A high-strength steel-UHPC composite beam reinforced with FRP and its construction method

Abstract

This invention relates to an FRP-reinforced high-strength steel-UHPC composite beam and its construction method, comprising a steel beam, a base plate, a connecting base, shear connectors, high-strength transverse reinforcement, longitudinal reinforcement, and UHPC concrete. The base plate is spliced ​​and assembled on top of multiple spaced steel beams, with its splice joint located at the center of the steel beams. An FRP extruded profile plate is fitted and fixedly installed on the upper part of the base plate. The connecting base is fixed on the upper part of the splice joint. The high-strength transverse reinforcement is arranged at intervals along the transverse direction, having concave sections approaching the base plate and convex sections moving away from the base plate, with the convex and concave sections connected by a smooth transition section. The longitudinal reinforcement is FRP high-strength reinforcement and is fixedly connected between the high-strength transverse reinforcement to form a steel reinforcement skeleton structure. UHPC concrete covers the base plate, embedding the steel reinforcement skeleton structure within it. This invention combines FRP-reinforced high-strength steel and UHPC concrete in a composite beam, fully utilizing the material's structural characteristics to reduce the cost of steel composite beams and facilitating the widespread use of steel-concrete composite structures.

Description

Technical Field

[0001] This invention relates to the field of composite beam technology, specifically to an FRP-reinforced high-strength steel-UHPC composite beam and its construction method. Background Technology

[0002] Composite beams are transverse load-bearing members that combine steel beams and concrete slabs through shear connectors to share the load. They fully utilize the advantages of steel's tensile strength and concrete's compressive strength, resulting in high load-bearing capacity, high stiffness, good seismic and dynamic performance, small component cross-sectional dimensions, and convenient construction. Existing composite beams utilize steel beams in various forms, including I-beams, box girders, steel trusses, and honeycomb steel beams.

[0003] A beam composed of two different materials or different construction processes is called a composite beam, also known as a combined beam. Some main beams are made of one material, while the bridge deck connecting the main beams is made of another material; there are also composite beams composed of precast reinforced concrete beams or prestressed concrete beams and in-situ cast reinforced concrete bridge decks.

[0004] FRP pultruded profiles have advantages such as light weight, high strength-to-weight ratio, good durability, strong corrosion resistance, and low maintenance costs. They have broad application prospects in new energy, rail transportation, environmental protection, petrochemical, power, construction, papermaking, steel and other fields, and show great potential in bridge engineering.

[0005] UHPC has a much higher strength than traditional concrete, reaching over 200 MPa; it has excellent density, effectively preventing water and gas penetration. UHPC has excellent durability, resisting the effects of harsh environments such as chloride ions and carbon dioxide. UHPC has excellent crack resistance, effectively preventing concrete from cracking and fracturing; UHPC has good fluidity and plasticity, allowing it to be easily constructed into components of various shapes and sizes.

[0006] In existing technologies, the composite beam structure with upper steel mesh and shear connectors typically involves horizontally arranging the steel mesh while the shear connectors are haphazardly and extensively fixed to the floor. As the composite beam is subjected to forces acting along the direction of the shear connectors, it is prone to fracture when subjected to longitudinal shear forces, resulting in limited structural strength that fails to meet current requirements. Therefore, it is necessary to research an FRP-reinforced high-strength steel-UHPC composite beam and its construction method. Summary of the Invention

[0007] Therefore, the purpose of this invention is to provide an FRP-reinforced high-strength steel-UHPC composite beam and its construction method, which effectively solves the problem of limited strength of existing composite beams.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: an FRP-reinforced high-strength steel-UHPC composite beam, comprising a steel beam, a base plate, a connecting base, shear connectors, high-strength transverse reinforcement, longitudinal reinforcement, and UHPC concrete;

[0009] The base plate is spliced ​​and assembled on the upper part of multiple steel beams arranged at intervals, and its splice seam is located at the center of the steel beams.

[0010] An FRP extruded profile plate is fitted and fixedly installed on the upper part of the base plate;

[0011] The connecting base is fixed to the upper part of the splice joint and is fixed to the base plate and steel beam;

[0012] The high-strength transverse ribs are arranged at intervals along the transverse direction. They have concave sections that are close to the bottom plate and convex sections that are far away from the bottom plate. The convex sections and concave sections are connected by a smooth transition section. The concave sections are fixed to the upper center of the connecting base by bolts.

