A stability test device for a bridge support

Abstract

The application discloses a kind of stability test equipment of bridge support, test equipment field, including rack, vertical loading system and composite test system, vertical loading system is located on the upper portion of rack, four rectangular distribution independent loading mechanism and load application mechanism are included, asymmetric vertical pressure and inclined moment can be applied;Composite test system is located in the lower portion of rack, including slide rail, pedestal, rotary table and two driving elements, the pedestal can be driven to slide transversely to realize shear loading, the rotary table can be driven to rotate to realize bottom torsional loading.Load application mechanism includes push plate and integrated multi-dimensional force ball hinge sensor, additional bending moment can be released and multiple force parameters can be measured in real time, and various loading modes can be automatically controlled by matching control system.The equipment solves the problems of single loading, large interference and low efficiency of traditional equipment, truly simulates the complex stress of support, improves the test accuracy and efficiency, and is suitable for stability detection of various bridge supports.

Description

Technical Field

[0001] This invention relates to the field of testing equipment, and more specifically to a stability testing device for bridge bearings. Background Technology

[0002] Bridge bearings are force-transmitting components that connect the superstructure and substructure of a bridge, and their stability directly determines the safe operation of the entire bridge. With the rapid development of long-span bridges and high-speed railway bridges in my country, the stress state of bridge bearings has become increasingly complex. They not only need to withstand vertical loads, but also multiple coupled effects such as eccentric loads from vehicles, horizontal displacement caused by temperature deformation, and torsion of piers and abutments caused by uneven settlement of the roadbed.

[0003] Existing bridge bearing testing equipment has the following main drawbacks: Most equipment uses a single loading head for centrally symmetrical vertical loading, which cannot simulate the asymmetric vertical forces and tilting moments caused by eccentric loads and bending deformations of beams commonly found in actual engineering projects, resulting in significant deviations between test results and actual stress states; vertical, horizontal, and torsional loading systems share the same rigid frame, and forces in each direction are transmitted to each other during loading, generating additional bending moments and force chain distortions, which seriously affect the accuracy of test data; vertical, shear, and torsional tests usually require changing fixtures or being performed on different equipment, which increases the cumulative error introduced by multiple clamping, and the test cycle is long and costly.

[0004] Therefore, developing a stability testing device that can realistically simulate the complex stress conditions of bridge bearings and has high testing efficiency is of great engineering significance. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, this application provides a stability testing device for bridge bearings.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: a stability testing device for bridge bearings, comprising: a frame; a vertical loading system disposed on the upper part of the frame, the vertical loading system comprising four loading mechanisms distributed in a rectangular shape and a loading mechanism for transmitting the pressure output by the loading mechanisms to the bridge bearing to be tested;

[0007] A composite testing system is installed at the lower part of the frame. The composite testing system includes a slide rail, a base, a rotary table, a first driving element, and a second driving element. The slide rail is fixed to the frame laterally, and the base is slidably connected to the slide rail. The rotary table is rotatably connected to the top surface of the base, and the bottom surface of the bridge bearing to be tested is installed on the top surface of the rotary table, and its top surface is fixedly connected to the loading mechanism.

[0008] The first driving element is connected between the frame and the base, and is used to drive the base to slide laterally along the slide rail;

[0009] The second driving element is connected between the base and the rotary table, and is used to drive the rotary table to rotate about the vertical axis relative to the base.

[0010] Furthermore, the loading mechanism includes a push plate and four ball joints. The output end of each loading mechanism is connected to the corresponding corner of the push plate through one of the ball joints. The geometric center of the rectangle formed by the center line of the four loading mechanisms is on the same vertical line as the geometric center of the push plate and the geometric center of the bridge support to be tested. The four loading mechanisms independently control the output force to collaboratively apply an arbitrary mode of asymmetric vertical pressure and tilting moment to the push plate, and release additional bending moment through the ball joints.

[0011] Furthermore, the loading mechanism is a hydraulic cylinder, which is installed on the top crossbeam of the frame, and the piston rod end of the hydraulic cylinder is fixedly connected to the upper end of the ball joint.

