A chemical anchor high temperature pull-out test device and method

Abstract

The present invention relates to the technical field of performance measurement of connecting anchors, and in particular to a chemical anchor high-temperature pull-out test device and method thereof. The chemical anchor high-temperature pull-out test device of the present invention comprises a concrete test block, a chemical anchor, a heating device and a pulling device; the chemical anchor comprises an anchor and a chemical anchoring adhesive, and an anchor hole for the anchor to penetrate is provided in the concrete test block; the anchor and the anchor hole are bonded and fixed by the chemical anchoring adhesive; the heating device comprises a temperature controller, a heating wire and a thermocouple; a cavity extending along the axial direction is provided in the anchor, the heating wire is evenly arranged in the cavity, and the temperature detection end of the thermocouple extends into the anchor hole; the heating wire is connected to the current output port of the temperature controller through a conductive wire, and the signal output end of the thermocouple is connected to the signal control port of the temperature controller through a signal line. The present invention can quickly and accurately control the temperature of the anchor, and thus quickly and accurately complete the pulling performance test of the chemical anchor at different temperatures.

Description

Technical Field

[0001] The invention relates to the technical field of performance determination of connecting anchor pieces, and in particular to a chemical anchor high-temperature pulling test device and a method thereof. Background Art

[0002] Fires frequently occur in various buildings, tunnels, integrated pipeline corridors, and cable trenches, causing a large number of casualties and property losses. Therefore, the research on the fire resistance of buildings (structures) has always received widespread attention. Not only has the fire resistance performance of the main structure of buildings and structures received a lot of research in the engineering community, but the fire resistance performance of connecting anchors has also received more and more attention.

[0003] Chemical anchors are widely used for the installation and fixation of steel structures such as building curtain walls, brackets, and hangers. Existing research results show that the performance of chemical anchors is very sensitive to temperature, and the bearing capacity of chemical anchors will decrease rapidly at high temperatures. Quantitative research on the pull-out performance of chemical anchors at different temperatures is the key to evaluating the safety of chemical anchors under fire.

[0004] There are two main research methods commonly used at present: one method is to implant the anchor bolt with chemical anchoring agent in the steel sleeve, and then use an electric furnace to heat it and then conduct a pull-out test. Since steel has good thermal conductivity, this method can better control the temperature of the anchor bolt. However, since the damage of chemical anchor bolts in concrete itself has many forms such as anchor glue-anchor bond damage, anchor glue-concrete bond damage, and colloid cohesive damage, it is difficult to use steel sleeves to truly simulate the damage form of anchor bolts in concrete when they are tensile. Another method is to implant chemical anchor bolts in concrete and then heat them in an electric furnace. Due to the low thermal conductivity of concrete, the temperature deep in the anchor bolt often rises very slowly, while the temperature in the shallow part rises rapidly. This uneven boundary condition has a great influence on the analysis test results. In addition, concrete will also suffer thermal damage and crack at high temperature. The bearing capacity of chemical anchor bolts in cracked concrete can be reduced by about 29%, which has a great influence on the bearing capacity results of anchor bolts. Summary of the invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a chemical anchor high temperature pull-out test device and method thereof, which can accurately and quickly control the temperature of the chemical anchor.

[0006] To achieve the above-mentioned purpose, the chemical anchor high-temperature pulling test device designed in the present invention comprises a concrete test block, a chemical anchor embedded in the concrete test block, a heating device and a pulling device; the chemical anchor comprises an anchor and a chemical anchoring glue, and an anchor hole for the anchor to penetrate is opened in the concrete test block; the anchor and the anchor hole are bonded and fixed by the chemical anchoring glue; it is characterized in that the heating device comprises a temperature controller, a heating wire and a thermocouple; a cavity extending along the axial direction is opened in the anchor, the heating wire is evenly arranged in the cavity, and the temperature detection end of the thermocouple extends into the anchor hole; the heating wire is connected to the current output port of the temperature controller through a conductive wire, and the signal output end of the thermocouple is connected to the signal control port of the temperature controller through a signal line, and the temperature of the anchor is servo-controlled by the heating device.

