A truss bridge member internal force non-contact identification method and device based on three-dimensional laser point cloud shape change

Abstract

The application discloses a truss bridge member internal force non-contact identification method and equipment based on three-dimensional laser point cloud shape change, which comprises the following steps: extracting the point cloud axial deformation variable of each member of the truss bridge, calculating the initial member internal force value of each member and the directional cosine of each direction at the node; distinguishing reliable nodes and unreliable nodes; converting the node external load value of the reliable node; taking the initial member internal force value of the member connected with the reliable node as the prior value, combining the node external load information and the node balance condition, and correcting the reliable node member internal force value through iterative optimization to obtain the corrected reliable node member internal force value; taking the remaining initial member internal force value as the prior value, the reliable node member internal force value as the determined value, combining the node balance condition, and performing the propagation type correction on the internal force value of each member of the unreliable node through iterative optimization to obtain the corrected internal force value of each member of the unreliable node. The application effectively improves the health monitoring efficiency and reliability.

Description

Technical Field

[0001] This invention belongs to the field of bridge monitoring technology, and in particular relates to a non-contact identification method and device for internal forces of truss bridge members based on the morphological changes of three-dimensional laser point clouds. Background Technology

[0002] Due to their advantages of high structural efficiency, economical material use, and strong spanning capacity, truss bridges have experienced rapid development and widespread application. The safety of a truss bridge structure primarily depends on the internal force state of its members (such as the top chord, bottom chord, and web members). Regularly and accurately monitoring the internal forces of these members is crucial for assessing the bridge's load-bearing capacity, providing early warnings of structural risks, and guiding maintenance and repair.

[0003] Currently, the identification and monitoring of internal forces in truss bridge members mainly relies on contact sensors such as strain gauges and optical fibers. This requires attaching sensors to the surface of the members. For large truss bridges, which have a large number of members at high locations, scaffolding or aerial work platforms need to be erected. This results in long operation cycles, high safety risks, and huge manpower and material costs. Furthermore, the sensors are susceptible to environmental influences, have short lifespans, high maintenance costs, and poor durability. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a non-contact identification method and device for internal forces of truss bridge members based on the morphological changes of three-dimensional laser point clouds, which can effectively improve the efficiency and reliability of health monitoring.

[0005] Technical Solution: To achieve the above objectives, the present invention provides a non-contact identification method for internal forces of truss bridge members based on morphological changes of three-dimensional laser point clouds, comprising the following steps:

[0006] S1. Extract the axial deformation of the point cloud of each member of the truss bridge based on the point cloud model of the truss bridge.

[0007] S2. Based on the axial deformation of the point cloud, calculate the initial internal force values ​​of each member to form an initial internal force set; and establish the connection relationship between each node and member of the truss bridge, and calculate the direction cosine of each member at the node along each direction.

[0008] S3. Based on the known nature of the external load action mode and external load value of the truss bridge, the truss nodes are divided into reliable nodes and unreliable nodes.

[0009] S4. Based on the principle of mechanical action equivalence and the form of external load action at the nodes, convert the external load values ​​of the reliable nodes to equivalent values.

[0010] S5. Using the initial internal force values ​​of the members connected to the reliable node as prior values, and combining the external load information and the equilibrium conditions of the node, the internal force values ​​of each member of the reliable node are corrected through iterative optimization to obtain the corrected internal force values ​​of the reliable node members.

[0011] S6. Using the remaining initial member internal force values ​​as prior values ​​and the reliable node member internal force values ​​as definite values, combined with the node equilibrium conditions, the internal force values ​​of each member of the unreliable node are propagated through iterative optimization to obtain the corrected internal force values ​​of the unreliable node members.

[0012] Optionally, step S2 specifically includes the following steps:

[0013] S21. Based on the axial deformation of the point cloud of each member of the truss bridge extracted from the point cloud model of the scanned truss bridge, the initial internal force values ​​of each member are obtained by calculation according to the mechanics of materials. The specific calculation formula is as follows:

[0014] ,

[0015] in For rods The initial identification value of axial force, i.e., the member The initial internal force values ​​of the members; The elastic modulus of the rod; For rods The cross-sectional area; For rods Design length; For rods The point cloud axial deformation is the difference between the fitted axis length of the member under load and the design length of the member.

[0016] S22. The initial internal force values ​​of each member are used to form an initial internal force set. ,in The total number of members;

[0017] S23. Establish the connection relationships between each node and member of the truss bridge. Assume the truss has a total of [number missing]. Each node Establish a set of members connected to this node. And calculate the direction cosine of each member at the node in each direction. ,in For rods At the node Along the direction Direction cosine, These correspond to the X, Y, and Z axes of the global coordinate system, respectively.

