Single-layer latticed shell structure damage identification method and system based on direct analysis method

Abstract

The invention discloses a single-layer latticed shell structure damage identification method and system based on a direct analysis method, and the method comprises the steps: S1, constructing a numerical model according to the numerical value of a latticed shell structure, taking a key member of the latticed shell as a unit, analyzing and determining a distribution position, and preliminarily arranging a monitoring sensor measurement point for each unit; s2, updating a numerical model according to the monitoring data, performing construction analysis on each unit, determining deformation and residual construction stress, performing importance sorting on key components of the latticed shell again, and optimizing a measuring point arrangement scheme; s3, acquiring response data of each unit of the reticulated shell structure by using a monitoring sensor; s4, calculating unit unbalance force under the current reticulated shell configuration according to the response data, and calculating a structural stiffness matrix and a change matrix thereof; and S5, analyzing the change condition of the damage area by using the damage index and the structural stiffness matrix, and obtaining the damage condition of the reticulated shell key component. The structural member damage and the damage degree are accurately identified through the rigidity damage index.

Description

Technical Field

[0001] The present invention belongs to the technical field of architectural engineering design, and in particular relates to a single-layer lattice shell structure damage identification method and system based on direct analysis method. Background Art

[0002] With the development of aesthetic level, the shape and structure of single-layer lattice shells are becoming more and more novel. Due to the prominent nonlinear behavior of single-layer lattice shells and the complex interaction mechanism between components, the traditional structural analysis and design method based on empirical coefficients has certain problems in the stress analysis of modern lattice shells. The existing methods most commonly use frequency domain analysis, time domain analysis and finite element model correction methods to evaluate the location of structural damage. The frequency domain method is greatly affected by environmental factors and requires the deployment of a large number of sensors, which requires a large amount of data processing. Some damage signals in the time domain method may be masked by signals with large amplitudes that are not related to damage. The finite element model correction method is to obtain a finite element model that matches the test data, and based on this, conduct damage and retrograde evaluation of the model, which can more clearly locate and quantify the damage. With the development of digital twin technology, this method is gradually being widely used in damage identification, but the current finite element model update theory and technology are imperfect. In order to ensure efficiency, many methods use the results obtained from eigenvalue buckling analysis to evaluate and correct the model. There is a problem that the model force is inconsistent with the actual state of the lattice shell, which will lead to the generation of localized deformation of the model, and it is impossible to accurately locate the damaged components and quantitatively evaluate the degree of damage, which restricts the operation and maintenance of the lattice shell.

[0003] The direct analysis method for steel structures is an emerging integrated method for structural analysis and design. It obtains the true mechanical state of the structure by directly considering the influence of structural defects and node stiffness in nonlinear analysis, and directly judges the bearing capacity of the rod based on the internal force of the component without the need for stability verification through empirical coefficients. The method has high analysis efficiency and more accurate judgment of the stress state of the structure. Its core is to propose a reasonable overall structural defect model and high-performance analysis unit, and realize an efficient simulation method that directly considers rod defects and node stiffness in the unit stiffness matrix. However, the current difficulty in applying the direct analysis method in structural damage identification lies mainly in how to reliably update the numerical analysis model data and determine the structural damage index to effectively evaluate the current state of the structure. Summary of the invention

[0004] The main purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a single-layer lattice shell structure damage identification method and system based on direct analysis method. By considering the relationship between external load and actual bearing capacity of the structure, the change of the overall stiffness matrix of the structure is obtained through nonlinear iteration, and the stiffness change of the nodes and corresponding components is further obtained. Through the stiffness damage index, the damage and degree of the structural components are accurately identified.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a single-layer lattice shell structure damage identification method based on a direct analysis method, comprising the following steps:

[0007] S1. Construct a numerical model based on the numerical value of the lattice shell structure, use the calculation results of the direct structural analysis method of one unit and one component to determine the distribution position of important components of the lattice shell, and preliminarily arrange monitoring sensor measurement points for each unit; the monitoring sensors include displacement sensors, strain sensors and acceleration sensors;

[0008] S2. Update the numerical model based on the monitoring data, conduct construction analysis on each unit, determine the deformation and residual construction stress, re-rank the importance of the key components of the grid shell, and optimize the measurement point layout plan;

[0009] S3, using monitoring sensors to collect response data of each unit of the lattice shell structure; the response data includes displacement of key nodes of the structure, strain data of key components and overall frequency of the structure;

[0010] S4. Calculate the unit unbalanced force under the current lattice shell configuration according to the response data, and calculate the structural stiffness matrix and its change matrix;

[0011] S5. Use damage index and structural stiffness matrix to analyze the changes in the damaged area and obtain the damage status of key components of the lattice shell.

