Device and method for testing viscosity performance of reinforcing steel bar-concrete interface

Abstract

The invention discloses a device and a method for testing the viscosity performance of a reinforcing steel bar-concrete interface, and is applied to the technical field of civil engineering. The device comprises a machine vision measuring device, a basic test platform, a reinforcing steel bar-concrete drawing test piece and a self-balancing long-term load holding device, the machine vision measuring device is carried on the basic test platform and comprises a grating ruler and a microscopic camera, the microscopic camera can slide on the grating ruler, and the grating ruler is arranged on the foundation test platform. And irradiating the characteristic points of the steel bar-concrete drawing test piece. According to the method, position coordinates of multiple feature points of concrete and steel bars are read through an optical means to calculate displacement distribution, and steel bar-concrete relative slippage, steel bar longitudinal strain and bonding stress distribution rules at any moment after load holding are further obtained; the blank of reliable testing of the deformation and the bonding stress of the embedded steel bar under long-term load can be filled; the multi-point test is realized, the test operation is free, abundant measurement data can be obtained, and a support is provided for the research of long-term viscosity performance.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, and more particularly to a testing device and method for testing the viscosity performance of a steel bar-concrete interface. Background Art

[0002] Reinforced concrete is an important structural form in the field of civil engineering. It is widely used in civil, industrial, military and other fields. The interfacial bonding performance of steel-concrete is related to the force transmission mechanism between the two materials, is a representation of the coordinated force of the two materials, and is the most basic property for the establishment of reinforced concrete structures. It has always attracted extensive attention from academia and engineering circles. At present, the short-term interfacial bonding slip behavior of steel-concrete has been fully studied, and a series of bonding-slip constitutive models have been proposed, which have positive significance for guiding engineering practice. However, the service life of civil engineering structures is relatively long. In actual engineering, reinforced concrete is in a state of long-term load bearing. The time-varying behavior of materials, such as concrete creep, shrinkage, and structural temperature deformation, is very obvious. The time-varying behavior of materials causes the interfacial performance of steel-concrete to also be time-varying. For example, the slip increases with time, the interfacial bonding stress redistributes with time, and the cooperative working performance of steel and concrete decreases, which then leads to increased structural deformation and continuous cracking, which is not conducive to structural safety, applicability and durability. Therefore, it is of great value to carry out research on the long-term interfacial bonding performance between steel and concrete.

[0003] However, research in this area has been blank for a long time. The fundamental reason is the lack of devices and methods for long-term deformation stability testing. Accurately obtaining the long-term time-varying deformation of embedded concrete steel bars along the length direction (i.e., axial direction) is the core technology for this research. At present, the main means of obtaining local deformation of steel bars is to paste resistive strain gauges, such as slotting steel bars and arranging strain gauges in sequence in the axial direction. However, the stability of strain gauge testing can only be maintained in the short term. Long-term testing is usually accompanied by changes in environmental parameters such as test conditions, temperature and humidity, which have a significant negative impact on the test stability of strain gauges. The data will drift irregularly by a large margin, resulting in the inability to complete long-term testing. This is a bottleneck problem that restricts the long-term bonding performance testing of steel bars and concrete. On the other hand, the strain gauges, 100 (1000) meter gauges, displacement meters and other testing instruments mainly used in steel bar-concrete bonding tests are essentially local single-point tests, with very limited measurement points and limited data acquisition, which is not conducive to systematic theoretical analysis and condensed conclusions. At the same time, due to the limitations of the on-site layout of 100 (1000) meter gauges and displacement meters, it is difficult to measure the deformation distribution of embedded steel bars. Chinese patent CN106644930B discloses a reinforced concrete internal bond slip test device and method, which adopts the method of setting cantilever bars on the steel bars, reflecting the internal steel bar deformation as the up and down movement of the cantilever bars, and then measuring its displacement through a displacement meter. However, the cantilever end itself is prone to large displacement, so the measured data has a large error. The measurement point data obtained by single-point testing is limited, and the actual slip amount is not measured.

[0004] In summary, short-term test schemes cannot be used for long-term tests. Currently, there is no solution to achieve reliable long-term strain testing of embedded steel bars, resulting in the unknown and blank research on the long-term interface stress distribution law and bonding performance of steel bars and concrete. At the same time, traditional testing methods are local single-point tests, which greatly limits the richness of data and needs to be improved. Therefore, how to provide a testing device and method for the viscosity performance of the steel bar-concrete interface is a problem that technicians in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a testing device and method for the viscosity performance of the steel bar-concrete interface, which breaks through the bottleneck problem of long-term deformation testing of steel bars inside concrete and solves the problem of small amount of data in traditional single-point testing. The load-holding device and the pulling specimen form a self-balancing force system to achieve loading and long-term load holding. The machine vision device uses a non-contact optical method to perform long-term, multi-point deformation testing.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A testing device for the viscosity performance of a steel bar-concrete interface comprises a machine vision measuring device, a basic test platform, a steel bar-concrete pulling specimen and a self-balancing long-term load holding device. The machine vision measuring device is mounted on the basic test platform. The machine vision measuring device comprises a first parallel guide rail, a second parallel guide rail, a grating ruler and a microscope camera installed on the first parallel guide rail and the second parallel guide rail. The grating ruler can slide in a vertical direction, and the microscope camera can slide longitudinally along the grating ruler to illuminate characteristic points of the steel bar-concrete pulling specimen.

