Quasi-zero stiffness self-adapting support creep test device and design method

Abstract

The application provides a quasi-zero stiffness self-adaptive support creep testing device and a design method. The device comprises a plurality of columns arranged around a base, a quasi-zero stiffness system arranged at a middle position of the base, a jacking device placed above the quasi-zero stiffness system, a lower pressing plate arranged above the jacking device, an upper pressing plate arranged above the lower pressing plate, and a support test piece placed between the upper and lower pressing plates. The quasi-zero stiffness system comprises a limiting column with a bottom plate, a disc spring group sleeved on the limiting column, a disc spring cover arranged on the disc spring group, a sleeve arranged outside the disc spring cover, a carrier plate fixedly connected to the sleeve, and a jacking device installed on the carrier plate. Four variable-pitch stepped stiffness springs are horizontally and symmetrically arranged around the carrier plate, and the two ends of each variable-pitch stepped stiffness spring are hingedly connected to the carrier plate and a vertical rod with a bottom plate. The application is used for realizing long-term, stable and high-precision automatic load holding testing and realizing self-adaptive load holding and displacement compensation design.

Description

Technical Field

[0001] This invention belongs to the field of structural engineering testing technology and intelligent monitoring, and specifically relates to a quasi-zero stiffness adaptive bearing creep testing device, which is suitable for evaluating the long-term creep performance of rubber seismic isolation bearings in buildings, bridges and other structures. Background Technology

[0002] Seismic isolation technology is a crucial means of reducing structural damage to buildings and bridges under strong earthquakes. Rubber seismic isolation bearings are the most widely used isolation devices. Their core principle is to isolate the transmission of seismic energy through the low horizontal stiffness of the rubber bearing, while simultaneously providing significant vertical bearing capacity through the constraint of the rubber. Their effectiveness has been verified in numerous strong earthquakes over the past decade. Test equipment for creep performance testing of seismic isolation rubber bearings (creep refers to the compressive deformation of a bearing under a fixed load over a long period) requires a load measurement time of no less than 1000 hours according to the standard GB / T20688.1-2007. This places extremely high demands on the long-term load holding capacity of the test equipment. Existing seismic isolation bearing creep test equipment mainly relies on hydraulic jacks or screw jacks to achieve load holding. Hydraulic systems require continuous power supply and active control, resulting in high energy consumption and cost; backup power supplies are also expensive to prevent power outages. Screw jacks, on the other hand, rely on manual intervention due to the decrease in vertical load after the bearing's creep contraction, making long-term automatic load compensation impossible and affecting the accuracy and reliability of creep data. Therefore, there is an urgent need for an intelligent creep test device that can automatically maintain a constant load and has the ability to adaptively compensate for displacement. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems of load attenuation, reliance on manual intervention, high energy consumption, and high cost of backup power in the prior art, and to propose a quasi-zero stiffness adaptive support creep testing device and design method to achieve long-term, stable, and high-precision automatic load holding test.

[0004] The above objectives are achieved through the following technical solutions:

[0005] This invention first provides a quasi-zero stiffness adaptive support creep testing device, comprising several columns arranged around a base, a quasi-zero stiffness system arranged in the middle of the base, a pushing device placed above the quasi-zero stiffness system, a lower pressure plate arranged above the pushing device, an upper pressure plate arranged above the lower pressure plate, and a test specimen placed between the upper and lower pressure plates; a pressure sensor is arranged between the pushing device and the lower pressure plate to form a force transmission path centered on the pushing device-pressure sensor-lower pressure plate, and an electronic dial indicator is arranged between the upper and lower pressure plates; the pressure sensor is connected to a magnetic digital display, and the electronic dial indicator is connected to a data acquisition system.

