Test loading device and method considering additional axial force influence of upper layer column
By combining differentiated circular plates with self-balancing beams and pressure compensation components, targeted loading of core concrete in super high-rise buildings was achieved, solving the problems of simulation distortion and long-term loading instability in existing technologies, and providing accurate experimental data support.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENZHEN UNIV
- Filing Date
- 2026-04-02
- Publication Date
- 2026-05-19
AI Technical Summary
Existing technologies struggle to simulate the loading mechanism of concrete-filled steel tubular columns in super high-rise buildings under the influence of additional axial forces from upper-level columns without affecting the vertical load transfer at the beam ends, especially since the core concrete is difficult to transfer vertical loads through bond friction.
A combination design of differentiated circular plates and self-balancing beams is adopted. The core concrete is targeted by tie rods. Combined with pressure compensation components and a dual-redundant monitoring system, the core concrete is ensured to bear the additional axial force of the upper column alone. Fiber optic strain gauges and tension sensors are used for real-time monitoring and compensation.
It has achieved long-term stable stress simulation of core concrete, and the test data is accurate and reliable. It solves the problems of simulation distortion and long-term loading instability of traditional devices, and provides a scientific basis for the design of steel tube concrete column structures.
Smart Images
Figure CN122062973A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of concrete-filled steel tubular (CFST) performance testing equipment, specifically relating to a test loading device and method that takes into account the influence of additional axial force on upper columns. Background Technology
[0002] Currently, it is generally accepted that axial compression tests are required to investigate the axial compression performance of concrete-filled steel tubular (CFST) columns. A vertical load is applied to the top of the CFST column to investigate its overall failure mode and axial compression performance under this load. However, in high-rise buildings, the proportion of the load transferred from the beams to the CFST column is relatively large. For CFST columns without joints, the core concrete cannot easily transfer the vertical load through the bond friction with the steel tubing; instead, it is mainly affected by the additional axial force directly transmitted downwards from the upper-level columns. This self-balancing device can be used to load the CFST column top affected by the additional axial force from the upper-level columns. Summary of the Invention
[0003] In view of this, the purpose of the present invention is to provide a test loading device and method that considers the influence of additional axial force on the upper column, so as to solve the problem of considering the influence of additional axial force on the internal core concrete from the upper column to the current column without affecting the loading method of transmitting vertical load from the beam end to the steel pipe wall.
[0004] To achieve the above objectives, the present invention provides the following technical solution: A test loading device considering the influence of additional axial force on an upper column includes a concrete-filled steel tube column and a loading assembly that applies axial force to it. Multiple loading beams are spaced circumferentially on the outer surface of the concrete-filled steel tube column, and an upper self-balancing beam and a lower self-balancing beam are respectively located at both ends of the column. A first circular plate, with a diameter smaller than the column, is positioned between the column and the upper self-balancing beam. A second circular plate, with a diameter larger than the column, is positioned between the column and the lower self-balancing beam. The column, upper self-balancing beam, lower self-balancing beam, first circular plate, and second circular plate are all coaxially arranged and abut against each other. The surfaces of the upper and lower self-balancing beams are each provided with vertically oriented through holes, and a tie rod is connected between any two corresponding upper and lower through holes. Each tie rod is spaced around the circumference of the steel-concrete composite column, and a first force sensor is provided on the surface of each tie rod. The loading assembly includes a base and a pressure member disposed on top of it. The pressure member is vertically oriented and coaxial with the steel-concrete composite column. The steel-concrete composite column is disposed directly below the pressure member, and the lower self-balancing beam abuts against the surface of the base. The output end of the pressure member is connected to a distribution beam coaxial with it, and the lower surface of the distribution beam is provided with an upper loading seat that abuts against the upper surface of each loading beam.
[0005] Furthermore, each of the aforementioned tie rods includes a first tie rod and a second tie rod detachably connected thereto. The first tie rod and the second tie rod are spaced vertically and coaxially arranged, and both ends of the first tie rod and the second tie rod are threaded. The adjacent ends of the first tie rod and the second tie rod are threadedly connected to a connecting cylinder, and the two ends that are far apart from each other pass through the corresponding upper self-balancing beam and lower self-balancing beam and are threadedly connected to fastening blocks. The outer surface of each first tie rod is provided with a first force sensor.