[0008] Optionally, the surface of the steel-concrete tensile specimen is provided with a plurality of through holes, through which the microscope camera can illuminate the internal steel surface, and the microscope camera can illuminate and measure the displacement of the concrete surface. The steel-concrete tensile specimen is used in conjunction with a self-balancing long-term load holding device and a basic test platform.

[0009] Optionally, a self-balancing long-term load holding device includes a jack, a force sensor and a rotating body anchoring device. The rotating body anchoring device is firmly bonded to the end of the steel bar by epoxy resin glue. The force sensor is arranged between the loading end of the jack and the rotating body anchoring device. The tensile load is applied by controlling the elongation of the loading end of the jack. The self-balancing long-term load holding device realizes the loading, long-term load maintenance, load level monitoring and adjustment of the steel bar-concrete tensile specimen.

[0010] Optionally, the basic test platform is a metal frame structure, including 6 metal columns, 7 metal connecting beams and 1 metal base plate. The metal columns are connected by metal connecting beams. The basic test platform can carry machine vision measurement equipment and align and straighten steel-concrete tensile specimens. The basic test platform provides space for loading, long-term load holding and long-term testing.

[0011] Optionally, the base of the metal column is provided with a height adjustment bolt, and the height adjustment bolt can be adjusted by rotation to achieve a horizontal state of the metal base plate.

[0012] Optionally, the metal base plate is welded integrally with the metal column, and the first steel plate, the second steel plate, the third steel plate and the fourth steel plate are vertically welded on the metal base plate and arranged in an open box shape, in which the steel bar-concrete tensile specimen is placed. The third steel plate is grooved on one side to facilitate the passage of the steel bar-concrete tensile specimen, thereby further fixing the steel bar-concrete tensile specimen.

[0013] Optionally, three circular openings are provided on the second steel plate and the fourth steel plate, and a set of fastening devices is provided at each opening, the fastening devices include bolts, nuts and gaskets, and the steel bar-concrete tensile specimen is fixed and the position is adjusted by adjusting the fastening devices.

[0014] Optionally, the grating ruler is located between two metal connecting beams, the grating ruler and the metal beams are perpendicular to each other, and the grating ruler can slide between the two metal connecting beams in a parallel direction.

[0015] A method for testing the viscosity of a steel bar-concrete interface, using the above-mentioned testing device for the viscosity of a steel bar-concrete interface, comprises the following steps:

[0016] S1. Make steel bar-concrete tensile test pieces: stick thin steel wires on the surface of the steel bars in sequence, set hollow sleeves at the ends of the steel bars, use molds to install the steel bars and pour concrete. After the concrete is initially set for 1 to 2 days, pull out all the thin iron wires to form through holes that go directly from the concrete surface to the internal steel bar surface. Use thin iron wires to clear the through holes in time to avoid blockage, and maintain the concrete according to regulations;

[0017] S2. After the steel-concrete pull-out specimen reaches the test age, the specimen is installed: the test platform is set up, the metal base plate is horizontally adjusted by adjusting the height adjustment bolts of the column foot, the steel-concrete pull-out specimen is placed from top to bottom into the open box-shaped area formed by the vertical steel plate, and the jack, force sensor and rotating body anchoring device are inserted from the end of the steel bar in sequence, and epoxy resin glue is poured into the sleeve of the rotating body anchoring device, and cured for 5 to 7 days to make it completely adhered to the end of the steel bar; the steel-concrete pull-out specimen is fixed and its position is corrected by 6 sets of fastening devices, so that the direction of the steel bar is parallel to the direction of the grating ruler, and the loading end of the jack is appropriately extended to achieve the pre-tightened state between the jack, the force sensor and the rotating body anchoring device;

[0018] S3, numbering the surface area of ​​the steel-concrete tensile specimen, adjusting the position of the grating ruler so that it slides in the vertical direction of the metal connecting beam; at the same time, adjusting the position of the microscope camera so that it slides on the grating ruler so that the microscope camera can illuminate the numbered area inside through each through hole, and fixing the grating ruler after the adjustment is completed;

[0019] S4, by moving the microscope camera, sequentially irradiating the numbered areas and marking the feature points, and reading the position coordinates of the feature points according to the grating ruler;

[0020] S5. Measure, calculate and analyze the bonding mechanics law of the steel-concrete pull-out specimen under instantaneous loading: control the extension of the loading end of the jack to achieve loading, use the force sensor to monitor the load level, adjust the jack to load to the predetermined load level, use the grating ruler to read the coordinate position information of the characteristic point when the instantaneous loading is completed, and obtain the instantaneous loading displacement of the steel bar and concrete by subtracting the initial position coordinates, and calculate the relative slip distribution function, the longitudinal tensile strain distribution law of the steel bar and the local bonding stress of the steel-concrete pull-out specimen;

[0021] S6. Measure, calculate and analyze the bonding mechanics law of steel-concrete pull-out specimens under continuous loading: lock the jack to start long-term load holding, monitor the load size through the force sensor, and when the load reduction reaches 1% to 2% of the predetermined load level, extend the loading end of the jack to replenish the load to the predetermined load level. After holding the load for a predetermined time, use a microscope camera to illuminate the characteristic points of each area, calculate the continuous loading displacement of the steel bar and concrete, and calculate the relative slip distribution function, the longitudinal tensile strain distribution law of the steel bar and the local bonding stress of the steel-concrete pull-out specimen;

[0022] S7. Measure, calculate and analyze the bonding mechanics laws of the steel-concrete tensile specimen under long-term continuous loading; continue to hold the load and repeat S6 to obtain the relative slip distribution function, the longitudinal tensile strain distribution law of the steel bar and the local bonding stress of the steel-concrete tensile specimen at any time.

