Large-span arch bridge large-scale reduced scale model test load self-adaptive loading method and system

Abstract

The invention discloses a large-span arch bridge large-scale reduced scale model test load self-adaptive loading method and system, and belongs to the technical field of bridge engineering structure tests. The system comprises a reduced scale model test piece used for manufacturing the reduced scale model test piece according to a reduced scale proportion and rigidity equivalence principle based on a target bridge, and setting a loading point at a preset position of an arch rib; the unconstrained self-adaptive loading device consists of a lever-pulley block and is used for applying a load to the loading point and allowing the model to freely deform in an unconstrained manner in the loading process; the transverse limiting devices are arranged on the two longitudinal sides of the reduced scale model test piece and used for limiting transverse displacement of the model and preventing instability; and the test system is used for collecting displacement, strain and arch foot internal force data of the model in the test process. According to the invention, long-term stable load application and unconstrained free deformation synchronous simulation of the model can be realized, and the real stress state and failure mode of the large-span arch bridge can be accurately restored.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge engineering structure test, more particularly to a large-span arch bridge large-scale model test load self-adaptive loading method and system. BACKGROUND

[0002] As a key structure in traffic engineering, the ultimate bearing capacity, stress state and failure mode of large-span arch bridge are of great importance to the safety of the structure. Scale model test is an effective means to explore the true stress and deformation characteristics of large-span arch bridge, and needs to be based on the similarity principle to realize the consistent simulation of the stress of the model and the real bridge.

[0003] At present, the commonly used loading methods in bridge scale model test mainly include: Jack loading method: only suitable for a few point short-term loading scene, difficult to meet the demand of long-term stable loading of large-span arch bridge.

[0004] Lever loading method: through torque balance to reduce the space occupation of counterweight, but the loading precision is low, and repeated loading adjustment is needed to reach the target load value.

[0005] Multi-point suspended weight method: suitable for multi-point long-term loading, but the test space requirement is very high, and it cannot adapt to the loading demand of large-span arch bridge large tonnage dead load.

[0006] The dead load of large-span arch bridge accounts for a large proportion, and the failure mode is mainly the compression of the cross section leading to overall instability under the guidance of dead load. The vertical constraint of the existing loading system easily changes the deformation mode and failure mode of the structure, resulting in distortion of the test parameters. In addition, the required load values of each loading point are inconsistent, and the conventional loading device cannot accurately apply non-uniform load. These problems restrict the accuracy and reliability of the scale model test of large-span arch bridge.

[0007] Therefore, how to provide a large-span arch bridge large-scale model test load self-adaptive loading method and system is a problem that needs to be solved by those skilled in the art. SUMMARY

[0008] Therefore, the present application provides a large-span arch bridge large-scale model test load self-adaptive loading method and system, which aims to solve the problems of constraint interference, low loading precision, large space requirement, and inability to adapt to multi-point non-uniform load in the existing loading method in large-span arch bridge large-scale model test, and to realize long-term stable load application, model unconstrained free deformation synchronous simulation, and accurate restoration of the true stress state and failure mode of large-span arch bridge.

[0009] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: A large-span arch bridge large-scale model test load self-adaptive loading method, comprising the following steps: S1: Based on the target bridge, a scaled-down model specimen is made according to the principle of scale ratio and stiffness equivalence, and loading points are set at the preset positions of the arch ribs. S2: Install a ground beam system at the test site, and install pulley units, lever units and slide systems corresponding to each loading point in sequence to form multiple lever-pulley loading units, thread the loading rope through and connect the loading mechanism; S3: Install displacement sensors, strain sensors, and arch foot internal force testing sensors on the model to establish a data acquisition system; S4: Preload is performed through the loading mechanism to eliminate gaps, and the fulcrum position of the corresponding lever unit is adjusted according to the measured load value at each loading point to make the load ratio at each point meet the design requirements. S5: Perform formal graded loading. After each loading reaches the target value, allow the system to stabilize at rest. Simultaneously collect displacement, strain, and arch foot internal force data until all test conditions are completed.