[0006] Furthermore, the surface of the lower self-balancing beam is provided with a pressure compensation component that applies axial pressure to the steel-concrete composite column. The pressure compensation component includes a gear ring coaxially and rotatably disposed on the surface of the lower self-balancing beam, a gear ring meshing with the gear ring, and a driving component that drives the gear ring to rotate. The driving component is fixedly disposed on the surface of the lower self-balancing beam. The gear ring is provided in multiple parts, each corresponding to a fastening block on the second tie rod. Each gear ring is coaxially sleeved and fixed on the outer ring surface of the corresponding fastening block. A first displacement sensor for detecting the interior of the steel-concrete composite column is provided at the center of the first circular plate, and a second displacement sensor for detecting the interior of the steel-concrete composite column is provided at the center of the second circular plate.
[0007] Furthermore, the connecting cylinder includes a first sleeve, a tension sensor, and a second sleeve arranged sequentially along a straight line. The two ends of the tension sensor are threadedly connected to the first sleeve and the second sleeve respectively and are coaxially arranged. The free end of the first sleeve is threadedly connected to the corresponding first pull rod, and the free end of the second sleeve is threadedly connected to the corresponding second pull rod.
[0008] Furthermore, all the tension sensors are fiber Bragg grating strain gauges, and each of the first pull rods has multiple fiber Bragg grating strain gauges on its surface. The fiber Bragg grating strain gauges are evenly spaced around the axis of the first pull rod, and each fiber Bragg grating strain gauge is located near the center of the length of the first pull rod.
[0009] A test loading method considering the influence of additional axial force on the upper column, applied in the aforementioned test loading device considering the influence of additional axial force on the upper column, includes the following implementation steps: Step S1: Preparation before the test; Place the lower loading stool in the preset position and adjust it to a horizontal state. Install each component in the designated position from bottom to top, while ensuring that the lower loading stool, the second circular plate, the lower self-balancing beam, the steel pipe concrete column, the first circular plate, and the upper self-balancing beam are all coaxially set. Then install each tie rod and connecting cylinder, and initially fix them between the upper and lower self-balancing beams. Finally, install each fiber optic strain gauge and connect each sensor to the data acquisition instrument and the main control unit. Step S2, System Calibration and Preloading; Start the pressurizing component and apply preloading to the specified pressure at the preset loading rate. Maintain the load stable for a period of time. During this process, observe the connection status of each component to ensure there is no looseness or deformation, and check for any abnormal fluctuations in the signals of each sensor. If any abnormality occurs, immediately unload and adjust. If there is no abnormality, unload to zero at the same rate to complete the preloading. Step S3: Formal Loading and Force Locking; Start the pressurizing component and slowly apply the load to the preset target. During the loading process, collect data from each sensor in real time and monitor the tension balance of each tie rod to ensure uniform stress on the core concrete. Maintain the pressurizing component to apply load stably. After the core concrete deformation stabilizes, tighten the fastening blocks and connecting cylinders on each first tie rod and second tie rod to keep the tie rods taut. Monitor the tension of the tie rods in real time. After confirming that the tension of the tie rods is stable and there are no abnormalities in any component, control the pressurizing component to slowly unload the pressure until the pressurizing component is completely separated from the upper self-balancing beam, completing the force conversion from the external force of the pressurizing component to the self-balancing tension of the tie rods. Then install the distribution beam and the upper loading stool, start the pressurizing component again and slowly apply the load to the loading beam to the preset target, while collecting experimental data. Step S4: Test monitoring and tensile deviation compensation; The data acquisition instrument synchronously acquires data from each of the first force sensor, first displacement sensor, second displacement sensor, and tension sensor in real time. Simultaneously, the main control unit calculates the difference between the first displacement sensor and the second displacement sensor in real time. With core concrete creep value; when When the deviation exceeds a preset threshold, the main control unit initiates automatic compensation, calculates the compensation torque based on the direction of the deviation, and controls the drive components to synchronously tighten or loosen the fastening blocks of each pair of tie rods via gear transmission. The tension value is then fed back in real time via a tension sensor until... Within the specified range; Step S5: When the steel-concrete composite column is damaged, control the drive component to simultaneously loosen the fastening blocks of each tie rod, slowly release the tension of the tie rods until the tension drops to zero, then remove each component in sequence, clean the experimental site, and save the experimental data.
