CN108228992A - lightning rod flange design method and terminal device - Google Patents

Abstract

The invention relates to the technical field of lightning rods, and provides a flange design method for lightning rods and terminal equipment. The method includes: obtaining the relevant information of the collapsed lightning rod to analyze the cause of the collapse of the lightning rod, using the AR autoregressive technology based on the relevant information of the collapsed lightning rod, simulating the fluctuating wind load based on the Davenport spectrum, and considering the horizontal and vertical correlations at the same time, to obtain various According to the wind load time history samples of lightning rods of various structural types, the mechanical performance of the lightning rod flange is analyzed according to the wind load time history samples of various structural types of lightning rods, and the lightning rod flange is optimized according to the analysis results. The above lightning rod flange design method and terminal equipment can optimize and analyze the lightning rod flange, improve the wind resistance performance of the lightning rod, and ensure the safe operation of the lightning rod.

Description

Design method of lightning rod flange and terminal equipment

technical field

The invention belongs to the technical field of lightning rods, and in particular relates to a method for designing a lightning rod flange and a terminal device.

Background technique

The lightning rod is a towering structure with a large natural vibration period, and the dynamic response is quite significant under the action of wind load. In most cases, it is only affected by the wind load. Therefore, the lightning rod is greatly affected by the wind load.

Most of the lightning rods in the substation adopt a single steel pipe structure. In order to save land, most of them are erected on the frame columns of various voltage levels. Lightning protection calculation requirements are getting higher and higher. Taking the 220kV outlet frame in a 220kV substation (using GIS power distribution device) as an example, the frame height has been optimized from the previous 15m to the current standard 14m, and the height of the lightning rod has been increased from 35m to 46m, or even 50m, with a single steel pipe on the A-shaped column The length of the lightning rod is 32m, even 36m, and it is also hung with the ground wire in most cases. At this time, the lightning rod is still designed according to the routine. Compared with the thinner A-shaped pillar at the lower part, there is an obvious "top-heavy" phenomenon. .

Considering that most of the current lightning rod drop accidents are lightning rods erected on the A-shaped column of the frame, whether the single-steel steel tube lightning rod on the upper part of the frame is affected by the lower A-shaped column, whether it is affected by the wire and the ground wire, and whether it is affected by the wind load , Whether the dynamic effect of the lightning rod under the wind load is further amplified is worthy of further study.

Contents of the invention

In view of this, the embodiments of the present invention provide a method for designing a lightning rod flange and a terminal device, so as to solve the problem in the prior art that the structure of the lightning rod flange is not designed according to environmental factors.

The first aspect of the embodiments of the present invention provides a method for designing a lightning protection flange pin, including:

Obtain the relevant information of the collapsed lightning rod, and analyze the cause of the collapse of the lightning rod; the relevant information includes the design information, material information, processing information and installation information of the lightning rod;

According to the relevant information of the collapsed lightning rod, AR autoregressive technology is used to simulate the fluctuating wind load based on the Davenport spectrum, and the horizontal and vertical correlations are considered at the same time, and the wind load time history samples of various structural types of lightning rods are obtained;

According to the wind load time history samples of various types of lightning rods, the mechanical performance of the lightning rod flange is analyzed, and the lightning rod flange is optimized according to the analysis results.

Optionally, the structural types of the lightning rod include:

The single-steel tube lightning rod erected on the A-column of the frame, the independent floor-to-ceiling single-steel tube variable-section lightning rod, and the independent floor-to-ceiling equilateral triangular steel tube and angle steel lattice combined lightning rod.

Optionally, analyzing the mechanical performance of the lightning rod flange according to the wind load time history samples of various structural types of lightning rods includes:

The ANSYS finite element solid modeling of the lightning rod flange is carried out to analyze the stress and deformation of the connecting flange of the A-shaped column top and the upper single steel pipe lightning rod under the fluctuating wind load.

Optionally, the analysis of the stress and deformation of the connecting flange of the A-shaped column top and the upper single steel pipe lightning rod under the fluctuating wind load, including:

Analyze the stress and deformation of the flange bolts, flange plates and stiffening plates of the lightning rod connecting flange under the fluctuating wind load between the top of the A-shaped column and the upper single-steel lightning rod connecting flange.

Optionally, the analysis of the stress and deformation of the connecting flange of the A-shaped column top and the upper single steel pipe lightning rod under the fluctuating wind load, the stress and deformation of the connecting flange of the lightning rod also includes:

The stress and deformation of other components of the lightning rod connecting flange except the flange bolts, flange plates and stiffening plates are analyzed under the fluctuating wind load between the top of the A-shaped column and the upper single-steel lightning rod connecting flange.

Optionally, the lightning rod flange is a rigid flange, and when the axis of the rigid flange is under tension:

In the formula: is the tensile force of the most stressed bolt, N is the tensile force on the flange, n is the number of bolts on the flange, is the design value of bolt bearing capacity;

When the rigid flange is under the combined action of tension or compression or bending:

In the formula: M is the bending moment on the flange; N is the axial force on the flange; Y _i is the distance from the bolt center to the rotation axis; when M/|N|≥0.8r ₂ , take the tube 0.8 times half of the outer diameter is the axis of rotation; when M/|N|<0.8r ₂ , the center of the pipe is taken as the axis of rotation; Y is the distance from the center of the bolt with the largest force to the axis of rotation; r ₂ is the radius of the outer wall of the steel pipe.

