A teaching system and teaching method for simulating the force-bearing of a steel structure due to temperature changes

Abstract

The present invention relates to a teaching system and teaching method for simulating the force of a steel structure under temperature change, belonging to the technical field of teaching equipment; the teaching system includes 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, and multiple auxiliary frames are arranged alternately with the reaction frame. The steel structure is placed inside the reaction frame, and the steel structure is supported by the auxiliary frame; a set of horizontal jacks are respectively arranged between the inner sides of both sides of the reaction frame and the outer sides of both sides of the steel structure, and a set 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 includes strain gauges, and the strain gauges are pasted on the steel structure; it solves the problem that there is currently a lack of an experimental platform that can simultaneously simulate the performance change of a steel structure under the dual action of temperature and force.

Description

Technical Field

[0001] The present invention belongs to the technical field of teaching equipment, and particularly relates to a teaching system and teaching method for simulating the stress of a steel structure under temperature change. Background Art

[0002] In the current domestic civil engineering education and research field, significant progress has been made in the understanding and analysis of the mechanical properties of steel structures. Traditional stress simulation techniques mainly focus on the mechanical response of a single component, and the advanced finite element analysis software can accurately simulate the influence of material properties, geometric dimensions, and load conditions on the component performance. These techniques provide a solid theoretical and practical basis 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 demand for accurate prediction and optimization of the overall performance of buildings or infrastructure is becoming more urgent. The overall structure simulation not only needs to consider the interaction between single components but also needs to incorporate various external environmental factors, such as wind load, seismic load, etc. In addition, temperature, as one of the key factors affecting the performance of steel structures, its change will significantly affect the mechanical properties such as the elastic modulus and yield strength of materials, and thus have an important impact on the overall stress state of the structure.

[0004] Although existing research has begun to focus on the influence of temperature on the performance of steel structures, most of them are still limited to the theoretical analysis and numerical simulation stage, lacking intuitive and effective experimental means to verify and deepen these theoretical findings. Especially in the teaching field, there is a lack of an experimental platform that can simultaneously simulate the performance change of steel structures under the dual action of temperature and stress, which limits students' understanding of the stress characteristics of steel structures in complex engineering environments.

[0005] Therefore, it is crucial to use a steel structure stress simulation and teaching assistance system for teaching. This teaching method not only realizes the combination of stress and temperature but also combines theoretical knowledge and the comparison of experimental results, consolidates students' basic theoretical knowledge, integrates the possible factors in real life for overall simulation, and can also provide data for the development of the project. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a teaching system and teaching method for simulating the stress of a steel structure under temperature change, solving the problem of the lack of an experimental platform that can simultaneously simulate the performance change of steel structures under the dual action of temperature and stress.

[0007] To achieve the above object, the present invention is realized by the following technical solutions.

[0008] A teaching system for simulating the force of a steel structure due to temperature change, comprising 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, and multiple auxiliary frames are arranged alternately with the reaction frame. The steel structure is placed inside the reaction frame, and the steel structure is supported by the auxiliary frames. A set of horizontal jacks are respectively arranged between the inner sides of both sides of the reaction frame and the outer sides of both sides of the steel structure, and a set 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 includes strain gauges, and the strain gauges are pasted on the steel structure.

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

[0010] Further, the auxiliary frame is an "8" - shaped frame structure arranged in a vertical plane along the front - back direction, including an upper longitudinal beam, a lower longitudinal beam, a middle longitudinal beam, a front upright column, and a rear upright column. The upper longitudinal beam, the middle longitudinal beam, and the lower longitudinal beam are all horizontally arranged along the front - back direction, and the upper longitudinal beam and the lower longitudinal beam are respectively located above and below the middle longitudinal beam. The front upright column and the rear upright column are both vertical and symmetrically arranged front and back. The front and back ends of the upper longitudinal beam are respectively fixedly connected to the upper ends of the front upright column and the rear upright column, the front and back ends of the middle longitudinal beam are respectively fixedly connected to the middle parts of the front upright column and the rear upright column, and the front and back ends of the lower longitudinal beam are respectively fixedly connected to the lower ends of the front upright column and the rear upright column. Two vertically arranged and front - back symmetric limiting rods are respectively fixedly arranged on the upper end surfaces of each middle longitudinal beam.

