Replaceable material fabricated foundation and calculation method thereof

Abstract

The invention belongs to the technical field of structural engineering, and particularly relates to a material-replaceable fabricated foundation and a calculation method thereof.The material-replaceable fabricated foundation comprises a bottom plate, stand columns, connecting pieces, caps and bolts; the bottom plate is formed by splicing I-shaped steel, the stand column is composed of angle steel, the connecting piece is angle steel, one end of the connecting piece is connected with the bottom plate through a bolt, the other end of the connecting piece is connected with the stand column through a bolt, the cap is angle steel arranged at the top of the stand column, and the cap is connected with the stand column through a bolt. And the cap is connected with the power transmission tower. All-metal component bolt connection is adopted for the foundation, traditional concrete wet operation and field welding are not needed, the components can be directly purchased or only individual components need to be machined in a factory, the construction period is remarkably shortened, the timeliness requirement for emergency repair of the medium and low voltage power transmission tower is particularly met, and assembling can be rapidly completed and put into use.

Description

Technical Field

[0001] The present invention belongs to the technical field of structural engineering, and in particular relates to a replaceable material assembled foundation and a calculation method thereof. Background Art

[0002] Transmission lines, as the core carrier of the power system, undertake the critical task of long-distance transmission and distribution of electrical energy. Their safety and reliability directly impact the stable operation of the power grid. Traditional transmission lines primarily consist of conductors, insulators, hardware, towers, and foundations. Tower foundations, as the core supporting structure, play a crucial role in transferring tower loads to the foundation. Transmission lines can be categorized by their installation method: overhead lines and cable lines. Overhead lines are widely used for long-distance transmission due to their low construction costs and ease of maintenance. However, they are exposed to the elements and susceptible to wind loads, icing, earthquakes, and geological activity. Cable lines are primarily used in urban power grids or in specialized environments, but they are expensive and can be challenging to locate faults. Common foundation types for overhead lines include traditional cast-in-place concrete, precast concrete, steel-concrete composites, and new types of foundations for special geological conditions. However, these commonly suffer from low construction efficiency, significant resource waste, and heavy environmental impact. Traditional wet foundation work, especially during emergency repairs, requires significant time and cannot meet timelines.

[0003] Prefabricated foundations are a type of transmission line foundation constructed from standardized factory-fabricated components and quickly assembled on-site. Compared to traditional cast-in-place foundations, their core advantages lie in construction efficiency, quality control, environmental friendliness, and adaptability. However, current research on prefabricated foundations for transmission lines primarily focuses on reinforced concrete composite foundations. Research on all-metal prefabricated foundations, commonly used for emergency rescue and low-voltage lines, is lacking. Furthermore, there is a lack of critical experimental research on the stress behavior of the diagonal and main materials, force transmission paths, and material selection methods for these prefabricated foundations. Summary of the Invention

[0004] In response to the technical problems existing in the above-mentioned existing prefabricated foundations, the present invention provides a prefabricated foundation with replaceable materials and a calculation method thereof.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A replaceable assembled foundation includes a base plate, a column, a connector, a cap and bolts; the base plate is spliced ​​by I-beams, the column is composed of angle steel, the connector is an angle steel, one end of the connector is connected to the base plate by bolts, and the other end of the connector is connected to the column by bolts, the cap is an angle steel arranged on the top of the column, the cap is connected to the column by bolts, and the cap is connected to the transmission tower.

[0006] The I-beams of the bottom plate are spliced ​​into a cross-shaped or well-shaped structure by bolts, and the splicing positions of adjacent I-beams are fixed by bolts.

[0007] The angle steel of the column is an equilateral angle steel.

[0008] The material of the I-beam and angle steel is Q235 steel, and the material of the cap is the same as that of the angle steel of the column.

[0009] The structural shape of the cap is adapted to the bottom interface of the transmission tower, and the cap is detachably connected to the top of the column by bolts.

[0010] The bolts are high-strength bolts, and the base plate, columns, connectors and caps are all detachably connected by the high-strength bolts.

[0011] There are multiple connecting pieces, which are evenly distributed along the height direction of the column. One end of each connecting piece is connected to the I-beam flange of the base plate by bolts, and the other end is connected to the angle steel flange of the column by bolts.