Optionally, the design process of the flange thickness is:

Uniform load on the plate where L _y =min(1.8L _y1 ,2.2L _y2 );

maximum bending moment in the plate

Flange thickness

In the formula: β is the bending moment coefficient, t is the thickness of the flange, and f is the design value of the material strength.

Optionally, when the stiffener adopts butt welds, the thickness of the stiffener is:

1) For vertical butt welds:

2) For horizontal butt welds:

When the stiffened plate adopts fillet welds, the thickness of the stiffened plate is:

In the formula: P is the pressure corresponding to the stiffened plate of a bolt grid, α is the ratio of the reaction force borne by the stiffener, σ _f is the tensile stress perpendicular to the length direction of the weld, τ _f is the shear stress perpendicular to the length of the weld, B is the width of the stiffener, t is the thickness of the stiffener, and e is P eccentricity, h is the height of the stiffener, S ₁ is the height of the chamfer at the lower end of the stiffener, S ₂ is the dimension of the transverse chamfer at the lower end of the stiffener, is the design value of shear and tensile strength of butt weld, f is the design value of steel strength, and f _v is the design value of steel shear strength.

The second aspect of the embodiment of the present invention provides a lightning rod flange design terminal device, including a memory and a processor, the memory stores a computer program that can run on the processor, and the processor executes the The computer program implements the following steps:

Obtain the relevant information of the collapsed lightning rod, and analyze the cause of the collapse of the lightning rod; the relevant information includes the design information, material information, processing information and installation information of the lightning rod;

According to the relevant information of the collapsed lightning rod, AR autoregressive technology is used to simulate the fluctuating wind load based on the Davenport spectrum, and the horizontal and vertical correlations are considered at the same time, and the wind load time history samples of various structural types of lightning rods are obtained;

According to the wind load time history samples of various types of lightning rods, the mechanical performance of the lightning rod flange is analyzed, and the lightning rod flange is optimized according to the analysis results.

A third aspect of the embodiments of the present invention provides a computer-readable storage medium, the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, any method for designing a lightning rod flange as described above is implemented A step of.

Compared with the prior art, the embodiment of the present invention has the following beneficial effects: in the embodiment of the present invention, the relevant information of the collapsed lightning rod is obtained to analyze the cause of the collapse of the lightning rod. According to the relevant information of the collapsed lightning rod, AR autoregressive technology is used, based on the Davenport spectrum Simulate the fluctuating wind load, and consider the horizontal and vertical correlations at the same time to obtain the wind load time history samples of various structural types of lightning rods, and then analyze the mechanical performance of the lightning rod flange according to the wind load time history samples of various structural types of lightning rods, And according to the analysis results, the lightning rod flange is optimized, so that the lightning rod flange can be optimized, the wind resistance performance of the lightning rod is improved, and the safe operation of the lightning rod is ensured.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the descriptions of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only of the present invention. For some embodiments, those of ordinary skill in the art can also obtain other drawings based on these drawings without paying creative efforts.

Fig. 1 is the flowchart of the design method of lightning rod flange provided by the embodiment of the present invention;

Fig. 2 is a first schematic diagram of bolt force provided by the embodiment of the present invention;

Fig. 3 is a second schematic diagram of the force of the bolt provided by the embodiment of the present invention;

Fig. 4 is a schematic diagram of the flange provided by the embodiment of the present invention;

Fig. 5 is a schematic diagram of calculating the thickness of a stiffened plate provided by an embodiment of the present invention;

Fig. 6 is a schematic diagram of a contact unit in a flange model provided by an embodiment of the present invention;

Fig. 7 is the time history curve of the axial force FZ and the bending moment MX, MY of the flange provided by the embodiment of the present invention;

Fig. 8 is the stress-time history curve of the maximum stress point of the bolt provided by the embodiment of the present invention;

Fig. 9 is a curve diagram of the maximum bolt axial force after the bolts fail one by one provided by the embodiment of the present invention;

Fig. 10 is a Z-direction deformation curve of the maximum flange after the bolts fail one by one provided by the embodiment of the present invention;

Fig. 11 is a schematic diagram of the operating environment of the lightning rod flange design program provided by the embodiment of the present invention;

Fig. 12 is a program module diagram of the lightning rod flange design program provided by the embodiment of the present invention.

Detailed ways

In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. It will be apparent, however, to one skilled in the art that the invention may be practiced in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

In order to illustrate the technical solutions of the present invention, specific examples are used below to illustrate.

Embodiment one

Figure 1 shows the implementation process of the lightning rod flange design method provided by Embodiment 1 of the present invention, which is described in detail as follows:

Step S101 , obtain relevant information about the collapsed lightning rod, and analyze the cause of the collapsed lightning rod; the relevant information includes design information, material information, processing information and installation information of the lightning rod.

Among them, the structural types of the lightning rod include: a single steel pipe lightning rod erected on the A-shaped column of the frame, an independent ground single steel pipe with variable cross-section lightning rod, and an independent ground equilateral triangular steel pipe combined with an angle steel lattice lightning rod.

The design information, material information, processing information and installation information of the lightning rod may lead to the collapse of the lightning rod. According to the obtained information about the collapsed lightning rod, the exact cause of the collapse of the lightning rod is further analyzed.

