Fire mixed test method for angle steel transmission tower structure

Abstract

The application discloses a kind of angle steel transmission tower structure fire mixed test method, comprising the following steps: transmission tower is divided into physical and numerical substructure, determine the wild fire heating mode of tower leg part;Then build finite element model to carry out normal temperature static force calculation, establish initial stress field for two substructures;After ignition test, in the set discretization time increment, real-time acquisition physical substructure top displacement data under fire, and as boundary condition input numerical model;Subsequently, the bottom update counterforce obtained by numerical simulation is reversely transmitted to the control system to update the vertical load of the actuator on the physical substructure;Continue to circulate displacement-counterforce dynamic interactive loading until the end of the test, finally obtain temperature distribution pattern and displacement time history curve, the application can restore the collapse behavior of tower leg local fire under the constraint of tower body, and ensure the consistency of calculation efficiency and real structure mechanical behavior.

Description

Technical Field

[0001] This invention relates to a mixed fire test method for angle steel transmission tower structures, belonging to the field of structural fire resistance testing technology. Background Technology

[0002] In modern society, power transmission networks are a solid foundation for life and the economy. Lattice-type angle steel transmission towers play a crucial role in the construction and operation of power grid systems; therefore, these towers must be appropriately designed to meet load-bearing requirements and mitigate the impact of extreme weather events. However, transmission towers are often built in forested or wasteland areas, which are highly susceptible to wildfires under current extreme weather conditions. Fires severely affect the mechanical properties of the structure, damage its integrity, and cause tower collapse. Therefore, it is necessary to employ various methods to study the overall response of structures under fire conditions to improve the theoretical advancement of structural fire protection design and the ability to assess fire resistance performance, thereby reducing or avoiding significant casualties and property losses.

[0003] Currently, there are two main analytical methods for analyzing the fire response of angle steel transmission towers: numerical simulation based on finite element software and thermo-mechanical coupling tests based on field testing. In numerical simulation, calculations are typically performed after assuming the thermal parameters of key tower components and the interaction parameters of thermal convection and radiation in the components, followed by result analysis and discussion. However, due to the strong nonlinearity that structures may exhibit during fires, the predicted temperature rise mode and structural mechanical behavior differ significantly from actual conditions, thus failing to accurately reflect the core mechanisms of structural collapse or failure. In thermo-mechanical coupling field testing, experimental studies primarily focus on full-scale and scaled-down tower legs or angle steel components, and the loading mode is usually based on external forces corresponding to a constant load ratio. This makes it difficult to effectively consider the boundary constraint effects of non-fire-affected parts on fire-affected parts, as well as the influence of structural force redistribution, thus hindering the effective guidance of experimental conclusions for structural fire protection engineering and technology development. Therefore, combining numerical simulation methods with thermo-mechanical coupling field testing into a hybrid fire test is an effective way to simulate the overall fire response of a structure. However, current limitations exist in hybrid fire resistance tests for angle steel transmission towers. 1. Unlike all nodes or components affected by fire, the tower legs are locally affected by wildfire, exhibiting extremely rapid temperature rise and fall, while the tower body is less affected by temperature. This is significantly different from existing numerical and physical substructure analysis methods that consider the impact of temperature.

[0004] 2. Hybrid testing of angle steel transmission towers is relatively insufficient. Compared with the well-established theoretical system of steel frame structures, the interaction method between the boundary conditions applied to the physical substructures and external loads in angle steel transmission towers is currently unclear. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a mixed test method for fire in angle steel transmission tower structures.

