at least one of the reinforcing bars, and are embedded in the post-cast concrete. The lower end of the shear members is connected to the bottom formwork.

[0007] The bridge deck has multiple post-cast slots, and the shear key unit and the post-cast slot are matched one-to-one. The transverse and longitudinal sides of the square body overlap with the longitudinal and transverse reinforcing bars, respectively.

[0008] This invention provides a prefabricated concrete bridge structure, comprising prefabricated steel beam components and bridge deck panels. Shear key units within the steel beam components form a square shape above the upper side of the bottom formwork, ensuring identical shear performance in both longitudinal and transverse directions at the interface. This guarantees mechanical advantages in both longitudinal and transverse directions at the joint surface when subsequently bonded to the bridge deck panel. The shear key units in the steel beam components are connected to the internal reinforcing steel bars through perforated shear components and the bottom formwork. A multi-dimensional, intersecting three-dimensional connection structure is formed between the shear components and the bottom formwork, the bottom formwork and the steel beam, the shear components and the reinforcing steel bars, and the reinforcing steel bars and the steel beam, improving the strength of the steel beam components and effectively transferring shear forces between components. The outer surface of the steel beam is covered with a UHPC (Ultra-High Performance Concrete) layer, further enhancing the strength of the steel beam components and effectively preventing corrosion of the steel beam and reinforcing steel bars encased in the UHPC layer, reducing the risk of corrosion fatigue. Furthermore, during subsequent assembly, the square-shaped structure formed by the shear members overlaps with the longitudinal and transverse reinforcing bars in the steel reinforcement skeleton inside the bridge deck, extending this three-dimensional connection structure to the connection between the steel beam members and the bridge deck. This allows the three-dimensional connection structure to overlap with the transverse and longitudinal reinforcing bars in the bridge deck, forming an interactive overall load-bearing structure. This reduces yielding failure caused by excessive local stress in individual shear members, improves the shear stiffness of the connection interface between the steel beam members and the bridge deck, enhances the shear strength of the bridge structure, and enables it to withstand shear forces in different directions, avoiding stress concentration and improving the overall load-bearing strength of the bridge structure. Moreover, the local pouring of concrete at the post-pouring slot fills the pouring space enclosed by the bottom formwork and the inner side of the web of the steel beam, as well as the post-pouring slot, covering the entire three-dimensional connection structure. The connection interface of the concrete forms shear stress surfaces in different directions, further enhancing the shear strength of the prefabricated concrete structure bridge. The post-cast concrete is bonded to the bridge deck, making the connection between the bridge deck and the steel beam components a whole. This enhances the connection strength between the shear key unit and the post-cast groove, fundamentally improving the fatigue performance of the connection node and increasing its long-term durability.

[0009] Furthermore, the concrete layer includes a first UHPC layer, an NSC (Normal Strength Concrete) layer, and a second UHPC layer arranged sequentially from top to bottom; the reinforcing steel skeleton also includes a perforated steel plate; the perforated steel plate supports and connects the longitudinal reinforcing bars and the transverse reinforcing bars, so that the reinforcing steel skeleton forms a double-layer bidirectional reinforcing steel mesh; the perforated steel plate penetrates the NSC layer and is connected to the first UHPC layer and the second UHPC layer respectively.

[0010] The precast bridge deck adopts a three-layer structure of "UHPC-NSC-UHPC," which is an optimized interface layer design based on the stress characteristics of the bridge deck structure. This not only fully utilizes the mechanical advantages of the materials and reduces costs but also effectively reduces the self-weight of the bridge deck. Simultaneously, perforated steel plates are pre-embedded in the NSC layer, vertically penetrating the NSC layer. These perforated steel plates, together with the longitudinal and transverse reinforcing bars in the upper and lower UHPC layers, form a double-layer bidirectional reinforcing mesh, creating a reinforced steel skeleton. This reinforcing skeleton, together with the "UHPC-NSC-UHPC" three-layer structure, forms a firmly connected bridge deck assembly. Furthermore, during subsequent assembly, inverted U-shaped shear keys in the steel beam members penetrate the "UHPC-NSC-UHPC" three-layer structure of the bridge deck and connect with the double-layer bidirectional reinforcing mesh in the bridge deck. This not only firmly connects the steel beam members and the bridge deck but also provides interface connection for the three surfaces of the bridge deck, effectively reducing interface slippage and separation between adjacent layers.

