Steel tube concrete composite column interface push-out test piece, mold and test piece manufacturing method

Abstract

The application discloses a kind of steel pipe concrete composite column interface push-out test piece, mould and test piece manufacturing method, belong to building structure experimental technical field.Test piece includes steel bottom plate, steel pipe, center tube concrete and peripheral concrete.Mould includes steel mould, positioning block, wood form, restraint clamp and rubber plug.Compared with traditional push-out test piece, after push-out test is carried out, steel pipe concrete and pipe outer reinforced concrete are consistent in height, unbonded steel pipe concrete composite column axial compression test can be carried out, material utilization is improved, in addition, traditional push-out test piece needs to be matched with at least 50mm thick middle opening hole steel plate support to carry out push-out test, the steel plate is heavy and material consumption is serious, moving steel plate is easy to cause personal injury, the application does not need steel plate support, and economic performance and test safety are significantly improved, reduce test workload.

Description

Technical Field

[0001] This invention belongs to the field of building structure experimental technology, specifically relating to a steel-concrete composite column interface ejection specimen, mold, and specimen preparation method. Background Technology

[0002] Steel-concrete composite columns are made of a centrally circular cross-section steel-concrete composite column and an outer steel-reinforced concrete column. Compared with ordinary reinforced concrete structures and steel-reinforced concrete structures, this type of structure can effectively improve the load-bearing capacity, ductility, fire resistance and seismic performance of the components, and reduce the cross-sectional size of the components. It has been applied in many high-rise and super high-rise buildings in China.

[0003] Whether the steel tube and concrete in a composite column can work together to give full play to the advantages of the composite structure is a major concern in the engineering community. The bond stress at the interface between the steel tube and the concrete outside the tube has a significant impact on the load distribution between the steel tube and the concrete outside the tube. Therefore, the study of the bond performance between the steel tube and the concrete in the steel tube-concrete composite column is one of the issues of great concern to our engineering community.

[0004] The interface push-out test of steel-concrete composite columns can effectively analyze the bond-slip relationship between the steel tube and the concrete outside the steel tube. However, the traditional push-out test of steel-concrete composite columns requires a steel plate support with a central hole of at least 50 mm thickness. However, after the test, the top of the specimen is pushed out, creating a height difference between the concrete inside and outside the steel tube, which makes it impossible to continue to study the mechanical properties of the composite column. The low recyclability of specimens and molds and poor economic benefits are also drawbacks that urgently need to be solved. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides a steel-concrete composite column interface ejection specimen, mold, and specimen fabrication method. It features prefabricated installation, simple specimen preparation, reusable specimens, recyclable molds, and good economic efficiency. It solves the problem that traditional specimens, after being ejected from the top, create a height difference between the concrete inside and outside the steel tube, making it impossible to continue research on the mechanical properties of the composite column.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A test specimen of a steel-concrete composite column interface, including

[0008] Steel base plate;

[0009] A steel pipe, which is vertically fixed to the upper surface of the steel base plate;

[0010] The central tube concrete is poured inside the steel pipe and is flush with the top surface of the steel pipe.

[0011] The outer concrete is poured to form the outer perimeter of the steel pipe. There is a sliding gap between the bottom surface of the outer concrete and the top surface of the steel base plate. The top surface of the outer concrete is higher than the top surface of the steel pipe. The height difference between the top surface of the outer concrete and the top surface of the steel pipe is the same as the sliding gap.

[0012] Preferably, a steel cage is embedded inside the outer concrete, and the steel cage is made of longitudinal bars and stirrups.

[0013] Preferably, the outer concrete has a rectangular cross-section perpendicular to its length.

[0014] Preferably, both the central cylinder concrete and the outer perimeter concrete are made of ordinary concrete, high-strength concrete, seawater sand concrete, adaptive concrete, or recycled aggregate concrete.

[0015] A mold designed for preparing the interface ejection specimen of the aforementioned steel-concrete composite column, the mold comprising:

[0016] A steel mold, which consists of a steel base plate and a steel pipe, is used as a component of a test specimen;

[0017] A positioning block, the positioning block being arranged on the upper surface of the steel base plate surrounding the steel pipe;

[0018] The wooden formwork consists of multiple side formworks and a bottom formwork. The side formworks are set around the steel pipe and sit on the positioning block. The bottom formworks are inserted into the steel pipe and sit on the positioning block. The bottom formworks and the side formworks are sealed together to form a space for pouring the outer concrete.