[0012] As a preferred technical solution, step S1 includes:

[0013] Perform structural nonlinear analysis on the lattice shell structure and obtain the structural stiffness matrix;

[0014] The importance of the structural stiffness matrix is ​​evaluated, the structural construction stiffness is varied, the cross-sectional bearing capacity changes of each component under the variation of the lattice shell structure components are calculated, and the matrix cross-sectional bearing capacity change matrix is ​​obtained, as shown in the following formula:

[0015]

[0016] Among them, δX is the cross-sectional bearing capacity variation matrix of each component obtained by variational calculation, δX ij It represents the influence of the change of stiffness of the i-th component on the cross-sectional bearing capacity of the j-th component;

[0017] The importance of the grid shell components is ranked according to the size of their impact to obtain the important structures of the grid shell.

[0018] As a preferred technical solution, step S1 includes:

[0019] A nonlinear analysis is performed on the high-performance beam-column analysis unit. The two bending and one torsion differential equilibrium equations of the bidirectional compression-bending member are used to derive the high-order unit shape function. The warping double moments are described by torque through the differential equilibrium relationship, and the unit stiffness matrix is ​​obtained based on the potential energy stationary value principle.

[0020] As a preferred technical solution, step S4 includes:

[0021] S401, calculating the displacement of the measuring point according to the displacement of the key nodes of the structure;

[0022] S402, structural node deformation ΔU i For displacement loads, nonlinear structural analysis is performed to calculate the internal forces of the lattice shell structure after deformation;

[0023] S403, according to the direct analysis method, judging whether the component has entered the plastic state through the internal force of the deformed lattice shell structure, if the component has entered the plastic state, executing step S404, otherwise executing step S405;

[0024] S404, calculating the cross-sectional stress distribution according to the internal force of the lattice shell structure, arranging the integration points along the cross section of the component, iteratively calculating the yield range of the cross section at the integration point using the fiber cross section method and material properties, reducing the cross section properties of the component, numerically integrating the cross section stiffness at each integration point, obtaining the stiffness of the entire key component, and updating the current lattice shell configuration;

[0025] S405, calculate the unit secant stiffness matrix K s and tangent stiffness matrix, calculate and assemble the structural unbalanced force F u,i And the overall tangent stiffness matrix K of the structure t ;

[0026] S406, according to the structural unbalanced force F u,i , calculate the structural node deformation ΔU i+1 ;

[0027] S407, if || F u，i ||2 and ||ΔU i+1 || 2 does not exceed the set limit, execute step S408, otherwise repeat steps S402-S406;

[0028] S408, calculating strain according to the internal force of the lattice shell structure, and comparing it with the strain data of the key components. If the strain difference Δε does not exceed the set limit, executing S410;

[0029] S409, recalculate the structural unbalanced force according to the strain difference Δε, and return to step S406;

[0030] S410, output the final structural stiffness matrix and its change matrix.

[0031] As a preferred technical solution, the internal force of the deformed lattice shell structure is used to determine whether the component has entered plasticity, as shown in the following formula:

[0032]

[0033] Where P is the axial force of the member, M is the bending moment, A is the cross-sectional area, W is the section modulus, f is the material design strength, Δ is the maximum relative displacement of the endpoints of the member in the local coordinate system, and δ is the maximum bending deformation of the endpoints of the member relative to the member in the local coordinate system. z, x, and y are all local coordinate axes.

[0034] As a preferred technical solution, the structural unbalanced force F u,i The calculation is as follows:

[0035] F u，i =F0-K s U

[0036] Among them, F0 represents the external load and U represents the structural deformation.

