A shear force distribution method demonstration device and a measurement method

Abstract

This invention discloses a shear force distribution demonstration device and measurement method, belonging to the field of structural engineering teaching technology. The device includes a base, a support mechanism, a loading mechanism, a demonstration mechanism, and a measurement mechanism. The support mechanism is a frame structure with sliding rails; the loading mechanism has replaceable supports with switchable constraints; the demonstration mechanism uses replaceable vertical columns with four-jaw chuck sleeves; and the measurement mechanism includes a strain measurement module, an S-shaped tension sensor, and a positioning ruler. This device adopts a fully modular, quick-release design, allowing for rapid switching between series and parallel systems, column constraint forms, and parameters. It simultaneously demonstrates the core knowledge points of inter-story force transmission in series and intra-story force distribution in parallel, verifying the shear force distribution law through measured data. This invention is easy to operate, combining visualization and quantitative measurement, effectively solving the pain points of abstract and difficult-to-understand traditional teaching methods, and significantly improving teaching effectiveness.

Description

Technical Field

[0001] This invention relates to the technical field of teaching demonstration devices for structural engineering, specifically a teaching demonstration device for demonstrating the principle of shear force distribution method. Background Technology

[0002] In structural mechanics, the "shear force distribution method" is a core foundational knowledge point for majors such as civil engineering and mechanics. Its core logic revolves around "stiffness matching, constraint conditions, and quantitative relationship of shear force in vertical columns of series and parallel systems." It is a key prerequisite for students to understand the law of force transmission in structures and to learn the analysis of complex frame structures.

[0003] However, current teaching practices of shear force distribution methods have significant drawbacks: traditional teaching relies heavily on textbook formula derivation and blackboard drawing explanations. Abstract stiffness calculations, shear force distribution ratios, and displacement superposition principles are difficult to present visually. Students are prone to confuse the core differences between "deformation superposition in series systems" and "uniform lateral displacement and stiffness components in parallel systems," and lack an intuitive understanding of how changes in constraints affect shear force distribution.

[0004] Existing teaching aids often have functional limitations: they can only demonstrate single parallel or series systems; most lack precise quantitative measurement components, relying solely on students' visual observation of the column's bending deformation, failing to obtain specific data such as strain, bending moment, and shear force; and the demonstrations are not adaptable to various column shapes. This prevents the teaching aids from accurately presenting the quantitative correspondence between stiffness and shear force / bending moment; the lack of replaceable and adjustable modular structures makes it difficult to quickly change support types or switch column parameters, hindering the conduct of multivariate control experiments. Students cannot intuitively perceive the influence of constraint type, stiffness magnitude, column height, and column shape on shear force distribution, making it difficult to deeply integrate theoretical derivation with practical phenomena, and failing to establish a quantitative cognitive framework for stiffness-shear force-bending moment, thus affecting their deep understanding of the core logic of the shear force distribution method and their ability to apply knowledge.

[0005] With the increasing emphasis on practical teaching in engineering education, there is a need for a teaching demonstration device that is simple in structure, easy to operate, and fully functional. This device can intuitively demonstrate the differences in shear force distribution in series and parallel systems, flexibly switch constraint conditions, and help students quickly understand the core principles of the shear force distribution method through quantitative measurement and visual indicators. It compensates for the lack of connection between abstract theory and practical perception in traditional teaching, improving teaching effectiveness and students' ability to apply knowledge. Based on this, this invention proposes a demonstration device embodying the shear force distribution method to address the problems existing in the prior art. Summary of the Invention

[0006] The purpose of this invention is to provide a shear force distribution demonstration device to address the difficulties in visually representing the shear force distribution ratio mentioned in the background art, as well as the inability to flexibly adjust the stiffness and height of the vertical columns, the inability to flexibly change the supports to demonstrate shear force distribution, the inability to flexibly change the series and parallel structures of the structure, and the inability to adapt to various types of columns. It is hoped that this device will improve students' learning efficiency.

