Core column plate end steel bar anchoring and rib end reinforcing structure

Abstract

The invention discloses a core column plate end steel bar anchoring and rib end reinforcing structure which is suitable for a high-altitude heart rate UHPC core column plate and an assembly type modular floor system. According to the structure, in a certain range close to a support, a plurality of core columns and ribs are transited from hollow sections to solid or semi-solid sections, and anchoring expanded end rib areas are formed through rib end widening; and the tensile longitudinal steel bars are provided with mechanical anchor heads or closed hooks in the section, and are restrained by being matched with small-diameter stirrups or short U-shaped ribs. An integrated prefabricated end beam or corner beam is wrapped outside the anchoring expanded end rib area and used for connecting bolts or sleeve anchoring, reliable assembly of the module units is achieved, and stress safety in the transportation and hoisting stages is guaranteed. On the premise that the high-altitude heart rate and light weight of the middle ribs and the core columns are kept, sliding and crack propagation of the ends of the tensile steel bars are effectively restrained, and the method is suitable for being applied to large-span high-performance assembly type floor systems and bridge deck slabs.

Description

An anchorage and rib end reinforcement structure for the end of a core column plate Technical Field

[0001] This invention relates to the field of prefabricated structure technology of ultra-high performance concrete (UHPC), specifically to an end anti-slip steel bar anchorage and rib end reinforcement structure for high-hollow-ratio UHPC core column slabs, which is particularly suitable for prefabricated prefabricated structures such as large-span modular floor slabs and bridge decks. Background Technology

[0002] Ultra-high performance concrete (UHPC) is characterized by high strength, high durability, and good ductility, and has been widely used in bridges, prefabricated buildings, and lightweight floor systems in recent years. Using UHPC and arranging core columns and ribs in the cross-section to form a high-hollow-ratio core column slab structure can significantly reduce self-weight and improve structural stiffness and integrity, making it suitable for engineering scenarios such as large spans, long cantilever structures, and modular assembly.

[0003] However, high-hollow-ratio UHPC core slabs typically employ a large proportion of hollow sections in the middle to reduce weight, resulting in a limited length of solid zone near the supports for anchoring the longitudinal tensile reinforcement. In actual bending members, the tensile reinforcement at the slab ends needs to complete stress transfer within a finite length. If only the anchorage length and structural requirements of ordinary concrete members are applied, problems such as insufficient anchorage, bond slippage of the reinforcement relative to the UHPC matrix, premature initiation of end cracks, and propagation towards the mid-span can easily occur. Although the bond strength between UHPC and reinforcement is higher, once slippage occurs, the failure is relatively brittle, which is detrimental to the safety of prefabricated modules during transportation, hoisting, and service.

[0004] In existing technologies, the anchorage performance of UHPC components is improved through the following methods: first, simply extending the length of the solid end section or increasing the overall cross-sectional size; second, setting anchor plates, adding steel components, or densifying ordinary stirrups at the end; and third, using post-cast sections, shear keys, and other joint structures. These measures have a certain effect on conventional solid beams and slabs or locally reinforced beam-column joints. However, for high-hollow-ratio UHPC core columns and slabs where weight reduction is the primary goal, blindly extending the solid end section or thickening the entire structure will significantly reduce the hollow-ratio and lightweight advantages. Simply increasing the reinforcement makes it difficult to fully utilize the high bonding capacity of UHPC within the limited structural height, and it is also not conducive to the factory prefabrication, transportation, and rapid assembly of standardized modules and modular units.

[0005] In addition, existing end reinforcement structures often separate the anchorage of tensile reinforcement from the modular connection structure: the end reinforcement is mainly designed for the bending bearing capacity under normal use and ultimate state, while the end beams or corner beams between modules are arranged independently, resulting in complex reinforcement and cross-sectional forms in the end areas of the components, making it difficult to balance reasonable stress, simple structure and convenient assembly construction.