[0006] The quasi-zero stiffness system includes a limiting post with a base plate, on which a disc spring assembly is mounted. The disc spring assembly is provided with a disc spring cover, and a sleeve is provided outside the disc spring cover. A carrying plate is fixedly connected to the sleeve, and the pushing device is installed on the carrying plate. Four variable pitch stepped stiffness springs and their adjustment systems are symmetrically arranged around the carrying plate. Each variable pitch stepped stiffness spring adjustment system includes a perforated sleeve, a tightening bolt and nut, a shear bar mechanism, a sleeve, a ring force gauge, a variable pitch spring, and a displacement baffle. The two ends of the variable pitch stepped stiffness spring are respectively hinged to the carrying plate and a vertical post with a base plate.

[0007] Furthermore, there are four columns, which pass through the four corners of the upper and lower pressure plates respectively; the upper pressure plate is fitted onto the column through round holes of corresponding sizes set at the corners, while the lower pressure plate is supported on the column by the movement of a circular guide rail; the column has a variable cross-section design, divided into three sections from top to bottom: section I, section II, and section III, with the diameter of section I, section II, and section III increasing sequentially. The upper pressure plate is fitted onto section I, and the lower pressure plate is fitted onto section II. The part of the column above the upper pressure plate has a locking device, and the part of the column below the lower pressure plate has a supporting movement device.

[0008] Furthermore, the supporting moving device is a circular guide rail.

[0009] Furthermore, the locking device is a bolt, and the surface of the column above the upper pressure plate is engraved with threads that mate with the bolt.

[0010] Furthermore, the jacking device is a screw jack.

[0011] This invention also provides an adaptive load-bearing and displacement compensation design method for the aforementioned quasi-zero stiffness adaptive support creep testing device based on the potential energy method. This method uses the potential energy method to match the negative stiffness of the variable pitch stepped stiffness spring with the positive stiffness of the disc spring assembly, achieving zero total system stiffness, thereby ensuring accurate implementation of adaptive load-bearing and displacement compensation. The specific method is as follows:

[0012] Adaptive quasi-zero stiffness design of quasi-zero stiffness system, total system potential energy It consists of the elastic potential energy of four variable pitch stepped stiffness springs and the potential energy of a disc spring assembly, with the disc spring assembly pre-compressed. The compression of a variable pitch stepped stiffness spring is That is, the spring is compressed at the equilibrium position. Then we have: (1) In the formula and This represents the horizontal and vertical distance between the locking holes of the two variable-pitch stepped stiffness springs when they are in equilibrium. The length representing the equilibrium state of a variable pitch stepped stiffness spring;

[0013] When the load plate moves upward displacement hour, Variable pitch stepped stiffness spring length for: (2)

[0014] Total compression of variable pitch stepped stiffness springs for: (3)

[0015] The force-displacement relationship of a variable pitch stepped stiffness spring exhibits nonlinear characteristics; therefore, a polynomial model is used here. (4) In the formula, , and These represent the forces acting on the variable pitch stepped stiffness springs. Linear stiffness coefficient and nonlinear cubic stiffness coefficient; (5) In the formula, This represents the stiffness of the disc spring assembly;

[0016] right Differentiate: (6) in, , , The vertical force provided for the quasi-zero stiffness system;

[0017] right Then differentiate: (7) in, The angle between the spring and the horizontal plane when the platform moves upward. , The total stiffness of the quasi-zero stiffness system;

[0018] Quasi-zero stiffness requirement at the equilibrium point At this point, the total stiffness of the system is zero, which means we obtain (8) in, The angle between the spring and the horizontal plane at the equilibrium position. ;

[0019] according to By selecting a suitable disc spring assembly, the negative stiffness of the variable pitch stepped stiffness spring (10) can be matched with the positive stiffness of the disc spring assembly (14).

[0020] The present invention also provides a method for conducting creep testing using a quasi-zero stiffness adaptive support creep testing device, characterized in that the method includes the following steps:

[0021] Step 1: First, the core test specimen, the rubber support, is installed between the upper and lower pressure plates. The upper pressure plate is fastened to section I of the column with bolts to form a stable loading frame; the lower pressure plate is moved and supported on the column via a circular guide rail.