[0007] To achieve the above objectives, the present invention provides a shear force distribution method demonstration device with the following technical solution: A shear force distribution method demonstration device and method, comprising a base, a support mechanism, a loading mechanism, a demonstration mechanism, and a measuring mechanism. The base is a rigid load-bearing structure. The support mechanism is a two-layer frame structure with slide rails, fixedly connected to the base by bolts. The loading mechanism includes: a loading control component, a loading execution component, and a transmission component. The loading control component and the loading execution component are connected to the support mechanism by bolts, and the loading control component and the loading execution component are connected by the transmission component. The loading execution component is fixedly connected to the vertical column via a replaceable support. The demonstration mechanism includes multiple vertical columns arranged at intervals along the loading direction and a telescopic bracket. Four-jaw chuck sleeves are installed on the upper and lower parts of the vertical columns. The lower part of the first-layer vertical column is fixedly connected to the telescopic bracket via a four-jaw chuck sleeve, and the upper part is connected to the replaceable support via a four-jaw chuck sleeve. The lower part of the second-layer vertical column is connected to the four-jaw chuck sleeve via a replaceable support, and the upper part is connected to the telescopic bracket via a four-jaw chuck sleeve. The telescopic support is installed at the bottom of the first-floor columns and the top of the second-floor columns. The support is bolted to the base plate and the transverse loading plate. It employs a combination design of replaceable supports and replaceable vertical columns. The replaceable supports include both fixed and hinged supports, allowing for quick switching of constraint types to fully realize the core principles of shear force distribution under different constraint conditions. The connection between the upper and lower ends of the vertical column relies on a four-jaw chuck sleeve. When clamping the vertical column, first rotate the locking wrench counterclockwise to open the four jaws, insert the vertical column, manually center it, and then rotate the four jaws clockwise to retract and clamp the vertical column.

[0008] The measurement mechanism of this device uses a strain gauge half-bridge connection method to measure the bending moment of the vertical column. The slope of the bending moment diagram is the shear force to be calculated. An external tensile force is applied and read by an S-shaped tension sensor, and the shear force distribution method is directly verified using measured data. A positioning ruler reads the horizontal displacement, visually demonstrating the deformation pattern: in a parallel system, the displacement of the vertical columns in the same layer is consistent; in a series system, the deformation exhibits superposition characteristics between layers. The strain gauge bridge connection method of this device is not limited to a half-bridge but can also be used for quarter-bridge and full-bridge connections. The quarter-bridge connection method requires only one strain gauge on the section of the vertical column to be measured, and with the built-in compensation gauge of the strain gauge, shear force measurement can be achieved. It is suitable for demonstration scenarios with lower measurement accuracy requirements. The full-bridge connection method requires four strain gauges symmetrically arranged on the section of the vertical column to be measured, forming a full-bridge circuit through wires. It offers the highest measurement accuracy and is suitable for high-precision experimental scenarios. All three connection methods can be adapted to this device by adjusting the number of strain gauges and the connection method, while maintaining the same core measurement principle.

[0009] Preferably, the base is a steel plate with several mounting holes for fitting bolts. The mounting holes allow for fixed connection to the support mechanism and the demonstration mechanism using bolts.

[0010] Preferably, the frame structure of the support mechanism is a portal frame. The bottom surface of the portal frame is fixed to the predetermined mounting holes of the base by bolts. Two connection positions for assembling vertical slide rails are provided on the side columns of the portal frame. The vertical slide rails are connected to the side columns of the portal frame by bolts. The two ends of the horizontal slide rails are fixed to the side protrusions of the horizontal and vertical slide rails by bolts. The side protrusions of the horizontal and vertical slide rails match the side protrusions of the vertical slide rails, thus forming a sliding fit.

[0011] Preferably, the loading control component includes a pulley base, a pulley shaft, a pin, a transmission pulley, a sleeve, and a displacement control rocker arm. A shaft hole and a pin hole connected to the shaft are provided on the left and right sides of the portal frame. The pulley shaft passes through the shaft hole, thus fitting with the outer circumferential surface of the pulley shaft. The pin is disposed in the pin hole. The transmission pulley is sleeved in the middle of the pulley shaft and coaxially fitted with the pulley shaft. Two sleeves are provided, respectively sleeved on the pulley shaft at positions on both sides of the transmission pulley. One end of the pulley shaft is fixedly connected to the displacement control rocker arm by bolts. The loading position of the loading control component can be selected to adapt to the driving requirements of the upper and lower loading execution components.

[0012] Preferably, the loading execution component is a rigid transverse loading plate with one or two layers; the rigid transverse loading plate is provided with replaceable supports; the bottom and top of the rigid transverse loading plate are provided with grooves extending along the length direction, and the grooves are adapted to the top protrusions of the horizontal slide rail to form a sliding fit.

[0013] Preferably, the transmission assembly includes a connecting plate, a steel wire, and a transmission pulley; a preset connection space for the transverse loading plate; the transverse loading plate is fixedly connected to the connecting plate by bolts; the connecting plate is fixedly connected to the S-shaped tension sensor by bolts; one end of the steel wire passes through the aluminum sleeve to form a closure and is hooked to the hook of the S-shaped tension sensor; the other end of the steel wire passes around the rim of the transmission pulley and forms a mating connection with the transmission pulley.

