Teaching system and teaching method for stress simulation by using temperature change of steel structure

Abstract

The invention relates to a teaching system and a teaching method for stress simulation by using temperature change of a steel structure, and belongs to the technical field of teaching equipment. The teaching system comprises a reaction frame, auxiliary frames, a jack, a detection mechanism, a heating mechanism and a cooling mechanism, the reaction frame is of a vertically-arranged square frame structure, the multiple auxiliary frames and the reaction frame are arranged in a staggered mode, a steel structure is placed in the reaction frame, and the steel structure is supported through the auxiliary frames; a group of horizontal jacks are respectively arranged between the interiors of the two sides of the reaction frame and the exteriors of the two sides of the steel structure; a group of vertical jacks are arranged between the upper side of the reaction frame and the upper side of the steel structure; a heating mechanism is arranged on the outer side of the steel structure, and a cooling mechanism is arranged on the inner side of the steel structure. The detection mechanism comprises a strain gauge, and the strain gauge is pasted on the steel structure; the problem that an experimental platform capable of simultaneously simulating the performance change of the steel structure under the dual effects of temperature and stress is lacked at present is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of teaching equipment, and in particular relates to a teaching system and a teaching method utilizing stress simulation of temperature changes of steel structures. Background Art

[0002] In the current domestic civil engineering education and research field, the understanding and analysis of the mechanical performance of steel structures has made significant progress. Traditional force simulation technology mainly focuses on the mechanical response of a single component. Advanced finite element analysis software can accurately simulate the influence of material properties, geometric dimensions and load conditions on component performance. These technologies provide a solid theoretical and practical foundation for civil engineering design and promote the optimization and innovation of engineering structures.

[0003] However, with the continuous expansion of the scale and increasing complexity of civil engineering projects, the need for accurate prediction and optimization of the overall performance of buildings or infrastructure has become more urgent. Overall structural simulation not only needs to consider the interaction between single components, but also needs to incorporate a variety of external environmental factors, such as wind loads and seismic loads. In addition, temperature is one of the key factors affecting the performance of steel structures. Its changes will significantly affect the mechanical properties of the material, such as elastic modulus and yield strength, and thus have an important impact on the overall stress state of the structure.

[0004] Although some studies have begun to focus on the effect of temperature on the performance of steel structures, most of them are still limited to theoretical analysis and numerical simulation, lacking intuitive and effective experimental methods to verify and deepen these theoretical findings. Especially in the field of teaching, there is a lack of experimental platforms that can simultaneously simulate the changes in the performance of steel structures under the dual effects of temperature and force, which limits students' understanding of the mechanical characteristics of steel structures in complex engineering environments.

[0005] Therefore, how to use the steel structure stress simulation and teaching auxiliary system for teaching is crucial. This teaching method not only realizes the combination of stress and temperature, but also combines theoretical knowledge and comparison of experimental results, consolidates students' basic theoretical knowledge, integrates factors that may appear in real life to conduct overall simulation, and can also provide data for engineering development. Summary of the invention

[0006] The present invention overcomes the deficiencies of the prior art and proposes a teaching system and a teaching method using temperature change stress simulation of steel structures; it solves the problem of the current lack of an experimental platform that can simultaneously simulate the performance changes of steel structures under the dual effects of temperature and stress.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions.

[0008] A teaching system utilizing temperature change stress simulation of steel structure comprises a reaction frame, an auxiliary frame, a jack, a detection mechanism, a heating mechanism and a cooling mechanism. The reaction frame is a vertically arranged square frame structure, a plurality of auxiliary frames are staggered with the reaction frame, a steel structure is placed inside the reaction frame, and the steel structure is supported by the auxiliary frame; a group of horizontal jacks are respectively arranged between the inside of both sides of the reaction frame and the outside of both sides of the steel structure, and a group of vertical jacks are arranged between the upper side of the reaction frame and the upper side of the steel structure; a heating mechanism is arranged on the outer side of the steel structure, and a cooling mechanism is arranged on the inner side of the steel structure; the detection mechanism comprises a strain gauge, and the strain gauge is pasted on the steel structure.

[0009] Furthermore, the reaction frame includes an upper crossbeam, a lower crossbeam, a left column, and a right column. The upper crossbeam and the lower crossbeam are horizontally arranged along the left-right direction, and the upper crossbeam is located above the lower crossbeam; the left column and the right column are both kept vertical and symmetrically arranged; the left and right ends of the upper crossbeam are respectively fixedly connected to the upper ends of the left column and the right column, and the left and right ends of the lower crossbeam are respectively fixedly connected to the lower ends of the left column and the right column.

[0010] Furthermore, the auxiliary frame is a "sun" shaped frame structure arranged in a vertical plane in the front-to-back direction, including an upper longitudinal beam, a lower longitudinal beam, a middle longitudinal beam, a front column, and a rear column. The upper longitudinal beam, the middle longitudinal beam and the lower longitudinal beam are all horizontally arranged along the front-to-back direction, and the upper longitudinal beam and the lower longitudinal beam are respectively located on the upper and lower sides of the middle longitudinal beam; the front column and the rear column are both kept vertical and symmetrically arranged front and back; the front and rear ends of the upper longitudinal beam are respectively fixedly connected to the upper ends of the front column and the rear column, the front and rear ends of the middle longitudinal beam are respectively fixedly connected to the middle of the front column and the rear column, and the front and rear ends of the lower longitudinal beam are respectively fixedly connected to the lower ends of the front column and the rear column; two front-to-back symmetrical vertical limit rods are respectively fixedly arranged on the upper end surface of each middle longitudinal beam.