[0010] Furthermore, S2 also includes: installing lateral limiting devices on both sides of the model in the longitudinal direction, wherein a gap is left between the lateral limiting devices and the side of the model arch rib to allow the model to deform freely in the vertical direction but to limit its lateral displacement beyond a predetermined range.

[0011] Furthermore, in S4, the lever fulcrum is changed by adding or removing the adjusting steel plate on the lever unit or moving its installation position in the slide, thereby achieving stepless or stepped adjustment of the load amplification factor.

[0012] Furthermore, the loading mechanism is a manual or electric hoist, which applies the load by pulling the loading rope.

[0013] Furthermore, the scaling ratio is between 1:20 and 1:60.

[0014] An adaptive loading system for large-scale scaled-down model testing of a long-span arch bridge, employing the aforementioned method, includes: Scaled-down model specimens are used to create scaled-down model specimens based on the target bridge, according to the principle of scaled-down ratio and stiffness equivalence, with loading points set at preset positions on the arch ribs. An unconstrained adaptive loading device, consisting of a lever-pulley system, is used to apply loads to the loading points and allow the model to deform freely without constraints during the loading process. A lateral limiting device is arranged on both sides of the longitudinal direction of the scaled-down model specimen to limit the lateral displacement of the model and prevent instability. The testing system is used to collect data on the displacement, strain, and internal forces at the arch feet of the model during the test.

[0015] Furthermore, the unconstrained adaptive loading device includes: The ground beam system, fixed to the test site, serves as the foundation for device installation; Multiple pulley units are fixed to the ground beam system and are set corresponding to each loading point; Multiple lever units, each lever unit being movably mounted via a pin and associated with a corresponding pulley unit and a loading point; A slide system is used to install and allow adjustment of the position of the lever unit; The loading rope passes sequentially through the pulley unit and the lever unit to form a load transfer path; A loading mechanism, connected to the loading rope, is used to provide and control the loading force.

[0016] Furthermore, the fulcrum position of the lever unit is adjustable. By changing the fulcrum position, the load amplification factor of the lever unit can be adjusted, thereby adapting to the non-uniform load requirements of different loading points.

[0017] Furthermore, the lateral limiting device is a portal frame structure, including a vertically arranged main support, a lateral connecting member, and an adjustable lateral limiting component, wherein the lateral limiting component maintains a preset gap with the side of the model arch rib.

[0018] Furthermore, the testing system includes: The displacement testing module uses a wire displacement gauge and / or a total station, and is set up at multiple displacement testing sections of the model arch rib. The strain testing module uses fiber optic strain sensors and / or resistance strain gauges, which are arranged on multiple strain testing sections of the model arch rib. The arch foot internal force testing module adopts a split arch seat structure, with multiple pressure sensors arranged on the back and bottom of the arch seat, and calculates the arch foot internal force through static balance.

