Axial compression performance testing device for hollow interlayer steel pipe concrete member

Abstract

The utility model discloses an axial compression performance testing device for a hollow sandwich steel tube concrete member, and belongs to the field of performance testing of hollow sandwich steel tube concrete specimens. When the total cross section is pressed, the upper end face of the hollow sandwich steel tube concrete member is attached to the lower end face of an upper cross beam, and the lower end face of the hollow sandwich steel tube concrete member is clamped on the upper end face of a base; the two annular loading blocks coincide with the center of the upper end and the center of the lower end of the hollow sandwich steel tube concrete member and then are attached to the center of the upper end and the center of the lower end of the hollow sandwich steel tube concrete member respectively, and the inner diameter of the annular loading blocks is larger than or equal to the outer diameter of an inner steel tube of the hollow sandwich steel tube concrete member. Output shafts of the hydraulic jacks directly face the lower end face of the base; the strain gauges are fixed on the outer walls of the inner and outer steel pipes, and the pressure sensor and the strain gauges are connected with the multi-channel strain acquisition instrument and then connected with the computer, so that the axial pressure load can be effectively applied to the interlayer concrete or the total cross section, and the axial pressure performance of the hollow interlayer steel pipe concrete member is conveniently tested.

Description

Technical Field

[0001] The utility model belongs to the field of performance testing of hollow sandwich steel tube concrete test pieces, and in particular relates to an axial compression performance testing device for hollow sandwich steel tube concrete components. Background Art

[0002] Concrete-filled steel tube components with hollow sandwich structures offer advantages such as light weight, expanded cross-sections, and high strength, meeting the requirements of transmission towers. In actual construction, transmission towers are subject not only to horizontal loads such as wind and conductor tension, but also to vertical loads from snow and ice accumulation, as well as torsional loads from broken conductors. This subjects the poles to a combined state of compression, bending, and torsion. Exploring the axial compression performance of concrete-filled steel tube components with hollow sandwich structures is fundamental to analyzing their combined load states.

[0003] The study of the axial compression performance of hollow sandwich steel tube concrete components usually includes two cases: 1) the steel tube and the sandwich concrete bear axial loads at the same time; 2) the steel tube is only subjected to the lateral pressure generated by the expansion of concrete, that is, only the sandwich concrete is loaded to form steel tube confined concrete.

[0004] There are currently reports on tests of the compressive properties of concrete, such as the Chinese invention patent with application number 202111016222.9, entitled "A Concrete High-Temperature Compressive Performance Test Device and Its Test Method". The test device includes a loading device, a heating device and a deformation collection device; the loading device includes a base and an upper pressure plate, and a plurality of columns are fixedly connected to the base. The upper pressure plate is connected to the base through the columns, and the columns pass through the upper pressure plate and are threadedly connected to the nuts; the concrete specimen is placed between the base and the upper pressure plate, and the nuts are tightened so that the upper pressure plate applies pressure to the concrete specimen along the columns; the deformation collection device includes a strain gauge and a strain collector, and the strain gauge includes an axial strain gauge and a circumferential strain gauge; on the outer side of each column and the outer side of the concrete specimen Two axial strain gauges are installed on each side; the two axial strain gauges on the concrete specimen are symmetrically distributed about its axis and located on a cross section passing through the midpoint of the axis; the two axial strain gauges on the column are symmetrically distributed about its axis and located on a cross section passing through the midpoint of its axis; two circumferential strain gauges are also installed on the outer surface of the concrete specimen, symmetrically distributed about its axis, located on a cross section passing through the midpoint of the concrete specimen axis and staggered 90 degrees with the two axial strain gauges in the circumferential direction of the concrete specimen; the loading device is placed inside the heating device to heat the concrete specimen, and the strain acquisition instrument located outside the heating device is electrically connected to multiple strain gauges to collect strain data from the strain gauges. However, this test device only tests the compressive performance of concrete, and specifically at high temperatures. Its structure and specific process are not suitable for testing the axial compression performance of hollow sandwich steel tube concrete components. Utility Model Content

[0005] In response to the problems existing in the prior art, the utility model provides an axial compression performance testing device for hollow sandwich steel tube concrete components, which can effectively apply the axial compression load not only to the sandwich concrete, but also to the entire cross-section, thereby realizing the testing of the compression performance of only the concrete and the entire cross-section.