[0011] Furthermore, multiple auxiliary frames are arranged in the left-right direction, the middle part of the lower longitudinal beam of the auxiliary frame is fixedly connected to the lower cross beam of the reaction frame, and the lower longitudinal beam and the lower cross beam remain perpendicular; the middle part of the upper longitudinal beam of the auxiliary frame is fixedly connected to the upper cross beam of the reaction frame, and the upper longitudinal beam and the upper cross beam remain perpendicular.

[0012] Furthermore, the steel structure is a U-shaped structure with an opening facing downward, and the steel structure includes a horizontal beam and two vertical columns. The horizontal beam is horizontally arranged along the left and right directions, and the two vertical columns are symmetrically arranged along the left and right directions. The left and right ends of the horizontal beam are respectively fixedly connected to the upper ends of the two vertical columns; the lower ends of the two vertical columns of the steel structure are both in contact with the upper end surface of the lower cross beam of the reaction frame; the two vertical columns of the steel structure are respectively located on the inner sides of the left column and the right column of the reaction frame, and the horizontal beam of the steel structure is located below the reaction frame; the horizontal beam of the steel structure is in contact with the upper end surfaces of the middle longitudinal beams of all the auxiliary frames, and the steel structure is located between the two limit rods at the upper ends of all the middle longitudinal beams.

[0013] Furthermore, a group of horizontal jacks are respectively arranged between the two vertical columns of the steel structure and the left column and the right column of the reaction frame. The horizontal jacks are placed horizontally along the left and right directions. The bases of the horizontal jacks are respectively fixedly connected to the inner sides of the left and right columns of the reaction frame, and one end of the action rod of the horizontal jack is respectively facing one side of the vertical column on the same side; when the action rod of the horizontal jack is extended, a horizontal force is applied to the left and right sides of the steel structure.

[0014] Furthermore, a group of vertical jacks are arranged between the horizontal beam of the steel structure and the upper beam of the reaction frame. The vertical jacks are kept vertically arranged, and the base of the vertical jacks is fixedly connected to the lower end surface of the upper beam of the reaction frame. One end of the action rod of the vertical jack is vertically downward toward the horizontal beam of the steel structure; when the action rod of the vertical jack is extended, a vertical downward force is applied to the upper end of the steel structure.

[0015] Furthermore, the cooling mechanism includes cooling fins and a cooler, and multiple cooling fins are connected to the cooler, and multiple cooling fins are fixedly attached to the inner sides of the vertical columns and horizontal beams of the steel structure, and the cooling fins are used to cool the inner sides of the vertical columns and horizontal beams of the steel structure; the cooler is fixedly set on the front columns of one of the auxiliary frames; the heating mechanism includes heating fins and a heater, and multiple heating fins are connected to the heater, and multiple heating fins are fixedly attached to the outer sides of the vertical columns and horizontal beams of the steel structure, and the heating fins are used to heat the outer sides of the vertical columns and horizontal beams of the steel structure; the heater is fixedly set on the front column of one of the auxiliary frames.

[0016] Furthermore, the detection mechanism also includes a strain collector; the strain gauges are fixedly attached to the top and bottom ends of the two vertical columns of the steel structure, and the strain gauges are also fixedly attached to the left and right ends and the mid-span position of the horizontal beam of the steel structure, and the strains at the corresponding positions are measured by the strain gauges; all the strain gauges are connected to the strain collector.