[0010] The beneficial effects of this invention are as follows: 1. The core advantage of this device and method lies in achieving targeted loading and long-term stable stress simulation of the core concrete. Through the collaborative design of differentiated circular plates and cross-shaped self-balancing beams, the transmission of force to the steel tube wall is precisely blocked, perfectly restoring the real working condition of "core concrete bearing the additional axial force of the upper column alone" in the steel tube concrete column without joint structure of super high-rise buildings. The segmented tie rod combined with the self-balancing loading principle gets rid of the constraints of external reaction walls and other auxiliary equipment, while improving the adaptability of the device to specimens of different sizes and the ease of assembly. 2. The supporting pressure compensation components and dual-redundant monitoring system further ensure the accuracy and reliability of the test data. The fiber optic strain gauge and series tensile sensor cross-validate and capture tensile fluctuations and creep deformation of the core concrete in real time. The drive motor drives the gear ring to synchronously adjust the preload of each screw, realizing automatic compensation for tensile deviation and ensuring that the core concrete always bears a constant axial force. The overall solution has a high degree of automation and is easy to maintain. It solves the pain points of traditional axial compression test condition simulation distortion and long-term loading instability, and provides a scientific basis for the design of steel tube concrete column structures. It has significant practical value and patent innovation.
[0011] Other advantages, objectives, and features of the invention will be set forth in the following description and will be apparent to those skilled in the art in some respects, or may be learned by practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description
[0012] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 This is a schematic diagram of the overall structure of the steel-concrete composite column and loading assembly of the present invention; Figure 2 This is a side view of the overall structure of the steel-concrete composite column and loading assembly of the present invention; Figure 3 for Figure 1 Enlarged view of point A in the middle; Figure 4 This is a schematic diagram of the steel-concrete composite column and tie rod structure of the present invention.
[0013] The following labels are shown in the attached diagram: 1. Steel pipe concrete column; 2. Upper self-balancing beam; 3. Lower self-balancing beam; 4. First circular plate; 5. Second circular plate; 6. Tie rod; 601. First tie rod; 602. Second tie rod; 7. First force sensor; 8. Pressurizing component; 9. Connecting cylinder; 901. First sleeve; 902. Second sleeve; 10. Fastening block; 11. Gear ring; 12. Driving component; 13. Distribution beam; 14. Upper loading stool; 15. Lower loading stool; 16. Base; 17. Second force sensor; 18. Loading beam; 19. Lower loading plate. Detailed Implementation
[0014] like Figures 1-4 As shown, A test loading device considering the influence of additional axial force on an upper column includes a concrete-filled steel tube column 1 and a loading assembly that applies axial force to it. Four loading beams 18 are evenly spaced circumferentially on the outer surface of the concrete-filled steel tube column 1, and the four loading beams 18 are positioned near the top of the column. An upper self-balancing beam 2 and a lower self-balancing beam 3 are respectively provided at both ends of the column. Both the upper and lower self-balancing beams 2 and 3 are shaped like a cross in the horizontal plane. A first circular plate 4 is provided between the column and the upper self-balancing beam 2, and the diameter of the first circular plate 4 is smaller than that of the column. A second circular plate 5 is provided between the column and the lower self-balancing beam 3, and the diameter of the second circular plate 5 is larger than that of the column. The column, the upper self-balancing beam 2, the lower self-balancing beam 3, the first circular plate 4, and the second circular plate 5 are all coaxially arranged and abut against each other. Vertical through holes are opened on the surfaces of the upper and lower self-balancing beams 2 and 3, and any two corresponding through holes are connected by a vertical through hole. A common connection is provided by tie rods 6, of which four tie rods 6 are evenly spaced around the vertical axis of the steel-concrete composite column 1, and each tie rod 6 has a first force sensor 7 on its surface; the loading assembly includes a base 16 and a pressure member 8 disposed above it, the pressure member 8 being a jack, the pressure member 8 being vertically arranged and coaxial with the steel-concrete composite column 1, the steel-concrete composite column 1 being positioned directly below the pressure member 8, and the lower surface of the lower self-balancing beam 3 being flush with the base 16. The surface abuts against the base 16, and a lower loading plate 19 is provided between the lower self-balancing beam 3 and the base 16. The output end of the pressure member 8 is connected to a distribution beam 13 coaxial with it, and an upper loading stool 14 that abuts against the upper surface of each loading beam 18 is welded and fixed to the lower surface of the distribution beam 13. The upper loading stool 14 and each loading beam 18 are detachably connected by bolts and nuts. When the loading stool 14 abuts against and is fixedly connected to the upper surface of each loading beam 18, there is a gap between the lower surface of the distribution beam 13 and the upper surface of the upper self-balancing beam 2.
