Steel structure joint bolt axial force control method based on BIM real-time monitoring

Abstract

A steel structure node bolt axial force control method based on BIM real-time monitoring relates to the technical field of steel structure construction and comprises calculating a target bolt predicted axial force value after a preset time; determining that the target high-strength bolt is in a loose state when the predicted axial force value is lower than a preset threshold value, and applying a first compensation axial force to the target high-strength bolt; obtaining the axial force value of the target bolt again after a preset verification time to determine whether it is less than a preset proportion of the initial pretightening force; if it is less than the preset proportion of the initial pretightening force, reducing the stiffness parameter of the virtual connection unit corresponding to the target high-strength bolt to obtain a stiffness reduction coefficient; based on the stiffness reduction coefficient, calculating the compensation axial force value of the adjacent high-strength bolt, and applying a second compensation axial force to the adjacent high-strength bolt; in the case of physical compensation failure of the target bolt, the stiffness reduction and mechanical redistribution calculation are used to compensate by using the surrounding bolts, thereby effectively maintaining the initial overall stiffness and safety and stability of the steel structure node.

Description

Technical Field

[0001] This invention relates to the field of steel structure construction technology, specifically to a method for controlling the axial force of bolts at steel structure nodes based on real-time BIM monitoring. Background Technology

[0002] Steel structure nodes include steel components and high-strength bolts used for connection and fixation. During use, the preload of high-strength bolts will gradually and irreversibly decrease due to factors such as vibration loads, temperature cycling, material creep, and slippage of connection surfaces. In severe cases, this can lead to degradation of the stiffness of the steel structure node, connection slippage, or even instability of the entire structure.

[0003] In recent years, BIM technology has been introduced into the field of steel structure health monitoring. Existing solutions typically involve placing axial force sensors on bolts or connecting plates and mapping the measured data to the BIM model in real time. When the BIM platform determines that the axial force is below a safety threshold, it sends an action command to the corresponding axial force compensation actuator. The existing compensation method involves repeatedly applying progressively stronger drive signals to the same actuator when the axial force of a bolt is insufficient, until the axial force recovers or reaches the actuator's output limit.

[0004] However, in actual engineering, axial force compensation devices are prone to physical degradation such as friction and jamming after long-term use, resulting in their actual output capacity being lower than the design value. In this situation, repeatedly generating secondary or even multiple compensation commands based on the axial force deviation of the same bolt not only fails to effectively restore the preload, but also accelerates failure due to continuous overload of the actuator, leaving the node in a dangerous state of insufficient axial force for a long time.

[0005] More importantly, existing technologies lack overall stress analysis of steel structure nodes. When the axial force of a bolt remains low, the local stiffness of its corresponding connection interface has changed, while adjacent bolts still operate according to their initial design state, resulting in uneven load distribution at the node and accelerating the attenuation of the axial force of surrounding bolts. In addition, changes in ambient temperature cause thermal expansion and contraction of the steel structure. Since the expansion coefficients of bolts and steel components are different, the values ​​measured by the axial force sensor naturally include temperature-induced components, causing the actuator to frequently perform ineffective actions, which reduces work efficiency and shortens the lifespan of the actuator. Summary of the Invention

[0006] This invention provides a method for controlling the axial force of bolts at steel structure nodes based on real-time BIM monitoring, in order to solve the above-mentioned problems.

[0007] A method for controlling the axial force of bolts at steel structure nodes based on real-time monitoring using BIM includes: acquiring the current axial force value of a target high-strength bolt at the steel structure node and calculating the axial force change rate based on the current axial force value; calculating the predicted axial force value of the target bolt after a preset time based on the current axial force value and the axial force change rate; determining that the target high-strength bolt is in a loose state when the predicted axial force value is lower than a preset threshold and applying a first compensating axial force to the target high-strength bolt; acquiring the axial force value of the target bolt again after a preset verification time and determining whether it is less than a preset proportion of the initial preload; if it is less than the preset proportion of the initial preload, reducing the stiffness parameter of the virtual connection unit corresponding to the target high-strength bolt to obtain a stiffness reduction coefficient; calculating the compensating axial force value of adjacent high-strength bolts based on the stiffness reduction coefficient and applying a second compensating axial force to the adjacent high-strength bolts.