[0006] To solve the above-mentioned technical problems, this invention proposes a method for mixed fire testing of angle steel transmission tower structures, comprising the following steps: S1: Divide the angle steel transmission tower structure to be analyzed into a physical substructure and a numerical substructure; S2: Based on the physical substructure, determine the heating tower leg part in the tower leg corresponding to the physical substructure, and determine that the fire treatment method is wildfire heating; S3: Based on the numerical substructure and the full structure to be analyzed, construct the full structure finite element model of the angle steel transmission tower and the numerical substructure model corresponding to the numerical substructure; perform room temperature static loading calculation based on the full structure finite element model to obtain the bottom support reaction force and structural displacement, and based on the bottom support reaction force and structural displacement, establish the room temperature static load stress field and initial stress in the numerical substructure model and the physical substructure respectively; S31. Based on the constructed finite element model of the angle steel transmission tower, the bottom support reaction force f0 and structural displacement are obtained by combining loads and performing static loading calculations at room temperature. The top displacement of the main tower leg is applied to the bottom of the numerical substructure, and the remaining degrees of freedom are kept constrained to obtain the stress field distribution of the substructure under static loading conditions at room temperature. S32. Change the reaction force of the bottom support of the structure to -f0 and transmit the data to the Openfresco port through ABAQUS; the Openfresco port transmits the load data -f0 to the LabVIEW control system and sends instructions to each corresponding actuator to simulate the effect of static loading at room temperature, so that the initial stress is generated inside each component of the physical substructure. In S32, Openfresco-ABAQUS-LabVIEW completes load signal interaction in the load data transmission process by transforming between global coordinates, local coordinates, and cantilever coordinates. The specific formula for the relationship between the cantilever and local coordinates is as follows:

[0007] Where F1 is the load along the axial direction of the main tower leg member, F2 is the load along the normal direction of the main tower leg member, F3 is the moment along the rotation direction of the main tower leg member, d1 is the projected length of the main tower leg member under deformation conditions along the bottom rotation condition in the local coordinate system, d2 is the projected height of the deformation at the top of the main tower leg member in the direction after deformation in the local coordinate system, and L is the axial deformation of the main tower leg member. The specific formula for transforming local and global coordinate systems is as follows:

[0008] Wherein, Ln is the original length of the main tower leg member, u4 is the horizontal displacement of the top of the main tower leg member in the overall coordinate system, u1 is the horizontal displacement of the bottom of the main tower leg member in the overall coordinate system, u2 is the vertical displacement of the bottom of the main tower leg member, and u5 is the vertical displacement of the top of the main tower leg member. S4: Based on the determined fire exposure method and the physical substructure with established initial stress, set up a fire scene ambient temperature detection system and a wildfire source, and ignite the wildfire source to start a fire mixing test; S5: During the fire mixing test, within the set discretization time increment, the displacement change data of the top of the physical substructure after being exposed to fire is obtained, the displacement change data is converted into displacement update values, and these values ​​are input as boundary conditions into the numerical substructure model in S3 to activate a new analysis step for numerical simulation calculation. In S5, the OpenFresco to ABAQUS to LabVIEW displacement data transmission process achieves complete signal transmission through mutual transformation between the global coordinate system, the local coordinate system, and the cantilever coordinate system. The specific formula for the relationship between the global coordinate system and the local coordinate system is as follows:

[0009] Where u1 is the horizontal displacement of the bottom of the main tower leg member, u4 is the horizontal displacement of the top of the main tower leg member, u2 is the vertical displacement of the bottom of the main tower leg member, u5 is the vertical displacement of the top of the main tower leg member, u3 is the bottom corner of the tower leg, u6 is the top corner of the tower leg, and L is the height of the tower leg. The specific formula relating the local coordinate system and the cantilever coordinate system is as follows:

[0010] Where q2 and q3 are the bottom and top corners of the main tower leg member, respectively; q1 is the vertical displacement of the top of the main tower leg member; and L is the height of the tower leg. S6: Based on the results of the numerical simulation calculation described in S5, the updated reaction force at the bottom of the numerical substructure is obtained, the updated reaction force is transmitted in the reverse direction to the control system, and the vertical load applied to the physical substructure by the actuator is updated based on the updated reaction force. S7: Based on the set discretization time increment, S5 and S6 are executed sequentially to cause the displacement update of the physical substructure and the reaction force update of the numerical substructure to continuously interact until the test termination condition is met and loading is stopped. S8: Based on the entire test process, the wildfire space temperature distribution pattern is obtained through the fire environment temperature detection system, and the displacement and time history curves of the key parts of the physical substructure are obtained through the control system.