[0006] Therefore, there is an urgent need to propose a special end structure for high-hollow-ratio UHPC core column slabs. Without changing the central hollow ratio, a highly efficient anchoring expansion rib zone can be formed by widening the local rib ends and solidifying the cross-section, combined with mechanical anchor heads or closed hooks and restraining reinforcement. This anchoring zone can then be organically integrated with the integrated precast end beam or corner beam. This not only suppresses the slippage of tensile reinforcement and the propagation of end cracks, but also meets the overall stress and connection requirements of modular units during transportation, hoisting, and use, thereby improving the safety and applicability of this type of structural system. Summary of the Invention

[0007] This invention addresses the following technical problems existing in the ends of high-hollow-ratio UHPC core column slabs: the solid length available for anchoring the longitudinal tensile reinforcement near the support is limited, making it difficult to meet the anchorage length requirements calculated according to ordinary concrete specifications, which easily leads to bond slippage between the tensile reinforcement and the UHPC matrix; once the reinforcement ends slip, end cracks occur prematurely and extend towards the mid-span, and the bond failure between UHPC and reinforcement is relatively brittle, which is detrimental to the safety of prefabricated modules during transportation, hoisting, and service; existing end reinforcement measures mostly rely on simply extending the solid section, thickening the whole or increasing the reinforcement density, which undermines the advantages of high hollow-ratio and lightweight in the middle, and the connection structure with the module ends is often designed separately, making it difficult to balance reasonable stress and assembly construction efficiency.

[0008] The purpose of this invention is to effectively improve the anchorage reliability of tensile steel bars, suppress end slippage and crack propagation, and coordinate with the modular end beam / corner beam connection structure, while maintaining the high void ratio and lightweight of the UHPC core column plate.

[0009] To achieve the above objectives, this invention provides a core column end reinforcement and rib end strengthening structure, applicable to precast slab components cast from UHPC, with internal core columns and ribs, and a high void ratio in the middle. This structure mainly includes:

[0010] 1. Solid or semi-solid anchorage zone at the end (2): Located at one or both ends of the UHPC core column plate (1) near the support, a predetermined length L is set along the plate span direction, so that the original hollow sections of several core columns (5) and ribs (4) within this range gradually transition to solid or semi-solid sections. By filling the core column holes with UHPC or ordinary concrete (15), or only partially filling and retaining the central cavity (16), a local solid or semi-solid anchorage zone (2) is formed to improve the shear resistance and bond anchorage capacity at the end.

[0011] 2. Anchoring expansion rib area (3): The rib (4) is widened and thickened along the span direction within the end anchoring area (2) to form the anchoring expansion rib area (3), the rib width of which is... Width greater than the middle rib It can gradually increase in size near the end of the slab, forming a localized hidden beam. Preferably, L is related to the span of the slab. satisfy Increase the width to meet .

[0012] 3. Anchorage structure at the ends of the longitudinal tension reinforcement (6): The longitudinal tension reinforcement (6) is arranged along the rib (4), and a mechanical anchor head (7) and / or a closed hook (8) are provided at the ends within the anchorage expansion rib area (3) to allow stress transfer to be completed within a shorter length. Effective anchorage length of the reinforcement. Less than the anchorage length calculated according to ordinary concrete specifications And preferably satisfying This allows for full utilization of the higher bond strength between UHPC and steel reinforcement.

[0013] 4. Constraint reinforcement (9, 10): Constraint reinforcement is provided in the anchorage expansion rib area (3) to confine the ends of the tensile longitudinal reinforcement (6), inhibit the development of UHPC cracks and improve bond anchorage performance. The contraint reinforcement can be small-diameter stirrups (9), preferably with a diameter of 6 to 10 mm and a spacing of no more than 100 mm; or it can be short U-shaped bars (10) arranged in pairs, with their leg lengths surrounding the anchorage end area of ​​the reinforcement.

[0014] 5. Integrated precast end beams or corner beams (11, 12): Precast end beams (11) or precast corner beams (12) are wrapped around the outside of the anchoring expansion rib area (3) and are integrally formed with the UHPC core column plate (1) or reliably connected by connecting steel bars, embedded parts, etc. Bolt sleeves (13), connecting steel plates or connecting ribs are pre-embedded in the end beams (11) or corner beams (12) for reliable assembly with adjacent module units by high-strength bolts (14), grouting sleeves or post-cast UHPC, so as to realize the overall stress and modular installation requirements of the floor or bridge deck, while considering the stress safety during transportation and hoisting.