[0019] As can be seen from the above technical solution, compared with the prior art, the present invention provides an adaptive loading method and system for large-scale scaled model tests of long-span arch bridges, with the following specific beneficial effects: 1) By utilizing the self-sliding characteristics of the pulley system, the model can be free to deform without constraints during the loading process, effectively avoiding changes to the original failure mode of the structure caused by the loading system. Experimental verification shows that the model has high consistency with the stress response of the actual bridge. 2) The adjustable multiplier lever unit can accurately adapt to the non-uniform load requirements of each loading point, without the need for repeated load adjustment, and the load is stable in the long term. The stress distribution of the model matches the actual bridge well. 3) By leveraging the leverage effect, the actual amount of counterweight blocks used and the stacking space are greatly reduced, making it suitable for large-tonnage constant load loading scenarios; 4) The lateral restraint device significantly improves the lateral stability of the model, greatly increases the critical load factor, and effectively prevents the risk of lateral instability or collapse during the test. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 The structural layout diagram of the Tian'e Longtan Grand Bridge provided by this invention; Figure 2 A scaled-down model of the Tian'e Longtan Grand Bridge, showing its structural layout. Figure 3 Schematic diagram of a lateral limiting device for a portal frame; Figure 4 This is a cross-sectional strain test diagram; Figure 5 Diagram showing the internal forces at the arch foot; Figure 6 To load the overall system assembly drawing; Figure 7 This is a rendering of the loading device; Figure 8 Diagram of an unconstrained adaptive loading device; Figure 9 This is a schematic diagram of the arch foot of an unconstrained adaptive loading component. Figure 10 This is a schematic diagram of a typical unconstrained adaptive loading component. Figure 11 This is a schematic diagram of the loading point of an unconstrained adaptive loading component. Figure 12 Renderings of key components under unconstrained adaptive loading; Figure 13 Diagram of the lateral limiting frame; Figure 14 This is a rendering of a lateral limiting frame. Figure 15 This is a system for testing the reaction force of the arch foot. Detailed Implementation

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

[0023] Example 1: Embodiment 1 of this invention discloses an adaptive loading system for a large-scale scaled model test of a long-span arch bridge, comprising: Scaled-down model specimen: Designed based on the principle of stiffness equivalence, using a large-scale scaled-down approach, the main span and rise of the model are determined proportionally, and the loading points are arranged on the arch ribs at preset intervals.

[0024] Unconstrained adaptive loading device: Composed of a lever-pulley system, including a ground beam system, a pulley system, a lever system, and a slide system; the lever system is installed in the slide system via pins, and the pulley system is fixed to the ground beam system; the loading rope passes through the pulley system and the lever system in sequence to form a tension transmission path; the self-sliding characteristics of the pulleys enable unconstrained free deformation of the model and synchronous application of the load during the loading process, and the load amplification and adjustable multiplier characteristics of the levers adapt to the non-uniform load requirements of each loading point.

[0025] Lateral limiting device: including portal frame structure, arranged on both sides of the longitudinal direction of the arch rib, used to limit the lateral deformation of the model, prevent lateral instability during loading, and also serve as a safety protection measure against collapse.

[0026] The testing system includes a displacement testing module, a strain testing module, and an arch foot internal force testing module. The displacement testing module uses a wire displacement gauge and a total station. The strain testing module uses a fiber optic strain sensor and / or strain gauge. The arch foot internal force testing module uses the separate arch seat method, which calculates the arch foot internal force through pressure sensors arranged on the arch seat.

[0027] The unconstrained adaptive loading device specifically includes: Ground beam system: including ground beam I-beams, ground beam connectors and ground beam fixing bolts, used to provide the foundation for device installation.

[0028] Pulley system: including arch foot lower pulley, arch foot upper pulley, general lower pulley, general upper pulley and pulley fixing block.

[0029] Lever system: including arch foot loading lever, general loading lever and loading point lever.

[0030] Slide system: including loading slide fixing block, loading slide and lever adjustment steel plate, used to install and adjust the lever position and magnification.

[0031] Loading and adjustment components: including fixed loading rope, movable loading rope, loading hoist, pin shaft and arch force sensor.

[0032] The lateral limiting device specifically includes: Support structure: including ground-embedded steel plates, bottom steel plates, top steel plates, main I-beams and stiffening plates.

[0033] Connection and limiting components: including transverse connecting plate, connecting bolt, screw, transverse limiting plate, limiting round steel bar and limiting side plate.

[0034] Embodiment 1 of the present invention also discloses an adaptive loading method for a large-scale scaled model test of a long-span arch bridge, comprising the following steps: Step 1: Experiment Preparation Based on the principle of equivalence between scale and stiffness, a scaled-down model specimen was designed and fabricated, with a stress platform and local reinforcement structure set at the preset loading point.

[0035] Install the arch foot internal force testing system and place the cured arch base.