[0015] As shown in the diagram, when the steel-concrete composite column 1 needs to simulate the additional axial force of the superstructure, the upper self-balancing beam 2, the lower self-balancing beam 3, and the steel-concrete composite column 1 are first set coaxially. Then, each tie rod 6 is arranged around the steel-concrete composite column 1, with both ends of each tie rod 6 passing through the through holes on the surfaces of the upper self-balancing beam 2 and the lower self-balancing beam 3. The tie rods 6, the upper self-balancing beam 2, and the lower self-balancing beam 3 are then tightened to form an integral structure. The steel-concrete composite column 1 is then moved to a position directly below the pressure-applying component 8, ensuring that the steel-concrete composite column 1 and the output end of the pressure-applying component 8 are coaxial. After adjusting the position, the pressure-applying component 8 is activated and vertical pressure is applied to the upper self-balancing beam 2. At this time, the upper loading stool 14 and the distribution beam 13 are not installed; the pressure-applying component 8 only applies force to the upper self-balancing beam 2 until the pressure-applying component 8 reaches the preset value. Then, the tightness between the tie rods 6 and the upper and lower self-balancing beams 2 and 3 is adjusted again. This causes the tie rod 6 to be under tension and in a taut state. At this time, the core concrete inside the steel-concrete composite column 1 is compressed, resulting in elastic deformation (similar to a compressed spring), and it possesses elastic potential energy to "restore its original state." Then, the jack is reset, and no more axial force is applied to the steel-concrete composite column 1. At this time, the elastic potential energy of the core concrete inside the steel-concrete composite column 1 attempts to be released (i.e., to restore its original state), but it cannot freely extend due to the rigid constraint of the tie rod 6. The "restoration tendency" of the concrete will generate an outward pushing force on the upper self-balancing beam 2 and the lower self-balancing beam 3. According to the action and reaction forces, the upper and lower self-balancing beams 3 will transmit the reverse tension through the tie rod 6, ultimately forming a self-balanced state of "concrete under compression → tie rod under tension." The axial pressure on the core concrete (i.e., the simulated additional axial force of the upper column) is equal in magnitude and opposite in direction to the total tension on the tie rod 6 (mechanical equilibrium). Therefore, by monitoring the tension of the tie rod 6 through the first force sensor 7, the actual force on the core concrete can be indirectly and accurately obtained. Secondly, when simulating the situation where the load of this floor is transferred to the bottom column by the beam in a super high-rise building, the distribution beam 13 and each upper loading stool 14 are first installed on the surface of the upper self-balancing beam 2, and the coaxial arrangement is ensured. Then, the upper loading stool 14 and the loading beam 18 are fixedly connected by bolts. Then, the pressure member 8 is controlled to move towards the steel tube concrete column 1. The vertical load applied by the pressure member 8 is transferred to the steel tube wall of the steel tube concrete column 1 through the distribution beam 13, loading stool 14 and loading beam 18. If the steel tube concrete column 1 has a node structure inside, the vertical load can be transferred to the core concrete inside through the node structure. If there is no node structure, the vertical load on the core concrete is very small (only the load transferred between the steel tube concrete by the bonding and friction). By continuously applying axial force by the pressure member 8 until the steel tube concrete column 1 fails, its bearing capacity can be obtained. Therefore, the device of the present invention has two methods of applying load. The upper self-balancing beam 2 and the lower self-balancing beam 3 can achieve additional axial force. The vertical load applied to the steel pipe by the distribution beam 13, the loading stool 14, and the loading beam 18 is to simulate the situation of large beam end load in high-rise buildings. When this beam end load is transferred, it is applied to the steel pipe wall. The upper self-balancing beam 2 and the lower self-balancing beam 3 apply pre-loaded axial force to the core concrete inside the steel tube concrete column 1 separately. Because the pre-loaded axial force does not act directly on the top surface of the steel tube concrete column 1, and the influence of the additional axial force from the upper column mainly includes the self-weight of the upper column and the vertical load transferred to the concrete through the bonding effect. This self-balancing device (upper self-balancing beam, lower self-balancing beam, and tie rod) is to achieve the application of pre-loaded axial force to the concrete separately without affecting the application of beam end load. Meanwhile, this invention achieves separate loading of the core concrete through the differentiated design of the first circular plate 4 and the second circular plate 5. The first circular plate 4 only covers the core concrete and does not contact the steel pipe wall, thus physically blocking the transmission of force to the steel pipe. This perfectly simulates the actual stress state of "core concrete bearing the additional axial force of the upper column alone" in super high-rise buildings, solving the problem that traditional devices cannot distinguish between the core concrete and the steel pipe under stress when "loaded as a whole". The test data is more in line with the actual engineering situation. Compared with the existing overall loading device, this application achieves targeted additional axial force loading of the core concrete for the first time through the combination design of differentiated circular plates (first circular plate, second circular plate) + self-balancing beams (upper self-balancing beam, lower self-balancing beam) + tie rods 6. Moreover, it does not require long-term occupation of large equipment such as jacks, solving the defects of traditional loading devices such as distorted working condition simulation and inconvenience of long-term loading.