[0014] Preferably, the demonstration mechanism includes multiple vertical columns, a four-jaw chuck sleeve, and an adjustable support. The vertical columns are connected to four-jaw chuck sleeves on both the upper and lower sides, and the connection between the sleeve and the vertical column is locked by the synchronous rotation of the four jaws, achieving stable clamping. The replaceable support is fixedly connected to the horizontal loading plate in one method; the other method is a hinged connection, for example, the upper part of the four-jaw chuck sleeve of one vertical column is rotatably connected to the lower hinged support of the horizontal loading plate via bolts. The vertical columns are made of fiberglass rod, a material with high strength and elasticity, which meets experimental verification requirements. The bending stiffness of the four-jaw chuck sleeve is much greater than that of the vertical column, preventing the sleeve's own deformation from interfering with the force and accuracy of the column.

[0015] Preferably, high-precision metal foil strain gauges are used in a half-bridge configuration. One set of strain gauges is installed on the hinged column near the fixed end of the pure bending section, and one set of strain gauges is installed on each of the pure bending sections near the ends of the fixed columns. The strain gauges are low-temperature welded to the surface of the vertical column, with the sensitive grid parallel to the longitudinal direction of the vertical column. The strain gauges are connected to a multi-channel static strain gauge via wires. The bridge configuration can also be adjusted to achieve quarter-bridge and full-bridge connections by changing the number of strain gauges and the wire connection method. An S-shaped tension sensor is connected in series between the transverse loading plate and the transmission steel wire. One end of the S-shaped tension sensor is rigidly connected to the transverse loading plate via bolts, and the other end is hooked to the transmission steel wire via a hook. Two positioning rulers are rigidly fixed to the upper and lower horizontal slide rails, respectively. The moving end is aligned with the corresponding transverse loading plate, and the measurement direction is consistent with the loading direction. During loading, the displacement values ​​at each level are recorded, and the vertical column is centered to avoid force errors caused by installation misalignment. In a parallel system, the displacement of the vertical column is equal to the displacement of the corresponding loading plate. In a series system, the displacement of the first-layer vertical column is the displacement of the lower-layer loading plate, and the displacement of the second-layer vertical column is the difference between the displacements of the upper and lower loading plates.

[0016] Compared with the prior art, the beneficial effects of the present invention are: the shear force distribution demonstration device: (1) The measurement mechanism overcomes the problem that traditional teaching aids cannot quantitatively describe the shear force. The shear force of the vertical column can be obtained by calculating the slope from the measured bending moment. The measurement system supports synchronous data acquisition and export in Excel format, and the inherent laws can be analyzed through the recorded data. At the same time, in order to meet the requirements of small loads and high precision in the teaching of shear force distribution method, the half-bridge method can improve the accuracy of the data. A new shear force verification component has been set up. It is simple to operate, the reading is intuitive, and it is suitable for classroom demonstration.

[0017] (2) The demonstration mechanism includes replaceable supports such as fixed supports and hinged supports, which can be quickly fixed to the quick-release frame with bolts, and can flexibly switch the node constraint type; only the four-jaw chuck needs to be locked or released to adapt to vertical column components of different shapes; the telescopic bracket adjusts the height of the vertical column, and multiple sets of comparative experiments with different vertical column stiffness, shape, height and constraint type can be carried out afterward to make the results more convincing. The upper-level series system can reflect the equal distribution of forces between layers. The experiment achieves the dual teaching effect of "intuitive demonstration + data verification", which solves the defect of traditional teaching aids that cannot intuitively show the shear force distribution process.

[0018] (3) The whole adopts a fully modular quick-disassembly design. The support mechanism uses pins and bolts to quickly disassemble the steel back plate and frame. The loading mechanism and the demonstration mechanism are connected by lifting rings. All measuring parts are completed by bolts or welding to achieve the purpose of quick positioning. The main parts are steel and other hard materials to ensure the stability of the structure. This project takes lightweight prefabricated structure as the research object, with "small size, easy disassembly, and good interactivity" as the core. It starts from four links: "assembly-constraint, replacement of vertical columns, adjustment of vertical column height-loading action-data processing and verification", and takes "combination of practice and theory" as the main line to enhance students' intuitive understanding of "shear force distribution method".

[0019] (4) The series and parallel structures can be realized by changing the loading position, and the loading can be stopped at any time. The loading relationship is clear and identifiable. Students can intuitively observe that "when the load of the series system is only applied to the top, the two columns deform together, and when the load of the parallel system is applied to the first floor, only the first floor column deforms." This strengthens the students' understanding of the correspondence between theoretical knowledge and practical phenomena. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a partial schematic diagram of the connection between the horizontal loading plate and the vertical column; Figure 3 Schematic diagram of the loading pulley; Figure 4 This is a partial schematic diagram of the loading connection plate for the S-shaped tension sensor. Figure 5 Schematic diagram of a four-jaw chuck sleeve; Figure 6 This is a flowchart of the design method of the present invention; Figure 7 shows a typical engineering schematic diagram and a simulation schematic diagram of the present invention.

