A prestressed anchor bolt joint that can counteract adverse downward forces and its construction method

Abstract

This invention relates to a prestressed anchor joint that can counteract adverse downward forces and its construction method. The prestressed anchor joint includes a prestressed anchor bolt anchored in the foundation slab and the foundation soil. The foundation slab has an inverted frustum-shaped through hole, within which an additional enlarged head is embedded. An anchor bolt support concrete slab is also embedded in the foundation soil. The additional enlarged head and the anchor bolt support concrete slab are fixedly connected to the prestressed anchor bolt. Compared with the prior art, in this invention, the prestressing force of the prestressed anchor bolt is borne by the anchor bolt support concrete slab, not the foundation slab: the anchor bolt support concrete slab is poured before the foundation slab, and the compression of the foundation soil layer by the prestressing force of the prestressed anchor bolt is completed before the foundation slab, thus further ensuring that the prestressing force of the prestressed anchor bolt is not transmitted to the foundation slab. Therefore, the foundation soil under the foundation slab is not subjected to the dual pressure of the upper load and the prestressed anchor bolt, ensuring the bearing capacity of the foundation.

Description

Technical Field

[0001] This invention relates to a prestressed anchor joint, and more particularly to a prestressed anchor joint that can counteract adverse downward forces and its construction method. Background Technology

[0002] When the groundwater level is high, the basement floor height is high, or the soil cover thickness of the basement roof is thin, the upper ballast may be insufficient to resist the large buoyancy force. In this case, the entire basement section may be at risk of floating up, indicating insufficient buoyancy resistance. This problem can be addressed using anti-uplift piles or prestressed anchors.

[0003] For tension piles, the cost is high and the construction period is long. In addition, tension piles not only resist uplift but also have considerable compressive bearing capacity. However, the vertical load of a pure underground garage is relatively small. When the soil layer reaches a certain bearing capacity, a natural foundation can be used, which results in low material utilization efficiency.

[0004] Prestressed anchors can only resist the buoyancy of water in the basement, but cannot bear vertical pressure, and their construction speed is relatively fast. However, prestressed anchors need to be pre-tensioned and then anchored to the basement foundation slab. The basement slab will be subjected to a reverse prestressing force from the prestressed anchors. This prestressing force, combined with the slab surface load, could potentially cause insufficient bearing capacity of the foundation soil under the raft slab or waterproofing slab. However, structural designers do not consider the impact of this prestressing force on the foundation soil during the design process. Summary of the Invention

[0005] The purpose of this invention is to provide a prestressed anchor bolt node that can offset adverse downward forces and its construction method, without applying additional vertical loads to the base plate without affecting the provision of vertical forces to resist buoyancy.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A prestressed anchor node includes a prestressed anchor anchored in a foundation slab and foundation soil, wherein the foundation slab has an inverted frustum-shaped through hole, and an additional enlarged head is embedded in the inverted frustum-shaped through hole; an anchor support concrete slab is also embedded in the foundation soil; the additional enlarged head and the anchor support concrete slab are respectively fixedly connected to the prestressed anchor anchor.

[0008] Furthermore, the anchor-supported concrete slab is disc-shaped, thicker in the middle and thinner at the outer edge.

[0009] Furthermore, the distance between the anchor-supported concrete slab and the foundation slab is 500–2000 mm.

[0010] Furthermore, a ribbed anchor is embedded in the concrete slab supporting the anchor bolt, and the ribbed anchor is fixedly connected to the prestressed anchor bolt.

[0011] Furthermore, the prestressed anchor node also includes an end back plate disposed on the additional enlarged head, and the prestressed anchor passes through the additional enlarged head and is connected to the end back plate.

[0012] Furthermore, the space between the additional enlarged head and the frustum-shaped through hole is filled with waterproof sealant.

[0013] Furthermore, there is a gap of 50-100mm between the additional enlarged head and the frustum-shaped through hole, and the gap is filled with waterproof filler.

[0014] A construction method for a prestressed anchor joint includes the following steps:

[0015] S1: Excavate the foundation pit according to the design elevation of the foundation slab and anchor-supported concrete slab;

[0016] S2: Erect brick formwork inside the foundation pit;

[0017] S3: Drive anchor bolts into the foundation pit;

[0018] S4: Tie the reinforcing steel bars of the concrete slab supporting the anchor around the anchor and insert the ribbed anchor.