[0007] As a preferred embodiment, the upper end of the anchor bolt is provided with an opening connected to the cavity, and the lower end of the anchor bolt is closed; the upper end of the anchor bolt extends upward from the upper surface of the concrete test block, and the lower end of the anchor bolt extends downward from the bottom surface of the concrete test block, the opening at the upper end of the anchor bolt is sealed by a plug, the conductive wire passes through the plug and extends into the cavity to be connected to the heating wire, and the lower end of the anchor bolt is connected to the pulling device.

[0008] As a preferred embodiment, the cavity is filled with magnesium oxide powder.

[0009] As a preferred embodiment, the pulling device includes a reaction frame, a through-hole jack, a tension sensor and a micrometer; the lower end of the anchor bolt is fixed on the reaction frame, the through-hole jack is arranged below the reaction frame and connected to the lower end of the anchor bolt, the tension sensor is installed at the lower end of the anchor bolt to collect the tension exerted on the anchor bolt, and the micrometer is connected to the reaction frame to collect the displacement change of the anchor bolt.

[0010] A method for performing a pull-out performance test on a chemical anchor using the chemical anchor high temperature pull-out test device is characterized by comprising the steps of:

[0011] S1: Take a plurality of anchor bolts of the same specification, and open a cavity in each anchor bolt, use a mold to make a plurality of concrete test blocks of the same specification, and open an anchor bolt hole in each concrete test block, and evenly pre-embed a plurality of thermocouples around the anchor bolt hole in each concrete test block;

[0012] S2: Take an anchor bolt and install it into the anchor bolt hole of the concrete test block, and inject chemical anchor glue for anchoring;

[0013] S3: After the chemical anchoring glue reaches the designed strength, start the through-hole jack, apply preload force to preload and maintain tension;

[0014] S4: Heat the anchor bolt to a predetermined temperature T through a temperature controller, increase the tension of the through-hole jack until the chemical anchor bolt is destroyed, and record the data of the tension sensor and the dial gauge in real time throughout the process, generate a tension-displacement ND curve of the load N collected by the tension sensor and the displacement D collected by the dial gauge, and take the tension at the peak of the tension-displacement ND curve as the ultimate bearing capacity N T , the displacement at the peak is the limit slip D T ;

[0015] S5: Calculate the cohesion of the chemical anchor at a predetermined temperature T according to formula (1):

[0016]

[0017] In the formula, is the cohesion of the chemical anchor; d is the diameter of the failure surface; l ef is the anchorage length of the anchor bolt in the concrete test block;

[0018] S6: Take another anchor bolt and concrete test block and perform pull-out test at different temperatures according to the above steps to obtain the cohesion of chemical anchor bolts at different temperatures. and the limit slip D T ; The relationship curves of the cohesion and temperature of the chemical anchor and the relationship curves of the limiting slip and temperature are drawn respectively.

[0019] As a preferred solution, in the step S4, the chemical anchor failure is divided into three failure states: A: bonding failure between the chemical anchor glue and the anchor; B: bonding failure between the chemical anchor glue and the concrete test block; C: cohesive failure of the chemical anchor glue;

[0020] When the failure state A occurs, in step S5, d is the outer diameter of the anchor bolt. It is the cohesion between the anchoring glue and the anchor bolt;

[0021] When the failure state B occurs, in step S5, d is the inner diameter of the anchor hole, is the cohesion between the concrete specimen and the chemical anchoring adhesive;

[0022] When the failure state C occurs, in step S5, d is the average diameter of the failure surface of the chemical anchoring glue, It is the cohesive force of chemical anchoring glue.

[0023] As a preferred solution, in step S6, it also includes obtaining the chemical anchor destruction state at different temperatures and drawing a relationship curve between the chemical anchor destruction form and temperature.

[0024] Compared with the existing chemical anchor pulling device using an electric furnace, the advantages of the present invention are:

[0025] 1. By opening a cavity extending along the axial direction of the anchor bolt, the heating wire of the heating device is evenly arranged in the cavity, and combined with the temperature controller and the thermocouple, the anchor bolt temperature can be servo-controlled quickly and accurately, thereby quickly and accurately completing the pulling performance test of the chemical anchor bolt at different temperatures.