[0016] In this embodiment, each of the pull rods 6 includes a first pull rod 601 and a second pull rod 602 detachably connected to it. The first pull rods 601 have the same size and length. The first pull rods 601 and the second pull rods 602 are spaced vertically and coaxially arranged. Both ends of the first pull rods 601 and the second pull rods 602 are threaded. The adjacent ends of the first pull rods 601 and the second pull rods 602 are threadedly connected to a connecting cylinder 9. The two ends that are far apart from each other pass through the corresponding upper self-balancing beam 2 and lower self-balancing beam 3 and are threadedly connected to a fastening block 10. The outer surface of each first pull rod 601 is provided with a first force sensor 7.
[0017] As shown in the figure, the first tie rods 601 and the second tie rods 602 are connected by the connecting sleeve 9 to form the tie rod 6. The tie rod 6 is then connected to the upper self-balancing beam 2 and the lower self-balancing beam 3. The tie rods 6, through a segmented design and sleeve connection, can adapt to steel-concrete composite columns 1 of different lengths within a certain range. By replacing the first tie rods 601 and the second tie rods 602 with different lengths, or by selecting connecting sleeves 9 of different lengths, the steel-concrete composite column 1 can be quickly adapted without redesigning the entire tie rod 6, thus enhancing the versatility and reusability of the device. Tensile compensation can be achieved by adjusting the connecting sleeve 9 individually. When the connecting sleeve 9 is tightened, the relative distance between the first tie rods 601 and the second tie rods 602 shortens, increasing the tension of the tie rod 6 and simultaneously increasing the tensile force. There is no need to adjust the fastening blocks 10 on both sides, making the operation simple and convenient without affecting the alignment of the tie rod 6's axis.
[0018] In this embodiment, the surface of the lower self-balancing beam 3 is provided with a pressure compensation component that applies axial pressure to the steel-concrete composite column 1. The pressure compensation component includes a gear ring 11 coaxially and rotatably disposed on the surface of the lower self-balancing beam 3, a gear ring meshing with the gear ring 11, and a driving component 12 that drives the gear ring 11 to rotate. There are two driving components 12, which are symmetrically arranged about the horizontal axis of the lower self-balancing beam 3. Each driving component 12 is fixedly disposed on the surface of the lower self-balancing beam 3 by bolts. Each driving component 12 is a drive motor, and its output end meshes with the gear ring 11. There are four gear rings, which correspond one-to-one with the fastening blocks 10 on the second tie rod 602. Each gear ring is coaxially sleeved and fixed on the outer ring surface of the corresponding fastening block 10. A first displacement sensor for detecting the inside of the steel-concrete composite column 1 is provided at the center of the first circular plate 4, and a second displacement sensor for detecting the inside of the steel-concrete composite column 1 is provided at the center of the second circular plate 5. The first displacement sensor and the second displacement sensor can be grating displacement meters (the first displacement sensor and the second displacement sensor are not shown in the figure).
[0019] As shown in the figure, when the pressure exerted by the pressure member 8 on the concrete inside the steel tube concrete column 1 is no longer applied and the force is transferred to the tie rod 6, the core concrete inside will undergo slow plastic deformation (creep), which will reduce the tension of the tie rod 6 and decrease the tension. This will cause the first circular plate 4 to produce a slight displacement, which can be detected by the first displacement sensor and the second displacement sensor (of course, creep can be double-verified by combining the first force sensor 7 on each tie rod 6). At this time, we need to perform pressure compensation on the core concrete. We start each drive member 12 and drive the gear ring 11 to rotate. The gear ring 11 drives each fastening block 10 to rotate through the gear ring, so that the fastening block 10 abuts against the self-balancing beam and applies a compensating force to it, so that the tension transferred to the tie rod 6 always maintains the preset value. This is to simulate the state of the core concrete bearing a continuous and stable additional axial force from the upper column under real conditions (it will not decrease on its own due to the deformation of the core concrete), so as to ensure the accuracy and authenticity of the experimental data. If the pressure on the core concrete is not compensated, the tension of the tie rod 6 will gradually be less than the preset "additional axial force of the upper column". The actual load borne by the core concrete deviates from the simulated target. The test becomes "the core concrete bears a gradually decreasing axial force" instead of "a continuous and stable axial force" in real engineering. The data on axial compression performance and deformation law obtained in the end cannot provide a reliable basis for building design.
[0020] In this embodiment, the connecting cylinder 9 includes a first sleeve 901, a tension sensor, and a second sleeve 902 arranged sequentially along a straight line. The two ends of the tension sensor are threadedly connected to the first sleeve 901 and the second sleeve 902 respectively and are coaxially arranged. The free end of the first sleeve 901 is threadedly connected to the corresponding first pull rod 601, and the free end of the second sleeve 902 is threadedly connected to the corresponding second pull rod 602.