[0008] Furthermore, the steps of calculating the axial force change rate and predicting the axial force value also include: obtaining the ambient temperature value at the target high-strength bolt; calculating the temperature-induced axial force component based on the ambient temperature value and the coefficient of thermal expansion of the steel; subtracting the temperature-induced axial force component from the target axial force value to generate the net mechanical axial force value; and calculating the axial force change rate and predicting the axial force value based on the net mechanical axial force value.

[0009] Furthermore, the steps for determining whether the target high-strength bolt is in a loose state include: performing linear fitting on historical axial force data based on the axial force change rate, and calculating the coefficient of determination of the fitting result; statistically analyzing the axial force value of the target high-strength bolt within a preset number of sampling time windows, calculating its coefficient of variation, and taking the reciprocal of the coefficient of variation as a stability index; weighting and fusing the coefficient of determination and the stability index according to preset weighting coefficients to obtain a comprehensive confidence level; and determining that the target high-strength bolt is in a loose state when the predicted axial force value is less than a preset threshold and the comprehensive confidence level is greater than a preset confidence level threshold.

[0010] Furthermore, the stiffness reduction factor is equal to the ratio of the target axial force at the end of the preset verification time to the initial preload.

[0011] Furthermore, the calculation steps for the compensating axial force value include: extracting the initial global stiffness matrix of the steel structure node under the condition of not setting the stiffness reduction factor; applying the stiffness reduction factor to the virtual connection unit to generate the current global stiffness matrix; making the node displacement value under the current global stiffness matrix equal to the node displacement value under the initial global stiffness matrix of the node as the solution condition, and calculating the compensating axial force value required for adjacent high-strength bolts.

[0012] Furthermore, the target high-strength bolt and adjacent high-strength bolts are compensated for axial force using an axial force compensation device.

[0013] Furthermore, the axial force compensation device includes a shape memory alloy drive body and a power supply control module connected to the shape memory alloy drive body. The power supply control module outputs a drive current to the shape memory alloy drive body based on the received axial force compensation command. The shape memory alloy drive body undergoes phase change expansion based on the drive current and outputs the axial force compensation.

[0014] Furthermore, the number of adjacent high-strength bolts is at least two.

[0015] Furthermore, the preset time is 300 to 600 seconds, and the preset verification time is 60 seconds.

[0016] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0017] 1. By setting a stiffness reduction coefficient for the virtual connection unit corresponding to the target high-strength bolt under the condition that the target axial force value is less than the preset ratio of the initial preload, and calculating the compensating axial force value based on the stiffness reduction coefficient, the adjacent axial force compensation device outputs the compensating axial force to the steel structure node under the condition that the target bolt position compensation device fails.

[0018] 2. The step of obtaining the ambient temperature value and calculating the temperature-induced axial force component, and subtracting the temperature-induced axial force component from the target axial force value to generate the net mechanical axial force value, ensures that the data calculated in the prediction and judgment steps excludes data fluctuations caused by temperature expansion.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0022] Figure 1 This is a flowchart of a steel structure node bolt axial force control method based on BIM real-time monitoring disclosed in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of a control system for implementing a BIM-based real-time monitoring method for controlling the axial force of bolts at steel structure nodes, as disclosed in an embodiment of the present invention.

[0024] Figure 3This is a communication block diagram of the control system disclosed in an embodiment of the present invention.

[0025] Figure label:

[0026] 10. Steel structure node; 11. Steel component; 12. Target high-strength bolt; 13. Target axial force sensor; 14. Adjacent high-strength bolt; 15. Adjacent axial force sensor; 20. Wireless communication module; 30. BIM monitoring server; 40. Target axial force compensation device; 50. Adjacent axial force compensation device; 60. Temperature sensor. Detailed Implementation

[0027] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0028] This invention provides a method for controlling the axial force of bolts at steel structure node 10 based on BIM real-time monitoring. The method described in this embodiment relies on a BIM-based real-time monitoring method for controlling the axial force of bolts at steel structure node 10, the structure of which is as follows: Figure 2 and 3 As shown.

[0029] At the structural level, the steel structure node 10 includes a steel member 11 and a plurality of high-strength bolts for connecting and fixing the steel member 11. The plurality of high-strength bolts are spatially arranged as a target high-strength bolt 12 and at least two adjacent high-strength bolts 14 arranged adjacent to the target high-strength bolt 12. Both the target high-strength bolt 12 and the adjacent high-strength bolts 14 are equipped with axial force sensors for acquiring the current axial force value, and both the target high-strength bolt 12 and the adjacent high-strength bolts 14 are equipped with axial force compensation devices for applying mechanical thrust to the surface of the member. The axial force sensor and axial force compensation device installed on the target high-strength bolt 12 are defined as target axial force sensor 13 and target axial force compensation device 40; the axial force sensor and axial force compensation device installed on the adjacent high-strength bolts 14 are defined as adjacent axial force sensor 15 and adjacent axial force compensation device 50. A temperature sensor 60 is also arranged in the environment where the steel structure node 10 is located.

