CN112733302A - Method for determining calculated length coefficient of combined-framework single steel pipe - Google Patents
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Abstract
The invention relates to a method for determining a calculated length coefficient of a joint framework single steel pipe, which is operated with the assistance of computer equipment and programs and at least comprises the following steps: step A: deducing a single steel pipe calculation length coefficient according to the steel structure stable calculation theoretical modeling; and B: screening simplified working conditions according to the actual engineering model and analyzing the stability by using a finite element method; and C: extracting a peripheral local model according to the influence factors, and deducing and calculating a length coefficient; step D: simulating an actual working condition to establish a test model for carrying out a stability test of the framework single steel pipe; step E: summarizing data and carrying out comparative analysis on each calculated length coefficient obtained in the steps A, B, C and D; step F: and E, adjusting and determining a recommended value of the calculated length coefficient according to the analysis result obtained in the step E. The stability of single steel pipe post is calculated more accurately, when guaranteeing structure safety, can save steel volume by the at utmost, promotes economic benefits.
Description
Technical Field
The invention relates to the field of combined framework design of power transmission lines, in particular to a method for determining a calculated length coefficient of a single steel pipe of a combined framework.
Background
A frame column in a traditional 500kV combined frame is usually welded with a round steel pipe column through A-type straight seam welding, a frame beam is usually hinged with a lattice type steel beam column through a triangular deformation section, steel pipe chords, angle steel web members and bolts, and splicing joints of the beam and the column are connected through flanges. Subsequently, with continuous optimization of engineering design on the basis, the inlet and outlet framework columns in the combined framework are improved to adopt a single steel pipe column to replace a conventional A-type column, and only the middle framework column is kept to still adopt the A-type column. Specifically, as shown in fig. 1, the combined framework has the advantages that the horizontal tension of the framework in the outgoing line direction is transmitted to the a-type column of the middle framework through the connecting beam and the bus beam, so that the horizontal load of the wires entering and exiting from the two sides is mainly borne by the a-type framework, and the single steel tube outgoing line framework mainly bears the vertical load of the wires and forms a fully-combined stress system with the a-type column.
For the single steel pipe structure adopted in the improved 500kV combined framework, the calculation of the length coefficient is undoubtedly the key index for determining the structural stability. However, in the existing specifications and technologies, a definite determination mode is not provided for the calculated length coefficient of the single steel pipe structure of the combined framework, the use of the single steel pipe structure in the combined framework is increasingly wide in practical engineering, the influence factors on the calculated length coefficient are more complicated and changeable due to various practical working condition forms, and the research on the determination method of the calculated length coefficient of the single steel pipe structure is of great importance in order to ensure the stability of the single steel pipe structure in the combined framework.
In view of the problems, the invention innovatively provides a method for determining the calculated length coefficient of the single steel pipe column in the combined framework of the 500kV transformer substation, so that the stable calculation of the single steel pipe column is more accurate, the structure safety is ensured, the section of the single steel pipe column can be optimized to the greatest extent, and the steel quantity is saved.
Disclosure of Invention
In view of the problems of the prior art, the inventor considers that an improved technical scheme is provided, and designs a method for determining the calculated length coefficient of the combined-framework single steel pipe, which has the specific technical means that:
the invention provides a method for determining the calculated length coefficient of a combined frame single steel pipe, which operates by computer equipment and a program and at least comprises the following steps:
step A: deducing a single steel pipe calculation length coefficient according to the steel structure stable calculation theoretical modeling;
and B: screening simplified working conditions according to the actual engineering model and analyzing the stability by using a finite element method;
and C: extracting a peripheral local model according to the influence factors, and deducing and calculating a length coefficient;
step D: simulating an actual working condition to establish a test model for carrying out a stability test of the framework single steel pipe;
step E: summarizing data and carrying out comparative analysis on each calculated length coefficient obtained in the steps A, B, C and D;
step F: and E, adjusting and determining a recommended value of the calculated length coefficient according to the analysis result obtained in the step E.