[0021] Explanation of reference numerals in the attached drawings: 1-1, Base plate; 1-2, Portal frame; 1-3, Vertical slide rail; 1-4, Horizontal slide rail; 1-5, Connecting piece for horizontal and vertical slide rails; 2-1.1, Pulley base; 2-1.2, Pulley shaft; 2-1.3, Pin; 2-1.4, Sleeve; 2-1.5, Transmission pulley; 2-1.6, Displacement control rocker arm; 2-2, Horizontal loading plate; 2-2.1, Connecting plate ; 2-3.1, Lifting ring; 2-3.2, Steel wire; 3-1, Vertical column; 3-2, Four-jaw chuck sleeve; 3-2.1, Jaws; 3-2.2, Adjusting knob; 3-2.3, Square connecting plate; 3-3, Telescopic bracket; 3-4, Replaceable support; 4-1.1, Strain gauge; 4-1.2, Strain gauge; 4-1.3, Wire; 4-2, Positioning ruler; 4-3, S-type tension sensor. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without innovative labor are within the scope of protection of the present invention.

[0023] Please refer to the appendix. Figure 1 This invention provides a shear force distribution demonstration device, comprising a support mechanism, a loading mechanism, a demonstration mechanism, and a measurement mechanism. The support structure includes a base plate 1-1 and a portal frame 1-2. The loading mechanism includes a transmission pulley 2-1.5, a displacement control rocker arm 2-1.6, a transverse loading plate 2-2, and a transmission component 2-3. The demonstration mechanism includes a vertical column 3-1, a small four-jaw chuck sleeve 3-2, a telescopic bracket 3-3, and a replaceable support 3-4. The measurement mechanism includes a strain gauge 4-1.1, a strain meter 4-1.2, a wire 4-1.3, a positioning ruler 4-2, and an S-shaped tension sensor 4-3.

[0024] The base plate 1 of the support mechanism is connected to the portal frame 1-1 by bolts. This connection method can ensure the overall stability of the device and avoid shaking during loading. The design of the portal frame 1-1 can further enhance the overall load-bearing capacity and prevent the frame from deforming due to excessive load. The vertical guide rail 1-3 is connected to the portal frame 1-2 by bolts. The horizontal guide rail 1-4 is connected to the vertical guide rail 1-3 by the horizontal vertical slide rail connector 1-5, which prepares the conditions for subsequent loading.

[0025] In the loading mechanism, pulley base 2-1.1 provides stable mounting support for the pulley shaft. A pulley shaft 2-1.2 is coaxially fitted on pulley base 2-1.1, allowing free rotation and providing a flexible rotation node for the transmission pulley. Pulley shaft 2-1.2 and transmission pulley 2-1.5 are coaxially fitted and rotate synchronously through a groove fit, ensuring that the operating force of the displacement control rocker is accurately transmitted to the transmission pulley and preventing slippage. Sleeves 2-1.4 are coaxially fitted on both sides of transmission pulley 2-1.5 on pulley shaft 2-1.2 to limit the axial position of transmission pulley 2-1.5, preventing axial displacement during rotation and ensuring the wire remains within the pulley groove. -1.2 is connected to the displacement control rocker arm 2-1.6 by bolts. By rocking the displacement control rocker arm, the pulley shaft can be easily driven to rotate, achieving labor-saving operation. At the same time, a pin 2-1.3 is coaxially fitted on the pulley base 2-1.1. The pin 2-1.3 can be inserted and removed. When the pin 2-1.3 is removed, the pulley shaft 2-1.2 can be rotated by rocking the displacement control rocker arm 2-1.6, which is convenient for loading operation. When inserted, it can lock the pulley shaft, realizing the immediate fixation of the transmission pulley, which is convenient for pausing the demonstration at a specific displacement position. A connecting plate 2-2.1 is fixed on the transverse loading plate 2-2. The connecting plate 2-2.1 is fixed to the S-type tension sensor 4-3 by screws. The other end of the S-type tension sensor 4-3 is connected to the steel wire 2-3.2 through the hook 2-3.1. Each of the first and second layer transverse loading plates is equipped with an independent S-shaped tension sensor 4-3 for individually acquiring the loading shear force of the corresponding layer, supporting independent measurement and superposition calculation of the force when both layers are loaded simultaneously. By rotating the transmission pulley 2-1.5 to tighten the pulling wire 2-3.2, the rotational motion of the pulley can be converted into the horizontal linear motion of the transverse loading plate, achieving smooth driving of the horizontal displacement of the transverse loading plate 2-2. The loading control component 2-1 is fixed to the base mounting positions of the portal frame 1-2 at different heights via bolts, enabling the loading execution component 2-2 to switch between horizontal loading on the first or second layer, and completing the series-parallel system conversion with the replaceable support 3-4.