[0022] Step 2: After the specimen is installed in place, preload is applied using a screw jack to eliminate the initial gap between components and ensure full contact of the rubber supports. Then, the electronic dial gauge and pressure sensor used to measure the compression deformation of the rubber supports are zeroed.

[0023] Step 3: Add standard loading weights or weights to the specified weight above the upper pressure plate. Based on the pressure value fed back by the pressure sensor, pressurize the jacking device to achieve the pressure required for the creep test.

[0024] Step 4: Throughout the creep process, the magnetic digital display automatically and continuously records the load data from the pressure sensor, and the data acquisition system automatically and continuously records the deformation data from the electronic dial indicator.

[0025] The advantages of this invention compared to the prior art are:

[0026] 1. The quasi-zero stiffness adaptive load-bearing system designed in this invention: Through the parallel stiffness coupling design of the variable pitch stepped stiffness spring (10) and the disc spring assembly (14), the equivalent stiffness of the system approaches zero near the equilibrium position, thus constructing a quasi-zero stiffness system with displacement adaptive compensation capability. This system can automatically respond to displacement changes caused by creep of the specimen, compensate for load attenuation in real time, and achieve a long-term, stable self-sustaining test state, reflecting the technological breakthrough of traditional creep devices from linear compensation to quasi-zero stiffness system compensation.

[0027] 2. This invention designs a high-precision guiding and anti-eccentric load bearing system: It adopts an integrated guiding structure of a variable cross-section column (with base) 1 and a circular guide rail 7 to achieve precise alignment of the upper and lower pressure plates 3 and 4 and the high-centered transfer of axial loads. This design not only provides an adjustable test space but also significantly enhances the rigidity and anti-eccentric load capacity of the overall structure, providing a stable and reliable mechanical support environment for long-term creep tests.

[0028] 3. This invention embodies the force (stiffness) adjustable function of the variable pitch stepped stiffness spring. The force adjustable function can be used for on-site calibration and compensation to ensure that the system reaches a true near-zero stiffness state at the equilibrium point, thereby obtaining better load holding capacity.

[0029] 4. The potential energy analysis method innovatively introduced in this invention replaces the traditional force balance method, which establishes a better theoretical model for this nonlinear system and derives a specific design formula to achieve quasi-zero stiffness, thereby realizing the long-term adaptive load holding of the device. Attached Figure Description

[0030] Figure 1 This is a three-dimensional structural diagram of a quasi-zero stiffness adaptive support creep testing device according to the present invention.

[0031] Figure 2 This is a two-dimensional structural schematic diagram of a quasi-zero stiffness adaptive support creep testing device (with intelligent detection system) according to the present invention.

[0032] Figure 3 This is a three-dimensional structural diagram of the quasi-zero stiffness system in a quasi-zero stiffness adaptive support creep testing device of the present invention.

[0033] Figure 4 This is a three-dimensional structural diagram (with base plate) of the limiting column in a quasi-zero stiffness adaptive support creep testing device of the present invention.

[0034] Figure 5 This is a three-dimensional structural diagram of a variable cross-section upright (with base) in a quasi-zero stiffness adaptive support creep testing device of the present invention.

[0035] Figure 6 This is a schematic diagram of the three-dimensional structure of the circular guide rail in a quasi-zero stiffness adaptive support creep testing device of the present invention.

[0036] Figure 7 This invention relates to a quasi-zero stiffness adaptive support creep testing device in which the load plate... A simplified diagram illustrating the recompression of the variable pitch stepped stiffness spring during the process;

[0037] Figure 8 This is an exploded schematic diagram of the design structure of the variable pitch stepped stiffness spring in the quasi-zero stiffness adaptive support creep testing device of the present invention.

