KR102582597B1 - Crack Length Measuring Device for Structural Safety Check - Google Patents

Abstract

The present invention relates to a crack length measuring device for structural safety diagnosis used to measure the length of cracks formed in a structure during safety diagnosis and safety inspection of the structure, and includes an eccentric bracket (50) installed on the end cap (31) and extending to one side. ; A wire hole (50a) formed in the eccentric bracket (50) so that its center coincides with the wire outlet hole (31h); An upper semicircular body (60) installed on the eccentric bracket (50) and in close contact with the upper outer peripheral surface of the rotary encoder (42); A lower semicircular body (70) combined with the upper semicircular body (60) and in close contact with the lower outer peripheral surface of the rotary encoder (42); A disk 61 formed on one side of the upper semicircular body 60; A boss (62) protruding at the center of the disk (61); An angle adjustment arm (80) supported on the boss (62) and having a rotation center concentric with the encoder shaft (42s); An arcuate long hole (81) formed in the angle adjustment arm (80); A tapped hole (61t) formed in the disk (61) along the arcuate long hole (81); It includes a fixing bolt (82) coupled to the tapped hole (61t) through the circular long hole (81).

Description

Crack Length Measuring Device for Structural Safety Check}

The present invention relates to a crack length measuring device for structural safety diagnosis used to measure the length of cracks formed in a structure during safety diagnosis and safety inspection of the structure. More specifically, it relates to a crack length measuring device for structural safety diagnosis that allows the angle of the measuring wheel to be adjusted by an angle adjustment arm. This relates to a crack length measuring device for structural safety diagnosis.

In general, architectural structures or civil engineering structures have a cycle of life and death, starting from the design stage, through the construction stage and the use stage, and then into the stage of natural collapse due to the passage of service life, artificial demolition, or premature collapse due to poor construction or damage. The cause of collapse of the same structure may be partly due to natural causes due to the passage of service life, but most of them are deeply related to the deformation of the structure due to external forces acting on the structure during the construction or use stage.

Among such structural deformations, cracks that occur in the structure are difficult to detect early because the width of the crack is so small, and the speed of crack progression is generally very slow, so constructors and users believe that it does not have a significant impact on the safety of the structure. Therefore, it is easy to overlook this without thinking, but since any crack can cause structural defects in the structure and ultimately lead to the collapse of the structure, cracking in the structure is a very important factor in diagnosing the safety of the structure. It is also one of the very important devices for diagnosing the stability of a structure.

As mentioned above, a cracker with a graduated scale is used to measure cracks occurring in building structures or civil engineering structures. Although this cracker is useful for roughly measuring the length of a crack, it does not accurately measure the length of a curved crack. .

That is, when measuring the length of a curved crack using a conventional cracker, the length of each straight section (from A to K) is measured one by one, as shown in Figure 1 of the attached drawing, and then added up to determine the cracks formed in the structure 10. The total length of (12) is calculated or the crack length is measured from the approximate shortest distance (S) from the start point to the end point of the crack (12).

However, measuring the length of the crack 12 in the structure 10 one by one several times for each straight section not only takes a lot of time, but also is difficult and dangerous when the crack occurs in a high and dangerous area such as the ceiling. There was a problem.

In addition, measuring the shortest distance (S) from the starting point of the crack 12 to the ending point can shorten the time, but there is a problem in that a large error occurs between the actual crack length and the measured value.

To solve these problems, Domestic Patent Publication No. 10-2016531 (hereinafter referred to as 'prior art') rolls a measuring wheel along a crack in the structure, and transmits the power transmitted from the measuring wheel to a rotary encoder through a belt. It has been proposed to count the length of the crack and then output the crack length through a display unit.

However, in this prior art, the tilt angle of the clevis plate supporting the measuring wheel cannot be changed, so there was a problem in that the clevis plate could not be changed to the optimal tilt depending on the position of the pole.

In addition, in the prior art, when the clevis plate rotates horizontally around the steering bearing, the signal line drawn from the rotary encoder moves, so if the movement of the signal line continues for a long period of time, there is a problem in that the signal line is disconnected and an output error occurs.