[0026] The parallel system implementation in the demonstration mechanism: Two vertical columns are set on the first floor, with identical materials, cross-sections, and heights. One column is fixed at both ends, while the other is fixed at the lower end and hinged at the upper end. The columns are clamped using a four-jaw chuck sleeve 3-2, and the height of the columns is locked using a telescopic bracket 3-3, ensuring that the tops of both columns are connected to the rigid transverse loading plate 2-2 on the first floor. Strain gauges are placed on the section of the column to be tested and connected to strain gauges 4-1.1. A positioning ruler 4-2 is fixed to the horizontal slide rail on the first floor, with its moving end attached to the transverse loading plate. The calculated lateral stiffness ratio between the column with both ends fixed and the column with one end fixed and the other hinged is 4:1. The pin 2-1.3 of the first-floor loading control component is pulled out, and the displacement control rocker 2-1.6 is rocked. This drives the transverse loading plate 2-2 on the first floor to move smoothly along the horizontal slide rail via the transmission assembly, applying a horizontal load. After loading, the total shear force applied by the S-shaped tension sensor is recorded. V , strain gauge 4.1.1 strain reading. Calculate the theoretical shear force and theoretical bending moment of the two vertical columns under horizontal load according to (1)(2)(3), and convert the measured bending moment and measured shear force of the two vertical columns according to (4)(5) to verify the core law of the shear force distribution method.

[0027] The demonstration system only implemented two-layer loading: First and second-layer horizontal loading plates and corresponding loading control components were installed. The first layer consisted of one column fixed at both ends and one column fixed at one end and hinged at the other. The second layer consisted of two vertical columns fixed at both ends. All four columns were identical in material, cross-section, and height. The bottom of the first-layer column was fixed to the base, and the top was connected to the first-layer horizontal loading plate. The bottom of the second-layer column was connected to the first-layer horizontal loading plate, and the top was connected to the second-layer horizontal loading plate, forming a complete two-layer series system. Strain gauges were installed on each column as required and connected to strain meters. Positioning rulers were installed on both layers of horizontal slide rails, respectively aligned with the corresponding layer's horizontal loading plate. The pin of the second-layer loading control component was pulled out, and the displacement control lever was cranked to apply graded horizontal loads. After each load was applied, the position was locked, and the total shear force of the second-layer S-shaped tension sensor was recorded. V , strain gauge 4.1.1 strain reading. Series inter-story load transfer, the sum of the theoretical shear forces of each column is equal to the total applied shear force. Calculate the theoretical shear force and theoretical bending moment of the four vertical columns under horizontal load according to (1)(2)(3), and convert the measured bending moment and measured shear force of the four vertical columns according to (4)(5), verifying the core law of the shear force distribution method. And demonstrate that inter-story load transfer does not change the law of shear force distribution according to stiffness in the same story, simultaneously covering the two core knowledge points of series and parallel connections.

[0028] The demonstration system was implemented with simultaneous loading on two layers: the device assembly was completely consistent with implementation method two, forming a two-layer series system. The first and second layers were respectively equipped with independent S-shaped tension sensors and loading control components, which could realize independent graded loading on the two layers. The shear force distribution coefficient of each vertical column on the first and second layers was calculated in advance, consistent with implementation method two. The loading control components on the first and second layers were operated respectively to apply graded horizontal loads simultaneously. After each load was completed, the loading positions of the two layers were locked, and the total shear force of the S-shaped tension sensor on the first layer and the total shear force of the S-shaped tension sensor on the second layer were recorded. The strain readings of the strain gauges on the two layers were collected simultaneously. The theoretical shear force and theoretical bending moment of the four vertical columns under horizontal load were calculated according to (1)(2)(3)(8)(9). The measured bending moment and measured shear force of the four vertical columns were obtained by conversion according to (4)(5), verifying the core law of the shear force distribution method.

[0029] This device can simulate three typical lateral resisting structural systems in civil engineering, conducting comparative demonstration experiments to help students establish a direct link between shear force distribution theory and engineering practice. Real-world images and device schematics corresponding to the three structural types are attached. Figure 7 Variable 1 Comparison and Verification: With the same loading method and unchanged constraints, the vertical column 4-1 with different stiffness was replaced, and the loading operation was repeated. The data changes were recorded, confirming that "the greater the stiffness, the higher the proportion of shear force distribution." Variable 2 Comparison and Verification: With the same loading method and unchanged stiffness of vertical column 4-1, the constraint form was changed, and the loading operation was repeated. The data changes were recorded, confirming "the difference in stiffness between rigid and hinged constraints." Variable 3 Comparison and Verification: With the same loading method and unchanged constraints, the telescopic support was adjusted to replace vertical column 4-1 with a different height. The loading operation was repeated, and the data changes were recorded, confirming that "the greater the height, the lower the proportion of shear force distribution."