[0011] The optional parts of the heating tower leg section mentioned in S2 above include: a single leg, a first pair of legs, a second pair of legs, or a triple leg; wherein, the direction of the first pair of legs is parallel to the direction of the crossbeam, and the direction of the second pair of legs is perpendicular to the direction of the crossbeam; the first pair of legs and the second pair of legs respectively represent the spread trend of wildfire in two orthogonal directions; the direction of the triple leg represents the spread trend of wildfire in the diagonal direction of the tower leg.

[0012] The above describes how, when constructing analysis steps in ABAQUS, Python scripts are used to generate analysis steps corresponding to the discretized time in batches. First, keep analysis step 1. For the remaining analysis steps, set the restart option and then disable it. First, set the frequency to 1 on the right side of each analysis step option in the edit restart request, then define the interval to 0, and finally click OK in the overlay box to achieve the initial restart setting goal. Meanwhile, in analysis step-2, both the data reading and analysis step name are set to analysis step-1, and then all analysis steps after analysis step-1 are set to disabled.

[0013] In S32 above, user-defined elements (UEL) and user subroutines (VUEL) are added to ABAQUS to enable network-based data transmission with the experimental elements in Openfresco. When constructing the UEL custom element, a communication port is first defined to enable data communication. When defining material parameters, the computer port number used for communication is entered, and port 8080 is selected as the communication port. When submitting the calculation task, the corresponding element subroutine file is called through the subroutine call port in the interface, and the element subroutine socket statement is written to realize the data transmission and reception function between ABAQUS and Openfresco.

[0014] In S32 above, the data transmission channel between OpenFresco and LabVIEW is constructed based on the TCP / IP channel for interaction; During the construction process, the Controldaemon (NTCP) plugin of the NEESDA package is used to implement data exchange between LabVIEW and OpenFresco in ASCII code via TCP connection.

[0015] The aforementioned S6 specifically includes: After the displacement input, the calculation continues in a new analysis step. The restart command is used to inherit the deformation results of the numerical substructure under the normal temperature static state. After the calculation, the updated reaction force at the bottom of the ABAQUS numerical substructure is obtained, which is modified into a reverse force and transmitted to the OpenFresco port and the LabVIEW control system. At the same time, the vertical load of the actuator is updated.

[0016] In S7 above, the height of the tower leg physical substructure is H, and the vertical displacement values ​​of each actuator in the physical substructure satisfy the following relationship, then the test ends:

[0017] Where dT-i is the displacement value corresponding to the top of the main material of the four tower legs of the physical substructure.

[0018] This invention has positive effects: This invention employs a novel substructure segmentation and loading method. It rapidly acquires the displacement variables at the top of the physical substructure using LabVIEW signal transmission and quickly transmits these variables back to the numerical substructure via an OpenFresco-ABAQUS port. The updated load response values ​​are then calculated using a finite element model and returned to the actuator at the top of the tower leg of the physical substructure via the original path, thus achieving dynamic transfer of key mechanical parameters between the physical and numerical substructures. Based on this overall design, the collapse evolution of locally heated components of a transmission tower under wildfire conditions and tower constraints was successfully realized. Furthermore, this invention directly utilizes existing port technology and finite element software, ensuring both testing accuracy and consistency between the experimental and actual structural mechanical behavior. Moreover, no new numerical substructure finite element model or algorithm was developed, facilitating direct operation and modeling analysis, effectively saving time and debugging costs for model development and debugging. This provides superior convenience for hybrid experimental analysis of power grid structures. Attached Figure Description

[0019] The method for mixed fire testing of angle steel transmission tower structures according to the present invention will be further explained below with reference to the accompanying drawings.