[0018] Optionally, step S3 specifically includes the following steps:

[0019] S31. Determine the action mode of the external load on the node, the action mode including the concentrated force on the node and the linear load between nodes;

[0020] S32. Based on the form of external load action at the nodes, nodes are classified into nodes with no external load action, nodes with only concentrated load action at the nodes, nodes with only inter-node linear load action, and nodes with both concentrated load action at the nodes and inter-node linear load action; among them, nodes with only concentrated load action at the nodes, nodes with only inter-node linear load action, and nodes with both concentrated load action at the nodes and inter-node linear load action are all nodes with external load action.

[0021] S33. Classify nodes without external loads and nodes with known external load values ​​as reliable nodes and include them in the reliable node set. If a node subjected to an external load only bears a dead load or the source of the load is clear, then the external load value is considered to be known.

[0022] S34. Nodes with unknown external load values ​​among nodes subject to external loads are classified as unreliable nodes and included in the unreliable node list. .

[0023] Optionally, step S4 specifically includes the following steps:

[0024] S41. When the only reliable node has concentrated forces, the concentrated forces are treated as external loads on the node. , For nodes along External load values ​​in the direction;

[0025] S42. When a reliable node has only inter-node linear loads, the inter-node linear loads are equivalent to concentrated forces at the node and are used as external load values ​​at the node. ;

[0026] S43. When a reliable node simultaneously bears a nodal concentrated force and an inter-node linear load, the inter-node linear load is first equivalent to a nodal concentrated force, and then the nodal concentrated force and the equivalent nodal concentrated force are superimposed to obtain the nodal external load value. ;

[0027] S44. When a reliable node is a node without external load, set the external load value of that node to zero.

[0028] Optionally, the steps S42 and S43 of converting the inter-node linear load into nodal concentrated forces specifically include the following steps:

[0029] When the linear load between segments is a uniformly distributed load, the equivalent concentrated force at the two ends of the segment is:

[0030] ,

[0031] in For along direction Uniformly distributed linear load intensity, Intersegmental length, and These are the nodes at both ends of the member. Linear loads between nodes along Equivalent concentrated force in direction, Linear loads between nodes along Equivalent concentrated force in a direction;

[0032] When a linear load is distributed in a triangular pattern within a segment, the equivalent concentrated forces at the two ends of the segment are as follows:

[0033] ,

[0034] ,

[0035] in For along direction The maximum linear load strength between segments, Intersegmental length, and These are the nodes at both ends of the member. The endpoint is the endpoint where the linear load strength of the member is 0. The endpoint is the endpoint where the linear load strength of the member is the greatest. Linear loads between nodes along Equivalent concentrated force in direction, Linear loads between nodes along Equivalent concentrated force in a direction;

[0036] When a linear load is distributed in a trapezoidal shape within a segment, the equivalent concentrated forces at the two ends of the segment are as follows:

[0037] ,

[0038] ,

[0039] in and These are the nodes at both ends of the member. Intersegmental length, For rods end along direction linear load strength, For rods end along direction linear load strength, Linear loads between nodes along Equivalent concentrated force in direction, Linear loads between nodes along Equivalent concentrated force in a direction;

[0040] When a node is a common node among multiple adjacent nodes, that node is in the direction Equivalent Concentration Take the sum of the equivalent concentrated forces between adjacent segments at that node:

[0041] ,

[0042] in Indicating rods At the node along Equivalent concentrated force in direction, For nodes The set of rods connected to it.

[0043] Optionally, step S5 specifically includes the following steps:

[0044] S51. Calculate the balance residuals of each reliable node in different directions. The specific calculation formula is as follows:

[0045] ,

[0046] in For reliable nodes along The directional balance residual; For a set of reliable nodes, For nodes The set of rods connected to it. For rods The internal forces of the rods, For rods At the node along The direction cosine; For nodes along External load values ​​in the direction;

[0047] S52. Based on the balance residuals of each reliable node in each direction, and normalizing the balance residuals using the nodal force scale, construct a reliable node force imbalance coefficient to characterize the degree of force balance deviation of the reliable node. The specific calculation formula is as follows:

[0048] ,

[0049] in For a set of reliable nodes, Represents a set of reliable nodes The total number of elements in the middle, For nodes The set of rods connected to it. For rods The internal forces of the rods, For rods At the node along The direction cosine, For nodes along External load values ​​in the direction, To prevent positive numbers with a denominator of zero;

[0050] S53. Using the initial member internal force values ​​as prior values, and combining them with the nodal force imbalance coefficient, construct the objective function with the goal of minimizing the difference in member internal forces before and after correction and the magnitude of the nodal force imbalance coefficient. as follows:

[0051] ,

[0052] in, For nodes The set of rods connected to it. For a set of reliable nodes, Preset penalty coefficient; For rods The internal forces of the rods, For rods The initial identification value of axial force, The reliable node force imbalance coefficient is used to characterize the degree of deviation of the force balance of a reliable node.