[0023] Optionally, S5 is specifically:

[0024] S51, control the extension of the loading end of the jack to achieve loading, use the force sensor to monitor the load level, adjust the jack to load to a predetermined load level, use the grating ruler to read the coordinate position information of the characteristic point when the instantaneous loading is completed, and obtain the instantaneous loading displacement of the steel bar and concrete by subtracting the initial position coordinates. The displacement distribution functions are obtained by curve fitting, which are the steel bar displacement distribution function and the concrete displacement distribution function. and concrete displacement distribution function Calculate the relative slip distribution function

[0025]

[0026] S52. Calculate the longitudinal tensile strain distribution of steel bars using the differential method:

[0027]

[0028] The steel bar instantaneous strain distribution function is obtained by interpolating the steel bar longitudinal tensile strain distribution curve.

[0029] S53. Calculate the local bonding stress of the steel bar-concrete tensile specimen based on the longitudinal force balance condition of the steel bar:

[0030]

[0031] In the formula, E s is the elastic modulus of the steel bar, d is the diameter of the steel bar, and the local bond stress curve of the steel bar-concrete tensile specimen is fitted to obtain the steel bar-concrete instantaneous bond stress distribution function

[0032] It can be seen from the above technical solution that, compared with the prior art, the present invention provides a testing device and method for the viscosity performance of the steel bar-concrete interface, which has the following beneficial effects:

[0033] 1. The present invention fills the gap in reliable testing of deformation and bonding stress of embedded steel bars under long-term load in steel-concrete;

[0034] 2. The present invention uses a microscopic camera to directly illuminate the surface of the internal steel bars, which better overcomes the error problem; the microscopic camera illumination method can be used to measure multiple points in any area within the machine vision recognition range, realizing "what you see is what you measure", and significantly improving the richness of data;

[0035] 3. The present invention has a high degree of freedom in displacement testing and can better test the relative slip amount. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0037] Figure 1 It is a front view of the testing device of the present invention;

[0038] Figure 2 A top view of the testing device of the present invention;

[0039] Figure 3 is a bottom-view cross-sectional view of the testing device of the present invention;

[0040] Figure 4 It is a left view of the testing device of the present invention;

[0041] Figure 5 is a schematic diagram of a third steel plate of the present invention;

[0042] Figure 6 It is a schematic diagram of the rotating body anchoring device of the present invention;

[0043] Figure 7 This is a schematic diagram of the steel bar of the present invention after the thin iron wire is attached longitudinally;

[0044] Figure 8 It is a schematic diagram of a cast steel-concrete tensile test piece of the present invention;

[0045] Fig. 9 It is a schematic diagram of the steel-concrete tensile test piece of the present invention after the thin iron wire is removed;

[0046] Fig.10 It is a schematic diagram of the area division of the steel-concrete tensile test piece of the present invention;

[0047] Fig.11 It is a schematic diagram of the characteristic point marking and position reading of the present invention;

[0048] Fig.12 It is a schematic diagram of the force balance analysis of the steel bar microelement of the present invention;

[0049] Fig.13 It is a schematic diagram of the relative slip distribution function and the bonding stress distribution function of instantaneous loading of the present invention;

[0050] Fig.14 It is a schematic diagram of the relative slip distribution function and the bonding stress distribution function of the load-bearing of the present invention;

[0051] In the figure: grating ruler 1, microscope lens 2, first metal column 3-1, second metal column 3-2, third metal column 3-3, fourth metal column 3-4, fifth metal column 3-5, sixth metal column 3-6, first metal connecting beam 4-1, second metal connecting beam 4-2, third metal connecting beam 4-3, fourth metal connecting beam 4-4, fifth metal connecting beam 4-5, sixth metal connecting beam 4-6, seventh metal connecting beam 4-7, metal bottom plate 5, first steel plate 6-1, second steel plate 6-2, third steel plate 6-3, fourth steel plate 6-4, first bolt 7-1, second bolt 7-2, third bolt 7-3, fourth bolt 7-4, fifth bolt 7-5, sixth bolt 7-6, first nut 7-7, second Nut 7-8, third nut 7-9, fourth nut 7-10, fifth nut 7-11, sixth nut 7-12, first gasket 7-13, second gasket 7-14, third gasket 7-15, fourth gasket 7-16, fifth gasket 7-17, sixth gasket 7-18, concrete 8, steel bar 9, sleeve 10, through hole 11, jack 12, force sensor 13, rotating body anchoring device 14, thin wire 15, first parallel guide rail 16-1, second parallel guide rail 16-2, first height adjustment bolt 17-1, second height adjustment bolt 17-2, third height adjustment bolt 17-3, fourth height adjustment bolt 17-4, fifth height adjustment bolt 17-5, sixth height adjustment bolt 17-6, wooden block 18. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] The embodiment of the present invention discloses a testing device for the viscosity performance of the steel bar-concrete interface, such as Figure 1-4 As shown, it includes a machine vision measuring device, a basic test platform, a steel-concrete tensile specimen and a self-balancing long-term load holding device. The machine vision measuring device is mounted on the basic test platform. The machine vision measuring device includes a first parallel guide rail 16-1, a second parallel guide rail 16-2, a grating ruler 1 and a microscope camera 2 installed on the first parallel guide rail 16-1 and the second parallel guide rail 16-2. The grating ruler 1 can slide in the vertical direction, and the microscope camera 2 can slide longitudinally along the grating ruler 1 to illuminate the characteristic points of the steel-concrete tensile specimen.