[0011] Furthermore, the perforated steel plate has a perforation in the middle. When the concrete in the perforation is poured during the precasting of the bridge deck, the concrete inside the perforation forms a concrete tenon structure, which effectively increases the shear area of ​​the interface, strengthens the connection between the concrete and the perforated steel plate, and effectively increases the shear strength of the bridge deck interface. This connection method better ensures the integrity of the bridge deck than simply embedding the steel plate.

[0012] Furthermore, the perforated steel plate has welding holes at its upper and lower ends, and the longitudinal and transverse reinforcing bars are connected to the welding holes, which increases the connection strength between the longitudinal and transverse reinforcing bars and the perforated steel plate. This effectively transmits the horizontal shear force at the interface of the composite bridge deck, prevents stress concentration at the interface, and ensures that the layers of the composite bridge deck are subjected to stress in a coordinated manner.

[0013] Furthermore, the steel beam has connection holes at both ends to facilitate subsequent assembly and positioning of the bridge.

[0014] Based on the same inventive concept, another aspect of the present invention provides a construction method for the above-mentioned prefabricated partially clad steel-UHPC composite bridge structure, the method comprising the following steps:

[0015] S1. Precast steel beam components:

[0016] Four inverted U-shaped shear members are gathered above the upper side of the bottom mold to form a square body, and are welded to the bottom mold to form a shear key unit;

[0017] Multiple shear key units are welded at intervals to the opening at the upper end of the steel beam; the bottom formwork and the inner side of the web of the steel beam enclose the casting space.

[0018] The reinforcing bars pass through the through holes in the web of the steel beam and are then welded to the steel beam; at least one of the reinforcing bars is connected to the square body;

[0019] A UHPC layer is poured onto the outer side of the steel beam using a formwork to cover the steel beam and the reinforcing bars.

[0020] S2, Precast bridge deck:

[0021] Longitudinal and transverse reinforcing bars are interwoven to form a reinforcing cage. A formwork is erected around the reinforcing cage, and a concrete layer is poured to form the bridge deck. Corresponding to the shear key unit, the bridge deck has a pre-cast groove, and the longitudinal and transverse reinforcing bars are bent downward at the post-cast groove.

[0022] S3. The hoisted steel beam components are placed in the designated positions; the connectors are used to initially fix adjacent steel beam components through the connection holes at the beginning and end of the steel beams;

[0023] S4. The bridge deck is hoisted and placed in the designated position by the shear key unit corresponding to the post-cast groove; the longitudinal and transverse steel bars bent downward at the post-cast groove are welded to the shear member respectively; concrete is poured into the post-cast groove to fill the casting space and the post-cast groove.

[0024] S5. Apply post-cast strip treatment to the two adjacent bridge deck sections.

[0025] Furthermore, the steel reinforcement cage fabrication step in S2 is as follows: longitudinal steel bars are welded to the upper and lower ends of a transversely arranged perforated steel plate, and transverse steel bars are welded to the upper and lower ends of a longitudinally arranged perforated steel plate. The longitudinal and transverse steel bars are interwoven and connected to form a double-layer bidirectional steel mesh to form a steel reinforcement cage.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The prefabricated partially clad steel-UHPC composite bridge structure provided by this invention adopts an interface connection design combining shear key units and post-cast grooves. The structural design is reasonable; the post-cast grooves, combined with the post-cast concrete, simultaneously complete the steel-concrete connection, providing excellent shear resistance at the slab-beam interface. This avoids problems such as easy cracking and weak shear resistance at wet joints of the bridge deck. The inverted U-shaped shear members, combined with the longitudinal and transverse steel reinforcement skeleton, connect the prefabricated bridge deck and steel beam components, leveraging the interlocking effect of the post-cast grooves to improve crack restraint performance between the new and old concrete interfaces, enhance the reliability of connections between prefabricated structures, and improve the tensile strength of the bridge deck. The above design has mechanical advantages such as lightweight and high strength, high interface shear strength, high overall stiffness, and reliable interface connection.

[0028] 2. The prefabricated partially clad steel-UHPC composite bridge structure provided by this invention adopts a three-layer composite structure of "UHPC-NSC-UHPC". It fully utilizes the lightweight, ultra-high compressive strength, good tensile properties, and durability of UHPC, and the economic performance of NSC. By rationally combining materials with different properties through layering, a complementary cross-sectional structure and mechanical design are formed. This composite concrete layer, combined with a double-layer bidirectional steel mesh and a perforated steel plate forming a reinforcing skeleton, vertically penetrates the NSC layer. The double-layer bidirectional steel mesh is firmly integrated with the upper and lower UHPC layers, fully leveraging the excellent tensile and deformation properties of steel. The structure is simple and reasonable, economical in cost, and maintains excellent mechanical and durability properties.