[0038] Figure 9 This is a schematic diagram of the components related to the design structure of the variable pitch stepped stiffness spring in a quasi-zero stiffness adaptive support creep testing device of the present invention (Figure a. Detailed view of the displacement device pushing the spring and Figure b. Detailed view of the force measuring device after pushing the spring);

[0039] Figure 10 This is a schematic diagram of the overall force distribution of the quasi-zero stiffness system in a quasi-zero stiffness adaptive support creep testing device of the present invention.

[0040] Figure 11 This invention relates to a quasi-zero stiffness adaptive support creep testing device, which demonstrates the overall vertical force of a quasi-zero stiffness system under different loads during creep testing. Displacement of the load plate A schematic diagram;

[0041] Figure 12 This invention relates to a quasi-zero stiffness adaptive support creep testing device for stiffness in a quasi-zero stiffness system. Displacement of the load plate A schematic diagram (based on an example);

[0042] Figure 13 This invention relates to a quasi-zero stiffness adaptive support creep testing device, which involves changing the design parameters of a variable pitch stepped stiffness spring. Then it moves up and down with the load plate. And regulating force A schematic diagram (based on an example); Detailed Implementation

[0043] like Figure 1 , Figure 2As shown, this invention provides a quasi-zero stiffness adaptive support creep testing device, including a column 1 (with base), bolts 2, upper pressure plate 3, lower pressure plate 4, rubber support 5, electronic dial indicator 6, circular guide rail 7, pressure sensor 8, screw jack 9, quasi-zero stiffness mechanism, variable pitch stepped stiffness spring 10 (with perforated sleeve 10-1, tightening bolt and nut 10-2, shear bar mechanism 10-3, sleeve 10-4, ring force gauge 10-5, variable pitch spring 10-6 and displacement baffle 10-7), load plate 11, disc spring cover 12, limiting column (with base plate) 13 and disc spring assembly 14, column ( 15 (with base plate), 16 data acquisition system and 17 magnetic digital display; there are multiple columns; the column 1 has a variable cross-section design, divided into zone I, zone II and zone III from top to bottom, with the diameter of the column 1 in zone I, zone II and zone III increasing sequentially; the upper pressure plate 3 is fitted in zone I, and the lower pressure plate 4 is fitted in zone II; the part of the column 1 above the upper pressure plate 3 has a locking device, and the part of the column 1 below the lower pressure plate 4 has a supporting moving device; a pushing device and a pressure sensor 8 are placed between the quasi-zero stiffness mechanism and the lower pressure plate, the bottom of the pushing device is installed on the load plate 11 of the quasi-zero stiffness mechanism, and the upper end of the pressure sensor 8 abuts against the lower end face of the lower pressure plate 4. The variable pitch stepped stiffness spring 10 of the quasi-zero stiffness mechanism is rigidly connected to the upright through the load plates at both ends, and is arranged symmetrically and obliquely around the perimeter; the lower end of the load plate 11 is connected to the disc spring cover 12, and the disc spring cover 12 supports the disc spring assembly 14; the disc spring assembly 14 is composed of multiple disc springs connected in series on the same axis and then stacked in parallel, and is fitted onto the limiting post 13 of the base for limiting.

[0044] The number of columns is [number], which are respectively arranged at the corners of the upper pressure plate 3 and the lower pressure plate 4.

[0045] The upper pressure plate 3 is fitted onto the column 1 through round holes of corresponding sizes set at the corners, while the lower pressure plate 4 is placed on the column 1 by the movable support of the circular guide rail 7.

[0046] The jacking device is a screw jack 9.

[0047] The supporting moving device is a circular guide rail 7.

[0048] The locking device is a bolt 2, and the surface of the column 1 above the upper pressure plate 3 is engraved with threads that cooperate with the bolt 2.

