Damage identification method and system for single-layer lattice shell structures based on direct analysis

Abstract

The present invention discloses a method and system for identifying damage to a single-layer lattice shell structure based on a direct analysis method. The method comprises the following steps: S1, constructing a numerical model based on the numerical values ​​of the lattice shell structure, analyzing the key components of the lattice shell as units to determine their distribution locations, and preliminarily arranging monitoring sensor measurement points for each unit; S2, updating the numerical model based on the monitoring data, performing a construction analysis on each unit, determining deformation and residual construction stress, re-ranking the importance of the key components of the lattice shell, and optimizing the measurement point arrangement plan; S3, using monitoring sensors to collect response data for each unit of the lattice shell structure; S4, calculating the unit unbalanced force under the current lattice shell configuration based on the response data, and calculating the structural stiffness matrix and its change matrix; S5, using the damage index and the structural stiffness matrix to analyze the changes in the damaged area and obtain the damage status of the key components of the lattice shell. The present invention accurately identifies the damage and damage degree of structural components through the stiffness 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 a direct analysis method. Background Art

[0002] With the advancement of aesthetic standards, the shapes and structural forms of single-layer lattice shells are becoming increasingly novel. However, due to the prominent nonlinear behavior of single-layer lattice shells and the complex interaction mechanisms between components, traditional structural analysis and design methods based on empirical coefficients present certain problems in the stress analysis of modern lattice shells. Existing methods for assessing structural damage locations most commonly use frequency domain analysis, time domain analysis, and finite element model modification methods. Frequency domain methods are significantly affected by environmental factors and require a large number of sensors, resulting in a high data processing workload. Some damage signals in time domain methods may be obscured by larger amplitude signals unrelated to the damage. The finite element model correction method is to obtain a finite element model that matches the test data, and then perform damage and retrograde evaluation on the model, so as to locate and quantify the damage more clearly. With the development of digital twin technology, this method is gradually being widely used in damage identification. However, the current finite element model update theory and technology are imperfect. In order to ensure efficiency, many methods use the results obtained by 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 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 approach for structural analysis and design. By directly considering the effects of structural defects and joint stiffness in nonlinear analysis, it determines the true mechanical state of the structure and directly determines the bearing capacity of members based on internal forces, eliminating the need for stability verification using empirical coefficients. This method offers high analytical efficiency and more accurate judgments of the structural stress state. Its core approach is to propose a reasonable overall structural defect model and high-performance analysis units, enabling efficient simulation methods that directly account for member defects and joint stiffness in the unit stiffness matrix. However, the current difficulty in applying direct analysis methods to structural damage identification lies primarily in reliably updating numerical analysis model data and determining structural damage indicators to effectively assess the structure's current state. Summary of the Invention

[0004] The main purpose of the present invention is to overcome the shortcomings and deficiencies of the existing technology and 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 the actual bearing capacity of the structure, through nonlinear iteration, the change of the overall stiffness matrix of the structure is obtained, and the stiffness change at the node and the corresponding component is further obtained. Through the stiffness damage index, the damage and degree of the structural component 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 method for damage identification of a single-layer lattice shell structure 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 lattice shell components, 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 are calculated, and the matrix cross-sectional bearing capacity change matrix is ​​obtained as follows:

[0015]

[0016] Among them, δX is the cross-sectional bearing capacity change 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;

[0017] The importance of the lattice shell components is ranked according to the size of their impact to obtain the important structures of the lattice 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 biaxial 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. Calculate the displacement of the measuring point based on 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 deformed lattice shell structure;

[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. Calculate the cross-sectional stress distribution based on the internal force of the lattice shell structure, arrange integration points along the component cross section, iteratively calculate the yield range of the cross section at the integration points using the fiber cross section method and material properties, reduce the component cross section properties, numerically integrate the cross section stiffness at each integration point, obtain the stiffness of the entire key component, and update 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 based on 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 the plastic state, as shown in the following formula:

[0032]

[0033] Where P is the axial force in the member, M is the bending moment, A is the cross-sectional area, W is the section modulus, f is the design strength of the material, 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 Indicates the 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] To D i Sort and determine the degree of node damage, and use the node position where the damage degree exceeds the set threshold as the key analysis area for component damage in the next step.