[0054] The above mechanism enables arbitrary adjustment of the position of the microscope camera 2, laying a foundation for the next step of irradiating characteristic points and displacement testing.

[0055] Furthermore, the surface of the steel-concrete tensile specimen is provided with a plurality of through holes 11, and the microscope camera 2 can illuminate the surface of the internal steel bars 9 through the through holes 11. The microscope camera 2 can illuminate and measure the surface displacement of the concrete 8. The steel-concrete tensile specimen is used in conjunction with a self-balancing long-term load holding device and a basic test platform.

[0056] In the embodiment of the present invention, the steel bar-concrete tensile test piece basically follows the general scheme in the field, that is, the steel bar 9 is embedded before pouring the concrete 8, and the sleeve 10 should be embedded at the loading end of the steel bar 9, so that the concrete 8 in this area does not interact with the steel bar 9 to avoid local bonding damage. The difference from the general scheme is that thin iron wires 15 are sequentially pasted on the surface of the steel bar 9 along the longitudinal direction, and the diameter of the thin iron wires 15 is controlled to be several millimeters. The main purpose is to take out the thin iron wires 15 after the initial setting of the poured concrete 8 to form a through hole 11 from the surface of the concrete 8 to the surface of the steel bar 9, so that the microscope camera 2 can illuminate the surface feature points of the steel bar 9 to read its position information with the help of the grating ruler 1. Because the iron wire is relatively thin, the influence of the tiny through hole 11 on the steel bar-concrete grip mechanism can be ignored.

[0057] Furthermore, the self-balancing long-term load holding device includes a jack 12, a force sensor 13 and a rotating body anchoring device 14. The rotating body anchoring device 14 is as shown in FIG. Figure 6 As shown, the rotating body anchoring device 14 and the end of the steel bar 9 are firmly bonded by epoxy resin glue, and the force sensor 13 is arranged between the loading end of the jack 12 and the rotating body anchoring device 14. The tensile load is applied by controlling the elongation of the loading end of the jack 12.

[0058] In the embodiment of the present invention, the jack 12 is a through-core mechanical jack 12, the force sensor 13 is a through-core spoke sensor, and the rotating body anchoring device 14 is a through-core rotating body anchoring device 14. The steel-concrete pull-out specimen, the jack 12, the force sensor 13, and the rotating body anchoring device 14 form a self-balanced force system, and the pull-out force of the steel bar 9 is measured by the force sensor 13. At the same time, by locking the loading end of the jack 12, a long-term load can be achieved. The load time course is monitored in real time by the sensor. Due to the creep behavior of the concrete 8, the steel bar 9 will be slowly pulled out, resulting in a decrease in the pull-out force, and the established load level can be maintained by further extending the loading section of the jack 12.

[0059] Furthermore, the basic test platform is a metal frame structure, including 6 metal columns, 7 metal connecting beams and 1 metal base plate 5, and the metal columns are connected by metal connecting beams; the basic test platform realizes the mounting of machine vision measurement equipment and the centering and straightening of steel-concrete tensile specimens, and the basic test platform provides a space for loading, long-term load holding and long-term testing.

[0060] In the embodiment of the present invention, the metal column includes a first metal column 3-1, a second metal column 3-2, a third metal column 3-3, a fourth metal column 3-4, a fifth metal column 3-5 and a sixth metal column 3-6, and the metal connecting beam includes a first metal connecting beam 4-1, a second metal connecting beam 4-2, a third metal connecting beam 4-3, a fourth metal connecting beam 4-4, a fifth metal connecting beam 4-5, a sixth metal connecting beam 4-6 and a seventh metal connecting beam 4-7; the first metal column 3-1 and the second metal column 3-2 are connected by the first metal connecting beam 4-1, and the second metal column 3-2 and The third metal columns 3-3 are connected by the first metal connecting beam 4-1, the fourth metal column 3-4 and the fifth metal column 3-5 are connected by the first metal connecting beam 4-1, the fifth metal column 3-5 and the sixth metal column 3-6 are connected by the first metal connecting beam 4-1, the first metal column 3-1 and the fourth metal column 3-4 are connected by the first metal connecting beam 4-1, the second metal column 3-2 and the fifth metal column 3-5 are connected by the first metal connecting beam 4-1, and the third metal column 3-3 and the sixth metal column 3-6 are connected by the first metal connecting beam 4-1.

[0061] Furthermore, the column base of the metal column is provided with a height adjustment bolt, and the height adjustment bolt can be adjusted by rotation to achieve a horizontal state of the metal base plate 5.