[0020] Figure 1 This is a flowchart illustrating this embodiment; Figure 2 This is a schematic diagram of the NTCP data interaction process in this embodiment; Figure 3 This is a schematic diagram illustrating the displacement transformation between the global and local coordinate systems in this embodiment; Figure 4 This is a schematic diagram illustrating the displacement transformation between the local and cantilever coordinate systems in this embodiment; Figure 5 This is a schematic diagram illustrating the transformation of the load between the local and global coordinate systems in this embodiment; Figure 6 This is a schematic diagram of the load transformation between the cantilever and the local coordinate system in this embodiment. Detailed Implementation

[0021] Example See Figures 1 to 6 The fire mixed test method for angle steel transmission tower structures according to an embodiment of the present invention specifically includes the following steps: S1. Divide the angle steel transmission tower structure to be analyzed into a physical substructure and a numerical substructure. S2. Determine the heating tower leg sections corresponding to the physical substructure: single leg, first double leg, second double leg, and triple leg. The fire treatment method is wildfire heating, and the heating time is 180s; fabricate the main tower leg materials, diagonal members, and struts required for the physical substructure, and assemble the loading reaction space frame simultaneously; S3. Deploy a wildfire fire site air temperature testing system and arrange thermocouples for temperature measurement and control points in the physical substructure. S31. Establish the ABAQUS full-structure finite element model of the angle steel transmission tower, calculate the structural support reaction force f0 and the overall structural deformation under normal temperature static load conditions, and record the vertical deformation value u3 at the top of the main tower leg material. S32. Establish an ABAQUS numerical substructure model of the angle steel transmission tower. Use a Python script to construct analysis steps Step-1 to Step-360, where the time increment is defined as Δt = 0.5s. Then, for each analysis step, in the restart settings, select: frequency 1, then define the interval as 0, and finally click OK in the overlay box to achieve the initial restart setting goal. Simultaneously, only retain Step-1, and disable Step-2 to Step-360. Step-1 Analysis: Apply the top deformation uZ of the main tower leg member in the full model to the bottom of the model and keep uX=uY=urX=urY=urZ=0 (ui are the translational degrees of freedom in the X, Y, and Z axes, and uri are the rotational degrees of freedom in the X, Y, and Z axes, respectively). Perform static room temperature state calculations to form the initial stress field of the numerical substructure. The support reactions calculated from the ABAQUS full-structure finite element model are converted into -f0 and transmitted to the OpenFresco control system via port communication. Considering the implicit solution method used, a UEL user element is established, and a communication port is defined to realize data communication. *USER ELEMENT, TYPE=Un, NODES=m, COORDINATES=a, PROPERTIES=b, IPROPERTIES =c,VARIABLES=d, unsymm Then, by specifying the nodal degrees of freedom and element properties, the response values ​​and commands for displacement and reaction forces are transmitted: *element, type=**, elset=** *uel property,elset=** Furthermore, when connecting, port 8080 in the TCP / IP protocol is selected as the communication port. After the communication port and material unit are set, socket statements are used to realize the data transmission and reception function between ABAQUS and OpenFresco. After receiving the load data, OpenFresco transmits it to LabVIEW and converts it into load signals, which are then applied to the actuators in the physical substructure. Simultaneously, it records the vertical displacement value d0 of the actuators under load conditions. During the transmission process, an NTCP loop is used to achieve data interaction between LabVIEW and OpenFresco: first, a session is opened (opensession); second, parameters are set (set parameter); and third, parameters are returned (get-parameter). Then, the following operations are performed in a loop: parsing the control point name and related parameters; verifying the preset actuator information in the loading proposal and control program, and providing feedback on the verification result (propose); then executing the loading scheme (execute); and finally, providing feedback on the data acquisition result (get-control-point). By executing these steps, data interaction and feedback results are achieved. According to one embodiment of the present invention, in order to realize the data interaction process between ABAQUS and Openfresco, the load variables need to undergo coordinate system transformation: For loads, the transformation between the local and global coordinate systems is as follows, and the schematic diagram of the load transformation relationship between the local and global coordinate systems is shown below. Figure 5 As shown:

[0022] In the formula, Ln is the original length of the main tower leg member, u4 is the horizontal displacement of the top of the main tower leg member in the global coordinate system, u1 is the horizontal displacement of the bottom of the main tower leg member in the global coordinate system, the tower leg is fixed, u1=0; u2 and u5 are the vertical displacements of the bottom and top of the main tower leg member, respectively, usually u2=0.