Further, the specific derivation manner of calculating the length coefficient in step a is as follows:
step A1: establishing a plurality of structural calculation simplified models, wherein the specific form of the structural calculation simplified model can be a straight rod member with equal sections, the straight rod member is rigidly connected with a column base and comprises two layers of supports, and the axis of the straight rod member is uniformly pressed;
step A2: setting the lower part of the structural calculation simplified model component as an AB section and the upper part as a BC section, and respectively deriving buckling load equations of the AB section component and the BC section component;
step A3: substituting the corresponding parameters of each structural calculation simplified model component into the buckling load equations of the AB section component and the BC section component deduced in the step A2 respectively, and calculating the critical load of each structural calculation simplified model component when the AB section and the BC section are unstable;
step A4: and C, comparing the critical load values of the AB section and the BC section of the simplified model component calculated by the structures in the step A3, determining a critical instability section and calculating the calculation length coefficient of the simplified model component calculated by the structures.
Further, the specific derivation process of the buckling load equations of the AB segment component and the BC segment component in the step a2 includes:
according to the displacement boundary conditions at the two ends of the BC section component, the bending line is set as a sine curve and satisfies the formula (1),
substituting the formula (1) into the formula (2) to deduce the strain energy,
the formula (1) is converted into a formula (3) to deduce the external force potential energy as follows,
further, the potential energy of the structural calculation simplified model is calculated according to the formula (4),
when the structural balance state is set, the formula (5) is satisfied,
further, the formula (6) can be derived,
converting the equation (6) to obtain a buckling load solving equation (7) of the BC section component,
according to the displacement boundary conditions at the two ends of the AB section component, the bending line equation is set to satisfy the formula (8),
y＝a1x2(l-x)+a2x3(l-x)+… (8)，
substituting the first two terms of the series of the formula (8) into the potential energy equation (9) of the structural calculation simplified model,
after the conversion, the formula (10) is obtained,
when the structural balance state is set, the following formula is satisfied,
further, the following formula (11) and formula (12) can be obtained by combining the above formula (10),
according to a1And a2Not all being zero, equation (13) can be derived,
the formula (14) can be obtained by further opening and sorting the formula (13),
the formula (15) obtained by solving the minimum root of the formula (14) is a buckling load solving equation of the AB section component,
further, the step B includes the steps of:
step B1: simplifying the actual framework column into a uniform-section steel pipe column model according to the engineering actual model;
step B2: screening out various working condition simplified models according to the engineering model;
step B3: and respectively performing stability analysis on each working condition simplified model in the step B2, wherein the stability analysis comprises the following analysis processes:
(1) performing buckling analysis according to characteristic values of the conditions without introducing geometric nonlinearity and material nonlinearity, respectively applying unit axial force to the top of each working condition simplified model, calculating to obtain buckling modal parameters of the first 2 orders, further calculating to obtain instability loads without introducing double nonlinearity, substituting the instability loads into an Euler formula, and performing inverse calculation to obtain the calculated length coefficient of each working condition simplified model component;
(2) and carrying out buckling analysis according to the characteristic value of the introduced geometric nonlinearity, calculating to obtain unstable loads of all the modes, obtaining the stability coefficient of all the modes according to the unstable loads, and further calculating to obtain the calculated length coefficient of the simplified model component under the condition of introducing the geometric nonlinearity.
Further:
the at least one local model extracted in the step C is a peripheral structure model of the member in the screening simplified condition in the step B, which influences the calculated length coefficient of the member in the whole frame, and comprises a peripheral support structure model;
in the step C, the calculation analysis dimensions of the local model include first-order instability and second-order instability, and the critical load and the calculation length coefficient of each instability plane of each local model are further calculated according to the situations of introducing no nonlinearity and introducing nonlinearity.
Further, in the step D, a specific implementation manner may be:
step D1: simplifying a test reduced-scale steel pipe column model according to actually adopted components of the project;
step D2: selecting at least one working condition from the screening simplified working conditions in the step B to establish a test model;
step D3: the grouping stability analysis calculation was performed for the above test model in step D2.
Further:
the stability calculation of the test model in the step D3 includes the average value of the breaking load and the calculated length coefficient of each group of test members under the test requirements.
Further, the step E includes the following comparison method for calculating the length coefficient:
(1) comparing and analyzing the calculation result of the structural calculation simplified model component calculated according to the step B with the test result of the test model calculated in the step D, wherein the analysis data comprises the calculation length coefficient value and the ratio of each instability plane of each model;
(2) comparing and analyzing the calculation result of the structural calculation simplified model component calculated according to the step B with the theoretical calculation result of the step A, wherein the analysis data comprises the calculation length coefficient values and the ratios of the calculation length coefficient values of the instability planes of the models;
(3) and C, comparing and analyzing the calculation result of the structural calculation simplified model component calculated according to the step B and the calculation result of the local model calculated according to the step C, wherein the analysis data comprises the calculation length coefficient values and the ratios of the calculation length coefficient values of the instability planes of the models.