[0019] A constraint clamp is fixed to the top of the side template and used to compact and constrain the surrounding side templates;

[0020] A rubber plug passes through an opening in the middle of the constraint clamp and fits against the top surface of the steel pipe.

[0021] Preferably, the cross-section of the wooden template perpendicular to its length direction is rectangular.

[0022] Preferably, the constraint fixture consists of a cross-shaped steel plate and an L-shaped constraint platform disposed on the outer edge of the cross-shaped steel plate, wherein the L-shaped constraint platform and the top of the side template form a limiting fit relationship.

[0023] Preferably, the diameter of the rubber stopper is the same as the outer diameter of the steel pipe.

[0024] A method for preparing a test specimen of a steel-concrete composite column interface, wherein the mold is prefabricated in a factory for later use, and the method for preparing the test specimen includes:

[0025] S1. Place the steel pipe on the steel base plate, pour the central cylinder concrete into the steel pipe, and attach strain gauges to the outer wall of the steel pipe.

[0026] S2. Place the positioning blocks at the four corners of the steel base plate. Place the bottom formwork, which has been coated with concrete release agent, through the top of the steel pipe onto the positioning blocks. Place the tied steel cage through the top of the steel pipe onto the bottom formwork. Erect the side formwork on the positioning blocks around the steel cage. The side formwork, bottom formwork, and steel pipe together form a space for pouring the outer concrete. Fix the restraint clamps to the top of the side formwork. Insert the rubber plugs through the opening in the middle of the restraint clamps and fit them against the top surface of the steel pipe. Finally, pour the outer concrete.

[0027] S3. After the outer concrete has initially set, remove the restraint clamps and rubber plugs. After 24 hours, remove the positioning block, demold the side formwork and bottom formwork, and cure and level the test specimen.

[0028] Preferably, in step S2, an expansion gap is reserved at the joint of the wooden template, and sealant is applied.

[0029] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0030] The specimens of this invention can be applied to the experimental research on the interfacial performance of different component materials in composite structural members, especially for the push-out test between the circular tube and concrete in composite members. Research objects may include FRP tube-confined concrete members, steel tube-confined concrete members, FRP-steel composite confined concrete members, concrete composite members with embedded FRP tubes, concrete composite members with embedded steel tubes, and FRP-concrete-steel tube double-tube columns, etc. These composite columns leverage the performance advantages of each component material and the confined concrete, exhibiting excellent mechanical properties and durability. Studying the bond-slip relationship at the interface between the circular tube and concrete helps to understand the working failure mechanism of structural members, enabling better design and wider application of multi-component composite structural members.

[0031] This invention proposes a steel-concrete composite column interface push-out specimen. Compared with traditional push-out specimens, after the push-out test, the steel-concrete composite column and the reinforced concrete outside the tube are at the same height, which allows for unbonded steel-concrete composite column axial compression tests, improving material utilization. In addition, traditional push-out specimens require a steel plate support with a central hole of at least 50mm thickness to conduct the push-out test. This steel plate is heavy and consumes a lot of materials. Moving the steel plate can easily cause personnel injury. This invention eliminates the need for a steel plate support, significantly improving economic performance and test safety, and reducing the workload of the test. Attached Figure Description

[0032] Figure 1 A three-dimensional structural schematic diagram of the steel-concrete composite column interface ejection specimen of the present invention;

[0033] Figure 2 This is a schematic diagram of the front structure of the steel-concrete composite column interface ejection specimen of the present invention.

[0034] Figure 3 This is a three-dimensional structural diagram of the steel cage of the present invention;

[0035] Figure 4 This is a three-dimensional structural diagram of the mold of the present invention;

[0036] Figure 5 This is a partial three-dimensional structural schematic diagram of the mold of the present invention;

[0037] Figure 6 This is a three-dimensional structural diagram of the steel mold of the present invention;

[0038] Figure 7 This is a three-dimensional structural diagram of the positioning block of the present invention;

[0039] Figure 8 This is a three-dimensional structural diagram of the wooden template of the present invention;

[0040] Figure 9 This is a three-dimensional structural diagram of the constraint fixture of the present invention;

[0041] Figure 10 This is a top view of the constraint fixture of the present invention.