[0017] Furthermore, according to a teaching method of a teaching system using a steel structure temperature change stress simulation, the teaching method comprises the following steps: S1: Place the steel structure at room temperature to ensure that there is no other external temperature interference; measure and record the strain data ε4 at the corresponding position, where ε4 is the initial reading of the strain gauge. Determine the length of time according to the experimental design to confirm that the strain remains stable without external temperature interference; compare the strain data recorded during the observation period to confirm that its fluctuation range is within an acceptable range to verify the stability of the strain without external temperature interference; S2: Use horizontal jacks and vertical jacks to apply predetermined horizontal and vertical loads to the steel structure; after the load is applied stably, record the data of each strain gauge as the initial strain value ε5; these data will serve as the basis for subsequent analysis; S3: The outer side of the steel structure is heated by the outer heating mechanism, and the inner cooling mechanism is started at the same time, so that the inner temperature of the steel structure is controlled at room temperature and maintained at a constant temperature; the heating mechanism and the cooling mechanism ensure precise control to ensure that each heating can produce a temperature difference of 10°C between the inner and outer sides of the steel structure; repeat this process, gradually increase the outer temperature, and wait for a period of time after each temperature difference change to ensure that the strain gauge reading is stable; after each temperature difference change is stable, record the data of each strain gauge ε6; S4: According to the predetermined applied load and the geometric dimensions and elastic modulus parameters of the steel structure, the internal force of the steel structure is calculated by the following method, and the strain of the measurement section is calculated by the internal force; the calculation method is as follows: S4.1 The moment distribution method is used to calculate the bending moment at the column end of the vertical column and the beam end of the horizontal beam under the vertical load. First, according to the formula Ki = Di / ΣDi, where Ki is the distribution coefficient and Di is the linear stiffness of the beam or column, the beam-column distribution coefficient Ki is calculated, and the fixed end bending moment is obtained by looking up the "Fixed end bending moment and fixed end shear force table of beams under load", and the distribution is performed according to the distribution coefficient, and the bending moment is transferred and distributed, thereby calculating the beam end and column end bending moment; S4.2 uses the inflection point method to calculate the bending moment of the horizontal beams and vertical columns of the steel structure under the horizontal load. First, the shear force of each layer of the structure is calculated based on the experiment, and the shear force is distributed to the two vertical columns according to the lateral stiffness. The 1 / 2 point is taken as the inflection point to calculate the bending moment at both ends to obtain the bending moment at both ends of the vertical column. The moment at the node is zero to calculate the beam end bending moment of the horizontal beam. The bending moment at the column end and beam end under the vertical load of S4.1 is superimposed with the bending moment at the corresponding section calculated by the horizontal load of S4.2. The stress σ1 at the measured section is calculated by the bending moment at the column end and beam end, and the strain value ε1 at the corresponding section is calculated by using the relationship between stress and strain ε=σ / E, where E is the elastic modulus. S4.3 uses the force method to calculate the internal forces generated by temperature. Since the steel structure is a symmetrical structure, half of the steel structure is taken for calculation to obtain a twice indeterminate structure, and the force method equation is listed: ; ; Among them, X1 and X2 are the forces of redundant constraints; Coefficient δ 11 It is numerically equal to the displacement of the basic structure in the direction of X1 when the unit force X1=1 acts alone; Coefficient δ 12 It is numerically equal to the displacement of the basic structure in the direction of X1 when the unit force X2=1 acts alone; Coefficient δ 21 It is numerically equal to the displacement of the basic structure in the direction X2 produced by the unit force X1=1 alone; Coefficient δ 22 It is numerically equal to the displacement of the basic structure in the direction X2 when the unit force X2=1 acts alone; coefficient is the displacement along the X1 direction caused by temperature; coefficient is the displacement along the X2 direction caused by temperature; Through the following formula ; Where h is the height of the cross-section beam, α is the linear expansion coefficient, It refers to the area of ​​the bending moment diagram produced by the axial force. It refers to the area of ​​the bending moment diagram produced by the bending moment. The positive and negative signs in the formula are specified as follows: the axial force is positive when the tension is positive, and t is positive when the temperature rise is positive; the positive and negative signs of the bending moment and the temperature difference are determined by their product: when the bending moment and the temperature difference cause tensile deformation on the same side of the rod, the product takes a positive value, otherwise it takes a negative value; t=1 / 2(t1+t2); Δ t =t2-t1, Δt is the height of the rectangular cross-section beam; get , and then obtain X1 and X2.

[0018] according to ; in, is the bending moment caused by the extra unknown force X1=1, is the bending moment caused by the extra unknown force X2=1; The bending moment M is obtained, and then the stress σ2 generated under the influence of temperature is obtained, and then the strain ε2 is obtained. The two strains are superimposed to obtain the theoretical total value ε3; S4.4 performs superposition: subtract the actual measured strain ε6 of each point under each temperature difference condition from the strain ε4 before loading to obtain the actual measured strain total value ε7, compare the theoretical calculated total value ε3 with the actual measured strain total value ε7, and evaluate the influence of temperature difference on the structure, as well as the error between theoretical calculation and experimental data; S5: Organize all the data recorded during the experiment, and write an experimental report based on the organized data and analysis results.

[0019] The beneficial effects of the present invention compared with the prior art are as follows: 1. The system can simulate the common temperature difference environment encountered by steel structures in actual projects. Through the coordinated work of the temperature-controlled adjustable heating plate on the outside and the cooling plate on the inside, the temperature change of the steel structure can be precisely controlled. At the same time, the system also relies on the solid reaction frame and the sophisticated auxiliary frame design to ensure the safety and stability of the steel structure during the simulation process, and can cope with various simulated loading challenges.

[0020] 2. The system is equipped with adjustable horizontal jacks and vertical jacks, which can accurately simulate the horizontal and vertical loads that steel structures bear in actual projects, making the experimental environment closer to actual projects. This loading method allows the overall mechanical performance test of the steel structure to be carried out, so as to deeply understand and evaluate the mechanical performance of the entire structure when subjected to loads in different directions.

[0021] 3. The combination of strain gauges at key locations of steel structures and static strain acquisition instruments enables instant and accurate capture of strain data, providing students and researchers with rich and intuitive experimental evidence. This comprehensive and accurate data collection and analysis is of great significance for in-depth understanding of the performance characteristics of steel structures, optimizing structural design, and predicting structural behavior.