[0012] Furthermore, the ball joint is an integrated multi-dimensional force ball joint sensor, including a ball head, a ball seat, and a strain measurement unit; the strain measurement unit is disposed in the equatorial plane of the ball head or in the concave surface of the ball seat, and is used to simultaneously measure the vertical force, horizontal shear force, and additional bending moment acting on the ball joint.

[0013] Furthermore, the push plate is provided with positioning holes that match the mounting holes on the top surface of the bridge bearing to be tested, and the push plate and the bridge bearing are fixedly connected by bolts.

[0014] Furthermore, there are two slide rails, which are arranged parallel and symmetrically on the frame. The distance between the two slide rails is adapted to the size of the base. The frame is provided with a ranging element that is aligned with the base.

[0015] Furthermore, the first driving element is a servo hydraulic cylinder, the cylinder body end of which is hinged to the frame via a first hinge seat, and the piston rod end of which is hinged to the center of the side of the base via a second hinge seat; the servo hydraulic cylinder is equipped with pressure sensors, which are used to detect lateral shear displacement and shear force in real time.

[0016] Furthermore, the rotating platform is provided with a positioning groove adapted to the bridge support to be tested, and screws for fixing the bridge support to the rotating platform are provided in the positioning groove.

[0017] Furthermore, a bracket for hanging protective baffles is provided on the outside of the frame.

[0018] Furthermore, it also includes a control system, which is electrically connected to all loading mechanisms, the first driving element, the second driving element, and the rotation angle measurement system respectively; the control system is preset with single-point off-center loading mode, double-sided off-center loading mode, overall tilting mode, and multi-point irregular loading mode, and can automatically control the stress value output of each loading mechanism.

[0019] Beneficial effects:

[0020] 1. Employing four independently controllable loading mechanisms arranged in a rectangular pattern, this system overcomes the limitation of traditional single-head loading, which can only achieve centrally symmetrical vertical loading. It can collaboratively deliver asymmetrical vertical pressure and tilting moment in any proportion, accurately simulating complex stress states commonly encountered in practical engineering, such as eccentric loads on beams, unilateral vehicle braking, beam bending deformation, and wind loads. The coverage of test conditions is significantly improved, completely resolving the industry problem of large discrepancies between traditional test results and the actual stress state of the supports, enabling test data to directly guide engineering design and application.

[0021] 2. By using a rotating table to rotate the bottom of the support while keeping the top fixed, the actual force path of more than 90% of the torsional failure of supports in actual engineering is perfectly reproduced, namely the passive torsion of the bottom of the support caused by uneven settlement of the roadbed and tilting of the pier.

[0022] 3. The upper vertical loading system and the lower composite testing system are independent of each other, with a clear force transmission path. This effectively isolates the mutual interference between vertical loading, lateral shear, and torsional loading, avoiding the force chain transmission distortion problem commonly found in traditional monolithic frame equipment. The loading mechanism is designed to adapt to the slight tilt of the push plate during loading, automatically releasing additional bending moments and ensuring that the vertical force always acts perpendicularly on the top surface of the support. This improves force transmission accuracy and significantly enhances the accuracy and reliability of the test data. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of an embodiment of this application;

[0025] Figure 2 This is a bottom view of an embodiment of this application;

[0026] Figure 3 for Figure 2 Sectional view of section AA;

[0027] Figure 4 This is a schematic diagram of the loading structure according to an embodiment of this application;

[0028] Figure 5 This is a schematic diagram of the structure of the ball joint component according to an embodiment of this application;

[0029] Figure 6 This is a schematic diagram of the structure of the composite testing system according to an embodiment of this application;

[0030] Figure 7 This is a cross-sectional view of the composite testing system according to an embodiment of this application.