[0042] Figure 11 This is a three-dimensional structural diagram of the rubber stopper of the present invention;

[0043] Figure 12 This is a schematic diagram of the test structure of the specimen of the present invention;

[0044] Figure 13 for Figure 12 A top view of the centrally restrained steel plate structure;

[0045] Figure 14 for Figure 12 A top view of the structure of the steel clamp.

[0046] In the diagram, 1-steel mold; 11-steel pipe; 12-steel base plate; 2-positioning block; 3-reinforcing cage; 31-longitudinal reinforcement; 32-stirrup; 4-wooden formwork; 41-side formwork; 42-bottom formwork; 5-constraint clamp; 51-cross-shaped steel plate; 52-constraint platform; 53-opening; 6-central tube concrete; 7-outer concrete; 8-rubber plug; 9-constraint steel plate; 10-steel clamp. Detailed Implementation

[0047] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the accompanying drawings are for illustrative purposes only and should not be construed as limiting the present patent. For better illustration of this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable that some well-known structures and their descriptions may be omitted in the drawings for those skilled in the art. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present patent.

[0048] Example 1

[0049] like Figure 1-3 As shown, a steel pipe 11 concrete composite column interface ejection specimen includes a steel base plate 12, a steel pipe 11, a central tube concrete 6, and an outer concrete 7.

[0050] The steel pipe 11 is vertically fixed to the upper surface of the steel base plate 12. The diameter and height of the steel pipe 11 depend on the size of the specimen required for the experiment.

[0051] The central tube concrete 6 is poured inside the steel pipe 11 and is flush with the top surface of the steel pipe 11. The central tube concrete 6 is made of ordinary concrete, high-strength concrete, seawater sand concrete, adaptive concrete or recycled aggregate concrete.

[0052] The outer concrete 7 is poured to form the periphery of the steel pipe 11. There is a sliding gap between the bottom surface of the outer concrete 7 and the top surface of the steel base plate 12. The top surface of the outer concrete 7 is higher than the top surface of the steel pipe 11, and the height difference between the top surface of the outer concrete 7 and the top surface of the steel pipe 11 is the same as the sliding gap. The outer concrete 7 has a rectangular cross-section perpendicular to its length direction. The outer concrete 7 is made of ordinary concrete, high-strength concrete, seawater sand concrete, adaptive concrete, or recycled aggregate concrete.

[0053] The outer concrete 7 contains a steel cage 3, which is made of longitudinal bars 31 and stirrups 32 tied together according to the cross-sectional dimensions and the thickness of the protective layer. The cross-section of the steel cage 3 perpendicular to its length is rectangular.

[0054] Example 2

[0055] like Figure 4-11 As shown, a mold designed for preparing a test specimen for the interface of a steel pipe 11 concrete composite column includes a steel mold 1, a positioning block 2, a wooden template 4, a constraint clamp 5, and a rubber plug 8.

[0056] The steel mold 1 is welded from a steel base plate 12 and a steel pipe 11. The steel pipe 11 and the steel base plate 12 form an integral structure. The steel mold 1 is used as a component of the test specimen. The diameter and height of the steel pipe 11 depend on the size of the test specimen required for the experiment.

[0057] The positioning block 2 is a square positioning block 2, and a total of four are set up and arranged on the upper surface of the steel base plate 12 around the steel pipe 11. The height of the square positioning block 2 depends on the ejection length set in the ejection experiment.

[0058] The wooden formwork 4 consists of multiple side formworks 41 and a bottom formwork 42. The side formworks 41 are made of rectangular wooden boards, and the bottom formwork 42 is made of square wooden boards. The side formworks 41 are set around the steel pipe 11 and sit on the positioning block 2. The bottom formwork 42 has a through hole in the middle, and the bottom formwork 42 passes through the steel pipe 11 and sits on the positioning block 2. The bottom formwork 42 and the side formworks 41 are connected by screws to form a space for pouring the outer concrete 7.

[0059] The constraint clamp 5 is fixed to the top of the side template 41 and is used to compact and constrain the surrounding side template 41. The constraint clamp 5 consists of a cross-shaped steel plate 51 and an L-shaped constraint platform 52 set on the outer edge of the cross-shaped steel plate 51. The L-shaped constraint platform 52 and the upper part of the side template 41 form a limiting fit relationship. The cross-shaped steel plate 51 has an opening 53 in the center, and the size of the through hole depends on the outer diameter of the steel pipe 11.