[0029] 3. The pre-reserved pouring space and post-pouring slot of the prefabricated partially covered steel-UHPC composite bridge structure provided by the present invention limit the amount of post-pouring concrete. The construction process does not require a large amount of wet pouring, which has the advantages of standardized production of components, short on-site operation time, easy control of construction quality, and low project cost. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall bridge structure according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the cross-sectional structure of a bridge deck according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of a steel beam component according to an embodiment of the present invention;

[0033] Figure 4 This is a partial schematic diagram of a steel beam component according to an embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram of a cross-section of a steel beam component according to an embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram of the connection between the shear key unit and the steel reinforcement cage according to an embodiment of the present invention;

[0036] Figure 7 This is a schematic diagram of a perforated steel plate according to an embodiment of the present invention;

[0037] Figure 8 This is a schematic diagram of the construction process according to an embodiment of the present invention.

[0038] Explanation of reference numerals in the attached figures:

[0039] 100. Steel beam component; 110. Steel beam; 111. Through hole; 112. Connecting hole; 120. Reinforcing bar; 130. Shear key unit; 131. Bottom formwork; 132. Shear member; 132A. Casting space; 132B. Cube; 140. UHPC layer.

[0040] 200 Bridge deck, 210 Steel reinforcement frame, 211 Perforated steel plate, 211A Perforation, 211B Welding hole, 220 Concrete layer, 221 First UHPC layer, 222 NSC layer, 223 Second UHPC layer, 230 Post-cast groove. Detailed Implementation

[0041] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the invention. It should be noted that the terms "set," "connect," and "install" should be interpreted broadly, for example, referring to direct connection, indirect connection, or integral connection. Those skilled in the art will understand the specific meaning of the above terms in the present invention according to the specific circumstances. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "vertical," "horizontal," "front," "rear," "left," "right," and similar expressions are for illustrative purposes only and do not represent the only embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains.

[0042] like Figure 1 As shown, the present invention provides a prefabricated partially covered steel-UHPC composite bridge structure, which is assembled from two separate components: an upper bridge deck 200 and a lower steel beam component 100. The bridge deck 200 is provided with a post-casting groove 230 for subsequent assembly with the steel beam component 100.

[0043] like Figure 2 As shown, the upper bridge deck 200 includes a steel reinforcement frame 210 and a concrete layer 220 covering the steel reinforcement frame 210. The steel reinforcement frame 210 includes interconnected longitudinal steel bars, transverse steel bars and perforated steel plates 211.

[0044] like Figure 7 As shown, a through hole 211A is provided in the middle of the perforated steel plate 211, and welding holes 211B are provided at the upper and lower ends of the perforated steel plate 211, respectively. The longitudinal and transverse reinforcing bars are connected to the welding holes 211B, respectively. For example, as shown... Figure 1 and Figure 2 As shown, longitudinal reinforcing bars are welded to the upper and lower ends of the transversely arranged perforated steel plate 211, and transverse reinforcing bars are welded to the upper and lower ends of the longitudinally arranged perforated steel plate 211. The perforated steel plate 211 supports and connects the longitudinal and transverse reinforcing bars, which interweave to form a double-layer, two-way reinforcing mesh, constituting the reinforcing steel skeleton 210. The thickness of the perforated steel plate 211 is 10mm-15mm, and its height is 80mm-100mm, with the specific height determined according to the thickness of the concrete layer. The diameter of the through holes 211A on the perforated steel plate 211 is 40-60mm, and the spacing of the through holes 211A is 80mm-180mm. The diameter of the welding holes 211B for welding reinforcing bars at the upper and lower edges is 14mm-18mm, and the spacing of the welding holes 211B is 80mm-180mm, consistent with the spacing of the through holes 211A. The perforated steel plates 211 are arranged longitudinally at a spacing of 300mm-400mm and transversely at a spacing of 350mm-450mm. The longitudinal and transverse reinforcing bars are of type HRB400, with a diameter of 10mm-12mm. The transverse reinforcing bars are spaced 8mm-14mm apart, and the longitudinal reinforcing bars are spaced 8mm-10mm apart. The longitudinal and transverse reinforcing bars are spot-welded to the perforated steel plate 211.