[0037] As a preferred technical solution, the calculation structure node deformation ΔU i+1 , as follows:

[0038]

[0039] Among them, F u,i Represents unbalanced force in the structure.

[0040] As a preferred technical solution, step S410 includes:

[0041] According to the change and characteristics of the stiffness matrix, determine the change of the structural stiffness matrix and obtain the stiffness change matrix ΔK n×n ;

[0042] According to the stiffness change matrix ΔK n×n , calculate the stiffness damage ratio of the i-th node as the damage index of each node;

[0043] Right D i Sort and determine the node damage degree, and use the node position where the damage degree exceeds the set threshold as the key analysis area for the next step of component damage.

[0044] As a preferred technical solution, step S5 includes:

[0045] According to the node damage index and the iteratively obtained component matrix, the change of the component stiffness matrix in the node damage area is analyzed, and the reduction degree of axial, bending and torsional stiffness at the component integration point section is calculated to obtain the damaged area of ​​the component.

[0046] In a second aspect, the present invention further provides a single-layer lattice shell structure damage identification system based on direct analysis method, which is applied to the single-layer lattice shell structure damage identification method based on direct analysis method, and includes a numerical modeling module, a first processing module, a second processing module, a third processing module and an execution output module;

[0047] The numerical modeling module is used to construct a numerical model based on the numerical values ​​of the lattice shell structure, determine the distribution positions of important lattice shell components by using the calculation results of the direct structural analysis method of one unit and one component, and preliminarily arrange monitoring sensor measurement points for each unit; the monitoring sensors include displacement sensors, strain sensors and acceleration sensors;

[0048] The first processing module is used to update the numerical model according to the monitoring data, conduct construction analysis on each unit, determine the deformation and residual construction stress, re-rank the importance of the key components of the grid shell, and optimize the measurement point layout plan;

[0049] The second processing module is used to collect the response data of each unit of the lattice shell structure by using the monitoring sensor; the response data includes the displacement of key nodes of the structure, the strain data of key components and the overall frequency of the structure;

[0050] The third processing module is used to calculate the unit unbalanced force under the current lattice shell configuration according to the response data, and calculate the structural stiffness matrix and its change matrix;

[0051] The execution output module is used to analyze the changes in the damage area and obtain the damage conditions of the key components of the lattice shell by using the damage index and the structural stiffness matrix.

[0052] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0053] (1) The component importance evaluation index of the present invention can be obtained based on the structural nonlinear analysis data by varying the structural stiffness matrix without additional nonlinear analysis. At the same time, an efficient analysis unit is proposed, which can take into account the influence of component warping, defects and semi-rigid nodes without introducing additional degrees of freedom, thereby realizing an efficient direct structural analysis method of one unit and one component.

[0054] (2) The node stiffness damage index of the present invention can be used to evaluate the structural damage area and damage degree. The calculation of the damage index is based on the direct analysis method and the newly proposed model iterative update algorithm, which has the characteristics of high calculation efficiency and good accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0056] Figure 1 This is a flow chart of a single-layer lattice shell structure damage identification method based on a direct analysis method according to an embodiment of the present invention;

[0057] Figure 2 This is a flow chart of an algorithm for evaluating the importance of a structural member according to an embodiment of the present invention;

[0058] Figure 3 A schematic diagram of a high-performance unit with warping freedom according to an embodiment of the present invention;

[0059] Figure 4 This is a schematic diagram of a unit performance comparison test of an embodiment of the present invention;

[0060] Figure 5 This is a flow chart of a component damage location identification algorithm according to an embodiment of the present invention;

[0061] Figure 6 It is a structural schematic diagram of a single-layer lattice shell structure damage identification system based on a direct analysis method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0062] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0063] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0064] See also Figure 1 This embodiment provides a single-layer lattice shell structure damage identification method based on a direct analysis method, comprising the following steps:

[0065] S1. Based on the numerical calculation model of the lattice shell structure, the calculation results of the direct structural analysis method of one unit and one component are used to determine the distribution position of the important components of the lattice shell, and the measurement points of the monitoring sensors during the construction of the lattice shell are preliminarily arranged. Among them, a high-performance beam-column analysis unit is used to perform nonlinear analysis on the large lattice shell, and the structural stiffness matrix under the structural design state is obtained. The structural stiffness is varied, and the changes in the cross-sectional bearing capacity of each component under the stiffness variation are calculated, and this is sorted to clarify the position distribution of important rods.