Further, the step F includes the steps of:
step F1: adjusting and optimizing the coefficient value of each calculated length according to the comparative analysis result in the step E;
step F2: and performing statistical display of the recommended value of each calculated length coefficient according to each instability plane of each working condition model.
The method has the beneficial effects that the method for determining the calculated length coefficient of the combined-framework single steel pipe is provided. The method comprises the steps of utilizing a model containing steel structure stability calculation theory to build a model and deduce, analyzing the stability of a finite element scheme working condition model, extracting the calculation and analysis of local model simulation influence parameters, establishing a test model to carry out the calculation of the stability of the single steel pipe of a framework in multiple modes of a single steel pipe stability test and analyzing and comparing the calculated length coefficient, obtaining the more accurate calculated length coefficient meeting the stability of the single steel pipe column after further optimization, fully ensuring the structure safety, realizing the optimal selection of the consumable materials of the cross section of the single steel pipe column to the maximum extent, saving the steel quantity, reducing the engineering cost, and obviously improving the economic benefit.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a conventional 500kV combined framework adopting a single steel pipe column.
FIG. 2 is a block diagram illustrating the general flow of the method of the present invention.
Fig. 3 is a schematic diagram of a simplified calculation model 1 for the theoretical modeling of steel structure stability calculation according to the present invention.
Fig. 4 is a schematic diagram of a computational simplified model 2 of the steel structure stability computational theory modeling of the present invention.
FIG. 5 is a schematic diagram of a simplified model example of working condition 1 of the finite element scheme screened by the present invention.
FIG. 6 is a schematic diagram of a simplified model example of finite element solution condition 2 screened in accordance with the present invention.
FIG. 7 is a schematic diagram of a simplified model example of condition 3 of the finite element scheme screened in accordance with the present invention.
FIG. 8 is a schematic diagram of a simplified model example of finite element solution condition 4 screened in accordance with the present invention.
FIG. 9 is a schematic diagram of a simplified model example of finite element solution condition 5 screened in accordance with the present invention.
FIG. 10 is a schematic diagram of an example of the extracted partial model 1 around the component according to the present invention.
FIG. 11 is a schematic diagram of an example of the extracted local model 2 around the component according to the present invention.
FIG. 12 is a schematic diagram of an example of the extracted local model 3 around the component according to the present invention.
Detailed Description
Referring to fig. 2, the main steps of the method of the present invention are shown in fig. 2:
step A: deducing a single steel pipe calculation length coefficient according to the steel structure stable calculation theoretical modeling;
and B: screening simplified working conditions according to the actual engineering model and analyzing the stability by using a finite element method;
and C: extracting a peripheral local model according to the influence factors, and deducing and calculating a length coefficient;
step D: simulating an actual working condition to establish a test model for carrying out a stability test of the framework single steel pipe;
step E: summarizing data and carrying out comparative analysis on each calculated length coefficient obtained in the steps A, B, C and D;
step F: and E, adjusting and determining a recommended value of the calculated length coefficient according to the analysis result obtained in the step E.
The specific derivation manner for calculating the length coefficient in step a is as follows:
step A1: establishing a multi-piece structural calculation simplified model as shown in fig. 3 and 4, wherein the structural calculation simplified model can be in the specific form of a straight rod member with equal sections, wherein the straight rod member is rigidly connected with a column base and comprises two layers of supports, and the axis of each layer of supports is uniformly pressed;
step A2: setting the lower part of the structural calculation simplified model component as an AB section and the upper part as a BC section, and respectively deriving buckling load equations of the AB section component and the BC section component;
step A3: substituting the corresponding parameters of each structural calculation simplified model component into the buckling load equations of the AB section component and the BC section component deduced in the step A2 respectively, and calculating the critical load of each structural calculation simplified model component when the AB section and the BC section are unstable; the specific critical load calculation method of the simplified model of each structure calculation comprises the following steps:
as shown in fig. 3 [ model 1 ]:
wherein the critical load of the AB section is,
the critical load of the BC-stage is,
as shown in fig. 4 [ model 2 ]:
wherein the critical load of the AB section is,
the critical load of the BC-stage is,
step A4: comparing the critical load values of the AB section and the BC section of the structure-calculated simplified model component in the step A3, determining a critical instability section and calculating the calculation length coefficient of the structure-calculated simplified model component, wherein the specific method comprises the following steps:
from the critical load calculation results of the model 1 shown in fig. 3 in the step a3, the two are compared
Model 1 is an AB stage instability,
further substituted into the formula
The calculated length coefficient u, which may result in [ model 1 ], is 0.451;
from the critical load calculation results of [ model 2 ] shown in fig. 4 in the step a3, the two are compared
Model 1 is AB stage instability
Further substituted into the formula
The calculated length coefficient u of [ model 2 ] can be found to be 0.433.
