CN109165447B - Method and system for evaluating wall thickness loss of space steel pipe structure - Google Patents
Method and system for evaluating wall thickness loss of space steel pipe structure Download PDFInfo
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Abstract
The invention discloses a method and a system for evaluating wall thickness loss of a space steel pipe structure, wherein the method comprises the following steps: monitoring geometric physical parameters of the steel pipe structure; determining a rigidity matrix of the steel pipe unit under a local coordinate system; analyzing the corresponding relation between the steel pipe unit physical parameters and the unit stiffness matrix, and expressing the stiffness matrix as the combination of the rod member section area and the section inertia moment; establishing the sensitivity of the cross section area of the steel pipe unit to the wall thickness loss; establishing sensitivity of the section inertia moment of the steel pipe unit to wall thickness loss; establishing the sensitivity of the steel pipe unit rigidity to the wall thickness loss under the integral coordinate system; 7) Establishing the sensitivity of the overall structure to wall thickness loss; 8) And establishing a steel pipe structure frequency change analysis and evaluation method caused by wall thickness loss, and analyzing and calculating dynamic characteristic change caused by the structural wall thickness loss. The invention skillfully converts the influence of the wall thickness loss on the structure into the influence on the section area and the inertia moment of the steel pipe unit by utilizing the structural dynamic modification principle.
Description
Technical Field
The invention relates to a space steel structure performance evaluation technology, in particular to a method and a system for evaluating wall thickness loss of a space steel pipe structure.
Background
The space structure is a typical civil infrastructure, and has been widely used in recent years due to the advantages of light dead weight, large span, flexible indoor arrangement, high building area utilization rate and the like. Over the years of development, space steel structures have been formed into various structural forms to meet different building and structural needs. The space steel pipe structure mainly adopts steel pipe members as main bearing force members, and is therefore the main form of the steel structure. The actual space steel structure is in service in the field for a long time and is subjected to the continuous action of environments and load effects such as corrosion, high temperature, strong wind and strong shock, and the like, so that damage accumulation and even failure damage are easily caused. In recent years, many space steel structure damage accidents occur at home and abroad, which causes serious economic loss and secondary disasters. Therefore, the performance analysis and safety evaluation under the service environment of the space steel structure have important practical significance.
The steel pipe structure is in service in a natural environment for a long time, and the section loss of the rod piece is inevitably caused by the corrosion action of a severe environment. The loss of the rod section will result in a reduction in the cross-sectional area of the steel tube rod and a reduction in the section moment of inertia. It inevitably leads to a reduction in the rigidity of the rod unit, and further, to a reduction in the rigidity of the overall structure. The dynamic characteristic of the structure is an important index of the service performance of the reaction structure under the action of dynamic load, and the dynamic characteristic is directly related to the rigidity of the structure. Therefore, the reduction in structural rigidity inevitably affects the dynamic characteristics of the overall structure. In recent years, with the rapid development of numerical calculation technology, the static and dynamic analysis of the space steel pipe structure is rapidly developed, and a nonlinear finite element method can be adopted for analysis and calculation. At present, finite element analysis software with powerful functions, such as ABAQUS, ANSYS and the like, can be used for calculating the dynamic response and the dynamic characteristic of the space steel pipe structure. However, in the finite element analysis and calculation process of the current space steel structure, the influence of the wall thickness loss of different rod pieces in the structure on the rigidity of the structure cannot be effectively considered, and the difference of the reduction influence of the wall thickness loss of different rod pieces on the structural rigidity cannot be quantitatively judged. In addition, the conventional method cannot quickly and accurately evaluate the influence rule of the wall thickness loss on the dynamic characteristics. In general, the method for evaluating the wall thickness loss of the space steel pipe structure is very insufficient, and a lot of work needs to be carried out. At present, the work of the method is still blank, and no relevant report exists on an evaluation method and system for the wall thickness loss of the space steel pipe structure.