In step S102, according to the relevant information of the collapsed lightning rod, AR autoregressive technology is used to simulate the fluctuating wind load based on the Davenport spectrum, and the horizontal and vertical correlations are considered at the same time to obtain the wind load time history samples of various structural types of lightning rods.

Step S103, analyzing the mechanical performance of the lightning rod flange according to the wind load time history samples of various types of lightning rods, and optimizing the lightning rod flange according to the analysis results.

Optionally, analyzing the mechanical performance of the lightning rod flange according to the wind load time history samples of various structural types of lightning rods includes:

The ANSYS finite element solid modeling of the lightning rod flange is carried out to analyze the stress and deformation of the connecting flange of the A-shaped column top and the upper single steel pipe lightning rod under the fluctuating wind load.

Specifically, the analysis of the stress and deformation of the connecting flange of the A-shaped column top and the upper single steel pipe lightning rod under the action of fluctuating wind load, including:

Analyze the stress and deformation of the flange bolts, flange plates and stiffening plates of the lightning rod connecting flange under the fluctuating wind load between the top of the A-shaped column and the upper single-steel lightning rod connecting flange.

In addition, the analysis of the stress and deformation of the connecting flange of the A-shaped column top and the upper single steel pipe lightning rod under the fluctuating wind load, the stress and deformation of the connecting flange of the lightning rod also includes:

The stress and deformation of other components of the lightning rod connecting flange except the flange bolts, flange plates and stiffeners are analyzed under the fluctuating wind load between the top of the A-shaped column and the upper single-steel lightning rod connecting flange.

In order to ensure the rigidity of the lightning rod, its flange generally adopts a rigid flange. Rigid flanges can be designed according to the following theory.

When the axis of the rigid flange is under tension:

In the formula: is the tensile force of the most stressed bolt, in Newton; N is the tensile force on the flange, in Newton; n is the number of bolts on the flange; Design value for bolt bearing capacity.

When the rigid flange is under the combined action of tension or compression or bending:

In the formula: M is the bending moment on the flange, the unit is N mm; N is the axial force on the flange, the unit is Newton; Y _i is the distance from the center of the bolt to the rotation axis, the unit is mm; When M/|N|≥0.8r ₂ , Y _i takes 0.8 times half of the outer diameter of the tube as the axis of rotation, see Figure 2; when M/|N|<0.8r ₂ , Y _i takes the center of the tube as the axis of rotation , see Figure 3; Y is the distance from the center of the maximum stressed bolt to the axis of rotation, in millimeters; r ₂ is the radius of the outer wall of the steel pipe, in millimeters.

For the thickness of the flange, the design of the flange is controlled by the tension condition, and the force diagram can be determined according to the three-sided support plate. The boundary conditions are three sides fixed and one side free, as shown in Figure 4.

Uniform load on the plate where L _y =min(1.8L _y1 ,2.2L _y2 );

The maximum bending moment M _max in the plate = β·q·L _x ² ;

Flange thickness

In the formula: β is the bending moment coefficient, which is checked from the "Static Calculation Manual of Building Structures" according to L _y /L _x ; t is the thickness of the flange, in millimeters; f is the design value of material strength, in MPa.

See Figure 5, for the thickness of the stiffener, when the stiffener adopts butt welds, the thickness of the stiffener is:

1) For vertical butt welds:

2) For horizontal butt welds:

When the stiffened plate adopts fillet welds, the thickness of the stiffened plate is:

In the formula: P is the pressure corresponding to the stiffened plate of a bolt grid, α is the ratio of the reaction force borne by the stiffener; _σf is the tensile stress perpendicular to the length direction of the weld, in MPa; _τf is the shear stress perpendicular to the length of the weld, in MPa; B is the width of the stiffener, The unit is mm; t is the thickness of the stiffening plate, the unit is mm; e is the P eccentricity, the unit is mm; _h is the height of the stiffening plate, the unit is _mm ; is the dimension of the transverse chamfer at the lower end of the stiffener, in millimeters; is the design value of shear and tensile strength of butt weld, in MPa; f is the design value of steel strength, in MPa; f _v is the design value of steel shear strength, in MPa.

In order to study the mechanical performance of the flange under the fluctuating wind load, ANSYS is used for finite element calculation. The applicable finite element model should first be determined.

The material of the model is all steel, and according to the elastic-plastic theory, the material performance model adopts the bilinear isotropic strengthening model BISO. The elastic modulus of steel is E=2.06×10 ⁵ MPa, Poisson's ratio μ=0.3, and the yield strength depends on the grade of steel.

According to previous related research, for steel pipes, flanges and stiffened plates, the available element types include solid elements and shell elements; for bolts, solid elements and rod elements are commonly used. Among them, under the premise of reasonable mesh division, the use of solid elements to simulate the flange parts is the most accurate. Therefore, the finite element model uses the solid element SOLID185 to model the various parts of the flange. It should be noted that in order to prevent "shear self-locking" or ill-conditioned system matrix from affecting the calculation accuracy, the dimensions of the solid elements in three directions should be as close as possible during the meshing process.