[0015] Through the above structural arrangement, without changing the hollowness ratio of the central core column and ribs, only the local area at the end of the plate is made solid or semi-solid and the rib ends are widened. Combined with mechanical anchor heads or closed hooks at the ends of the tension reinforcement and restraint reinforcement, a special anti-slip end anchoring scheme for the characteristics of UHPC core column plates is realized.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. Improve end anchorage reliability: By combining the design of solid or semi-solid end anchorage zone (2) with anchorage expansion rib zone (3), the bonding and anchorage capacity between UHPC and tensile steel bar (6) is significantly improved within a limited end length, effectively suppressing end slippage of tensile steel bar and end crack propagation.

[0018] 2. Maintain the advantages of high hollowness and lightweight in the middle: Only the core column (5) and rib (4) are solidified and widened in a local area at the end of the plate, while the original high hollowness section in the middle is maintained, so that the self-weight control of the component and the stiffness improvement are balanced, which is suitable for large span and long cantilever structures.

[0019] 3. Make full use of the high bonding performance of UHPC: Control the anchorage length of the tensile steel bars to be significantly smaller than the calculated value of ordinary concrete. Through the synergistic effect of mechanical anchor head (7), closed hook (8) and restraint steel bars (9, 10), the high bonding strength between UHPC and steel bars can be better utilized, and the end structure size can be reduced.

[0020] 4. Integrated design with modular assembly structure: By wrapping the precast end beam (11) or corner beam (12) outside the anchoring expansion rib area (3), and setting bolt sleeves (13), high-strength bolts (14) and other connecting parts in it, the integrated design of the end anchoring structure and the modular assembly node is realized, which is conducive to factory prefabrication, standardized production and rapid on-site assembly, while ensuring safe stress during transportation and hoisting.

[0021] 5. Simple structure and easy to promote and apply: This invention can be achieved by adjusting the local cross section and optimizing the conventional steel reinforcement structure on the basis of the existing UHPC core column plate. It does not require complex additional steel components or special construction technology, and is easy to promote and apply in prefabricated floor slabs, bridge decks and other projects. Attached Figure Description

[0022] The accompanying drawings are used to illustrate preferred embodiments of the invention and do not constitute a limitation on the scope of protection of the invention.

[0023] Figure 1 is a schematic plan view of the end reinforcement anchorage and rib end strengthening structure of the core column plate of the present invention.

[0024] Figure 2 is a schematic diagram of the longitudinal section along the rib direction, showing the solid or semi-solid anchorage zone at the end and the anchorage structure at the end of the tension reinforcement.

[0025] Figure 3 is a schematic cross-sectional view of the anchorage expansion rib area, showing the widening of the rib end and the arrangement of the restraining reinforcement.

[0026] Figure 4 is a schematic diagram showing the connection between modular units via prefabricated end beams or corner beams.

[0027] Figure 1 Explanation (Overall Plan View): As shown in Figure 1, the present invention provides a core column plate end reinforcement anchorage and rib end strengthening structure, applied to a UHPC core column plate (1). Several central ribs (4) are arranged along the plate span direction in the middle of the UHPC core column plate (1), and core columns (5) are set between and below the ribs (4) to form a high void ratio section. A solid or semi-solid end anchorage area (2) is set in the plate end area near the support, and this area has a predetermined length L along the plate span direction. In this area, several core columns (5) transition from the hollow form in the middle to the solid or semi-solid form, forming a solid area conducive to reinforcement anchorage. A precast end beam (11) is set on the outside of the solid or semi-solid end anchorage area (2) or a precast corner beam (12) is set at the corner for connection between module units.

[0028] Figure 2 illustrates (longitudinal section along the rib direction): As shown in Figure 2, a longitudinal section is taken along the direction of the middle rib (4). It can be seen that in the middle region, the middle rib (4) and the core column (5) below are high void ratio sections; while in the solid or semi-solid anchorage area (2) at the end, a semi-solid section is formed by filling with UHPC or ordinary concrete (15) or partially filling, making the core column (5) and the area below it locally solid. In the solid or semi-solid anchorage area (2) at the end, the rib (4) is widened and thickened to form the anchorage expansion rib area (3). The tensile longitudinal steel bars (6) are arranged along the rib (4), and mechanical anchor heads (7) and / or closed hooks (8) are set in the anchorage expansion rib area (3) so that the steel bars complete stress transfer within a shorter anchorage length. Small diameter stirrups (9) or short U-shaped bars (10) are arranged around the ends of the steel bars to provide circumferential restraint.