[0062] In an embodiment of the present invention, the height adjustment bolts include a first height adjustment bolt 17-1, a second height adjustment bolt 17-2, a third height adjustment bolt 17-3, a fourth height adjustment bolt 17-4, a fifth height adjustment bolt 17-5 and a sixth height adjustment bolt 17-6, which are sequentially arranged at the base of the first metal column 3-1, the second metal column 3-2, the third metal column 3-3, the fourth metal column 3-4, the fifth metal column 3-5 and the sixth metal column 3-6.

[0063] Furthermore, the metal bottom plate 5 is welded integrally with the metal column, and the first steel plate 6-1, the second steel plate 6-2, the third steel plate 6-3 and the fourth steel plate 6-4 are vertically welded on the metal bottom plate 5, arranged in an open box shape, in which the steel-concrete tensile specimen is placed, and the third steel plate 6-3 is grooved on one side to facilitate the steel-concrete tensile specimen to pass through, such as Figure 5 As shown, the steel bar-concrete tensile specimen is further fixed.

[0064] Furthermore, three circular openings are provided on the second steel plate 6-2 and the fourth steel plate 6-4, and a set of fastening devices is provided at each opening. The fastening devices include bolts, nuts and gaskets. The steel bar-concrete tensile specimen is fixed and its position is adjusted by adjusting the fastening devices.

[0065] In an embodiment of the present invention, the bolts include a first bolt 7-1, a second bolt 7-2, a third bolt 7-3, a fourth bolt 7-4, a fifth bolt 7-5 and a sixth bolt 7-6, the nuts include a first nut 7-7, a second nut 7-8, a third nut 7-9, a fourth nut 7-10, a fifth nut 7-11 and a sixth nut 7-12, and the gaskets include a first gasket 7-13, a second gasket 7-14, a third gasket 7-15, a fourth gasket 7-16, a fifth gasket 7-17 and a sixth gasket 7-18.

[0066] Furthermore, the grating ruler 1 is located between the two metal connecting beams, the grating ruler 1 and the metal beams are perpendicular to each other, and the grating ruler 1 can slide between the two metal connecting beams in a parallel direction.

[0067] In the embodiment of the present invention, the grating ruler 1 is located between the fifth metal connecting beam 4-5 and the sixth metal connecting beam 4-6.

[0068] and Figure 1-4 Corresponding to the device, an embodiment of the present invention further discloses a method for testing the viscosity performance of a steel bar-concrete interface. The method uses the device for testing the viscosity performance of a steel bar-concrete interface, and comprises the following steps:

[0069] S1. Make steel bar-concrete tensile test piece: stick thin steel wires on the surface of steel bar 9 in sequence, such as Figure 7As shown, a hollow sleeve 10 is provided at the end of the steel bar 9, the steel bar 9 is installed using a mold and concrete 8 is poured. Figure 8 As shown, after the concrete is initially set for 81 to 2 days, all the thin wires 15 are pulled out. Fig. 9 As shown, a through hole 11 is formed from the surface of the concrete 8 directly to the surface of the internal steel bar 9, and a thin iron wire 15 is used to timely clear the through hole 11 to avoid blockage, and the concrete 8 is cured according to regulations;

[0070] In the embodiment of the present invention, thin iron wires 15 are pasted longitudinally on the surface of the steel bar 9. The thin iron wires 15 can be distributed at equal intervals, and the adjacent distance is 2 to 3 cm. The thin iron wires 15 can be pasted with adhesives such as "502" glue, which can ensure that the concrete 8 does not fall off or dislocate during pouring and vibration, and make it easy to pull out and remove the thin iron wires 15 after the concrete 8 is initially set. The wire spacing is measured after the thin iron wires 15 are pasted. The pre-embedded hollow sleeve 10 at the end of the steel bar 9 can be made of materials such as PVC pipes with an inner diameter larger than the diameter of the steel bar 9;

[0071] S2. After the steel-concrete pull-out specimen reaches the test age, the specimen is installed: the test platform is set up, the metal base plate 5 is horizontally adjusted by adjusting the height adjustment bolts of the column foot, the steel-concrete pull-out specimen is placed from top to bottom into the open box-shaped area formed by the vertical steel plate, and the jack 12, the force sensor 13 and the rotating body anchoring device 14 are inserted from the end of the steel bar 9 in sequence, and epoxy resin glue is poured into the sleeve of the rotating body anchoring device 14, and cured for 5 to 7 days to make it completely adhered to the end of the steel bar 9; the steel-concrete pull-out specimen is fixed and its position is corrected by 6 sets of fastening devices, so that the direction of the steel bar 9 is parallel to the direction of the grating ruler 1, and the loading end of the jack 12 is appropriately extended to achieve the pre-tightened state between the jack 12, the force sensor 13 and the rotating body anchoring device 14;

[0072] In the embodiment of the present invention, a wooden block 18 may be placed under the jack 12 to provide support, and the preload may be 1 kN, which is monitored in real time by the force sensor 13 .