[0011] Further, multiple auxiliary frames are arranged in a row along 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 is perpendicular to the lower cross beam. 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 is perpendicular to the upper cross beam.

[0012] Further, the steel structure is a U-shaped structure with an opening downward. The steel structure includes a horizontal beam and two vertical columns. The horizontal beam is horizontally arranged along the left-right direction, and the two vertical columns are symmetrically arranged along the left-right direction. 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 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 inside 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 middle longitudinal beam of all the auxiliary frames of the horizontal beam of the steel structure is in contact with the upper end surface, and the steel structure is located between the two limit rods at the upper ends of all the middle longitudinal beams.

[0013] Further, a set 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 horizontally placed along the left-right direction. The bases of the horizontal jacks are respectively fixedly connected to the inner side surfaces of the left column and the right column of the reaction frame, and one end of the action rod of the horizontal jack is respectively directed towards the vertical column on the same side. When the action rods of the horizontal jacks extend, horizontal forces are applied to the left and right sides of the steel structure.

[0014] Further, a set of vertical jacks are arranged between the horizontal beam of the steel structure and the upper cross beam of the reaction frame. The vertical jacks are vertically arranged. The base of the vertical jack is fixedly connected to the lower end surface of the upper cross beam of the reaction frame, and one end of the action rod of the vertical jack is vertically downward towards the horizontal beam of the steel structure. When the action rod of the vertical jack extends, a vertically downward force is applied to the upper end of the steel structure.

[0015] Further, the cooling mechanism includes cooling fins and a cooler. A plurality of cooling fins are all connected to the cooler, and the plurality of cooling fins are respectively fixedly pasted on the inner side surfaces of the vertical columns and the horizontal beam of the steel structure to cool the inner side surfaces of the vertical columns and the horizontal beam of the steel structure through the cooling fins. The cooler is fixedly arranged on the front column of one of the auxiliary frames. The heating mechanism includes heating fins and a heater. A plurality of heating fins are all connected to the heater, and the plurality of heating fins are respectively fixedly pasted on the outer side surfaces of the vertical columns and the horizontal beam of the steel structure to heat the outer side surfaces of the vertical columns and the horizontal beam of the steel structure through the heating fins. The heater is fixedly arranged on the front column of one of the auxiliary frames.

[0016] Further, the detection mechanism further includes a strain acquisition instrument. Strain gauges are fixedly pasted on the top and bottom ends of the two vertical columns of the steel structure, and at the same time, strain gauges are also fixedly pasted at the left and right ends and the mid-span position of the horizontal beam of the steel structure to measure the strain at the corresponding positions through the strain gauges. All the strain gauges are connected to the strain acquisition instrument.

[0017] Furthermore, according to a teaching method of a teaching system for simulating the force of a steel structure due to temperature change, the method includes the following steps:

[0018] S1: Place the steel structure at room temperature to ensure no other external temperature interference; measure and record the strain data ε4 at the corresponding position. ε4 is the initial reading of the strain gauge. Determine the time length 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 and confirm that its fluctuation range is within an acceptable range to verify the stability of the strain without external temperature interference.

[0019] S2: Apply a predetermined horizontal and vertical load to the steel structure using a horizontal jack and a vertical jack; after the load is applied stably, record the data of each strain gauge as the initial strain value ε5; these data will be used as the basis for subsequent analysis.

[0020] S3: Heat the outside of the steel structure through the outside heating mechanism, and at the same time start the inside cooling mechanism to keep the inside temperature of the steel structure at room temperature and constant; the heating mechanism and the cooling mechanism ensure precise control to ensure that each temperature increase can cause a 10°C temperature difference between the inside and outside of the steel structure; repeat this process, gradually increase the outside temperature, and wait for a period of time after each temperature difference change to ensure that the strain gauge readings are stable; after each temperature difference change is stable, record the data ε6 of each strain gauge.

[0021] S4: According to the predetermined applied load, the geometric dimensions, and the elastic modulus parameters of the steel structure, calculate the internal force of the steel structure using the following method, and measure the strain of the cross-section through internal force calculation; the calculation method is as follows:

[0022] S4.1 Use the moment distribution method to calculate the moments at the column ends of the vertical columns and the beam ends of the horizontal beams under the action of the vertical load; first, calculate the beam-column distribution coefficient Ki according to the formula Ki = Di / ΣDi, where Ki is the distribution coefficient and Di is the linear stiffness of the beam or column. Check the "Table of Fixed-End Moments and Fixed-End Shears of Beams under Loaded Conditions" to obtain the fixed-end moments, and distribute them according to the distribution coefficient, and transfer and distribute the moments to calculate the beam-end and column-end moments.