[0053] S54. The internal forces of reliable node members are updated iteratively using gradient descent. The update method is as follows:

[0054] ,

[0055] in For the first The rods obtained in the next iteration The internal force values ​​of the members, , This is the iteration step size;

[0056] S55. Stop iteration when the set conditions are met, and output the corrected reliable node member internal force values. ;

[0057] S56. The corrected reliable node member internal force values As a determinant, the corrected rod force is calculated at the unreliable node. The component forces at the nodes along each direction are calculated using the following formula:

[0058] ,

[0059] For corrected force at unreliable nodes along Component of force in direction.

[0060] Optionally, stopping iteration when a set condition is met in step S55 means stopping iteration when any of the following conditions are met:

[0061] (1) The nodal force imbalance coefficient satisfies Furthermore, the change in variables between two consecutive iterations does not exceed a preset threshold, i.e.:

[0062] ,

[0063] in and The preset threshold;

[0064] (2) The number of iterations reaches the upper limit. .

[0065] Optionally, step S6 specifically includes the following steps:

[0066] S61. Calculate the equilibrium residuals of each unreliable node in the direction of non-external load. The specific calculation formula is as follows:

[0067] ,

[0068] in Unreliable node along The directional balance residual; For a set of unreliable nodes, This is the set of directions of external loads acting on each node. For nodes The set of rods connected to it. For the remaining uncorrected member set, For rods The internal forces of the rods, For rods At the node along The direction cosine, For corrected force at unreliable nodes along Component of force in direction,

[0069] S62. Based on the equilibrium residuals of each unreliable node in the direction of non-external load, and normalizing the residuals using the nodal force scale, construct an unreliable node force imbalance coefficient to characterize the degree of force equilibrium deviation of the unreliable node. The specific calculation formula is as follows:

[0070] ,

[0071] in For a set of unreliable nodes, Represents a set The total number of elements in the middle, This is the set of directions of external loads acting on each node. For nodes The set of rods connected to it. For rods The internal forces of the rods, For rods At the node along The direction cosine, For corrected force at unreliable nodes along Component of force in direction, To prevent positive numbers with a denominator of zero; For the remaining uncorrected member set,

[0072] S63. Using the remaining initial member internal forces as prior values, and combining them with the nodal force imbalance coefficient, construct the objective function with the goal of minimizing the difference in member internal forces before and after correction and the magnitude of the nodal force imbalance coefficient. as follows:

[0073] ,

[0074] in For nodes The set of rods connected to it. For a set of unreliable nodes, Preset penalty coefficient; For rods The internal forces of the rods, For rods The initial identification value of axial force, The unreliable node force imbalance coefficient is used to characterize the degree of deviation of the unreliable node from the force balance.

[0075] S64. Gradient descent iterative update of the internal forces of unreliable node members is adopted. The update method is as follows:

[0076] ,

[0077] in For the first The rods obtained in the next iteration The internal force values ​​of the members, , This is the iteration step size;

[0078] S65. Stop iteration when the set conditions are met, and output the corrected internal force values ​​of unreliable node members.

[0079] Optionally, stopping iteration when a set condition is met in step S65 means stopping iteration when any of the following conditions are met:

[0080] (1) The nodal force imbalance coefficient satisfies Furthermore, the change in variables between two consecutive iterations does not exceed a preset threshold, i.e.:

[0081] ,

[0082] in and The preset threshold;

[0083] (2) The number of iterations reaches the upper limit. .

[0084] Based on the same inventive concept, the present invention provides an electronic device including a processor and a storage medium;

[0085] The storage medium is used to store instructions;

[0086] The processor is configured to operate according to the instructions to perform the steps of the method described above.