[0036] Step 2: Loading device installation: Install and secure the ground beam system at the test site.

[0037] Install the pulley system, lever system, and slide system in sequence according to the preset loading point position to form a lever-pulley loading unit.

[0038] Thread the loading rope into the pulley system, connect it to the lever system, and install a loading hoist at the loading point.

[0039] Step 3: Test system installation: Displacement sensors and total station targets are installed at the pre-set displacement test section of the model.

[0040] Strain sensors and temperature sensors are installed at a preset strain test section and connected to a data acquisition instrument.

[0041] Establish a measurement coordinate system and perform initial linear measurements.

[0042] Step 4: Preloading and Adjustment

[0043] By using a loading gourd to preload the model multiple times, the gap between the model and the device is eliminated.

[0044] Read the pressure sensor data at each loading point, and adjust the lever adjustment steel plate to change the position of the lever fulcrum, thereby adjusting the load amplification factor of each loading point so that the load ratio at each point reaches the design value.

[0045] Step 5: Formal Loading and Data Collection: The load is applied gradually by loading the hoist until the load at each point reaches the target value.

[0046] After each loading stage, the system is allowed to stand still for a preset time, and displacement, strain, and arch foot internal force data are collected simultaneously to complete one working condition test.

[0047] Repeat the loading process until all design conditions are completed.

[0048] Example 2: Based on the Tian'e Longtan Grand Bridge with a main span of 600m, such as Figure 1 A single-rib scaled-down model was designed using a 1:40 scale based on the principle of stiffness equivalence, such as... Figure 2 The model has a main span of 15m and a rise of 3.125m. The composite section of the actual bridge is equivalent to a reinforced concrete section, and the steel pipes are equivalent to steel bars according to the reinforcement ratio. 60mm diaphragms and local bearing pads are set at the loading points to avoid local damage.

[0049] The design incorporates a lever-pulley loading device, utilizing the consistent tension and self-sliding characteristics of the pulley wire ropes to achieve unconstrained free deformation of the model and synchronous load application during loading. Leveraging the lever's load amplification properties, it meets the requirements for loading large-tonnage dead load counterweights, and the lever amplification factor is adjustable to accommodate inconsistent loads at different loading points. The model requires a load of 39 times its own weight; a distributed concentrated load is used instead of the self-weight distributed load, with loading points spaced 1m apart, totaling 15 loading points across the entire arch.

[0050] To ensure the lateral stability of the single-rib model, two portal frame lateral restraint devices are arranged longitudinally along the arch rib, such as... Figure 3 This limits lateral deformation and prevents lateral instability during loading. It also serves as a safety protection measure against collapse, causing the model's first-order instability mode to change from lateral bending to vertical bending, and increasing the critical load factor to 4.25.

[0051] The testing section mainly consists of displacement testing, strain testing, and arch foot internal force testing. Displacement testing: Seven displacement test sections were set at the 8th point of the arch rib, and vertical displacement was observed using a 5G201 type wire-guided displacement gauge and a Leica MS60 total station. Strain testing: A total of nine strain test sections were set on the entire model, including the 8th point section and the two arch feet, such as... Figure 4 Five strain gauges were set up at each stress test section. W1-W3 were used to collect strain data along the web height, while B1 and R1 were used to collect strain data of the bottom and top slab concrete, respectively. A T1 temperature sensor was also embedded in the arch crown section to eliminate the potential influence of structural temperature on the strain data. To minimize the impact of the sensors on the structure, small, high-precision, and corrosion-resistant fiber optic strain sensors were used at one arch foot and arch crown. SuperHawk3002TX strain gauges were used at the concrete measuring points, and SuperHawk2001T strain gauges were used at the temperature measuring points. Strain gauges were used to collect strain data at the remaining sections. Arch foot internal force testing: as follows... Figure 5The method of separating the arch base is adopted, and the internal forces at the arch foot are calculated based on static equilibrium. H1 and H2 are the resultant forces of the upper and lower rows of pressure sensors for horizontal force testing at the arch base, respectively. F1 and F2 are the resultant forces of the front and rear pressure sensors for vertical force testing at the arch base, respectively. h1, h2, v1, and v2 are the height difference and horizontal distance from the sensor center to the center of the arch axis at the arch foot. The formula for calculating the internal forces at the arch foot is as follows:

[0052] In one specific embodiment, the adaptive loading system for the large-scale scaled model test of a long-span arch bridge, such as... Figure 6 , Figure 7 The system includes a scaled-down model specimen, an unconstrained adaptive loading device, a lateral limiting device, and a testing system. The scaled-down model specimen is designed based on the principle of stiffness equivalence; the unconstrained adaptive loading device consists of a lever-pulley system; and the testing system includes modules for displacement testing, strain testing, and arch foot internal force testing.

[0053] 2. Unconstrained adaptive loading devices, such as Figures 8-12 The components include: 1. Ground beam screw nut; 2. Ground beam I-beam; 3. Ground beam connecting screw nut; 4. Pulley fixing block; 5. Loading slide fixing block; 6. Arch foot loading lever; 7. Arch foot lower pulley; 8. Arch foot upper pulley; 9. General loading lever; 10. General lower pulley; 11. General upper pulley; 12. Loading slide; 13. Arch top force sensor; 14. Arch top loading rope pad; 15. Loading point lever; 16. Fixed loading rope; 17. Loading hoist; 18. Movable loading rope; 19. Lever adjusting steel plate; 20. Pin shaft; 21.

[0054] 3. Lateral limiting device, such as Figures 13-14 It includes a ground-embedded steel plate 22, a bottom steel plate 23, a top steel plate 24, a refined rib plate 25, a longitudinal bridge stiffening plate 26, a transverse bridge stiffening plate 27, a main I-beam steel plate 28, a transverse connecting plate 29, a connecting plate M40 bolt 30, a connecting plate screw 31, a transverse limiting plate 32, a limiting round steel bar 33, a limiting side plate 34, and a limiting plate screw nut 35.

[0055] 4. Testing system, such as Figure 15 It includes eight force sensors 36 behind the arch seat and on the bottom surface of the arch seat, an inner steel pad 37, an outer steel plate 38, and a steel pad fixing screw 39.

[0056] 5. A method and system for adaptive loading of loads in a large-scale scaled model test of a long-span arch bridge according to claims 1-4, comprising the following steps: Step 1: Preparatory work before the formal test, including drawing test installation drawings, designing and drawing model construction drawings based on the scaling ratio and stiffness equivalence principle. Calibrate the displacement and pressure sensors beforehand. Prioritize the fabrication of the arch abutment; after fabrication, install the arch abutment internal force testing system at the test site, such as... Figure 13 Then, place the cured arch base on top. Next, construct the arch rib formwork according to the design lines, and erect load-bearing platforms at 1m intervals at the pre-set loading points of the arch ribs. Pre-install features such as... Figure 4 The fiber optic strain sensor shown is constructed using fine aggregate concrete. A variable cross-section reinforcement section is installed at the arch foot, and diaphragms and local bearing pads are installed at the loading points to ensure that the specimen dimensions and material properties meet the design requirements.