Therefore, it is necessary to systematically study the characteristics of the wall thickness loss of the rod in the space steel tube structure in the severe service environment, and it is necessary to establish a method and a system for evaluating the wall thickness loss of the space steel tube structure. On the premise of ensuring the analysis precision, the workload of finite element modeling and service performance evaluation is reduced rapidly and effectively, so that the bearing capacity calculation efficiency and the analysis level of the space steel pipe structure can be improved effectively, and the analysis and evaluation level of the large space steel pipe structure is improved.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method and a system for evaluating the wall thickness loss of a space steel pipe structure aiming at the defects in the prior art.
The technical scheme adopted by the invention for solving the technical problem is as follows: a method for evaluating wall thickness loss of a space steel pipe structure comprises the following steps:
1) Monitoring geometric and physical parameters of the steel pipe structure: determining physical parameters of the steel pipe unit in the structure, including node information, rod piece connection information, rod piece length L and rod piece inner diameter r in Outer diameter r of rod member out Geometric information including wall thickness t and elastic modulus;
2) Determining rigidity matrix of steel pipe unit under local coordinate system
The local coordinate system of the steel pipe unit takes the central point of the section of one end of the steel pipe as an O point, the axial direction is an x axis, the radial direction is a y axis, and the vertical direction is a z axis;
3) Analyzing the corresponding relation between the steel pipe unit physical parameters and the unit stiffness matrix, and analyzing the stiffness matrix
Expressed as a combination of rod section area and section moment of inertia;
4) According to a stiffness matrix
The relation between the cross-sectional area and the wall thickness establishes the sensitivity of the cross-sectional area of the steel pipe unit to the wall thickness loss
5) According to a stiffness matrix
The relation between the section moment of inertia and the wall thickness establishes the sensitivity of the section moment of inertia of the steel pipe unit to the wall thickness loss
And
6) According to the sensitivity of the cross-sectional area of the steel pipe unit to the wall thickness loss and the sensitivity of the cross-sectional inertia moment of the steel pipe unit to the wall thickness loss, the sensitivity of the rigidity of the steel pipe unit to the wall thickness loss under an integral coordinate system is established
7) According to the sensitivity of the steel pipe unit rigidity to the wall thickness loss in the global coordinate system, all steel pipe unit rigidity matrixes are superposed in the global coordinate system, and the sensitivity of the global structure to the wall thickness loss is established
8) Establishing a steel pipe structure frequency change analysis and evaluation method caused by wall thickness loss, and analyzing and calculating dynamic characteristic change delta f caused by the wall thickness loss of the structure r 。
According to the scheme, in the step 3), the rigidity matrix is formed
Is shown asThe combination of the section area and the moment of inertia of the rod piece is as follows:
in the formula:
wherein: a. The i The sectional area of the ith steel pipe unit under a local coordinate system;
in the formula: r is a radical of hydrogen i,in And r i,out The inner radius and the outer radius of the ith steel pipe unit are respectively set;
and
the inertia moments of the ith steel pipe unit in the x direction, the y direction and the z direction are respectively.