[0030] In a single-layer parallel system, the shear force distribution pattern can be fully demonstrated through changes in constraint forms: by gradually loading and reading shear force, students can intuitively perceive the core logic that "supports with fixed ends have the strongest constraints and bear the largest shear force, while supports with one fixed end and one hinged end have weak constraints and bear the smallest shear force." Changing the lateral stiffness within the system is convenient and the variable is unique. In the upper-layer series system framework, forces are transmitted from top to bottom. Changing supports does not affect the core essence of inter-layer force transmission, directly proving that the equal transmission of shear force from bottom to top is determined by the force transmission path rather than the constraint form.

[0031] In the measurement mechanism, strain gauge 4-1.1 is a multi-channel static strain gauge, connected to strain gauge 4-1.2 via connecting wire 4-1.3. Strain gauge 4-1.2 is a high-precision metal foil strain gauge, fixed to the stress-bearing part of column member 3-1 using a low-temperature welding process. For a column with one hinged end on the first floor, only one set of two strain gauges needs to be attached to the pure bending section near the fixed end of the column. The sensitive grid is parallel to the longitudinal direction of the vertical column to ensure the accuracy of bending moment measurement, and the slope of the bending moment distribution of this column can be obtained. For the other three fixed columns, two sets of four strain gauges need to be attached, arranged in the pure bending section near the end of the column. The shear force of the column can be obtained by calculating the slope of the two sets of bending moments. The strain gauge has a built-in data processing system, which presets parameters such as the material elastic modulus and moment of inertia of the column member. It can automatically amplify and convert the collected strain signal, and finally display the magnitude of the distributed bending moment borne by each column member in real time in digital form, realizing the automatic conversion of "strain-stress-bending moment" and avoiding errors in manual calculation. It also supports data export, allowing the complete dataset to be exported in Excel format for students to conduct subsequent data processing and analysis, such as calculating the slope to obtain shear force for data analysis. If a quarter-bridge method is selected for the hinged column, one strain gauge is placed near the fixed end in the pure bending section, along with a temperature compensation gauge. The working gauge is connected to the corresponding channel of the strain gauge via wires, and the remaining wiring is completed according to the strain gauge instruction manual. During loading, the strain gauge reads the strain value of the working gauge and uses the formula to calculate the bending moment and shear force. If a full-bridge method is selected for the fixed column, two strain gauges are symmetrically placed on each end in the pure bending section. The four strain gauges are connected to the strain gauge via wires in a full-bridge circuit. The full-bridge method can compensate for temperature effects, improve measurement accuracy, and is suitable for high-precision quantitative analysis experiments.

[0032] Working Principle: First, the device configuration is completed according to the teaching demonstration requirements. This shear force distribution demonstration device uses a series-parallel system as its core carrier. Through the coordinated design of horizontal load transfer, column shear force distribution, and real-time measurement by strain gauges, it intuitively presents the core principle of "parallel stiffness components and series inter-story force transmission," enhancing the depth of the concept. The overall working principle revolves around three stages: load input and force transfer, shear force distribution, and data feedback and verification.

[0033] In the load input and force transmission, the demonstration mechanism adopts a vertical series-parallel structure of "base plate - first-floor double-column group - first-floor transverse loading plate - second-floor double-column group - second-floor transverse loading plate". The bottom of the first-floor column is fixed to the base plate, forming a closed force transmission path. The external horizontal load is transmitted through the lower or upper transverse loading plate via a hand-cranked pulley. Because the transverse loading plate is a rigid plate, it does not deform during the loading process, and the load can be transmitted to the column without loss, ensuring that the load is completely converted into shear force, laying a solid foundation for the load-bearing structure.

[0034] The shear force distribution follows the core principle of "equal lateral displacement in parallel systems and inter-layer force transmission in series systems", which means parallel transmission within the same layer and series transmission between layers.

[0035] (1) Parallel distribution within the same floor: The lateral displacement of the two columns in the same floor is consistent, and the shear force on the column is proportional to its own lateral stiffness. The first-floor column group is designed as a combination of a column with both ends fixed and a column with one end fixed and the other end hinged. The stiffness and column height of the two are consistent, so the shear force distribution ratio is 4:1. The relevant formulas are as follows: (6) (7) In the formula: For lateral stiffness, h The geometric height of the column, E For the elastic modulus of the material, I Let the moment of inertia of the cross section be... To provide lateral stiffness for vertical columns fixed at both ends, This indicates the lateral stiffness of a vertical column that is fixed at one end and hinged at the other.

[0036] (2) Parallel distribution comparison within the same floor: The lateral displacement of the tops of the two columns in the same floor is consistent, and the shear force on the column is proportional to its own lateral stiffness. Three control groups were added, each based on a single variable, changing only the stiffness, column height, and constraint form of one column in the same floor, while keeping other relationships unchanged. The quantitative influence of different factors on shear force distribution can be intuitively understood from formulas (1), (6), and (7).