[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 degree of reduction of the 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 a direct analysis method, which is applied to the single-layer lattice shell structure damage identification method based on a 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 position of important lattice shell components 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 based on 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 lattice shell, and optimize the measurement point layout plan;

[0049] The second processing module is used to collect response data of each unit of the lattice shell structure using monitoring sensors; the response data includes displacement of key nodes of the structure, strain data of key components and 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 using damage indicators and structural stiffness matrix to obtain the damage status of key components of the lattice shell.

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

[0053] (1) The present invention can obtain the component importance evaluation index based on the structural nonlinear analysis data by varying the structural stiffness matrix without the need for additional nonlinear analysis. At the same time, an efficient analysis unit is proposed, which can consider the effects 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 present invention can be used to evaluate the structural damage area and damage degree through the node stiffness damage index. 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 computational 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 following briefly introduces the drawings required for use in the description of the embodiments. 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 any creative work.

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

[0058] Figure 3 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 Schematic diagram of the structure 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 invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0063] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, 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 and the results of the direct structural analysis method of one unit and one component, the distribution location of the important lattice shell components was determined, and the measurement points for monitoring sensors during the lattice shell construction were preliminarily arranged. A high-performance beam-column analysis unit was used to conduct nonlinear analysis of the large lattice shell, and the structural stiffness matrix under the structural design state was obtained. The structural stiffness was varied, and the changes in the cross-sectional bearing capacity of each component under the stiffness variation were calculated and ranked to clarify the location and distribution of important members.

[0066] In this example, based on a numerical calculation model of the lattice shell structure, the results of a unit-by-component direct structural analysis method were used to determine the distribution of key lattice shell components and to preliminarily arrange the measurement points for monitoring sensors during the lattice shell construction process. The numerical model uses finite element analysis to identify units with relatively high stress or strain, and further identifies the corresponding key components based on these 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 structural member importance assessment process shown in the figure takes the variation of the structural member stiffness, calculates the change of the cross-sectional bearing capacity of each member under the variation of the member stiffness, and forms the matrix of the cross-sectional bearing capacity change as follows:

[0068]

[0069] Among them, δX is the cross-sectional bearing capacity change matrix of each component obtained by variational calculation, δX ij Indicates the effect of the stiffness change of the i-th component on the cross-sectional bearing capacity of the j-th component. ij Sort by the absolute value of each row and compare the maximum value in each row. The larger the value, the greater the impact of the corresponding component on the subsequent bearing capacity change of the structure and the highest importance.

[0070] Here, in order to obtain the corresponding data required subsequently, 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 biaxial compression-bending members to derive accurate high-order unit shape functions. The unit then uses torque to describe the warping dual moments through differential equilibrium relationships, and the unit stiffness matrix is ​​derived based on the principle of potential energy stationary value. The derived beam-column analysis unit does not require the introduction of additional warping degrees of freedom and is more consistent with the physical meaning of spatial degrees of freedom than the traditional 7-DOF unit. The unit's 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 during construction, 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 analysis, and inversely 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. Based on the direct analysis method, determine whether the component has entered plasticity by using the internal force of the rod according to the following formula. If the following formula is true, proceed to step S404; if not, proceed directly to step S405:

[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 design strength of the material, Δ and δ are the relative displacement of the end points of the component in the local coordinate system and the maximum bending deformation of the member, respectively, and the subscript is the local coordinate axis;

[0080] S404. Calculate the cross-sectional stress distribution based on the component internal force, arrange integration points along the component cross section, iteratively calculate the yield range for the cross section at the integration points using the fiber cross section method in combination with material properties, reduce the component cross section properties, numerically integrate the cross section stiffness at each integration point, and obtain 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 overall tangent stiffness matrix K of the structure 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 based on 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 element of the undamaged structural stiffness matrix, i and j represent the row and column of the structural stiffness matrix for a 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. Therefore, the rows and columns 6n+1 to 6n+6 represent the position of the stiffness of node n in the overall structural stiffness matrix.