[0030] The axial force compensation device includes a shape memory alloy drive body and a power supply control module connected to the shape memory alloy drive body. The power supply control module outputs a drive current to the shape memory alloy drive body based on the received axial force compensation command. The shape memory alloy drive body undergoes phase change expansion based on the heat generated by the drive current and outputs the axial force compensation.

[0031] At the control level, a BIM monitoring server 30 is installed. The BIM monitoring server 30 internally stores the 3D BIM model data, material physical property data, and connection topology data corresponding to the steel structure node 10. The target axial force sensor 13, adjacent axial force sensors 15, target axial force compensation device 40, adjacent axial force compensation device 50, and temperature sensor 60 are all connected to the BIM monitoring server 30 via a communication module. The BIM monitoring server 30 is configured to acquire and analyze the data collected by the target axial force sensor 13, adjacent axial force sensors 15, and temperature sensor 60, and control the target axial force compensation device 40 and adjacent axial force compensation device 50 to control the bolt axial force of the steel structure node 10.

[0032] The BIM monitoring server 30 continuously acquires axial force data of the target high-strength bolt 12 and adjacent high-strength bolts 14, and calculates the rate of change of axial force and the predicted axial force value of the target high-strength bolt 12. When the BIM monitoring server 30 detects that the predicted axial force value is lower than a preset threshold, it determines that the target high-strength bolt 12 is in a loose state, and sends a single-point compensation command to the target axial force compensation device 40 at the target high-strength bolt 12. The difference between this solution and the prior art is that after issuing the single-point compensation command, the BIM monitoring server 30 performs stiffness reduction calculation under the condition that the physical compensation action at the target high-strength bolt 12 has failed. Based on the stiffness matrix generated by the stiffness reduction calculation, the BIM monitoring server 30 solves the redistribution state of the node internal forces, calculates the required compensation axial force value of the adjacent high-strength bolt 14, and sends an action command to the adjacent axial force compensation device 50 of the adjacent high-strength bolt 14, so that the initial overall stiffness of the steel structure node 10 is maintained through the mechanical action of cluster compensation.

[0033] To eliminate the effects of thermal expansion and contraction of steel structures caused by changes in ambient temperature, the steps of calculating the axial force change rate and predicting the axial force value also include: the BIM monitoring server 30 acquiring the ambient temperature value collected by the temperature sensor 60 at the target high-strength bolt 12; the BIM monitoring server 30 calculating the temperature-induced axial force component based on the ambient temperature value and the coefficient of thermal expansion of the steel; subtracting the temperature-induced axial force component from the target axial force value to generate the net mechanical axial force value; and calculating the axial force change rate and predicting the axial force value based on the net mechanical axial force value.

[0034] like Figure 1 As shown, this embodiment provides a method for controlling the axial force of bolts at a steel structure node 10 based on real-time BIM monitoring, including the following steps:

[0035] S1, obtain the current axial force value of the target high-strength bolt 12 at steel structure node 10, and calculate the axial force change rate based on the current axial force value.

[0036] The current axial force value of the target high-strength bolt 12 is obtained through the target axial force sensor 13. In this embodiment, both the target axial force sensor 13 and the adjacent axial force sensor 15 use piezoresistive strain gauge washers. Simultaneously, the ambient temperature value at the target high-strength bolt 12 is obtained through a temperature sensor 60 installed on the surface of the steel structure node 10. The BIM monitoring server 30 extracts the steel expansion coefficient corresponding to the high-strength bolt and the base material expansion coefficient corresponding to the steel component 11 from the pre-stored database. The BIM monitoring server 30 calculates the temperature-induced axial force component based on the ambient temperature value and the steel expansion coefficient. The calculation process is as follows: In the formula, This refers to the temperature-induced axial force component. The elastic modulus of the bolt material; This represents the effective cross-sectional area of ​​the bolt rod. is the coefficient of linear expansion of the bolt; Let be the coefficient of linear expansion of steel component 11; The current ambient temperature value; The reference ambient temperature at which the initial preload is applied to the bolt.

