A partial bearing capacity optimization structure of an anti-pulling anchor rod

Abstract

This invention provides an optimized structure for the local bearing capacity of pull-out anchors, belonging to the field of building construction technology. It includes an anchor reinforcement body comprising an upper section above ground and a lower section below ground, which are integrally formed. The top of the upper section includes an anchoring steel plate. A tapered spiral stirrup connects the lower surface of the anchoring steel plate to the ground, and the tapered spiral stirrup is fixedly connected to the lower surface of the anchoring steel plate. The tapered spiral stirrup is a truncated cone shape, wider at the top and narrower at the bottom, and is composed of a single continuously spiraling reinforcing bar. A set of vertically arranged reinforcing bars are evenly distributed around the circumference of the tapered spiral stirrup. This invention replaces traditional ordinary cylindrical stirrups with tapered spiral stirrups and welded vertical reinforcing bars, aiming to actively and efficiently improve the bearing capacity and durability of the concrete in the anchoring zone.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and specifically to a structure for optimizing the local bearing capacity of pull-out anchors. Background Technology

[0002] In recent years, to better address land scarcity, the application of underground space has become increasingly widespread, leading to the development of large underground structures in areas with shallow groundwater levels. Due to their large floor area, deep foundations, and relatively few stories, these underground structures often lack the structural weight to withstand the buoyancy of groundwater at historically high groundwater levels. Therefore, anti-uplift anchors are necessary to counteract this buoyancy.

[0003] Pull-out anchors are a type of geotechnical anchoring technology specifically designed to resist upward pull-out forces on structures or components. They are typically made of high-strength steel (such as reinforcing bars or steel strands), with one end anchored deep in stable ground and the other end firmly connected to the structure requiring pull-out resistance (such as foundation slabs, retaining walls, columns, etc.). The core function of pull-out anchors is to provide strong pull-out bearing capacity, preventing structures or foundations from being pulled up or damaged by upward forces. Typically, pull-out anchors need to have their ends anchored to the basement floor slab to transfer the tensile force. Specifically, before pouring the basement floor slab, the metal embedded part at the end of the anchor is placed in the pouring area, and the slab is poured together after the reinforcing steel is tied, thus achieving a rigid connection between the anchor and the floor slab. However, under enormous tensile forces, simply embedding rectangular steel plates can lead to localized compressive failure of the concrete.

[0004] Chinese patent CN222100835U provides a system for improving the coordinated force-bearing capacity of pull-out anchors and pull-out piles, as shown in the attached specification. Figure 1 As shown, using only spring-shaped stirrups at the anchor bolt connection to improve local bearing capacity is ineffective. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to address the shortcomings of existing technologies by providing a structure for optimizing the local bearing capacity of pull-out anchors. This structure replaces traditional cylindrical stirrups with tapered spiral stirrups and welded vertical reinforcing bars, aiming to proactively and efficiently improve the bearing capacity and durability of the concrete in the anchorage zone.

[0006] Technical Solution: The present invention discloses a structure for optimizing the local bearing capacity of an anti-pull-out anchor, comprising an anchor bar body, which includes an upper bar portion located above the ground and a lower bar portion located below the ground. The upper bar portion and the lower bar portion are integral. The top of the upper bar portion includes an anchoring steel plate. A tapered spiral stirrup is connected between the lower surface of the anchoring steel plate and the ground. The tapered spiral stirrup is fixedly connected to the lower surface of the anchoring steel plate. The tapered spiral stirrup is a frustum-shaped cone, larger at the top and smaller at the bottom, and is composed of a single continuously spiraling reinforcing bar. A set of vertically arranged vertical reinforcing bars are evenly distributed around the circumference of the tapered spiral stirrup 2.

[0007] When the vertical reinforcing bars are pulled downwards, attempting to pull the "large end" of the tapered spiral stirrups downwards towards the "small end," this downward movement inevitably forces the stirrups to contract inwards due to the larger diameter at the top and smaller diameter at the bottom. This generates strong, active, and continuous radial compressive stress on the internal concrete. This puts the core concrete in the anchorage zone under triaxial compression (vertical compression from the anchoring steel plates, radial compression from the active constraint of the tapered stirrups, which is generated immediately in the initial stage of the anchor bolt under tensile loading, rather than passively waiting for the concrete to deform and crack).

[0008] Furthermore, the diameter of the reinforcing bar is 14mm, the diameter of the top hoop of the tapered spiral stirrup is 240mm, the diameter of the bottom hoop of the tapered spiral stirrup is 140mm, the vertical length of the tapered spiral stirrup ranges from 220mm to 390mm, and the corresponding cone angle range is 15° to 25°.