[0013] The shear-resistant connector is fixed to the base plate and corresponds to the protruding section;

[0014] The longitudinal bars are FRP high-strength bars and are fixedly connected between the high-strength transverse bars to form a steel reinforcement skeleton structure.

[0015] The UHPC concrete covers the base slab and embeds the steel reinforcement skeleton structure within it.

[0016] Furthermore, the FRP high-strength ribs are arranged on the concave section except for the high-strength transverse rib fixing points, and are fixed by fasteners.

[0017] Furthermore, the high-strength transverse ribs are fixed to the connecting base by one or two bolts, and two shear-resistant connectors are provided in each protruding section.

[0018] Furthermore, the bottom of the connecting base is provided with an ear plate, which is adapted to the edge of the steel beam, and the ear plate, the base and the steel beam are connected and fixed together by fixing bolts extending along the length of the ear plate.

[0019] Furthermore, the base plate has grooves on its sides, and the grooves on both sides of the base plate form mounting grooves. The base is fitted into the mounting grooves and fixed with fixing bolts.

[0020] Furthermore, the upper surface of the FRP extruded profile sheet is provided with an uneven rough surface; the steel beam is an I-beam, and the base is a frustum-shaped structure made of steel or precast concrete.

[0021] Furthermore, the high-strength transverse ribs are alternating concave and convex structures formed by bending sheet-like structures.

[0022] Furthermore, the high-strength transverse reinforcement is a columnar steel bar structure, which is bent to form a wavy structure. Fixing plates are provided on both sides of the trough of the wavy steel bar connection point, and the fixing plates are fixed to the base by bolts.

[0023] Furthermore, connecting ribs are also provided between the FRP high-strength ribs, and limit holes or butt ribs are provided on the side of the connecting base. The connecting ribs are tied to the upper part of the longitudinal ribs, and their ends are fixed to the limit holes or butt ribs.

[0024] A construction method for FRP-reinforced high-strength steel-UHPC composite beams includes the following steps:

[0025] Step 1: Construction of the base slab

[0026] The prefabricated base plate is placed on top of the I-beam and spliced ​​together into a whole plate; sealing gaskets or sealant are placed at the splice joints; then the FRP extruded profile plate is fixed on the base plate and shear connectors are added to reinforce the FRP extruded profile plate.

[0027] Step 2: Install the connecting base

[0028] The connecting base is installed in the middle of the splice joint, and then the connecting base, the base plate and the flange of the I-beam are fixed by bolts; the connecting base is a frustum-shaped structure and its width is adapted to the width of the I-beam.

[0029] Step 3: Fix the high-strength transverse reinforcement.

[0030] According to the construction schedule, the concave sections of the high-strength transverse reinforcement are arranged on the connecting base and then fixed with bolts; in this state, the shear connector integrally set on the base plate faces the protruding section.

[0031] Step 4: Reinforce FRP high-strength ribs

[0032] The FRP high-strength reinforcement is connected to the high-strength horizontal reinforcement. The FRP high-strength reinforcement is arranged on the concave section except for the fixing point of the high-strength horizontal reinforcement, and is fixed by fasteners.

[0033] Step 5: Pour UHPC concrete

[0034] Support the side formwork on the base, and use the side formwork and the base plate to form the inner cavity for casting. Pour UHPC concrete into the inner cavity, and finally carry out the surface layer construction.

[0035] The beneficial effects of the above technical solution are as follows: In terms of structure, the present invention arranges the base plate on the upper part of the spaced steel beams, thereby forming a continuous base support structure on the upper part of the steel beams, and arranges FRP extruded profile plates on the base plate; the FRP extruded profile plates are lightweight, have a high strength-to-weight ratio, good durability, and strong corrosion resistance, and are fixedly connected to the base plate and have a rough surface.

[0036] To ensure structural airtightness, connecting bases are installed at the splice joints of the base plate. The connecting bases can seal the splice joints, ensuring the connection strength and airtightness at this time. At the same time, the connecting bases also serve as the basis for arranging high-strength horizontal reinforcement bars, allowing the high-strength horizontal reinforcement bars to be arranged at intervals on the upper part of the base plate. After the concrete is poured, the steel reinforcement skeleton structure is embedded in the concrete.