Further, the specific derivation process of the buckling load equations of the AB segment component and the BC segment component in the step a2 includes:
according to the displacement boundary conditions at the two ends of the BC section component, the bending line is set as a sine curve and satisfies the formula (1),
substituting the formula (1) into the formula (2) to deduce the strain energy,
the formula (1) is converted into a formula (3) to deduce the external force potential energy as follows,
further, the potential energy of the structural calculation simplified model is calculated according to the formula (4),
when the structural balance state is set, the formula (5) is satisfied,
further, the formula (6) can be derived,
converting the equation (6) to obtain a buckling load solving equation (7) of the BC section component,
according to the displacement boundary conditions at the two ends of the AB section component, the bending line equation is set to satisfy the formula (8),
y＝a1x2(l-x)+a2x3(l-x)+… (8)，
substituting the first two terms of the series of the formula (8) into the potential energy equation (9) of the structural calculation simplified model,
after the conversion, the formula (10) is obtained,
when the structural balance state is set, the following formula is satisfied,
further, the following formula (11) and formula (12) can be obtained by combining the above formula (10),
according to a1And a2Not all being zero, equation (13) can be derived,
the formula (14) can be obtained by further opening and sorting the formula (13),
the formula (15) obtained by solving the minimum root of the formula (14) is a buckling load solving equation of the AB section component,
wherein, the step B comprises the following steps:
step B1: simplifying an actual framework column into a uniform-section steel pipe column model according to an engineering actual model, wherein the steel pipe column model is, for example, a model with a steel pipe column interface phi 630 × 12(mm) and a height of 35 m;
step B2: screening various working condition simplified models according to the engineering model, and specifically establishing the following working condition models:
(1) as shown in fig. 5, the model is simplified under condition 1, and the concrete conditions are that the bottom is fixedly constrained, X, Z two-direction hinge constraints are arranged at 35m, and X, Z two-direction hinge constraints are arranged at 26 m;
(2) as shown in fig. 6, the model is simplified under condition 2, and the concrete conditions are that the bottom is fixedly constrained, X, Z hinge constraints in two directions are arranged at 35m, and Z hinge constraints are arranged at 26m and 20 m;
(3) as shown in fig. 7, the model is simplified under condition 3, and the concrete conditions are that the bottom is fixedly constrained, the total height of the steel pipe is modified to 26m, X, Z hinge constraints are arranged at the position of 26m, and an X hinge constraint is arranged at the position of 20 m;
(4) as shown in fig. 8, the simplified model under condition 4 has specific conditions that the bottom is fixedly constrained, X, Z two-direction hinge constraints are arranged at 35m, X, Z two-direction hinge constraints are arranged at 26m, and Z-direction hinge constraints are arranged at 20 m;
(5) as shown in fig. 9, the operating condition 5 simplifies the model, and the specific operating conditions are bottom fixed constraint, X, Z two-direction hinge constraint is set at 35m, X-direction hinge constraint is set at 26m, and Z-direction hinge constraint is set at 20 m.