[0026] 2. The magnesium oxide powder filled in the anchor bolt has good thermal conductivity and insulation, which can not only prevent the heating wire from contacting the anchor bolt wall and causing short circuit and leakage, but also transfer the heat of the heating wire to the anchor bolt better.

[0027] 3. There is no need to heat the concrete specimen as a whole, which reduces the impact of concrete thermal damage and cracking on the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of a chemical anchor high temperature pull-out test device of the present invention;

[0029] Figure 2 for Figure 1 Axial section of the middle anchor bolt;

[0030] The components in the figure are numbered as follows: concrete test block 10, anchor hole 11, chemical anchor 20, anchor 21, cavity 21.1, magnesium oxide powder 21.2, plug 21.3, chemical anchoring glue 22, heating device 30, temperature controller 31, heating wire 32, thermocouple 33, conductive wire 34, signal line 35, pulling device 40, reaction frame 41, through-hole jack 42, tension sensor 43, micrometer 44. DETAILED DESCRIPTION

[0031] In order to better understand the present invention, the invention will be described in detail below in conjunction with specific examples.

[0032] See also Figure 1A chemical anchor high temperature pull-out test device comprises a concrete test block 10, a chemical anchor 20 embedded in the concrete test block 10, a heating device 30 and a pull-out device 40; the chemical anchor 20 comprises an anchor 21 and a chemical anchoring glue 22, an anchor hole 11 for the anchor 21 to penetrate is opened in the concrete test block 10, the upper end of the anchor 21 extends upward from the upper surface of the concrete test block 10, and the lower end of the anchor 21 extends downward from the bottom surface of the concrete test block 10; the anchor 21 is bonded and fixed to the anchor hole 11 by the chemical anchoring glue 22; the heating device 30 comprises a temperature controller 31, an electric heating wire 32 and a thermocouple 33, and the electric The hot wire 32 is connected to the current output port of the temperature controller 31 through the conductive wire 34, and the signal output end of the thermocouple 33 is connected to the signal control port of the temperature controller 31 through the signal line 35; the pulling device 40 includes a reaction frame 41, a through-core jack 42, a tension sensor 43 and a micrometer 44, the lower end of the anchor 21 is fixed on the reaction frame 41, the through-core jack 42 is arranged below the reaction frame 41 and connected to the lower end of the anchor 21, the tension sensor 43 is installed at the lower end of the anchor 21 to collect the tension size of the anchor 21, and the micrometer 44 is connected to the reaction frame 41 to collect the displacement change of the anchor 21.

[0033] See also Figure 2 The key point of the present invention is that a cavity 21.1 extending along the axial direction is provided in the anchor bolt 21, the electric heating wire 32 of the heating device 30 is evenly arranged in the cavity 21.1, the upper end of the anchor bolt 21 is provided with an opening connected to the cavity 21.1, the lower end of the anchor bolt 21 is closed, the opening at the upper end of the anchor bolt 21 is sealed by a plug 21.3, and the conductive wire 34 passes through the plug 21.3 and extends into the cavity 21.1 to connect with the electric heating wire 32; by arranging the electric heating wire in the anchor bolt 21, and servo-controlling the temperature of the anchor bolt 21 by the heating device 30, the temperature of the anchor bolt 21 can be quickly and accurately controlled, and then the pulling performance test of the chemical anchor bolt at different temperatures can be quickly and accurately completed. In addition, the cavity 21.1 is filled with magnesium oxide powder, and the heat conduction of the magnesium oxide powder makes the anchor bolt 21 heated more evenly.

[0034] In addition, analysis of the mechanism of action of chemical anchors shows that the pull-out performance of chemical anchors mainly depends on the bonding force between the chemical anchoring glue and the concrete. Therefore, the cavity 21.1 extending along the axial direction of the anchor 21 will not affect the pull-out performance of the chemical anchor 20.