[0022] 4. The system not only provides an intuitive and vivid experimental platform for civil engineering students, helping them to more deeply understand and master the stress characteristics of steel structures under different temperature difference conditions, but also improves the teaching effect. Through practical operation and data analysis, students can better understand the stress conditions of steel structures in actual projects and improve their ability to solve practical problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings: Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a front view of the present invention as a whole; Figure 3 It is a schematic diagram of the connection between the reaction frame, auxiliary frame, horizontal jack and vertical jack; Figure 4It is the front view of the steel structure; Figure 5 It is a schematic diagram of the structure of the strain collector; Figure 6 It is a schematic diagram of the structure of the heater; Figure 7 It is a schematic diagram of the structure of the cooler; Figure 8 It is a connection relationship diagram between the steel structure, cooling fins, heat sinks, and cooling fans; Among them, 1 is a reaction frame, 2 is an auxiliary frame, 3 is a steel structure, 4 is a horizontal jack, 5 is a vertical jack, 6 is an upper crossbeam, 7 is a lower crossbeam, 8 is a left column, 9 is a right column, 10 is an upper longitudinal beam, 11 is a lower longitudinal beam, 12 is a middle longitudinal beam, 13 is a front column, 14 is a rear column, 15 is a limit rod, 16 is a horizontal beam, 17 is a vertical column, 18 is a cooling plate, 19 is a cooler, 20 is a heating plate, 21 is a heater, 22 is a strain collector, 23 is a heat sink, and 24 is a cooling fan. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0025] like Figure 1 As shown in FIG8 , the present invention provides a teaching system for simulating the stress of steel structure by temperature change, comprising a reaction frame 1, an auxiliary frame 2, a jack, a detection mechanism, a heating mechanism, and a cooling mechanism. The reaction frame 1 is a vertically arranged square frame structure, and a plurality of auxiliary frames 2 are staggered with the reaction frame 1. The steel structure 3 is placed inside the reaction frame 1, and the steel structure 3 is supported by the auxiliary frame 2. A group of horizontal jacks 4 are respectively arranged between the inside of both sides of the reaction frame 1 and the outside of both sides of the steel structure 3, and a group of vertical jacks 5 are arranged between the upper side of the reaction frame 1 and the upper side of the steel structure 3. A heating mechanism is arranged on the outer side of the steel structure 3, and a cooling mechanism is arranged on the inner side of the steel structure 3. The detection mechanism comprises a strain gauge, and the strain gauge is pasted on the steel structure 3.

[0026] The reaction frame 1 includes an upper crossbeam 6, a lower crossbeam 7, a left column 8, and a right column 9. The upper crossbeam 6 and the lower crossbeam 7 are horizontally arranged along the left-right direction, and the upper crossbeam 6 is located above the lower crossbeam 7; the left column 8 and the right column 9 are both kept vertical and symmetrically arranged; the left and right ends of the upper crossbeam 6 are respectively fixedly connected to the upper ends of the left column 8 and the right column 9, and the left and right ends of the lower crossbeam 7 are respectively fixedly connected to the lower ends of the left column 8 and the right column 9.

[0027] The auxiliary frame 2 is a "sun" shaped frame structure arranged in a vertical plane in the front-to-back direction, including an upper longitudinal beam 10, a lower longitudinal beam 11, a middle longitudinal beam 12, a front column 13, and a rear column 14. The upper longitudinal beam 10, the middle longitudinal beam 12 and the lower longitudinal beam 11 are all arranged horizontally along the front-to-back direction, and the upper longitudinal beam 10 and the lower longitudinal beam 11 are respectively located on the upper and lower sides of the middle longitudinal beam 12; the front column 13 and the rear column 14 are both kept vertical and symmetrically arranged front and back; the front and rear ends of the upper longitudinal beam 10 are respectively fixedly connected to the upper ends of the front column 13 and the rear column 14, the front and rear ends of the middle longitudinal beam 12 are respectively fixedly connected to the middle of the front column 13 and the rear column 14, and the front and rear ends of the lower longitudinal beam 11 are respectively fixedly connected to the lower ends of the front column 13 and the rear column 14. Two front-to-rear symmetrical vertical limiting rods 15 are fixedly arranged on the upper end surface of each middle longitudinal beam 12 , and the two limiting rods 15 on all the middle longitudinal beams 12 maintain the same distance.

[0028] Multiple auxiliary frames 2 are arranged in the left-right direction, and the middle part of the lower longitudinal beam 11 of the auxiliary frame 2 is fixedly connected to the lower cross beam 7 of the reaction frame 1, and the lower longitudinal beam 11 and the lower cross beam 7 remain perpendicular; the middle part of the upper longitudinal beam 10 of the auxiliary frame 2 is fixedly connected to the upper cross beam 6 of the reaction frame 1, and the upper longitudinal beam 10 and the upper cross beam 6 remain perpendicular.

[0029] The steel structure 3 is a U-shaped structure with an opening downward, and includes a horizontal beam 16 and two vertical columns 17. The horizontal beam 16 is horizontally arranged along the left and right directions, and the two vertical columns 17 are symmetrically arranged along the left and right directions. The left and right ends of the horizontal beam 16 are respectively fixedly connected to the upper ends of the two vertical columns 17. The lower ends of the two vertical columns 17 of the steel structure 3 are in contact with the upper end surface of the lower cross beam 7 of the reaction frame 1. The two vertical columns 17 of the steel structure 3 are respectively located on the inner side of the left column 8 and the right column 9 of the reaction frame 1, and the horizontal beam 16 of the steel structure 3 is located below the reaction frame 1. The horizontal beam 16 of the steel structure 3 is in contact with the upper end surfaces of the middle longitudinal beams 12 of all the auxiliary frames 2, and the steel structure 3 is located between the two limiting rods 15 at the upper ends of all the middle longitudinal beams 12, and the horizontal beam 16 of the steel structure 3 is supported by the middle longitudinal beam 12, and the front and rear positions of the steel structure 3 are limited by the front and rear limiting rods 15.