[0006] The utility model is realized through the following technical solutions:

[0007] A device for testing the axial compression performance of a hollow sandwich steel tube concrete-filled component comprises an upper crossbeam, a hydraulic jack, and a data acquisition unit. The hollow sandwich steel tube concrete-filled component is cylindrical, and a plurality of vertically spaced columns are fixedly connected to the upper crossbeam. Horizontally distributed bases are slidably provided on the lower halves of all the columns.

[0008] When the entire cross-section of the hollow sandwich steel tube concrete-filled component is under pressure, the upper end face of the hollow sandwich steel tube concrete-filled component is fitted with the lower end face of the upper crossbeam, and the lower end face of the hollow sandwich steel tube concrete-filled component is supported on the upper end face of the base. When only the concrete in the hollow sandwich steel tube concrete-filled component is under pressure, the component further comprises two annular loading blocks, which are respectively fitted with the upper and lower end centers of the hollow sandwich steel tube concrete-filled component after being coincident with each other. The inner diameter of the annular loading blocks is greater than or equal to the outer diameter of the inner steel tube of the hollow sandwich steel tube concrete-filled component. The lower end face of the upper crossbeam is fitted with the upper end face of the annular loading block located at the upper end, and the lower end face of the annular loading block located at the lower end is supported on the upper end face of the base. The output shaft of the hydraulic jack faces the lower end face of the base.

[0009] The data acquisition unit includes a pressure sensor, a multi-channel strain acquisition instrument and several strain gauges. The pressure sensor is fixed to the upper end surface of the base, and all the strain gauges are respectively fixed on the outer walls of the inner steel tube and the outer steel tube in the hollow sandwich steel tube concrete component. The output ends of the pressure sensor and all the strain gauges are connected to the input end of the multi-channel strain acquisition instrument, and the output end of the multi-channel strain acquisition instrument is connected to a computer.

[0010] The further improvement of the present invention is:

[0011] All strain gauges are divided into several groups, and each group of strain gauges is respectively fixed on the outer wall of the inner steel pipe and the outer steel pipe with the same cross section in the hollow sandwich steel tube concrete component after being aligned.

[0012] It also includes a passage bearing block, the center of which is provided with a through hole, and the upper end surface and the lower end surface of the passage bearing block are both provided with grooves communicating with the through hole and communicating with both sides of the passage bearing block;

[0013] When the entire cross-section of the hollow sandwich steel tube concrete component is under pressure, the upper end surface of the passage bearing block is in contact with the lower end surface of the upper crossbeam, the upper end surface of the hollow sandwich steel tube concrete component is in contact with the lower end surface of the passage bearing block, and the center of the passage bearing block coincides with the center of the hollow sandwich steel tube concrete component;

[0014] When only the concrete in the hollow sandwich steel tube concrete member is under pressure, the lower end surface of the passage bearing block is in contact with the upper end surface of the annular loading block at the upper end, the upper end surface of the passage bearing block is in contact with the lower end surface of the upper crossbeam, and the centers of the passage bearing block and the annular loading block at the upper end coincide with each other;

[0015] When the entire cross-section of the hollow sandwich steel tube concrete-filled component is under pressure, the strain gauge data lines of all strain gauges fixed on the inner steel tube of the hollow sandwich steel tube concrete-filled component are sequentially passed inwardly through the groove located on the lower end surface, upwardly through the through hole, and outwardly through the groove located on the upper end surface to be connected to the input end of the multi-channel strain collector, and the strain gauge data lines of all strain gauges fixed on the outer steel tube of the hollow sandwich steel tube concrete-filled component are passed outwardly through the groove located on the lower end surface to be connected to the input end of the multi-channel strain collector;