[0019] S5: Tension the anchor rod to obtain a prestressed anchor rod;

[0020] S6: Pour concrete, and after the concrete has cured, remove the brick formwork to obtain the anchor-supported concrete slab;

[0021] S7: Backfill soil to the bottom elevation of the raft foundation;

[0022] S8: Tie the bottom plate reinforcement and pour the bottom plate concrete to obtain a foundation plate with an inverted frustum-shaped through hole, and make the top of the prestressed anchor rod pass through the inverted frustum-shaped through hole;

[0023] S9: The additional enlarged head is plugged and welded to the prestressed anchor rod to obtain the prestressed anchor rod node.

[0024] Furthermore, step S5 also includes perforated plug welding of the prestressed anchor rod and the ribbed anchor.

[0025] Furthermore, step S9 also includes: after the additional enlarged head and the prestressed anchor rod are perforated and plugged together, the end back plate is laid on the additional enlarged head and perforated and plugged together with the prestressed anchor rod.

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

[0027] 1) In this invention, the prestressing force of the prestressed anchor is borne by the concrete slab supported by the anchor, not by the foundation slab: the concrete slab supported by the anchor is poured before the foundation slab, and the compression of the foundation soil by the prestressing force of the prestressed anchor is completed before the foundation slab, thus further ensuring that the prestressing force of the prestressed anchor is not transmitted to the foundation slab. Therefore, the foundation soil under the foundation slab is not subjected to the dual pressure of the upper load and the prestressed anchor, ensuring the bearing capacity of the foundation.

[0028] 2) In this invention, when the base plate is subjected to buoyancy and tends to float upward, a normal stress will be formed between the notched base plate and the additional enlarged head, preventing the base plate from deforming upward.

[0029] 3) In this invention, the anchor-supported concrete slab is subjected to the point-like downward tension of the prestressed anchor and the surface-like support force of the foundation soil. Furthermore, the anchor-supported concrete slab is not absolutely rigid and undergoes some deformation. Therefore, the support force from the foundation soil is greater at the center and smaller at both ends, making its stress similar to that of a cantilever beam. A design with a larger thickness at the center and smaller thickness at the ends is adopted to save on concrete usage.

[0030] 4) In this invention, to prevent the prestressed anchor rod from being pulled out of the concrete slab supported by the anchor rod, it is necessary to solve the shear bond problem between the two. Therefore, the ribbed anchor and the prestressed anchor rod are first subjected to through-hole plug welding to ensure that they form a whole. The ribbed anchor and the concrete can provide a huge interlocking force to prevent the prestressed anchor rod from being pulled out of the concrete.

[0031] 5) When the base plate deforms upward in this invention, it will generate huge normal stress on the additional enlarged head. In order to prevent the prestressed anchor rod from being pulled out of the additional enlarged head, the additional enlarged head and the prestressed anchor rod are perforated and plugged to ensure that they form a whole.

[0032] 6) In order to increase the structural safety redundancy and further ensure that the prestressed anchor rods can effectively provide downward force without failing when the bottom plate floats, an end back plate is set on the bottom plate surface again. The end back plate is also formed with the prestressed anchor rod by through-hole plug welding to ensure that it forms a whole. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a prestressed anchor bolt node that can offset adverse downward tension in the embodiment.

[0034] Figure 2 This is a schematic diagram of the anchor bolt structure;

[0035] Figure 3 , Figures 16-17 , Figure 19 A schematic diagram of a concrete slab supported by anchor bolts;

[0036] Figure 4A top view of the ribbed anchor.

[0037] Figure 5 This is a schematic diagram of the main structure of the ribbed anchor.

[0038] Figure 6 This is a schematic diagram of step S2 in a construction method for a prestressed anchor bolt joint that can offset adverse downward tension.

[0039] Figure 7 This is a schematic diagram of step S3 in a construction method for a prestressed anchor bolt joint that can offset adverse downward tension.

[0040] Figure 8 This is a schematic diagram of step S4 in a construction method for a prestressed anchor bolt joint that can offset adverse downward tension.

[0041] Figure 9 This is a schematic diagram of step S5 in a construction method for a prestressed anchor bolt joint that can offset adverse downward tension.