[0057] Step Two: According to the experimental requirements, after the scaled-down arch bridge model is formed, the supports and templates are removed. Multiple I-beams 2 and 3 are installed between the two arch bases, ensuring that the length of the I-beams covers both arch bases. The I-beams are then connected into a whole using ground beam connecting screws and nuts 4. Next, the ground and I-beams are fixed using reaction ground beam bolts 1. Then, lever-pulley loading devices are installed at preset loading points on the model arch ribs at 1m intervals. First, the arch foot sliding pulleys 8 and general sliding pulleys 11 are placed at both ends vertically to the loading points. The arch foot loading lever 7 is placed vertically to the arch foot loading point and presses down on the arch foot sliding pulleys. The general loading lever 10 is placed vertically to other loading points and presses down between the two general sliding pulleys 11, ensuring that the loading points and the lever device are on the same vertical line. Finally, the device is fixed to the ground beam I-beams 2 and 3 using pulley fixing blocks 5 and lever fixing blocks 6. Next, assemble the other devices on the ground, fix the arch pressure sensor 14 to the arch loading rope pad 15, connect the fixed loading rope 17 to the loading lever 7, and then use the pin 21 to install the loading lever 7 into the upper loading slide 6, making the six components a unit. Use a laboratory gantry crane to lift the unit and place it at the loading point. Then install the upper pulley 12, and use the pin 21 to install the lever into the lower loading slide 13, thus completing the device for one loading point. Repeat this operation 15 times. Then, thread the movable loading rope 19 through each pulley. Finally, at the loading point, divide the movable loading line 19 into two parts and install the loading hoist 18.

[0058] Step 3: Installation of the testing system: Install wire displacement gauges and total station measuring point targets at various locations of the 8 points on the model; set up strain gauges and temperature sensors at the 9 stress test sections and connect them to the data acquisition instrument; use the total station to establish a coordinate system at a suitable location and perform the initial measurement of the arch rib shape.

[0059] Step 4: Preloading: Use loading hoist 18 to preload the model multiple times. Multiple preloadings eliminate the gap between the scaled model and the components. After loading, check the test data to ensure that each test value is within the normal working range. At the same time, adjust the loading slide 13 with lever adjustment steel plate 20 according to the pressure value obtained from the test, so that the proportion of each loading lever is different, thereby making the force ratio of each loading point reach the design value.

[0060] Step 5: Formal Loading: Use loading hoist 18 to load the model. During the loading process, pay attention to the pressure sensor readings at each loading point. When the pressure sensor value reaches the required value for the test, stop loading, let the test model stand still for 5 minutes to collect data, and complete the test for one working condition. Then proceed to the next level of loading until all working conditions are completed.

[0061] The beneficial effects that can be achieved through the above technical solution are as follows: 1. Solving the problem of constraint interference: By utilizing the self-sliding characteristics of lever-pulley system, the model can be free to deform without constraints, avoiding the loading system from changing the original failure mode of the structure. The test results show that the maximum deflection difference between the model and the actual bridge is only 0.4mm, accounting for 4.5% of the total deflection of the model, and the stress response is highly consistent.

[0062] 2. Improved loading accuracy and stability: The adjustable multiplier lever device adapts to multi-point non-uniform load requirements, eliminating the need for repeated load adjustments. The load remains stable over a long period, and the model and the actual bridge have a high degree of consistency in axial compressive stress and bending stress distribution, with the maximum deviation all within a reasonable range.

[0063] 3. Saves test space: By utilizing the leverage amplification effect, the amount of counterweight used is greatly reduced. Compared with the traditional multi-point suspension method, it significantly reduces the test space requirements and is suitable for large-tonnage constant load loading scenarios.

[0064] 4. Ensuring test safety: The lateral limiting device increases the critical load factor of the model from 0.75 to 4.25, effectively preventing lateral instability and collapse risks, and providing reliable protection for test safety.

[0065] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0066] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for adaptive loading of loads in a large-scale scaled model test of a long-span arch bridge, characterized in that, Includes the following steps: S1: Based on the target bridge, a scaled-down model specimen is made according to the principle of scale ratio and stiffness equivalence, and loading points are set at the preset positions of the arch ribs. S2: Install a ground beam system at the test site, and install pulley units, lever units and slide systems corresponding to each loading point in sequence to form multiple lever-pulley loading units, thread the loading rope through and connect the loading mechanism; S3: Install displacement sensors, strain sensors, and arch foot internal force testing sensors on the model to establish a data acquisition system; S4: Preload is performed through the loading mechanism to eliminate gaps, and the fulcrum position of the corresponding lever unit is adjusted according to the measured load value at each loading point to make the load ratio at each point meet the design requirements. S5: Perform formal graded loading. After each loading reaches the target value, allow the system to stabilize at rest. Simultaneously collect displacement, strain, and arch foot internal force data until all test conditions are completed.

