Cross diagonal member structure of tower body of power transmission tower

Abstract

The invention relates to the technical field of power transmission lines, in particular to a crossed diagonal member structure of a power transmission tower body. Comprising two opposite tower body main materials, the two tower body main materials are connected through a crossed diagonal member, the tower body main materials and the crossed diagonal member are connected through a triangular supporting structure, the crossed diagonal member comprises two unequal angle steels which are arranged in a crossed mode, and a first connecting hole is formed in the center of a short limb of each unequal angle steel; the first bolt sequentially penetrates through the first connecting holes in the two pieces of unequal angle steel and is locked through the first nut, the short limbs of the two pieces of unequal angle steel abut against each other, the equal angle steel is arranged at the two ends of each piece of unequal angle steel, and the two limbs of each equal angle steel are connected with the two limb bolts of the unequal angle steel respectively. And the limb width of the equilateral angle steel is the same as that of the short limb of the unequilateral angle steel. According to the invention, the weight of the tower body is reduced under the condition that the strength is ensured by adopting the cross-arranged unequal angle steel structure and combining the specific proportion of the long limbs to the short limbs and the equal angle steel connected with the end parts.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission lines, and specifically to a cross diagonal member structure for the tower body of a transmission tower. Background Art

[0002] To avoid a substantial increase in project investment caused by house demolition, transmission line projects often need to cross through mountains and ranges. With the large-scale construction of transmission line projects in recent years, it has become increasingly difficult to select the tower erection locations for newly built transmission line projects. Many towers have to be erected on steep terrains with slopes exceeding 40°, or even exactly on steep and narrow mountain ridges. When the tower height is relatively small, the opening size of the tower legs is generally small, and it can barely be erected on steep and narrow terrains. However, when the tower needs to cross obstacles and its height exceeds 80 meters, the opening size of the tower legs needs to be strictly controlled to enable tower erection on steep and narrow terrains. A high-flexibility transmission tower refers to a tower with a height exceeding 80 meters, the opening size of the tower legs being smaller than the specification requirements, and the ratio of the static linear calculated top displacement to the tower height being greater than 1 / 100.

[0003] For the design of transmission line towers, the load calculation combination complies with the "Code for Design of 110kV - 750kV Overhead Transmission Lines" (GB 50545 - 2010) and the "Load Code for Overhead Transmission Lines" (DL / T 5551 - 2018), and the calculation of angle steel members complies with the "Standard for Design of Steel Structures" (GB 50017 - 2017) and the "Technical Specification for the Design of Tower Structures of Overhead Transmission Lines" (DL / T 5486 - 2020). Due to the relatively small stiffness of the "high-flexibility" tower, the tower displacement is relatively large under the condition of strong wind load, and the situation of premature failure of the cross diagonal members of the longer tower body occurred in the 1:1 full-scale tower test. The large deformation of the tower causes the cross diagonal members of some longer tower bodies with very small forces to have a significantly increased force and be in a state of simultaneous compression, resulting in overall out-of-plane instability of the cross diagonal members within the entire length. For the cross diagonal members of the tower, when in overall out-of-plane instability, the calculated length is the full length of the diagonal member, while when in overall in-plane instability, due to the support of the auxiliary members, the calculated length is only about half of the full length. From the results of the full-scale test, when the longer cross diagonal members of the tower undergo overall out-of-plane instability under strong wind conditions, the actual pressure borne by the cross diagonal members increases significantly compared with the theoretical calculated value, and is not much different from the pressure under the control condition when the cross diagonal members undergo overall in-plane instability. The cross diagonal members of the transmission line tower body generally use equal-angle steel, and the moment of inertia in-plane and out-of-plane are equal. To ensure that the longer cross diagonal members of the tower body do not undergo overall out-of-plane instability under large tower deformation, it is necessary to significantly increase the specification and weight of the cross diagonal members. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a cross diagonal member structure for the tower body of a transmission tower, which is used to optimize the layout structure of the cross diagonal members, increase the material utilization rate, and reduce the weight of the tower body.