Domestic Registered Patent Publication No. 10-0601358 (announcement date 2006.07.24.) Domestic Registered Patent Publication No. 10-0779096 (announcement date 2007.11.27.) Domestic Registered Patent Publication No. 10-1764640 (announcement date 2017.08.07.) Domestic Registered Patent Publication No. 10-1406326 (announcement date 2014.06.12.) Domestic Registered Patent Publication No. 10-2016531 (announcement date 2019.08.30.) Domestic Registered Patent Publication No. 10-1972768 (announcement date 2019.04.29.) Domestic Registered Patent Publication No. 10-2069122 (announcement date 2020.01.22.)

The present invention was made to solve the above problems, and its purpose is to provide a crack length measuring device for structural safety diagnosis that can prevent disconnection of the signal line drawn from the rotary encoder and change the angle of the measuring wheel. .

A crack length measuring device for structural safety diagnosis to achieve the object of the present invention includes a pole having a certain length; An end cap installed at the end of the pole and having a wire outlet hole; A measuring wheel that rolls along the cracks that occur on the surface of the structure; A driving pulley installed on the measuring wheel; A rotary encoder having a signal line passing through a wire outlet hole and detecting the number of revolutions of the measuring wheel; Driven pulley installed on the encoder shaft of the rotary encoder; In the crack length measuring device for structural safety diagnosis including a belt that transmits power from the driving pulley to the driven pulley,

An eccentric bracket installed on the end cap and extending to one side; A wire hole formed in the eccentric bracket so that its center coincides with the wire outlet hole; An upper semicircular body installed on the eccentric bracket and in close contact with the upper outer peripheral surface of the rotary encoder; A lower semicircular body combined with the upper semicircular body and in close contact with the lower outer peripheral surface of the rotary encoder; A disk formed on one side of the upper semicircle; A boss protruding from the center of the disk; An angle adjustment arm supported by a boss and having a rotation center concentric with the encoder axis; A circular long hole formed in the angle-adjusting arm; A tapped hole formed in the disk along an arcuate hole; It has the feature of including a fixing bolt that is coupled to the tapped hole through a circular long hole.

The present invention includes a bearing support hole penetrating the center of the disk and the boss; A small diameter bearing inserted into the bearing support hole and supporting the end of the encoder shaft; It has the feature of including a belt interference prevention groove formed at the corner where the disk and the upper semicircle meet.

The present invention includes a bent portion formed on an eccentric bracket; It is formed on the eccentric bracket and has the feature of including a wire sagging prevention hole through which the signal wire passes.

As described above, the present invention is configured to change the angle of the angle adjustment arm 80, and thus has the effect of changing the angle of the measuring wheel 40 to an appropriate angle depending on the position of the pole 30.

Since the rotation center of the angle adjustment arm 80 is located at the same center as the center of the encoder shaft 42s provided in the rotary encoder 42, only the belt 44 moves when the angle adjustment arm 80 rotates. The rotary encoder 42 and the signal line 42w do not move, which has the effect of preventing disconnection of the signal line 42w.

Belt 44 interference that may occur when the belt 44 interferes with the corner of the upper semicircular groove 65 is caused by the belt interference prevention groove 64 formed at the corner where the upper semicircular body 60 and the disk 61 meet. It has the effect of preventing breakage.

The signal line (42w) drawn from the rotary encoder (42) is connected to the wire hole (50a) formed in the eccentric bracket (50) through the wire sagging prevention hole (50h) formed in the eccentric bracket (50) and the wire formed in the end cap (31). When wiring through the lead-out hole 31h, the middle of the signal line 42w can be passed through the wire sagging prevention hole 50h, which has the effect of preventing sagging of the signal line 42w.

Since it is configured to support the encoder shaft 42s of the rotary encoder 42 by the small diameter bearing 63 supported in the bearing support hole 61h formed at the center of the disk 61 and the boss 62, the encoder shaft It has the effect of preventing sagging of (42s) and driven pulley (43).