[0037] In this invention, the high-strength transverse reinforcement is arranged at intervals on the connecting base. Structurally, it has concave sections and convex sections, with a smooth transition between the two parts. The bottom of the concave section is fixed to the base, and a shear-resistant connector is provided on the base plate corresponding to the convex section. In terms of structural features, for the transverse of the steel reinforcement skeleton structure, there is a structure in which the concave section and the shear-resistant connector are arranged alternately. The two together bear the inner frame structure, which reduces the number of shear-resistant connectors and can also ensure the structural strength.

[0038] Meanwhile, the present invention also provides connecting bars corresponding to the high-strength transverse bars in the longitudinal bars. Through this structure, the arrangement of high-strength transverse bars can be appropriately reduced. The connecting bars form a planar steel mesh structure, while the high-strength transverse bars protrude from the planar steel mesh structure, thus forming a structure in which planar bars and protrusions alternate. This structure can improve the strength of the bottom layer of steel bars in the structure. The protrusions and shear-resistant connectors together form a shear-resistant component, which greatly improves the strength of the structure.

[0039] Since steel structures excel at tensile strength, they only need to accommodate shear studs. This invention utilizes a web and a base plate, with shear-resistant members on the base plate and reinforced support bases at the joints, where high-strength transverse reinforcements are installed. This structure saves on the cost of shear key structures, reduces the cost of steel composite beams, and facilitates the widespread use of steel-concrete composite structures. The resulting composite beam bridge has a smaller bridge deck size, lower self-weight, and stronger spanning capacity, offering advantages in lightweight construction. Furthermore, this invention integrates FRP-reinforced high-strength steel with UHPC concrete into the composite beam, fully utilizing the material's structural characteristics. The built-in high-strength skeleton significantly increases the structure's shear strength, preventing bridge deck fracture. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the internal structure of the present invention;

[0041] Figure 2 for Figure 1 Front view structural diagram;

[0042] Figure 3 for Figure 1 A schematic diagram of the side view structure;

[0043] Figure 4 for Figure 1 A top-view structural diagram;

[0044] Figure 5 This is a schematic diagram of the construction structure of the present invention;

[0045] Figure 6 This is a structural diagram of the fixed plate;

[0046] Figure 7 This is a schematic diagram of the implementation structure of the connecting reinforcement.

[0047] Attached reference numerals: 1 is steel beam, 2 is base plate, 3 is connecting base, 4 is ear plate, 5 is shear connector, 6 is high-strength transverse reinforcement, 61 is concave section, 62 is convex section; 7 is FRP high-strength reinforcement, 8 is fixing bolt, 9 is UHPC concrete, 10 is FRP extruded profile plate, 11 is high-strength steel reinforcement, 12 is fixing plate, 13 is connecting reinforcement, 14 is connector. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0049] Example 1: This example aims to provide an FRP-reinforced high-strength steel-UHPC hybrid composite beam for composite beam structures. Addressing the problem of poor transverse shear resistance and subsequent fractures in existing composite beams, this example combines the material properties of FRP and UHPC and utilizes them in the composite beam, thus providing an FRP-reinforced high-strength steel-UHPC hybrid composite beam.

[0050] like Figure 1-5 The image shows an FRP-reinforced high-strength steel-UHPC composite beam, comprising a steel beam 1, a base plate 2, a connecting base 3, shear connectors 5, high-strength transverse reinforcement 6, FRP high-strength reinforcement 7, and UHPC concrete 9. In this embodiment, the steel beam 1 is an I-beam 1, with multiple I-beams 1 arranged in parallel at intervals. The base plate 2 is spliced ​​and assembled on the upper part of the multiple spaced steel beams 1, and its splice joint is located at the center of the steel beam 1. In the specific implementation structure, the bottom of the connecting base 3 is provided with an ear plate 4, which is adapted to the edge of the steel beam 1. The ear plate 4, the base plate, and the steel beam 1 are connected and fixed together by fixing bolts 8 extending along the length of the ear plate 4. This structure can ensure the sealing of the joint of the base plate 2 and avoid grout leakage at the bottom during concrete pouring.