[0087] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention utilizes three-dimensional laser scanning technology to identify the internal forces of truss bridge members by analyzing their morphological changes (micro-deformation) under load, achieving non-contact internal force identification, reducing the cost of health monitoring for truss bridges, and improving the efficiency and reliability of health monitoring; This invention achieves completely non-contact long-distance data acquisition through three-dimensional laser scanning technology, significantly improving operational safety and monitoring efficiency; By directly converting the axial deformation of the members into initial internal force values, a physical mapping between geometric shape and mechanical state is established, providing reliable priors for subsequent corrections; By distinguishing between reliable and unreliable nodes and accurately equivalentizing various linear loads, the method can flexibly adapt to complex working conditions such as dead loads and live loads; Through a two-step iterative optimization strategy, the influence of point cloud measurement noise is suppressed by utilizing node equilibrium conditions, and a propagational solution is performed on unreliable regions using the corrected reliable member forces as boundaries, achieving self-consistent closure of the entire bridge's internal force information, significantly improving the accuracy and reliability of the identification results. Attached Figure Description

[0088] Figure 1 This is a flowchart illustrating the implementation of the present invention. Detailed Implementation

[0089] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0090] like Figure 1 As shown, the present invention provides a non-contact method for identifying internal forces in truss bridge members based on 3D laser point cloud morphological changes, comprising the following steps:

[0091] S1. Extract the axial deformation of the point cloud of each member of the truss bridge based on the point cloud model of the truss bridge.

[0092] S2. Based on the axial deformation of the point cloud, calculate the initial internal force values ​​of each member to form an initial internal force set; and establish the connection relationship between each node and member of the truss bridge, and calculate the direction cosine of each member at the node along each direction.

[0093] Step S2 specifically includes the following steps:

[0094] S21. Based on the axial deformation of the point cloud of each member of the truss bridge extracted from the point cloud model of the scanned truss bridge, the initial internal force values ​​of each member are obtained by calculation according to the mechanics of materials. The specific calculation formula is as follows:

[0095] ,

[0096] in For rods The initial identification value of axial force, i.e., the member The initial internal force values ​​of the members; The elastic modulus of the rod; For rods The cross-sectional area; For rods Design length; For rods The point cloud axial deformation is the difference between the fitted axis length of the member under load and the design length of the member.

[0097] S22. The initial internal force values ​​of each member are used to form an initial internal force set. ,in The total number of members;

[0098] S23. Establish the connection relationships between each node and member of the truss bridge. Assume the truss has a total of [number missing]. Each node Establish a set of members connected to this node. And calculate the direction cosine of each member at the node in each direction. ,in For rods At the node Along the direction Direction cosine, These correspond to the X, Y, and Z axes of the global coordinate system, respectively.

[0099] S3. Based on the known nature of the external load action mode and external load value of the truss bridge, the truss nodes are divided into reliable nodes and unreliable nodes.

[0100] Step S3 specifically includes the following steps:

[0101] S31. Determine the action mode of the external load on the node, the action mode including the concentrated force on the node and the linear load between nodes;

[0102] S32. Based on the form of external load action at the nodes, nodes are classified into nodes with no external load action, nodes with only concentrated load action at the nodes, nodes with only inter-node linear load action, and nodes with both concentrated load action at the nodes and inter-node linear load action; among them, nodes with only concentrated load action at the nodes, nodes with only inter-node linear load action, and nodes with both concentrated load action at the nodes and inter-node linear load action are all nodes with external load action.

[0103] S33. Classify nodes without external loads and nodes with known external load values ​​as reliable nodes and include them in the reliable node set. If a node subjected to an external load only bears a dead load or the source of the load is clear, then the external load value is considered to be known.

[0104] S34. Nodes with unknown external load values ​​among nodes subject to external loads are classified as unreliable nodes and included in the unreliable node list. .

[0105] S4. Based on the principle of mechanical action equivalence and the form of external load action at the node, convert the external load value of the reliable node to an equivalent value.

[0106] Step S4 specifically includes the following steps:

[0107] S41. When the only reliable node has concentrated forces, the concentrated forces are treated as external loads on the node. , For nodes along External load value in the direction.

[0108] S42. When a reliable node has only inter-node linear loads, the inter-node linear loads are equivalent to concentrated forces at the node and are used as external load values ​​at the node. ...

[0109] S43. When a reliable node simultaneously bears a nodal concentrated force and an inter-node linear load, the inter-node linear load is first equivalent to a nodal concentrated force, and then the nodal concentrated force and the equivalent nodal concentrated force are superimposed to obtain the nodal external load value. .

[0110] The specific steps in steps S42 and S43 of converting the internode linear load into nodal concentrated forces include the following:

[0111] (1) When the linear load between segments is a uniformly distributed load, the equivalent concentrated force at the two ends of the segment is:

[0112] ,

[0113] in For along direction Uniformly distributed linear load intensity, Intersegmental length, and These are the nodes at both ends of the member. Linear loads between nodes along Equivalent concentrated force in direction, Linear loads between nodes along Equivalent concentrated force in direction.