[0049] The force adjustment function of the variable pitch stepped stiffness spring is achieved through its built-in precision mechanical mechanism. Specifically, the tightening bolt and nut 10-2 acts as the adjustment actuator. The threaded pair formed by the bolt and nut generates a precise linear displacement during rotation, driving the uppermost perforated sleeve 10-1 to move towards the center. This displacement further pushes the shear bar mechanism 10-3 connected to it, causing it to move forward and press against the displacement baffle 10-7. The movement of the displacement baffle 10-7 directly changes the initial installation position or pre-compression of the variable pitch spring 10-6, thereby achieving stepless and precise adjustment of the spring's output force. To monitor in real time and ensure adjustment accuracy, the ring-shaped force gauge 10-5 is in close contact with the spring surface, providing real-time feedback on force changes, forming a control system of "mechanical drive - displacement conversion - pre-compression adjustment - real-time monitoring".

[0050] Installation method:

[0051] The variable cross-section column (with base) 1 is precisely positioned on the horizontal platform to ensure overall stability. Then, a vertical rod 15 is installed on top, providing lateral restraint and restoring force for the variable pitch stepped stiffness spring 10. A limiting post (with base plate) 13 is placed at the center of the plane of the vertical rod (with base) 15, its core function being to provide precise vertical guidance for subsequent moving parts. Next, the disc spring assembly 14 is fitted onto the limiting post (with base plate) 13, and the disc spring cover 12 is placed on top. Then, the carrying plate 11 is installed, thus constraining the disc spring assembly between the carrying plate and the disc spring cover to form a single moving unit. Afterward, the other end of the variable pitch stepped stiffness spring 10 is connected to the side of the carrying plate 11 via a snap-fit ​​to balance part of the load or provide unloading restoring force. The lower pressure plate 4 is guided by the smooth guide rail 7, moved along the variable cross-section column 1, and precisely positioned at the junction of its variable cross-sections, forming a precisely guideable load-bearing surface. Install the pressure sensor 8 at the force center of the lower pressure plate 4, ensuring the contact surface is free of impurities to guarantee accurate force measurement. Then, place the screw jack 9 on the lower support plate 11 and adjust its lifting head so that it is directly below the center of the pressure sensor 8, thus forming a clear and centered force transmission path of "jack → pressure sensor → lower pressure plate". Place the rubber support 5 directly above the lower pressure plate 4, and finally, fit the upper pressure plate 3 onto the top of the column, and use bolts 2 to fasten the upper pressure plate 3, lower pressure plate 4, and variable cross-section column 1 into a high-rigidity integral load-bearing frame. Securely fix the electronic micrometer 6 with a special bracket and adjust its position so that the probe lightly touches a flat measuring point between the upper and lower pressure plates (3 and 4). Connect the signal output terminals of the electronic micrometer 6 and the pressure sensor 8 to the data acquisition system 16 and the magnetic digital display 17 respectively through special acquisition lines.

[0052] The above-mentioned design method for a quasi-zero stiffness adaptive support creep testing device achieves zero total system stiffness at the equilibrium point by matching the negative stiffness of the variable pitch stepped stiffness spring 10 with the positive stiffness of the disc spring assembly 14, thereby ensuring the accurate realization of adaptive load holding and displacement compensation. The specific method is as follows:

[0053] Adaptive quasi-zero stiffness design of quasi-zero stiffness system, total system potential energy It consists of the elastic potential energy of four variable pitch stepped stiffness springs and the potential energy of a disc spring assembly, with the disc spring assembly pre-compressed. The compression of a variable pitch stepped stiffness spring is That is, the spring is compressed at the equilibrium position. Then we have: (1) In the formula and This represents the horizontal and vertical distance between the locking holes of the two variable-pitch stepped stiffness springs when they are in equilibrium. The length representing the equilibrium state of a variable pitch stepped stiffness spring;

[0054] When the load plate moves upward displacement hour, Variable pitch stepped stiffness spring length for: (2)

[0055] Total compression of variable pitch stepped stiffness springs for: (3)