[0073] S3. Number the surface areas of the steel-concrete tensile specimens, such as Fig.10 As shown, the position of the grating ruler 1 is adjusted so that it slides in the vertical direction of the metal connecting beam; at the same time, the position of the microscope camera 2 is adjusted so that it slides on the grating ruler 1, so that the microscope camera 2 can illuminate the numbered area inside through each through hole 11, and the grating ruler 1 is fixed after the adjustment is completed;

[0074] In the embodiment of the present invention, the surface of the concrete 8 is numbered as: zone 1, zone 2, ..., zone i, ... (n-1) zone, zone n, and the surface of the steel bar 9 is directly reached through the through hole 11, and the surface of the steel bar 9 is numbered as: zone 1, zone 2, ..., zone i, ... (n-1) zone, zone n, wherein the distance between the (i-1) zone and the i zone of the steel bar 9 is L.i , the distance between the i-th zone and the (i+1)-th zone is L i +1, the spacing is measured when the thin iron wire 15 is pasted.

[0075] S4, by moving the microscope camera 2, sequentially illuminate the numbered areas and mark the feature points, such as Fig.11 As shown, the position coordinates of the feature points are read according to the grating ruler 1;

[0076] In the embodiment of the present invention, at least three feature points are marked for each partition of concrete 8 and steel bar 9. For the partition of concrete 8, the feature points C1, C2, C3, ... can be the corners of coarse aggregate, micropores, color spots on the surface of concrete 8, and all other points that are easy to identify the next time of irradiation. Similarly, for the distribution of steel bar 9, the feature points S1, S2, S3, ... can be color spots, textures, defects, and other points that are easy to identify again after irradiation. The initial state of the feature points of each partition before being subjected to force is irradiated, and its position coordinates are read according to the grating ruler 1: For example, the initial position coordinates of each C1 feature point in the (i-1) zone, i zone, and (i+1) zone of concrete 8 are expressed as: The initial position coordinates of each S1 characteristic point in the (i-1)th zone, ith zone, and (i+1)th zone of steel bar 9 are expressed as:

[0077] S5. Measure, calculate and analyze the bonding mechanics law of the steel bar-concrete tensile specimen under instantaneous loading: control the extension of the loading end of the jack 12 to achieve loading, use the force sensor 13 to monitor the load level, adjust the jack 12 to load to a predetermined load level, and analyze the force balance of the steel bar 9 microelement. Fig.12 As shown; the coordinate position information of the characteristic point when the instantaneous loading is completed is read by the grating ruler 1, and the instantaneous loading displacement of the steel bar 9 and the concrete 8 is obtained by subtracting the initial position coordinates, and the relative slip distribution function, the longitudinal tensile strain distribution law of the steel bar 9 and the local bonding stress of the steel bar-concrete tensile specimen are calculated. The relative slip distribution function and the bonding stress distribution function of the instantaneous loading are shown in Fig.13 As shown;

[0078] S6. Measure, calculate and analyze the bonding mechanics law of the steel-concrete pull-out specimen under continuous loading: lock the jack 12 to start long-term load holding, monitor the load size through the force sensor 13, and when the load reduction reaches 1% to 2% of the predetermined load level, extend the loading end of the jack 12 to replenish the load to the predetermined load level. After holding the load for a predetermined time, use the microscope camera 2 to illuminate the characteristic points of each area, calculate the continuous loading displacement of the steel bar 9 and the concrete 8, calculate the relative slip distribution function, the longitudinal tensile strain distribution law of the steel bar 9 and the local bonding stress of the steel-concrete pull-out specimen;

[0079] S7, measure, calculate and analyze the bonding mechanics law of the steel-concrete tensile specimen under long-term continuous loading; continue to hold the load, repeat S6 steps, obtain the relative slip distribution function, the longitudinal tensile strain distribution law of steel bar 9 and the local bonding stress of the steel-concrete tensile specimen at any time, continue to hold the load to the preset time, the relative slip distribution function and the bonding stress distribution function are as follows: Fig.14 shown.

[0080] Furthermore, S5 is specifically:

[0081] S51, control the jack 12 to extend the loading end to achieve loading, use the force sensor 13 to monitor the load level, adjust the jack 12 to load to a predetermined load level, use the grating ruler 1 to read the coordinate position information of the feature point when instantaneous loading is completed, and obtain the instantaneous loading displacement of the steel bar 9 and the concrete 8 by subtracting the initial position coordinates. The displacement distribution functions are obtained by curve fitting as follows: the displacement distribution function of the steel bar 9 and concrete 8 displacement distribution function Calculate the relative slip distribution function

[0082]

[0083] S52. Calculate the longitudinal tensile strain distribution of steel bar 9 using the differential method:

[0084]

[0085] The instantaneous strain distribution function of steel bar 9 is obtained by interpolating the longitudinal tensile strain distribution curve of steel bar 9.

[0086] S53. Calculate the local bonding stress of the steel bar-concrete tensile specimen based on the longitudinal force balance condition of steel bar 9:

[0087]

[0088] In the formula, E s is the elastic modulus of steel bar 9, d is the diameter of steel bar 9, and the local bond stress curve of steel bar-concrete tensile specimen is fitted to obtain the steel bar-concrete instantaneous bond stress distribution function

[0089] In the embodiment of the present invention, the state of each partition feature point after being irradiated in S51 is subjected to force, and its position coordinates are read according to the grating ruler 1: for example, the initial position coordinates of each C1 feature point in the (i-1) zone, i zone, and (i+1) zone of concrete 8 are expressed as: The initial position coordinates of each S1 characteristic point in the (i-1)th zone, ith zone, and (i+1)th zone of steel bar 9 are expressed as: The instantaneous displacement of each characteristic point of concrete 8 and steel bar 9 is:

[0090]

[0091] Where, m = C1, C2, C3, ... or S1, S2, S3, ..., q = 1, 2, 3 ..., i, ..., and the average displacement of each characteristic point in the same area is used to represent the instantaneous displacement of the area:

[0092]

[0093] Where p = C or S, n represents the number of feature points in a partition, and the instantaneous displacement of the partition is regarded as the displacement value at the longitudinal midpoint of the partition, and the coordinates are: x = X p,q .