Step B3: and respectively performing stability analysis on each working condition simplified model in the step B2, wherein the stability analysis comprises the following analysis processes:
(1) performing buckling analysis according to characteristic values of the conditions without introducing geometric nonlinearity and material nonlinearity, respectively applying unit axial force to the top of each working condition simplified model, calculating to obtain buckling modal parameters of the first 2 orders, further calculating to obtain instability loads without introducing double nonlinearity, substituting the instability loads into an Euler formula, and performing inverse calculation to obtain the calculated length coefficient of each working condition simplified model component;
(2) performing buckling analysis according to a characteristic value of a condition of introducing geometric nonlinearity, for example, introducing an initial defect (H/1200), calculating to obtain instability loads of all modes, obtaining a stability coefficient of each mode according to the instability loads, and further calculating to obtain a calculated length coefficient of each working condition simplified model component under the condition of introducing the geometric nonlinearity;
through the stability analysis in the step B3, a data analysis table as shown in table 1 can be output, wherein, the multi-column sub-curve of the axis pressing bar member is divided into four types, i.e., a, B, C and d, wherein the residual stress of the section a has the smallest influence on the stable bearing capacity of the structure, the stable bearing capacity is the highest and is closest to the calculation model, so the corresponding slenderness ratio is found out by adopting the steel structure design specification appendix C, namely the stability coefficient of the axis pressed member, and the section a, and the calculated length coefficient of each model member is obtained by inverse calculation.
TABLE 1 summary of second-order destabilizing loads and calculated length coefficients under various working conditions of equivalent model
Wherein, the at least one local model extracted in the step C is a peripheral structure model of the member in the screening simplified condition in the step B, which influences the calculated length coefficient of the member in the overall frame, and the model comprises a peripheral support structure model, specifically comprises local models 1, 2 and 3 of herringbone columns with supports at the periphery as shown in fig. 10, 11 and 12;
in addition, the calculation analysis dimensions of the local model in the step C include first order instability and second order instability, and further the critical load and the calculation length coefficient of each instability plane of each local model are calculated according to the situations of introducing no nonlinearity and introducing nonlinearity, respectively, and a data analysis table shown in table 2 can be output specifically.
TABLE 2 local model second order destabilization load and calculation length coefficient summary table
Wherein, in the step D, the specific implementation manner may be:
step D1: simplifying a test reduced-scale steel pipe column model by adopting components according to the actual engineering, wherein the interface of the steel pipe column is phi 60 x 5(mm), and the height of the steel pipe column is 3.5 m;
step D2: selecting at least one working condition from the screening simplified working conditions in the step B to establish a test model, which can be specifically the following test model:
(1) as shown in fig. 5, in the test model established under the working condition 1, the specific test conditions are that the cantilever column constrains the horizontal displacement in the X direction at 2.6m, constrains the horizontal displacement in the X direction at 3.5m, and is fixedly constrained at 0m of the bottom end;
(2) as shown in fig. 6, in the test model established under the working condition 2, the specific test conditions are that the cantilever column constrains the horizontal displacement in the X direction at 2.0m, constrains the horizontal displacement in the X direction at 3.5m, and is fixedly constrained at 0m of the bottom end;
step D3: and D2, performing grouping stability analysis and calculation on the test model, wherein the specific test requirement can be that under the load working condition that the axis is pressed, the form containing instability and instability limit load parameters in the plane of the reduced-scale steel pipe model are inspected, and the damage form and related data of the instability in the plane are obtained completely under the condition of support restraint.
The stability calculation of the test model in the step D3 includes the average value of the breaking load and the calculated length coefficient of each group of test members under the test requirement, and specifically, the step D3 can output the analysis data of each test model shown in tables 3 and 4 and further obtain the test conclusion.
TABLE 3-summary of packet stability analysis data for the test model set-up according to Condition 1
The test results obtained from table 3 above are: the third order is instability in a constraint plane, the X plane is instability, the critical load of the third order instability is 242.19kN, and the corresponding calculation length coefficient is 0.465;
TABLE 4-summary of packet stability analysis data for the test model based on Condition 2
The test results obtained from table 3 above are: the first order and the second order are out-of-constraint surface instability, the third order is in-constraint surface instability, the third order instability critical load is 264.6kN, and the corresponding calculated length coefficient is 0.432.