There are three types of contact in the flange model: contact A between the flanges, contact B between the nut and the flange, and contact C between the screw and the screw hole. Referring to Fig. 6, these three kinds of contacts are all surface-surface contacts, corresponding to the solid unit SOLID185, and the target unit and contact unit of the contact pair are TARGE170 and CONTA173 respectively.

When specifying the target surface and the contact surface, the principle of "convex, dense, soft, high and small is the contact surface" is followed. The weaker material is the contact surface, and the stronger material is the target surface. Since the bolt is more rigid than the flange and the material is stronger, the flange is selected as the contact surface and the bolt is the target surface. The actual performance is that the bolt can penetrate the flange, and the flange can only adapt to the invasion and deform.

The pre-tightening force of the bolt is applied through the pre-tightening unit PRETS179, and the application process is as follows: 1) The pre-tightening unit is established on the central section of the screw through the PSMESH command; 2) The specified pre-tightening load is applied through the SLOAD command. Under the action of only pretightening force, according to the simulation results, it can be seen that the pretightening force is applied to the central section of the bolt, while there is a contact force in the opposite direction on the contact surface between the nut and the flange.

Since the flange is subjected to axial force and bending moment at the same time, the model of the entire flange is established when modeling.

The bottom of the flange is connected to the top of the A-shaped column, and its rigidity is extremely high, which can be regarded as a rigid connection. Therefore, rigid constraints are imposed on the joints of the steel pipe and the stiffened plate at the bottom of the flange.

Axial force and bending moment load are applied on the top surface of the steel pipe on the upper part of the flange. According to Saint-Venant's principle, the length of the steel pipe on the upper part of the flange is 1 times the diameter of the steel pipe. A concentrated force is applied to each node on the top surface of the steel pipe to achieve an axially uniform force bearing effect. The application process of the bending moment is as follows: (1) A MASS21 element is established at the center of the steel pipe top surface, so that it has degrees of freedom Uxyz and ROTxyz in six directions; (2) Select the nodes of the MASS element and the nodes of the steel pipe top surface, and The CERIG command establishes a rigid surface to ensure the transmission of the bending moment; (3) apply a concentrated bending moment to the MASS unit.

In order to better analyze the mechanical performance of the flange, the time history analysis of fluctuating wind load is carried out. The axial force and bending moment time-history curves of the flange are extracted from the model of the entire frame, and the flange model is imported for time-history calculation. The time course curves of axial force FZ and bending moments MX, MY on the flange are shown in Fig. 7.

In view of the large number of nodes and units in the finite element model, in order to take into account the calculation efficiency and calculation accuracy, loads from 0 to 60 s are taken for time-history analysis, and the analysis step is 0.1 s.

Take the load step time=52.9, which bears a large force near the end of loading, for illustration. According to the simulation results, it can be seen that the stress on the flange is generally small, and the maximum stress is 155MPa. The places with greater stress are distributed around the bolt holes, and the stress on the edge of the flange is very small. The maximum stress on the stiffened plate is 266MPa, which occurs at the stress concentration at the junction of the stiffened plate and the steel pipe, and the stress in most areas of the stiffened plate does not exceed 90MPa. The bolts are under axial tension, and the maximum bolt stress is 279MPa, which is less than the allowable stress of the bolt. The stress distribution trend of the bolt is consistent with that of the flange. The maximum stress of the steel pipe is 100MPa, which is located at the junction of the steel pipe and the stiffened plate, and the stress of the entire steel pipe is within the elastic range.

The deformation of the flange at the end of the loading is shown in the figure below. The flange is characterized by bending deformation. The maximum displacement of the flange in the Z direction is 0.037mm, and the minimum displacement in the Z direction is -0.024mm. Compared with the diameter of the flange, the method at this time The inclination of the bottom of the flange is about 1/8700, indicating that the deformation of the flange has little contribution to the deformation of the lightning rod.

The lightning rod swings greatly under the action of wind for a long time, and the stress of the bolts changes continuously, causing fatigue damage to some bolts. Therefore, the fatigue analysis of the bolts where the maximum stress is located is carried out. According to the simulation, the stress-time history curve of the maximum stress point is shown in Fig. 8. Among them, the maximum stress at this point is 394.1MPa, the minimum stress is 260.4MPa, and the bolt stress amplitude is 133.7MPa.

At present, my country's steel structure design code lacks relevant design regulations for the fatigue design of bolted tension connections. Internationally, the German code VDI-2230 has relatively mature calculations on bolt fatigue, which can provide a reference for analysis. The alternating stress amplitude of bolt fatigue limit in VDI-2230 can be calculated by the following formula:

σ _ASV ＝0.85(150/d+45)

After calculation, for the finite element calculation example, the allowable value of the bolt stress amplitude corresponding to the number of stress cycles N=2×10 ⁶ is 86.0MPa. The bolt stress amplitude is greater than the allowable stress amplitude, and cracks will appear as the fatigue damage accumulates during use, eventually leading to fatigue failure.

On the other hand, the value of the bolt preload is also critical. The greater the pre-tightening force, the smaller the bolt alternating stress and the smaller the bolt stress range. Appropriately increasing the bolt pre-tightening force can not only improve the anti-loosening ability of the bolt, but also improve the fatigue life of the bolt. Therefore, it is recommended that the bolt pretightening force be as large as possible within a reasonable range.