According to the scheme, in the step 5), the formula of the sensitivity of the section moment of inertia of the steel pipe unit to the wall thickness loss is represented as follows:
according to the scheme, in the step 6), the formula of the sensitivity of the steel pipe unit rigidity to the wall thickness loss in the overall coordinate system is represented as follows:
according to the scheme, in the step 7), the formula of the sensitivity of the integral structure to the wall thickness loss is expressed as follows:
according to the scheme, in the step 8), the power characteristic change delta f r Is expressed as follows:
the invention also provides a system for evaluating the wall thickness loss of the space steel pipe structure, which comprises the following components:
the steel pipe structure geometric and physical parameter monitoring module is used for determining geometric information such as node information, rod piece connecting information, rod piece length, rod piece radius, wall thickness and the like in the structure, material parameters such as elastic modulus and the like;
the steel pipe unit physical parameter and unit stiffness matrix corresponding relation analysis module is used for representing a stiffness matrix as a combination of the section area of the rod piece and the inertia moment;
the sensitivity determination module of the sectional area of the steel pipe unit to the wall thickness loss is used for analyzing and calculating the sectional area change of the single steel pipe unit after the wall thickness loss occurs, and further analyzing and calculating the sensitivity of the sectional area to the wall thickness loss;
the sensitivity determination module of the steel pipe unit section moment of inertia to the wall thickness loss is used for analyzing and calculating the section moment of inertia change of a single steel pipe unit after the wall thickness loss occurs, and further analyzing and calculating the sensitivity of the section moment of inertia to the wall thickness loss;
the sensitivity determination module of the steel pipe unit rigidity to the wall thickness loss under the integral coordinate system is used for analyzing the sensitivity of the steel pipe unit rigidity to the wall thickness loss according to the influence of the change of the cross-sectional area and the inertia moment on the unit rigidity;
the sensitivity of the integral structure to the wall thickness loss is determined by a module, firstly, a steel pipe structure integral rigidity matrix under an integral coordinate system is formed, and then the sensitivity of the wall thickness loss of a single steel pipe unit to a certain order frequency of the integral structure is established;
and the steel pipe structure frequency change analysis and evaluation module is used for establishing a steel pipe structure frequency change analysis and evaluation method caused by wall thickness loss and analyzing and calculating dynamic characteristic change caused by the structural wall thickness loss.
The invention has the following beneficial effects:
1. the method for evaluating the wall thickness loss of the space steel pipe structure has the advantages of clear concept and accurate analysis and calculation. The analysis method and the system have applicability, and are suitable for analyzing and evaluating the wall thickness loss of the space steel pipe structure with different spans, heights and physical parameters.
2. The current common method is to adopt a finite element method to analyze and calculate the static and dynamic performance of the space steel pipe structure. However, since the spatial steel tube structure is composed of a plurality of rods, in the analysis process, accurate finite element models must be respectively established for a single rod, then the wall thickness loss of each rod is considered respectively, and the dynamic performance analysis and calculation are performed one by one, so that the analysis process is very complicated and complex, the practicability is not strong, and from the practical operation perspective, especially for a large spatial steel tube structure with numerous rods, a fine finite element analysis model cannot be established for each rod at all and the wall thickness loss of the large spatial steel tube structure can not be analyzed and evaluated. The invention provides a method for evaluating the wall thickness loss of a space steel pipe structure, which utilizes the structural dynamic modification principle and establishes the corresponding relation between the physical parameters of steel pipe units and a unit stiffness matrix to express the stiffness matrix as the combination of the section area and the inertia moment of a rod piece. The influence of the wall thickness loss on the structure is ingeniously converted into the influence on the section area and the inertia moment of the steel pipe unit.
3. The invention innovatively establishes a method for analyzing the sensitivity of the cross-sectional area and the cross-sectional moment of inertia of the steel pipe unit to the wall thickness loss. The sensitivity of the steel pipe unit rigidity to the wall thickness loss and the sensitivity of the integral structure rigidity to the wall thickness loss under an integral coordinate system are established. On the basis, an analysis and evaluation method for the frequency change of the steel pipe structure caused by the wall thickness loss is established. By the method, the sensitivity of the wall thickness loss of the steel pipe unit is analyzed, and the influence of the wall thickness loss on the service performance of the structure is evaluated.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a flow chart of a method of an embodiment of the present invention;