[0030] A group of horizontal jacks 4 is respectively arranged between the two vertical columns 17 of the steel structure 3 and the left column 8 and the right column 9 of the reaction frame 1. The multiple horizontal jacks 4 in a group are evenly arranged along the vertical direction. The horizontal jacks 4 are horizontally placed along the left and right directions. The bases of the horizontal jacks 4 are respectively fixedly connected to the inner sides of the left column 8 and the right column 9 of the reaction frame 1. One end of the action rod of the horizontal jack 4 is respectively facing the side of the vertical column 17 on the same side. When the action rod of the horizontal jack 4 is extended, a horizontal force is applied to the left and right sides of the steel structure 3.

[0031] A group of vertical jacks 5 is arranged between the horizontal beam 16 of the steel structure 3 and the upper beam 6 of the reaction frame 1. A plurality of vertical jacks 5 in a group are evenly arranged along the left and right directions. The vertical jacks 5 are kept vertically arranged. The base of the vertical jacks 5 is fixedly connected to the lower end surface of the upper beam 6 of the reaction frame 1. One end of the action rod of the vertical jack 5 is vertically downward toward the horizontal beam 16 of the steel structure 3. When the action rod of the vertical jack 5 is extended, a vertical downward force is applied to the upper end of the steel structure 3.

[0032] The cooling mechanism includes cooling fins 18 and a cooler 19, and the plurality of cooling fins 18 are connected to the cooler 19, and the cooling fins 18 are provided with cooling function by the cooler 19. The plurality of cooling fins 18 are fixedly attached to the inner side surfaces of the vertical columns 17 and the horizontal beams 16 of the steel structure 3, respectively, and the inner side surfaces of the vertical columns 17 and the horizontal beams 16 of the steel structure 3 are cooled by the cooling fins 18. The cooler 19 is fixedly arranged on the front column 13 of one of the auxiliary frames 2.

[0033] The heating mechanism includes a heating plate 20 and a heater 21. The plurality of heating plates 20 are connected to the heater 21, and the heater 21 provides a heating function for the heating plates 20. The plurality of heating plates 20 are fixedly attached to the outer sides of the vertical columns 17 and the horizontal beams 16 of the steel structure 3, respectively, and the outer sides of the vertical columns 17 and the horizontal beams 16 of the steel structure 3 are heated by the heating plates 20. The heater 21 is fixedly arranged on the front column 13 of one of the auxiliary frames 2.

[0034] The detection mechanism also includes a strain collector 22. The strain gauges are fixedly attached to the top and bottom ends of the two vertical columns 17 of the steel structure 3, and the strain gauges are also fixedly attached to the left and right ends and the mid-span position of the horizontal beam 16 of the steel structure 3, and the strains at the corresponding positions are measured by the strain gauges. All the strain gauges are connected to the strain collector 22.

[0035] The teaching system is also provided with a heat dissipation mechanism, which includes a heat sink 23 and a heat dissipation fan 24. The heat sink 23 is fixedly attached to the inner side of the horizontal beam 16 and the vertical column 17 of the steel structure 3, and the heat dissipation fan 24 is fixedly arranged on the heat sink 23. The heat sink 23 is used to absorb the heat on the steel structure 3, and the heat dissipation fan 24 is used to volatilize the heat absorbed inside the heat sink 23.

[0036] According to a teaching method of a teaching system using a steel structure temperature change stress simulation, the teaching method comprises the following steps: S1: Place the steel structure 3 at room temperature to ensure that there is no other external temperature interference; measure and record the strain data ε4 at the corresponding position, where ε4 is the initial reading of the strain gauge, and determine the length of time according to the experimental design to confirm that the strain remains stable without external temperature interference; compare the strain data recorded during the observation period to confirm that its fluctuation range is within an acceptable range to verify the stability of the strain without external temperature interference; S2: Use the horizontal jack 4 and the vertical jack 5 to apply the predetermined horizontal and vertical loads to the steel structure 3; after the load application is stable, record the data of each strain gauge as the initial strain value ε5; these data will serve as the basis for subsequent analysis; S3: The outer side of the steel structure 3 is heated by the outer heating mechanism, and the inner cooling mechanism is started at the same time, so that the inner temperature of the steel structure 3 is controlled at room temperature and kept constant; the heating mechanism and the cooling mechanism ensure precise control to ensure that each heating can produce a temperature difference of 10°C between the inner and outer sides of the steel structure 3; repeat this process, gradually increase the outer temperature, and wait for a period of time after each temperature difference change to ensure that the strain gauge reading is stable; after each temperature difference change is stable, record the data of each strain gauge ε6; S4: According to the predetermined applied load and the geometric dimensions and elastic modulus parameters of the steel structure 3, the internal force of the steel structure 3 is calculated by the following method, and the strain of the measurement section is calculated by the internal force; the calculation method is as follows: S4.1 The moment distribution method is used to calculate the bending moment at the column end of the vertical column 17 and the beam end of the horizontal beam 16 under the vertical load; first, according to the formula Ki= Di / ΣDi, where Ki is the distribution coefficient and Di is the linear stiffness of the beam or column, the beam-column distribution coefficient Ki is calculated, and the fixed end bending moment is obtained by looking up Table 1 (the fixed end bending moment and fixed end shear force table of the beam under load state), and the distribution is performed according to the distribution coefficient, and the bending moment is transferred and distributed, thereby calculating the beam end and column end bending moment.