[0029] Figure 3 illustrates (transverse section at the rib end): As shown in Figure 3, a transverse section is made at the anchoring expansion rib area (3). The middle rib (4) widens to both sides near the plate end to form the anchoring expansion rib area (3). Its rib width is greater than that of the middle rib to form a local hidden beam, thereby improving the local shear and bending resistance of the end area. The tensile longitudinal reinforcement (6) is arranged at the tie position of the anchoring expansion rib area (3), and its end is provided with mechanical anchor head (7) and / or closed hook (8). Small diameter stirrups (9) or short U-shaped bars (10) are provided around the ends of the reinforcement to constrain the UHPC matrix and inhibit crack propagation. The core column (5) below the anchoring expansion rib area (3) is filled with UHPC or ordinary concrete (15). If it is a semi-solid section, a central cavity (16) is retained in the filling.

[0030] Figure 4 illustrates the module connection: As shown in Figure 4, precast end beams (11) or precast corner beams (12) are respectively installed at the ends of two adjacent UHPC core column plates (1). Bolt sleeves (13), connecting steel plates, or connecting ribs are pre-embedded inside the precast end beams (11) or precast corner beams (12). Adjacent modules are reliably connected via high-strength bolts (14), bolt sleeves (13), and / or grouting materials. The precast end beams (11) or precast corner beams (12) and their rear anchoring expansion rib area (3) are subjected to overall stress, ensuring that the anchoring force of the tensile longitudinal reinforcement (6) and the connection force of the end beams are coordinated, thereby improving the end anti-slip performance and overall stress safety while ensuring the modular assembly requirements. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that, without departing from the concept of the present invention, equivalent substitutions and modifications can be made to the structural forms, dimensional parameters, reinforcement arrangements, etc., in the following embodiments, and all such substitutions and modifications should fall within the protection scope of the present invention.

[0032] For ease of explanation, the same or similar components in the attached drawings are referred to by the same reference numerals, as follows: 1 — Integral UHPC core plate; 2 — Solid or semi-solid end anchorage zone; 3 — Anchorage flared rib zone; 4 — Middle rib; 5 — Core column; 6 — Tensile longitudinal reinforcement; 7 — Mechanical anchor head; 8 — Closed hook; 9 — Small diameter stirrup; 10 — Short U-shaped reinforcement; 11 — Precast end beam; 12 — Precast corner beam; 13 — Bolt sleeve; 14 — High-strength bolt; 15 — Filled with UHPC or ordinary concrete; 16 — Central cavity.

[0033] Example 1: Overall structure and end anti-slip construction

[0034] As shown in Figures 1 to 3, this embodiment provides a core column plate end reinforcement anchorage and rib end strengthening structure, which is applied to precast UHPC core column plates (1).

[0035] 1. Core Column Plate Overall Structure

[0036] The UHPC core column plate (1) is generally arranged in a rectangular planar shape, with its long side in the span direction and its short side in the width direction. Several parallel central ribs (4) are arranged in the middle of the plate along the span direction. Core columns (5) are arranged between the central ribs (4) and below them, which together form a high-hollow section: the central ribs (4) are arranged with constant rib height and rib width in the middle area of ​​the plate to provide the main bending stiffness; the core columns (5) are arranged in a rectangular or square shape in the plane to form a regular cavity array to reduce self-weight; the core columns (5) and ribs (4) in the middle area are connected by UHPC integral casting to form an integral working section.

[0037] Taking typical parameters as an example, the core column spacing can be 400 to 1200 mm, the rib height of the middle rib (4) can be 1.2 to 1.8 times the plate thickness, and the side length of the core column (5) cross section can be 100 to 300 mm. This embodiment is not limited to specific dimensions and can be determined according to the engineering span and load requirements.