[0023] According to an embodiment of the present invention, in step S9, in order to realize the data interaction process between Openfresco and LabVIEW, the load variables are further transformed into coordinate systems: S91, For loads, the transformation between the local coordinate system and the cantilever coordinate system is as follows, and the schematic diagram of the load transformation relationship between the cantilever and local coordinate systems is shown below. Figure 6 As shown:

[0024] In the formula, F1 is the load along the axial direction of the main tower leg member, F2 is the load along the normal direction of the main tower leg member, and F3 is the torque along the rotation direction of the main tower leg member. It should be noted that the units of F1 and F2 are force k0N, and the unit of F3 is torque kN·m.

[0025] d1 is the projected length of the main tower leg member in the local coordinate system under the condition of no deformation along the bottom corner condition, d2 is the projected height of the deformation of the top of the main tower leg member in the local coordinate system in the direction after the deformation of the main tower leg member, and L is the axial deformation of the main tower leg member. S4. Ignite the ignition source and conduct a fire mixing test: S5. Within the time increment Δt=0.5s, the displacement measurement values ​​of each actuator sensor at the top of the physical substructure increase from d0 to d1. The increased vertical displacement d1 is transmitted to the Openfresco system through LabVIEW and converted into a displacement update value, which is then input into the boundary conditions of the ABAQUS numerical substructure finite element model. At the same time, Step-2 is activated. According to one embodiment of the present invention, in order to realize the data interaction process of LabVIEW-Openfresco-ABAQUS, the displacement variables need to undergo coordinate system transformation: S111, for the transition between LabVIEW and Openfresco, the transformation between the cantilever coordinate system and the local coordinate system is performed as follows, and the displacement transformation between the cantilever and local coordinate systems is illustrated as follows. Figure 4 As shown:

[0026] In the formula, q2 and q3 represent the bottom and top rotation angles of the main tower leg member, respectively; q1 represents the vertical displacement of the top of the main tower leg member; and L represents the tower leg height. Then, for Openfresco and ABAQUS, the transformation between the local and global coordinate systems is performed as follows, illustrated in the diagram below. Figure 3 As shown:

[0027] In the formula, u1 and u4 are the horizontal displacements of the bottom and top of the main tower leg material, usually u1=0; u2 and u5 are the vertical displacements of the bottom and top of the main tower leg material, usually u2=0; u3 and u6 are the rotation angles of the bottom and top of the tower leg, and L is the height of the tower leg.

[0028] S6. Using a Python script, import d1 into the load conditions of Step-2, edit the model attribute, select restart analysis step and read the input from file Step-1 to complete the restart file inheritance purpose; and generate a new job Step-2 to perform numerical substructure model calculation after vertical displacement update, obtain bottom reaction force update value f1 and numerical substructure stress field distribution; then, convert it to -f1 and pass it to the Openfresco port and LabVIEW control system, while updating the actuator vertical load from -f0 to -f1; S7. In the initial stage corresponding to each time increment Δt=0.5s, repeat the above steps S5 and S6 in sequence, while the displacement, analysis step code and load are gradually updated from d1, Step-2, f1 to dn, Step-n, fn (n is a positive integer); The height of the tower leg physical substructure is H. The test ends when the vertical displacement values ​​of each actuator in the physical substructure satisfy the following relationship:

[0029] In the formula, dT-i represents the displacement value corresponding to the top of the main members of the four tower legs of the physical substructure. S8. The wildfire space temperature distribution pattern is obtained through the fire temperature detection system; the displacement-time history curve of the top of the main material of the physical substructure tower leg is obtained through the LabVIEW control system. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

[0030] Obviously, the above embodiments are merely examples to clearly illustrate the embodiments of the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, these obvious variations or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims

1. A mixed fire test method for angle steel transmission tower structures, characterized in that, Includes the following steps: S1: Divide the angle steel transmission tower structure to be analyzed into a physical substructure and a numerical substructure; S2: Based on the physical substructure, determine the heating tower leg part in the tower leg corresponding to the physical substructure, and determine that the fire treatment method is wildfire heating; S3: Based on the numerical substructure and the full structure to be analyzed, construct the full structure finite element model of the angle steel transmission tower and the numerical substructure model corresponding to the numerical substructure; perform room temperature static loading calculation based on the full structure finite element model to obtain the bottom support reaction force and structural displacement, and based on the bottom support reaction force and structural displacement, establish the room temperature static load stress field and initial stress in the numerical substructure model and the physical substructure respectively; S31. Based on the constructed finite element model of the angle steel transmission tower, the bottom support reaction force f0 and structural displacement are obtained by combining loads and performing static loading calculations at room temperature. The top displacement of the main tower leg is applied to the bottom of the numerical substructure, and the remaining degrees of freedom are kept constrained to obtain the stress field distribution of the substructure under static loading conditions at room temperature. S32. Change the reaction force of the bottom support of the structure to -f0 and transmit the data to the Openfresco port through ABAQUS; the Openfresco port transmits the load data -f0 to the LabVIEW control system and sends instructions to each corresponding actuator to simulate the effect of static loading at room temperature, so that the initial stress is generated inside each component of the physical substructure. In S32, Openfresco-ABAQUS-LabVIEW completes load signal interaction in the load data transmission process by transforming between global coordinates, local coordinates, and cantilever coordinates. The specific formula for the relationship between the cantilever and local coordinates is as follows: Where F1 is the load along the axial direction of the main tower leg member, F2 is the load along the normal direction of the main tower leg member, F3 is the moment along the rotation direction of the main tower leg member, d1 is the projected length of the main tower leg member under deformation conditions along the bottom rotation condition in the local coordinate system, d2 is the projected height of the deformation at the top of the main tower leg member in the direction after deformation in the local coordinate system, and L is the axial deformation of the main tower leg member. The specific formula for transforming local and global coordinate systems is as follows: Wherein, Ln is the original length of the main tower leg member, u4 is the horizontal displacement of the top of the main tower leg member in the overall coordinate system, u1 is the horizontal displacement of the bottom of the main tower leg member in the overall coordinate system, u2 is the vertical displacement of the bottom of the main tower leg member, and u5 is the vertical displacement of the top of the main tower leg member. S4: Based on the determined fire exposure method and the physical substructure with established initial stress, set up a fire scene ambient temperature detection system and a wildfire source, and ignite the wildfire source to start a fire mixing test; S5: During the fire mixing test, within the set discretization time increment, the displacement change data of the top of the physical substructure after being exposed to fire is obtained, the displacement change data is converted into displacement update values, and these values ​​are input as boundary conditions into the numerical substructure model in S3 to activate a new analysis step for numerical simulation calculation. In S5, the OpenFresco to ABAQUS to LabVIEW displacement data transmission process achieves complete signal transmission through mutual transformation between the global coordinate system, the local coordinate system, and the cantilever coordinate system. The specific formula for the relationship between the global coordinate system and the local coordinate system is as follows: Where u1 is the horizontal displacement of the bottom of the main tower leg member, u4 is the horizontal displacement of the top of the main tower leg member, u2 is the vertical displacement of the bottom of the main tower leg member, u5 is the vertical displacement of the top of the main tower leg member, u3 is the bottom corner of the tower leg, u6 is the top corner of the tower leg, and L is the height of the tower leg. The specific formula relating the local coordinate system and the cantilever coordinate system is as follows: Where q2 and q3 are the bottom and top corners of the main tower leg member, respectively; q1 is the vertical displacement of the top of the main tower leg member; and L is the height of the tower leg. S6: Based on the results of the numerical simulation calculation described in S5, the updated reaction force at the bottom of the numerical substructure is obtained, the updated reaction force is transmitted in the reverse direction to the control system, and the vertical load applied to the physical substructure by the actuator is updated based on the updated reaction force. S7: Based on the set discretization time increment, S5 and S6 are executed sequentially to cause the displacement update of the physical substructure and the reaction force update of the numerical substructure to continuously interact until the test termination condition is met and loading is stopped. S8: Based on the entire test process, the wildfire space temperature distribution pattern is obtained through the fire environment temperature detection system, and the displacement and time history curves of the key parts of the physical substructure are obtained through the control system.