[0016] When only the concrete in the hollow sandwich steel tube concrete component is under pressure, the strain gauge data lines on all the strain gauges fixed on the inner steel tube of the hollow sandwich steel tube concrete component are sequentially connected to the input end of the multi-channel strain collector by passing obliquely inward through the interior of the annular loading block, upward through the through hole, and outward through the groove located on the upper end surface; the strain gauge data lines on all the strain gauges fixed on the outer steel tube of the hollow sandwich steel tube concrete component are connected to the input end of the multi-channel strain collector by passing upward and backward outward through the groove located on the lower end surface.

[0017] Each group of strain gauges has eight, evenly distributed on the outer walls of the inner and outer steel pipes. Cross-shaped grooves are provided on the upper and lower end faces of the passage bearing block, and each branch groove of the groove corresponds to the corresponding strain gauge position.

[0018] The outer diameter of the annular loading block is equal to the inner diameter of the outer steel pipe of the hollow sandwich steel tube concrete component, and the inner diameter of the annular loading block is 2-5 mm larger than the outer diameter of the inner steel pipe of the hollow sandwich steel tube concrete component.

[0019] It also includes a hydraulic oil source and a controller, the input end of the controller is connected to the output end of the computer, the output end of the controller is connected to the control end of the hydraulic oil source, and the oil outlet of the hydraulic oil source is connected to the oil inlet of the hydraulic jack.

[0020] The input end of the controller is connected to the output end of the computer through a four-core wire, the output end of the controller is connected to the control end of the hydraulic oil source through a four-core wire, and the output end of the multi-channel strain collector is connected to the computer through a four-core wire.

[0021] The oil outlet of the hydraulic oil source is communicated with the oil inlet of the hydraulic jack through an oil pipe.

[0022] The output shaft of the hydraulic jack is directly opposite to the center of the lower end surface of the base. When the entire cross-section of the hollow sandwich steel tube concrete-filled component is under pressure, the lower end surface of the hollow sandwich steel tube concrete-filled component is located at the center of the base. When only the concrete in the hollow sandwich steel tube concrete-filled component is under pressure, the lower end surface of the lower end annular loading block is located at the center of the base.

[0023] There are four upright posts, and the upper end of each upright post extends out from the four corners of the upper crossbeam and is fixed in the upper crossbeam through a nut.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] The utility model discloses an axial compression performance testing device for a hollow sandwich steel tube concrete-filled component. A column can fix a hollow sandwich steel tube concrete-filled component to be tested at its upper end face via an upper crossbeam. When the entire cross-section of the hollow sandwich steel tube concrete-filled component is under compression, the lower end face of the hollow sandwich steel tube concrete-filled component is supported on the upper end face of a base. The load of the output shaft of the hydraulic jack can be applied to the entire cross-section of the hollow sandwich steel tube concrete-filled component to be tested through the base. When only the concrete in the hollow sandwich steel tube concrete-filled component is under compression, two annular loading blocks are respectively aligned with the upper and lower end centers of the hollow sandwich steel tube concrete-filled component and then affixed. The inner diameter of the two annular loading blocks is greater than or equal to the outer diameter of the inner steel tube of the hollow sandwich steel tube concrete-filled component to be tested. The lower end face of the upper crossbeam affixes to the upper end face of the annular loading block located at the upper end, and the lower end face of the annular loading block located at the lower end is supported on the upper end face of the base. In this way, the load can be applied only to the concrete through the annular loading blocks, thereby realizing the test conditions of only concrete under compression and full cross-section compression. The pressure sensor detects the pressure applied by the hydraulic jack's output shaft. Strain gauges attached to the outer walls of the inner and outer steel tubes of the hollow sandwich steel tube concrete-filled component collect strain both when the concrete is compressed and when the entire cross-section is compressed. Data from the pressure sensor and all strain gauges is collected by a multi-channel strain gauge. A computer then converts the data into vertical force Pt and displacement St, respectively, to determine the axial compressive performance of the hollow sandwich steel tube concrete-filled component. This utility model effectively applies axial compressive loads to only the sandwich concrete or to the entire cross-section, facilitating testing of the axial compressive performance of hollow sandwich steel tube concrete-filled components.