[0114] (2) When the linear load is distributed in a triangular pattern within the segment, the equivalent concentrated forces at the two ends of the segment are as follows:

[0115] ,

[0116] ,

[0117] in For along direction The maximum linear load strength between segments, Intersegmental length, and These are the nodes at both ends of the member. The endpoint is the endpoint where the linear load strength of the member is 0. The endpoint is the endpoint where the linear load strength of the member is the greatest. Linear loads between nodes along Equivalent concentrated force in direction, Linear loads between nodes along Equivalent concentrated force in direction.

[0118] (3) When the linear load is distributed in a trapezoidal shape within the segment, the equivalent concentrated forces at the two ends of the segment are as follows:

[0119] ,

[0120] ,

[0121] in and These are the nodes at both ends of the member. Intersegmental length, For rods end along direction linear load strength, For rods end along direction linear load strength, Linear loads between nodes along Equivalent concentrated force in direction, Linear loads between nodes along Equivalent concentrated force in direction.

[0122] (4) When a node is a common node among multiple adjacent nodes, the node in the direction Equivalent Concentration Take the sum of the equivalent concentrated forces between adjacent segments at that node:

[0123] ,

[0124] in Indicating rods At the node along Equivalent concentrated force in direction.

[0125] S44. When a reliable node is a node without external load, set the external load value of that node to zero.

[0126] S5. Using the initial internal force values ​​of the members connected to the reliable node as prior values, and combining the external load information and the equilibrium conditions of the node, the internal force values ​​of each member of the reliable node are corrected through iterative optimization to obtain the corrected internal force values ​​of the reliable node members.

[0127] Step S5 specifically includes the following steps:

[0128] S51. Calculate the balance residuals of each reliable node in different directions. The specific calculation formula is as follows:

[0129] ,

[0130] in For reliable nodes along The directional balance residual; For a set of reliable nodes, For nodes The set of rods connected to it. For rods The internal forces of the rods, For rods At the node along The direction cosine; For nodes along External load value in the direction.

[0131] S52. Based on the equilibrium residuals of each reliable node in each direction, and normalizing the equilibrium residuals using the nodal force scale to eliminate the influence of differences in force levels on the evaluation results, a reliable node force imbalance coefficient is constructed to characterize the degree of force balance deviation of reliable nodes. The specific calculation formula is as follows:

[0132] ,

[0133] in For a set of reliable nodes, Represents a set of reliable nodes The total number of elements in the middle, For nodes The set of rods connected to it. For rods The internal forces of the rods, For rods At the node along The direction cosine, For nodes along External load values ​​in the direction, To prevent positive numbers with a denominator of zero.

[0134] S53. Using the initial member internal force values ​​as prior values, and combining them with the nodal force imbalance coefficient, construct the objective function with the goal of minimizing the difference in member internal forces before and after correction and the magnitude of the nodal force imbalance coefficient. as follows:

[0135] ,

[0136] in, For nodes The set of rods connected to it. For a set of reliable nodes, This is a preset penalty coefficient.

[0137] S54. The internal forces of reliable node members are updated iteratively using gradient descent. The update method is as follows:

[0138] ,

[0139] in For the first The rods obtained in the next iteration The internal force values ​​of the members, , This is the iteration step size.

[0140] S55. Stop the iteration and output the corrected reliable node member internal force values ​​when any of the following conditions are met. :

[0141] (1) The nodal force imbalance coefficient satisfies Furthermore, the change in variables between two consecutive iterations does not exceed a preset threshold, i.e.:

[0142] ,

[0143] in and The preset threshold;

[0144] (2) The number of iterations reaches the upper limit. .

[0145] S56. The corrected reliable node member internal force values As a determinant, the corrected rod force is calculated at the unreliable node. The component forces at the nodes along each direction are calculated using the following formula:

[0146] ,

[0147] For corrected force at unreliable nodes along Component of force in direction.

[0148] S6. Using the remaining initial member internal force values ​​as prior values ​​and the reliable node member internal force values ​​as definite values, combined with the node equilibrium conditions, the internal force values ​​of each member of the unreliable node are propagated through iterative optimization to obtain the corrected internal force values ​​of the unreliable node members.