[0091] To D i Sort and determine the degree of node damage, and use the node positions where the degree of damage exceeds 10% as the key analysis areas for component damage in the next step.

[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 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 repair 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 concept 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 implement the above-mentioned single-layer lattice shell structure damage identification method based on the direct analysis method. For ease of explanation, the structural 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 will understand that the illustrated structure does not constitute a limitation of the device, and it can include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0096] See also Figure 6 In another embodiment of the present application, a single-layer lattice shell structure damage identification system 10 based on a 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 based on the numerical values ​​of the lattice shell structure, determine the distribution position of important lattice shell components 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 based on 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 lattice shell, and optimize the measurement point layout plan;

[0099] The second processing module 13 is used to collect response data of each unit of the lattice shell structure using monitoring sensors; the response data includes displacement of key nodes of the structure, strain data of key components and 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 changes in the damage area 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. No further details will be given here. This is hereby declared.

[0103] The technical features of the above embodiments can be combined arbitrarily. 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 considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A damage identification method for single-layer lattice shell structure based on direct analysis method, 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 the important components of the lattice shell, and preliminarily arrange the monitoring sensor measurement points for each unit; The monitoring sensors include displacement sensors, strain sensors and acceleration sensors; The step S1 comprises: The high-order element shape function is derived using the two bending and one torsion differential equilibrium equations of biaxial compression-bending members. The warping double moments are described by torque through the differential equilibrium relationship, and the element stiffness matrix is ​​obtained based on the potential energy stationary value principle. 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 are calculated, and the matrix cross-sectional bearing capacity change matrix is ​​obtained as follows: Among them, δX is the cross-sectional bearing capacity change 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; Sort the importance of the lattice shell components according to their impact and obtain the important structures of the lattice shell; 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 damage identification method for single-layer lattice shell structure based on direct analysis method according to claim 1 is characterized in that: The step S4 comprises: S401. Calculate the displacement of the measuring point based on 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 deformed lattice shell structure; 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. Calculate the cross-sectional stress distribution based on the internal force of the lattice shell structure, arrange integration points along the component cross section, iteratively calculate the yield range of the cross section at the integration points using the fiber cross section method and material properties, reduce the component cross section properties, numerically integrate the cross section stiffness at each integration point, obtain the stiffness of the entire key component, and update 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 based on 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.

3. The damage identification method for single-layer lattice shell structure based on direct analysis method according to claim 2 is characterized in that: The internal force of the deformed lattice shell structure is used to determine whether the component has entered the plastic state, as shown in the following formula: Where P is the axial force in the member, M is the bending moment, A is the cross-sectional area, W is the section modulus, f is the design strength of the material, 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.

4. The single-layer lattice shell structure damage identification method based on direct analysis method according to claim 2 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.

5. The damage identification method for single-layer lattice shell structure based on direct analysis method according to claim 2 is characterized in that: The calculated structural node deformation ΔU i+1 , as follows: Among them, F u,i Indicates the unbalanced force in the structure.

6. The damage identification method for single-layer lattice shell structure based on direct analysis method according to claim 2 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; To D i Sort and determine the degree of node damage, and use the node position where the damage degree exceeds the set threshold as the key analysis area for component damage in the next step.

7. The damage identification method for single-layer lattice shell structure 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 degree of reduction of the axial, bending and torsional stiffness at the component integration point section is calculated to obtain the damaged area of ​​the component.

8. 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 a direct analysis method applied to any one of claims 1 to 7, 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 position of important lattice shell components 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 based on 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 lattice shell, and optimize the measurement point layout plan; The second processing module is used to collect response data of each unit of the lattice shell structure using monitoring sensors; the response data includes displacement of key nodes of the structure, strain data of key components and 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 using damage indicators and structural stiffness matrix to obtain the damage status of key components of the lattice shell.

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