[0021] Based on the original first force sensor 7, a tension sensor is added to form a redundant monitoring structure of main sensor (first force sensor 7) + auxiliary sensor (tension sensor), avoiding monitoring distortion caused by the failure or error of a single sensor. The tension sensor is connected in series between the first tie rod 601 and the second tie rod 602, and the tension sensor is rigidly connected to the first tie rod 601 and the second tie rod 602 through the first sleeve 901 and the second sleeve 902, ensuring that the direct transmission of force completely coincides with the detection path, which greatly reduces the monitoring error and improves the response speed. It can capture the small tension fluctuations of the tie rod 6 in real time (such as the slight tension attenuation in the early stage of core concrete creep), providing high-frequency and reliable real-time data support for the precise control of the pressure compensation component.
[0022] In this embodiment, the loading assembly further includes a lower loading stool 15 coaxial with the steel tube concrete column 1. A second force sensor 17 is coaxially provided between the distribution beam 13 and the output end of the pressure member 8. The lower loading stool 15 is disposed between the lower self-balancing beam 3 and the base 16, and adjacent surfaces abut against each other.
[0023] As shown in the figure, the second force sensor 17 can monitor the axial force applied to the steel-concrete composite column 1 by the pressure component in real time. The upper loading stool 14, the cross distribution beam 13, and the lower loading stool 15 can effectively optimize the uniformity of the force transmission applied by the pressure component, ensure the stability of the device, and adapt to the loading equipment and test scenario. The three perform their respective functions and cooperate with each other to ensure that the force is without deviation and diffusion throughout the entire process from the output of the pressure component to the core concrete bearing the force, and completely avoid the steel pipe wall being stressed.
[0024] In this embodiment, the tension sensors are all fiber Bragg grating strain gauges. Each of the first pull rods 601 has multiple fiber Bragg grating strain gauges on its surface, and each fiber Bragg grating strain gauge is evenly spaced around the axis of the first pull rod 601. Each fiber Bragg grating strain gauge is located near the center of the length of the first pull rod 601.
[0025] The fiber optic strain gauge serves as the main sensor, forming a dual redundancy structure of "high-precision main monitoring + direct force transmission auxiliary monitoring" with the series-connected tensile sensor (auxiliary sensor) inside the connecting cylinder 9. Furthermore, the design of multiple fiber optic strain gauges can effectively avoid measurement errors caused by single strain gauges due to misalignment of the bonding position or uneven local stress in the tie rod, and can also avoid monitoring deviations caused by local stress concentration or individual sensor differences, further improving the reliability of the dual redundancy monitoring system.
[0026] A test loading method considering the influence of additional axial force on the upper column, applied in the aforementioned test loading device considering the influence of additional axial force on the upper column, includes the following implementation steps: Step S1: Preparation before the test; Place the lower loading stool 15 in the preset position and adjust it to a horizontal state. Install each component in the designated position from bottom to top, while ensuring that the lower loading stool 15, the second circular plate 5, the lower self-balancing beam 3, the steel pipe concrete column 1, the first circular plate 4, and the upper self-balancing beam 2 are all coaxially set. Then install each tie rod 6 and the connecting cylinder 9, and initially fix them between the upper self-balancing beam 2 and the lower self-balancing beam 3. Finally, install each fiber optic strain gauge and connect each sensor (first force sensor 7, tension sensor, second force sensor 17, first displacement sensor, second displacement sensor) to the data acquisition instrument and the main control unit. Step S2, System Calibration and Preloading; Start the pressurizing component 8 and apply preloading to the specified pressure at the preset loading rate. Keep the load stable for a period of time. During this process, observe the connection status of each component to see if there is any looseness or deformation, and whether there are any abnormal fluctuations in the signals of each sensor. If any abnormality occurs, unload and adjust immediately. If there is no abnormality, unload to zero at the same rate to complete the preloading. Step S3: Formal Loading and Force Locking; Start the pressurizing component 8 and slowly apply the load to the preset target. During the loading process, collect data from each sensor in real time and monitor the tension balance of each tie rod 6 to ensure uniform stress on the core concrete. Keep the pressurizing component 8 stably applying the load. After the core concrete deformation stabilizes, tighten the fastening blocks 10 on each first tie rod 601 and second tie rod 602, as well as the connecting cylinder 9, to keep the tie rod 6 taut. Monitor the tension