[0037] The BIM monitoring server 30 subtracts the temperature-induced axial force component from the acquired target axial force value to generate the net mechanical axial force value. The net mechanical axial force value represents the actual structural stress after excluding the physical deformation caused by thermal expansion and contraction.

[0038] S2, based on the current axial force value and the rate of change of axial force, calculate the predicted axial force value of the target bolt after a preset time.

[0039] The BIM monitoring server 30 extracts a time window set before the current moment, such as the time series of continuous net mechanical axial force values ​​within the past 200 seconds, and uses the least squares method for linear fitting to calculate the axial force change rate.

[0040] Subsequently, the BIM monitoring server 30 calculates the predicted axial force value of the target bolt after a preset time based on the current net mechanical axial force value and axial force change rate. In this embodiment, the preset time is set to 300 seconds to 600 seconds, preferably 300 seconds. The calculation process is as follows: In the formula, Predict the axial force value of the target bolt after a preset time; This represents the net mechanical axial force value at the current moment; The axial force change rate is based on least squares fitting. This is the preset time.

[0041] S3, when the predicted axial force value is lower than the preset threshold, it is determined that the target high-strength bolt 12 is in a loose state, and the first compensation axial force is applied to the target high-strength bolt 12.

[0042] After obtaining the predicted axial force value Then, the BIM monitoring server 30 will predict the axial force value. The value is compared to a preset threshold, which, for example, is set to 75% of the initial design preload. This is used to predict the axial force value. Under conditions where the value is below a preset threshold, a comprehensive confidence level calculation is performed.

[0043] When performing linear fitting of historical axial force data based on the axial force change rate, the BIM monitoring server 30 simultaneously calculates the coefficient of determination of the fitting result. Within a preset number of sampling time windows, the net mechanical axial force value of the target high-strength bolt 12 is statistically analyzed, and the ratio of its standard deviation to the mean is calculated to obtain the coefficient of variation. The BIM monitoring server 30 takes the reciprocal of the coefficient of variation as a stability index. The BIM monitoring server 30 weights and fuses the coefficient of determination and the stability index according to preset weighting coefficients to obtain the comprehensive confidence level. The calculation expression is: In the formula, For overall confidence level; To determine the preset weight of the coefficient, this embodiment uses 0.6; The preset weight for the stability index is 0.4 in this embodiment; The coefficients of determination for the linear fit; This represents the average value of the net mechanical axial force within the sampling time window. This represents the standard deviation of the net mechanical axial force values ​​within the sampling time window.

[0044] When the predicted axial force value is less than the preset threshold, and the overall confidence level is... If the value exceeds the preset confidence threshold, for example, the preset confidence threshold is set to 0.85, and the BIM monitoring server 30 determines that the target high-strength bolt 12 is in a loose state.

[0045] After determining that the bolt is loose, the BIM monitoring server 30 sends a compensation axial force command to the target axial force compensation device 40 at the target high-strength bolt 12.

[0046] The axial force compensation device includes a shape memory alloy actuator and a power supply control module connected to the shape memory alloy actuator. In one embodiment, the shape memory alloy actuator is made of nickel-titanium shape memory alloy and is fabricated as a ring-shaped pad structure with an internal heating resistance wire. The power supply control module includes a pulse width modulation controller and a high-power solid-state relay.

[0047] Based on the received compensation axial force command, the power supply control module outputs a preset intensity of drive current to the heating resistance wire inside the shape memory alloy drive body. The shape memory alloy drive body, based on the Joule heat generated by the current, raises its temperature above the phase transition temperature, causing phase transition expansion. Under the condition of being physically constrained by the nut and the steel component 11, the phase transition expansion is converted into a thrust along the bolt axis, that is, the output of the first compensation axial force.

[0048] S4. After the preset verification time, obtain the axial force value of the target bolt again and determine whether it is less than the preset ratio of the initial preload.

[0049] After the BIM monitoring server 30 issues a compensation axial force command, an internal timer is started. After a preset verification time, the BIM monitoring server 30 acquires the axial force value of the target bolt again. In this embodiment, the preset verification time is set to 60 seconds to cover the phase change response delay time of the shape memory alloy drive body. The BIM monitoring server 30 determines whether the axial force value of the target bolt acquired at 60 seconds is less than a preset proportion of the initial preload. In this embodiment, the preset proportion is set to 80%. If the axial force value of the target bolt is greater than or equal to 80% of the initial preload, the single-point physical compensation is deemed successful, and the process ends. If the axial force value of the target bolt is less than 80% of the initial preload, the actuator at the target high-strength bolt 12 is deemed to be abnormal, such as jamming, breakage, or thermal failure causing the compensation action to fail to meet the standard.