[0045] In one specific embodiment, such as Figure 2 As shown, the concrete layer 220 is composed of a combination of UHPC and NSC, including a first UHPC layer 221, an NSC layer 222, and a second UHPC layer 223 arranged sequentially from top to bottom; the thickness of the UHPC layer is 40mm-60mm, and the thickness of the NSC layer is 40mm-60mm. A perforated steel plate 211 penetrates the NSC layer 222 and connects to the first UHPC layer 221 and the second UHPC layer 223 respectively. A double-layer, bidirectional steel mesh is wrapped within the upper and lower UHPC layers. Multiple post-cast grooves 230 are provided on the bridge deck 200, and the longitudinal and transverse reinforcing bars are bent downwards at the post-cast grooves 230. The spacing between the post-cast grooves 230 is 300mm-500mm. The concrete around the reserved post-cast groove 230 is roughened to significantly improve the interfacial bond strength between the precast bridge deck and the cast-in-place concrete in the post-cast groove 230, increasing the effective contact area. This enhances the overall integrity of the bond between the precast bridge deck and the subsequent concrete poured in the post-cast groove 230, facilitating load transfer on the bridge deck 200 and effectively improving its seismic performance and durability. UHPC can be used for the concrete subsequently poured in the post-cast groove 230.

[0046] like Figure 3As shown, the steel beam member 100 below includes a steel beam 110 and reinforcing bars 120. The steel beam 110 is hollow and open at the top. For example, the steel beam 110 is a U-shaped steel beam made of HRB400 steel, with a length of 4000mm-5000mm, a width of 100mm-150mm, and a height of 400mm-1200mm. Figure 1 , 3 As shown in Figure 4, the steel beam 110 has connecting holes 112 at both ends as bolt interfaces for connecting adjacent steel beam components during subsequent assembly. The bolt interface spacing is 70mm-140mm, the bolt type is M20, and the bolt hole diameter is 22mm. The web of the steel beam 110 has through holes 111 with a diameter of 12mm-15mm, a transverse spacing of 15mm-20mm, and a longitudinal spacing of 10mm-20mm. The reinforcing bars 120 are of type HRB400, with a length of 110mm-175mm and a diameter of 10mm-12mm. The reinforcing bars 120 pass through the through holes 111 and are spot-welded to the steel beam 110.

[0047] like Figure 3 and 4 As shown, the outer side of the steel beam member 100 is covered with a UHPC layer 140, which covers the steel beam 110 and the reinforcing bars 120 passing through the web through-holes 111. This increases the overall strength of the steel beam member 100 and effectively prevents corrosion of the steel beam, reducing the risk of corrosion fatigue. For example, the reinforcing bars 120 pass through the web of the steel beam 110 at equal intervals laterally, and part of the web of the steel beam member 100 is covered with a UHPC layer with a thickness of 15mm-25mm.

[0048] like Figure 1 and Figure 3 As shown, multiple shear key units 130 are spaced apart at the upper opening of the steel beam 110; the shear key units 130 and the post-cast grooves 230 are matched one-to-one. Figure 4-6As shown, the shear key unit 130 includes a bottom mold 131 and four shear members 132. The bottom mold 131 is set at the upper opening of the steel beam 110 and surrounds the inner side of the web of the steel beam 110 to form a casting space 132A. For example, the bottom mold 131 is a steel profile bent into a U-shape, such as a channel steel with a U-shaped cross section and a thickness of 10mm. The lateral side length of the bottom mold 131 is the same as the inner width of the steel beam 110. The bent part of the bottom mold 131 is the front and rear ends. The bottom mold 131 is welded to the web of the steel beam 110 on the left and right sides and surrounds a rectangular open cavity, which is the casting space 132A. The shear member 132 is inverted U-shaped. Four shear members 132 are arranged above the upper side of the bottom formwork 131 to form a square body 132B. The height of the square body 132B is 100mm-120mm, and the length and width are 50mm-110mm. The lower end of the shear member 132 is welded to the bottom formwork 131. At least one of the reinforcing bars 120 passing through the web of the steel beam 110 passes through the casting space 132A and connects to the shear member 132 therein. Figure 4 As shown, a steel bar 120 is connected to a square body 132B formed by shear member 132. The connection method can be binding or welding. Shear member 132 and bottom formwork 131 are connected by triangular welding.