[0066] In this embodiment, based on the numerical calculation model of the lattice shell structure, the calculation results of the direct analysis method of the structure of one unit and one component are used to determine the distribution position of the important components of the lattice shell, and the measurement points of the monitoring sensors during the construction of the lattice shell are preliminarily arranged. The numerical model determines the units with relatively large stress or strain through finite element numerical analysis, and further clarifies the corresponding key components through the units. The structural analysis and internal force calculation method used here is the "direct analysis method".

[0067] The specific method is: perform structural nonlinear analysis to obtain the structural stiffness matrix under the structural design state, and then perform the following steps: Figure 2 The importance assessment process of structural members shown in the figure takes the variation of the stiffness of the structural members, calculates the change of the cross-sectional bearing capacity of each member under the variation of the member stiffness, and forms the cross-sectional bearing capacity change matrix as follows:

[0068]

[0069] Among them, δX is the cross-sectional bearing capacity variation matrix of each component obtained by variational calculation, δX ij It represents the influence of the stiffness change of the i-th component on the cross-sectional bearing capacity of the j-th component. ij The absolute values ​​of the components are sorted and the maximum value of each row is compared. The larger the value, the greater the influence of the corresponding component on the subsequent bearing capacity change of the structure and the higher its importance.

[0070] Here, in order to obtain the corresponding data required later, displacement sensors, strain sensors and acceleration sensors are arranged at the measuring points.

[0071] In order to explain the analysis process more specifically, this embodiment uses the following method to analyze the nonlinearity of the lattice shell structure: Figure 3 The high-performance beam-column analysis unit shown in the figure uses the two bending and one torsion differential equilibrium equations of the bidirectional compression-bending member to derive accurate high-order unit shape functions, and uses torque to describe the warping double moment through the differential equilibrium relationship, and obtains the unit stiffness matrix based on the potential energy stationary principle. The derived beam-column analysis unit does not need to introduce additional warping degrees of freedom, and is more in line with the physical meaning of spatial degrees of freedom than the traditional 7-degree-of-freedom unit. The unit performance test is shown in the figure below. Figure 4 As shown, the proof unit has good analysis accuracy and high efficiency.

[0072] S2. Update the numerical model of the single-layer lattice shell structure based on the monitoring data of the construction process, clarify the deformation and residual construction stress during construction, and design the layout of the structural health monitoring points based on the updated model to obtain the optimized layout of multiple sensors for operation and maintenance management.

[0073] S3, using monitoring sensors to collect response data of each unit of the lattice shell structure; the response data includes displacement of key nodes of the structure, strain data of key components and overall frequency of the structure;

[0074] S4. Basis Figure 5 The process shown uses the structural mechanical response obtained by the sensor to calculate the unit unbalanced force under the current configuration of the structure through nonlinear structural component analysis, and back-calculates the structural stiffness matrix and its changes. The specific steps are as follows:

[0075] S401, calculating the displacement of the measuring point according to the displacement monitoring data;

[0076] S402, node deformation ΔU i For displacement loads, nonlinear structural analysis is performed to calculate the internal forces of the structure after deformation;

[0077] S403, according to the direct analysis method theory, the internal force of the rod is used to determine whether the component enters plasticity according to the following formula. If the following formula is established, step S404 is performed; if not, step S405 is directly performed:

[0078]

[0079] Where P is the axial force of the member, M is the bending moment, A is the cross-sectional area, W is the section modulus, f is the material design strength, Δ and δ are the relative displacement of the end points of the member in the local coordinate system and the maximum bending deformation of the member, respectively, and the subscript is the local coordinate axis;