[0037] (3) Inter-story series transmission: When only two stories are loaded, the total shear force of the upper and lower story columns is equal. One of the first-story column groups is fixed at one end and hinged at the other end; the other is fixed at both ends; the two upper-story vertical columns are all fixed, and the stiffness of the four vertical columns is exactly the same. Moreover, the shear force ratio between the fixed and hinged columns in the first story is still 4:1, which reflects the two knowledge points of "series inter-story force transmission" and "parallel stiffness component force". The upper and lower story columns form a series system through the transverse loading plate. When the two loading plates are loaded at the same time, the force transmission path has no branches. The total shear force of the first-story column group is equal to the sum of the total shear force of the two stories loaded. The total shear force of the second story is the actual reading of the corresponding S-type tension sensor. The relevant formulas for theoretical internal forces are as follows: (8) (9) In the formula: For the first layer j Theoretical shear force of the root column For the first layer j Root column allocation coefficient. This refers to the readings of the S-shaped tension sensors for the first and second floors. If the total shear force is input when both floors are loaded... When loading a single layer , which is the effective height.

[0038] Data feedback and verification: Based on the strain gauges of each column in the measuring mechanism, the bending moment of the cross section is calculated from the strain value, and then the shear force is obtained by calculating the slope. This realizes the transformation of abstract mechanical laws into intuitive data, which aligns with modern educational concepts. A positioning ruler welded to a horizontal guide rail is used to visually verify the consistency of lateral displacement in a parallel system. In a series system, the deformation superposition characteristics are visually demonstrated, helping to understand that the essence of inter-story shear force transmission is deformation continuity. The relevant formulas are as follows: (10) (11) (12) (13) In the formula: For the first i Layer j Lateral stiffness of the root column, This represents the total input shear force at a certain level. For the first i Layer j Measured shear force of the vertical column. This indicates the relative error of the shear force of the vertical column. This indicates the relative error of the bending moment of the vertical column.

[0039] Formula (10) can be used to verify the core principle of the shear force distribution method, and formula (11) can be used to verify the accuracy of the measurement data. Formulas (12) and (13) can be used to verify the theoretical internal forces and measured internal forces of each vertical column under different systems.

[0040] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A shear force distribution demonstration device, comprising a base, a support mechanism, a loading mechanism, a demonstration mechanism, and a measuring mechanism, characterized in that: The base (1-1) is a rigid load-bearing structure. The support mechanism includes a portal frame (1-2) with two sliding rails, which is fixedly connected to the base plate (1-1) by bolts. The loading mechanism includes a loading control component (2-1), a loading execution component (2-2), and a transmission assembly (2-3). The loading control component (2-1) and the loading execution component (2-2) are connected to the support mechanism by bolts. The loading control component (2-1) and the loading execution component (2-2) are connected by the transmission assembly (2-3). The loading execution component (2-2) is fixedly connected to the vertical column (3-1) by a replaceable support (3-4). The demonstration mechanism includes: multiple vertical columns (3-1) spaced apart along the loading direction; small four-jaw chuck sleeves (3-2) are installed on the upper and lower parts of the vertical columns (3-1); the lower end of the first-layer vertical column (3-1) is fixedly connected to the telescopic bracket (3-3) through the sleeve (3-2), and the upper end is connected to the replaceable support (3-4) through the sleeve (3-2); the lower end of the second-layer vertical column (3-1) is connected to the replaceable support (3-4) through the sleeve (3-2), and the upper end of the second-layer vertical column (3-1) is bolted to the telescopic bracket (3-3) through the sleeve (3-2). The measurement mechanism includes: a bending moment measuring component (4-1), a positioning ruler (4-2), and an S-shaped tension sensor (4-3). The bending moment measuring component (4-1) consists of a strain gauge (4-1.1), a strain gauge (4-1.2), and a wire (4-1.3). The strain gauge (4-1.1) and strain plate (4-1.2) are connected by a wire (4-1.3), and the positioning ruler (4-2) is fixed to the upper and lower horizontal slide rails (1-4). One end of the S-type tension sensor (4-3) is locked to the transverse loading plate (2-2) with a bolt, and the other end is connected to the steel wire (2-3.2) through a hook (2-3.1). The strain gauge (4-1.1) and the S-type tension sensor (4-3) are connected by a wire (4-1.3).

2. The frame structure (1-2) has two sets of mounting positions set at vertical intervals on both sides. The vertical slide rails (1-3) are fixedly connected to the frame structure (1-2) by bolts. The horizontal slide rails (1-4) are respectively matched with the vertical slide rails (1-3) of the corresponding layer. The horizontal slide rails (1-4) are provided with groove-type matching structures extending along the length direction on both sides. The matching structure forms a sliding fit with the protruding structure of the vertical slide rails (1-3). Each layer of horizontal slide rails (1-4) is provided with detachable limiting blocks at both ends. The bottom of the horizontal slide rails (1-4) is pre-set with locking holes that match the positioning holes of the vertical slide rails (1-3).