of the tie rod 6 in real time. After confirming that the tension of the tie rod 6 is stable and that there are no abnormalities in each component, control the pressurizing component 8 to slowly unload the pressure until the pressurizing component 8 is completely separated from the upper self-balancing beam 2, completing the force conversion from the external force of the pressurizing component 8 to the self-balancing tension of the tie rod 6. Then, the distribution beam 13 and the upper loading stool 14 are installed, and the upper loading stool 14 is fixedly connected to the corresponding loading beam 18 by bolts and nuts. This simulates the situation in a super high-rise building where the beams transfer the load of this floor to the bottom column. The pressure component 8 is activated again, and the vertical load applied by the pressure component 8 is transferred to the steel pipe wall of the steel-concrete composite column 1 through the loading stool 14 and the loading beam 18 until the steel-concrete composite column 1 is damaged. Step S4: Test monitoring and tensile deviation compensation; The data acquisition instrument synchronously acquires data from each of the first force sensor 7, the first displacement sensor, the second displacement sensor, and the tension sensor in real time. Simultaneously, the main control unit calculates the difference between the first displacement sensor and the second displacement sensor in real time. With core concrete creep value; when When the deviation exceeds a preset threshold, the main control unit initiates automatic compensation, calculates the compensation torque based on the direction of the deviation, controls the drive component 12 to simultaneously tighten or loosen the fastening blocks 10 on each pair of tie screws 6, and provides real-time feedback of the tension value through the tension sensor until... Within the specified range; Step S5: When the steel-concrete composite column 1 is damaged, the control drive component 12 simultaneously loosens the fastening blocks 10 of each tie rod 6, slowly releasing the tension of the tie rod 6 until the tension drops to zero. Then, each component is removed in sequence, the experimental site is cleaned, and the experimental data is saved.
[0027] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.
Claims
1. A test loading device considering the influence of additional axial force on an upper column, comprising a concrete-filled steel tube column (1) and a loading assembly for applying axial force to it, characterized in that, The outer surface of the steel-concrete composite column (1) is provided with multiple loading beams (18) spaced apart circumferentially. An upper self-balancing beam (2) and a lower self-balancing beam (3) are respectively provided at both ends of the steel-concrete composite column (1). A first circular plate (4) is provided between the steel-concrete composite column (1) and the upper self-balancing beam (2), and the diameter of the first circular plate (4) is smaller than that of the steel-concrete composite column (1). A second circular plate (5) is provided between the steel-concrete composite column (1) and the lower self-balancing beam (3), and the diameter of the second circular plate (5) is larger than that of the steel-concrete composite column (1). The steel-concrete composite column (1), the upper self-balancing beam (2), the lower self-balancing beam (3), the first circular plate (4), and the second circular plate (5) are all coaxially arranged and abut against each other. The surfaces of the upper self-balancing beam (2) and the lower self-balancing beam (3) are both open. The system has vertical through holes, and a tie rod (6) is connected between any two corresponding through holes. Each tie rod (6) is spaced around the steel pipe concrete column (1) in a circumferential manner, and a first force sensor (7) is provided on the surface of each tie rod (6). The loading assembly includes a base (16) and a pressure member (8) set above it. The pressure member (8) is set vertically and is coaxial with the steel pipe concrete column (1). The steel pipe concrete column (1) is set directly below the pressure member (8), and the lower self-balancing beam (3) abuts against the surface of the base (16). The output end of the pressure member (8) is connected to a distribution beam (13) coaxial with it, and the lower surface of the distribution beam (13) is provided with an upper loading stool (14) that abuts against the upper surface of each loading beam (18).
2. The test loading device considering the influence of the additional axial force of the upper column according to claim 1, characterized in that: Each of the aforementioned tie rods (6) includes a first tie rod (601) and a second tie rod (602) detachably connected thereto. The first tie rod (601) and the second tie rod (602) are spaced apart vertically and coaxially arranged. Both ends of the first tie rod (601) and the second tie rod (602) are threaded. The adjacent ends of the first tie rod (601) and the second tie rod (602) are threadedly connected to a connecting cylinder (9). The two ends that are far apart from each other pass through the corresponding upper self-balancing beam (2) and lower self-balancing beam (3) and are threadedly connected to a fastening block (10). The outer surface of each first tie rod (601) is provided with a first force sensor (7).
