Induction and control system of concrete cracks

Abstract

The present invention relates to a concrete crack induction and control system. More specifically, the concrete crack induction and control system may include a concrete test specimen, a plurality of reinforcing bars penetrating the sides of the concrete test specimen parallel to each other, a crack inducer inserted across the center of the concrete test specimen in a direction perpendicular to the reinforcing bars, a bottom body supporting and fixing the concrete test specimen, a test bed supporting the bottom body, a first frame positioned on one side of the concrete test specimen and fixed by one end of the reinforcing bar penetrating the concrete test specimen, a second frame positioned on the other side of the concrete test specimen and fixed by the other end of the reinforcing bar penetrating the concrete test specimen, a load-applying rod positioned between the concrete test specimens and having one end fixed to both ends of one side of the first frame to form a length in the direction of the second frame, a hydraulic cylinder fixed to both ends of one side of the second frame opposite to one side of the first frame to apply a load to the load-applying rod, a jig connecting one end of the reinforcing bar fixed by penetrating the first frame to a horizontal actuator, and a reaction jig that supports both ends of the other side of the second frame, spaced apart from each other, and fixed to the upper part of the test bed. Accordingly, cracks can be induced in concrete test specimens and the crack width can be controlled.

Description

Technology Field

[0001] The present invention relates to a concrete crack induction and control system, and more specifically, to a concrete crack induction and control system capable of inducing and causing cracks in a concrete test specimen and controlling the width of the cracks that occur. Background Technology

[0003] Post-installation anchor bolts allow for the installation of anchors after the location of the structure on the concrete foundation has been determined. This offers the advantage of adaptability even if the structural design or the location of the structure changes. However, it has the disadvantage of lower strength compared to pre-installation anchors and vulnerability to vibration and fatigue.

[0004] To date, clear regulations and standards regarding testing of post-installed anchor bolts in cracked concrete have not been established in Korea.

[0005] In the case of the anchor standard test applied to cracked concrete by the American Concrete Institute (ACI), the maximum crack width is about 0.3 mm, and when considering service loads, the maximum crack width is applied up to 0.5 mm.

[0006] In cracked concrete, the crack width varies depending on the live load. Post-installation anchor bolts are installed at the locations of microcracks after they have been induced in the concrete. A precise system is required to induce these microcracks. However, installing anchors is difficult because the induced crack directions vary widely. Therefore, to simulate this, a system capable of precise control to vary the size of the crack width is required. The problem to be solved

[0008] The problem that the present invention aims to solve is to provide a concrete crack induction and control system capable of inducing and causing cracks in a concrete test specimen and controlling the width of the cracks that occur.

[0009] In particular, the objective of the present invention is to provide a concrete crack induction and control system that can precisely induce cracks in a concrete test specimen to test conditions (crack width 0.3 mm or 0.5 mm) using cylinders installed on both sides of the concrete test specimen, induce cracks in the center using a crack inducer inserted during concrete pouring, and control the crack width by connecting reinforcing bars to a horizontal actuator.

[0011] The problems of the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0013] To solve the problem described above, a concrete crack induction and control system according to one embodiment of the present invention comprises: a concrete test specimen; a plurality of reinforcing bars penetrating the sides of the concrete test specimen parallel to each other; a crack inducer inserted across the center of the concrete test specimen in a direction perpendicular to the reinforcing bars; a bottom body supporting and fixing the concrete test specimen; a test bed supporting the bottom body; a first frame disposed on one side of the concrete test specimen and fixed by one end of the reinforcing bar penetrating the concrete test specimen; a second frame disposed on the other side of the concrete test specimen and fixed by the other end of the reinforcing bar penetrating the concrete test specimen; a load-applying rod disposed between the concrete test specimens and having one end fixed to both ends of one side of the first frame to form a length in the direction of the second frame; a hydraulic cylinder fixed to both ends of one side of the second frame opposite to one side of the first frame to apply a load to the load-applying rod; a jig connecting one end of the reinforcing bar fixed by penetrating the first frame to a horizontal actuator; and supporting both ends of the other side of the second frame, but mutually It may include a reaction jig that is spaced apart and fixed to the upper part of the test bed.