[0051] Structurally, in this embodiment, an FRP extruded profile plate is fitted and fixedly installed on the upper part of the base plate. The upper part of the FRP extruded profile plate is provided with an uneven rough surface 10. This rough surface enables the connection and assembly with the UHPC concrete 9, so that it can fully contact the poured UHPC concrete 9 and ensure the strength and connectivity of the structure.

[0052] The connecting base 3 is fixed to the upper part of the splice joint and is fixed to the base plate 2 and the steel beam 1. In implementation, the base of the structure is a frustum-shaped structure made of steel or precast concrete. The upper surface of the base plate 2 is provided with uneven mating surfaces, and the FRP extruded profile plate is spliced ​​on the mating surfaces accordingly.

[0053] In a further connection structure, grooves are provided on the sides of the base plate 2, and the grooves on both sides of the base plate 2 form mounting grooves. The base is adapted to be installed in the mounting grooves and fixed by fixing bolts, such as... Figure 1 As shown, the connecting base 3 has ear plates 4 on both sides, which correspond to the two side flanges of the I-beam 1, while the middle part of the connecting base 3 is directly opposite the web of the I-beam 1. The ear plates are nested in the mounting grooves and are connected and assembled together by through fixing bolts. Sealing gaskets are applied to the end areas of the fixing bolts to ensure the sealing of the connection.

[0054] High-strength transverse reinforcement 6 is arranged at intervals along the transverse direction. It has a concave section 61 that approaches the base plate 2 and a convex section 62 that moves away from the base plate 2. The convex section 62 and the concave section 61 are connected by a smooth transition section. The concave section 61 is fixed to the upper center of the connecting base 3 by bolts. In this embodiment, the connecting base 3 is used as the fixed foundation. The high-strength transverse reinforcement 6 is arranged vertically on the connecting base 3. In terms of structural correspondence, the connecting base 3 is arranged along the extension direction of the web of the I-beam 1, while the high-strength transverse reinforcement 6 is perpendicular to this direction and is arranged at intervals on the connecting base 3. In this structure, the high-strength transverse reinforcement 6 is fixed to the connecting base 3 by one or two bolts, so that the high-strength transverse reinforcement 6 is higher than the base plate 2 and is basically located in the middle area of ​​the poured concrete.

[0055] like Figure 5 As shown, UHPC concrete 9 covers the base plate 2 and embeds the steel reinforcement skeleton structure within it. The longitudinal reinforcement is FRP high-strength reinforcement and is arranged on the concave section except for the fixing point of the high-strength transverse reinforcement 6. Structurally, the shear connector 5 is fixed on the base plate 2 and corresponds to the protruding section. The FRP high-strength reinforcement 7 is connected between the high-strength transverse reinforcement 6 to form the steel reinforcement skeleton structure.

[0056] In this embodiment, the shear connector 5 preferably adopts the form of a bolt-head type columnar bolt. Two shear connectors 5 are provided in each protruding section. Structurally, the shear connector 5 is basically flush with the upper edge of the bolt used to fix the high-strength transverse reinforcement 6. Thus, in this embodiment, a first shear assembly composed of the shear connector and the protruding section is formed, a second shear assembly composed of the connecting base 3 and the concave section is formed, and a third shear assembly composed of the FRP high-strength reinforcement 7 and the concave section is formed. By arranging these three types of shear assemblies alternately, the shear performance of the composite beam can be significantly improved.

[0057] In this embodiment, a construction method for FRP-reinforced high-strength steel-UHPC composite beams is also provided, which specifically includes the following steps:

[0058] Step 1: Construct base plate 2;

[0059] The prefabricated base plate 2 is placed on top of the I-beam 1 and spliced ​​together to form a whole plate. The base plate 2 is a prefabricated plate structure. To ensure sealing, sealing gaskets or sealant are placed at the splice joints. Then, the FRP extruded profile plate is fixed on the base plate and shear connectors are added to reinforce the FRP extruded profile plate.

[0060] Step 2, install connecting base 3;

[0061] The connecting base 3 is installed in the middle of the splice joint, and then the connecting base 3, the base plate 2 and the flange of the I-beam 1 are fixed by bolts; the connecting base 3 selected during construction is a frustum-shaped structure, and its width is adapted to the width of the I-beam 1.