[0056] The force-displacement relationship of a variable pitch stepped stiffness spring exhibits nonlinear characteristics; therefore, a polynomial model is used here. (4) In the formula, , and These represent the forces acting on the variable pitch stepped stiffness springs. Linear stiffness coefficient and nonlinear cubic stiffness coefficient; (5) In the formula, This represents the stiffness of the disc spring assembly;

[0057] right Differentiate: (6) in, , , The vertical force provided for the quasi-zero stiffness system;

[0058] right Then differentiate: (7) Among them, The angle between the spring and the horizontal plane when the platform moves upward. , The total stiffness of the quasi-zero stiffness system;

[0059] Quasi-zero stiffness requirement at the equilibrium point At this point, the total stiffness of the system is zero, which means we obtain

[0060] (8)

[0061] in, The angle between the spring and the horizontal plane at the equilibrium position. ;

[0062] according to By selecting a suitable disc spring assembly, the negative stiffness of the variable pitch stepped stiffness spring (10) can be matched with the positive stiffness of the disc spring assembly (14).

[0063] Application examples.

[0064] Based on the design surface pressure of the rubber seismic isolation bearing under test (6-12 MPa) and its bearing area (The creep support specified in GB 20688-1 can be replaced by a scaled-down version, which is 200-300 mm). Calculate the maximum constant load that needs to be applied for the creep test. The maximum constant load range to be applied during the creep test is (188.5 kN-848.2 kN), with a design load of 400 kN.

[0065] Based on three-dimensional illustration ( Figure 3 Based on theoretical optimization, the system adopts a symmetrical arrangement, with the horizontal distance of the variable pitch stepped stiffness springs... Set to 120 mm, vertical height Also 50 mm, .

[0066] The negative stiffness design of variable pitch stepped stiffness springs is a critical aspect. In actual selection, four standard heavy-duty springs are chosen and arranged symmetrically: the material is 60Si2MnA spring steel, and the stiffness is... , The total compression of a variable pitch stepped stiffness spring is... (That is, the spring is compressed at the equilibrium position) )

[0067] The positive stiffness matching of the disc spring assembly must meet the quasi-zero stiffness condition: , Disc spring assembly pre-compression .

[0068] For the disc spring assembly, there are 3 series and 4 parallel configurations. The stiffness of a single disc spring is denoted as... (unit: )

[0069] Stiffness of each group of 3 plates connected in series: (9)

[0070] Total stiffness of the two sets connected in parallel: (10).

[0071] For matching A single disc spring is required. .

[0072] According to the calculation formula for a single disc spring: (11) Typical parameters (spring steel): Elastic modulus E = 206000 N / mm² 2 Poisson's ratio u=0.3, outer diameter D=250 mm, inner diameter d=127 mm, thickness t=15.87 mm, parameters K1=0.69, K4=1 (no support surface), deformation parameters h0=9 mm, f=6.72 mm.

[0073] The creep of the support is typically 5% (approximately 1 mm) of the support adhesive layer thickness. This is achieved through the overall vertical force of the quasi-zero stiffness system. Displacement of the load plate Relationship curve ( Figure 11 It can be seen that under creep load , The displacement variation is extremely small, and the pressure fluctuation is within ±2% of the specification GB / T 20688.1-2007, indicating that the system possesses excellent dead load holding capacity. Meanwhile, the overall system stiffness... Displacement of the load plate Relationship curve ( Figure 12 )visible, The fluctuation value near the equilibrium position is related to the stiffness of the disc spring assembly. Compared to the negligible stiffness, this further verifies the realization of quasi-zero stiffness characteristics. In summary, this device can effectively maintain a constant load within the support creep displacement range, demonstrating that the quasi-zero stiffness design is reasonable and feasible.