[0060] The rubber plug 8 is a cylindrical rubber plug 8, which passes through the opening 53 in the middle of the constraint clamp 5 and fits against the top surface of the steel pipe 11. The diameter of the rubber plug 8 is the same as the outer diameter of the steel pipe 11.

[0061] Example 3

[0062] like Figure 12-14 As shown, a method for preparing a steel pipe 11 concrete composite column interface ejection specimen is described. A prefabricated mold is used in the factory. The steel base plate 12, steel pipe 11, and positioning block 2 are all made of Q345 steel. The steel base plate 12 has dimensions of 300*300*20mm; the steel pipe 11 has a diameter of 114mm, a height of 660mm, and a wall thickness of 6mm; the positioning block 2 has dimensions of 50*50*50mm; the rectangular side templates 41 have dimensions of 220*220mm, a thickness of 3mm, and a height of 660mm; the bottom template 42 has an opening 53 with a diameter of 114mm; the rubber plug 8 has a diameter of 114mm and a height of 100mm; the constraint clamp 5 has a central cutout of 114mm, a cross-shaped steel plate 51 with a width of 50mm and a thickness of 5mm, and a surrounding constraint platform 52 with a height of 50mm.

[0063] The methods for preparing the specimens include:

[0064] S1. Stand the steel pipe 11 on the steel base plate 12, pour the central cylinder concrete 6 into the steel pipe 11, and attach strain gauges to the outer wall of the steel pipe 11.

[0065] S2. Place the positioning block 2 at the four corners of the steel base plate 12. Place the bottom formwork 42, which has been coated with concrete release agent, through the top of the steel pipe 11 and onto the positioning block 2. Place the tied steel cage 3 through the top of the steel pipe 11 and onto the bottom formwork 42. Erect the side formwork 41 on the positioning block 2 around the steel cage 3. The side formwork 41, the bottom formwork 42 and the steel pipe 11 together form a space for pouring the outer concrete 7. Fix the restraint clamp 5 on the top of the side formwork 41. Insert the rubber plug 8 through the opening 53 in the middle of the restraint clamp 5 and attach it to the top surface of the steel pipe 11. Finally, pour the outer concrete 7.

[0066] In this design, expansion joints are reserved at the joints of the wooden formwork 4, and sealant is applied. The reinforcing cage 3 is placed between the steel pipe 11 and the wooden formwork 4, with its center coinciding with the center of the steel pipe 11, and a certain distance between its outer edge and the inside of the wooden formwork 4. When pouring the outer concrete 7, a vibrator is inserted between the wooden formwork 4 and the restraint clamps 5, and the concrete is vibrated while being poured. The mass ratio of the concrete components is as follows: slag: metakaolin: limestone: water glass: water: sand: 5-10mm crushed stone: 10-20mm crushed stone: steel fiber = 1: 0.125: 0.125: 0.496: 0.35: 1.837: 0.848: 2.025: 0.217.

[0067] S3. After the outer concrete 7 has initially set, remove the restraint clamp 5 and rubber plug 8. After 24 hours, remove the positioning block 2, demold the side formwork 41 and bottom formwork 42, and cure at room temperature for 48 hours. Then, use epoxy resin mortar to level the surface of the specimen.

[0068] After the specimen has been cured, the specimen is placed in the restraint steel plate 9, aligned with the center of the base plate of the pressure testing machine, and the strain gauge circuit is connected. The two ends of the component are restrained by steel clamps 10 to prevent the end face from being damaged first. The upper end of the steel plate is leveled and in contact with the top surface of the pressure testing machine, and the lower end of the concrete outside the pipe is leveled and in contact with the bottom surface of the pressure testing machine. The pressure testing machine applies vertical downward pressure to the steel pipe 11 concrete composite column until the bonding and slippage are completed.

[0069] According to the test results, in this embodiment, the ultimate axial compression bearing capacity of the steel tube 11 concrete composite column in the push-out test is 248kN; the ultimate axial compression bearing capacity of the unbonded steel tube 11 concrete composite column in the axial compression test is 2756kN.

[0070] Based on the description and accompanying drawings of this invention, those skilled in the art can readily manufacture or use the steel-concrete composite column interface ejection specimen, mold, and specimen preparation method of this invention, and can achieve the positive effects described in this invention.

[0071] Unless otherwise specified, in this invention, terms such as "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and 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, the terms used to describe orientation or positional relationships in this invention are for illustrative purposes only and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood in conjunction with the accompanying drawings and according to the specific circumstances.