[0038] 2. Solid or semi-solid anchorage zone at the end (2)

[0039] As shown in Figures 1 and 2, a solid or semi-solid end anchorage zone (2) is provided at one or both ends of the slab near the support. The length of the end anchorage zone (2) along the slab span is L, which is used to provide effective anchorage space for the tensile longitudinal reinforcement (6).

[0040] In the end anchorage zone (2), the core column (5), which was originally hollow, is filled into solid or semi-solid form by pouring filling material (15). The filling material (15) is preferably UHPC that is the same as or compatible with the plate, or ordinary concrete can be used according to economic considerations to ensure good bonding with the UHPC matrix. When a semi-solid form is used, a central cavity (16) is retained in the core column (5) and the filling material (15) below it to reduce the self-weight as much as possible while improving anchorage and shear resistance.

[0041] In a typical design, L is related to the corresponding slab span. satisfy: When determining specific values ​​through experiments and calculations, optimization can be achieved by comprehensively considering the bonding performance between UHPC and steel reinforcement, the stress characteristics of the component, and construction conditions.

[0042] The inner core column (5) of the end anchoring area (2) gradually transitions from a hollow section in the middle to a solid or semi-solid section. The transition can be done in a stepped or continuous manner to reduce stress concentration and facilitate mold making and casting.

[0043] 3. Anchoring expansion rib area (3)

[0044] As shown in Figures 2 and 3, in the end anchoring area (2), the middle rib (4) near the end of the plate is widened or thickened to form the anchoring expansion rib area (3).

[0045] The anchoring expansion rib area (3) is arranged along the span direction of the plate, and the rib width gradually increases near the end of the plate to form an "expansion" shape; the rib width of the anchoring expansion rib area (3) Width of the middle rib The following conditions must be met: The preferred value range can be adjusted according to the design load and component height; the rib width can adopt a linear gradual change, a segmented gradual change, or a local sudden expansion form. In this embodiment, a linear or single-step gradual change form is preferred to facilitate formwork fabrication and casting.

[0046] By forming a local hidden beam-shaped anchorage rib zone (3) in the end region, the local shear strength and bending stiffness of the end region can be significantly improved, providing a favorable anchorage environment for the tensile longitudinal reinforcement (6).

[0047] 4. Anchorage structure at the ends of the longitudinal tensile reinforcement (6)

[0048] As shown in Figures 2 and 3, the tensile longitudinal reinforcement (6) is arranged along the middle rib (4) and plays a load-bearing role as the main tie bar in the middle area. A special anchorage structure is set at its end in the end anchorage area (2).

[0049] The diameter of the longitudinal tensile reinforcement (6) can be determined according to the bending moment design, and hot-rolled ribbed steel bars in the range of 14 to 32 mm are generally used. In the anchorage expansion rib area (3), mechanical anchor heads (7) and / or closed hooks (8) are set at the ends of the longitudinal tensile reinforcement (6). The mechanical anchor head (7) can be in the form of extrusion anchor head, nut anchor head or welded end plate anchor head, etc., and it is preferred to use nut anchor head or extrusion anchor head prepared in a factory according to standardization. The bending angle of the closed hook (8) is preferably 90° to 135°, and the straight section length of the hook is not less than 6 times the diameter of the steel bar to improve the end anchorage force.

[0050] In this embodiment, the effective anchorage length of the tensile longitudinal reinforcement (6) is... Anchorage length less than that calculated by the ordinary concrete design code The ratio is determined through a specialized UHPC-reinforcement bond test, and preferably satisfies the following: By shortening the anchorage length and combining it with mechanical anchor head (7) and closed hook (8), the high bonding performance of UHPC can be fully utilized while ensuring safety reserves.

[0051] 5. Arrangement of confining reinforcement bars (9, 10)

[0052] As shown in Figures 2 and 3, in the anchorage expansion rib area (3), in order to suppress cracking of the UHPC matrix and improve the restraint effect of the steel reinforcement anchorage area, restraint reinforcement is arranged, including small diameter stirrups (9) and / or short U-shaped bars (10).