[0026] Furthermore, a passage bearing block is arranged between the annular loading block at the upper end and the top upper cross beam. Through the grooves on the upper and lower end faces of the passage bearing block and the through hole in the center, the strain gauge data lines fixed on the outer wall of the outer steel pipe can be arranged while the strain gauge data lines on the outer wall of the inner steel pipe are also arranged outward, which facilitates the collection of strain data of the inner steel pipe and improves the measurement accuracy, thereby effectively overcoming the problem of difficult measurement of the strain of the inner steel pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of the hollow sandwich steel tube concrete specimen described in the present utility model;

[0028] Figure 2 This is a schematic structural diagram of the annular loading block in the present invention;

[0029] Figure 3 This is a schematic structural diagram of the passage bearing block in the present invention;

[0030] Figure 4 This is a schematic diagram of the connection structure of the hollow sandwich steel tube concrete specimen, the annular loading block and the passage bearing block of the utility model;

[0031] Figure 5 This is a structural diagram of the data acquisition system in this utility model

[0032] Figure 6 This is a three-dimensional diagram of the specimen loading unit in which only concrete is under pressure in the present invention.

[0033] Figure 7 This is a three-dimensional diagram of the loading unit of the specimen with the entire cross section under compression in the present invention.

[0034] Figure 8a This is the installation circuit diagram of the strain gauge of the concrete-only specimen loading unit in this utility model.

[0035] Figure 8b for Figure 8a Enlarged image in the dotted box.

[0036] Figure 9a This is the installation circuit diagram of the strain gauge of the full-section specimen loading unit in this utility model.

[0037] Figure 9b for Figure 9a Enlarged image in the dotted box.

[0038] Among them, 1 is the hollow sandwich steel tube concrete specimen to be tested, 2 is the annular loading block, 3 is the passage bearing block, 4 is the column, 5 is the upper beam, 6 is the base, 7 is the hydraulic oil source, 8 is the oil pipe, 9 is the four-core wire, 10 is the controller, 11 is the computer, 12 is the multi-channel strain acquisition instrument, 13 is the through hole, 14 is the strain gauge data cable, and 15 is the strain gauge. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it:

[0040] The utility model discloses a device for testing the axial compression performance of a hollow sandwich steel tube concrete component, which can realize the compression performance test of only concrete (the steel tube is only subjected to the lateral pressure generated by the expansion of concrete) and the full section (the steel tube and the sandwich concrete are subjected to the axial load at the same time). The structure of the hollow sandwich steel tube concrete specimen 1 to be tested is as follows: Figure 1 As shown, it is cylindrical and includes a component loading unit and a data acquisition unit. When only the concrete in the hollow sandwich steel tube concrete component is under pressure, the specimen loading unit includes Figure 2 The annular loading block 2, columns 4, upper crossbeam 5, base 6, and hydraulic oil source 7 are shown. When the entire cross-section of the hollow sandwich concrete-filled steel tubular member is under compression, the annular loading block 2 is absent. Multiple vertically spaced columns 4 are fixedly connected to the upper crossbeam 5, and horizontally distributed bases 6 are slidably mounted on the lower halves of all columns 4.