[0149] Step S6 includes the following sub-steps:

[0150] S61. Calculate the equilibrium residuals of each unreliable node in the direction of non-external load. The specific calculation formula is as follows:

[0151] ,

[0152] in Unreliable node along The directional balance residual; For a set of unreliable nodes, This is the set of directions of external loads acting on each node. For nodes The set of rods connected to it. For the remaining uncorrected member set, For rods The internal forces of the rods, For rods At the node along The direction cosine of the direction.

[0153] S62. Based on the equilibrium residuals of each unreliable node in the direction of non-external load, and normalizing the residuals using the nodal force scale to eliminate the influence of differences in force levels of different nodes on the evaluation results, an unreliable node force imbalance coefficient is constructed to characterize the degree of force balance deviation of unreliable nodes. The specific calculation formula is as follows:

[0154] ,

[0155] in For a set of unreliable nodes, Represents a set The total number of elements in the middle, This is the set of directions of external loads acting on each node. For nodes The set of rods connected to it. For rods The internal forces of the rods, For rods At the node along The direction cosine, For corrected force at unreliable nodes along Component of force in direction, To prevent positive numbers with a denominator of zero.

[0156] S63. Using the remaining initial member internal forces as prior values, and combining them with the nodal force imbalance coefficient, construct the objective function with the goal of minimizing the difference in member internal forces before and after correction and the magnitude of the nodal force imbalance coefficient. as follows:

[0157] ,

[0158] in For nodes The set of rods connected to it. For a set of unreliable nodes, This is a preset penalty coefficient.

[0159] S64. Gradient descent iterative update of the internal forces of unreliable node members is adopted. The update method is as follows:

[0160] ,

[0161] in For the first The rods obtained in the next iteration The internal force values ​​of the members, , This is the iteration step size.

[0162] S65. Stop the iteration and output the corrected internal force values ​​of unreliable node members when any of the following conditions are met:

[0163] (1) The nodal force imbalance coefficient satisfies Furthermore, the change in variables between two consecutive iterations does not exceed a preset threshold, i.e.:

[0164] ,

[0165] in and The preset threshold;

[0166] (2) The number of iterations reaches the upper limit. .

[0167] This invention achieves true "non-contact, long-distance" identification of internal forces in truss bridge members, completely avoiding the cumbersome process and high cost of installing sensors on truss bridge members. Surveyors can complete data collection from under the bridge or on the riverbank without approaching the truss bridge members, greatly improving operational safety and efficiency. It is particularly suitable for large or high-risk truss bridges spanning canyons and rivers. It avoids errors in measurement results due to sensor aging and performance degradation, eliminates the need for sensor maintenance costs, provides accurate identification of member deformation, and offers high precision in internal force identification, representing a qualitative leap from geometric measurement to mechanical state assessment.

[0168] This invention achieves automation or semi-automation through algorithms, providing core technical support and reliable data support for building an intelligent truss bridge health monitoring system. It provides key state parameters for truss bridge digital twins, and the identified high-precision internal force distribution data can serve as key driving and verification data for real-time simulation, prediction, and safety early warning of truss bridge digital twin models. It has significant engineering application value and broad market prospects.

[0169] Example 2: An electronic device according to the present invention includes a processor and a storage medium;

[0170] Storage media are used to store instructions;

[0171] The processor is configured to operate according to the instructions to perform the steps of the method described above.