[0023] In S4.2, the moment generated by the horizontal beam and vertical column of the steel structure under the action of horizontal load is calculated by the inflection point method. First, the shear force received by each layer of the structure is obtained through experiments, and the shear force is distributed to the two vertical columns according to the lateral stiffness. Taking the midpoint as the inflection point, the moments at both ends are calculated to obtain the moments at both ends of the vertical column. Using the fact that the moment at the node is zero, the moment at the beam end of the horizontal beam is calculated. The moments at the column end and beam end under the vertical load in S4.1 are superimposed with the moments at the corresponding cross-sections calculated by the horizontal load in S4.2. The stress σ1 at the measurement cross-section is obtained from the moments at the column end and beam end, and the strain value ε1 at the corresponding cross-section is obtained using the relationship between stress and strain ε = σ / E, where E is the elastic modulus.

[0024] S4.3 uses the force method to calculate the internal force generated by temperature. Since the steel structure is a symmetric structure, half of the steel structure is taken for calculation to obtain a two-time statically indeterminate structure, and the force method equations are listed:

[0025] ;

[0026] ;

[0027] where X1 and X2 are the forces of the redundant constraints;

[0028] The coefficient δ 11 is numerically equal to the displacement generated in the X1 direction under the action of the unit force X1 = 1 in the basic structure;

[0029] The coefficient δ 12 is numerically equal to the displacement generated in the X1 direction under the action of the unit force X2 = 1 in the basic structure;

[0030] The coefficient δ 21 is numerically equal to the displacement generated in the X2 direction under the action of the unit force X1 = 1 in the basic structure;

[0031] The coefficient δ 22 is numerically equal to the displacement generated in the X2 direction under the action of the unit force X2 = 1 in the basic structure;

[0032] The coefficient is the displacement generated in the X1 direction due to temperature;

[0033] The coefficient is the displacement generated in the X2 direction due to temperature;

[0034] Through the following formula

[0035] ;

[0036] where h is the height of the cross-section beam, α is the linear expansion coefficient, refers to the area of the moment diagram generated by the axial force, It refers to the area of the bending moment diagram generated by the bending moment. The positive and negative signs in the formula are specified as follows: the axial force is positive for tension, and t is positive for temperature rise; for the bending moment and temperature difference, their product determines the positive and negative signs: when the bending moment and temperature difference cause tensile deformation on the same side of the member, their product takes a positive value, otherwise a negative value;

[0037] t = 1 / 2 (t1 + t2);

[0038] Δ t = t2 - t1, and Δt is the height of the rectangular cross-section beam;

[0039] Obtain , and then obtain X1 and X2.

[0040] According to

[0041] ;

[0042] Among them, is the bending moment generated by the redundant unknown force X1 = 1, is the bending moment generated by the redundant unknown force X2 = 1;

[0043] Obtain the bending moment M, thus obtain the stress σ2 generated under the influence of temperature, and then obtain the strain ε2. Superimpose the two strains to obtain the total theoretical calculation value ε3;

[0044] S4.4 Perform superposition: Subtract the measured strain ε6 at each point under each temperature difference condition from the strain ε4 before loading to obtain the total actual measured strain value ε7. Compare the total theoretical calculation value ε3 with the total actual measured strain value ε7 to evaluate the influence of temperature difference on the structure and the error between the theoretical calculation and experimental data;

[0045] S5: Organize all the data recorded during the experiment. According to the organized data and analysis results, write an experimental report.

[0046] The beneficial effects of the present invention compared with the prior art are as follows:

[0047] 1. This system can simulate the common temperature difference environment encountered by steel structures in actual projects. Through the coordinated operation of the temperature control adjustable heating sheets on the outside and the cooling sheets on the inside, precise control of the temperature change of the steel structure is achieved. At the same time, the system also relies on the strong reaction frame and the delicate auxiliary frame design to ensure the safety and stability of the steel structure during the simulation process and can cope with various challenges of simulated loading.