[0049] like Figure 6 As shown, the longitudinal and transverse reinforcing bars at the post-cast groove 230 on the square body 132B are respectively lapped with the longitudinal and transverse reinforcing bars at the post-cast groove 230, and the longitudinal and transverse reinforcing bars at the post-cast groove 230 are respectively spot welded with the inverted U-shaped shear member to form an integral structure.

[0050] The concrete mix proportions used for the UHPC layer 140, the first UHPC layer 221, and the second UHPC layer 223 in the aforementioned prefabricated partially clad steel-UHPC composite bridge structure can adopt the following specific proportions: 52.5R silicate cement content 773.2 kg / m³. 3 The silicon powder content for particles with a diameter of 5mm-270mm is 215.3kg / m³. 3 Silica fume content 78.2 kg / m³ 3 The content of quartz sand with a diameter of 400mm-800mm is 848.4kg / m³. 3 The content of quartz powder with a particle size of 52μm is 77.3 kg / m³. 3 Plasticizer content 20.1 kg / m³ 3 Mineral powder content 78.2 kg / m³ 3 Steel fiber content 118.6 kg / m 3 Water content 192 kg / m³ 3 The NSC layer uses commercial concrete with a concrete strength of C50.

[0051] like Figure 8As shown, another aspect of the present invention also provides a construction method for the above-mentioned prefabricated partially clad steel-UHPC composite bridge structure, comprising the following steps:

[0052] Construction of partially covered steel beams: S1-1, Precast open-type steel beams and drill holes in them. Weld the precast shear member units to the corresponding positions on the top surface of the open-type steel beams according to design requirements. Arrange reinforcing bars at the hole locations in the steel beams, and weld the holes to the reinforcing bars and tie the reinforcing bars to the inverted U-shaped shear members at the post-cast groove. S1-2, Erect formwork for the outer surface of the steel beams, and complete the factory casting, curing, and demolding of the UHPC outer covering layer.

[0053] The technical advantages of partially encased steel beams are as follows: 1. Factory construction is possible, effectively reducing costs and ensuring component quality; 2. Segmental assembly of the steel beams on-site effectively reduces the on-site construction period; 3. The outer UHPC layer protects the steel beam, preventing durability issues caused by steel corrosion; 4. Segmental assembly of the steel beams effectively reduces transportation difficulty and costs without affecting the overall structural integrity; 5. Perforated steel bars arranged on the steel beams effectively transfer shear stress at the interface between the outer UHPC layer and the steel beam, ensuring the integrity of the partially encased steel beams and effectively improving the overall strength of the steel beams.

[0054] Construction of precast UHPC-NSC-UHPC composite bridge deck: S2-1, Fabricate perforated steel plates and fix them to the corresponding positions on the composite bridge deck; S2-2, Fabricate the lower longitudinal and transverse steel mesh and spot weld it to the pre-drilled holes in the perforated steel plates; S2-3, Erect the composite bridge deck formwork in the factory and reserve the post-pouring slots according to the design requirements, then pour the second UHPC layer at the bottom; S2-4, Pour the NSC layer after the second UHPC layer reaches the design strength; S2-5, Fabricate the upper longitudinal and transverse steel mesh and spot weld it to the pre-drilled holes in the perforated steel plates; S2-6, Pour the uppermost first UHPC layer and cure it to the design strength.

[0055] Advantages of prefabricated UHPC-NSC-UHPC composite bridge deck technology: 1) The stress characteristics of this composite bridge deck project are that the upper and lower layers have high stress and the middle layer has low stress. Arranging the UHPC layer on the upper and lower surfaces can effectively utilize the mechanical advantages of UHPC's ultra-high compressive strength, good tensile performance, and durability, ensuring that the bridge deck structure has sufficient strength and durability; 2) Openings in the steel plates of the middle NSC layer effectively increase the shear area of ​​the middle layer interface. At the same time, the concrete at the opening forms a concrete tenon, which can further improve the interface shear strength between the NSC layer and the upper and lower layers, ensuring the overall performance of the bridge deck; 3) The longitudinal and transverse steel bars in the upper and lower UHPC layers are arranged in the perforated steel plates and spot-welded to the openings of the perforated steel plates. This design can effectively transfer the horizontal shear force at the interface and avoid stress concentration at the perforated steel plates. At the same time, the steel mesh of the upper and lower layers and the perforated steel plates form a steel skeleton, further ensuring the integrity and strength of the prefabricated UHPC-NSC-UHPC composite bridge deck.