FIG. 2 is an isometric view and an elevation view of a space steel pipe structure according to an embodiment of the present invention;
FIG. 3 is a schematic view of a local coordinate system of a steel pipe unit according to an embodiment of the present invention;
FIG. 4 is a schematic representation of the wall thickness loss of a steel pipe unit of an embodiment of the present invention as a function of age;
FIG. 5 is a schematic diagram showing the influence of the wall thickness loss of the steel pipe unit on the first 5 th order frequency of the structure according to the embodiment of the present invention;
FIG. 6 is a graph illustrating the effect of sustained cross-sectional loss of the structure of an embodiment of the present invention over different years on the first 5 th order frequency.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in FIG. 1, the method for evaluating the wall thickness loss of the space steel pipe structure comprises the following steps:
the method comprises the following steps: determining geometric information and elastic modulus of each node information, rod piece connection information, rod piece length, rod piece radius, wall thickness and the like in the steel pipe structure, and establishing a rigidity matrix under a local coordinate system of the steel pipe unit;
FIG. 3 shows a local coordinate system O-XYZ of the steel pipe unit.The space coordinates of two nodes 1 and 2 at two ends of the steel pipe unit are respectively as follows: (x) 1 ,y 1 ,z 1 )、(x 2 ,y 2 ,z 2 ). The steel pipe unit of the space steel structure can be simulated by adopting a three-dimensional space beam unit, and each node has three translational degrees of freedom and three rotational degrees of freedom. The corresponding node displacement is then expressed as: (u) 1 ,v 1 ,w 1 ,θ x1 ,θ y1 ,θ z1 )、(u 2 ,v 2 ,w 2 ,θ x2 ,θ y2 ,θ z2 ). Node displacement vector under local coordinate system
Vector of sum force
Can be expressed as:
the stiffness matrix and the mass matrix of the ith steel pipe unit under the local coordinate system can be expressed as follows:
in the formula: rho i Is the material density of the ith cell; b is i A strain-displacement matrix of the ith cell; h i Is the shape function of the ith unit; d i A material matrix of the ith cell; v is the integration area of the ith cell. Based on Euler-Bernoulli beam unit theory, steel is in local coordinate systemStiffness matrix of tube units
Can be expressed as:
step two: establishing the corresponding relation between the physical parameters of the steel pipe units and the rigidity matrix
Stiffness matrix of on-beam unit
In the middle, the physical parameters related to the wall thickness of the steel pipe are mainly the cross-sectional area and the inertia moment in each direction:
therefore, the stiffness matrix of the ith steel pipe unit in the local coordinate system can be expressed as the cross-sectional area A i Moment of inertia in each direction
And
linear combination of (a):
in the formula:
step three: establishing sensitivity of steel pipe unit cross-sectional area to wall thickness loss
The steel pipe unit is in service for a long time in severe environments such as corrosion, the section area of the steel pipe unit is gradually reduced, and the static and dynamic performance of the whole structure is degraded. Thus, the effect of cross-sectional area loss on structural performance can be evaluated by dynamic modification techniques. The reduction of the wall thickness of the steel pipe unit will cause the cross-sectional area A thereof i Is reduced. The cross-sectional area of the steel pipe unit may be expressed as:
in the formula: r is i,in And r i,out The inner radius and the outer radius of the ith steel pipe unit respectively.
Cross-sectional area versus wall thickness of steel pipe
The sensitivity of (a) can be expressed as:
step four: sensitivity of building steel pipe unit cross-section inertia moment to wall thickness loss
Wall thickness of steel pipe unit
Will cause its section moment of inertia to decrease
And
is reduced.
Cross-sectional inertia moment of steel pipe in different directions to wall thickness
The sensitivities of (a) can be expressed as:
therefore, the sectional moment of inertia is related to the wall thickness of the steel pipe
The sensitivity of (d) can be expressed as:
step five: sensitivity of steel pipe unit rigidity to wall thickness loss under integral coordinate system is established
Rigidity of ith steel pipe unit to wall thickness under local coordinate system
The sensitivity of (d) can be expressed as:
further, the rigidity to the wall thickness of the ith steel pipe unit under a local coordinate system can be established
The calculation formula of (2):
using coordinate transformation matrices
The unit rigidity matrix under the local coordinate system can be formed
Converting the unit stiffness matrix K into a whole coordinate system i ：
Therefore, a unit stiffness matrix K under the global coordinate system can be established i Wall thickness of
The sensitivity calculation formula of (c):
step six: establishing sensitivity of monolithic structures to wall thickness loss
By superposing all steel pipe unit rigidity matrixes under the overall coordinate system, the overall rigidity matrix K of the steel pipe structure can be established:
in the formula: ne is the number of all rod pieces in the steel tube structure.
The characteristic equation of the r-th order vibration mode of the structural whole body can be expressed as follows:
in the formula: m and K are respectively a mass matrix and a rigidity matrix of an integral structure omega r And phi r Respectively, the frequency and the vibration mode vector of the r stage of the integral structure.