3. The test loading device considering the influence of the additional axial force of the upper column according to claim 2, characterized in that: The surface of the lower self-balancing beam (3) is provided with a pressure compensation component that applies axial pressure to the steel-concrete composite column (1). The pressure compensation component includes a gear ring (11) coaxially and rotatably disposed on the surface of the lower self-balancing beam (3), a gear ring meshing with the gear ring (11), and a drive member (12) that drives the gear ring (11) to rotate. The drive member (12) is fixedly disposed on the surface of the lower self-balancing beam (3). The gear ring is provided with multiple pieces and corresponds one-to-one with the fastening block (10) on the second tie rod (602). Each gear ring is coaxially sleeved and fixed on the outer ring surface of the corresponding fastening block (10). The center of the first circular plate (4) is provided with a first displacement sensor for detecting the inside of the steel-concrete composite column (1), and the center of the second circular plate (5) is provided with a second displacement sensor for detecting the inside of the steel-concrete composite column (1).
4. The test loading device considering the influence of the additional axial force of the upper column according to claim 3, characterized in that: The connecting cylinder (9) includes a first sleeve (901), a tension sensor, and a second sleeve (902) arranged sequentially along a straight line. The two ends of the tension sensor are threadedly connected to the first sleeve (901) and the second sleeve (902) respectively and are coaxially arranged. The free end of the first sleeve (901) is threadedly connected to the corresponding first pull rod (601), and the free end of the second sleeve (902) is threadedly connected to the corresponding second pull rod (602).
5. The test loading device considering the influence of the additional axial force of the upper column according to claim 4, characterized in that: The tension sensors all use fiber Bragg grating strain gauges. Each of the first pull rods (601) has multiple fiber Bragg grating strain gauges on its surface. The fiber Bragg grating strain gauges are evenly spaced around the axis of the first pull rod (601) and are located near the center of the length of the first pull rod (601).
6. A test loading method considering the influence of additional axial force on upper columns, applied in the test loading device considering the influence of additional axial force on upper columns as described in claims 1-5, characterized in that: The implementation steps include the following: Step S1, Preparatory work before the test: Place the lower loading stool (15) in the preset position and adjust it to a horizontal state. Install each component in the designated position from bottom to top, while ensuring that the lower loading stool (15), the second circular plate (5), the lower self-balancing beam (3), the steel pipe concrete column (1), the first circular plate (4) and the upper self-balancing beam (2) are all coaxially set. Then install each tie rod (6) and the connecting cylinder (9) and fix them between the upper self-balancing beam (2) and the lower self-balancing beam (3). Finally, install each fiber optic strain gauge and connect each sensor to the data acquisition instrument and the main control unit. Step S2, System calibration and preloading; Start the pressurizing component (8), apply preloading to the specified pressure at the preset loading rate, keep the load stable for a period of time, and observe the connection status of each component at all times to see if there is any looseness or deformation, and whether there is any abnormal fluctuation in the signal of each sensor; If any abnormality occurs, unload and adjust immediately; if there is no abnormality, unload to zero at the same rate to complete the preloading. Step S3: Formal loading and force locking; Start the pressurizing component (8) and slowly apply the load to the preset target. During the loading process, collect data from each sensor in real time to monitor the tension balance of each tie rod (6) and ensure that the core concrete is subjected to uniform force; Keep the pressurizing component (8) stable in applying the load. After the core concrete deformation stabilizes, tighten the fastening blocks (10) on each first tie rod (601) and second tie rod (602) and the connecting cylinder (9) to make the tie rod (6) taut. The tension of the tie rod (6) is monitored in real time. After confirming that the tension of the tie rod (6) is stable and that there are no abnormalities in any component, the pressure component (8) is controlled to slowly unload the pressure until the pressure component (8) is completely separated from the upper self-balancing beam (2), thus completing the force conversion from the external force of the pressure component (8) to the self-balancing tension of the tie rod (6). Then the distribution beam (13) and the upper loading stool (14) are installed, the pressure component (8) is restarted, and the load on the loading beam (18) is slowly applied to the preset target while the experimental data is collected. Step S4: Test monitoring and tensile deviation compensation; The data acquisition instrument synchronously acquires data from each of the first force sensor (7), first displacement sensor, second displacement sensor, and tensile sensor in real time. At the same time, the main control unit calculates the difference between the first displacement sensor and the second displacement sensor in real time. With core concrete creep value; when When the deviation exceeds a preset threshold, the main control unit initiates automatic compensation, calculates the compensation torque based on the direction of the deviation, and controls the drive component (12) to simultaneously tighten or loosen the fastening blocks (10) of each pair of pull screws (6) through gear transmission. The tensile force value is fed back in real time through the tension sensor until the force reaches the target value. Within the specified range; Step S5: When the steel-concrete composite column (1) is damaged, the control drive (12) simultaneously loosens the fastening blocks (10) of each tie rod (6), slowly releasing the tension of the tie rod (6) until the tension drops to zero. Then, each component is removed in sequence, the experimental site is cleaned, and the experimental data is saved.