[0074] The test method for the aforementioned quasi-zero stiffness adaptive support creep testing device includes the following steps:

[0075] Step 1: Install the rubber support 5 of the specimen between the upper and lower pressure plates 3 and 4. The upper pressure plate 3 is fastened to the variable cross-section column 1 (main support structure) with bolts 2 to form a stable loading frame. To ensure the centering of the axial loading, the lower pressure plate 4 is equipped with a circular guide rail 7 to guide the loading direction. After the specimen is installed in place, pre-loading is performed using a screw jack to eliminate the initial gap between components and ensure full contact between the supports. Subsequently, the electronic dial gauge and pressure sensor used to measure the compression deformation of the supports are zeroed.

[0076] Step 2: After the specimen is installed in place, preload is applied using the screw jack 9 to eliminate the initial gap between components and make the rubber support 5 fully contact. Then, the electronic dial gauge 6 and pressure sensor 8 used to measure the compression deformation of the rubber support 5 are zeroed.

[0077] Step 3: Add standard loading weights or weights to the specified weight above the upper pressure plate 3. Based on the pressure value fed back by the pressure sensor 8, pressurize the pushing device to achieve the pressure required for the creep test.

[0078] Step 4: Throughout the creep process, the magnetic digital display 17 automatically and continuously records the load data from the pressure sensor 8 and the data acquisition system 16 automatically and continuously records the deformation data from the electronic dial gauge 6.

[0079] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the invention in any way. Any person skilled in the art can make various modifications and refinements without departing from the principles of the present invention, and all such modifications and refinements fall within the scope of protection of this patent.

Claims

1. A quasi-zero stiffness adaptive support creep testing device, characterized in that, The system includes several columns (1) arranged around the base, a quasi-zero stiffness system in the middle of the base, a jacking device (9) placed above the quasi-zero stiffness system, a lower pressure plate (4) above the jacking device (9), an upper pressure plate (3) above the lower pressure plate (4), and a support specimen placed between the upper pressure plate (3) and the lower pressure plate (4); a pressure sensor (8) is arranged between the jacking device (9) and the lower pressure plate (4) to form a force transmission path centered on the jacking device (9) - pressure sensor (8) - lower pressure plate (4); an electronic dial indicator (6) is arranged between the upper pressure plate (3) and the lower pressure plate (4); the pressure sensor (8) is connected to a magnetic digital display (17); and the electronic dial indicator (6) is connected to a data acquisition system (16). The quasi-zero stiffness system includes a limiting post (13) with a base plate, on which a disc spring assembly (14) is mounted. A disc spring cover (12) is provided on the disc spring assembly (14). A sleeve is provided outside the disc spring cover (12). A carrying plate (11) is fixedly connected to the sleeve. The pushing device (9) is installed on the carrying plate (11). Four variable pitch step stiffness springs (10) are symmetrically arranged around the carrying plate (11). Each variable pitch step stiffness spring (10) includes a perforated sleeve (10-1), a tightening bolt and nut (10-2), a shear bar mechanism (10-3), a sleeve (10-4), a ring force gauge (10-5), a variable pitch spring (10-6), and a displacement baffle (10-7). The two ends of the variable pitch step stiffness spring (10) are respectively hinged to the carrying plate and a vertical rod (15) with a base plate.

2. The quasi-zero stiffness adaptive support creep testing device according to claim 1, characterized in that, The number of columns is four, which pass through the four corners of the upper pressure plate (3) and the lower pressure plate (4); the upper pressure plate (3) is fitted onto the column (1) through round holes of corresponding size set at the corners, while the lower pressure plate (4) is placed on the column (1) through the movable support of the circular guide rail (7); the column (1) is a variable cross section design, divided into area I, area II and area III from top to bottom (Figure 5), and the diameter of area I, area II and area III of the column (1) increases sequentially. The upper pressure plate (3) is fitted onto area I, and the lower pressure plate (4) is fitted onto area II. The part of the column (1) above the upper pressure plate (3) has a locking device, and the part of the column (1) below the lower pressure plate (4) has a supporting moving device.