[0031] In the figure: 1-frame; 2-slide rail; 3-base; 4-rotating table; 5-first driving element; 6-second driving element; 7-push plate; 8-ball joint; 801-ball head; 802-ball seat; 803-strain measurement unit; 9-hydraulic cylinder; 10-positioning hole; 11-distance measuring element; 12-pressure sensor; 13-control system; 14-support. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0035] In the description of this application, it should be noted that the use of terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" to indicate orientation or positional relationships is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product is in use. These terms are used solely for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the use of terms such as "first" and "second" in the description of this application is only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] Furthermore, the use of terms such as "horizontal" and "vertical" in the description of this application does not imply that the component is required to be absolutely horizontal or suspended, but rather that it may be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but rather that it may be slightly tilted.

[0037] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0038] Example

[0039] Please refer to Figures 1-7 This embodiment provides a stability testing device for bridge bearings, including: a frame 1; which serves as a rigid support frame and reaction foundation for the entire testing device, bears the reaction forces generated by all loading mechanisms and driving elements, provides a precise installation reference for each component, and ensures the stability of the overall geometric accuracy of the device.

[0040] A vertical loading system is installed on the upper part of the frame 1. The vertical loading system includes four loading mechanisms distributed in a rectangle and a loading mechanism for transmitting the pressure output by the loading mechanisms to the bridge bearing to be tested. Through the coordinated work of multiple independent and controllable loading mechanisms, the vertical force is transmitted to the top surface of the bridge bearing. By adjusting the output force ratio of each loading mechanism, various modes such as central symmetric loading, asymmetric loading, and inclined moment loading can be realized. It can simulate various actual stress states of the beam, such as eccentricity and bending, and the test conditions are closer to the actual engineering situation.

[0041] Specifically, the four rectangularly distributed loading mechanisms are arranged at the four corners of the top crossbeam through four loading units, forming a rectangular loading array. Each unit independently receives commands from the control system and outputs vertical forces without interference, enabling load distribution of any proportion from 0-100%, covering all possible asymmetric loading conditions. These loading mechanisms, acting as intermediate force transmission components between the loading mechanisms and the bearings under test, converge and uniformly transmit multiple dispersed loading forces to the top surface of the bridge bearings, while also adapting to minor deformations during the loading process.

[0042] A composite testing system is installed at the lower part of the frame 1. The composite testing system includes a slide rail 2, a base 3, a rotary table 4, a first driving element 5, and a second driving element 6. The slide rail 2 is fixed to the frame 1 laterally, and the base 3 is slidably connected to the slide rail 2. The rotary table 4 is rotatably connected to the top surface of the base 3, and the bottom surface of the bridge bearing to be tested is installed on the top surface of the rotary table 4, and its top surface is fixedly connected to the loading mechanism. The above-mentioned composite testing system integrates two loading functions, transverse shear and torsion. Shear deformation is achieved by the transverse sliding of the base 3, and torsional deformation is achieved by the rotation of the rotary table 4. All loading actions are applied to the bottom of the bearing, which is consistent with the force path of the bearing in actual engineering.

[0043] Specifically, the aforementioned slide rail 2 is fixed to the base beam at the bottom of the frame 1, providing precise linear motion guidance for the base 3, restricting all degrees of freedom of the base 3 except for lateral sliding, ensuring that the lateral shear force is always parallel to the shear plane of the support, and avoiding the generation of additional bending moments. The aforementioned base 3 serves as the load-bearing platform of the composite testing system, simultaneously supporting the rotary table 4 and two drive elements. It slides laterally with the slide rail 2, transmitting the linear motion of the first drive element 5 to the bottom of the support, providing a unified installation reference for the rotary table 4 and the drive elements. The bottom of the aforementioned rotary table 4 extends into the base 3 and is rotatably connected, allowing it to rotate freely around the vertical axis, converting the linear motion of the second drive element 6 into rotation around the axis, causing torsional deformation at the bottom of the support.

[0044] The first driving element 5 is connected between the frame 1 and the base 3, and is used to drive the base 3 to slide laterally along the slide rail 2. The first driving element 5 outputs linear thrust / tension, which drives the base 3 to slide laterally along the slide rail 2, so that the bottom of the support is relatively displaced relative to the fixed top, thereby generating shear stress and deformation inside the support, which can simulate the lateral shear force under vehicle braking, earthquake and other actions.