[0005] The technical solution adopted by the present invention to solve its technical problems is a cross diagonal member structure of a transmission tower body, including two opposite main tower members. The two main tower members are connected by cross diagonal members. The main tower member and the cross diagonal member are connected by a triangular support structure. The cross diagonal member includes two unequal angle steels arranged crosswise. A first connection hole is provided at the center of the short limb of the unequal angle steel. A first bolt sequentially passes through the first connection holes on the two unequal angle steels and is locked with a first nut. The short limbs of the two unequal angle steels abut against each other. The ratio of the width of the long limb to the width of the short limb of the unequal angle steel is 1.6:1. Equal angle steels are provided at both ends of each unequal angle steel. One limb of the equal angle steel is bolted to the inner side surface of the long limb of the unequal angle steel, and the other limb is bolted to the inner side surface of the short limb of the unequal angle steel. The limb width of the equal angle steel is the same as the limb width of the short limb of the unequal angle steel.

[0006] Further, the cross-sectional calculation formula of the unequal angle steel is as follows:

[0007]

[0008] In the formula: N is the maximum pressure of the main tower member connected to the cross diagonal member;

[0009] K1 is the variable cross-section correction coefficient;

[0010] K2 is the proportional coefficient of the pressure of the cross diagonal member to the pressure of the main tower member under large deformation, taking 0.018;

[0011] A is the cross-sectional area of the unequal angle steel;

[0012] is the stability coefficient of the overall out-of-plane instability of the unequal angle steel;

[0013] f is the design strength of the steel of the cross diagonal member of the tower body;

[0014] The calculation formula of the variable cross-section correction coefficient K1 is as follows:

[0015]

[0016] In the formula: I1 is the out-of-plane moment of inertia of the equal angle steel;

[0017] I2 is the out-of-plane moment of inertia of the unequal angle steel.

[0018] Further, the length of each equal angle steel is half of the length of the unequal angle steel;

[0019] Further, a row of second threaded holes is provided at both ends of the long limb and the short limb of each unequal-leg angle steel. The number of threaded holes in each row is three. A third threaded hole that cooperates with the second threaded hole is provided on each equal-leg angle steel. The second bolt sequentially passes through the second threaded hole and the third threaded hole and is locked with a second nut.

[0020] The beneficial effects of the present invention are as follows: By adopting the structure of cross-arranged unequal-leg angle steels, combined with the specific ratio (1.6:1) of the long limb to the short limb and the equal-leg angle steel connected at the end, the width of the long limb of the unequal-leg angle steel is relatively large, and its out-of-plane moment of inertia is significantly higher than that of the equal-leg angle steel, thus effectively reducing the risk of overall out-of-plane instability under strong wind loads. At the same time, the introduction of the variable cross-section correction coefficient (K1) further optimizes the cross-section design to ensure the maximization of material utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of the present invention;

[0022] Figure 2 is a cross-sectional view of the cooperation between the equal-leg angle steel and the unequal-leg angle steel;

[0023] Figure 3 is a cross-sectional view of the unequal-leg angle steel;

[0024] Figure 4 is a cross-sectional view of the equal-leg angle steel.

[0025] Reference numerals: 1 - unequal-leg angle steel; 2 - first bolt; 3 - equal-leg angle steel; 4 - second bolt; 5 - main tower material; 6 - cross diagonal member; 7 - triangular support structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0027] As Figure 1As shown in the figure, the cross - diagonal member 6 structure of the transmission tower body of the present invention includes two opposite main tower members 5. The two main tower members 5 are connected by the cross - diagonal member 6. A triangular support structure 7 is used to connect the main tower member 5 and the cross - diagonal member 6. The cross - diagonal member 6 includes two unequal - leg angles 1 arranged cross - wise. A first connection hole is provided at the center of the short leg of the unequal - leg angle 1. The first bolt 2 passes through the first connection holes on the two unequal - leg angles 1 in sequence and is locked with the first nut. The short legs of the two unequal - leg angles 1 are abutted against each other. The ratio of the long - leg width to the short - leg width of the unequal - leg angle 1 is 1.6:1. Equal - leg angles 3 are provided at both ends of each unequal - leg angle 1. One limb of the equal - leg angle 3 is bolt - connected to the inner side of the long leg of the unequal - leg angle 1, and the other limb is bolt - connected to the inner side of the short leg of the unequal - leg angle 1. The limb width of the equal - leg angle 3 is the same as the short - leg limb width of the unequal - leg angle 1.