[0041] When the full section of the hollow sandwich steel tube concrete member is under compression, Figure 7 As shown, the upper end surface of the hollow sandwich steel tube concrete component is in contact with the lower end surface of the upper beam 5, and the lower end surface is supported on the upper end surface of the base 6. When only the concrete in the hollow sandwich steel tube concrete component is under pressure, Figure 4 In the test, two annular loading blocks 2 are respectively aligned with the upper and lower centers of the hollow sandwich steel tube concrete component to be tested and then fitted together. The inner diameter of the annular loading block 2 is greater than or equal to the outer diameter of the inner steel tube of the hollow sandwich steel tube concrete component. In this way, the load can be applied only to the concrete through the annular loading block 2. Figure 4 The outer diameter of the middle annular loading block 2 is equal to the inner diameter of the outer steel pipe of the concrete component, and the inner diameter is 2 to 5 mm larger than the outer diameter of the inner steel pipe of the hollow sandwich steel tube concrete component to be tested. Figure 6 As shown, the lower end face of the upper crossbeam 5 is fitted with the upper end face of the annular loading block 2 at the upper end, and the lower end face of the annular loading block 2 at the lower end is supported on the upper end face of the base 6, and the output shaft of the hydraulic jack is facing the lower end face of the base 6; there are four columns 4, and the upper end of each column 4 extends out from the four corners of the upper crossbeam 5, and is then fixed to the upper crossbeam 5 by a nut. Since this is just a schematic diagram, Figure 6 and Figure 7 The nut is not shown.

[0042] The data acquisition unit includes a pressure sensor for detecting the pressure of the hydraulic jack output shaft, a hydraulic oil source 7, a controller 10, a multi-channel strain acquisition instrument 12 and several strain gauges 15. The pressure sensor is fixed to the upper end surface of the base 6. The pressure sensor is installed on the lower surface of the base 6 with a gap between it and the jack output shaft. All strain gauges 15 are respectively fixed on the outer walls of the inner and outer steel pipes in the hollow sandwich steel tube concrete component. All strain gauges 15 are specifically divided into several groups. Each group of strain gauges 15 is fixed on the outer walls of the inner and outer steel pipes of the same cross-section in the concrete component after being aligned. The output ends of the pressure sensor and all strain gauges 15 are connected to the input end of the multi-channel strain acquisition instrument 12, as shown in FIG. Figure 5 As shown, the input end of the controller 10 is connected to the output end of the computer 11 via a four-core wire 9. The output end of the controller 10 is connected to the control end of the hydraulic oil source 7 via a four-core wire 9. The output end of the multi-channel strain gauge 12 is also connected to the computer 11 via a four-core wire 9. The oil outlet of the hydraulic oil source 7 is connected to the oil inlet of the hydraulic jack via an oil pipe 8.

[0043] As a preferred solution, the present invention also includes the following Figure 3 The passage bearing block 3 shown in the figure has a through hole 13 in the center with a diameter of 20mm. The upper and lower end surfaces are both provided with inverted triangular grooves that connect to the through hole 13 and are connected to both sides of the passage bearing block 3. When the entire cross section is under pressure, the upper end surface of the passage bearing block 3 fits with the lower end surface of the upper crossbeam 5, and the upper end surface of the hollow sandwich steel tube concrete component fits with the lower end surface of the passage bearing block 3. The passage bearing block 3 and the center of the hollow sandwich steel tube concrete component coincide. At this time, Figure 9a and Figure 9b As shown, the strain gauge data lines 14 of all the strain gauges 15 fixed on the inner steel pipe can be sequentially connected inwardly through the grooves on the lower end surface, upwardly through the through-holes 13, and outwardly through the grooves on the upper end surface to connect to the input end of the multi-channel strain collector 12. The strain gauge data lines 14 of all the strain gauges 15 fixed on the outer steel pipe can be connected outwardly through the grooves on the lower end surface to connect to the input end of the multi-channel strain collector 12, thereby facilitating wiring and data collection. When only the concrete in the hollow sandwich steel tube concrete component is under pressure, as shown in FIG. Figure 4 As shown, the lower end surface of the passage bearing block 3 is in contact with the upper end surface of the annular loading block 2 at the upper end, and the upper end surface of the passage bearing block 3 is in contact with the lower end surface of the upper crossbeam 5, and the center of the passage bearing block 3 and the annular loading block 2 at the upper end coincide with each other. Figure 8a and Figure 8bAs shown, the strain gauge data cables 14 of all strain gauges 15 fixed to the inner steel pipe can be sequentially routed diagonally inward through the interior of the annular loading block 2, upward through the through-hole 13, and outward through the groove on the upper end surface to connect to the input of the multi-channel strain collector 12. The strain gauge data cables 14 of all strain gauges 15 fixed to the outer steel pipe can be routed upward and then outward through the groove on the lower end surface to connect to the input of the multi-channel strain collector 12, thereby facilitating wiring and data collection. This utility model solves the problem of difficult strain measurement in the inner steel pipe by using the passage bearing block 3, achieving a smaller error.