[0014] In addition, when a load is applied by the hydraulic cylinder, tensile force is transmitted to the reinforcing bar through the load-applying rod, the first frame, and the second frame, and microcracks may occur in the concrete test specimen.

[0015] In addition, the width of the crack in the concrete test specimen can be controlled to 0.3 mm or 0.5 mm by driving control of the horizontal actuator.

[0016] In addition, a groove is formed to support the hydraulic cylinder and the force rod, and a support member may be further included that is supported by both ends of the upper surface of the bottom body.

[0017] In addition, the plurality of reinforcing bars may include a pair of upper reinforcing bars and a pair of lower reinforcing bars that penetrate from one side to the other of the concrete test specimen and are arranged parallel to each other at both ends of the side of the concrete test specimen.

[0018] Additionally, the crack inducer may include an axis formed in an H shape that extends in length by passing between the pair of upper reinforcing bars and the pair of lower reinforcing bars, and plates formed at both ends of the axis and spaced apart at a certain distance from the outer sides of the upper reinforcing bars and lower reinforcing bars. At this time, the plates may be positioned opposite to the first frame and the second frame.

[0020] Specific details of other embodiments are included in the detailed description and drawings. Effects of the invention

[0022] A concrete crack induction and control system according to one embodiment of the present invention can precisely induce cracks in a concrete test specimen up to test conditions (crack width 0.3 mm or 0.5 mm) by using cylinders installed on both sides of the concrete test specimen.

[0023] In addition, cracks can be generated in the center using crack inducers inserted during concrete pouring, and the width of the cracks can be controlled by connecting reinforcing bars to a horizontal actuator.

[0025] The effects according to the present invention are not limited to those exemplified above, and other effects will be clearly understood by those skilled in the art from the description in the specification below. Brief explanation of the drawing

[0027] FIG. 1 is a perspective view showing a concrete crack induction and control system according to one embodiment of the present invention. Figure 2 is a top view of the concrete crack induction and control system of Figure 1. Figure 3 is a side view of the concrete crack induction and control system of Figure 1. FIG. 4 is a perspective view of the components of the concrete crack induction and control system of FIG. 1. Figure 5 is a drawing for explaining the fabrication of the concrete test specimen of Figure 1. Figure 6 is a cross-sectional view of the concrete test specimen prepared in Figure 5. Specific details for implementing the invention

[0028] The following description merely illustrates the principles of the invention. Therefore, those skilled in the art may invent various devices that embody the principles of the invention and are included within the concept and scope of the invention, even if they are not explicitly described or illustrated in this specification. Furthermore, all conditional terms and embodiments listed in this specification are, in principle, explicitly intended only for the purpose of understanding the concept of the invention and should be understood as not being limited to the embodiments and conditions specifically listed as such.

[0029] Furthermore, in the following description, ordinal expressions such as "first," "second," etc., are intended to describe mutually equal and independent objects, and should be understood as having no meaning of main / sub or master / slave in their order.

[0030] The aforementioned objectives, features, and advantages will become clearer through the following detailed description in conjunction with the attached drawings, and accordingly, a person skilled in the art to which the invention pertains will be able to easily implement the technical concept of the invention.

[0031] The features of each of the various embodiments of the present invention may be combined or combined with one another, either partially or wholly, and as will be fully understood by those skilled in the art, various technical interlocking and operation are possible, and each embodiment may be implemented independently of one another or together in an interlocking relationship.

[0032] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings.

[0034] FIG. 1 is a perspective view showing a concrete crack induction and control system according to an embodiment of the present invention. FIG. 2 is a top view of the concrete crack induction and control system of FIG. 1. FIG. 3 is a side view of the concrete crack induction and control system of FIG. 1. FIG. 4 is a perspective view of the components of the concrete crack induction and control system of FIG. 1.