[0050] S5, if it is less than the preset ratio of the initial preload, then the stiffness parameter of the virtual connection unit corresponding to the target high-strength bolt 12 is reduced to obtain the stiffness reduction coefficient.

[0051] After determining that physical compensation has failed, the BIM monitoring server 30 stops sending drive commands to the target high-strength bolt 12. The BIM monitoring server 30 retrieves the virtual connection unit corresponding to the target high-strength bolt 12 from its internal BIM model. The virtual connection unit is represented in the BIM model as a spring-damped model containing stiffness parameters.

[0052] The BIM monitoring server 30 reduces the stiffness parameters of the virtual connection unit corresponding to the target high-strength bolt 12 to obtain a stiffness reduction coefficient. The value of the stiffness reduction coefficient is equal to the ratio of the target axial force value to the initial preload at the preset verification time endpoint. The calculation expression is: In the formula, This is the stiffness reduction factor; The target axial force value is obtained at the end of the preset verification time of 60 seconds. The initial preload design value for the target high-strength bolt 12.

[0053] S6. Based on the stiffness reduction factor, calculate the compensating axial force value of the adjacent high-strength bolt 14, and apply a second compensating axial force to the adjacent high-strength bolt 14.

[0054] The BIM monitoring server 30 calculates the compensating axial force values ​​for at least two adjacent high-strength bolts 14 based on the stiffness reduction factor. The specific calculation steps include:

[0055] First, the initial global stiffness matrix of steel structure node 10 is extracted under the condition that no stiffness reduction factor is set.

[0056] Secondly, a stiffness reduction factor is applied to the virtual connection unit to generate the current global stiffness matrix after modifying the local parameters.

[0057] Subsequently, a finite element equilibrium equation is constructed to ensure that the nodal displacements under the current global stiffness matrix are equal to the nodal displacements under the initial global stiffness matrix, which is the solution condition. The calculation expression is as follows:

[0058]

[0059]

[0060] In the formula, This is the initial global stiffness matrix; The nodal displacement vectors under the initial global stiffness matrix; The vector of external loads borne by the node; The current global stiffness matrix generated by applying the stiffness reduction factor; This is the vector of compensating axial force values ​​required for the adjacent high-strength bolts 14.

[0061] extract The force component parallel to the axis of the adjacent high-strength bolt 14 in the vector is distributed according to the lever arm ratio of the positions of each adjacent high-strength bolt 14 through the mechanical equilibrium distribution matrix, thereby generating the compensating axial force value corresponding to each adjacent high-strength bolt 14.

[0062] The BIM monitoring server 30 calculates the required compensating axial force vector for adjacent high-strength bolts 14 while maintaining the node displacement vector unchanged. Finally, the BIM monitoring server 30 generates a second compensation command containing the compensating axial force value and sends it to the adjacent axial force compensation devices 50 located at at least two adjacent high-strength bolts 14. The power supply control module within the adjacent axial force compensation device 50 calculates the matching target driving current based on the compensating axial force value and outputs current to the corresponding shape memory alloy actuators. Specifically, this calculation step includes: the system pre-stores the driving current-phase change thrust calibration curves of the shape memory alloy actuators at different ambient temperatures, and the power supply control module obtains the matching target driving current based on these curves. The shape memory alloy actuators at the adjacent high-strength bolts 14 undergo phase change expansion, applying a second compensating axial force to the steel structure node 10, thus restoring the overall anti-slip capability of the node to the design requirements.

[0063] The target axial force compensation device 40 and the adjacent axial force compensation device 50 have the same structure. To avoid false triggering of phase transformation in the shape memory alloy actuator due to increased ambient temperature caused by outdoor exposure in summer, the shape memory alloy actuator is made of high-temperature shape memory alloy material, such as a nickel-titanium based high-temperature shape memory alloy doped with palladium, hafnium, or zirconium. Its austenitic phase transformation initiation temperature is set above 85℃, preferably 100℃~120℃, to ensure that under extreme climate conditions, the phase transformation can only be triggered by Joule heating from the drive current output by the power supply control module.