Wherein, the step E comprises the following comparison method for calculating the length coefficient:
(1) comparing and analyzing the calculation result of the structural calculation simplified model component calculated according to the step B with the test result of the test model calculated in the step D, wherein the analysis data comprises the calculation length coefficient value and the ratio of each instability plane of each model;
specifically, a comparative analysis data table 5, a table 6 and an analysis conclusion of the finite element scheme simplified model calculation results corresponding to the working condition 1 shown in fig. 5 and the working condition 2 shown in fig. 6 and the corresponding test model calculation results can be output;
TABLE 5 simplified model of finite element scheme and comparative table of data analysis of test model established according to working condition 1
| Working condition 1 | Critical load (kN) | Coefficient of stability | Calculating the length coefficient |
| Finite element calculation | 242.19 | 0.588 | 0.465 |
| Test model | 231.00 | 0.561 | 0.477 |
| Finite element/test | 1.096 | 1.048 | 0.975 |
TABLE 6 simplified model of finite element scheme and comparative table of data analysis of test model established according to working condition 1
It can be seen from tables 5 and 6 that the ratios of the finite element calculated length coefficients of working condition 1 and working condition 2 to the calculated length coefficients of the test are 0.975 and 1.03 respectively, and the calculated results are basically consistent, the error is small, and the error is within 5%, so that the calculation result of the finite element can be recommended to be corrected, and the calculated length coefficient is optimally adjusted to be 1.05.
(2) Comparing and analyzing the calculation result of the structural calculation simplified model component calculated according to the step B with the theoretical calculation result of the step A, wherein the analysis data comprises the calculation length coefficient values and the ratios of the calculation length coefficient values of the instability planes of the models;
specifically, a comparative analysis data table 7 of a finite element scheme simplified model calculation result corresponding to the working condition 5 without the pull rod and a theoretical calculation result as shown in fig. 9 and an analysis conclusion can be output;
TABLE 7-simplified model and comparison of theoretical calculation results Length coefficient based on finite element scheme without Tie rod Condition 5
| Plane of instability | X-Y | Z-Y |
| Model operating mode without tie rod | 0.422 | 0.416 |
| Theoretical calculation of | 0.451 | 0.433 |
| Without tie-rods/theoretical calculations | 0.936 | 0.960 |
It can be seen from the above comparison table 7 that the ratio of the calculated length coefficients of the simplified model of the 5-limited element scheme without the tie rod to the theoretically calculated two planes is 0.936 and 0.960, the calculation results of the two planes are basically consistent, and the error is within 5%, but the calculation result of the finite element scheme is unsafe in the whole view, and it is suggested to correct the calculated length coefficient output by the calculation result of the limited calculation element according to the calculation result, and the adjustment of the calculated length coefficient is 1.05 in comprehensive consideration.
(3) And C, comparing and analyzing the calculation result of the structural calculation simplified model component calculated according to the step B and the calculation result of the local model calculated according to the step C, wherein the analysis data comprises the calculation length coefficient values and the ratios of the calculation length coefficient values of the instability planes of the models, and the following comparison and analysis can be specifically carried out:
a) the finite element calculation result of the working condition 5 without the tie rod shown in fig. 9 is compared with the calculation result of the local model 1 with the periphery shown in fig. 10, and the comparison analysis result shown in table 8 can be output;
TABLE 8-comparison of Length coefficients calculated from simplified model and its local model 1 based on finite element solution without Tie rod Condition 5
| Plane of instability | Z-Y | X-Y |
| Model operating mode without tie rod | 0.422 | 0.416 |
| Local model 1 | 0.420 | 0.433 |
| Without tie-rods/partial moulds 1 | 1.004 | 0.96 |
From the above comparison table 8, it can be seen that the calculated length coefficient ratios of the two planes calculated without the tie rod model 5 and the local model 1 are 1.00 and 0.96, respectively;
b) the finite element calculation result of the working condition 3 without the tie rod shown in FIG. 7 is compared with the calculation result of the local model 3 with the periphery shown in FIG. 12, and the comparison analysis result shown in Table 9 can be output;
TABLE 9-comparison of calculated Length coefficients based on simplified model and its local model 3 for a finite element solution without Tie rod Condition 3
| Plane of instability | Z-Y | X-Y |
| Model working condition three without pull rod | 0.734 | 0.427 |
| Local model III | 0.7 | 0.46 |
| No tie rod/partial model III | 1.05 | 0.93 |
It can be seen from the above comparative table 9 that the calculated length coefficient ratios of the two planes calculated by the model 3 without the tie bar and the local model 3 are 1.05 and 0.93, respectively;
furthermore, according to the comparison result of the finite element model and the local model under each working condition, the ratio of the calculated length coefficient of the X-Y surface is respectively 1.004 and 1.05 which are both larger than 1.0, after the X-direction supporting condition is considered, the calculated length coefficient of the member is reduced, the stable bearing capacity is increased, the rigidity of the restraining member in the X direction can form strong restraint on the independent single steel pipe, and the calculated length coefficient of the X-Y of the steel pipe column calculated without lateral movement is safe and reliable; similarly, the ratio of the calculated length coefficients of the Z-Y plane is 0.96 and 0.93 respectively, after the supporting condition of the Z direction is considered, the calculated length coefficient of the component is increased, the stable bearing capacity is reduced, the influence of the rigidity of the constraint component in the Z direction on the independent single steel pipe cannot be ignored, and the calculated length coefficient of the steel pipe column in the Z-Y direction calculated without lateral movement is unsafe, so that adjustment according to the calculation and analysis result can be recommended, and the calculated length coefficient is adjusted to be 1.10.