[0044] In addition, each group of strain gauges 15 has 8, 4 of which are evenly distributed on the outer wall of the outer steel pipe, and the other 4 are evenly distributed on the outer wall of the inner steel pipe. The upper and lower end faces of the passage bearing block 3 are specifically provided with cross-shaped grooves, and each branch groove of the groove corresponds to the position of the corresponding strain gauge 15.

[0045] In the present invention, when only the concrete in the hollow sandwich steel tube concrete component is under pressure, the annular loading block 2, the passage bearing block 3, the upper crossbeam 5, the base 6 and the hollow sandwich steel tube concrete specimen 1 to be tested are placed in a centered manner (with the centers coinciding); when the entire cross section is under pressure, the passage bearing block 3, the upper crossbeam 5, the base 6 and the hollow sandwich steel tube concrete specimen 1 to be tested are placed in a centered manner, and the output shaft of the hydraulic jack is facing the center of the bottom of the base 6, so that the hollow sandwich steel tube concrete specimen 1 to be tested (or the annular loading block 2), the passage bearing block 3 and the output shaft of the hydraulic jack are on the same vertical line, and the hydraulic jack applies the load to the hollow sandwich steel tube concrete specimen to be tested through the base 6; during vertical loading, the column 4 fixes the hollow sandwich steel tube concrete specimen 1 to be tested through the upper crossbeam 5.

[0046] In the present invention, the hollow sandwich steel tube concrete specimen 1 to be tested does not have an annular loading block 2 above or below. The load can be applied to the entire cross-section of the hollow sandwich steel tube concrete specimen 1 to be tested. The top surface of the hollow sandwich steel tube concrete specimen 1 to be tested directly contacts the bottom of the passage bearing block 3, and the hollow sandwich steel tube concrete specimen 1 to be tested is directly placed on the base 6. When manufacturing the hollow sandwich steel tube concrete specimen 1 to be tested, the inner steel tube is first welded to a lower end plate. Four strain gauges 15 are attached to each cross-section of the inner steel tube. The outer wall of the inner steel tube can be polished to increase the stability of the bond. The strain gauge data line 14 at the other end is placed upward. The outer steel tube is then concentrically placed on the lower end plate and welded. Concrete is poured into the inner and outer steel tube sandwich. Finally, the lower end plate is knocked off, and the strain gauges 15 are attached to the outer steel tube in the same manner.

[0047] The utility model discloses a device for testing the axial compression performance of a hollow sandwich steel tube concrete component. The specific working process is as follows:

[0048] Step 1: When only the concrete in the hollow sandwich steel tube concrete-filled component is under pressure, install the annular loading block 2, the passage bearing block 3, the base 6, and the hollow sandwich steel tube concrete-filled component 1 to be tested. When the entire cross-section is under pressure, install the passage bearing block 3, the base 6, and the hollow sandwich steel tube concrete-filled component 1 to be tested.