[0012] A calculation method for a replaceable prefabricated foundation comprises the following steps: S1. Determine the target downward pressure load N; S2. Using equal-leg angle steel b×b×t, with a thickness of t=16mm, calculate the cross-sectional area of ​​the angle steel A=2bt−t 2 =2×b×16−16 2 =32b−256; S3. Calculate the minimum turning radius i of the angle steel section min ≈0.3b+0.8; S4. Calculate the slenderness ratio λ = L / i min =2000 / (0.3b+0.8); S5. Modify the stability coefficient φ through reverse fitting and substitute it into the empirical adjustment formula N = (0.36 + 120 / b) × (32b − 256) × 0.215 to calculate the required angle steel side length b.

[0013] The target downward pressure load in S1 is N=φAf, where φ is the stability coefficient and slenderness ratio λ=L / i min Related, L is the length of the angle steel 2000mm; A is the cross-sectional area of ​​the angle steel, for equal-leg angle steel A=2bt−t 2 , where b is the side length of the angle steel, t is the thickness of the angle steel; f is the design value of the steel compressive strength; i min is the minimum turning radius of the angle steel section, through the approximate formula i min ≈0.3b+0.05t calculation.

[0014] The ultimate bearing capacity of different angle steel sizes is verified through real-type tests. The verification data includes: When b = 400, the ultimate bearing capacity is 800.4kN; When b = 350, the ultimate bearing capacity is 670.5kN; When b=300, the ultimate bearing capacity is 535.9kN.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The foundation of the present invention uses all-metal components connected by bolts, eliminating the need for traditional wet concrete work and on-site welding. Components can be purchased directly or only individual parts (the cap parts connected to the transmission tower) need to be processed in the factory, significantly shortening the construction period. In particular, it meets the timeliness requirements of emergency repairs for medium and low voltage transmission towers and can be quickly assembled and put into use.

[0016] 2. Key components, such as columns, are constructed using commercially available steel sections, making material procurement convenient and cost-effective. Calculation methods based on steel structure design specifications precisely match the steel section dimensions to the estimated foundation bearing capacity, minimizing material waste while ensuring structural safety and achieving a balance between cost-effectiveness and safety. Full-scale testing has demonstrated minimal error between calculated and tested values, ensuring design reliability.

[0017] 3. The cap component connected to the transmission tower of the present invention can be replaced according to the interface requirements of transmission towers of different voltage levels, thereby improving the versatility of the foundation; the base plate adopts an I-beam splicing structure, and the splicing form (cross shape or well shape) can be flexibly adjusted to adapt to different geological conditions and load distribution, thereby expanding the application scenarios.

[0018] 4. The all-metal components of the present invention can be 100% recycled and reused, reducing construction waste and environmental burden; there is no dust or sewage discharge during the construction process, which meets the requirements of green construction and is particularly suitable for the construction of power transmission lines in ecologically sensitive areas.

[0019] 5. The connectors of the present invention use angle steel to connect the base plate and the column, and multiple connectors are evenly distributed along the height direction of the column. A rigid connection is formed by high-strength bolts, which enhances the overall wind and earthquake resistance of the foundation and avoids the weak connection problem that may exist in traditional prefabricated foundations. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0021] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein and to facilitate understanding and reading by persons skilled in the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, without affecting the efficacy and objectives of the present invention, shall remain within the scope of the technical contents disclosed herein.

[0022] Figure 1 It is a structural schematic diagram of the present invention.