[0080] S404, calculating the cross-sectional stress distribution according to the internal force of the component, arranging integration points along the cross section of the component, using the fiber cross-sectional method for the cross section at the integration point, combining the material properties to iteratively calculate the yield range, and reducing the cross-sectional properties of the component, numerically integrating the cross-sectional stiffness at each integration point, and obtaining the stiffness of the entire component;

[0081] S405. Recalculate the unit secant stiffness matrix K according to the updated structural configuration s and tangent stiffness matrix, calculate and assemble the structural unbalanced force F u,i =F0-K s U and the structural overall tangent stiffness matrix K t ;

[0082] S406. Calculate the deformation of the structural nodes based on the structural unbalanced force

[0083] S407, if ||ΔU i+1 ||2 and ||F u,i || 2 does not exceed 0.001, proceed to S408, otherwise repeat steps S402-S406;

[0084] S408, calculate the strain according to the calculated internal force of the rod, and compare it with the strain monitoring data. If the strain difference Δε=ε 测 -ε 算 If it does not exceed 0.0001, proceed to step S410;

[0085] S409, calculating the structural unbalanced force according to the strain difference Δε, and returning to step S406 for iteration;

[0086] S410, output the total stiffness matrix and its change value, examine the change and characteristics of the stiffness matrix, and obtain a stiffness matrix change form similar to the following form to determine the change of the structural stiffness matrix:

[0087]

[0088] According to the stiffness change matrix, the stiffness damage ratio of node i is calculated as the damage index of each node as follows:

[0089]

[0090] Where K i,j is the undamaged structural stiffness matrix element, i and j represent the row and column of the structural stiffness matrix of the node pair, respectively, and n is the node number. A node has six degrees of freedom, and each node corresponds to a 6-row × 6-column stiffness matrix, so the rows and columns from 6n+1 to 6n+6 are the positions of the stiffness of the n-th node in the overall structural stiffness matrix.

[0091] Right D i Sort and determine the node damage degree, and take the node position where the damage degree exceeds 10% as the key analysis area for the next step of component damage.

[0092] S5. Use damage index and structural stiffness matrix to analyze the changes in the damaged area and obtain the damage status of key components of the lattice shell.

[0093] Finally, based on the node damage index and the iteratively obtained component matrix, the changes in the component stiffness matrix in the node damage area are analyzed, the degree of reduction in the axial, bending and torsional stiffness at the component integration point section is examined, and the damaged area of ​​the component is clarified, providing a reference for component maintenance and structural operation and maintenance.

[0094] It should be noted that, for the sake of convenience, the aforementioned method embodiments are all expressed as a series of action combinations, but those skilled in the art should know that the present invention is not limited to the described order of actions, because according to the present invention, certain steps can be performed in other orders or simultaneously.

[0095] Based on the same idea as the single-layer lattice shell structure damage identification method based on the direct analysis method in the above-mentioned embodiment, the present invention also provides a single-layer lattice shell structure damage identification system based on the direct analysis method, which can be used to execute the above-mentioned single-layer lattice shell structure damage identification method based on the direct analysis method. For ease of explanation, the structural schematic diagram of the embodiment of the single-layer lattice shell structure damage identification system based on the direct analysis method only shows the parts related to the embodiment of the present invention. Those skilled in the art can understand that the illustrated structure does not constitute a limitation on the device, and may include more or fewer components than shown in the diagram, or combine certain components, or arrange the components differently.

[0096] See also Figure 6 In another embodiment of the present application, a single-layer lattice shell structure damage identification system 10 based on direct analysis method is provided, the system comprising a numerical modeling module 11, a first processing module 12, a second processing module 13, a third processing module 14 and an execution output module 15;

[0097] The numerical modeling module 11 is used to construct a numerical model according to the numerical value of the lattice shell structure, determine the distribution position of important lattice shell components by using the calculation results of the direct structural analysis method of one unit and one component, and preliminarily arrange monitoring sensor measurement points for each unit; the monitoring sensors include displacement sensors, strain sensors and acceleration sensors;

[0098] The first processing module 12 is used to update the numerical model according to the monitoring data, perform construction analysis on each unit, determine the deformation and residual construction stress, re-rank the importance of the key components of the grid shell, and optimize the measurement point arrangement plan;

[0099] The second processing module 13 is used to collect the response data of each unit of the lattice shell structure by using the monitoring sensor; the response data includes the displacement of key nodes of the structure, the strain data of key components and the overall frequency of the structure;

[0100] The third processing module 14 is used to calculate the unit unbalanced force under the current lattice shell configuration according to the response data, and calculate the structural stiffness matrix and its change matrix;

[0101] The execution output module 15 is used to analyze the change of the damage area by using the damage index and the structural stiffness matrix, and obtain the damage status of the key components of the lattice shell.