[0094] By displacement of each zone of concrete 8: ...The curve fitting results in the instantaneous displacement distribution function of concrete 8 Similarly, the instantaneous displacement distribution function of steel bar 9 is obtained:

[0095] In the embodiment of the present invention, S6 specifically includes: holding the load until time t k After that, the microscope camera 2 is controlled to illuminate each feature point again, and its position is read by the grating ruler 1. For example, the initial position coordinates of each C1 feature point in the (i-1)th zone, the ith zone, and the (i+1)th zone of the concrete 8 are expressed as The initial position coordinates of each S1 characteristic point in the (i-1)th zone, ith zone, and (i+1)th zone of steel bar 9 are expressed as: The instantaneous displacement of each characteristic point of concrete 8 and steel bar 9 is:

[0096]

[0097] Similar to S51, the average displacement of each feature point in the same area is used to represent the area t k Time displacement:

[0098]

[0099] By displacement of each zone of concrete 8: ...Curve interpolation to obtain concrete 8t k Time displacement distribution function Similarly, the steel bar 9t k Time displacement distribution function Further conclusion is drawn that reinforced concrete t k hour:

[0100]

[0101] S62: According to steel bar 9t k Time displacement distribution function Calculation of steel bar 9t by difference method k The distribution law of longitudinal tensile strain is:

[0102]

[0103] The steel bar 9t is obtained by interpolating the above local strain value curve k Strain distribution function

[0104] Calculate the steel-concrete t according to the longitudinal force balance condition of steel bar 9 k Local bonding stress:

[0105]

[0106] The steel-concrete t k Bond stress distribution function

[0107] In the embodiment of the present invention, S7 continues to hold the load until time t n , repeat step S6 to obtain the relative slip distribution function Distribution law of longitudinal tensile strain of steel bar 9 Bond stress distribution function Generally, starting from the moment t0 when the instantaneous loading is completed, observations are made every 2 to 3 days within the first three months of holding the load, and after three months, observations are made every 5 to 7 days. The total holding time is determined based on the actual test conditions and is generally not less than three months.

[0108] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the method disclosed in the embodiment, since it corresponds to the device disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0109] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A testing device for the viscosity performance of the steel bar-concrete interface, characterized in that: The invention comprises a machine vision measuring device, a basic test platform, a steel-concrete tensile specimen and a self-balancing long-term load holding device. The machine vision measuring device is mounted on the basic test platform. The machine vision measuring device comprises a first parallel guide rail, a second parallel guide rail, a grating scale and a microscope camera installed on the first parallel guide rail and the second parallel guide rail. The grating scale can slide in a vertical direction, and the microscope camera can slide longitudinally along the grating scale to illuminate the characteristic points of the steel-concrete tensile specimen.

2. A testing device for the viscosity performance of the steel bar-concrete interface according to claim 1, characterized in that: The surface of the steel-concrete tensile specimen is provided with a plurality of through holes, through which the microscope camera can illuminate the internal steel surface, and can illuminate and measure the displacement of the concrete surface. The steel-concrete tensile specimen is used in conjunction with a self-balancing long-term load holding device and a basic test platform.

3. A testing device for the viscosity performance of the steel bar-concrete interface according to claim 1, characterized in that: The self-balancing long-term load holding device includes a jack, a force sensor and a rotating body anchoring device. The rotating body anchoring device and the end of the steel bar are firmly bonded by epoxy resin glue. The force sensor is arranged between the loading end of the jack and the rotating body anchoring device. The tensile load is applied by controlling the elongation of the loading end of the jack. The self-balancing long-term load holding device realizes the loading, long-term load maintenance, load level monitoring and adjustment of the steel bar-concrete tensile specimen.

4. A testing device for the viscosity performance of the steel bar-concrete interface according to claim 1, characterized in that: The basic test platform is a metal frame structure, including 6 metal columns, 7 metal connecting beams and 1 metal base plate. The metal columns are connected by metal connecting beams. The basic test platform can carry machine vision measurement devices and align and straighten steel-concrete tensile specimens. The basic test platform provides space for loading, long-term load holding and long-term testing.

5. A testing device for the viscosity performance of the steel bar-concrete interface according to claim 4, characterized in that: The column base of the metal column is provided with a height adjustment bolt, and the height adjustment bolt can be adjusted by rotation to achieve a horizontal state of the metal base plate.

6. A testing device for the viscosity performance of the steel bar-concrete interface according to claim 4, characterized in that: The metal base plate is welded integrally with the metal column, and the first steel plate, the second steel plate, the third steel plate and the fourth steel plate are vertically welded on the metal base plate, arranged in an open box shape, in which the steel bar-concrete tensile specimen is placed. The third steel plate is grooved on one side to facilitate the steel bar-concrete tensile specimen to pass through, thereby further fixing the steel bar-concrete tensile specimen.