2. The fire mixed test method for angle steel transmission tower structures according to claim 1, characterized in that, The optional parts of the heating tower leg section described in S2 include: a single leg, a first pair of legs, a second pair of legs, or a triple leg; wherein, the direction of the first pair of legs is parallel to the direction of the crossbeam, and the direction of the second pair of legs is perpendicular to the direction of the crossbeam; the first pair of legs and the second pair of legs respectively represent the spread trend of wildfire in two orthogonal directions; the direction of the triple leg represents the spread trend of wildfire in the diagonal direction of the tower leg.

3. The fire mixed test method for angle steel transmission tower structures according to claim 1, characterized in that, When constructing analysis steps in ABAQUS, Python scripts are used to generate analysis steps corresponding to discretized times in batches. First, keep analysis step 1. For the remaining analysis steps, set the restart option and then disable it. First, set the frequency to 1 on the right side of each analysis step option in the edit restart request, then define the interval to 0, and finally click OK in the overlay box to achieve the initial restart setting goal. Meanwhile, in analysis step-2, both the data reading and analysis step name are set to analysis step-1, and then all analysis steps after analysis step-1 are set to disabled.

4. The method for mixed fire testing of angle steel transmission tower structures according to claim 1, characterized in that, In S32, user-defined elements (UEL) and user subroutines (VUEL) are added to ABAQUS to enable network-based data transmission with experimental elements in Openfresco. When constructing the UEL custom element, a communication port is first defined to enable data communication. When defining material parameters, the computer port number used for communication is entered, and port 8080 is selected as the communication port. When submitting the calculation task, the corresponding element subroutine file is called through the subroutine call port in the interface. The element subroutine socket statement is written to realize the data transmission and reception function between ABAQUS and Openfresco.

5. The method for mixed fire testing of angle steel transmission tower structures according to claim 1, characterized in that, In S32, the data transmission channel between OpenFresco and LabVIEW is built based on the TCP / IP channel for interaction; During the construction process, the Controldaemon (NTCP) plugin of the NEESDA package is used to implement data exchange between LabVIEW and OpenFresco in ASCII code via TCP connection.

6. The method for mixed fire testing of angle steel transmission tower structures according to claim 1, characterized in that, S6 specifically includes: After the displacement input, the calculation continues in a new analysis step. The restart command is used to inherit the deformation results of the room temperature static state from the numerical substructure. After the calculation, the updated reaction force at the bottom of the ABAQUS numerical substructure is obtained, which is modified into a reverse force and transmitted to the OpenFresco port and the LabVIEW control system. At the same time, the vertical load of the actuator is updated.

7. The method for mixed fire testing of angle steel transmission tower structures according to claim 1, characterized in that, In S7, the height of the tower leg physical substructure is H. If the vertical displacement values ​​of each actuator in the physical substructure satisfy the following relationship, then the test ends: Where dT-i is the displacement value corresponding to the top of the main material of the four tower legs of the physical substructure.

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