[0028] Among them, the main tower member 5 is made of angle steel. The cross - diagonal member 6 includes two connection points on the left and two connection points on the right. The two connection points on the left of the cross - diagonal member 6 are connected to one main tower member 5 by bolts, and the two connection points on the right of the cross - diagonal member 6 are connected to the other main tower member 5 by bolts. The triangular support structure 7 is composed of three angle steels: the first angle steel: an equal - leg angle 3 connecting the main tower member 5 and the upper end of the cross - diagonal member 6; the second angle steel: an equal - leg angle 3 connecting the main tower member 5 and the lower end of the cross - diagonal member 6; the third angle steel: longitudinally connecting the equal - leg angles 3 at the upper and lower ends to form a closed triangle. The cross - diagonal member 6 is composed of two unequal - leg angles 3 arranged cross - wise. The two unequal - leg angles 1 are aligned at the cross - point through the first connection holes at the center of the short legs, and are penetrated and fixed by the first bolt 2. Specifically, the short legs of the two unequal - leg angles 1 are closely abutted at the cross - point to form a rigid node. By adjusting the pre - tightening force of the first bolt 2, it is ensured that there is no relative sliding of the cross - diagonal member 6 when stressed, thereby improving the overall stability. The ratio of the long - leg width to the short - leg width of the unequal - leg angle 1 is 1.6:1. For example, if the short - leg width is 100 mm, then the long - leg width is 160 mm. This ratio design makes the out - of - plane moment of inertia of the long leg significantly higher than that of the equal - leg angle 3, thereby effectively suppressing the risk of overall out - of - plane instability under strong wind loads. Both ends of each unequal - leg angle 1 are bolt - connected to the equal - leg angle 3. Specifically, one limb of the equal - leg angle 3 is bolt - connected to the inner side of the long leg of the unequal - leg angle 1, and the other limb is bolt - connected to the inner side of the short leg. The limb width of the equal - leg angle 3 is the same as the short - leg limb width of the unequal - leg angle 1, ensuring uniform force at the connection and avoiding stress concentration.

[0029] Furthermore, the cross - sectional calculation formula of the unequal - leg angle 1 is as follows:

[0030]

[0031] Where: N is the maximum pressure of the tower main material 5 connected to the cross diagonal material 6;

[0032] K1 is the variable section correction coefficient;

[0033] K2 is the proportional coefficient between the pressure of the cross diagonal material 6 and the pressure of the tower main material 5 under large deformation, which is 0.018;

[0034] A is the cross-sectional area of the unequal angle steel 1;

[0035] is the stability coefficient of overall instability outside the unequal angle steel 1 surface;

[0036] f is the steel design strength of the tower cross diagonal member 6;

[0037] The calculation formula of variable section correction coefficient K1 is as follows:

[0038]

[0039] Where: I1 is the out-of-plane moment of inertia of the equilateral angle steel 3;

[0040] I2 is the out-of-plane moment of inertia of the unequal angle steel 1.

[0041] N is the maximum pressure of the tower body main material 5, which needs to be determined by finite element analysis or standard calculation according to actual working conditions; It needs to be determined by looking up the table in the "Steel Structure Design Standard" (GB 50017-2017), which is related to the slenderness ratio and material properties of the unequal-leg angle steel 1; A and f are the cross-sectional area of the angle steel and the design strength of the steel, respectively, and need to be determined in combination with the material selection.

[0042] The design process is as follows

[0043] 1. Calculate the maximum pressure N of the tower main material 5 according to the tower height and load combination;

[0044] 2. Preliminary selection of equilateral angle steel 3 specifications, calculation of its out-of-plane moment of inertia I1;

[0045] 3. Determine the size of unequal angle steel 1 according to the ratio of long limb to short limb (1.6:1) and calculate I2;

[0046] 4. Substitute the formula to calculate K1 and optimize the cross-sectional parameters to ensure

[0047] 5. If the verification fails, adjust the size or material grade of the unequal angle steel 1 until it meets the requirements.

[0048] Furthermore, the length of each equal - angle steel 3 is half of the length of the unequal - angle steel 1; the length of each equal - angle steel 3 is half of the length of the unequal - angle steel 1. For example, if the length of the unequal - angle steel 1 is 4 meters, then the equal - angle steels 3 connected at both ends are each 2 meters. This design can balance the stiffness and weight of the connection area, avoiding local stiffness redundancy caused by too long equal - angle steels 3 or insufficient connection strength caused by too short ones.