[0053] Small-diameter stirrups (9) are arranged around the tensile longitudinal steel bars (6), with a diameter generally of 6 to 10 mm and a spacing preferably not greater than 100 mm; short U-shaped bars (10) can be arranged in pairs, with the U-shaped opening facing the side or bottom of the rib (4), and their limb length surrounding the anchorage end range of the tensile longitudinal steel bars (6); stirrups (9) and short U-shaped bars (10) can be used alone or in combination. In this embodiment, bidirectional or multidirectional restraint is preferably used in the anchorage expansion rib area (3) near the end of the steel bar to enhance the local triaxial compressive stress state.

[0054] The density of the reinforcing bars can be arranged in stages along the anchorage length. For example, the density can be appropriately increased in the area near the end of the slab, while it can be appropriately relaxed in the area near the middle rib, so as to balance structural rationality and construction economy.

[0055] Example 2: Semi-solid end anchorage zone and cavity retention form

[0056] Based on Example 1, this embodiment focuses on explaining the structural form of the semi-solid end anchorage area (2) and the central cavity (16).

[0057] As shown in Figures 2 and 3, within the end anchorage zone (2), the core column (5) and the area below it adopt a semi-solid cross section:

[0058] 1. Semi-solid filling form

[0059] First, when prefabricating the UHPC core column plate (1) mold in the factory, a detachable or hole-reserving device is set at the core column position in the end anchoring area (2) to form the outline of the central cavity (16); when the UHPC is cast as a whole in this area, a central cavity (16) of a certain shape is retained in the center of the core column by inserting hollow plastic or metal sleeves, foam blocks, etc.; after the casting is completed and a certain strength is reached, the hollow sleeve is removed or the lightweight filler is retained if necessary, thereby forming a central cavity (16) surrounded by UHPC or ordinary concrete (15).

[0060] 2. Size and shape of the central cavity (16)

[0061] The central cavity (16) can be circular, square or rectangular, preferably similar to the overall cross-sectional shape of the core column (5) to facilitate template fabrication; the side length or diameter of the central cavity (16) is generally 30% to 70% of the core column cross-sectional dimensions, and can be selected according to the requirements of shear resistance, punching resistance and anchoring performance; the height of the central cavity (16) can be 50% to 100% of the height of the core column (5), or it can be set only in the area near the bottom or top of the plate to achieve reinforcement at different height positions.

[0062] By using the aforementioned semi-solid form, the local shear resistance, punching shear resistance, and anchoring performance at the ends can be effectively improved, while maintaining the lightweight characteristics of the overall component as much as possible, reducing material usage and self-weight.

[0063] Example 3: Different Reinforcing Bar End Anchorage Methods

[0064] This embodiment, based on embodiment 1, illustrates the specific application scenarios of different rebar anchorage structures.

[0065] 1. Construction using only mechanical anchor heads (7)

[0066] For situations involving high stress, limited component height, and large rebar diameter, mechanical anchor heads (7) can be preferred: nut anchor heads or extrusion anchor heads (7) are processed or installed at the ends of the tensile longitudinal rebars (6), with the outer diameter of the anchor head significantly larger than the rebar diameter; force is transmitted over a shorter length through mechanical locking; in this case, the use of closed hooks (8) can be appropriately reduced or eliminated to simplify the rebar processing technology. This form is suitable for combinations of high-strength rebars and high-strength UHPC, and is used in high-stress areas of large-span slabs and bridge decks.

[0067] 2. Construction using only closed hooks (8)

[0068] For cases with relatively small loads or large slab thickness, a traditional closed hook (8) can be preferred: the ends of the tensile longitudinal reinforcement (6) are bent into closed hooks (8), with a bending angle of 90° to 135°; the straight section length of the hook is controlled to be not less than 6d (d is the diameter of the reinforcement); and high-density small-diameter stirrups (9) and / or short U-shaped bars (10) are used to constrain the anchorage zone. This structure is easy to process and is suitable for small and medium-span floor slabs and general stress areas.