There is an effect that the angle adjustment arm 80 can be installed to be tilted to one side with respect to the pole 30 by the bent portion 51 formed on the eccentric bracket 50.

Since the rotary encoder 42 is configured to be fixed by engaging between the upper semicircular body 60 and the lower semicircular body 70, when the centers of the belt grooves formed on the driving pulley 41 and the driven pulley 43 are aligned, There is the convenience of being able to move the rotary encoder 42 in the axial direction.

1 is a diagram schematically showing measuring the length of a crack in a conventional structure.
Figure 2 is an exploded perspective view according to the present invention.
Figure 3 is an exploded perspective view of Figure 2 seen from the bottom of the opposite side.
Figure 4 is a side view according to the present invention
Figure 5 is a side cross-sectional view according to the present invention
Figure 6 is a cross-sectional view taken along line A-A' of Figure 5
Figure 7 is a rear view according to the present invention
Figure 8 is a bottom view according to the present invention
Figure 9 is a perspective view according to the present invention
Figure 10 is a perspective view showing measuring the crack length by turning the present invention upside down.
Figure 11 is a circuit diagram schematically showing the configuration according to the present invention.

Hereinafter, an embodiment according to the present invention will be described in detail with reference to FIGS. 2 to 11 of the accompanying drawings.

The present invention includes a pole (30) having a certain length; An end cap (31) installed at the end of the pole (30) and having a wire outlet hole (31h); A measuring wheel (40) rolling along the crack (21) occurring on the surface of the structure (20); It includes a driving pulley 41 installed on the measuring wheel 40.

The pole 30 can be formed by, for example, cutting a straight metal pipe to a certain length. The end cap 31 can be formed by turning a metal round bar as a material.

For example, the end cap 31 can be installed by gluing it to the end of the pole 30. In another example, the end cap 31 can be press-fitted or shrink-fitted to the end of the pole 30.

The configuration for combining the end cap 31 and the eccentric bracket 50 below is, for example, arranging cap fixing tab holes 31t in a circular shape at the end of the end cap 31, and attaching the eccentric bracket 50. A cap fastening hole (52h) whose center coincides with the cap fastening tap hole (31t) is formed, and then the cap bolt (52) is coupled to the cap fastening tap hole (31t) through the cap fastening hole (52h) to form an eccentric A bracket 50 is installed on the end cap 31.

As shown in FIG. 9, the measuring wheel 40 rolls along the crack 21 occurring in the structure 20 and serves to generate a rotational force on the encoder shaft 42s of the rotary encoder 42. For example, the driving pulley 41 may be formed integrally with one side of the measurement wheel 40 so as to be concentric with the measurement wheel 40.

The present invention includes a rotary encoder (42) having a signal line (42w) passing through a wire outlet hole (31h) and detecting the rotation speed of the measuring wheel (40); A driven pulley (43) installed on the encoder shaft (42s) of the rotary encoder (42); It includes a belt 44 that transmits power from the driving pulley 41 to the driven pulley 43.

The encoder shaft 42s of the rotary encoder 42 is rotated by power transmitted through the measuring wheel 40, driving pulley 41, belt 44, and driven pulley 43. The rotary encoder 42 can be configured as an incremental rotary encoder, for example.

As shown in Figure 11, the signal line 42w drawn from the rotary encoder 42 is connected to the input port of the microcontroller 90, and the pulse waveform output from the rotary encoder 42 is transmitted to the microcontroller 90. It can be configured to measure the length of the crack portion 21 by counting.

The value counted by the microcontroller 90 is stored in a memory built into the microcontroller 90, and the value stored in the memory is output to a display device such as a liquid crystal display or seven-segment module 92 to display the crack length. do.

The zero point switch (SW1) can be connected to the input port of the microcontroller 90 to set the value output to the seven-segment module 92 to '0'. At this time, a pull-up resistor (R1) connected to the power supply can be connected to the connection terminal of the zero point switch (SW1) and the microcontroller (90).