[0045] The second driving element 6 is connected between the base 3 and the rotary table 4, and is used to drive the rotary table 4 to rotate relative to the base 3 about a vertical axis. The second driving element 6 outputs a linear thrust / tension, which drives the rotary table 4 to rotate about a vertical axis through a hinge, causing the bottom of the support to rotate relative to the fixed top, thereby generating torsional stress and deformation inside the support, simulating the torsion of the support bottom caused by uneven settlement of the roadbed and tilting of the pier.

[0046] Please refer to Figures 1-7 Furthermore, the loading mechanism includes a push plate 7 and four ball joints 8. The output end of each loading mechanism is connected to the corresponding corner of the push plate 7 through one of the ball joints 8. The geometric center of the rectangle formed by the center line of the four loading mechanisms is on the same vertical line as the geometric center of the push plate 7 and the geometric center of the bridge support to be tested. The four loading mechanisms independently control the output force to collaboratively apply arbitrary mode of asymmetric vertical pressure and tilting moment to the push plate 7, and release additional bending moment through the ball joints 8.

[0047] Specifically, the aforementioned push plate 7 serves as the main component of the loading mechanism, providing a unified force transmission surface for the four loading mechanisms, and converging the four dispersed loading forces to uniformly transmit them to the top surface of the support. The four ball joints 8 connect the output ends of the loading mechanisms to the corners of the push plate 7, allowing the push plate 7 to rotate slightly in any direction relative to the loading mechanism, releasing the additional bending moment generated during loading. Through precise machining and installation adjustments, the three geometric centers—the center of the loading mechanism rectangle, the center of the push plate 7, and the center of the support—are aligned on the same vertical line. When the four loading mechanisms output the same force, the resultant force application point passes precisely through the center of the support, achieving centrally symmetrical loading; when outputting different forces, the resultant force application point can be precisely controlled at any position. Each loading mechanism is equipped with an independent servo valve and sensor, receiving independent commands from the control system and outputting the set force value without interference. Through the vector synthesis of the four forces, a resultant force and resultant torque of arbitrary magnitude and direction can be generated.

[0048] Please refer to Figure 1 Furthermore, the loading mechanism is a hydraulic cylinder 9, which is installed on the top crossbeam of the frame 1, and the piston rod end of the hydraulic cylinder 9 is fixedly connected to the upper end of the ball joint 8.

[0049] In this embodiment, the hydraulic cylinder 9 generates thrust through the pressure of hydraulic oil, and the force is transmitted to the ball joint 8 when the piston rod extends. The cylinder body is hinged to the top crossbeam via a hinge seat, allowing the hydraulic cylinder 9 to oscillate slightly with the tilt of the push plate 7. It has a large output force, with a single cylinder rated thrust exceeding 5000kN, making it suitable for large-tonnage support tests.

[0050] Please refer to Figures 1-7Furthermore, the ball joint 8 is an integrated multi-dimensional force ball joint sensor, including a ball head 801, a ball seat 802, and a strain measurement unit 803; the strain measurement unit 803 is disposed in the equatorial plane of the ball head 801 or in the concave surface of the ball seat 802, and is used to simultaneously measure the vertical force, horizontal shear force, and additional bending moment acting on the ball joint 8.

[0051] In this embodiment, the top of the ball head 801 is connected to the flange and fixed to the end of the piston rod of the loading mechanism by high-strength bolts. The ball head 801 serves as the main elastic body and force transmission component. The spherical surface of the ball head 801 is precisely fitted with the ball seat 802. The inner spherical surface of the ball seat 802 is in contact with the ball head 801. The bottom is fixed to the corner of the push plate 7 by the lower connecting flange. The strain measurement unit 803 is attached to the strain gauge array and signal processing circuit on the equatorial surface of the ball head 801 or the concave surface of the ball seat 802.

[0052] The strain measurement unit 803 is provided with a protective structure (not shown in the figure), an epoxy resin inner layer and a stainless steel outer protective cover or sealant layer, and the signal output interface is a waterproof aviation plug for oilfield workers, used to connect to the control system.