[0069] 3. Combined structure of mechanical anchor head (7) and closed hook (8)

[0070] In projects with high safety reserve requirements or high seismic resistance requirements, mechanical anchors (7) and closed hooks (8) can be installed simultaneously at the ends of the longitudinal tensile reinforcement (6): first, mechanical anchors (7) are installed at the ends of the reinforcement, and then closed hooks (8) are installed near the anchors; or some reinforcements are reinforced with mechanical anchors (7) and other reinforcements are reinforced with closed hooks (8) to form a combined reinforcement system; combined with higher density confined reinforcement (9, 10), stronger ductility and anti-slip capacity can be obtained. This combination can be used for key components or nodes, such as the end of the floor slab supporting the mid-span beam, shear concentration areas, etc.

[0071] Example 4: Modular connection with precast end beams / corner beams

[0072] As shown in Figure 4, this embodiment illustrates the collaborative work of the end anchoring structure of the present invention with the modular prefabricated end beam (11) and the prefabricated corner beam (12).

[0073] 1. Construction of precast end beam (11)

[0074] Precast end beams (11) are set at the ends of the long side plate: the precast end beams (11) are arranged along the width of the plate, and their cross-sectional height is generally slightly greater than or equal to the overall thickness of the UHPC core column plate (1) to ensure good rigidity and connection space; the precast end beams (11) and the anchoring expansion rib area (3) are connected by through longitudinal steel bars (6) and stirrups (9), or additional connecting steel bars can be welded or tied; multiple bolt sleeves (13) or connecting steel plates are pre-embedded inside the precast end beams (11) for connection with the end beams of adjacent module units by high-strength bolts (14).

[0075] During the factory prefabrication stage, the end beam (11) and the UHPC core column plate (1) are cast as an integral component; or the core column plate (1) is prefabricated first, and then the end beam (11) and the core column plate (1) are reliably connected by wet joint or grouting.

[0076] 2. Construction of precast corner beam (12)

[0077] At the corner of the component, a precast corner beam (12) can be set: the precast corner beam (12) extends in two mutually perpendicular directions at the same time, and can connect the ends of two or more core column plates (1) together; bolt sleeves (13), high-strength bolts (14) or connecting steel plates are also set inside the precast corner beam (12) as connection nodes between corner modules; the tensile longitudinal steel bars (6) extend from the anchoring expansion rib area (3) into the interior of the precast corner beam (12) and share the force with the internal reinforcement of the corner beam.

[0078] 3. Modular assembly and stress coordination

[0079] At the construction site, the end beams (11) or corner beams (12) of two or more adjacent precast UHPC core column slabs (1) are connected in the following ways: the bolt sleeves (13) in the adjacent end beams (11) or corner beams (12) are aligned, high-strength bolts (14) are inserted, and nuts are tightened to form a rigid or semi-rigid connection; or high-strength bolts (14) are inserted into the reserved connection steel plate holes, and then combined with local grouting or post-cast UHPC to form an integral node; after the connection between the end beams (11) or corner beams (12) is completed, the anchoring expansion rib area (3) and the end solid or semi-solid anchoring area (2) of the present invention are combined to make the tensile longitudinal steel bars (6) reliably anchored in the end area, avoiding steel bar slippage and crack concentration caused by uneven stiffness in the connection area. Through the above modular assembly method, the overall stress performance of the component can be achieved in the use stage while ensuring safety in the transportation, hoisting and installation stages.

[0080] Example 5: Key Points of Construction and Manufacturing Methods (Optional)

[0081] To facilitate the application of this invention in engineering, a typical manufacturing and construction process is briefly described:

[0082] 1. Factory prefabrication stage

[0083] According to the design requirements, the overall steel mold of the UHPC core column plate (1) is made, and the template structure of the middle rib (4), core column (5), end anchorage area (2) and anchorage expansion rib area (3) is reserved. Hollow sleeves or foam blocks are installed at the core column position in the end anchorage area (2) to form the central cavity (16). According to the requirements of Examples 1 to 3, the tensile longitudinal steel bars (6), mechanical anchor heads (7), closed hooks (8) and restraint steel bars (9, 10) are tied and connected and fixed with the steel bars in the precast end beam (11) or precast corner beam (12). UHPC or ordinary concrete (15) is poured, vibrated and compacted and cured to the specified age. The mold is removed and the pre-shipment inspection of the component is completed.