[0049] Step 2: Control the working state of the hydraulic oil source 7 through the computer 11 and the controller 10, adjust the hydraulic jack to return the stroke of the base 6 to the initial position, and connect the hydraulic oil source 7, the controller 10, the multi-channel strain gauge 12 and the computer 11 through the four-core wire 9;

[0050] Step 3: When testing is required, a corresponding vertical force is applied by a hydraulic jack until the specimen is destroyed, and the vertical force Pt and displacement St during the test are collected by a computer 11 and a multi-channel strain collector 12; based on the vertical force Pt and the vertical displacement St at the vertical force action point recorded during the test, a load-displacement curve of the hollow sandwich steel tube concrete specimen is drawn with only the concrete under compression or the entire cross-section under compression.

[0051] By analyzing the load-displacement curve, it is possible to calculate the ultimate bearing capacity, determine the safety factor, and understand the strength and stiffness characteristics of hollow sandwich concrete-filled steel tube specimens. Furthermore, the curve can help predict the performance of structures under actual loads and be used in failure criteria and seismic analysis in design.

Claims

1. A device for testing the axial compression performance of hollow sandwich steel tube concrete components, characterized in that: It comprises an upper crossbeam (5), a hydraulic jack and a data acquisition unit, wherein the hollow sandwich steel tube concrete component is cylindrical, a plurality of vertically distributed columns (4) are fixedly connected to the upper crossbeam (5), and a horizontally distributed base (6) is slidably provided on the lower half of all the columns (4); When the entire cross section of the hollow sandwich steel tube concrete component is under pressure, the upper end face of the hollow sandwich steel tube concrete component is fitted with the lower end face of the upper crossbeam (5), and the lower end face of the hollow sandwich steel tube concrete component is supported on the upper end face of the base (6). When only the concrete in the hollow sandwich steel tube concrete component is under pressure, the component further includes two annular loading blocks (2), which are respectively fitted after coinciding with the upper and lower end centers of the hollow sandwich steel tube concrete component. The inner diameter of the annular loading block (2) is greater than or equal to the outer diameter of the inner steel pipe of the hollow sandwich steel tube concrete component. The lower end face of the upper crossbeam (5) is fitted with the upper end face of the annular loading block (2) at the upper end, and the lower end face of the annular loading block (2) at the lower end is supported on the upper end face of the base (6). The output shaft of the hydraulic jack faces the lower end face of the base (6). The data acquisition unit includes a pressure sensor, a multi-channel strain acquisition instrument (12) and a plurality of strain gauges (15). The pressure sensor is fixed to the upper end surface of the base (6). All the strain gauges (15) are respectively fixed on the outer walls of the inner steel pipe and the outer steel pipe in the hollow sandwich steel tube concrete component. The output ends of the pressure sensor and all the strain gauges (15) are connected to the input end of the multi-channel strain acquisition instrument (12). The output end of the multi-channel strain acquisition instrument (12) is connected to the computer (11).

2. The axial compression performance testing device for hollow sandwich steel tube concrete components according to claim 1 is characterized in that: All strain gauges (15) are divided into several groups, and each group of strain gauges (15) is respectively fixed on the outer walls of the inner steel pipe and the outer steel pipe of the same cross section in the hollow sandwich steel tube concrete component after being aligned.