[0062] Step 3: Fix the high-strength transverse reinforcement 6;

[0063] According to the construction schedule, the concave section of the high-strength transverse reinforcement 6 is arranged on the connecting base 3 and then fixed with bolts; in this state, the shear connector 5 integrally set on the base plate 2 is directly opposite the protruding section.

[0064] Step 4: Reinforce with FRP high-strength ribs 7;

[0065] The FRP high-strength rib 7 is connected to the high-strength transverse rib 6. The FRP high-strength rib is arranged on the concave section except for the fixing point of the high-strength transverse rib and is fixed by fastener. Alternatively, the FRP high-strength rib 7 and the high-strength transverse rib 6 can be assembled as a whole and then hoisted onto the connecting base 3.

[0066] Step 5: Pour concrete;

[0067] Support the side formwork on the base, and use the side formwork and the base plate to form the inner cavity for casting. Pour UHPC concrete into the inner cavity, and finally carry out the surface layer construction.

[0068] In this embodiment, the high-strength transverse reinforcement 6 is a sheet-like structure formed by bending, resulting in an alternating concave and convex shape. The FRP high-strength reinforcement 7 is a columnar structure. The high-strength transverse reinforcement 6 is made of sheet steel bent into a flat cross-section. The high-strength transverse reinforcement 6 is arranged at intervals on the connecting base 3. Structurally, it has concave sections and convex sections, with a smooth transition between the two parts. Both the convex and concave sections are platform structures, forming an isosceles trapezoidal structure with the inclined transition section. The bottom of the concave section is fixed to the base, and a shear connector 5 is provided on the base plate 2 corresponding to the convex section. In terms of structural features, for the transverse direction of the steel reinforcement skeleton structure, there is a structure in which the concave section and the shear connector are arranged alternately. The two together bear the inner frame structure, reducing the number of shear connectors 5 and ensuring structural strength.

[0069] Example 2 further illustrates the structure of the high-strength transverse rib 6.

[0070] In this embodiment, the high-strength horizontal reinforcement 6 is a columnar steel bar structure, which is bent to form a wavy structure. The FRP high-strength reinforcement 7 is a straight reinforcement structure. Fixing plates are provided on both sides of the trough of the wavy reinforcement connection point. The fixing plates are fixed to the base by bolts.

[0071] In this embodiment, connecting bars are also provided between the FRP high-strength ribs 7. Limiting holes or butt bars are provided on the side of the connecting base 3. The connecting bars are tied to the upper part of the FRP high-strength ribs 7, and their ends are fixed to the limiting holes or butt bars. This structure can appropriately reduce the arrangement of high-strength transverse ribs 6. The connecting bars form a planar steel mesh structure, while the high-strength transverse ribs 6 protrude from the planar steel mesh structure, thus forming a structure in which planar ribs and protrusions alternate. This structure can improve the strength of the bottom steel reinforcement of the structure. The protrusions and shear connectors 5 together form a shear component, which greatly improves the strength of the structure.

[0072] During implementation, the high-strength transverse reinforcement 6 is FRP high-strength steel, and the concrete is steel fiber high-strength concrete. The FRP steel fiber high-strength concrete structure formed by the combination of FRP reinforcement and steel fiber high-strength concrete can enhance the bonding performance between FRP reinforcement and concrete, delay the cracking and crack propagation of FRP reinforced concrete beams, and increase the cross-sectional stiffness of FRP reinforced concrete beams.

[0073] Example 3 further illustrates the structure of the shear connector.

[0074] In this embodiment, a connector is also provided at the bottom of the concave section 61, and a connecting sleeve is provided on the base plate. The connector 14 can pass through the concave section 61 and connect to the connecting sleeve. The connector 14 limits the concave section 61 on the base plate 2, further improving the stability of the structure and having a limiting function, so that a certain structural connection is established between the steel frame and the base plate, preventing longitudinal shear fracture of the composite beam.