[0037] Table 1 S4.2 uses the inflection point method to calculate the bending moment of the horizontal beam 16 and vertical column 17 of the steel structure 3 under the horizontal load; first, the shear force of each layer of the structure is obtained according to the experiment, and the shear force is distributed to the two vertical columns 17 according to the lateral stiffness. The 1 / 2 point is taken as the inflection point to calculate the bending moment at both ends, and the bending moment at both ends of the vertical column 17 is obtained. The moment at the node is zero to calculate the beam end bending moment of the horizontal beam 16, and the bending moment at the column end and beam end under the vertical load of S4.1 is superimposed with the bending moment at the corresponding section calculated by the horizontal load of S4.2; the stress σ1 at the measuring section is obtained by the bending moment at the column end and beam end, and the strain value ε1 at the corresponding section is obtained by using the relationship between stress and strain ε=σ / E, where E is the elastic modulus; S4.3 uses the force method to calculate the internal forces generated by temperature. Since the steel structure 3 is a symmetrical structure, half of the steel structure 3 is taken for calculation to obtain a twice indeterminate structure, and the force method equation is listed: ; ; Among them, X1 and X2 are the forces of redundant constraints; Coefficient δ 11 It is numerically equal to the displacement of the basic structure in the direction of X1 when the unit force X1=1 acts alone; Coefficient δ 12 It is numerically equal to the displacement of the basic structure in the direction of X1 when the unit force X2=1 acts alone; Coefficient δ 21 It is numerically equal to the displacement of the basic structure in the direction X2 produced by the unit force X1=1 alone; Coefficient δ 22 It is numerically equal to the displacement of the basic structure in the direction X2 when the unit force X2=1 acts alone; coefficient is the displacement along the X1 direction caused by temperature; coefficient is the displacement along the X2 direction caused by temperature; Through the following formula ; Where h is the height of the cross-section beam, α is the linear expansion coefficient, It refers to the area of ​​the bending moment diagram produced by the axial force. It refers to the area of ​​the bending moment diagram produced by the bending moment. The positive and negative signs in the formula are specified as follows: the axial force is positive when the tension is positive, and t is positive when the temperature rise is positive; the positive and negative signs of the bending moment and the temperature difference are determined by their product: when the bending moment and the temperature difference cause tensile deformation on the same side of the rod, the product takes a positive value, otherwise it takes a negative value; t=1 / 2(t1+t2); Δ t=t2-t1, Δt is the height of the rectangular cross-section beam; get , and then obtain X1 and X2.

[0038] according to ; in, is the bending moment caused by the extra unknown force X1=1, is the bending moment caused by the extra unknown force X2=1; The bending moment M is obtained, and then the stress σ2 generated under the influence of temperature is obtained, and then the strain ε2 is obtained. The two strains are superimposed to obtain the theoretical total value ε3; S4.4 performs superposition: subtract the actual measured strain ε6 of each point under each temperature difference condition from the strain ε4 before loading to obtain the actual measured strain total value ε7, compare the theoretical calculated total value ε3 with the actual measured strain total value ε7, and evaluate the influence of temperature difference on the structure, as well as the error between theoretical calculation and experimental data; S5: Organize all the data recorded during the experiment, and write an experimental report based on the organized data and analysis results.

[0039] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A teaching system using steel structure temperature change stress simulation, characterized by: It includes a reaction frame (1), an auxiliary frame (2), a jack, a detection mechanism, a heating mechanism, and a cooling mechanism. The reaction frame (1) is a vertically arranged square frame structure. A plurality of auxiliary frames (2) are arranged alternately with the reaction frame (1). A steel structure (3) is placed inside the reaction frame (1), and the steel structure (3) is supported by the auxiliary frames (2). A set of horizontal jacks (4) are respectively arranged between the inner sides of both sides of the reaction frame (1) and the outer sides of both sides of the steel structure (3), and a set of vertical jacks (5) are arranged between the upper side of the reaction frame (1) and the upper side of the steel structure (3). A heating mechanism is arranged on the outer side of the steel structure (3), and a cooling mechanism is arranged on the inner side of the steel structure (3). The detection mechanism includes strain gauges, and the strain gauges are pasted on the steel structure (3).

2. The teaching system using the stress simulation of temperature change of steel structure according to claim 1 is characterized by: The reaction frame (1) includes an upper cross beam (6), a lower cross beam (7), a left vertical column (8), and a right vertical column (9). The upper cross beam (6) and the lower cross beam (7) are both horizontally arranged along the left - right direction, and the upper cross beam (6) is located above the lower cross beam (7). The left vertical column (8) and the right vertical column (9) are both vertical and symmetrically arranged left - right. The left and right ends of the upper cross beam (6) are respectively fixedly connected to the upper ends of the left vertical column (8) and the right vertical column (9), and the left and right ends of the lower cross beam (7) are respectively fixedly connected to the lower ends of the left vertical column (8) and the right vertical column (9).