[0048] 2. Adjustable horizontal jacks and vertical jacks are installed in the system, which can accurately simulate the horizontal and vertical loads borne by steel structures in actual projects, making the experimental environment closer to actual projects. This loading method allows for the overall mechanical property testing of steel structures, thereby deeply understanding and evaluating the mechanical properties of the entire structure under loads in different directions.

[0049] 3. The strain gauges at the key parts of the steel structure are combined with static strain collectors to achieve instant and accurate capture of strain data, providing rich and intuitive experimental evidence for students and researchers. This comprehensive and accurate data collection and analysis is of great significance for deeply understanding the performance characteristics of steel structures, optimizing structural designs, and predicting structural behaviors.

[0050] 4. This system not only provides an intuitive and vivid experimental platform for civil engineering students to help them more deeply understand and master the mechanical properties of steel structures under different temperature differences, but also improves the teaching effect. Through actual operations 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

[0051] The present invention will be further described in detail below with reference to the accompanying drawings:

[0052] Figure 1 is the overall structural schematic diagram of the present invention;

[0053] Figure 2 is the front view of the whole of the present invention;

[0054] Figure 3 is the connection schematic diagram between the reaction frame, auxiliary frame, horizontal jack, and vertical jack;

[0055] Figure 4 is the front view of the steel structure;

[0056] Figure 5 is the structural schematic diagram of the strain collector;

[0057] Figure 6 is the structural schematic diagram of the heater;

[0058] Figure 7 is the structural schematic diagram of the cooler;

[0059] Figure 8 is the connection relationship diagram among the steel structure, cooling fins, heat sinks, and cooling fans;

[0060] Among them, 1 is the reaction frame, 2 is the auxiliary frame, 3 is the steel structure, 4 is the horizontal jack, 5 is the vertical jack, 6 is the upper cross beam, 7 is the lower cross beam, 8 is the left column, 9 is the right column, 10 is the upper longitudinal beam, 11 is the lower longitudinal beam, 12 is the middle longitudinal beam, 13 is the front column, 14 is the rear column, 15 is the limit rod, 16 is the horizontal beam, 17 is the vertical column, 18 is the cooling fin, 19 is the cooler, 20 is the heating fin, 21 is the heater, 22 is the strain acquisition instrument, 23 is the heat dissipation fin, and 24 is the heat dissipation fan. Detailed implementation manner

[0061] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear and understandable, the present invention will be further described in detail in combination 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 used to limit the present invention. The technical solutions of the present invention will be described in detail below in combination with the embodiments and the accompanying drawings, but the protection scope is not limited by this.

[0062] As Figure 1 As shown in FIG. 8, the present invention provides a teaching system for simulating the force of a steel structure due to temperature change, including 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 arranged alternately 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 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 a strain gauge, and the strain gauge is pasted on the steel structure 3.

[0063] The reaction frame 1 includes an upper cross beam 6, a lower cross beam 7, a left column 8, and a right column 9. The upper cross beam 6 and the lower cross beam 7 are both horizontally arranged along the left and right directions, and the upper cross beam 6 is located above the lower cross beam 7. The left column 8 and the right column 9 are both kept vertical and symmetrically arranged left and right. The left and right ends of the upper cross beam 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 cross beam 7 are respectively fixedly connected to the lower ends of the left column 8 and the right column 9.

[0064] The auxiliary frame 2 is an "E"-shaped frame structure arranged in a vertical plane in the front-rear 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 in the front-rear direction. 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 vertical column 13 and the rear vertical column 14 are both vertical and symmetrically arranged front and rear. 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. On the upper end surface of each middle longitudinal beam 12, two vertically arranged limit rods 15 that are symmetrically arranged front and rear are respectively fixedly provided. The two limit rods 15 on all the middle longitudinal beams 12 maintain the same spacing.

[0065] A plurality of auxiliary frames 2 are arranged side by side in 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.

[0066] The steel structure 3 is a U-shaped structure with an opening downward. The steel structure 3 includes a horizontal beam 16 and two vertical columns 17. The horizontal beam 16 is horizontally arranged in the left-right direction. The two vertical columns 17 are symmetrically arranged in 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 inside the left vertical column 8 and the right vertical column 9 of the reaction frame 1. 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 surface of the middle longitudinal beam 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. The middle longitudinal beam 12 is used to support the horizontal beam 16 of the steel structure 3, and the front and rear two limit rods 15 are used to limit the front and rear positions of the steel structure 3.