[0009] Furthermore, the top of the vertical reinforcing bar is connected to the anchoring steel plate, and the vertical reinforcing bar and the tapered spiral stirrup are welded and fixed at the contact points. The structure in which the top of the vertical reinforcing bar is connected to the anchoring steel plate and welded to the tapered spiral stirrup at all contact points is the core technical guarantee for realizing the active restraint mechanism: during the initial loading, the rigidity of the weld seam causes the vertical bar and the tapered stirrup to deform synchronously, immediately triggering the restraint; during the peak load, the welded joint inhibits the local buckling of the vertical bar and maintains the stability of the taper; during the failure stage, the plastic deformation of the weld seam consumes energy and delays the disintegration of the structure.

[0010] Furthermore, there are 8 vertical reinforcing bars 3, and the included angle between any two adjacent vertical reinforcing bars 3 ranges from 30° to 60°. The 8 vertical reinforcing bars and the spiral stirrups form a spatial truss structure, which significantly improves the torsional stiffness of the anchorage zone.

[0011] Furthermore, the middle of the anchoring steel plate facing downwards is threaded with an upper nut, and the upper rod is threaded with a lower nut at the position on the ground; this stage is the initial sealing, and the upper nut is both a mechanical force transmission component (enhancing the interface pressure bearing) and a waterproof carrier (fixing the water-stop strip).

[0012] Furthermore, the lower end of the upper nut is provided with an upper water-swellable sealing strip, and the upper end of the lower nut is provided with a lower water-swellable sealing strip. The material is modified polyurethane. This stage is an active water-sealable seal, providing a tight seal.

[0013] Furthermore, the anchoring steel plate 1 is a rectangle with dimensions of 250×250mm and is made of 40cr steel.

[0014] Furthermore, the vertical reinforcing bar 3 is made of plain round steel bar with a diameter of 12mm.

[0015] Beneficial effects: Compared with the prior art, the advantages of the present invention are as follows:

[0016] The tapered spiral stirrups designed in this invention are rigidly connected to the reinforcing bars by full welding. When the anchor rod is under tension, the active constraint mechanism is triggered. The vertical bars pull down the large end of the tapered stirrups, forcing radial contraction and generating continuous confining pressure. This puts the core concrete in a triaxial compression state, thereby improving both the local compressive strength and the ultimate pull-out resistance. Attached Figure Description

[0017] Figure 1 This refers to the prior art mentioned in the background section;

[0018] Figure 2 This is a schematic diagram of the structure of the present invention;

[0019] Figure 3 This is a schematic diagram of the structure of a tapered spiral stirrup;

[0020] Figure 4 yes Figure 3 Top view;

[0021] Figure 5 This is a force transmission path analysis diagram of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the embodiments described.

[0023] like Figure 2 The diagram illustrates a structure for optimizing the local bearing capacity of a pull-out anchor bolt, comprising an anchor bolt reinforcement 4. The anchor bolt reinforcement 4 includes an upper section above the ground and a lower section below the ground, forming a single unit. The top of the upper section includes an anchoring steel plate 1, with an upper nut 5 threadedly connected to the downward-facing center of the anchoring steel plate 1. A lower nut is threadedly connected to the upper section at its ground-level position. An upper water-swellable sealing strip 6 is installed at the lower end of the upper nut 5, and a lower water-swellable sealing strip 7 is installed at the upper end of the lower nut. A tapered spiral stirrup 2 connects the lower surface of the anchoring steel plate 1 to the ground. Figures 3-4 As shown, the tapered spiral stirrup 2 is fixedly connected to the lower surface of the anchoring steel plate 1. The tapered spiral stirrup 2 is a frustum-shaped cone, wider at the top and narrower at the bottom, and is composed of a single continuously spiraling reinforcing bar. A group of vertically arranged reinforcing bars 3 are evenly distributed around the circumference of the tapered spiral stirrup 2. The top of the vertical reinforcing bars 3 is connected to the anchoring steel plate 1. The vertical reinforcing bars 3 and the tapered spiral stirrup are welded and fixed at their contact points. There are eight vertical reinforcing bars 3, and the angle between any two adjacent vertical reinforcing bars 3 ranges from 30° to 60°. Figure 5As shown, the concrete in the anchorage area is under triaxial stress, which greatly improves the compressive bearing capacity of the local concrete and prevents it from being crushed and causing the anchor rod to fail. In contrast, traditional ordinary stirrups are cylindrical and do not have an active clamping effect. The clamping effect of the stirrups is only triggered when the concrete deforms under vertical load. At this time, some cracks have already appeared inside the concrete, and its mechanical properties and waterproof performance are greatly weakened.