3. Two sets of base mounting positions are preset vertically at intervals on both sides of the frame structure (1-2). The load control component base (2-1.1) is fixedly connected to the corresponding layer base mounting position of the frame structure (1-2) by bottom bolts; a pulley shaft (2-1.2) and a pin (2-1.3) are coaxially fitted on the load control component base (2-1.1), a transmission pulley (2-1.5) is sleeved in the middle of the pulley shaft (2-1.2), and sleeves (2-1.4) are provided on both sides of the transmission pulley (2-1.5) for axial limiting. One end of the pulley shaft (2-1.2) is fixedly connected to the displacement control rocker (2-1.6) by bolts.

4. The loading execution component (2-2) includes two independently arranged rigid transverse loading plates, each with a preset mounting position. The plate is movably connected to the loading control component (2-1) of the same layer via the corresponding layer transmission component (2-3). Replaceable supports (3-4) are provided at the bottom and top of the first-layer transverse loading plate (2-2) and at the bottom of the second-layer transverse loading plate (2-2). The replaceable supports (3-4) are fixedly connected to the transverse loading plate by bolts. Both sides of the transverse loading plate are provided with boss-type mating structures extending along the length direction. These mating structures form a sliding fit with the groove of the horizontal slide rail (1-4). The first-layer and second-layer transverse loading plates (2-2) are respectively equipped with independent S-shaped tension sensors (4-3).

5. The shear force distribution demonstration device according to claim 1, characterized in that: The horizontal loading plate (2-2) can slide along the horizontal guide rail. Applying force to the corresponding loading control component (2-1) enables rapid conversion between series and parallel structures. When only one layer of loading control component (2-1) applies a horizontal load, the device is a parallel structure; when the first and second layers apply a horizontal load simultaneously or only the two layers apply a horizontal load, the device is a series structure. The vertical column group (3-1) can achieve column differentiation by changing its stiffness, height, or switching the replaceable support (3-4). Both the upper and lower ends of the vertical column are equipped with small four-jaw chuck sleeves (3-2), and the jaws can open and close radially synchronously to adapt to different shapes of vertical columns (3-1). The small four-jaw chuck sleeves (3-2) are connected to the integrated square connecting plate (3-2.3) by bolts. The connecting interface has threaded holes along the axial direction, and it can be directly fixed to the replaceable support (3-4) through the connecting interface without the need for additional connecting parts. The telescopic bracket (3-3) is a rigid structure that locks after vertical adjustment and has no horizontal deformation.

6. A method of demonstrating a shear force distribution method, characterized by: The total loading force was measured by the S-type tension sensor (4-3); the shear force on each column (3-1) was measured independently by the bending moment measuring component (4-1); the positioning ruler (4-2) was used to assist in the centering of the columns and to visually display the deformation pattern.

7. A demonstration method for shear force distribution according to claim 6, characterized in that: The formula for calculating the shear force distribution coefficient of each columnar member is as follows: (1) In the formula, Indicates the first i Layer j Root column distribution coefficient, This indicates the lateral stiffness of the corresponding vertical column.

8. The shear force distribution method demonstration method according to claim 6, characterized in that: The theoretical and measured formulas for calculating the internal forces of each columnar member are as follows: (2) (3) (4) (5) In the formula, The effective height of the column, To input the total shear force, Indicates the first i Layer j Theoretical internal force values ​​of the vertical column. Indicates the first i Layer j Measured internal force values ​​of the vertical column. The measured bending moment corresponding to the upper and lower strain gauges. E The elastic modulus of the vertical column. I Let be the moment of inertia of the vertical column. For strain gauge readings, k This is the bridge amplification factor. Specific value: for a quarter-bridge configuration. k =1. Half-bridge k =2. Full bridge k =4. x The distance between the centers of the strain gauges on the same vertical column. This is the distance from the neutral axis to the strain gauge bonding distance.

9. A demonstration method for shear force distribution according to claim 6, characterized in that, The method specifically includes the following steps: S1. Determine the demonstration system, including the installation location of the loading and control components and the types of replaceable supports. Calculate the shear force distribution coefficient for each vertical column on the same floor. The lateral stiffness of the corresponding vertical column is obtained. ; S2. Obtain the total shear force by applying a horizontal load through the loading control component (2-1) and recording the measured reading of the S-type tension sensor (4-3); S3. Theoretical internal force value, obtained based on formulas (1)(2)(3); S4. Measured internal force values, obtained based on formulas (4) and (5); S5. Theoretical and experimental comparison and verification: By comparing the theoretical internal forces of each vertical column with the measured internal forces, the core law of the shear force distribution method can be verified.

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