[0042] Figure 10 This is a schematic diagram of step S6 in a construction method for a prestressed anchor bolt joint that can offset adverse downward forces.

[0043] Figure 11 This is a schematic diagram of step S7 in a construction method for a prestressed anchor bolt joint that can offset adverse downward tension.

[0044] Figure 12 This is a schematic diagram of step S8 in a construction method for a prestressed anchor bolt joint that can offset adverse downward tension.

[0045] Figure 13 This is a schematic diagram of step S9 in a construction method for a prestressed anchor bolt joint that can offset adverse downward tension.

[0046] Figures 14-15 This is a schematic diagram of step S10 in a construction method for a prestressed anchor bolt joint that can offset adverse downward forces.

[0047] Figure 18 This is a schematic diagram of the assembly structure of the ribbed anchor and the concrete slab supported by the anchor (the ribbed anchor is located inside the concrete slab supported by the anchor).

[0048] Figure 20 This is a front (axial) sectional view with the enlarged head attached;

[0049] Figure 21 A bottom view with an attached enlarged head;

[0050] Explanation of markings in the diagram:

[0051] 1-Foundation slab, 2-Foundation soil, 3-Prestressed anchor, 4-Additional enlarged head, 5-Anchor support concrete slab, A-End thickness, B-Root thickness, 6-Ribped anchor, 601-Stiffening plate, 602-Clamping plate, 7-End back plate, 8-Reinforcement, 9-Brick formwork, 10-Anchor, 11-Ribped anchor perforation plug weld point, 12-Additional enlarged head perforation plug weld point, D-Anchor bar diameter, L-Length. Detailed Implementation

[0052] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are based on the above-described technical solutions of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0053] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0054] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0055] Example:

[0056] like Figure 1 The prestressed anchor node shown is capable of offsetting adverse downward forces. It includes a prestressed anchor 3 anchored in the foundation slab 1 and the foundation soil 2. The foundation slab 1 is provided with an inverted frustum-shaped through hole, and an additional enlarged head 4 is embedded in the inverted frustum-shaped through hole. An anchor support concrete slab 5 is also embedded in the foundation soil 2. The additional enlarged head 4 and the anchor support concrete slab 5 are respectively fixedly connected to the prestressed anchor 3.

[0057] In some specific embodiments, the foundation slab 1 includes a raft slab or a waterproof slab.

[0058] In some specific embodiments, the anchor-supported concrete slab 5 is disc-shaped, thicker in the middle and thinner at the outer edges. The anchor-supported concrete slab 5 is subjected to the point-like downward tension of the prestressed anchor rods 3 and the surface-like support force of the foundation soil 2. Furthermore, the anchor-supported concrete slab 5 is not absolutely rigid and undergoes some deformation. Therefore, the foundation soil 2 it experiences is also thicker at the center and thinner at the ends, making its stress similar to that of a cantilever beam. The use of a thicker core and thinner ends saves on concrete usage.

[0059] In some specific embodiments, the shape and size of the additional enlarged head 4 are adapted to the inverted frustum-shaped through hole, and it is made of steel with a hole along the center line. Its size is adapted to the prestressed anchor rod. When the foundation plate 1 is subjected to water buoyancy and tends to float and deform, normal stress will be formed between the foundation plate 1 with the inverted frustum-shaped through hole and the additional enlarged head 4, preventing the deformation of the foundation plate 1.

[0060] In some specific embodiments, the distance between the anchor-supported concrete slab 5 and the foundation slab 1 is 500-2000 mm.

[0061] In some specific embodiments, ribbed anchors 6 are embedded within the anchor-supported concrete slab 5, and the ribbed anchors 6 are fixedly connected to the prestressed anchors 3. Specifically, such as... Figures 4-5 As shown, the ribbed anchor 6 consists of a stiffening plate 601 and upper and lower clamping plates 602 with holes. Preferably, the holes are circular, and their size is adapted to the prestressed anchor rod.

[0062] To prevent the prestressed anchor rod 3 from being pulled out of the concrete slab 5 supported by the anchor rod, it is necessary to solve the shear bond problem between the two. Therefore, the ribbed anchor rod 6 and the prestressed anchor rod 3 are first subjected to through-hole plug welding to ensure that they form a whole. The ribbed anchor rod 6 can provide a huge interlocking force with the concrete to prevent the prestressed anchor rod 3 from being pulled out of the concrete.