[0064] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0065] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0066] Those skilled in the art will also understand that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments herein can be implemented as electronic hardware, computer software, or a combination thereof. To clearly illustrate the interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps described above are generally described in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in alternative ways for each specific application; however, such implementation decisions should not be construed as departing from the scope of this disclosure.

[0067] The steps of the methods or algorithms described in conjunction with the embodiments herein can be directly embodied in hardware, software modules executed by a processor, or a combination thereof. The software modules can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal. Alternatively, the processor and storage medium can exist as discrete components in the user terminal.

[0068] For software implementation, the techniques described in this application can be implemented using modules (e.g., procedures, functions, etc.) that perform the functions described in this application. This software code can be stored in memory units and executed by a processor. The memory units can be implemented within the processor or outside the processor; in the latter case, they are communicatively coupled to the processor via various means, as is well known in the art.

[0069] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that the various embodiments can be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

Claims

1. A method for controlling the axial force of bolts at steel structure nodes based on real-time BIM monitoring, characterized in that, include: Obtain the current axial force value of the target high-strength bolt at the steel structure node, and calculate the axial force change rate based on the current axial force value; Based on the current axial force value and the rate of change of axial force, calculate the predicted axial force value of the target bolt after a preset time. When the predicted axial force value is lower than the preset threshold, it is determined that the target high-strength bolt is in a loose state, and a first compensation axial force is applied to the target high-strength bolt; After the preset verification time, the axial force value of the target bolt is obtained again, and it is determined whether it is less than the preset ratio of the initial preload. If it is less than the preset ratio of the initial preload, the stiffness parameter of the virtual connection unit corresponding to the target high-strength bolt is reduced to obtain the stiffness reduction coefficient. Based on the stiffness reduction factor, the compensating axial force value of adjacent high-strength bolts is calculated, and a second compensating axial force is applied to the adjacent high-strength bolts.

2. The method as described in claim 1, characterized in that, The steps for calculating the axial force change rate and predicting the axial force value also include: obtaining the ambient temperature value at the target high-strength bolt; calculating the temperature-induced axial force component based on the ambient temperature value and the coefficient of thermal expansion of the steel; subtracting the temperature-induced axial force component from the target axial force value to generate the net mechanical axial force value; and calculating the axial force change rate and predicting the axial force value based on the net mechanical axial force value.

3. The method as described in claim 1, characterized in that, The steps to determine if a target high-strength bolt is loose include: Linear fitting was performed on historical axial force data based on the rate of change of axial force, and the coefficient of determination of the fitting result was calculated. Within a preset number of sampling time windows, the axial force values ​​of the target high-strength bolts are statistically analyzed, their coefficient of variation is calculated, and the reciprocal of the coefficient of variation is taken as a stability index. The determination coefficient and stability index are weighted and fused according to the preset weighting coefficients to obtain the comprehensive confidence level; If the predicted axial force is less than the preset threshold and the overall confidence level is greater than the preset confidence level threshold, the target high-strength bolt is determined to be in a loose state.

4. The method as described in claim 1, characterized in that, The stiffness reduction factor is equal to the ratio of the target axial force at the end of the preset verification time to the initial preload.

5. The method as described in claim 1, characterized in that, The calculation steps for the compensating axial force value include: Extract the initial global stiffness matrix of the steel structure nodes without setting a stiffness reduction factor; Apply stiffness reduction factors to the virtual connection elements to generate the current global stiffness matrix; The solution condition is to make the nodal displacement values ​​under the current global stiffness matrix equal to the nodal displacement values ​​under the initial global stiffness matrix of the nodes, and to calculate the compensating axial force values ​​required for adjacent high-strength bolts.

6. The method as described in claim 1, characterized in that, The target high-strength bolt and adjacent high-strength bolts are compensated for axial force using an axial force compensation device.

7. The method as described in claim 6, characterized in that, The axial force compensation device includes a shape memory alloy drive body and a power supply control module connected to the shape memory alloy drive body. The power supply control module outputs a drive current to the shape memory alloy drive body based on the received axial force compensation command. The shape memory alloy drive body undergoes phase change expansion based on the drive current and outputs the axial force compensation.

8. The method as described in claim 1, characterized in that, The number of adjacent high-strength bolts must be at least two.

9. The method as described in claim 1, characterized in that, The preset time is 300 to 600 seconds, and the preset verification time is 60 seconds.

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