[0053] Please refer to Figure 4 Furthermore, the push plate 7 is provided with positioning holes 10 that are adapted to the mounting holes on the top surface of the bridge bearing to be tested, and the push plate 7 and the bridge bearing are fixedly connected by bolts.

[0054] In this embodiment, the push plate 7 is machined with positioning holes 10 that correspond one-to-one with the mounting holes on the top surface of the support to be tested. The push plate 7 is firmly connected to the top surface of the support by high-strength bolts, which restricts the relative sliding and rotation between the two. The firm connection ensures that there is no relative displacement between the top of the support and the push plate 7 during shear and torsion tests.

[0055] Please refer to Figures 1-3 Furthermore, there are two slide rails 2, which are arranged parallel and symmetrically on the frame 1. The distance between the two slide rails 2 is adapted to the size of the base 3. The frame 1 is provided with a ranging element 11 aligned with the base 3.

[0056] In this embodiment, the two parallel symmetrical slide rails 2 work in conjunction with the base 3 and the first driving element 5. The two slide rails 2 are arranged parallel and symmetrically on the bottom foundation beam of the frame 1, and the base 3 is connected to the two slide rails 2 through a slider. The symmetrical layout ensures that the force on the base 3 is evenly distributed on the two slide rails 2, avoiding unilateral overload. The base 3 is installed on the side of the frame 1, aligned with the side of the base 3, and the lateral displacement of the base 3 is measured in real time as a displacement feedback signal for the shear test. Directly measuring the displacement of the base 3 avoids the errors caused by indirect calculation of the displacement through the driving element.

[0057] Please refer to Figure 1Furthermore, the first driving element 5 is a servo hydraulic cylinder 9. The cylinder body end of the servo hydraulic cylinder 9 is hinged to the frame 1 through a first hinge seat, and the piston rod end of the servo hydraulic cylinder 9 is hinged to the center position of the side of the base 3 through a second hinge seat. The servo hydraulic cylinder 9 integrates a wire-type displacement sensor and a pressure sensor 12, which are used to detect the lateral shear displacement and shear force in real time, respectively.

[0058] In this embodiment, the aforementioned servo hydraulic cylinder 9 precisely controls the flow and pressure of hydraulic oil through a servo valve, achieving high-precision force and displacement control. Both ends are hinged to the frame 1 and base 3 respectively via hinge seats, allowing the base 3 to swing slightly during sliding, releasing additional bending moment. The hinged connection avoids lateral forces on the hydraulic cylinder 9, extending its service life. The pull-wire displacement sensor's pull end is fixed to the piston rod end of the hydraulic cylinder 9, measuring the piston rod elongation in real time. The pressure sensor 12 is installed in the rodless chamber of the hydraulic cylinder 9, measuring the hydraulic oil pressure in real time and calculating the output force based on the pressure.

[0059] Please refer to Figure 6 Furthermore, the rotating table 4 is provided with a positioning groove adapted to the bridge support to be tested, and screws for fixing the bridge support to the rotating table 4 are provided in the positioning groove.

[0060] In this embodiment, the rotary table 4 is machined with a positioning groove that matches the contour of the bottom surface of the support to be tested. After the support is placed in the positioning groove, it is initially positioned. Then, the bottom surface of the support is firmly connected to the rotary table 4 with screws. This achieves rapid and accurate positioning of the bottom of the support, ensuring that the center of the support coincides with the rotation center of the rotary table 4.

[0061] Please refer to Figures 1-3 Furthermore, the frame 1 is provided with a bracket 14 for hanging a protective baffle (not shown in the figure) on its exterior.

[0062] In this embodiment, the protective baffle bracket on the outside of the frame 1 is welded to the outer column of the frame 1. The bracket 14 is used to install a transparent acrylic or steel plate protective baffle to isolate the test area from the external environment. This prevents splashes generated when the support is damaged, protects the safety of the test personnel, and prevents external dust and debris from entering the equipment and affecting its operation.