[0024] In this embodiment, the diameter of the reinforcing bar is 14mm, the diameter of the top hoop of the tapered spiral stirrup 2 is 240mm, the diameter of the bottom hoop of the tapered spiral stirrup 2 is 140mm, and the vertical length of the tapered spiral stirrup 2 is 300mm. The anchoring steel plate 1 is a rectangle with dimensions of 250×250mm and is made of 40Cr steel; the vertical reinforcing bar 3 is a plain round steel bar with a diameter of 12mm.

[0025] The construction method in this embodiment is as follows:

[0026] 1. GPS positioning and marking

[0027] The anchor bolt center point is calibrated using RTK-GPS (horizontal accuracy ±5mm, elevation accuracy ±10mm); a warning line is sprayed with a diameter of 300mm around the center point (to prevent mechanical collision).

[0028] 2. High-pressure jet spraying for hole formation

[0029] The high-pressure jet grouting machine drills to the designed depth, enlarges the hole, and pulls out the drill bit.

[0030] 3. Anchor bolt installation and grouting

[0031] Insert anchor bolts and perform pressure grouting and curing.

[0032] 4. Install the lower water-swellable sealing strip.

[0033] Install adhesive strips on the upper surface of the concrete base layer, i.e., around the anchor holes. Joint treatment: 45° beveled overlap, overlap length ≥ 50mm, and seal with special adhesive.

[0034] 5. Install tapered spiral stirrups and place the upper water-swellable sealing strip;

[0035] 6. Install the anchor plates and tighten the high-strength nuts, and wait for the base slab concrete to be poured.

[0036] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A structure for optimizing the local bearing capacity of an anti-pull-out anchor, characterized in that: The anchor rod (4) includes an upper rod part located on the ground and a lower rod part located below the ground. The upper rod part and the lower rod part are a whole. The top of the upper rod part includes an anchoring steel plate (1). A tapered spiral stirrup (2) is connected between the lower surface of the anchoring steel plate (1) and the ground. The tapered spiral stirrup (2) is fixedly connected to the lower surface of the anchoring steel plate (1). The tapered spiral stirrup (2) is a frustum-shaped cone with a larger upper part and a smaller lower part. It is composed of a continuously spiraling steel bar. A set of vertically arranged vertical reinforcing bars (3) are evenly distributed around the tapered spiral stirrup (2).

2. The structure for optimizing the local bearing capacity of an anti-pull-out anchor bolt according to claim 1, characterized in that: The diameter of the reinforcing bar is 14mm, the diameter of the top hoop of the tapered spiral stirrup (2) is 240mm, the diameter of the bottom hoop of the tapered spiral stirrup (2) is 140mm, and the vertical length of the tapered spiral stirrup (2) ranges from 220mm to 390mm.

3. The structure for optimizing the local bearing capacity of an anti-pull-out anchor bolt according to claim 1, characterized in that: The top of the vertical reinforcing bar (3) is connected to the anchoring steel plate (1), and the vertical reinforcing bar (3) and the conical spiral stirrup are welded and fixed at the contact point.

4. The structure for optimizing the local bearing capacity of an anti-pull-out anchor bolt according to claim 3, characterized in that: There are 8 vertical reinforcing bars (3), and the included angle between any two adjacent vertical reinforcing bars (3) is 30°~60°.

5. The structure for optimizing the local bearing capacity of an anti-pull-out anchor bolt according to claim 1, characterized in that: The anchoring steel plate (1) is threaded with an upper nut (5) at the center facing downwards; the upper rod is threaded with a lower nut at the position on the ground.

6. The structure for optimizing the local bearing capacity of an anti-pull-out anchor bolt according to claim 5, characterized in that: The lower end of the upper nut (5) is provided with an upper water-swellable sealing strip (6); the upper end of the lower nut is provided with a lower water-swellable sealing strip (7).

7. The structure for optimizing the local bearing capacity of an anti-pull-out anchor bolt according to claim 1, characterized in that: The anchoring steel plate (1) is a rectangle with dimensions of 250×250mm and is made of 40cr steel.

8. The structure for optimizing the local bearing capacity of an anti-pull-out anchor bolt according to claim 3, characterized in that: The vertical reinforcing bar (3) is made of plain round steel bar with a diameter of 12mm.

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