The sensitivity of solving the characteristic equation to the ith steel pipe unit can be obtained as follows:
considering that the mass matrix and the rigidity matrix of the integral structure are symmetric matrixes and considering that the vibration mode vector and the mass matrix M meet the normalization condition, the sensitivity of the ith unit wall thickness loss of the steel pipe structure to the r-order frequency can be obtained:
considering that the overall stiffness matrix of the structure is a combination of the stiffness matrices of the individual units, the sensitivity of the i-th unit wall thickness loss of the steel pipe structure to its r-th order frequency can be expressed as:
step seven: method for establishing frequency change analysis of steel pipe structure caused by wall thickness loss
Determining the outer wall loss of the rod piece caused by the bad service environment
The resulting ensemble can then be determinedFrequency variation of the structure:
since there are several rods in the structure that suffer from wall thickness loss, the effects of different rods can be superimposed to determine the effect of all rod wall thickness loss on the frequency of the overall structure:
in the formula: nm is the number of rods in the steel pipe structure where wall thickness loss occurs due to environmental deterioration.
A method and a system for evaluating wall thickness loss of a space steel pipe structure are characterized by comprising the following steps:
the steel pipe structure geometric and physical parameter monitoring module is used for determining geometric information such as node information, rod piece connecting information, rod piece length, rod piece radius, wall thickness and the like in the structure, material parameters such as elastic modulus and the like;
the steel pipe unit physical parameter and unit stiffness matrix corresponding relation analysis module is used for representing a stiffness matrix as a combination of the section area of the rod piece and the inertia moment;
the sensitivity module of the sectional area of the steel pipe unit to the wall thickness loss is used for analyzing and calculating the sectional area change of the single steel pipe unit after the wall thickness loss occurs, and further analyzing and calculating the sensitivity of the sectional area to the wall thickness loss;
the sensitivity module of the steel pipe unit section moment of inertia to the wall thickness loss is used for analyzing and calculating the section moment of inertia change of a single steel pipe unit after the wall thickness loss occurs, and further analyzing and calculating the sensitivity of the section moment of inertia to the wall thickness loss;
the sensitivity analysis module of the steel pipe unit rigidity to the wall thickness loss under the integral coordinate system is used for collecting the influence of the cross-sectional area and the inertia moment change on the unit rigidity and analyzing the sensitivity of the steel pipe unit rigidity to the wall thickness loss;
the sensitivity analysis module of the overall structure to the wall thickness loss firstly forms a steel pipe structure overall stiffness matrix under an overall coordinate system, and then establishes the sensitivity of the wall thickness loss of a single steel pipe unit to a certain order frequency of the overall structure;
and the steel pipe structure frequency change analysis and evaluation module is used for establishing a steel pipe structure frequency change analysis and evaluation method caused by wall thickness loss and analyzing and calculating dynamic characteristic change caused by the structural wall thickness loss.
The concrete implementation process of the patent is described in the following case of actual space steel pipe structure:
the span of the steel pipe latticed shell structure in a certain space is 50 meters, the height of the steel pipe latticed shell structure is 8 meters, and 500 steel pipe rod piece units are totally arranged. The elastic modulus of the rod material is 2.01 multiplied by 10 11 Pa, material density of 7800kg/m 3 The Poisson's ratio was 0.28. The outer radius of the steel pipe unit is 180mm, and the cross-sectional area is 0.002749m 2 . The inner radius of the steel pipe unit is 159mm, and the cross-sectional area is 0.002419m 2 . The steel pipe unit is made of Q235 steel, and the yield strength of the steel pipe unit is 235MPa. Because the space steel pipe structure is in service for years, part of the rod pieces have certain wall thickness loss, and the rod pieces with the wall thickness loss after inspection account for half of the number of all the rod pieces. Fig. 2 is an axonometric view and an elevation view of the space steel pipe structure. First, a local coordinate system of the steel pipe unit is established as shown in fig. 3, wherein the direction along the length of the rod member is the X direction, and the two orthogonal directions along the cross section of the rod member are the Y direction and the Z direction, respectively.