In addition, VDI-2230 pointed out that due to the introduction of residual compressive stress, the fatigue limit of bolts rolled after heat treatment is higher than that of bolts rolled before heat treatment, up to 1.7 times the original. Therefore, in the processing technology of bolts, it is recommended to use bolts rolled after heat treatment.

When some bolts fail due to fatigue or other reasons, the stress of the remaining bolts increases due to redistribution. Taking the typical load FZ=32kN, M=283kN m as an example, calculate the force of the remaining bolts after the bolts fail one by one, and the calculation results As shown in Table 1 below.

Table 1 Calculation results of bolt failure one by one

Number of failed bolts Maximum bolt axial force (kN) Tensile bearing capacity of bolts (kN) 0 78 184 2 107 184 4 156 184 6 246 184

When one bolt fails, under a typical load, the maximum stress of the steel pipe is 248MPa, and the flange plate in the area where the bolt with the largest force is still in the elastic stage, only the stress concentration around the screw hole is the maximum stress of 341MPa. The stress at the junction of the stiffened plate and the flange is less than 330MPa. The maximum stress of the bolt is 544MPa, which is located at the local stress concentration point. The tensile force of the bolt is 149.9kN, which does not exceed the yield strength of the bolt, and the bolt has not yet been damaged. At this time, the maximum Z-direction deformation of the flange is 0.54mm, and the flange is inclined about 1/856.

When the two bolts fail, under typical load, the maximum stress of the steel pipe is 248MPa, and most of the flanges in the area where the bolts bear the largest force are still in the elastic stage. The stress at the junction of the stiffened plate and the flange is less than 330MPa. The maximum bolt stress is 655MPa, which is located at the local stress concentration point. The bolt tension is 179.6kN, which is not exceeded but very close to the bolt bearing capacity, and the bolt is about to fail. At this time, the maximum Z-direction deformation of the flange is 0.91 mm, and the flange is tilted by about 1/530.

When the three bolts fail, under the typical load, the maximum stress of the steel pipe is 337MPa, and most of the flanges in the area where the bolts are subjected to the maximum stress are in the elastic stage, and the stress concentration around the screw holes is at a maximum of 425MPa, and the local area begins to enter plasticity . The stress at the junction of the stiffened plate and the flange in this area is greater than 296MPa, and some of them enter plasticity. The maximum stress of the bolt is 648MPa, and the stress on the side of the screw with a larger force generally exceeds 577MPa. The tensile force of the bolt is 202.5kN, which exceeds the tensile bearing capacity of the bolt. It can be considered that the bolt has been damaged at this time. At this time, the maximum Z-direction deformation of the flange is 1.31 mm, and the flange is inclined by about 1/371.

When five bolts fail, under typical load, the maximum stress of the steel pipe is 363MPa, most of the stress of the flange plate in the area where the maximum bolt is located exceeds 293MPa, and the surroundings of the screw holes enter plasticity. The stress at the junction of the blue and the plate is greater than 330MPa. The maximum stress of the bolt has exceeded 600MPa, and the local stress concentration point even reaches 673MPa, which exceeds the yield strength of the bolt. The tensile force of the bolt is 273.3kN, and it can be considered that the bolt has been damaged at this time. At this time, the maximum Z-direction deformation of the flange is 2.55mm, the flange is inclined by about 1/195, and the deformation of the lightning rod is significant.

Based on the comprehensive analysis of the above finite element and hand calculation results, the development of the maximum axial force of the bolts is shown in the figure when the bolts fail sequentially. It can be seen from Figure 9 and Figure 10 that as the number of bolt failures increases, the maximum axial force of the bolts increases rapidly. Under the same failed bolt, the finite element result is about 50kN larger than the hand calculation result. This is due to the existence of the pre-tightening force, and the flange rotation axis used in the hand calculation deviates from the real situation, resulting in a smaller bolt axial force in the hand calculation result. Judging from the development trend of the bolt axial force, it was not until three bolts failed that the other bolts of the flange began to yield, and the flange joints were damaged. This shows that the flange has a large static margin, which can provide time for early detection of potential accidents.

At the same time, as the bolts fail one by one, the Z-direction deformation of the flange also shows a linear growth trend. Monitoring the top displacement of the lightning rod can detect abnormal deformation of the flange in time and provide early warning for accidents.

In view of the possible low temperature cold brittleness of steel, the stiffening plate of the flange may also fail. When all stiffeners fail, the original rigid flange is converted to a flexible flange type. For all cases of stiffened plate failure, the typical load FZ=32kN, M=283kN·m is taken as an example to carry out finite element calculation, and the calculation results are as follows.

When one stiffening plate fails, under typical load, the maximum stress of the steel pipe is 253MPa, which appears at the junction of the steel pipe and the flange. Most of the stress of the flange plate in the area where the bolt with the largest force does not exceed 204MPa, and the stress around the screw hole is relatively large due to the stress concentration, the maximum is 305MPa, all of which are yielded. The maximum stress of the bolt is 473MPa, which does not exceed the yield strength of the bolt. The tensile force of the bolt is 133.4kN, which is about 8kN higher than that of the undamaged stiffener. At this time, the maximum Z-direction deformation of the flange is 0.31 mm, and the flange is tilted by about 1/1357. Therefore, the consequences of stiffener failure are safer than bolt failure.