2. The adaptive loading method for a large-scale scaled model test of a long-span arch bridge according to claim 1, characterized in that, The S2 further includes: installing lateral limiting devices on both sides of the model in the longitudinal direction, wherein a gap is left between the lateral limiting devices and the side of the model arch rib, allowing the model to deform freely in the vertical direction but restricting its lateral displacement beyond a predetermined range.

3. The adaptive loading method for a large-scale scaled model test of a long-span arch bridge according to claim 1, characterized in that, In S4, the lever fulcrum is changed by adding or removing the adjusting steel plate on the lever unit or moving its installation position in the slide, thereby achieving stepless or stepped adjustment of the load amplification factor.

4. The adaptive loading method for a large-scale scaled model test of a long-span arch bridge according to claim 1, characterized in that, The loading mechanism is a manual or electric hoist, which applies the load by pulling the loading rope.

5. The adaptive loading method for a large-scale scaled model test of a long-span arch bridge according to claim 1, characterized in that, The scaling ratio is between 1:20 and 1:

60.

6. A load-adaptive loading system for a large-scale scaled model test of a long-span arch bridge, characterized in that, The method according to any one of claims 1-5 includes: Scaled-down model specimens are used to create scaled-down model specimens based on the target bridge, according to the principle of scaled-down ratio and stiffness equivalence, with loading points set at preset positions on the arch ribs. An unconstrained adaptive loading device, consisting of a lever-pulley system, is used to apply loads to the loading points and allow the model to deform freely without constraints during the loading process. A lateral limiting device is arranged on both sides of the longitudinal direction of the scaled-down model specimen to limit the lateral displacement of the model and prevent instability. The testing system is used to collect data on the displacement, strain, and internal forces at the arch feet of the model during the test.

7. The adaptive loading system for a large-scale scaled model test of a long-span arch bridge according to claim 6, characterized in that, The unconstrained adaptive loading device includes: The ground beam system, fixed to the test site, serves as the foundation for device installation; Multiple pulley units are fixed to the ground beam system and are set corresponding to each loading point; Multiple lever units, each lever unit being movably mounted via a pin and associated with a corresponding pulley unit and a loading point; A slide system is used to install and allow adjustment of the position of the lever unit; The loading rope passes sequentially through the pulley unit and the lever unit to form a load transfer path; A loading mechanism, connected to the loading rope, is used to provide and control the loading force.

8. The adaptive loading system for a large-scale scaled model test of a long-span arch bridge according to claim 7, characterized in that, The fulcrum position of the lever unit is adjustable. By changing the fulcrum position, the load amplification factor of the lever unit can be adjusted, thereby adapting to the non-uniform load requirements of different loading points.

9. The adaptive loading system for a large-scale scaled model test of a long-span arch bridge according to claim 6, characterized in that, The lateral limiting device is a portal frame structure, including a vertically arranged main support, a lateral connecting member, and an adjustable lateral limiting component. The lateral limiting component maintains a preset gap with the side of the model arch rib.

10. The adaptive loading system for a large-scale scaled model test of a long-span arch bridge according to claim 6, characterized in that, The testing system includes: The displacement testing module uses a wire displacement gauge and / or a total station, and is set up at multiple displacement testing sections of the model arch rib. The strain testing module uses fiber optic strain sensors and / or resistance strain gauges, which are arranged on multiple strain testing sections of the model arch rib. The arch foot internal force testing module adopts a split arch seat structure, with multiple pressure sensors arranged on the back and bottom of the arch seat, and calculates the arch foot internal force through static balance.

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