Wherein, the step F comprises the following steps:
step F1: adjusting and optimizing the coefficient value of each calculated length according to the comparative analysis result in the step E;
step F2: performing statistical display of the recommended values of the calculated length coefficients according to the instability planes of the working condition models, as shown in the following table 10, so as to finally obtain the optimal calculated length coefficient value of the single steel tube structure adopted in the 500kV combined framework;
TABLE 10 summary of the calculated length coefficient recommended values for steel pipe columns
The method utilizes a plurality of modes including steel structure stability calculation theory modeling derivation, finite element scheme working condition model stability analysis, local model simulation influence parameter extraction calculation analysis, test model establishment and single steel pipe stability test construction to calculate the single steel pipe stability of the construction and analyze and compare the calculated length coefficient, obtains the more accurate calculated length coefficient meeting the single steel pipe column stability after further optimization, and realizes the optimal selection of single steel pipe column section consumables to the maximum extent while fully ensuring the structural safety, thereby saving the steel quantity, reducing the engineering cost and obviously improving the economic benefit.
Claims (9)
1. The method for determining the calculated length coefficient of the joint-frame single steel pipe is characterized in that the method is operated with the assistance of computer equipment and programs, and at least comprises the following steps:
step A: deducing a single steel pipe calculation length coefficient according to the steel structure stable calculation theoretical modeling;
and B: screening simplified working conditions according to the actual engineering model and analyzing the stability by using a finite element method;
and C: extracting a peripheral local model according to the influence factors, and deducing and calculating a length coefficient;
step D: simulating an actual working condition to establish a test model for carrying out a stability test of the framework single steel pipe;
step E: summarizing data and carrying out comparative analysis on each calculated length coefficient obtained in the steps A, B, C and D;
step F: and E, adjusting and determining a recommended value of the calculated length coefficient according to the analysis result obtained in the step E.
2. The method for determining the calculated length coefficient of the joint-frame single steel pipe according to claim 1, wherein the specific derivation manner of the calculated length coefficient in the step A is as follows:
step A1: establishing a plurality of structural calculation simplified models, wherein the specific form of the structural calculation simplified model can be a straight rod component with equal sections, the straight rod component is in rigid connection with a column base and comprises two layers of supports, and the axis of each layer of supports is uniformly pressed;
step A2: setting the lower part of the structural calculation simplified model component as an AB section and the upper part of the structural calculation simplified model component as a BC section, and respectively deriving buckling load equations of the AB section component and the BC section component;
step A3: respectively substituting the corresponding parameters of each structural calculation simplified model component into the buckling load equations of the AB section component and the BC section component deduced in the step A2, and calculating the critical load of each structural calculation simplified model component when the AB section and the BC section are unstable;
step A4: and C, comparing the critical load values of the AB section and the BC section of each structural calculation simplified model component in the step A3, determining a critical instability section and calculating the calculation length coefficient of each structural calculation simplified model component.