[0063] Furthermore, it also includes a control system 13, which is electrically connected to all loading mechanisms, the first driving element 5, the second driving element 6 and the rotation angle measurement system respectively; the control system 13 is preset with single-point off-center loading mode, double-sided off-center loading mode, overall tilting mode and multi-point irregular loading mode, and can automatically control the stress value output of each loading mechanism.

[0064] In this embodiment, the aforementioned control system acts as the brain of the device, receiving feedback signals from all sensors and adjusting the output of each actuator in real time through a built-in PID control algorithm to achieve the predetermined loading process. Simultaneously, it completes data acquisition, storage, processing, and display. The loading parameters and control logic for the four most common asymmetric loading conditions in engineering are pre-stored in the control system. The test personnel only need to select the corresponding mode, and the system can automatically calculate and control the four loading mechanisms to output the corresponding force values.

[0065] The specific experimental steps are as follows:

[0066] S1: Fix the bottom surface of the bridge bearing to be tested on the top surface of the rotating table 4, and fix the top surface of the bridge bearing to the push plate 7 of the loading mechanism; adjust the installation position so that the geometric center of the rectangle formed by the line connecting the centers of the four loading mechanisms, the geometric center of the push plate 7, and the geometric center of the bridge bearing to be tested are on the same vertical line.

[0067] S2: Perform no-load zero-point calibration on each loading mechanism, the first driving element 5, the second driving element 6, and each integrated multi-dimensional force ball joint sensor to eliminate initial installation gap and zero-point drift error;

[0068] S3: Control the four loading mechanisms to output the preset preload synchronously, apply a uniform preload to the bridge bearing to be tested through the push plate 7, maintain the preset time and then unload to zero, and complete the tightness of the specimen contact surface and the elimination of system gaps.

[0069] S4: The four loading mechanisms independently control their respective output forces to collaboratively apply asymmetric vertical pressure and tilting moment in a set mode to the push plate 7; at the same time, the ball joint 8 is used to adaptively rotate and release the additional bending moment generated during the loading process.

[0070] And selectively perform at least one of the following loads:

[0071] The first driving element 5 drives the base 3 to slide laterally along the slide rail 2, causing the bottom of the bridge support to be tested to undergo lateral shear deformation relative to the top.

[0072] The second driving element 6 drives the rotary table 4 to rotate relative to the base 3 around the vertical axis, causing the bottom of the bridge support to be tested to undergo torsional deformation, simulating the torsional stress condition of the lower pier.

[0073] S5: Through the strain measurement unit 803 of each integrated multi-dimensional force ball joint sensor, the vertical force, horizontal shear force and additional bending moment at each ball joint position are collected in real time and synchronously; the transverse shear displacement, the rotation angle of the rotary table 4 and the load parameters output by the loading mechanism are collected synchronously.

[0074] S6: When the preset loading condition, preset displacement / rotation limit, or when the support deformation instability or sudden load change is detected, stop loading and unload to zero in stages according to the set rate to complete the bridge support stability test.

[0075] Furthermore, during the overall tilting ultimate moment test, this testing equipment can simulate the overall tilting of the beam caused by seismic action, strong wind load, and uneven settlement of the piers, subjecting the supports to the ultimate overturning moment. The control system controls the four loading mechanisms to output linearly gradient force values, causing the push plate to tilt at a set angle (maximum tilt angle up to 5°), applying a pure tilting moment to the supports; the ball joint completely releases the additional bending moment, ensuring the accuracy of moment transmission.

[0076] The usage method is as follows:

[0077] 1. Complete steps S1-S3.

[0078] 2. Mode Selection: Select "Overall Tilting Mode", input the target tilt angle and estimated limit torque, and the system will achieve precise tilting of the push plate through displacement control (rather than force control).

[0079] 3. Graded loading: Angle control is used for graded loading, with the tilt angle increasing by 0.5° at each level and held for 5 minutes at each level. The output force of each hydraulic cylinder and the bending moment of the ball joint are recorded. When the tilt angle reaches 3°, the angle is changed to 0.2° at each level and held for 3 minutes at each level.