[0035] Referring to FIGS. 1 to 4, a concrete crack induction and control system according to one embodiment of the present invention may include a concrete test specimen (1), a first frame (2), a second frame (3), a reaction jig (4), a force rod (5), a hydraulic cylinder (6), a bottom body (6), a plurality of reinforcing bars (8), a jig (9), a support (10), a test bed (11), and a crack inducer (12).

[0036] The concrete test specimen (1) can be manufactured by pouring using a formwork, and can be manufactured by inserting multiple reinforcing bars and crack inducers during pouring. The manufacturing of the concrete test specimen can be explained in detail through FIGS. 5 and FIGS. 6.

[0037] FIG. 5 is a drawing for explaining the fabrication of the concrete test specimen of FIG. 1. FIG. 6 is a cross-sectional view of the concrete test specimen fabricated in FIG. 5. Referring to FIG. 5, a hollow space through which a plurality of reinforcing bars (8) can pass is formed on both opposing sides of the formwork (20), and a groove through which a crack inducer can be inserted is formed on the other two sides where the hollow space is not formed.

[0038] Referring to FIGS. 5 and 6, a plurality of reinforcing bars (8) are inserted through the upper and lower hollows on both sides of the formwork (20) and are arranged parallel to each other, and the crack inducer (12) may include an axis (121) formed in an H shape that extends in length by passing between a pair of upper reinforcing bars and a pair of lower reinforcing bars, and plates (122) formed at both ends of the axis (121) and spaced apart at a certain distance from the upper reinforcing bars (81) and lower reinforcing bars (82).

[0039] At this time, plates (122) of the crack-inducing body (12) can be placed in the grooves on both sides of the formwork (20).

[0040] A concrete test specimen (1) can be produced by pouring concrete into a formwork (20) in which a plurality of reinforcing bars (8) and crack inducers (12) are inserted, and the crack inducers (12) are inserted in a direction perpendicular to the direction of penetration of the reinforcing bars (8) at the center of the concrete.

[0041] At this time, in order to fix the concrete test specimen (1) to the bottom body (7) in the formwork (20), a circular tube (not shown) can be erected during pouring to make holes in each side, top surface, bottom surface, etc. of the test specimen.

[0042] When looking at the cross-section (cross-section cut with respect to the crack inducer) of the concrete test specimen (1) poured using the formwork (20) of FIG. 5, as shown in FIG. 6, the crack inducer (12) is inserted with respect to the center of the concrete test specimen (1) poured, a pair of upper reinforcing bars (81) and lower reinforcing bars (82) are spaced apart parallel to each other, the axis (121) of the crack inducer (12) is inserted between the upper reinforcing bars (81) and the lower reinforcing bars (82), and the plate (122) is formed at both ends of the axis (121) and spaced apart at a certain distance from the upper reinforcing bars (81) and the lower reinforcing bars (82).

[0043] At this time, the crack inducer (12) can be formed from a metal plate of approximately 2 mm.

[0044] A concrete test specimen (1) with reinforcing bars (8) and crack inducers (12) inserted as shown in FIGS. 5 and 6 can be fixed to a bottom body (7) through holes (Fig. 1, 1h) that are drilled in each side by screws / bolts, etc., and can be supported by the bottom body (7). Additionally, the bottom body (7) can be supported by a test bed (11).

[0045] A first frame (2) is disposed on one side of a concrete test specimen (1) that is supported and fixed to a bottom body (7), through which one end of a reinforcing bar penetrating the concrete test specimen (1) is fixed, and a second frame (3) is disposed on the other side of the concrete test specimen (1), through which the other end of a reinforcing bar (8) penetrating the concrete test specimen (1) is fixed. Accordingly, the first frame (2) and the second frame (3) can form a plurality of hollows (h) through which a plurality of reinforcing bars (8) can pass, as shown in FIG. 4.