[0056] Construction of the post-cast groove: S4-1. After the bridge deck is installed in place according to the design dimensions, the longitudinal and transverse steel bars at the post-cast groove of the precast bridge deck are bent down and spot-welded to the inverted U-shaped shear members in the shear key unit; S4-2. After the partial covering steel beam and bridge deck are assembled in place and the bolt holes at the ends of the steel beam are fixed, concrete is poured into the post-cast groove; S4-3. UHPC (ultra-high performance concrete) at the post-cast groove is cured on site.

[0057] Advantages of post-cast groove construction technology: 1. Less on-site wet work, and UHPC significantly reduces curing time compared to ordinary concrete, effectively shortening the bridge deck construction cycle; 2. Using UHPC as the casting material for post-cast grooves effectively improves the connection strength of the grooves, ensuring the overall performance of the prefabricated bridge structure; 3. The prefabricated post-cast groove structure design facilitates later bridge maintenance and replacement, simplifying operation and maintenance costs and reducing the later operation and maintenance construction cycle; 4. The design of the post-cast groove shear component unit effectively connects the various components of the steel beam and bridge deck in a multi-dimensional three-dimensional space, and the groove extends into the opening at the upper end of the steel beam, forming a sawtooth structure on the lower surface of the composite bridge deck. This design method improves the interface shear strength between the bridge deck and the steel beam and the overall integrity of the bridge deck structure, ensuring the full utilization of the mechanical advantages of each material.

[0058] This invention provides an embodiment illustrating the above construction steps, specifically, corresponding to the attached... Figure 1-6The construction process for each component is as follows: For precast steel beam component 100: Four inverted U-shaped shear members 132 are welded to the bottom formwork 131 to form shear key units 130. The shear members 132 enclose a square body 132B above the upper side of the bottom formwork 131. Multiple shear key units 130 are welded at intervals at the opening at the upper end of the steel beam 110. The bottom formwork 131 and the inner side of the web of the steel beam 110 enclose a casting space 132A. Reinforcing bars 120 pass through through holes 111 on the web of the steel beam 110 and are welded to the steel beam 110. The reinforcing bars 120 pass through the casting space 132A and connect to the square body 132B. A template is set along the outer contour of the web of the steel beam 110, and a 10mm-15mm thick UHPC protective layer is cast.

[0059] In the process of fabricating the precast steel beam component 100, firstly, the steel beam is prefabricated in a steel structure processing plant according to the design drawings. The bottom formwork 131 and the inverted U-shaped shear member 132 are precisely positioned and welded to the upper flange of the precast concrete space. Secondly, reinforcing bars 120 are inserted through holes drilled in the web of the steel beam 110, ensuring that at least one reinforcing bar 120 passes through the casting space 132A and is tied to the square body 132B. A formwork is then erected to cast the UHPC along the outer side of the web of the steel beam 110. HRB400 grade ribbed steel bars with good ductility are selected as the material for the shear member 132. During fabrication, the shear member is first segmented according to the drawings, namely the five sequentially connected main components of the inverted U-shaped shear member: the first vertical straight section, the first curved section, the transverse straight section, the second curved section, and the second vertical straight section. The diameter of the HRB400 grade ribbed steel bars used in the shear member 132 is 8mm-20mm. Figure 6 In the shear member located above the upper side of the bottom mold 131, the length of each vertical straight section is 120mm, the length of each horizontal straight section is 100mm, and the length of each curved section is 15mm. Then, the inverted U-shaped shear member 132 is triangularly welded.

[0060] Precast bridge deck 200: First, the mold is erected, the bottom layer of reinforcing mesh is laid, and perforated steel plates 211 are installed with pre-reserved post-casting slots 230. Then, the second UHPC layer 223 at the bottom is poured; next, the intermediate NSC layer 222 is poured; on top of the NSC layer 222, the UHPC layer formwork is erected, the top layer of reinforcing mesh is tied, and the first UHPC layer 221 is poured. The UHPC layer of the bridge deck 200 is steam-cured, while the NSC layer is naturally cured. Steam curing conditions: temperature 95-100℃, relative humidity approximately 95%. NSC layer curing conditions: temperature 20-25℃, relative humidity approximately 85%.