When all stiffening plates fail, under typical loads, the maximum stress of the steel pipe is 390MPa, which occurs at the junction of the steel pipe and the flange. The stress of the flange plate in the area where the bolt with the largest force is mostly not more than 322MPa, and the stress around the screw hole is relatively large due to the stress concentration, the maximum is 413MPa. The maximum stress of the bolt is 652MPa, which exceeds the yield strength of the bolt, and the tensile force of the bolt is 208.1kN. It can be considered that the bolt has been damaged at this time. At this time, the maximum Z-direction deformation of the flange is 0.81 mm, and the flange is tilted by about 1/490.

Based on the above analysis, it can be known that:

1. The finite element model simulates the stress of the entire lightning rod flange under fluctuating wind loads, and the results are more accurate and credible.

2. The stress of each part of the flange under the fluctuating wind load is within the elastic range, and a large margin is left.

3. The fatigue stress amplitude of the bolts under the fluctuating wind load is 133.7MPa, exceeding the limit value of 86MPa allowed by VDI-2230. Fatigue damage is the main reason for bolt fracture.

4. When the bolts fail one by one, until the third bolt fails, the maximum bolt force exceeds its tensile bearing capacity, and the flange is damaged.

5. When the stiffening plate fails, the consequences are not as serious as the failure of the bolts. Therefore, more attention should be paid to the protection measures of the bolts.

6. In order to avoid similar incidents, the measures that can be taken are:

1) Improve the material requirements of flanges and bolts, and choose D-grade steel;

2) Improve the bolt processing technology and select bolts rolled before heat treatment;

3) Strengthen the bolts, ensure the bolt margin, reduce the bolt stress, and reduce the bolt stress amplitude in disguise;

4) Increasing the bolt pre-tightening force within a reasonable range can reduce the bolt stress amplitude;

5) Ensure the flatness of the contact surface of the flange and reduce the swing of the lightning rod caused by the gap.

The above lightning rod flange design method obtains the relevant information of the collapsed lightning rod to analyze the cause of the collapse of the lightning rod. According to the relevant information of the collapsed lightning rod, the AR autoregressive technology is used to simulate the fluctuating wind load based on the Davenport spectrum, and the horizontal and vertical correlations are considered at the same time. The wind load time history samples of various structural types of lightning rods are obtained, and then according to the wind load time history samples of various structural types of lightning rods, the mechanical performance of the lightning rod flange is analyzed, and the lightning rod flange is optimized according to the analysis results, so that the The lightning rod flange is optimized to improve the wind resistance performance of the lightning rod and ensure the safe operation of the lightning rod.

It should be understood that the sequence numbers of the steps in the above embodiments do not mean the order of execution, and the execution order of each process should be determined by its functions and internal logic, and should not constitute any limitation to the implementation process of the embodiment of the present invention.

Embodiment two

Corresponding to the lightning rod flange design method described in the above embodiments, FIG. 11 shows a schematic diagram of the operating environment of the lightning rod flange design program provided by the embodiment of the present invention. For ease of description, only the parts related to this embodiment are shown.

In this embodiment, the lightning rod flange design program 200 is installed and run in the terminal equipment 20 . The terminal device 20 may include, but not limited to, a memory 201 and a processor 202 . FIG. 11 only shows terminal device 20 with components 201-202, but it should be understood that implementation of all of the illustrated components is not required and that more or fewer components may instead be implemented.

The storage 201 may be an internal storage unit of the terminal device 20 in some embodiments, for example, a hard disk or a memory of the terminal device 20 . The memory 201 may also be an external storage device of the terminal device 20 in other embodiments, such as a plug-in hard disk equipped on the terminal device 20, a smart memory card (Smart MediaCard, SMC), a secure digital ( Secure Digital (SD) card, flash memory card (Flash Card), etc. Further, the memory 201 may also include both an internal storage unit of the terminal device 20 and an external storage device. The memory 201 is used to store application software and various data installed in the terminal device 20 , such as program codes of the accelerated life test sample distribution program 200 , and the like. The memory 201 can also be used to temporarily store data that has been output or will be output.

In some embodiments, the processor 202 may be a central processing unit (Central Processing Unit, CPU), a microprocessor or other data processing chips, which are used to run the program codes stored in the memory 201 or process data, such as executing The lightning rod flange design program 200 and so on.

The terminal device 20 may further include a display, and in some embodiments, the display may be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, an OLED (Organic Light-Emitting Diode, organic light-emitting diode) touch device, and the like.

Please refer to FIG. 12 , which is a program module diagram of the lightning rod flange design program 200 provided by the embodiment of the present invention. In the present embodiment, the lightning rod flange design program 200 can be divided into one or more modules, and the one or more modules are stored in the memory 201 and executed by one or more processors ( This embodiment is executed by the processor 202) to complete the present invention. For example, in FIG. 12 , the lightning rod flange design program 200 can be divided into an information acquisition module 301 , a processing module 302 and an optimization design module 303 . The module referred to in the present invention refers to a series of computer program instruction segments capable of completing specific functions, which is more suitable than a program to describe the execution process of the lightning rod flange design program 200 in the terminal device 20 . The following description will specifically introduce the functions of the modules 301-303.

Wherein, the information acquisition module 301 is used to obtain relevant information of the collapsed lightning rod, and analyze the cause of the collapse of the lightning rod; the relevant information includes design information, material information, processing information and installation information of the lightning rod.