[0080] 4. Limit judgment: When the support experiences partial detachment, overall slippage, or the overturning moment can no longer increase, it is determined that the overall tilting limit moment has been reached, and loading is stopped.

[0081] 5. Data recording: Extract the ultimate tilt angle, corresponding overturning moment, and percentage of support detachment area.

[0082] Furthermore, when conducting multi-point irregular loading ultimate bearing capacity tests, this testing equipment can simulate the irregular stress limit state of bridge bearings under complex construction loads, explosive impact loads, or localized damage. The control system allows users to customize the arbitrary force ratio of the four loading mechanisms (0-100% arbitrary ratio) to achieve arbitrary shape of resultant force distribution, covering all possible irregular vertical loading conditions.

[0083] The specific experimental method is as follows:

[0084] 1. Complete steps S1-S3.

[0085] 2. Custom loading settings: Manually input the target force ratio of the four hydraulic cylinders (e.g., 60%, 20%, 15%, 5%) in the control system to set the loading rate.

[0086] 3. Graded loading: The load-displacement dual control is adopted. When the displacement change rate exceeds 0.5mm / min, it automatically switches to displacement control.

[0087] 4. Limit determination: As before, focus on monitoring the deformation and cracking in the local stress concentration areas of the support.

[0088] 5. Data processing: Analyze the failure modes of supports under irregular load distribution and determine the most unfavorable loading combination.

[0089] This test equipment can simulate the fatigue failure limit of bearings caused by repeated vehicle loading and temperature cycles under cyclic loading conditions. The fatigue life of the bearings is determined by cyclically applying vertical, shear, or torsional loads through a control system.

[0090] The specific experimental method is as follows:

[0091] 1. Complete steps S1-S3.

[0092] 2. Cyclic Loading Settings: Select the cyclic loading mode, and enter the load amplitude, frequency (0.5-2Hz), and target number of cycles.

[0093] 3. Cyclic loading: Cyclic loading is performed according to the set parameters, with a pause every 1000 cycles to check for support damage.

[0094] 4. Fatigue limit determination: When fatigue cracks appear in the support, residual deformation exceeds the limit, or the bearing capacity decreases by 20%, the fatigue limit is determined to have been reached, and the actual number of cycles is recorded.

[0095] 5. Data processing: Plot the load-cycle curve (SN curve) to determine the fatigue limit of the support.

[0096] This experimental setup simulates the most complex stress state of bridge bearings under extreme disasters such as strong earthquakes and massive floods, under the combined effects of vertical eccentric loading, lateral shear, and bottom torsion, in a fully coupled ultimate load condition involving vertical eccentric loading, lateral shear, and torsion. Coupling loading of forces across all dimensions is achieved through independent synchronous control of three loading systems.

[0097] The specific experimental method is as follows:

[0098] 1. Complete steps S1-S3.

[0099] 2. Fully Coupled Loading Settings: Define the vertical off-center load ratio, shear displacement rate, and torsional angle rate in the control system, and set the synchronous loading logic for the three.

[0100] 3. Graded coupled loading: Multi-parameter coordinated control is adopted. After each loading stage, the load is held for 10 minutes until the deformation is completely stable before proceeding to the next stage. When any parameter reaches 70% of the predicted limit, the loading is switched to single-parameter fine-tuning.

[0101] 4. Limit judgment: When the support becomes unstable, severely damaged, or any parameter reaches the safety limit, all loading shall be stopped immediately; unloading shall be carried out in stages in the order of "unloading torsion first, then unloading shear and finally unloading vertical".

[0102] 5. Comprehensive analysis: Draw the three-dimensional ultimate bearing capacity surface and calculate the safety reserve factor of the support under fully coupled working conditions.