3. The axial compression performance testing device for hollow sandwich steel tube concrete components according to claim 2, characterized in that: It also includes a passage bearing block (3), a through hole (13) is provided at the center of the passage bearing block (3), and grooves communicating with the through hole (13) and with both sides of the passage bearing block (3) are provided on the upper end surface and the lower end surface of the passage bearing block (3); When the entire cross section of the hollow sandwich steel tube concrete component is under pressure, the upper end surface of the passage bearing block (3) fits in with the lower end surface of the upper crossbeam (5), the upper end surface of the hollow sandwich steel tube concrete component fits in with the lower end surface of the passage bearing block (3), and the passage bearing block (3) coincides with the center of the hollow sandwich steel tube concrete component; When only the concrete in the hollow sandwich steel tube concrete member is under pressure, the lower end surface of the passage bearing block (3) fits in with the upper end surface of the annular loading block (2) located at the upper end, the upper end surface of the passage bearing block (3) fits in with the lower end surface of the upper crossbeam (5), and the centers of the passage bearing block (3) and the annular loading block (2) located at the upper end coincide with each other; When the entire cross section of the hollow sandwich steel tube concrete component is under pressure, the strain gauge data lines (14) on all the strain gauges (15) fixed on the inner steel tube of the hollow sandwich steel tube concrete component sequentially pass inwardly through the groove located on the lower end surface, upwardly through the through hole (13), and outwardly through the groove located on the upper end surface to be connected to the input end of the multi-channel strain acquisition instrument (12), and the strain gauge data lines (14) on all the strain gauges (15) fixed on the outer steel tube of the hollow sandwich steel tube concrete component pass outwardly through the groove located on the lower end surface to be connected to the input end of the multi-channel strain acquisition instrument (12); When only the concrete in the hollow sandwich steel tube concrete component is under pressure, the strain gauge data lines (14) on all the strain gauges (15) fixed on the inner steel tube of the hollow sandwich steel tube concrete component are sequentially connected to the input end of the multi-channel strain collector (12) by passing obliquely inward through the inside of the annular loading block (2), upward through the through hole (13), and outward through the groove located on the upper end surface, and the strain gauge data lines (14) on all the strain gauges (15) fixed on the outer steel tube of the hollow sandwich steel tube concrete component are connected to the input end of the multi-channel strain collector (12) by passing upward and backward and outward through the groove located on the lower end surface.

4. The axial compression performance testing device for hollow sandwich steel tube concrete components according to claim 3, characterized in that: Each group of strain gauges (15) has eight, evenly distributed on the outer walls of the inner steel pipe and the outer steel pipe. The upper end face and the lower end face of the passage bearing block (3) are both provided with a cross-shaped groove, and each branch groove of the groove corresponds to the position of a corresponding strain gauge (15).

5. The axial compression performance testing device for hollow sandwich steel tube concrete components according to claim 1, characterized in that: The outer diameter of the annular loading block (2) is equal to the inner diameter of the outer steel pipe of the hollow sandwich steel tube concrete component, and the inner diameter of the annular loading block (2) is 2 to 5 mm larger than the outer diameter of the inner steel pipe of the hollow sandwich steel tube concrete component.

6. The axial compression performance testing device for hollow sandwich steel tube concrete components according to claim 1, characterized in that: The invention also includes a hydraulic oil source (7) and a controller (10), wherein the input end of the controller (10) is connected to the output end of the computer (11), the output end of the controller (10) is connected to the control end of the hydraulic oil source (7), and the oil outlet of the hydraulic oil source (7) is communicated with the oil inlet of the hydraulic jack.

7. The axial compression performance testing device for hollow sandwich steel tube concrete members according to claim 6, characterized in that: The input end of the controller (10) is connected to the output end of the computer (11) through a four-core wire (9), the output end of the controller (10) is connected to the control end of the hydraulic oil source (7) through the four-core wire (9), and the output end of the multi-channel strain collector (12) is connected to the computer (11) through the four-core wire (9).

8. The axial compression performance testing device for hollow sandwich steel tube concrete members according to claim 6, characterized in that: The oil outlet of the hydraulic oil source (7) is connected to the oil inlet of the hydraulic jack through an oil pipe (8).

9. The axial compression performance testing device for hollow sandwich steel tube concrete components according to claim 1, characterized in that: The output shaft of the hydraulic jack is directly opposite to the center of the lower end surface of the base (6); when the entire cross-section of the hollow sandwich steel tube concrete component is under pressure, the lower end surface of the hollow sandwich steel tube concrete component is located at the center of the base (6); when only the concrete in the hollow sandwich steel tube concrete component is under pressure, the lower end surface of the lower end annular loading block (2) is located at the center of the base (6).

10. The axial compression performance testing device for hollow sandwich steel tube concrete components according to claim 1, characterized in that: There are four upright posts (4), and the upper end of each upright post (4) extends out from the four corners of the upper crossbeam (5) and is fixed in the upper crossbeam (5) through a nut.

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