[0049] Select a section of the tower body of this project for calculation and comparison. The maximum pressure on the main tower members connected to the cross - braces is 2645 kN, and the length of the cross - braces is 11571 mm. When the cross - braces are made of equal - angle steels, K1 = 1. According to the specification calculation, the cross - braces need to be of the specification HL140X10 (angle steel width 140 mm, thickness 10 mm), and the weight of the cross - braces is 248.6 kg. When the cross - braces use equal - angle steels at both ends and unequal - angle steels in the middle, according to the above formula calculation, the equal - angle steels at both ends use HL100X10 (angle steel width 100 mm, thickness 10 mm), and the unequal - angle steel in the middle uses HL160X100X10 (long - side width 160 mm, short - side width 100 mm, thickness 10 mm) to meet the design requirements, and the weight of the cross - braces is 202.4 kg. Therefore, when using this scheme to meet the design strength, compared with using all equal - angle steels for the cross - braces, the way of combining equal - angle steels and unequal - angle steels in the present invention can reduce the tower weight by 18%.

[0050] To improve the stability of the connection between the equal - angle steel 3 and the unequal - angle steel 1, further, a row of second threaded holes is provided at both ends of the long limb and the short limb of each unequal - angle steel 1, and the number of threaded holes in each row is three. A third threaded hole matching the second threaded hole is provided on each equal - angle steel 3. The second bolt 4 passes through the second threaded hole and the third threaded hole in sequence and is locked with a second nut.

[0051] The embodiments of this specific implementation manner are all preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A cross diagonal member structure of a transmission tower tower body, comprising two opposite main tower body members (5), the two main tower body members (5) being connected by cross diagonal members (6), and the main tower body members (5) and the cross diagonal members (6) being connected by a triangular support structure (7), characterized in that: The cross diagonal member (6) includes two unequal-leg angles (1) arranged crosswise. A first connection hole is provided at the center of the short leg of the unequal-leg angle (1). A first bolt (2) sequentially passes through the first connection holes on the two unequal-leg angles (1) and is locked with a first nut. The short legs of the two unequal-leg angles (1) abut against each other. The ratio of the width of the long leg to the width of the short leg of the unequal-leg angle (1) is 1.6:

1. Equal-leg angles (3) are provided at both ends of each unequal-leg angle (1). One limb of the equal-leg angle (3) is bolted to the inner side of the long leg of the unequal-leg angle (1), and the other limb is bolted to the inner side of the short leg of the unequal-leg angle (1). The limb width of the equal-leg angle (3) is the same as the limb width of the short leg of the unequal-leg angle (1).

2. The cross diagonal member structure of the transmission tower body according to claim 1, wherein: The cross-sectional calculation formula of the unequal-leg angle (1) is as follows: In the formula: N is the maximum pressure of the main tower member (5) connected to the cross diagonal member (6) of the tower; K1 is the variable cross-section correction coefficient; K2 is the proportional coefficient of the pressure of the cross diagonal member (6) to the pressure of the main tower member (5) under large deformation, taking 0.018; A is the cross-sectional area of the unequal-leg angle (1); is the stability coefficient for the overall out-of-plane buckling of the unequal-angle steel (1); f is the design strength of the steel of the cross diagonal member (6) of the tower; The calculation formula of the variable cross-section correction coefficient K1 is as follows: In the formula: I1 is the out-of-plane moment of inertia of the equal-leg angle (3); I2 is the out-of-plane moment of inertia of the unequal-leg angle (1).

3. The cross diagonal member structure of the transmission tower body according to claim 1, characterized in that: The length of each equal-leg angle (3) is half of the length of the unequal-leg angle (1); 4. The cross diagonal member structure of the transmission tower body according to claim 1, characterized in that: A row of second threaded holes is provided at both ends of the long leg and the short leg of each unequal-leg angle (1). The number of threaded holes in each row is three. Third threaded holes matching the second threaded holes are provided on each equal-leg angle (3). A second bolt 4 sequentially passes through the second threaded holes and the third threaded holes and is locked with a second nut.

Images