[0067] A set of horizontal jacks 4 are respectively arranged between the two vertical columns 17 of the steel structure 3 and the left vertical column 8 and the right vertical column 9 of the reaction frame 1. A plurality of horizontal jacks 4 inside a set are evenly arranged in the vertical direction. The horizontal jacks 4 are horizontally placed in the left-right direction. The bases of the horizontal jacks 4 are respectively fixedly connected to the inner side surfaces of the left vertical column 8 and the right vertical column 9 of the reaction frame 1. One end of the actuating rod of the horizontal jack 4 faces the side of the same-side vertical column 17. When the actuating rod of the horizontal jack 4 extends, a horizontal acting force is applied to the left and right sides of the steel structure 3.

[0068] A set of vertical jacks 5 is provided between the horizontal beam 16 of the steel structure 3 and the upper cross beam 6 of the reaction frame 1. A plurality of vertical jacks 5 inside the set are arranged evenly along the left - right direction. The vertical jacks 5 are kept vertically set. The base of the vertical jack 5 is fixedly connected to the lower end face of the upper cross beam 6 of the reaction frame 1. One end of the actuating rod of the vertical jack 5 faces vertically downward towards the horizontal beam 16 of the steel structure 3. When the actuating rod of the vertical jack 5 extends, a vertically downward acting force is applied to the upper end of the steel structure 3.

[0069] The cooling mechanism includes cooling fins 18 and a cooler 19. A plurality of cooling fins 18 are all connected to the cooler 19, and the cooler 19 provides a cooling function for the cooling fins 18. A plurality of cooling fins 18 are respectively fixedly pasted on the inner side surfaces of the vertical columns 17 and the horizontal beam 16 of the steel structure 3, and the cooling fins 18 are used to cool the inner side surfaces of the vertical columns 17 and the horizontal beam 16 of the steel structure 3. The cooler 19 is fixedly arranged on the front column 13 of one of the auxiliary frames 2.

[0070] The heating mechanism includes heating fins 20 and a heater 21. A plurality of heating fins 20 are all connected to the heater 21, and the heater 21 provides a heating function for the heating fins 20. A plurality of heating fins 20 are respectively fixedly pasted on the outer side surfaces of the vertical columns 17 and the horizontal beam 16 of the steel structure 3, and the heating fins 20 are used to heat the outer side surfaces of the vertical columns 17 and the horizontal beam 16 of the steel structure 3. The heater 21 is fixedly arranged on the front column 13 of one of the auxiliary frames 2.

[0071] The detection mechanism further includes a strain acquisition instrument 22. Strain gauges are fixedly pasted on the tops and bottoms of the two vertical columns 17 of the steel structure 3, and at the same time, strain gauges are also fixedly pasted at 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 acquisition instrument 22.

[0072] The teaching system is also provided with a heat dissipation mechanism. The heat dissipation mechanism includes heat dissipation fins 23 and a heat dissipation fan 24. The heat dissipation fins 23 are fixedly pasted on the inner side surfaces of the horizontal beam 16 and the vertical columns 17 of the steel structure 3, and the heat dissipation fan 24 is fixedly arranged on the heat dissipation fins 23. The heat dissipation fins 23 are used to adsorb the heat on the steel structure 3, and the heat dissipation fan 24 is used to volatilize the heat adsorbed inside the heat dissipation fins 23.

[0073] According to a teaching method of a teaching system for simulating the force of a steel structure due to temperature change, it includes the following steps

[0074] S1: Place the steel structure 3 at room temperature to ensure no interference from other external temperatures; measure and record the strain data ε4 at the corresponding positions. ε4 is the initial reading of the strain gauge. Determine the time length 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;

[0075] S2: Apply the predetermined horizontal and vertical loads to the steel structure 3 using the horizontal jack 4 and the vertical jack 5; after the loads are applied stably, record the data of each strain gauge as the initial strain value ε5; these data will be used as the basis for subsequent analysis;

[0076] S3: Heat the outside of the steel structure 3 through the outside heating mechanism, and at the same time start the inside cooling mechanism to keep the inside temperature of the steel structure 3 at room temperature and constant; the heating mechanism and the cooling mechanism are precisely controlled to ensure that each temperature increase can cause a temperature difference of 10°C between the inside and outside of the steel structure 3; repeat this process, gradually increase the outside temperature, and wait for a period of time after each temperature difference change to ensure that the strain gauge readings are stable; after each temperature difference change is stable, record the data ε6 of each strain gauge;