Claims

1. A non-contact method for identifying internal forces in truss bridge members based on morphological changes of three-dimensional laser point clouds, characterized in that, Includes the following steps: S1. Extract the axial deformation of the point cloud of each member of the truss bridge based on the point cloud model of the truss bridge. S2. Based on the axial deformation of the point cloud, calculate the initial internal force values ​​of each member to form the initial internal force set; The connection relationship between each node and member of the truss bridge is established, and the direction cosine of each member at the node along each direction is calculated. Step S2 specifically includes the following steps: S21. Based on the axial deformation of the point cloud of each member of the truss bridge extracted from the point cloud model of the scanned truss bridge, the initial internal force values ​​of each member are obtained by calculation according to the mechanics of materials. The specific calculation formula is as follows: ， in For rods The initial identification value of axial force, i.e., the member The initial internal force values ​​of the members; The elastic modulus of the rod; For rods The cross-sectional area; For rods Design length; For rods The point cloud axial deformation is the difference between the fitted axis length of the member under load and the design length of the member. S22. The initial internal force values ​​of each member are used to form an initial internal force set. ,in The total number of members; S23. Establish the connection relationships between each node and member of the truss bridge. Assume the truss has a total of [number missing]. Each node Establish a set of members connected to this node. And calculate the direction cosine of each member at the node in each direction. ,in For rods At the node Along the direction Direction cosine, These correspond to the X, Y, and Z axes of the global coordinate system, respectively. S3. Based on the known nature of the external load action mode and external load value of the truss bridge, the truss nodes are divided into reliable nodes and unreliable nodes. Step S3 specifically includes the following steps: S31. Determine the action mode of the external load on the node, the action mode including the concentrated force on the node and the linear load between nodes; S32. Based on the form of external load action at the node, nodes are divided into nodes with no external load action, nodes with only concentrated load action at the node, nodes with only inter-node linear load action, and nodes with both concentrated load action at the node and inter-node linear load action. Among them, nodes with only concentrated nodal forces, nodes with only inter-node linear loads, and nodes with both concentrated nodal forces and inter-node linear loads are all nodes with external loads. S33. Classify nodes without external loads and nodes with known external load values ​​as reliable nodes and include them in the reliable node set. If a node subjected to an external load only bears a dead load or the source of the load is clear, then the external load value is considered to be known. S34. Nodes with unknown external load values ​​among nodes subject to external loads are classified as unreliable nodes and included in the unreliable node list. ; S4. Based on the principle of mechanical action equivalence and the form of external load action at the nodes, convert the external load values ​​of the reliable nodes to equivalent values. Step S4 specifically includes the following steps: S41. When the only reliable node has concentrated forces, the concentrated forces are treated as external loads on the node. , For nodes along External load values ​​in the direction; S42. When a reliable node has only inter-node linear loads, the inter-node linear loads are equivalent to concentrated forces at the node and are used as external load values ​​at the node. ; S43. When a reliable node simultaneously bears a nodal concentrated force and an inter-node linear load, the inter-node linear load is first equivalent to a nodal concentrated force, and then the nodal concentrated force and the equivalent nodal concentrated force are superimposed to obtain the nodal external load value. ; S44. When a reliable node is a node without external load, set the external load value of that node to zero. S5. Using the initial internal force values ​​of the members connected to the reliable node as prior values, and combining the external load information and the equilibrium conditions of the node, the internal force values ​​of each member of the reliable node are corrected through iterative optimization to obtain the corrected internal force values ​​of the reliable node members. S6. Using the remaining initial member internal force values ​​as prior values ​​and the reliable node member internal force values ​​as definite values, combined with the node equilibrium conditions, the internal force values ​​of each member of the unreliable node are propagated through iterative optimization to obtain the corrected internal force values ​​of the unreliable node members.

2. The non-contact identification method for internal forces of truss bridge members based on morphological changes of three-dimensional laser point clouds according to claim 1, characterized in that, The specific steps in steps S42 and S43 of converting the internode linear load into nodal concentrated forces include the following: When the linear load between segments is a uniformly distributed load, the equivalent concentrated force at the two ends of the segment is: ， in For along direction Uniformly distributed linear load intensity, Intersegmental length, and These are the nodes at both ends of the member. Linear loads between nodes along Equivalent concentrated force in direction, Linear loads between nodes along Equivalent concentrated force in a direction; When a linear load is distributed in a triangular pattern within a segment, the equivalent concentrated forces at the two ends of the segment are as follows: ， ， in For along direction The maximum linear load strength between segments, Intersegmental length, and These are the nodes at both ends of the member. The endpoint is the endpoint where the linear load strength of the member is 0. The endpoint is the endpoint where the linear load strength of the member is the greatest. Linear loads between nodes along Equivalent concentrated force in direction, Linear loads between nodes along Equivalent concentrated force in a direction; When a linear load is distributed in a trapezoidal shape within a segment, the equivalent concentrated forces at the two ends of the segment are as follows: ， ， in and These are the nodes at both ends of the member. Intersegmental length, For rods end along direction linear load strength, For rods end along direction linear load strength, Linear loads between nodes along Equivalent concentrated force in direction, Linear loads between nodes along Equivalent concentrated force in a direction; When a node is a common node among multiple adjacent nodes, that node is in the direction Equivalent Concentration Take the sum of the equivalent concentrated forces between adjacent segments at that node: ， in Indicating rods At the node along Equivalent concentrated force in direction, For nodes The set of rods connected to it.