[0063] In some specific embodiments, to increase structural safety redundancy and further ensure that the prestressed anchor rods 3 can effectively provide downward force without failing when the foundation slab 1 floats, an end back plate 7 is installed on the surface of the foundation slab 1. This end back plate 7 is also formed with the prestressed anchor rods 3 using through-hole plug welding to ensure it forms a single unit. Specifically, the end back plate 7 is made of steel with holes, and its size is adapted to the prestressed anchor rods.

[0064] In some specific embodiments, the space between the additional enlarged head 4 and the frustum-shaped through hole is filled with waterproof filler. Preferably, there is a gap of 50-100 mm between the additional enlarged head 4 and the frustum-shaped through hole, and the gap is filled with waterproof filler.

[0065] A design method for prestressed anchor bolt nodes that can offset adverse downward tension includes the following steps:

[0066] A1: Based on geological data, architectural design drawings, and other information, design the required parameters for the anchor bolts, such as diameter D and length L. Figure 2 As shown;

[0067] A2: Calculate the prestressing force of prestressed anchor 3 based on parameters such as diameter D and length L of the anchor rod;

[0068] A3: The area and dimensions of the anchor-supported concrete slab 5 are calculated based on the prestressing force of the prestressed anchor 3 and the bearing capacity of the foundation. Since all the vertical prestressing force of the prestressed anchor 3 is borne by the anchor-supported concrete slab 5 and then transferred to the foundation soil 2 under the anchor-supported concrete slab 5, the stress on the anchor-supported concrete slab 5 is close to that of a cantilever beam. The required end thickness A, root thickness B, and required reinforcement 8 of the anchor-supported concrete slab 5 are calculated using the calculation method for variable cross-section cantilever beams. Figure 3 As shown;

[0069] A4: Due to the large vertical force of the prestressed anchor rod 3 and the weak bond between the prestressed anchor rod 3 and the concrete slab 5 supporting the anchor rod, the prestressed anchor rod 3 is pulled out to avoid splitting failure between the prestressed anchor rod 3 and the concrete slab 5 supporting the anchor rod. The prestressed anchor rod 3 and the ribbed anchor 6 are then welded together to form a whole, enhancing the bonding ability and shear resistance between the two. The ribbed anchor 6 serves as a shear connector, and its dimensions are calculated based on the prestressed force of the prestressed anchor rod 3, the shear strength of the concrete, and the reinforcing steel bars in the concrete slab 5 supporting the anchor rod.

[0070] A5: The additional enlarged head 4 is made of steel and is welded to the prestressed anchor rod 3 to form a whole. The weld size and the material strength of the additional enlarged head 4 are calculated from the pretension of the prestressed anchor rod 3 to ensure that the prestressed anchor rod 3 is not pulled out and the additional enlarged head 4 itself is not damaged.

[0071] A6: To increase structural safety redundancy, the end back plate 7 is also integrally welded with the prestressed anchor rod 3 through a perforation weld, serving as a second line of defense against buoyancy for the prestressed anchor rod 3. Similarly, the weld size, the size of the end back plate 7, and the material strength are calculated from the prestressed tension of the prestressed anchor rod 3, ensuring that the prestressed anchor rod 3 is not pulled out and that the end back plate 7 itself does not undergo significant deformation or damage.

[0072] A construction method for prestressed anchor joints that can offset adverse downward tension includes the following steps:

[0073] S1: Prefabricate the ribbed anchor 6 in the factory according to the structural design drawings and transport it to the site;

[0074] S2: As Figure 6 As shown, the foundation pit is excavated according to the design elevation of the foundation slab 1 and the anchor-supported concrete slab 5;

[0075] S3: As Figure 7 As shown, a brick formwork 9 is erected inside the foundation pit;

[0076] S4: As Figure 8 As shown, anchor rods 10 are driven into the foundation pit according to the structural design drawings;

[0077] S5: As Figure 9As shown, the reinforcing steel bars of the concrete slab supporting the anchor rod are tied around the anchor rod, and the ribbed anchor 6 is inserted.