[0077] S4: According to the predetermined applied load, the geometric dimensions, and the elastic modulus parameters of the steel structure 3, calculate the internal force of the steel structure 3 using the following method, and measure the strain of the cross-section through the internal force calculation; the calculation method is as follows:

[0078] S4.1 Calculate the bending moments at the column ends of the vertical columns 17 and the beam ends of the horizontal beams 16 under the action of the vertical load using the moment distribution method; first, calculate the beam-column distribution coefficient Ki according to the formula Ki = Di / ΣDi, where Ki is the distribution coefficient and Di is the linear stiffness of the beam or column, look up Table 1 (Table of Fixed-End Moments and Fixed-End Shears of Beams under Loaded Conditions) to obtain the fixed-end moments, and distribute them according to the distribution coefficient, and transfer and distribute the moments to calculate the beam-end and column-end bending moments.

[0079] Table 1

[0080]

[0081] In S4.2, the moment method is used to calculate the moments generated by the horizontal beam 16 and vertical column 17 of the steel structure 3 under horizontal loads. First, the shear force received by each layer of the structure is obtained through experiments, and the shear force is distributed to the two vertical columns 17 according to the lateral stiffness. Taking the midpoint as the inflection point, the moments at both ends are calculated to obtain the moments at both ends of the vertical column 17. Using the fact that the moment at the node is zero, the moment at the beam end of the horizontal beam 16 is calculated. The moments at the column end and beam end under the vertical load in S4.1 are superimposed with the moments at the corresponding cross-sections calculated by the horizontal load in S4.2. The stress σ1 at the measurement cross-section is obtained from the moments at the column end and beam end, and the strain value ε1 at the corresponding cross-section is obtained using the relationship between stress and strain ε = σ / E, where E is the elastic modulus.

[0082] S4.3 uses the force method to calculate the internal forces generated by temperature. Since the steel structure 3 is a symmetric structure, half of the steel structure 3 is taken for calculation to obtain a two-time statically indeterminate structure, and the force method equation is listed:

[0083] ;

[0084] ;

[0085] where X1 and X2 are the forces of the redundant constraints;

[0086] The coefficient δ 11 is numerically equal to the displacement generated in the X1 direction by the basic structure under the action of the unit force X1 = 1 alone;

[0087] The coefficient δ 12 is numerically equal to the displacement generated in the X1 direction by the basic structure under the action of the unit force X2 = 1 alone;

[0088] The coefficient δ 21 is numerically equal to the displacement generated in the X2 direction by the basic structure under the action of the unit force X1 = 1 alone;

[0089] The coefficient δ 22 is numerically equal to the displacement generated in the X2 direction by the basic structure under the action of the unit force X2 = 1 alone;

[0090] The coefficient is the displacement generated in the X1 direction by temperature;

[0091] The coefficient is the displacement generated in the X2 direction by temperature;

[0092] Through the following formula

[0093] ;

[0094] where h is the height of the cross-sectional beam and α is the linear expansion coefficient, It refers to the area of the bending moment diagram generated by the axial force. It refers to the area of the bending moment diagram generated by the bending moment. The positive and negative sign regulations in the formula are as follows: the axial force is positive for tension, and t is positive for temperature rise; for the bending moment and temperature difference, their product determines the positive and negative sign: when the bending moment and temperature difference cause tensile deformation on the same side of the member, their product takes a positive value, otherwise a negative value.

[0095] t = 1 / 2 (t1 + t2);

[0096] Δ t = t2 - t1, and Δt is the height of the rectangular cross-section beam.

[0097] Obtain , and then obtain X1 and X2.

[0098] According to

[0099] ;

[0100] Among them, is the bending moment generated by the redundant unknown force X1 = 1. is the bending moment generated by the redundant unknown force X2 = 1.