3. The teaching system using steel structure temperature change stress simulation according to claim 2 is characterized by: The auxiliary frame (2) is an "H" - shaped frame structure arranged in a vertical plane in the front - back direction, including an upper longitudinal beam (10), a lower longitudinal beam (11), a middle longitudinal beam (12), a front vertical column (13), and a rear vertical column (14). The upper longitudinal beam (10), the middle longitudinal beam (12), and the lower longitudinal beam (11) are all horizontally arranged along the front - back direction. The upper longitudinal beam (10) and the lower longitudinal beam (11) are respectively located above and below the middle longitudinal beam (12). The front vertical column (13) and the rear vertical column (14) are both vertical and symmetrically arranged front - back. The front and rear ends of the upper longitudinal beam (10) are respectively fixedly connected to the upper ends of the front vertical column (13) and the rear vertical column (14). The front and rear ends of the middle longitudinal beam (12) are respectively fixedly connected to the middle parts of the front vertical column (13) and the rear vertical column (14). The front and rear ends of the lower longitudinal beam (11) are respectively fixedly connected to the lower ends of the front vertical column (13) and the rear vertical column (14). Two vertically arranged and front - back symmetric limit rods (15) are respectively fixedly arranged on the upper end surfaces of each middle longitudinal beam (12).

4. The teaching system using the stress simulation of temperature change of steel structure according to claim 3 is characterized by: A plurality of auxiliary frames (2) are arranged in a row along the left - right direction. The middle part of the lower longitudinal beam (11) of the auxiliary frame (2) is fixedly connected to the lower cross beam (7) of the reaction frame (1), and the lower longitudinal beam (11) is perpendicular to the lower cross beam (7). The middle part of the upper longitudinal beam (10) of the auxiliary frame (2) is fixedly connected to the upper cross beam (6) of the reaction frame (1), and the upper longitudinal beam (10) is perpendicular to the upper cross beam (6).

5. The teaching system using the stress simulation of temperature change of steel structure according to claim 3 is characterized by: The steel structure (3) is a U-shaped structure with an opening facing downward. The steel structure (3) comprises a horizontal beam (16) and two vertical columns (17). The horizontal beam (16) is arranged horizontally along the left-right direction, and the two vertical columns (17) are arranged symmetrically along the left-right direction. The left and right ends of the horizontal beam (16) are respectively fixedly connected to the upper ends of the two vertical columns (17); the lower ends of the two vertical columns (17) of the steel structure (3) are in contact with the upper end surface of the lower cross beam (7) of the reaction frame (1); the two vertical columns (17) of the steel structure (3) are respectively located on the inner sides of the left column (8) and the right column (9) of the reaction frame (1), and the horizontal beam (16) of the steel structure (3) is located below the reaction frame (1); the horizontal beam (16) of the steel structure (3) is in contact with the upper end surfaces of the middle longitudinal beams (12) of all the auxiliary frames (2), and the steel structure (3) is located between the two limit rods (15) at the upper ends of all the middle longitudinal beams (12).

6. The teaching system using the stress simulation of temperature change of steel structure according to claim 5 is characterized by: A group of horizontal jacks (4) are respectively arranged between the two vertical columns (17) of the steel structure (3) and the left column (8) and the right column (9) of the reaction frame (1). The horizontal jacks (4) are placed horizontally along the left-right direction. The bases of the horizontal jacks (4) are respectively fixedly connected to the inner side surfaces of the left column (8) and the right column (9) of the reaction frame (1). One end of the action rod of the horizontal jack (4) is respectively directed toward the side of the vertical column (17) on the same side. When the action rod of the horizontal jack (4) is extended, a horizontal force is applied to the left and right sides of the steel structure (3).

7. The teaching system using the stress simulation of temperature change of steel structure according to claim 5 is characterized by: A group of vertical jacks (5) are arranged between the horizontal beam (16) of the steel structure (3) and the upper beam (6) of the reaction frame (1). The vertical jacks (5) are kept vertically arranged, and the base of the vertical jacks (5) is fixedly connected to the lower end surface of the upper beam (6) of the reaction frame (1). One end of the action rod of the vertical jack (5) is vertically downward toward the horizontal beam (16) of the steel structure (3); when the action rod of the vertical jack (5) is extended, a vertical downward force is applied to the upper end of the steel structure (3).

8. The teaching system using the stress simulation of temperature change of steel structure according to claim 5 is characterized by: The cooling mechanism comprises a cooling fin (18) and a cooler (19), wherein the plurality of cooling fins (18) are connected to the cooler (19), and the plurality of cooling fins (18) are respectively fixedly attached to the inner side surfaces of the vertical columns (17) and the horizontal beams (16) of the steel structure (3), so that the inner side surfaces of the vertical columns (17) and the horizontal beams (16) of the steel structure (3) are cooled by the cooling fins (18); the cooler (19) is fixedly arranged on a front column (13) of one of the auxiliary frames (2); The heating mechanism comprises a heating plate (20) and a heater (21), wherein the plurality of heating plates (20) are connected to the heater (21), and the plurality of heating plates (20) are respectively fixedly attached to the outer surfaces of the vertical columns (17) and the horizontal beams (16) of the steel structure (3), so that the outer surfaces of the vertical columns (17) and the horizontal beams (16) of the steel structure (3) are heated by the heating plates (20); the heater (21) is fixedly arranged on a front column (13) of one of the auxiliary frames (2).

9. The teaching system using steel structure temperature change stress simulation according to claim 5 is characterized by: The detection mechanism also includes a strain collector (22); the strain gauges are fixedly attached to the top and bottom ends of the two vertical columns (17) of the steel structure (3); the strain gauges are also fixedly attached to the left and right ends and the mid-span position of the horizontal beam (16) of the steel structure (3); the strain gauges are used to measure the strain at the corresponding positions; all the strain gauges are connected to the strain collector (22).