The processing module 302 is used for simulating fluctuating wind loads based on Davenport spectrum by using AR autoregressive technology based on relevant information of collapsed lightning rods, and taking horizontal and vertical correlations into consideration to obtain time history samples of wind loads for various structural types of lightning rods.

The optimization design module 303 is used to analyze the mechanical performance of the lightning rod flange according to the wind load time history samples of various structural types of lightning rods, and optimize the lightning rod flange according to the analysis results.

Optionally, the structural types of the lightning rod include:

The single-steel tube lightning rod erected on the A-column of the frame, the independent floor-to-ceiling single-steel tube variable-section lightning rod, and the independent floor-to-ceiling equilateral triangular steel tube and angle steel lattice combined lightning rod.

Optionally, the processing module 302 is used to: perform ANSYS finite element solid modeling on the lightning rod flange, and analyze the stress and deformation of the connecting flange of the A-shaped column top and the upper single steel pipe lightning rod under the fluctuating wind load. .

Optionally, the processing module 302 is specifically used for:

Analyze the stress and deformation of the flange bolts, flange plates and stiffening plates of the lightning rod connecting flange under the fluctuating wind load between the top of the A-shaped column and the upper single-steel lightning rod connecting flange.

As a possible implementation, the lightning rod flange is a rigid flange, and when the axis of the rigid flange is under tension:

In the formula: is the tensile force of the most stressed bolt, N is the tensile force on the flange, n is the number of bolts on the flange, is the design value of bolt bearing capacity;

When the rigid flange is under the combined action of tension or compression or bending:

In the formula: M is the bending moment on the flange; N is the axial force on the flange; Y _i is the distance from the bolt center to the rotation axis; when M/|N|≥0.8r ₂ , take the tube 0.8 times half of the outer diameter is the axis of rotation; when M/|N|<0.8r ₂ , the center of the pipe is taken as the axis of rotation; Y is the distance from the center of the bolt with the largest force to the axis of rotation; r ₂ is the radius of the outer wall of the steel pipe.

As another possible implementation, the design process of the thickness of the flange is:

Uniform load on the plate where L _y =min(1.8L _y1 ,2.2L _y2 );

The maximum bending moment M _max in the plate = β·q·L _x ² ;

Flange thickness

In the formula: β is the bending moment coefficient, t is the thickness of the flange, and f is the design value of the material strength.

As a possible implementation method, when the stiffened plate adopts butt weld, the thickness of the stiffened plate is:

1) For vertical butt welds:

2) For horizontal butt welds:

When the stiffened plate adopts fillet welds, the thickness of the stiffened plate is:

In the formula: P is the pressure corresponding to the stiffened plate of a bolt grid, α is the ratio of the reaction force borne by the stiffener, σ _f is the tensile stress perpendicular to the length direction of the weld, τ _f is the shear stress perpendicular to the length of the weld, B is the width of the stiffener, t is the thickness of the stiffener, and e is P eccentricity, h is the height of the stiffener, S ₁ is the height of the chamfer at the lower end of the stiffener, S ₂ is the dimension of the transverse chamfer at the lower end of the stiffener, is the design value of shear and tensile strength of butt weld, f is the design value of steel strength, and f _v is the design value of steel shear strength.

Those skilled in the art can clearly understand that for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used for illustration. In practical applications, the above-mentioned functions can be assigned to different functional units, Completion of modules means that the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment may be integrated into one processing unit, or each unit may exist separately physically, or two or more units may be integrated into one unit, and the above-mentioned integrated units may adopt hardware It can also be implemented in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the protection scope of the present application. For the specific working process of the units and modules in the above system, reference may be made to the corresponding process in the foregoing method embodiments, and details will not be repeated here.

In the above-mentioned embodiments, the descriptions of each embodiment have their own emphases, and for parts that are not detailed or recorded in a certain embodiment, refer to the relevant descriptions of other embodiments.

Those skilled in the art can appreciate that the units and algorithm steps of the examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed by hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be regarded as exceeding the scope of the present invention.

In the embodiments provided in the present invention, it should be understood that the disclosed apparatus/terminal equipment and method may be implemented in other ways. For example, the device/terminal device embodiments described above are only illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units Or components may be combined or may be integrated into another system, or some features may be omitted, or not implemented. In another point, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of devices or units may be in electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, each unit may exist separately physically, or two or more units may be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

If the integrated module/unit is realized in the form of a software function unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention realizes all or part of the processes in the methods of the above embodiments, and can also be completed by instructing related hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer When the program is executed by the processor, the steps in the above-mentioned various method embodiments can be realized. Wherein, the computer program includes computer program code, and the computer program code may be in the form of source code, object code, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a removable hard disk, a magnetic disk, an optical disk, a computer memory, and a read-only memory (ROM, Read-Only Memory) , random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium may be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable Excludes electrical carrier signals and telecommunication signals.

The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still carry out the foregoing embodiments Modifications to the technical solutions recorded in the examples, or equivalent replacement of some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should be included in within the protection scope of the present invention.