7. A testing device for the viscosity performance of the steel bar-concrete interface according to claim 6, characterized in that: Three circular openings are arranged on the second steel plate and the fourth steel plate, and a set of fastening devices is arranged at each opening. The fastening devices include bolts, nuts and washers. The steel bar-concrete tensile specimen can be fixed and its position adjusted by adjusting the fastening devices.

8. A testing device for the viscosity performance of the steel bar-concrete interface according to claim 4, characterized in that: The grating ruler is located between two metal connecting beams. The grating ruler and the metal beams are perpendicular to each other. The grating ruler can slide in a parallel direction between the two metal connecting beams.

9. A method for testing the viscosity of the steel bar-concrete interface, characterized in that: A testing device for the adhesive properties of a steel bar-concrete interface according to any one of claims 1 to 8 comprises the following steps: S1. Make steel bar-concrete tensile test pieces: stick thin steel wires on the surface of the steel bars in sequence, set hollow sleeves at the ends of the steel bars, use molds to install the steel bars and pour concrete. After the concrete is initially set for 1 to 2 days, pull out all the thin iron wires to form through holes that go directly from the concrete surface to the internal steel bar surface. Use thin iron wires to clear the through holes in time to avoid blockage, and maintain the concrete according to regulations; S2. After the steel-concrete pull-out specimen reaches the test age, the specimen is installed: the test platform is set up, the metal base plate is horizontally adjusted by adjusting the height adjustment bolts of the column foot, the steel-concrete pull-out specimen is placed from top to bottom into the open box-shaped area formed by the vertical steel plate, and the jack, force sensor and rotating body anchoring device are inserted from the end of the steel bar in sequence, and epoxy resin glue is poured into the sleeve of the rotating body anchoring device, and cured for 5 to 7 days to make it completely adhered to the end of the steel bar; the steel-concrete pull-out specimen is fixed and its position is corrected by 6 sets of fastening devices, so that the direction of the steel bar is parallel to the direction of the grating ruler, and the loading end of the jack is appropriately extended to achieve the pre-tightened state between the jack, the force sensor and the rotating body anchoring device; S3, numbering the surface area of ​​the steel-concrete tensile specimen, adjusting the position of the grating ruler so that it slides in the vertical direction of the metal connecting beam; at the same time, adjusting the position of the microscope camera so that it slides on the grating ruler so that the microscope camera can illuminate the numbered area inside through each through hole, and fixing the grating ruler after the adjustment is completed; S4, by moving the microscope camera, sequentially irradiating the numbered areas and marking the feature points, and reading the position coordinates of the feature points according to the grating ruler; S5. Measure, calculate and analyze the bonding mechanics law of the steel-concrete pull-out specimen under instantaneous loading: control the extension of the loading end of the jack to achieve loading, use the force sensor to monitor the load level, adjust the jack to load to the predetermined load level, use the grating ruler to read the coordinate position information of the characteristic point when the instantaneous loading is completed, and obtain the instantaneous loading displacement of the steel bar and concrete by subtracting the initial position coordinates, and calculate the relative slip distribution function, the longitudinal tensile strain distribution law of the steel bar and the local bonding stress of the steel-concrete pull-out specimen; S6. Measure, calculate and analyze the bonding mechanics law of steel-concrete pull-out specimens under continuous loading: lock the jack to start long-term load holding, monitor the load size through the force sensor, and when the load reduction reaches 1% to 2% of the predetermined load level, extend the loading end of the jack to replenish the load to the predetermined load level. After holding the load for a predetermined time, use a microscope camera to illuminate the characteristic points of each area, calculate the continuous loading displacement of the steel bar and concrete, and calculate the relative slip distribution function, the longitudinal tensile strain distribution law of the steel bar and the local bonding stress of the steel-concrete pull-out specimen; S7. Measure, calculate and analyze the bonding mechanics laws of the steel-concrete tensile specimen under long-term continuous loading; continue to hold the load and repeat S6 to obtain the relative slip distribution function, the longitudinal tensile strain distribution law of the steel bar and the local bonding stress of the steel-concrete tensile specimen at any time.

10. A method for testing the viscosity of the steel bar-concrete interface according to claim 9, characterized in that: S5 is specifically: S51, control the extension of the loading end of the jack to achieve loading, use the force sensor to monitor the load level, adjust the jack to load to a predetermined load level, use the grating ruler to read the coordinate position information of the characteristic point when the instantaneous loading is completed, and obtain the instantaneous loading displacement of the steel bar and concrete by subtracting the initial position coordinates. The displacement distribution functions are obtained by curve fitting, which are the steel bar displacement distribution function and the concrete displacement distribution function. and concrete displacement distribution function Calculate the relative slip distribution function S52. Calculate the longitudinal tensile strain distribution of steel bars using the differential method: The steel bar instantaneous strain distribution function is obtained by interpolating the steel bar longitudinal tensile strain distribution curve. S53. Calculate the local bonding stress of the steel bar-concrete tensile specimen based on the longitudinal force balance condition of the steel bar: In the formula, E s is the elastic modulus of the steel bar, d is the diameter of the steel bar, and the local bond stress curve of the steel bar-concrete tensile specimen is fitted to obtain the steel bar-concrete instantaneous bond stress distribution function

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