[0102] It should be noted that the single-layer lattice shell structure damage identification system based on the direct analysis method of the present invention corresponds one-to-one to the single-layer lattice shell structure damage identification method based on the direct analysis method of the present invention. The technical features and beneficial effects described in the above-mentioned embodiment of the single-layer lattice shell structure damage identification method based on the direct analysis method are applicable to the embodiment of the single-layer lattice shell structure damage identification method based on the direct analysis method. For specific contents, please refer to the description in the embodiment of the method of the present invention, which will not be repeated here. This is hereby declared.

[0103] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0104] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A damage identification method for a single-layer lattice shell structure based on direct analysis, characterized in that: The steps include: S1. Construct a numerical model based on the numerical value of the lattice shell structure, use the calculation results of the direct structural analysis method of one unit and one component to determine the distribution position of important components of the lattice shell, and preliminarily arrange monitoring sensor measurement points for each unit; the monitoring sensors include displacement sensors, strain sensors and acceleration sensors; S2. Update the numerical model based on the monitoring data, conduct construction analysis on each unit, determine the deformation and residual construction stress, re-rank the importance of the key components of the grid shell, and optimize the measurement point layout plan; S3, using monitoring sensors to collect response data of each unit of the lattice shell structure; the response data includes displacement of key nodes of the structure, strain data of key components and overall frequency of the structure; S4. Calculate the unit unbalanced force under the current lattice shell configuration according to the response data, and calculate the structural stiffness matrix and its change matrix; S5. Use damage index and structural stiffness matrix to analyze the changes in the damaged area and obtain the damage status of key components of the lattice shell.

2. The single-layer lattice shell structure damage identification method based on direct analysis method according to claim 1 is characterized in that: The step S1 comprises: Perform structural nonlinear analysis on the lattice shell structure and obtain the structural stiffness matrix; The importance of the structural stiffness matrix is ​​evaluated, the structural construction stiffness is varied, the cross-sectional bearing capacity changes of each component under the variation of the lattice shell structure components are calculated, and the matrix cross-sectional bearing capacity change matrix is ​​obtained, as shown in the following formula: Among them, δX is the cross-sectional bearing capacity variation matrix of each component obtained by variational calculation, δX ij It represents the influence of the change of stiffness of the i-th component on the cross-sectional bearing capacity of the j-th component; The importance of the grid shell components is ranked according to the size of their impact to obtain the important structures of the grid shell.

3. The single-layer lattice shell structure damage identification method based on direct analysis method according to claim 1 is characterized in that: The step S1 comprises: A nonlinear analysis is performed on the high-performance beam-column analysis unit. The two bending and one torsion differential equilibrium equations of the bidirectional compression-bending member are used to derive the high-order unit shape function. The warping double moments are described by torque through the differential equilibrium relationship, and the unit stiffness matrix is ​​obtained based on the potential energy stationary value principle.