[0023] Among them: 1 is the base plate, 2 is the column, 3 is the connecting piece, 4 is the cap, and 5 is the bolt. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of this application, not all the embodiments. These descriptions are only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0025] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following embodiments are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0026] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0027] Example 1 This embodiment provides a replaceable material assembly foundation, such as Figure 1As shown, components are prefabricated and materials are prepared. Commercially available Q235 I-beams are cut to the design dimensions and pre-assembled into a baseplate frame using high-strength bolts using a cross-shaped or crisscross pattern. Bolt holes are reserved. Q235 equal-leg angle steel is selected as column 2. The angle steel's side length is calculated and the bolt holes are machined at the ends. Angle steel made of the same material as column 2 is cut to the appropriate length as connector 3, and bolt holes are machined at both ends to ensure uniform distribution along the height of column 2. A cap 4 made of the same material as column 2 is machined according to the dimensions of the transmission tower's base interface and appropriate bolt holes are drilled. 8.8-grade high-strength bolts 5 and matching gaskets are then prepared. Next, on-site foundation preparation is performed. Debris in the construction area is cleared and the foundation is compacted or a gravel cushion layer is laid. After ensuring the foundation installation surface is level, the outline of the baseplate 1 and the installation positions of column 2 are marked on the foundation. Then carry out the foundation assembly, lift the prefabricated I-beam bottom plate 1 frame to the foundation positioning area, fix the joints with bolts 5 and adjust the level, place the equilateral angle steel columns 2 vertically at the four corner mark positions of the bottom plate 1, connect them with the I-beam flange bolts 5 of the bottom plate 1 through the bottom connector 3 and preliminarily fix the verticality of the column 2, install multiple connectors 3 along the height direction of the column 2 according to the designed spacing, connect one end of each connector 3 with the I-beam flange bolt 5 of the bottom plate 1 and the other end with the angle steel flange bolt 5 of the column 2 and tighten the bolts 5 diagonally, align the hat 4 parts with the top bolts of the column 2 The holes are detachably connected via high-strength bolts 5. After checking the compatibility of the cap 4 and the transmission tower interface, use a torque wrench to re-tighten all bolts 5 in the tightening order of the high-strength bolts 5 to ensure that the preload force meets the design requirements. Check the overall verticality of the foundation, the flatness of the base plate 1, and the reliability of the connection. After confirming that there is no looseness, complete the final connection with the bottom flange of the transmission tower. The entire process does not require welding or concrete pouring. 2-3 people can collaborate to complete the assembly within 2 hours. All bolt 5 connections use double nuts to prevent loosening or spring washers. When the transmission tower model changes, only the cap 4 components need to be removed and replaced with the appropriate model.

[0028] Example 2 This embodiment provides a calculation method for a replaceable prefabricated foundation, comprising the following steps: The calculation formula for the ultimate bearing capacity of axially compressed angle steel is: N = φAf Where: φ is the stability factor (related to the slenderness ratio λ); A is the cross-sectional area of ​​the angle steel (mm²). For equal-leg angle steel, A=2bt−t 2 ; f is the design value of steel compressive strength (such as 215 MPa for Q235 steel); λ is the slenderness ratio, λ=L / i min ; L is the calculated length of the component (here the actual length is 2000mm); i min is the minimum turning radius of the angle steel section (mm).

[0029] For equal-leg angle steel b×b×t (thickness t=16mm): A=2bt−t 2 =2×b×16−16 2 =32b−256(mm 2 ) The minimum radius of gyration of a single angle steel around its weak axis can be estimated by the approximate formula: i min ≈0.3b+0.05t (applicable to equal-leg angle steel) Substituting t=16mm: i min ≈0.3b+0.8(mm) λ = L / i min =2000 / (0.3b+0.8) Based on the above, we can get the bearing capacity expression based on the standard formula with the side length b as the variable: N = φ × (32b − 256) × 215 × 10 −3 (kN) By correcting the value of the stability coefficient φ through reverse fitting, the empirical adjustment formula is obtained: N=(0.36+120 / b)×(32b−256)×0.215(kN) Table 1 Angle steel size and ultimate bearing capacity verification data Angle steel size (mm) Test value (kN) Calculated value based on empirical adjustment formula (kN) error(%) 300×300×16 535.9 536.1 0.04% 350×350×16 670.5 670.2 0.04% 400×400×16 800.4 800.6 0.02% As shown in Table 1, this is the verification data table of angle steel size and ultimate bearing capacity, including angle steel size (mm), test value (kN), calculated value (kN) by empirical adjustment formula, and error (%). The specific data are as follows: the test value of 300×300×16 angle steel is 535.9kN, the calculated value is 536.1kN, and the error is 0.04%; the test value of 350×350×16 angle steel is 670.5kN, the calculated value is 670.2kN, and the error is 0.04%; the test value of 400×400×16 angle steel is 800.4kN, the calculated value is 800.6kN, and the error is 0.02%. The test values ​​in this data are derived from full-scale test results. Finite element analysis was used to verify the ultimate bearing capacity of equal-leg angle steels of different sizes (all 16 mm thick and 2000 mm long). The calculated values ​​are based on the empirical adjustment formula N=(0.36+120 / b)×(32b−256)×0.215 (b is the angle steel side length, in mm), derived in the briefing document. Comparing the test values ​​with the calculated values ​​aims to verify the accuracy of the empirical adjustment formula and ensure the reliability of the column angle steel size selection method. The results show a maximum error of 0.04% and a minimum error of 0.02%, both of which are extremely small. This indicates that the empirical adjustment formula is highly consistent with the full-scale test results. This formula can be used to quickly calculate the required angle steel size based on the target downward compressive load, achieving economic optimization while ensuring safety, thus meeting the invention's goal of controlling steel size and improving economic efficiency.