3. The method for determining the calculated length coefficient of the joint-frame single steel pipe according to claim 2, wherein the specific derivation process of the buckling load equations of the AB segment component and the BC segment component in the step a2 comprises:
according to the displacement boundary conditions at the two ends of the BC section component, the deflection line is set as a sine curve and satisfies the formula (1),
substituting the formula (1) into the formula (2) to deduce strain energy,
the formula (1) is converted into a formula (3) to deduce external force potential energy,
further, the potential energy of the structural calculation simplified model is calculated according to the formula (4),
when the structural balance state is set, the formula (5) is satisfied,
further, the formula (6) can be derived,
converting the formula (6) to obtain a buckling load solving equation (7) of the BC section component,
according to the displacement boundary conditions at the two ends of the AB section component, the bending line equation of the AB section component is set to satisfy the formula (8),
y＝a1x2(l-x)+a2x3(l-x)+… (8)，
substituting the first two terms of the series of the formula (8) into a potential energy equation (9) of the structural calculation simplified model,
after the conversion, the formula (10) is obtained,
when the structural balance state is set, the following formula is satisfied,
further, the following formula (11) and formula (12) can be obtained by combining the formula (10) and arranging,
according to a1And a2Not all being zero, equation (13) can be derived,
the formula (14) can be obtained by carrying out the sorting calculation again on the formula (13),
obtaining a formula (15) for the minimum root solved by the formula (14), namely solving an equation for the buckling load of the AB section component,
4. the method for determining the calculated length factor of the joint-frame single steel pipe according to claim 1, wherein the step B comprises the steps of:
step B1: simplifying the actual framework column into a uniform-section steel pipe column model according to the engineering actual model;
step B2: screening out various working condition simplified models according to the engineering model;
step B3: and respectively performing stability analysis on each working condition simplified model in the step B2, wherein the stability analysis comprises the following analysis processes:
(1) performing buckling analysis according to characteristic values of the conditions without introducing geometric nonlinearity and material nonlinearity, respectively applying unit axial force to the top of each working condition simplified model, calculating to obtain buckling modal parameters of the first 2 orders, further calculating to obtain instability load without introducing double nonlinearity, substituting the instability load into an Euler formula, and performing inverse calculation to obtain a calculated length coefficient of each working condition simplified model component;
(2) and carrying out buckling analysis according to the characteristic value of the introduced geometric nonlinearity, calculating to obtain instability loads of all the modes, obtaining a stability coefficient of each mode according to the instability loads, and further calculating to obtain a calculated length coefficient of each working condition simplified model component under the introduced geometric nonlinearity.
5. The method for determining the calculated length coefficient of the joint-frame single steel pipe according to claim 1, wherein:
the at least one local model extracted in the step C is a peripheral structure model of the member in the screening simplified working condition in the step B, which influences the calculated length coefficient of the member in the whole frame, and comprises a peripheral support structure model;
and C, calculating and analyzing dimensions of the local models in the step C, wherein the dimensions comprise first-order instability and second-order instability, and further calculating critical load and calculating length coefficient of each instability plane of each local model according to the situations of introducing no nonlinearity and introducing nonlinearity.
6. The method for determining the calculated length coefficient of the joint-frame single steel pipe according to claim 1, wherein the specific implementation manner of the step D is as follows:
step D1: simplifying a test reduced-scale steel pipe column model according to actually adopted components of the project;
step D2: selecting at least one working condition from the screened simplified working conditions in the step B to establish a test model;
step D3: a grouping stability analysis calculation is performed for the test model in step D2.
7. The method for determining the calculated length coefficient of the joint-frame single steel pipe according to claim 6, wherein:
the stability calculation of the test model in step D3 includes the average of the breaking load and the calculated length factor for each set of test members under test requirements.
8. The method for determining the calculated length coefficient of the joint-frame single steel pipe according to claim 1, wherein the step E comprises the following comparison method for calculating the length coefficient:
(1) comparing and analyzing the calculation result of the structural calculation simplified model component calculated according to the step B with the test result of the test model calculated in the step D, wherein the analysis data comprises the calculation length coefficient value and the ratio of each instability plane of each model;
(2) comparing and analyzing the calculation result of the structural calculation simplified model member calculated according to the step B with the theoretical calculation result of the step A, wherein the analysis data comprises the calculation length coefficient value and the ratio of each instability plane of each model;
(3) and C, comparing and analyzing the calculation result of the structural calculation simplified model member calculated according to the step B with the calculation result of the local model calculated according to the step C, wherein the analysis data comprises the calculation length coefficient value and the ratio of the calculation length coefficient value to the calculation length coefficient value of each instability plane of each model.
9. The method for determining the calculated length factor of the joint-frame single steel pipe according to claim 1, wherein the step F comprises the steps of:
step F1: adjusting and optimizing the coefficient value of each calculated length according to the comparative analysis result in the step E;
step F2: and performing statistical display of the recommended value of each calculated length coefficient according to each instability plane of each working condition model.
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| CN117057023A (en) * | 2023-10-10 | 2023-11-14 | 中国农业大学 | Unified calculation length determining method for space steel structural members |
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