Claims

1. A composite beam made of FRP-reinforced high-strength steel and UHPC, characterized in that, Includes steel beams, base plate, connecting base, shear connectors, high-strength transverse reinforcement, longitudinal reinforcement and UHPC concrete; The base plate is spliced ​​and assembled on the upper part of multiple steel beams arranged at intervals, and its splice seam is located at the center of the steel beams. An FRP extruded profile plate is fitted and fixedly installed on the upper part of the base plate; The connecting base is fixed to the upper part of the splice joint and is fixed to the base plate and steel beam by fixing bolts; The steel beam is an I-beam; The high-strength transverse ribs are arranged at intervals along the web extension direction of the I-beam, and have concave sections that are close to the bottom plate and convex sections that are far away from the bottom plate. The convex sections and concave sections are connected by a smooth transition section, and the concave sections are fixed to the upper center of the connecting base by bolts. The shear connector is fixed to the base plate and corresponds to the protruding section. Two shear connectors are provided below each protruding section. The longitudinal bars are FRP high-strength bars and are fixedly connected between the high-strength transverse bars to form a steel reinforcement skeleton structure. The UHPC concrete covers the base slab and embeds the steel reinforcement skeleton structure within it.

2. The FRP-reinforced high-strength steel-UHPC composite beam according to claim 1, characterized in that: The FRP high-strength ribs are arranged on the concave section except for the high-strength transverse rib fixing points, and are fixed by fasteners.

3. The FRP-reinforced high-strength steel-UHPC composite beam according to claim 1, characterized in that: The high-strength transverse ribs are fixed to the connecting base by one or two bolts, and two shear-resistant connectors are provided in each protruding section.

4. The FRP-reinforced high-strength steel-UHPC composite beam according to claim 1, characterized in that: The bottom of the connecting base is provided with an ear plate, which is adapted to the edge of the steel beam. The ear plate, the connecting base and the steel beam are connected and fixed together by fixing bolts extending along the length of the ear plate.

5. The FRP-reinforced high-strength steel-UHPC composite beam according to any one of claims 1-4, characterized in that: The base plate has grooves on its sides, and the grooves on both sides of the base plate form mounting grooves. The connecting base is fitted into the mounting grooves and fixed by fixing bolts.

6. The FRP-reinforced high-strength steel-UHPC composite beam according to claim 5, characterized in that: The upper surface of the FRP extruded profile sheet is provided with an uneven rough surface; the steel beam is an I-beam, and the connecting base is a frustum-shaped structure made of steel or precast concrete.

7. The FRP-reinforced high-strength steel-UHPC composite beam according to claim 1, characterized in that: The high-strength transverse ribs are formed by bending sheet-like structures into an alternating concave-convex structure.

8. The FRP-reinforced high-strength steel-UHPC composite beam according to claim 1, characterized in that: The high-strength transverse reinforcement is a columnar steel bar structure, which is bent to form a wavy structure. Fixing plates are provided on both sides of the trough of the wavy steel bar connection point, and the fixing plates are fixed to the connecting base by bolts.

9. The FRP-reinforced high-strength steel-UHPC composite beam according to claim 7 or 8, characterized in that: Connecting bars are also provided between the FRP high-strength bars, and the connecting bars are tied to the upper part of the longitudinal bars.

10. A construction method for FRP-reinforced high-strength steel-UHPC composite beams, characterized in that, Includes the following steps, Step 1: Construction of the base slab The prefabricated base plate is placed on top of the I-beam and spliced ​​together into a whole plate; sealing gaskets or sealant are placed at the splice joints; then the FRP extruded profile plate is fixed on the base plate and shear connectors are added to reinforce the FRP extruded profile plate. Step 2: Install the connecting base The connecting base is installed in the middle of the splice joint, and then the connecting base, the base plate and the flange of the I-beam are fixed by bolts; the connecting base is a frustum-shaped structure and its width is adapted to the width of the I-beam. Step 3: Fix the high-strength transverse reinforcement. According to the construction schedule, the concave sections of the high-strength transverse reinforcement are arranged on the connecting base and then fixed with bolts; in this state, the shear connector integrally set on the base plate faces the protruding section. Step 4: Reinforce FRP high-strength ribs The FRP high-strength reinforcement is connected to the high-strength horizontal reinforcement. The FRP high-strength reinforcement is arranged on the concave section except for the fixing point of the high-strength horizontal reinforcement, and is fixed by fasteners. Step 5: Pour UHPC concrete Side formwork is erected on the base plate, and the side formwork and base plate form a casting cavity. UHPC concrete is injected into the casting cavity, and finally the surface layer is constructed.

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