[0035] The method for conducting a pull-out performance test on a chemical anchor using the above chemical anchor high temperature pull-out test device comprises the following steps:

[0036] S1: Take a plurality of anchor bolts 21 of the same specification, and open a cavity 21.1 in each anchor bolt 21, use a mold to make a plurality of concrete test blocks 10 of the same specification, and open an anchor bolt hole 11 in each concrete test block 10, and evenly pre-embed a plurality of thermocouples 33 around the outer periphery of the anchor bolt hole 11 in each concrete test block 10;

[0037] S2: Take an anchor bolt 21 and install it into the anchor bolt hole 11 of the concrete test block 10, and inject chemical anchor glue 22 for anchoring;

[0038] S3: After the chemical anchoring glue 22 reaches the design strength, the through-hole jack 42 is started, and a preload force of 1KN is applied to maintain the tension;

[0039] S4: The anchor bolt 21 is heated to a predetermined temperature T by the temperature controller 31, and the tension of the through-hole jack 42 is increased until the chemical anchor bolt 20 is damaged. The damage of the chemical anchor bolt 20 is divided into three damage states: A: the bonding damage between the chemical anchor glue 22 and the anchor bolt 21; B: the bonding damage between the chemical anchor glue 22 and the concrete test block 10; C: the cohesive damage of the chemical anchor glue 22;

[0040] The data of the tension sensor 43 and the micrometer 44 are recorded in real time throughout the whole process, and a tension displacement ND curve of the load N collected by the tension sensor 43 and the displacement D collected by the micrometer 44 is generated. The tension at the peak of the tension displacement ND curve is taken as the ultimate bearing capacity N. T , the displacement at the peak is the limit slip D T ;

[0041] S5: Calculate the cohesion of the chemical anchor 20 at a predetermined temperature T according to formula (1):

[0042]

[0043] In the formula, is the cohesion of the chemical anchor; d is the diameter of the failure surface; l ef is the anchorage length of the anchor bolt in the concrete test block;

[0044] When the failure state A occurs, in step S5, d is the outer diameter of the anchor bolt 20, is the cohesion between the anchoring glue 22 and the anchor bolt 21;

[0045] When the damage state B occurs, in step S5, d is the inner diameter of the anchor hole 11, is the cohesion between the concrete specimen 10 and the chemical anchoring adhesive 22;

[0046] When the damage state C occurs, in step S5, d is the average diameter of the damage surface of the chemical anchoring glue 22, is the cohesive force of the chemical anchoring glue 22.

[0047] S6: Take another anchor bolt 21 and concrete test block 10 and perform pull-out tests at different temperatures according to the above steps to obtain the damage state of the chemical anchor bolt and the cohesion of the chemical anchor bolt at different temperatures. and the limit slip D T ; The relationship curves between the chemical anchor failure form and temperature, the relationship curves between the chemical anchor cohesion and temperature, and the relationship curves between the limit slip and temperature are drawn respectively.

[0048] The pull-out performance of chemical anchors is characterized by the relationship curve between the failure form of chemical anchors and temperature, the relationship curve between the cohesion of chemical anchors and temperature, and the relationship curve between the limiting slip and temperature.

[0049] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for testing the pulling performance of chemical anchor bolts using a high temperature pulling test device, characterized in that: Includes steps: S1: taking a plurality of anchor bolts (21) of the same specification, and opening a cavity (21.1) in each anchor bolt (21), using a mold to make a plurality of concrete test blocks (10) of the same specification, and opening an anchor bolt hole (11) in each concrete test block (10), and pre-embedding a plurality of thermocouples (33) uniformly around the outer periphery of the anchor bolt hole (11) in each concrete test block (10); S2: Take an anchor bolt (21) and install it into the anchor bolt hole (11) of the concrete test block (10), and inject chemical anchor glue (22) for anchoring; S3: After the chemical anchoring glue (22) reaches the designed strength, the through-hole jack (42) is started to apply a preload force and maintain the tension; S4: The anchor bolt (21) is heated to a predetermined temperature T by a temperature controller (31), and the tension of the through-hole jack (42) is increased until the chemical anchor bolt (20) is damaged. The data of the tension sensor (43) and the dial gauge (44) are recorded in real time throughout the whole process, and a tension-displacement ND curve of the load N collected by the tension sensor (43) and the displacement D collected by the dial gauge (44) is generated. The tension at the peak of the tension-displacement ND curve is taken as the ultimate bearing capacity N. T , the displacement at the peak is the limit slip D T ; S5: Calculate the cohesion of the chemical anchor (20) at a predetermined temperature T according to formula (1): In the formula, is the cohesion of the chemical anchor; d is the diameter of the failure surface; l ef is the anchorage length of the anchor bolt in the concrete test block; S6: Take another anchor bolt (21) and a concrete test block (10) and perform a pull-out test at different temperatures according to the above steps to obtain the cohesion of the chemical anchor bolt at different temperatures. and the limit slip D T ; The relationship curves of the cohesion and temperature of the chemical anchor and the relationship curves of the limit slip and temperature are drawn respectively; The chemical anchor high temperature pull-out test device comprises a concrete test block (10), a chemical anchor (20) embedded in the concrete test block (10), a heating device (30) and a pull-out device (40); the chemical anchor (20) comprises an anchor (21) and a chemical anchoring glue (22); an anchor hole (11) for the anchor (21) to penetrate is provided in the concrete test block (10); the anchor (21) and the anchor hole (11) are bonded and fixed by the chemical anchoring glue (22); the heating device (30) comprises a temperature controller (31), an electric heating wire (32) and a heat exchanger (40); The anchor bolt (21) is provided with a cavity (21.1) extending along its axial direction, the heating wire (32) is evenly arranged in the cavity (21.1), and the temperature detection end of the thermocouple (33) extends into the anchor bolt hole (11); the heating wire (32) is connected to the current output port of the temperature controller (31) through a conductive wire (34), and the signal output end of the thermocouple (33) is connected to the signal control port of the temperature controller (31) through a signal wire (35), and the temperature of the anchor bolt (21) is servo-controlled by the heating device (30).