Firstly, writing a computer program according to a formula (5) to determine a rigidity matrix of the steel pipe unit under a local coordinate system
Writing a computer program to apply the stiffness matrix according to equations (6) and (7)
Expressed as a combination of rod cross-sectional area and moment of inertia;
writing a computer program according to the formula (15) to determine the sensitivity of the cross section area of the steel pipe unit to the wall thickness loss
Writing a computer program according to the formulas (23), (25) and (27) to determine the sensitivity of the section moment of inertia of the steel pipe unit to the wall thickness loss
And
writing a computer program according to the formula (31) to determine the sensitivity of the steel pipe unit stiffness to wall thickness loss in a coordinate system
Writing a computer program to determine the sensitivity of the overall structure to wall thickness loss according to equation (37)
Writing a computer program according to equation (39) to determine the dynamic property change Δ f due to structural wall thickness loss r 。
FIG. 4 shows the wall thickness loss of a steel pipe unit as a function of service life, values which can be obtained by field measurements of the structure. FIG. 5 shows the effect of different units on the first 5 th order frequency of the structure after a loss of wall thickness occurs in the steel pipe unit. Fig. 6 shows the effect on the first 5 order frequency of a structure after sustained cross-sectional loss for different years.
The analysis result shows that: (1) The wall thickness loss of the units at different positions of the structure occurs, and the influence on the rigidity of the structure is greatly different; (2) The radial rod member (rm) along the radius direction of the structure generally has larger wall thickness loss sensitivity, and the main reason is that the radial rod member is the main stressed member of the structure, so the rigidity of the radial rod member has larger influence on the whole frequency of the structure; (3) The circumferential rod pieces (cm) in the circumferential direction of the structure have smaller wall thickness loss sensitivity, wherein the wall thickness loss sensitivity of the inner layer circumferential rod pieces (cm 1, cm2 and cm 3) close to the center of the structure is obviously greater than that of the outer layer circumferential rod pieces (cm 4, cm5 and cm 6); (4) The oblique units (sm) oblique to the structure have larger wall thickness loss sensitivity, wherein the wall thickness loss sensitivity of the inner layer oblique units (sm 1, sm2, sm 3) close to the center of the structure is obviously larger than that of the outer layer oblique units (sm 4, sm5, sm 6); (5) With the increase of the service time of the structure, the wall thickness loss of the structure under the action of a severe environment is gradually increased, which causes the rigidity of the whole structure to be gradually reduced. Therefore, it also leads to a gradual reduction of the overall frequency of the structure, resulting in a degradation of the service performance of the structure. (6) The evaluation method provided by the invention has high precision and completely meets the requirements of actual engineering analysis; (7) The equivalent analysis method provided by the invention has the advantages of wide application range, small calculation workload, high analysis precision, quick calculation and the like.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (7)
1. The method for evaluating the wall thickness loss of the space steel pipe structure is characterized by comprising the following steps of:
1) Monitoring geometric physical parameters of the steel pipe structure: determining physical parameters of the steel pipe unit in the structure, including node information, rod piece connection information, rod piece length L and rod piece inner diameter r in Outer diameter r of rod member out Geometric information including wall thickness t and elastic modulus;
2) Determining rigidity matrix of steel pipe unit under local coordinate system
The local coordinate system of the steel pipe unit takes the central point of the section of one end of the steel pipe as an O point, the axial direction is an x axis, the radial direction is a y axis, and the vertical direction is a z axis;
3) Analyzing the corresponding relation between the steel pipe unit physical parameters and the unit stiffness matrix, and analyzing the stiffness matrix
Expressed as a combination of rod cross-sectional area and cross-sectional moment of inertia;
4) According to a stiffness matrix
The relation between the cross-sectional area and the wall thickness establishes the sensitivity of the cross-sectional area of the steel pipe unit to the wall thickness loss
5) According to a stiffness matrix
The relation between the section moment of inertia and the wall thickness establishes the sensitivity of the section moment of inertia of the steel pipe unit to the wall thickness loss