3. The quasi-zero stiffness adaptive support creep testing device according to claim 2, characterized in that, The supporting moving device is a circular guide rail (7).

4. A quasi-zero stiffness adaptive support creep testing device according to claim 2 or 3, characterized in that, The locking device is a bolt (2), and the column (1) has threads engraved on the surface above the upper pressure plate (3) to match the bolt (2).

5. A quasi-zero stiffness adaptive support creep testing device according to claim 1, 2, 3, or 4, characterized in that, The jacking device is a spiral jack (9).

6. A design method for adaptive load holding and displacement compensation of a quasi-zero stiffness adaptive support creep testing device as described in any one of claims 1-5, characterized in that, This method is based on the potential energy method. By matching the negative stiffness of the variable pitch stepped stiffness spring (10) with the positive stiffness of the disc spring assembly (14), the total stiffness of the system is zero at the equilibrium point, thereby ensuring the accurate realization of adaptive load holding and displacement compensation. The specific method is as follows: Adaptive quasi-zero stiffness design of quasi-zero stiffness system, total system potential energy It consists of the elastic potential energy of four variable pitch stepped stiffness springs and the potential energy of a disc spring assembly, with the disc spring assembly pre-compressed. The compression of a variable pitch stepped stiffness spring is That is, the spring is compressed at the equilibrium position. Then we have: (1) In the formula and This represents the horizontal and vertical distance between the locking holes of the two variable-pitch stepped stiffness springs when they are in equilibrium. The length representing the equilibrium state of a variable pitch stepped stiffness spring; When the load plate moves upward displacement hour, Variable pitch stepped stiffness spring length for: (2) Total compression of variable pitch stepped stiffness springs for: (3) The force-displacement relationship of a variable pitch stepped stiffness spring exhibits nonlinear characteristics; therefore, a polynomial model is used here. (4) In the formula, , and These represent the forces acting on the variable pitch stepped stiffness springs. Linear stiffness coefficient and nonlinear cubic stiffness coefficient; (5) In the formula, This represents the stiffness of the disc spring assembly; right Differentiate: (6) in, , , The vertical force provided for the quasi-zero stiffness system; right Then differentiate: (7) in, The angle between the spring and the horizontal plane when the platform moves upward. , The total stiffness of the quasi-zero stiffness system; Quasi-zero stiffness requirement at the equilibrium point At this point, the total stiffness of the system is zero, which yields... (8) in, The angle between the spring and the horizontal plane at the equilibrium position. ; according to By selecting a suitable disc spring assembly, the negative stiffness of the variable pitch stepped stiffness spring (10) can be matched with the positive stiffness of the disc spring assembly (14).

7. A method for conducting creep testing using the quasi-zero stiffness adaptive support creep testing device as described in any one of claims 1-5, characterized in that, The method includes the following steps: Step 1: First, the core test specimen rubber support (5) is installed between the upper pressure plate (3) and the lower pressure plate (4). The upper pressure plate (3) is fastened to the I zone of the column (1) by bolts (2) to form a stable loading frame. The lower pressure plate (4) is moved and supported on the column (1) by circular guide rail (7). Step 2: After the specimen is installed in place, preload is applied by using a screw jack (9) to eliminate the initial gap between components and make the rubber support (5) fully contact. Then, the electronic dial gauge (6) and pressure sensor (8) used to measure the compression deformation of the rubber support (5) are zeroed. Step 3: Add standard loading weights or weights to the specified weight above the upper pressure plate (3), and pressurize the pusher device to achieve the pressure required for the creep test based on the pressure value fed back by the pressure sensor (8); Step 4: Throughout the creep process, the magnetic digital display (17) automatically and continuously records the load data from the pressure sensor (8) and the data acquisition system (16) automatically and continuously records the deformation data from the electronic dial gauge (6).

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