3. The non-contact identification method for internal forces of truss bridge members based on morphological changes of three-dimensional laser point clouds according to claim 2, characterized in that, Step S5 specifically includes the following steps: S51. Calculate the balance residuals of each reliable node in different directions. The specific calculation formula is as follows: ， in For reliable nodes along The directional balance residual; For a set of reliable nodes, For nodes The set of rods connected to it. For rods The internal forces of the rods, For rods At the node along The direction cosine; For nodes along External load values ​​in the direction; S52. Based on the balance residuals of each reliable node in each direction, and normalizing the balance residuals using the nodal force scale, construct a reliable node force imbalance coefficient to characterize the degree of force balance deviation of the reliable node. The specific calculation formula is as follows: ， in For a set of reliable nodes, Represents a set of reliable nodes The total number of elements in the middle. For nodes The set of rods connected to it. For rods The internal forces of the rods, For rods At the node along The direction cosine, For nodes along External load values ​​in the direction, To prevent positive numbers with a denominator of zero; S53. Using the initial internal force values ​​of the members as prior values, and combining them with the nodal force imbalance coefficient, construct the objective function with the goal of minimizing the difference in internal forces of the members before and after correction and the magnitude of the nodal force imbalance coefficient. as follows: ， in, For nodes The set of rods connected to it. For a set of reliable nodes, Preset penalty coefficient; For rods The internal forces of the rods, For rods The initial identification value of axial force, The reliable node force imbalance coefficient is used to characterize the degree of deviation from the force balance of a reliable node. S54. The internal forces of reliable node members are updated iteratively using gradient descent. The update method is as follows: ， in For the first The rods obtained in the next iteration The internal force values ​​of the members, , This is the iteration step size; S55. Stop iteration when the set conditions are met, and output the corrected reliable node member internal force values. ; S56. The corrected reliable node member internal force values As a determinant, the corrected rod force is calculated at the unreliable node. The component forces at the nodes along each direction are calculated using the following formula: ， For the corrected force at the unreliable node along Component of force in direction.

4. The non-contact identification method for internal forces of truss bridge members based on morphological changes of three-dimensional laser point clouds according to claim 3, characterized in that, In step S55, stopping iteration when a set condition is met means stopping iteration when any of the following conditions are met: (1) The nodal force imbalance coefficient satisfies Furthermore, the change in variables between two consecutive iterations does not exceed a preset threshold, i.e.: ， in and The preset threshold; (2) The number of iterations reaches the upper limit. .

5. The non-contact identification method for internal forces of truss bridge members based on morphological changes of three-dimensional laser point clouds according to claim 4, characterized in that, Step S6 specifically includes the following steps: S61. Calculate the equilibrium residuals of each unreliable node in the direction of non-external load. The specific calculation formula is as follows: ， in Unreliable node along The directional balance residual; For a set of unreliable nodes, This is the set of directions of external loads acting on each node. For nodes The set of rods connected to it. For the remaining uncorrected member set, For rods The internal forces of the rods, For rods At the node along The direction cosine, For the corrected force at the unreliable node along Component of force in direction, S62. Based on the equilibrium residuals of each unreliable node in the direction of non-external load, and normalizing the residuals using the nodal force scale, construct an unreliable node force imbalance coefficient to characterize the degree of force equilibrium deviation of the unreliable node. The specific calculation formula is as follows: ， in For a set of unreliable nodes, Represents a set The total number of elements in the middle, This is the set of directions of external loads acting on each node. For nodes The set of rods connected to it. For rods The internal forces of the rods, For rods At the node along The direction cosine, For the corrected force at the unreliable node along Component of force in direction, To prevent positive numbers with a denominator of zero; For the remaining uncorrected member set, S63. Using the remaining initial member internal forces as prior values, and combining them with the nodal force imbalance coefficient, construct the objective function with the goal of minimizing the difference in member internal forces before and after correction and the magnitude of the nodal force imbalance coefficient. as follows: ， in For nodes The set of rods connected to it. For a set of unreliable nodes, The preset penalty coefficient; For rods The internal forces of the rods, For rods The initial identification value of axial force, The unreliable node force imbalance coefficient is used to characterize the degree of deviation of the unreliable node from the force balance. S64. Gradient descent iterative update of the internal forces of unreliable node members is adopted. The update method is as follows: ， in For the first The rods obtained in the next iteration The internal force values ​​of the members, , This is the iteration step size; S65. Stop iteration when the set conditions are met, and output the corrected internal force values ​​of unreliable node members.

6. The non-contact identification method for internal forces of truss bridge members based on morphological changes of three-dimensional laser point clouds according to claim 5, characterized in that, In step S65, stopping iteration when a set condition is met means stopping iteration when any of the following conditions are met: (1) The nodal force imbalance coefficient satisfies Furthermore, the change in variables between two consecutive iterations does not exceed a preset threshold, i.e.: ， in and The preset threshold; (2) The number of iterations reaches the upper limit. .

7. An electronic device, characterized in that, Including processor and storage media; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1 to 6.

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