2. The method for performing a pull-out performance test on a chemical anchor according to claim 1, characterized in that: In the step S4, the damage of the chemical anchor bolt (20) is divided into three damage states: A: the bond failure between the chemical anchoring glue (22) and the anchor bolt (21); B: the bond failure between the chemical anchoring glue (22) and the concrete test block (10); C: cohesive failure of chemical anchoring glue (22); When the failure state A occurs, in step S5, d is the outer diameter of the anchor bolt (20), is the cohesive force between the anchoring glue (22) and the anchor bolt (21); When the failure state B occurs, in step S5, d is the inner diameter of the anchor hole (11), is the cohesion between the concrete test block (10) and the chemical anchoring glue (22); When the damage state C occurs, in step S5, d is the average diameter of the damage surface of the chemical anchoring glue (22), is the cohesive force of the chemical anchoring glue (22).

3. The method for performing a pull-out performance test on a chemical anchor according to claim 2, characterized in that: In the step S6, it also includes obtaining the destruction state of the chemical anchor at different temperatures and drawing a relationship curve between the chemical anchor destruction form and temperature.

4. The method for performing a pull-out performance test on a chemical anchor according to claim 1, characterized in that: The upper end of the anchor bolt (21) is provided with an opening connected to the cavity (21.1), and the lower end of the anchor bolt (21) is closed; the upper end of the anchor bolt (21) extends upward from the upper surface of the concrete test block (10), and the lower end of the anchor bolt (21) extends downward from the bottom surface of the concrete test block (10); the opening at the upper end of the anchor bolt (21) is sealed by a plug (21.3); the conductive wire (34) passes through the plug (21.3) and extends into the cavity (21.1) to be connected to the heating wire (32); and the lower end of the anchor bolt (21) is connected to the pulling device (40).

5. The method for performing a pull-out performance test on a chemical anchor according to claim 1 or 2, characterized in that: The cavity (21.1) is filled with magnesium oxide powder.

6. The method for performing a pull-out performance test on a chemical anchor according to claim 1 or 2, characterized in that: The pulling device (40) comprises a reaction frame (41), a through-hole jack (42), a tension sensor (43) and a micrometer (44); the lower end of the anchor bolt (21) is fixed on the reaction frame (41), the through-hole jack (42) is arranged below the reaction frame (41) and connected to the lower end of the anchor bolt (21), the tension sensor (43) is installed at the lower end of the anchor bolt (21) to collect the tension magnitude borne by the anchor bolt (21), and the micrometer (44) is connected to the reaction frame (41) to collect the displacement change of the anchor bolt (21).

7. The method for performing a pull-out performance test on a chemical anchor according to claim 6, characterized in that: The cavity (21.1) is filled with magnesium oxide powder.

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