4. The single-layer lattice shell structure damage identification method based on direct analysis method according to claim 1 is characterized in that: The step S4 comprises: S401, calculating the displacement of the measuring point according to the displacement of the key nodes of the structure; S402, structural node deformation ΔU i For displacement loads, nonlinear structural analysis is performed to calculate the internal forces of the lattice shell structure after deformation; S403, according to the direct analysis method, judging whether the component has entered the plastic state through the internal force of the deformed lattice shell structure, if the component has entered the plastic state, executing step S404, otherwise executing step S405; S404, calculating the cross-sectional stress distribution according to the internal force of the lattice shell structure, arranging the integration points along the cross section of the component, iteratively calculating the yield range of the cross section at the integration point using the fiber cross section method and material properties, reducing the cross section properties of the component, numerically integrating the cross section stiffness at each integration point, obtaining the stiffness of the entire key component, and updating the current lattice shell configuration; S405, calculate the unit secant stiffness matrix K s and tangent stiffness matrix, calculate and assemble the structural unbalanced force F u,i And the overall tangent stiffness matrix K of the structure t ; S406, according to the structural unbalanced force F u,i , calculate the structural node deformation ΔU i+1 ; S407, if || F u，i ||2 and ||ΔU i+1 || 2 does not exceed the set limit, execute step S408, otherwise repeat steps S402-S406; S408, calculating strain according to the internal force of the lattice shell structure, and comparing it with the strain data of the key components. If the strain difference Δε does not exceed the set limit, executing S410; S409, recalculate the structural unbalanced force according to the strain difference Δε, and return to step S406; S410, output the final structural stiffness matrix and its change matrix.

5. The single-layer lattice shell structure damage identification method based on direct analysis method according to claim 4 is characterized in that: The internal force of the deformed lattice shell structure is used to judge whether the component has entered plasticity, as shown in the following formula: Where P is the axial force of the member, M is the bending moment, A is the cross-sectional area, W is the section modulus, f is the material design strength, Δ is the maximum relative displacement of the endpoints of the member in the local coordinate system, and δ is the maximum bending deformation of the endpoints of the member relative to the member in the local coordinate system. z, x, and y are all local coordinate axes.

6. The single-layer lattice shell structure damage identification method based on direct analysis method according to claim 4 is characterized in that: The structural unbalanced force F u,i The calculation is as follows: F u，i =F0-K s U Among them, F0 represents the external load and U represents the structural deformation.

7. The single-layer lattice shell structure damage identification method based on direct analysis method according to claim 4 is characterized in that: The calculated structural node deformation ΔU i+1 , as follows: Among them, F u,i Represents unbalanced force in the structure.

8. The single-layer lattice shell structure damage identification method based on direct analysis method according to claim 4 is characterized in that: The step S410 includes: According to the change and characteristics of the stiffness matrix, determine the change of the structural stiffness matrix and obtain the stiffness change matrix ΔK n×n ; According to the stiffness change matrix ΔK n×n , calculate the stiffness damage ratio of the i-th node as the damage index of each node; Right D i Sort and determine the node damage degree, and use the node position where the damage degree exceeds the set threshold as the key analysis area for the next step of component damage.

9. The single-layer lattice shell structure damage identification method based on direct analysis method according to claim 1 is characterized in that: The step S5 comprises: According to the node damage index and the iteratively obtained component matrix, the change of the component stiffness matrix in the node damage area is analyzed, and the reduction degree of axial, bending and torsional stiffness at the component integration point section is calculated to obtain the damaged area of ​​the component.

10. A single-layer lattice shell structure damage identification system based on direct analysis method, characterized in that: A single-layer lattice shell structure damage identification method based on direct analysis method applied to any one of claims 1 to 9, comprising a numerical modeling module, a first processing module, a second processing module, a third processing module and an execution output module; The numerical modeling module is used to construct a numerical model based on the numerical values ​​of the lattice shell structure, determine the distribution positions of important lattice shell components by using the calculation results of the direct structural analysis method of one unit and one component, and preliminarily arrange monitoring sensor measurement points for each unit; the monitoring sensors include displacement sensors, strain sensors and acceleration sensors; The first processing module is used to update the numerical model according to the monitoring data, conduct construction analysis on each unit, determine the deformation and residual construction stress, re-rank the importance of the key components of the grid shell, and optimize the measurement point layout plan; The second processing module is used to collect the response data of each unit of the lattice shell structure by using the monitoring sensor; the response data includes the displacement of key nodes of the structure, the strain data of key components and the overall frequency of the structure; The third processing module is used to calculate the unit unbalanced force under the current lattice shell configuration according to the response data, and calculate the structural stiffness matrix and its change matrix; The execution output module is used to analyze the changes in the damage area and obtain the damage conditions of the key components of the lattice shell by using the damage index and the structural stiffness matrix.

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