And
6) According to the sensitivity of the cross-sectional area of the steel pipe unit to the wall thickness loss and the sensitivity of the cross-sectional inertia moment of the steel pipe unit to the wall thickness loss, the sensitivity of the rigidity of the steel pipe unit to the wall thickness loss under an integral coordinate system is established
7) According to the sensitivity of the steel pipe unit rigidity to the wall thickness loss under the integral coordinate system, overlapping under the integral coordinate systemAdding all steel pipe unit rigidity matrixes to establish sensitivity of the integral structure to wall thickness loss
8) Establishing a steel pipe structure frequency change analysis and evaluation method caused by wall thickness loss, and analyzing and calculating dynamic characteristic change delta f caused by the wall thickness loss of the structure r 。
2. The method for evaluating the wall thickness loss of the spatial steel tube structure according to claim 1, wherein the rigidity matrix is used in the step 3)
Expressed as a combination of the rod cross-sectional area and the moment of inertia, as follows:
in the formula:
wherein: a. The i The sectional area of the ith steel pipe unit under a local coordinate system;
in the formula: r is i,in And r i,out Respectively setting the inner radius and the outer radius of the ith steel pipe unit;
and
are respectively the firstThe inertia moments of the i steel pipe units in the x, y and z directions.
3. The method for evaluating the wall thickness loss of a space steel pipe structure according to claim 1, wherein in the step 5), the formula of the sensitivity of the steel pipe unit section moment of inertia to the wall thickness loss is expressed as follows:
4. the method for evaluating the wall thickness loss of a space steel tube structure according to claim 1, wherein in the step 6), the formula of the sensitivity of the stiffness of the steel tube unit to the wall thickness loss in the global coordinate system is represented as follows:
5. the method for evaluating the wall thickness loss of a space steel pipe structure according to claim 1, wherein in the step 7), the formula of the sensitivity of the overall structure to the wall thickness loss is expressed as follows:
6. the space steel tube joint of claim 1The method for evaluating the structural wall thickness loss, wherein in the step 8), the dynamic characteristic change Δ f r Is expressed as follows:
7. a system for evaluating the wall thickness loss of a space steel tube structure is characterized by comprising:
the steel pipe structure geometric physical parameter monitoring module is used for determining the physical parameters of the steel pipe units in the structure, including the geometric information and the elastic modulus of each node information, the rod piece connection information, the rod piece length, the rod piece inner diameter, the rod piece outer diameter and the wall thickness;
the steel pipe unit physical parameter and unit stiffness matrix corresponding relation analysis module is used for representing a stiffness matrix as a combination of the section area of the rod piece and the inertia moment;
the sensitivity determination module of the sectional area of the steel pipe unit to the wall thickness loss is used for analyzing and calculating the sectional area change of the single steel pipe unit after the wall thickness loss occurs, and further analyzing and calculating the sensitivity of the sectional area to the wall thickness loss;
the sensitivity determination module of the steel pipe unit section moment of inertia to the wall thickness loss is used for analyzing and calculating the section moment of inertia change of a single steel pipe unit after the wall thickness loss occurs, and further analyzing and calculating the sensitivity of the section moment of inertia to the wall thickness loss;
the sensitivity determination module of the steel pipe unit rigidity to the wall thickness loss under the integral coordinate system is used for analyzing the sensitivity of the steel pipe unit rigidity to the wall thickness loss according to the influence of the change of the cross-sectional area and the inertia moment on the unit rigidity;
the method comprises the steps that a sensitivity determination module of the overall structure to wall thickness loss firstly forms a steel pipe structure overall stiffness matrix under an overall coordinate system, and then establishes the sensitivity of the wall thickness loss of a single steel pipe unit to a certain order frequency of the overall structure;
and the steel pipe structure frequency change analysis and evaluation module is used for establishing a steel pipe structure frequency change analysis and evaluation method caused by wall thickness loss and analyzing and calculating dynamic characteristic change caused by the structural wall thickness loss.
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