[0101] Obtain the bending moment M, thus obtain the stress σ2 generated under the influence of temperature, and then obtain the strain ε2. Superimpose the two strains to obtain the total theoretical calculation value ε3;

[0102] S4.4 Perform superposition: Subtract the measured strain ε6 at each point under each temperature difference condition from the strain ε4 before loading to obtain the total actual measured strain value ε7. Compare the total theoretical calculation value ε3 with the total actual measured strain value ε7 to evaluate the influence of temperature difference on the structure and the error between the theoretical calculation and experimental data.

[0103] S5: Organize all the data recorded during the experiment. According to the organized data and analysis results, write an experimental report.

[0104] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A teaching system for simulating the force of a steel structure due to temperature changes, characterized in that: The invention comprises a reaction frame (1), an auxiliary frame (2), a jack, a detection mechanism, a heating mechanism and a cooling mechanism, wherein 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 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 adhered to the steel structure (3); The auxiliary frame (2) comprises a front column (13); The steel structure (3) includes a horizontal beam (16) and two vertical columns (17); 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).

2. The teaching system for simulating the force under the temperature change of a steel structure according to claim 1, wherein: The reaction frame (1) comprises 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 both arranged horizontally 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 arranged symmetrically; 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).

3. The teaching system for simulating the force exerted by the temperature change of a steel structure according to claim 2, wherein: The auxiliary frame (2) is a "日"-shaped frame structure arranged in a vertical plane in the front-to-back direction, and further comprises an upper longitudinal beam (10), a lower longitudinal beam (11), a middle longitudinal beam (12), 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 are arranged front and back. The upper longitudinal beam (10) is symmetrically arranged; 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); 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); and two front-to-rear symmetrical vertical limit rods (15) are respectively fixedly arranged on the upper end surface of each middle longitudinal beam (12).

4. A teaching system for simulating the force of a steel structure due to temperature change according to claim 3, characterized in that: A plurality of auxiliary frames (2) are arranged in a left-right direction, the middle portion of a lower longitudinal beam (11) of the auxiliary frame (2) is fixedly connected to a lower cross beam (7) of the reaction frame (1), and the lower longitudinal beam (11) and the lower cross beam (7) are kept perpendicular; the middle portion of an upper longitudinal beam (10) of the auxiliary frame (2) is fixedly connected to an upper cross beam (6) of the reaction frame (1), and the upper longitudinal beam (10) and the upper cross beam (6) are kept perpendicular.

5. A teaching system for simulating the force of a steel structure due to temperature changes according to claim 3, characterized in that: The steel structure (3) is a U-shaped structure with an opening downward, wherein a horizontal beam (16) is horizontally arranged along the left-right direction, and two vertical columns (17) are symmetrically arranged along the left-right direction, and 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 both 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. A teaching system for simulating the stress of a steel structure due to temperature changes according to claim 5, characterized in that: 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. A teaching system for simulating the stress of a steel structure due to temperature changes according to claim 5, characterized in that: A set of vertical jacks (5) is provided between the horizontal beam (16) of the steel structure (3) and the upper cross beam (6) of the reaction frame (1). The vertical jacks (5) are kept vertically arranged. The base of the vertical jack (5) is fixedly connected to the lower end face of the upper cross beam (6) of the reaction frame (1). One end of the actuating rod of the vertical jack (5) faces vertically downward towards the horizontal beam (16) of the steel structure (3). When the actuating rod of the vertical jack (5) extends, a vertically downward acting force is applied to the upper end of the steel structure (3).

8. A teaching system for simulating the force of a steel structure due to temperature changes according to claim 5, characterized in that: The detection mechanism further includes a strain acquisition instrument (22). Strain gauges are fixedly pasted on the tops and bottoms of the two vertical columns (17) of the steel structure (3), and at the left and right ends and the mid-span position of the horizontal beam (16) of the steel structure (3) as well. The strain at the corresponding positions is measured through the strain gauges. All the strain gauges are connected to the strain acquisition instrument (22).