[0046] The load-applying rod (5) is a cylindrical rod that can be positioned between concrete test specimens (1) and has one end fixed to both ends of one side of the first frame (2) to form a length in the direction of the second frame (3). Additionally, a hydraulic cylinder (6) can be fixed to both ends of one side of the second frame (3) opposite to one side of the first frame (2) to apply a load to the load-applying rod (5).

[0047] The base (10) is supported by both ends of the upper surface of the bottom body (7) and can support a hydraulic cylinder (6) and a load-applying rod (5). At this time, referring to FIG. 4, the base (10) may have a groove (10h) formed on its upper surface and may be formed in a stepped structure. The load-applying rod (5) may be supported in the groove of the highest layer, the hydraulic cylinder (6) may be supported in the groove of the middle layer, and the second frame (3) may be supported in the groove of the lowest layer. At this time, the groove (10h) may be formed in various shapes such as a V-shape or a U-shape, and may maintain the axial direction of the load-applying rod (5) and the hydraulic cylinder (6).

[0048] The jig (9) can connect one end of the fixed reinforcing bar (8) through the first frame (2) to a horizontal actuator (not shown), and the reaction jig (4) supports both ends of the other side of the second frame (3) and is spaced apart from each other and can be fixed to the upper part of the test bed (11).

[0049] A concrete crack induction and control system according to one embodiment of the present invention can be formed with the structure of FIGS. 1 to 4 as described above, and can induce microcracks in a concrete test specimen (1) by applying tensile force to a reinforcing bar (8) through a hydraulic cylinder (6).

[0050] The load applied by hydraulic cylinders (6) installed on both sides of the concrete test specimen applies tensile force to the reinforcing bar through the load rod (5) and the first and second frames (2, 3), and a crack may occur in the center of the test specimen (1) by the crack inducer (12) inserted during concrete pouring. At this time, the width of the crack can be controlled by connecting the reinforcing bar to a horizontal actuator, and the generated crack can be maintained at 0.3 mm or 0.5 mm.

[0051] By controlling the degree of cracking, data regarding seismic performance evaluation can be obtained, and the system of the present invention can generate and maintain cracks in concrete applied to the simulated seismic shear / tensile test among the service condition test items for seismic performance verification of post-installed anchors for seismic performance evaluation, and can be applied to the seismic performance evaluation of anchors.

[0052] At this time, the seismic performance evaluation of the anchor was conducted as follows. First, it was performed using a torque-controlled M12 stud anchor bolt. A concrete test specimen (1) to be installed with the anchor was poured to a size of (420×420×200 mm) and then cured. Microcracks were generated in the concrete test specimen (1) through the crack-inducing control system of the present invention, and then the manufacturer's installation conditions (effective insertion depth: 70 mm, installation torque: 60 The anchor was installed according to the method. In addition, after maintaining the installation torque for 10 minutes, the torque was removed and finally installed at 50% of the installation torque.

[0053] Through the system of the present invention, static tensile and static shear tests were performed after applying a load up to a crack width of 0.3 mm, which is the test condition. For the seismic test, the setup was the same as for the static test, and after additionally inducing a crack width of 0.5 mm, a total of 140 cycles of repetitive behavior were performed at a speed of 0.1 Hz.

[0054] The test load values ​​were calculated according to Equations 1 and 2 using the results of static tensile and static shear tests. Here, is the maximum load result of the static test, is concrete compressive strength, represents the tensile strength of the anchor steel. After the cyclic loading was completed, a load was applied until failure of the anchor to verify the residual strength. At this time, the load was applied in three stages according to the ACI 355.2 standard. Here, Neq can be the stage 1 seismic tensile test load, Nm can be the stage 2 seismic tensile test load, and Ni can be the stage 3 seismic tensile test load. Additionally, Veq can be the stage 1 seismic shear test load, Vm can be the stage 2 seismic shear test load, and Vi can be the stage 3 seismic shear test load.