10. A teaching method according to any one of claims 5 to 9, characterized in that: The following steps are included: S1: Place the steel structure (3) at room temperature to ensure that there is no external temperature interference; measure and record the strain data ε4 at the corresponding position, where ε4 is the initial reading of the strain gauge, and determine the length of time according to the experimental design to confirm that the strain remains stable without external temperature interference; compare the strain data recorded during the observation period to confirm that its fluctuation range is within an acceptable range to verify the stability of the strain without external temperature interference; S2: Use a horizontal jack (4) and a vertical jack (5) to apply a predetermined horizontal and vertical load to the steel structure (3); after the load is applied stably, record the data of each strain gauge as the initial strain value ε5; these data will serve as a benchmark for subsequent analysis; S3: The outer side of the steel structure (3) is heated by the outer heating mechanism, and the inner cooling mechanism is started at the same time, so that the inner temperature of the steel structure (3) is controlled at room temperature and maintained at a constant temperature; the heating mechanism and the cooling mechanism ensure precise control to ensure that each heating can produce a temperature difference of 10°C between the inner and outer sides of the steel structure (3); repeat this process, gradually increase the outer temperature, and wait for a period of time after each temperature difference change to ensure that the strain gauge reading is stable; after each temperature difference change is stable, record the data ε6 of each strain gauge; S4: According to the predetermined applied load and the geometric dimensions and elastic modulus parameters of the steel structure (3), the internal force of the steel structure (3) is calculated by the following method, and the strain of the measurement section is calculated by the internal force; the calculation method is as follows: S4.1 The moment distribution method is used to calculate the bending moment at the column end of the vertical column (17) and the beam end of the horizontal beam (16) under the vertical load. First, according to the formula Ki = Di / ΣDi, where Ki is the distribution coefficient and Di is the linear stiffness of the beam or column, the beam-column distribution coefficient Ki is calculated, and the fixed end bending moment is obtained by looking up the "Fixed end bending moment and fixed end shear force table of beams under load", and the distribution is performed according to the distribution coefficient, and the bending moment is transferred and distributed, thereby calculating the beam end and column end bending moment; S4.2 uses the inflection point method to calculate the bending moment generated by the horizontal beam (16) and vertical column (17) of the steel structure (3) under the horizontal load. First, the shear force on each layer of the structure is calculated based on the experiment, and the shear force is distributed to the two vertical columns (17) according to the lateral stiffness. The 1 / 2 point is taken as the inflection point to calculate the bending moment at both ends to obtain the bending moment at both ends of the vertical column (17). The bending moment at the end of the horizontal beam (16) is calculated using the moment at the node as zero. The bending moment at the column end and the beam end under the vertical load in S4.1 is superimposed with the bending moment at the corresponding section calculated by the horizontal load in S4.

2. The stress σ1 at the measuring section is calculated by the bending moment at the column end and the beam end, and the strain value ε1 at the corresponding section is calculated using the relationship between stress and strain ε=σ / E, where E is the elastic modulus. S4.3 uses the force method to calculate the internal forces generated by temperature. Since the steel structure (3) is a symmetrical structure, half of the steel structure (3) is taken for calculation to obtain a twice indeterminate structure, and the force method equation is listed as follows: ； ； Among them, X1 and X2 are the forces of redundant constraints; Coefficient δ 11 It is numerically equal to the displacement of the basic structure in the direction of X1 when the unit force X1=1 acts alone; Coefficient δ 12 It is numerically equal to the displacement of the basic structure in the direction of X1 when the unit force X2=1 acts alone; Coefficient δ 21 It is numerically equal to the displacement of the basic structure in the direction X2 produced by the unit force X1=1 alone; Coefficient δ 22 It is numerically equal to the displacement of the basic structure in the direction X2 when the unit force X2=1 acts alone; coefficient is the displacement along the X1 direction caused by temperature; coefficient is the displacement along the X2 direction caused by temperature; Through the following formula ； Where h is the height of the cross-section beam, α is the linear expansion coefficient, It refers to the area of ​​the bending moment diagram produced by the axial force. It refers to the area of ​​the bending moment diagram produced by the bending moment. The positive and negative signs in the formula are specified as follows: the axial force is positive when the tension is positive, and t is positive when the temperature rise is positive; the positive and negative signs of the bending moment and the temperature difference are determined by their product: when the bending moment and the temperature difference cause tensile deformation on the same side of the rod, the product takes a positive value, otherwise it takes a negative value; t=1 / 2(t1+t2); Δ t =t2-t1, Δt is the height of the rectangular cross-section beam; get , and then obtain X1 and X2; according to ； in, is the bending moment caused by the extra unknown force X1=1, is the bending moment caused by the extra unknown force X2=1; The bending moment M is obtained, and then the stress σ2 generated under the influence of temperature is obtained, and then the strain ε2 is obtained. The two strains are superimposed to obtain the theoretical total value ε3; S4.4 performs superposition: subtract the actual measured strain ε6 of each point under each temperature difference condition from the strain ε4 before loading to obtain the actual measured strain total value ε7, compare the theoretical calculated total value ε3 with the actual measured strain total value ε7, and evaluate the influence of temperature difference on the structure, as well as the error between theoretical calculation and experimental data; S5: Organize all the data recorded during the experiment, and write an experimental report based on the organized data and analysis results.

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