[0061] In the process of prefabricating the bridge deck 200, the composite bridge deck adopts a three-layer structure of "UHPC-NSC-UHPC". A 50mm thick UHPC layer, a 50mm thick NSC layer, and a 50mm thick UHPC layer are cast sequentially. A perforated steel plate 211 is pre-embedded in the NSC layer as a shear key. This shear key vertically penetrates the NSC layer, forming a firm connection with the upper and lower UHPC layers. A post-cast groove is reserved in the bridge deck 200, with longitudinal and transverse reinforcing bars of a certain length extending from the groove. The ends of the longitudinal and transverse reinforcing bars are bent towards the steel beam at 90 degrees. ° It is then welded to the inverted U-shaped shear member 132 during the subsequent assembly process, and the bridge deck 200 is cured to reach the design strength.

[0062] The precast steel beam component 100 and precast bridge deck 200 are in the factory prefabrication stage, where most of the concrete pouring is completed in the factory, reducing the amount of pouring required in the subsequent on-site assembly stage. After the shear connection welded parts pass inspection and all components have reached their design strength through steam curing, they will then enter the on-site assembly stage. The steel beam component 100 and bridge deck 200 will be hoisted to the construction site, with hoisting equipment selected based on the size and weight of the steel beam 110 and bridge deck 200 during transportation.

[0063] During the on-site assembly phase, steel beam component 100 is hoisted, and steel beam 110 is first assembled in segments. Steel beam component 100 is initially fixed in the designated position through the connecting holes 112 at the beginning and end of steel beam 110; bolt anchoring connections are used for initial fixation. Then, bridge deck 200 is hoisted; the post-cast groove 230 is accurately aligned with the shear key unit 130 on the steel beam component 100, and bridge deck 200 is hoisted and placed in the designated position; the downward-bent longitudinal and transverse reinforcing bars at the post-cast groove 230 are welded to the shear member 132. The post-cast interface is cleaned and moistened, and concrete is poured into the post-cast groove 230 to fill the casting space 132A. An immersion vibrator is used to ensure that the concrete fully fills all gaps inside and outside the inverted U-shaped shear member 132 and between the shear key unit 130 and the post-cast groove 230. Post-cast strips are then applied to adjacent bridge deck sections 200. The concrete poured at the 230mm post-cast groove and in the post-cast strip is UHPC. The post-cast UHPC will be covered with a membrane for thermal insulation curing. The curing conditions are: temperature 95-100℃, relative humidity approximately 95%, consistent with the factory prefabrication stage. Once the post-cast concrete reaches the design strength, such as when the post-cast UHPC strength reaches 120MPa, forming a high-strength, high-rigidity integral structural connection, the formwork can be removed.

[0064] The prefabricated partially clad steel-UHPC composite bridge structure provided by this invention has significant advantages such as reasonable structural design, short on-site operation time, easy control of construction quality, and low project cost. Simultaneously, this bridge structure also possesses mechanical advantages such as lightweight and high strength, high interfacial shear strength, high overall stiffness, and reliable interfacial connections.

[0065] The aforementioned composite bridge structure fully utilizes the excellent tensile and deformation properties of steel, the lightweight, ultra-high compressive strength, good tensile characteristics and durability of ultra-high performance concrete, and the economic performance of ordinary concrete through a rational cross-sectional design, forming a complementary cross-sectional design. This design holds promise for achieving the development goals of lightweight, prefabricated, and long-life bridge structures.

[0066] Compared to light steel structure prefabricated bridges, the prefabricated composite bridge decks used reduce the amount of steel used, which can effectively reduce project costs, reduce carbon emissions, and minimize the risk of steel bridge fatigue.

[0067] Its structural design is reasonable, facilitating factory prefabrication and effectively improving construction efficiency and shortening the construction period. Compared with traditional prefabricated concrete bridges, the amount of concrete used is significantly reduced, and the project cost is effectively controlled. At the same time, the processing and manufacturing of each component of this structure are convenient, enabling mass production. This effectively reduces the problems of high initial investment and low reuse rate of factory equipment.

[0068] The steel-UHPC composite bridge structure employs an interface connection design combining perforated steel plate shear keys and grooved post-casting. The perforated steel plate shear keys effectively transfer shear force through rebar connections, while the grooved post-casting enhances the integrity of the joint area, significantly improving the collaborative performance of all structural components. This approach solves the technical challenge of weak joints and interface failures affecting the overall structural performance of novel prefabricated steel-concrete composite bridges.

[0069] The steel-clad UHPC structural system significantly reduces the amount of concrete used compared to traditional structures, has a simple and reasonable construction, and is economical in cost, while maintaining excellent mechanical and durability properties, making it a promising candidate for application in bridge engineering.