[0078] S6: Tension the anchor rod 10 to obtain the prestressed anchor rod 3; perform through-hole plug welding on the prestressed anchor rod 3 and the ribbed anchor 6, with the through-hole plug welding point 11 of the ribbed anchor as shown. Figure 10 As shown;

[0079] S7: As Figure 11 As shown, concrete is poured, and after the concrete has cured, the brick formwork 9 is removed to obtain the anchor-supported concrete slab 5.

[0080] S8: As Figure 12 As shown, the backfill soil is placed to the bottom elevation of the raft foundation;

[0081] S9: such as Figure 13 As shown, the bottom plate reinforcement is tied and the bottom plate concrete is poured to obtain the foundation plate 1 with an inverted frustum-shaped through hole, and the top of the prestressed anchor rod 3 passes through the inverted frustum-shaped through hole.

[0082] S10: Perform a through-hole plug weld on the additional enlarged head 4 and the prestressed anchor rod 3, with the through-hole plug weld point 12 of the additional enlarged head as shown. Figure 14 As shown; then the end back plate 7 is laid on the additional enlarged head 4, and is perforated and plugged with the prestressed anchor rod 3, as shown. Figure 15 As shown, the prestressed anchor bolt node is obtained.

[0083] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A prestressed anchor node comprising a prestressed anchor (3) anchored in a foundation slab (1) and ground soil (2), characterized in that, The base plate (1) is provided with an inverted round table-shaped through hole, and an additional enlarged head (4) is embedded in the inverted round table-shaped through hole; an anchor rod supporting concrete plate (5) is also embedded in the foundation soil (2); the additional enlarged head (4) and the anchor rod supporting concrete plate (5) are fixedly connected with the prestressed anchor rod (3) respectively; The anchor rod supporting concrete plate (5) is in the shape of a disc with a thick middle and a thin edge; The spacing between the anchor rod supporting concrete plate (5) and the base plate (1) is 500-2000 mm; The anchor rod supporting concrete plate (5) is embedded with a ribbed anchoring piece (6), and the ribbed anchoring piece (6) is fixedly connected with the prestressed anchor rod (3).

2. A pre-stressed rock bolt node according to claim 1, characterised in that, An end back plate (7) provided on the additional enlarged head (4) is also included, and the prestressed anchor rod (3) is connected with the end back plate (7) by penetrating the additional enlarged head (4).

3. A pre-stressed rock bolt node according to claim 1, characterised in that, The additional enlarged head (4) and the inverted round table-shaped through hole are filled with waterproof filler.

4. A pre-stressed rock bolt node according to claim 3, characterised in that, The additional enlarged head (4) and the inverted round table-shaped through hole have a gap of 50-100 mm, and the gap is filled with waterproof filler.

5. A method of constructing a prestressed rock bolt node as claimed in any one of claims 1 to 4, characterized in that, The method comprises the following steps: S1: Excavate the foundation pit according to the design elevation of the base plate (1) and the anchor rod supporting concrete plate (5); S2: Set up a brick formwork (9) in the foundation pit; S3: Drive the anchor rod into the foundation pit; S4: Bind the anchor rod supporting concrete plate steel bars around the anchor rod, and place the ribbed anchoring piece (6); S5: Stretch and tension the anchor rod to obtain the prestressed anchor rod (3); S6: Pour the concrete, and after the concrete is cured, remove the brick formwork to obtain the anchor rod supporting concrete plate (5); S7: Backfill the soil to the bottom elevation of the raft foundation; S8: Bind the bottom plate steel bars and pour the bottom plate concrete to obtain the base plate (1) with the inverted round table-shaped through hole, and make the top end of the prestressed anchor rod (3) penetrate through the inverted round table-shaped through hole; S9: Perform perforation plug welding on the additional enlarged head (4) and the prestressed anchor rod (3) to obtain the prestressed anchor rod joint.

6. The construction method of a prestressed anchor rod node according to claim 5, characterized in that, Step S5 further comprises performing perforation plug welding on the prestressed anchor rod (3) and the ribbed anchoring piece (6).

7. The construction method of a prestressed anchor rod node according to claim 5, characterized in that, Step S9 further comprises: after perforation plug welding is performed on the additional enlarged head (4) and the prestressed anchor rod (3), laying the end back plate (7) on the additional enlarged head (4) and performing perforation plug welding on the prestressed anchor rod (3).

Images