[0072] Unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" in this invention 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 direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0073] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A steel-concrete composite column interface ejection specimen, characterized in that, include Steel base plate (12); A steel pipe (11) is vertically fixed to the upper surface of the steel base plate (12); The central tube concrete (6) is poured and formed inside the steel pipe (11) and is flush with the top surface of the steel pipe (11). And the outer concrete (7), which is poured to form the outer perimeter of the steel pipe (11). There is a sliding gap between the bottom surface of the outer concrete (7) and the top surface of the steel base plate (12). The top surface of the outer concrete (7) is higher than the top surface of the steel pipe (11). The height difference between the top surface of the outer concrete (7) and the top surface of the steel pipe (11) is the same as the sliding gap.

2. The steel-concrete composite column interface ejection specimen according to claim 1, characterized in that, The outer concrete (7) contains a steel cage (3), which is made of longitudinal bars (31) and stirrups (32).

3. The steel-concrete composite column interface ejection specimen according to claim 1, characterized in that, The outer concrete (7) has a rectangular cross-section perpendicular to its length direction.

4. The steel-concrete composite column interface ejection specimen according to claim 1, characterized in that, The central cylinder concrete (6) and the outer concrete (7) are both made of ordinary concrete, high-strength concrete, seawater sand concrete, adaptive concrete or recycled aggregate concrete.

5. A mold designed for preparing an interface ejection specimen of the steel-concrete composite column as described in claim 1, characterized in that, The mold includes: A steel mold (1) is composed of a steel base plate (12) and a steel pipe (11), and the steel mold (1) is used as a component of the test piece; Positioning block (2), the positioning block (2) is arranged on the upper surface of the steel base plate (12) around the steel pipe (11); Wooden formwork (4), the wooden formwork (4) is composed of multiple side formworks (41) and bottom formwork (42). The side formworks (41) are set around the steel pipe (11) and sit on the positioning block (2). The bottom formwork (42) is inserted into the steel pipe (11) and sits on the positioning block (2). The bottom formwork (42) and the side formworks (41) are sealed together to form a space for pouring the outer concrete (7). A constraint clamp (5) is fixed to the top of the side template (41) and used to compact and constrain the four sides of the side template (41); A rubber plug (8) passes through the opening (53) in the middle of the constraint clamp (5) and fits against the top surface of the steel pipe (11).

6. The mold according to claim 5, characterized in that, The cross section of the wooden template (4) perpendicular to its length direction is rectangular.

7. The mold according to claim 5, characterized in that, The constraint fixture (5) consists of a cross-shaped steel plate (51) and an L-shaped constraint platform (52) disposed on the outer edge of the cross-shaped steel plate (51). The L-shaped constraint platform (52) and the top of the side template (41) form a limiting fit relationship.

8. The mold according to claim 5, characterized in that, The diameter of the rubber stopper (8) is the same as the outer diameter of the steel pipe (11).

9. A method for preparing a specimen for the interface extension of a steel-concrete composite column, characterized in that, The mold as described in claim 5 is prefabricated in the factory for later use. The method for preparing the specimen includes: S1. Place the steel pipe (11) on the steel base plate (12), pour the central cylinder concrete (6) into the steel pipe (11), and attach strain gauges to the outer wall of the steel pipe (11). S2. Place the positioning block (2) at the four corners of the steel base plate (12), and place the bottom template (42) coated with concrete release agent through the top of the steel pipe (11) on the positioning block (2). Place the tied steel cage (3) through the top of the steel pipe (11) on the bottom template (42). Place the side template (41) on the positioning block (2) outside the steel cage (3). The side template (41), bottom template (42) and steel pipe (11) enclose the space for pouring the outer concrete (7). Fix the restraint clamp (5) on the top of the side template (41). Put the rubber plug (8) through the opening (53) in the middle of the restraint clamp (5) and attach it to the top surface of the steel pipe (11). Finally, pour the outer concrete (7). S3. After the outer concrete (7) has initially set, remove the restraint clamps (5) and rubber plugs (8). After 24 hours, remove the positioning block (2), demold the side formwork (41) and bottom formwork (42), and cure and level the specimen.

10. The method for preparing a steel-concrete composite column interface ejection specimen according to claim 9, characterized in that, In step S2, expansion gaps are reserved at the joints of the wooden template (4), and sealant is applied.

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