[0030] The above only describes in detail the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of the present invention, and various changes should be included in the scope of protection of the present invention.

Claims

1. A replaceable material assembled foundation, characterized by: The invention comprises a base plate (1), a column (2), a connecting piece (3), a cap (4) and a bolt (5); the base plate (1) is formed by splicing I-beams, the column (2) is composed of angle steel, the connecting piece (3) is an angle steel, one end of the connecting piece (3) is connected to the base plate (1) by a bolt (5), the other end of the connecting piece (3) is connected to the column (2) by a bolt (5), the cap (4) is an angle steel arranged on the top of the column (2), the cap (4) is connected to the column (2) by a bolt (5), and the cap (4) is connected to the transmission tower.

2. The replaceable material prefabricated foundation according to claim 1, characterized in that: The I-beams of the base plate (1) are spliced ​​into a cross-shaped or well-shaped structure by bolts (5), and the spliced ​​portions of adjacent I-beams are fixed by bolts (5).

3. The replaceable material prefabricated foundation according to claim 1, characterized in that: The angle steel of the column (2) is an equilateral angle steel.

4. The replaceable material prefabricated foundation according to claim 1, characterized in that: The material of the I-beam and the angle steel is Q235 steel, and the material of the cap (4) is the same as that of the angle steel of the column (2).

5. The replaceable material prefabricated foundation according to claim 1, characterized in that: The structural shape of the cap (4) is adapted to the bottom interface of the transmission tower, and the cap (4) is detachably connected to the top of the column (2) via bolts (5).

6. The replaceable material prefabricated foundation according to claim 1, characterized in that: The bolts (5) are high-strength bolts, and the base plate (1), the columns (2), the connecting piece (3) and the cap (4) are all detachably connected via the high-strength bolts (5).

7. The replaceable material prefabricated foundation according to claim 1, characterized in that: The number of the connecting members (3) is multiple and evenly distributed along the height direction of the column (2). One end of each connecting member (3) is connected to the I-beam flange of the base plate (1) through a bolt (5), and the other end is connected to the angle steel flange of the column (2) through a bolt (5).

8. A calculation method for a replaceable material prefabricated foundation, the calculation method being applicable to a replaceable material prefabricated foundation according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Determine the target downward pressure load N; S2. Using equal-leg angle steel b×b×t, with a thickness of t=16mm, calculate the cross-sectional area of ​​the angle steel A=2bt−t 2 =2×b×16−16 2 =32b−256; S3. Calculate the minimum turning radius i of the angle steel section min ≈0.3b+0.8; S4. Calculate the slenderness ratio λ = L / i min =2000 / (0.3b+0.8); S5. Correct the stability coefficient φ through reverse fitting and substitute it into the empirical adjustment formula N = (0.36 + 120 / b) × (32b − 256) × 0.215 to calculate the required angle steel side length b.

9. The calculation method of a replaceable prefabricated foundation according to claim 8, characterized in that: The target downward pressure load in S1 is N=φAf, where φ is the stability coefficient and slenderness ratio λ=L / i min Related, L is the length of the angle steel 2000mm; A is the cross-sectional area of ​​the angle steel, for equal-leg angle steel A=2bt−t 2 , where b is the side length of the angle steel, t is the thickness of the angle steel; f is the design value of the steel compressive strength; i min is the minimum turning radius of the angle steel section, through the approximate formula i min ≈0.3b+0.05t calculation.

10. The calculation method of a replaceable prefabricated foundation according to claim 8, characterized in that: The ultimate bearing capacity of different angle steel sizes is verified through real-type tests. The verification data includes: When b = 400, the ultimate bearing capacity is 800.4kN; When b = 350, the ultimate bearing capacity is 670.5kN; When b=300, the ultimate bearing capacity is 535.9kN.

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