Claims (10)

1. A kind of 1. lightning rod flange design method, which is characterized in that including：

   The relevant information for the lightning rod that collapses is obtained, analyzes the reason of lightning rod collapses；The relevant information includes setting for lightning rod Count information, material information, machining information and mount message；

   According to the relevant information for the lightning rod that collapses, with AR autoregression technologies, based on Davenport spectrum analog wind loads, Horizontal and vertical correlation is considered simultaneously, obtains the wind load time-history sample of various structure type lightning rods；

   According to the wind load time-history sample of various structure type lightning rods, analyze the stress performance of lightning rod flange, and according to point Analysis result optimizes lightning rod flange.
2. 2. lightning rod flange design method as described in claim 1, which is characterized in that the structure type of lightning rod includes：

   Erect the single steel pipe lightning rod on framework A word columns, independent landing single steel pipe variable cross-section lightning rod, independent landing etc. The lightning rod of side triangle steel pipe and angle steel lattice convolution.
3. 3. lightning rod flange design method as claimed in claim 2, which is characterized in that described to be taken shelter from the thunder according to various structure types The wind load time-history sample of needle analyzes the stress performance of lightning rod flange, including：

   ANSYS finite element solid modelings, analysis A words capital and top single steel pipe lightning rod connecting flange are carried out to lightning rod flange Under wind loads effect, the stress of lightning rod connecting flange and deformation.
4. 4. lightning rod flange design method as claimed in claim 3, which is characterized in that the analysis A words capital and top are single Steel pipe lightning rod connecting flange is under wind loads effect, the stress of lightning rod connecting flange and deformation, including：

   A words capital is analyzed with top single steel pipe lightning rod connecting flange under wind loads effect, lightning rod connecting flange Flange bolt, the stress of flanged plate and stiffener and deformation.
5. 5. lightning rod flange design method as claimed in claim 4, which is characterized in that the lightning rod flange is stiffness method Orchid, when the axial tension of rigid flange acts on：

   In formula：The pulling force of a bolt for stress maximum, N are the pulling force suffered by flange, and n is Number of Bolts on ring flange Mesh,For bolt design ultimate bearing capacity；

   When rigid flange tension or pressure or curved collective effect：

   In formula：M is the moment of flexure suffered by flange；N is the pivotal role power suffered by flange；Y_iDistance for bolt-center to rotary shaft； Work as M/ | N | >=0.8r₂When, take pipe outside diameter half 0.8 times is rotary shaft；Work as M/ | N |<0.8r₂When, it is rotary shaft to take tube hub； Y is distance of the stress maximum bolt-center to rotary shaft；r₂For outer wall of steel pipe radius.
6. 6. lightning rod flange design method as claimed in claim 5, which is characterized in that the design process of flange thickness is：

   Evenly load on plateWherein L_y=min (1.8L_y1,2.2L_y2)；

   Maximal bending moment M in plate_max=β qL_x ²；

   Flange thickness

   In formula：β is bending moment coefficients, and t is flange thickness, and f is design value for strength of material.
7. 7. lightning rod flange design method as claimed in claim 6, which is characterized in that when stiffener uses butt weld, add Strength plate thickness is：

   1) during vertical butt weld：

   2) during horizontal butt weld：

   When stiffener uses fillet weld, plate thickness of putting more energy into is：

   In formula：P be the stiffener of bolt area lattice to the pressure that should bear,α undertakes instead for stiffener The ratio of power, σ_fFor the tensile stress perpendicular to fusion length direction, τ_fFor the shear stress perpendicular to fusion length direction, B is puts more energy into Plate width, for t to put more energy into plate thickness, e is P eccentricities, and h is stiffener height, S₁For stiffener lower end corner cut height, S₂To put more energy into Plate lower end transverse direction corner cut size,f_t ^WFor butt weld shearing resistance, tensile strength design value, f is steel strength design value, f_vFor Steel shearing strength design value.
8. 8. a kind of lightning rod flange design device, which is characterized in that including：

   Data obtaining module for obtaining the relevant information for the lightning rod that collapses, analyzes the reason of lightning rod collapses；The related letter Breath includes design information, material information, machining information and the mount message of lightning rod.

   For the relevant information according to the lightning rod that collapses, with AR autoregression technologies, mould is composed based on Davenport for processing module Intend wind loads, while consider horizontal and vertical correlation, obtain the wind load time-history sample of various structure type lightning rods.

   Optimization design module for the wind load time-history sample according to various structure type lightning rods, analyzes lightning rod flange Stress performance, and lightning rod flange is optimized according to analysis result.
9. 9. a kind of lightning rod flange design terminal device, which is characterized in that including memory, processor, deposited in the memory The computer program that can be run on the processor is contained, the processor realizes following step when performing the computer program Suddenly：

   The relevant information for the lightning rod that collapses is obtained, analyzes the reason of lightning rod collapses；The relevant information includes setting for lightning rod Count information, material information, machining information and mount message；

   According to the relevant information for the lightning rod that collapses, with AR autoregression technologies, based on Davenport spectrum analog wind loads, Horizontal and vertical correlation is considered simultaneously, obtains the wind load time-history sample of various structure type lightning rods；

   According to the wind load time-history sample of various structure type lightning rods, analyze the stress performance of lightning rod flange, and according to point Analysis result optimizes lightning rod flange.
10. 10. a kind of computer readable storage medium, the computer-readable recording medium storage has computer program, and feature exists In when the computer program is executed by processor the step of realization such as any one of claim 1 to 8 the method.