[0056]

[0057]

[0059]

[0060]

[0062] The results of the test loads and static tensile / static shear tests for the seismic test are as follows.

[0063]

[0064] As such, the average results of the seismic tensile test and seismic shear test were 15.1 kN and 23.7 kN, respectively, which were found to be more than 160% of the judgment criteria Neq and Veq. This indicates that the seismic performance of the anchor bolt is satisfactory.

[0065] As a result, the concrete crack induction and control system of the present invention precisely induces cracks in a concrete specimen to test conditions (crack width 0.3 mm or 0.5 mm) and generates cracks in the center using a crack inducer inserted during concrete pouring, making it suitable for use in anchor bolt seismic performance testing.

[0067] Although embodiments of the present invention have been described in more detail with reference to the attached drawings, the present invention is not necessarily limited to these embodiments and may be modified in various ways within the scope of the technical spirit of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not limit, the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of protection of the present invention shall be interpreted by the claims below, and all technical spirits within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention. Explanation of the symbols

[0069] 1 : Concrete test specimen 2 : 1st frame 3 : 2nd frame 4 : Reaction jig 5 : Garyeokbong 6 : Hydraulic cylinder 7 : Bottom body 8: Rebar, 81: Top Rebar, 82: Bottom Rebar 9 : Jig 10 : Stand 11 : Test bed 12 : Crack inducer 20 : Formwork

Claims

Claim 1 A concrete test specimen; a plurality of reinforcing bars penetrating the sides of the concrete test specimen in parallel with each other; a crack inducer inserted across the center of the concrete test specimen in a direction perpendicular to the reinforcing bars; a bottom body supporting and fixing the concrete test specimen; a test bed supporting the bottom body; a first frame disposed on one side of the concrete test specimen and fixed by one end of the reinforcing bar penetrating the concrete test specimen, and a second frame disposed on the other side of the concrete test specimen and fixed by the other end of the reinforcing bar penetrating the concrete test specimen; a pair of load-applying rods disposed on both sides of the concrete test specimen, with one end fixed to both ends of one side of the first frame to form a length in the direction of the second frame; a pair of hydraulic cylinders fixed to both ends of one side of the second frame opposite to one side of the first frame to apply a load to the pair of load-applying rods disposed on both sides of the concrete test specimen. A concrete crack induction and control system comprising: a base supported by both ends of the floor body and formed as a step structure having a groove formed on the upper surface, wherein the load-applying rod is supported in the groove of the highest layer, a hydraulic cylinder is supported in the groove of the middle layer, and a second frame is supported in the lowest layer through which the other end of the reinforcing bar is fixed; a jig connecting one end of the reinforcing bar fixed through the first frame to a horizontal actuator; and a reaction jig supporting both ends of the other side of the second frame, spaced apart from each other, and fixed to the upper part of the test bed; wherein when a load is applied by the hydraulic cylinder, tensile force is transmitted to the reinforcing bar through the load-applying rod, the first frame, and the second frame, a microcrack is generated in the center of the concrete test specimen by the inserted crack inducer, and the width of the crack in the concrete test specimen is controlled to 0.3 mm or 0.5 mm by driving control of the horizontal actuator connected to one end of the reinforcing bar. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 In claim 1, the plurality of reinforcing bars includes a pair of upper reinforcing bars and a pair of lower reinforcing bars that penetrate from one side to the other side of the concrete test specimen and are arranged parallel to each other at both ends of the side of the concrete test specimen, and the crack inducing body includes an axis formed in an H shape that extends in length by passing between the pair of upper reinforcing bars and the pair of lower reinforcing bars, and plates formed at both ends of the axis and spaced apart at a certain distance from the outer sides of the upper reinforcing bars and lower reinforcing bars, wherein the plates are arranged opposite to the first frame and the second frame, a concrete crack inducing and control system.

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