[0103] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A stability testing device for bridge bearings, characterized in that, include: Rack (1); A vertical loading system is installed on the upper part of the frame (1). The vertical loading system includes four loading mechanisms distributed in a rectangular shape and a loading mechanism for transmitting the pressure output by the loading mechanisms to the bridge support to be tested. A composite testing system is set at the lower part of the frame (1). The composite testing system includes a slide rail (2), a base (3), a rotary table (4), a first driving element (5), and a second driving element (6). The slide rail (2) is fixed to the frame (1) in the transverse direction, and the base (3) is slidably connected to the slide rail (2). The rotary table (4) is rotatably connected to the top surface of the base (3). The bottom surface of the bridge bearing to be tested is installed on the top surface of the rotary table (4), and its top surface is fixedly connected to the loading mechanism. The first driving element (5) is connected between the frame (1) and the base (3) and is used to drive the base (3) to slide laterally along the slide rail (2); The second driving element (6) is connected between the base (3) and the rotary table (4) to drive the rotary table (4) to rotate relative to the base (3) about the vertical axis.

2. The stability testing equipment for bridge bearings according to claim 1, characterized in that, The loading mechanism includes a push plate (7) and four ball joints (8). The output end of each loading mechanism is connected to the corresponding corner of the push plate (7) through one of the ball joints (8). The geometric center of the rectangle formed by the center line of the four loading mechanisms is on the same vertical line as the geometric center of the push plate (7) and the geometric center of the bridge support to be tested. The four loading mechanisms independently control the output force to apply arbitrary mode of asymmetric vertical pressure and tilting moment to the push plate (7) in a coordinated manner, and release additional bending moment through the ball joints (8).

3. The stability testing equipment for bridge bearings according to claim 2, characterized in that, The loading mechanism is a hydraulic cylinder (9), which is installed on the top crossbeam of the frame (1). The piston rod end of the hydraulic cylinder (9) is fixedly connected to the upper end of the ball joint (8).

4. The stability testing equipment for bridge bearings according to claim 2, characterized in that, The ball joint (8) is an integrated multi-dimensional force ball joint sensor, including a ball head (801), a ball seat (802) and a strain measurement unit (803); the strain measurement unit (803) is located on the equatorial plane of the ball head (801) or in the concave surface of the ball seat (802), and is used to simultaneously measure the vertical force, horizontal shear force and additional bending moment acting on the ball joint (8).

5. The stability testing equipment for bridge bearings according to claim 2, characterized in that, The push plate (7) is provided with positioning holes (10) that are compatible with the mounting holes on the top surface of the bridge bearing to be tested. The push plate (7) and the bridge bearing are fixedly connected by bolts.

6. The stability testing equipment for bridge bearings according to claim 1, characterized in that, The number of slide rails (2) is two. The two slide rails (2) are arranged parallel and symmetrically on the frame (1). The distance between the two slide rails (2) is adapted to the width of the base (3). The frame (1) is provided with a ranging element (11) aligned with the base (3).

7. The stability testing equipment for bridge bearings according to claim 6, characterized in that, The first driving element (5) is a servo hydraulic cylinder (9). The cylinder body end of the servo hydraulic cylinder (9) is hinged to the frame (1) through a first hinge seat, and the piston rod end of the servo hydraulic cylinder (9) is hinged to the center of the side of the base (3) through a second hinge seat. The servo hydraulic cylinder (9) is equipped with a pressure sensor (12) for real-time detection of shear force.

8. The stability testing equipment for bridge bearings according to claim 1, characterized in that, The rotating table (4) is provided with a positioning groove adapted to the bridge support to be tested, and screws for fixing the bridge support on the rotating table (4) are provided in the positioning groove.

9. The stability testing equipment for bridge bearings according to claim 1, characterized in that, The frame (1) is provided with a bracket (14) for hanging protective baffles on the outside.

10. The stability testing equipment for bridge bearings according to claim 1, characterized in that, It also includes a control system, which is electrically connected to all loading mechanisms, the first driving element (5), the second driving element (6) and the rotation angle measurement system respectively; the control system has preset single-point off-center loading mode, double-sided off-center loading mode, overall tilting mode and multi-point irregular loading mode, and can automatically control the stress value output of each loading mechanism.

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