[0070] The foregoing has provided a detailed description of the prefabricated partially clad steel-UHPC composite bridge structure and its construction method provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are merely for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A prefabricated partially clad steel-UHPC composite bridge structure, comprising steel beam members and bridge deck, wherein the bridge deck comprises a steel reinforcement skeleton and a concrete layer covering the steel reinforcement skeleton, wherein the steel reinforcement skeleton comprises interconnected longitudinal and transverse steel reinforcements; Its features are, The steel beam component includes steel beams, reinforcing bars, and a UHPC layer; The web of the steel beam has through holes, through which the reinforcing bars pass and connect to the steel beam; the outer side of the steel beam is covered with the UHPC layer. The steel beam has an opening at the top, and multiple shear key units are spaced apart at the opening. The shear key unit includes a bottom formwork and four shear members; the bottom formwork is located at the upper opening of the steel beam and forms a casting space with the inner side of the web of the steel beam; the shear members are inverted U-shaped; the shear members form a square shape above the upper side of the bottom formwork and are connected to at least one steel bar, and are embedded in the post-cast concrete; the lower end of the shear members is connected to the bottom formwork; The bridge deck has multiple post-cast slots, and the shear key unit and the post-cast slot are matched one-to-one. The transverse and longitudinal sides of the square body overlap with the longitudinal and transverse reinforcing bars, respectively.

2. The prefabricated partially clad steel-UHPC composite bridge structure according to claim 1, characterized in that, The concrete layer includes a first UHPC layer, an NSC layer, and a second UHPC layer arranged sequentially from top to bottom; the reinforcing steel frame also includes a perforated steel plate; the perforated steel plate supports and connects the longitudinal reinforcing bars and the transverse reinforcing bars so that the reinforcing steel frame forms a double-layer bidirectional reinforcing steel mesh; the perforated steel plate penetrates the NSC layer and is connected to the first UHPC layer and the second UHPC layer respectively.

3. The prefabricated partially clad steel-UHPC composite bridge structure according to claim 2, characterized in that, The perforated steel plate has a perforation in the middle.

4. The prefabricated partially clad steel-UHPC composite bridge structure according to claim 2, characterized in that, The perforated steel plate has welding holes at its upper and lower ends, and the longitudinal and transverse reinforcing bars are connected to the welding holes respectively.

5. The prefabricated partially clad steel-UHPC composite bridge structure according to any one of claims 1-4, characterized in that, The steel beam has connection holes at both ends.

6. A construction method for a prefabricated partially clad steel-UHPC composite bridge structure as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Precast steel beam components: Four inverted U-shaped shear members surround a square body on the upper side of the bottom mold and are welded to the bottom mold to form a shear key unit; Multiple shear key units are welded at intervals to the opening at the upper end of the steel beam; the bottom formwork and the inner side of the web of the steel beam enclose the casting space. The reinforcing bars pass through the through holes in the web of the steel beam and are then welded to the steel beam; at least one of the reinforcing bars is connected to the square body; A UHPC layer is poured on the outer side of the steel beam using a formwork, so that the UHPC layer covers the steel beam and the reinforcing bars; S2, Precast bridge deck: Longitudinal and transverse reinforcing bars are interwoven to form a reinforcing cage; formwork is erected around the reinforcing cage, and a concrete layer is poured to form the bridge deck; wherein, corresponding to the shear key unit, the bridge deck is reserved with a post-casting groove, and the longitudinal and transverse reinforcing bars are bent downward at the post-casting groove; S3. The hoisted steel beam components are placed in the designated positions; the connectors are used to initially fix adjacent steel beam components through the connection holes at the beginning and end of the steel beams; S4. The bridge deck is hoisted and placed in the designated position by the shear key unit corresponding to the post-cast groove; the longitudinal and transverse steel bars bent downward at the post-cast groove are welded to the upper end of the shear member respectively; concrete is poured into the post-cast groove to fill the casting space and the post-cast groove. S5. Apply post-cast strip treatment to the two adjacent bridge deck sections.

7. The construction method for the prefabricated partially clad steel-UHPC composite bridge structure according to claim 6, characterized in that, The steps for fabricating the reinforcing steel cage in S2 are as follows: longitudinal reinforcing bars are welded to the upper and lower ends of a transversely arranged perforated steel plate, and transverse reinforcing bars are welded to the upper and lower ends of a longitudinally arranged perforated steel plate. The longitudinal and transverse reinforcing bars are interwoven and connected to form a double-layer bidirectional reinforcing steel mesh to form the reinforcing steel cage.

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