9. A teaching method for a teaching system for simulating the stress of a steel structure due to temperature changes according to any one of claims 5-8, characterized in that, including the following steps S1: Place the steel structure (3) at room temperature to ensure no other external temperature interference. Measure and record the strain data ε4 at the corresponding positions. ε4 is the initial reading of the strain gauge. Determine the time length 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 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 be used as the basis for subsequent analysis. S3: Heat the outside of the steel structure (3) through the outside heating mechanism, and at the same time start the inside cooling mechanism to keep the inside temperature of the steel structure (3) at room temperature and keep it constant. The heating mechanism and the cooling mechanism are precisely controlled to ensure that a temperature difference of 10 °C is generated between the inside and outside of the steel structure (3) every time the temperature is increased. Repeat this process, gradually increase the outside temperature, and wait for a period of time after each temperature difference change to ensure that the strain gauge readings are stable. After each temperature difference change is stable, record the data ε6 of each strain gauge. S4: According to the predetermined applied load, the geometric dimensions and elastic modulus parameters of the steel structure (3), use the following method to calculate the internal force of the steel structure (3), and measure the strain of the cross-section through the internal force calculation. The calculation method is as follows S4.1 Use the moment distribution method to calculate the moments at the column ends of the vertical columns (17) and the beam ends of the horizontal beam (16) under the action of the vertical load. First, calculate the beam-column distribution coefficient Ki according to the formula Ki = Di / ΣDi, where Ki is the distribution coefficient and Di is the linear stiffness of the beam or column. Check the "Table of Fixed-End Moments and Fixed-End Shears of Beams under Loaded Conditions" to obtain the fixed-end moments, and distribute them according to the distribution coefficient, and transfer and distribute the moments to calculate the beam-end and column-end moments. In S4.2, the moment method is used to calculate the moments generated in the horizontal beams (16) and vertical columns (17) of the steel structure (3) under the action of horizontal loads. First, the shear force received by each floor structure is obtained through experiments. The shear force is distributed to the two vertical columns (17) according to the lateral stiffness. Taking the midpoint as the inflection point, the moments at both ends are calculated to obtain the moments at both ends of the vertical columns (17). Using the fact that the moment at the node is zero, the moment at the beam end of the horizontal beam (16) is calculated. The moments at the column ends and beam ends under the action of the vertical load in S4.1 are superimposed with the moments at the corresponding cross-sections calculated under the horizontal load in S4.

2. The stress σ1 at the measurement cross-section is obtained from the moments at the column ends and beam ends. Using the relationship between stress and strain ε = σ / E, the strain value ε1 at the corresponding cross-section is obtained, where E is the elastic modulus. In S4.3, the force method is used to calculate the internal force generated by temperature. Since the steel structure (3) is a symmetric structure, half of the steel structure (3) is taken for calculation to obtain a two-time statically indeterminate structure, and the force method equation is listed: ； ； where X1 and X2 are the forces of the redundant constraints; Coefficient δ 11 Numerically equal to the displacement of the basic structure along the X1 direction under the action of the unit force X1 = 1 alone; Coefficient δ 12 Numerically equal to the displacement of the basic structure in the X1 direction under the action of a unit force X2 = 1 alone; Coefficient δ 21 Numerically equal to the displacement of the basic structure in the X2 direction under the action of a unit force X1 = 1 alone; Coefficient δ 22 Numerically equal to the displacement of the basic structure along the X2 direction under the action of a unit force X2 = 1 alone; Coefficient is the displacement in the X1 direction generated by temperature; Coefficient is the displacement in the X2 direction generated by temperature; Through the following formula ； where h is the height of the sectional beam and α is the coefficient of linear expansion, refers to the area of the bending moment diagram generated by the axial force, refers to the area of the bending moment diagram generated by the bending moment. The positive and negative signs in the formula are specified as follows: the axial force is positive for tension, t is positive for temperature rise; for the bending moment and temperature difference, their product determines the positive and negative signs: when the bending moment and temperature difference cause tensile deformation on the same side of the member, their product is taken as positive, otherwise negative; t = 1 / 2 (t1 + t2); Δ t = t2 - t1, where Δt is the height of the rectangular cross-section beam; Obtain , and then obtain X1 and X2; According to ； Among them, is the bending moment generated by the redundant unknown force X1 = 1, is the bending moment generated by the redundant unknown force X2 = 1; the moment M is obtained, thus 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 total theoretical calculation value ε3; In S4.4, superposition is carried out: the difference between the measured strain ε6 at each point under each temperature difference condition and the strain ε4 before loading is taken to obtain the total actual measured strain value ε7. The total theoretical calculation value ε3 is compared with the total actual measured strain value ε7 to evaluate the influence of temperature difference on the structure and the error between the theoretical calculation and the experimental data; In S5: All the data recorded during the experiment are sorted out. According to the sorted data and the analysis results, an experimental report is written.

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