[0084] 2. Transportation and hoisting stage

[0085] Lifting points are arranged near the center of gravity of the component so that the force path near the lifting points can be transferred to the anchorage expansion rib area (3) and the end anchorage area (2) through the precast end beam (11) or the precast corner beam (12); the end anti-slip structure of the present invention can effectively suppress the slippage of steel bars and the generation of end cracks caused by repeated loads and impact loads during hoisting and transportation.

[0086] 3. On-site assembly stage

[0087] Position multiple UHPC core column panels (1), adjust the position between precast end beams (11) or precast corner beams (12) to align bolt sleeves (13) or connecting steel plates; insert high-strength bolts (14) and tighten them, or carry out grouting sleeve and post-cast UHPC construction; if necessary, set up a waterproof layer or protective structure at the joint of the panels to complete the floor or bridge deck system.

[0088] Through the above embodiments, the present invention achieves an integrated design of reliable anchorage of end tension reinforcement and modular connection structure while ensuring high central void ratio and lightweight, effectively improving the safety and durability of UHPC core plate during transportation, hoisting and long-term service.

Claims

1. A core column end reinforcement anchorage and rib end strengthening structure, applied to precast slab components cast from ultra-high performance concrete (UHPC), with internal core columns and ribs and a high void ratio in the middle, characterized in that, include: The end solid or semi-solid anchorage zone is located within a predetermined length range near the support at the end of the plate. Within this range, several core columns and ribs gradually transition from hollow sections to solid or semi-solid sections. The anchorage expansion rib zone is located within the end anchorage zone and is set along the plate span direction. The rib height and plate thickness gradually increase near the end of the plate, forming a local hidden beam, making the rib width at this point greater than the rib width in the middle. The tensile longitudinal reinforcement is arranged along the ribs, and mechanical anchor heads and / or closed hooks are set at the ends within the anchorage expansion rib zone. Its effective anchorage length is less than the anchorage length calculated according to the ordinary concrete design code. The restraint reinforcement is used to bind the tensile longitudinal reinforcement within the anchorage expansion rib zone. It is a small-diameter stirrup or a short U-shaped bar. The precast end beam or corner beam covers the outside of the anchorage expansion rib zone and is integrally formed with the UHPC core column plate or reliably connected through connecting reinforcement, sleeves, embedded parts, etc., for bolt or sleeve anchorage connection between modular units.

2. The construction according to claim 1, characterized in that, The length L of the solid or semi-solid anchorage zone at the end along the span direction satisfies the following condition: 。 3. The construction according to claim 1 or 2, characterized in that, The widening width b of the anchoring expansion rib area e The width b0 of the middle rib satisfies: Furthermore, the rib width is either continuous or gradually varied in stages.

4. The construction according to any of the preceding claims, characterized in that, The effective anchorage length l of the tensile longitudinal reinforcement a The anchorage length l is calculated according to the design specifications for ordinary concrete. n The ratio satisfies: The ratio was determined through tests on the bond performance between UHPC and steel reinforcement.

5. The construction according to any of the preceding claims, characterized in that, The mechanical anchor head is one of the following: extrusion anchor head, nut anchor head, or welded end plate anchor head. The bending angle of the closed hook is 90° to 135°, and the straight section length of the hook is not less than 6 times the diameter of the reinforcing bar.

6. The construction according to any of the preceding claims, characterized in that, The restraining reinforcement is a small-diameter stirrup with a diameter of 6 to 10 mm. The spacing between the stirrups in the anchorage expansion rib area is no more than 100 mm, or it is a pair of short U-shaped bars with their limbs surrounding the anchorage end of the tensioned longitudinal reinforcement.

7. The construction according to any of the preceding claims, characterized in that, The core column holes in the solid or semi-solid anchorage zone at the end are filled with UHPC or ordinary concrete to make them solid, or a semi-solid section is formed by partially filling and retaining the central cavity, so as to improve the local shear resistance and bond anchorage capacity.

8. The construction according to any of the preceding claims, characterized in that, The prefabricated end beams or corner beams are pre-embedded with connecting steel plates, bolt sleeves, or connecting ribs to achieve overall connection with the end beams or corner beams of adjacent module units through high-strength bolts, grouting sleeves, or post-cast UHPC, taking into account the stress requirements under transportation and hoisting conditions.

Images