The microcontroller 90 includes program memory (ROM), a non-volatile memory such as flash memory, data memory (RAM), a volatile memory, a clock generator, a timer, an input/output interface circuit, a communication circuit, etc., built into a single semiconductor chip. can be used.

A through hole (symbol omitted) for press-fitting the rotary encoder 42 around the encoder shaft 42s can be formed in the center of the driven pulley 43. The belt 44 may be made of, for example, a urethane round belt with a certain diameter.

The power generated from the measuring wheel 40 is transmitted to the encoder shaft 42s of the rotary encoder 42 by the belt 44 wound around the driving pulley 41 and the driven pulley 43. As shown in FIG. 6, an annular V-groove (symbol omitted) around which the belt 44 is wound can be formed on the outer peripheral surfaces of the driving pulley 41 and the driven pulley 43.

The present invention includes an eccentric bracket (50) installed on the end cap (31) and extending to one side; A wire hole (50a) formed in the eccentric bracket (50) so that its center coincides with the wire outlet hole (31h); It is installed on the eccentric bracket 50 and includes an upper semicircular body 60 in close contact with the upper outer peripheral surface of the rotary encoder 42.

The eccentric bracket 50 can be formed, for example, into a rectangular shape using a metal plate having a certain thickness.

An upper semicircular groove 65 having an inner diameter corresponding to the outer diameter of the rotary encoder 42 is formed in the lower part of the upper semicircular body 60. This upper semicircular groove 65 is in close contact with the upper outer peripheral surface of the rotary encoder 42.

The configuration for connecting the eccentric bracket 50 and the upper semicircular body 60 is to cut the upper outer peripheral surface of the upper semicircular body 60 into a flat surface and then form a tapped hole 60a for bracket fixation on the flat surface. After forming a bracket fastening hole (53h) whose center coincides with the bracket fastening tapped hole (60a) in the eccentric bracket (50), the bracket fastening bolt (53) is passed through the bracket fastening hole (53h) to the bracket fastening tapped hole. When coupled to (60a), the eccentric bracket (50) is installed on the top of the upper semicircular body (60).

The present invention includes a lower semicircular body (70) combined with the upper semicircular body (60) and in close contact with the lower outer peripheral surface of the rotary encoder (42); A disk 61 formed on one side of the upper semicircular body 60; It includes a boss 62 protruding from the center of the disk 61.

A lower semicircular groove 75 having an inner diameter corresponding to the outer diameter of the rotary encoder 42 is formed on the upper part of the lower semicircular body 70. This lower semicircular groove 75 is in close contact with the lower outer peripheral surface of the rotary encoder 42.

An encoder fixing bolt (71) for coupling the upper semicircle (60) and the lower semicircle (70) and pressing the rotary encoder (42) located between the upper semicircle (60) and the lower semicircle (70). can be provided.

As shown in Figure 5 of the attached drawing, when the upper semicircular body 60 and the lower semicircular body 70 are coupled by the encoder fixing bolt 71, there is a constant width between the upper semicircular body 60 and the lower semicircular body 70. A gap is formed so that the upper semicircular groove 65 and the lower semicircular groove 75 are in close contact with the outer peripheral surface of the rotary encoder 42.

The configuration for installing the encoder fixing bolt 71 is to form a tapped hole 60t for fixing the encoder in the upper semicircle 60, and a tapped hole 60t for fixing the encoder in the lower semicircle 70. After forming the matching counterbore hole (70h), the encoder fixing bolt (71) is coupled to the encoder fixing tap hole (60t) through the counterbore hole (70h) to form the upper semicircular body (60) and the lower semicircular body (70 ) is connected by the encoder fixing bolt (71).

At this time, the encoder fixing bolt 71 passes through the gap between the upper semicircular body 60 and the lower semicircular body 70. When the encoder fixing bolt 71 is strongly tightened, the rotary encoder 42 located between the upper semicircular body 60 and the lower semicircular body 70 is fixed under strong pressure.

The upper semicircular body 60, disk 61, and boss 62 can all be molded as one piece.

The present invention includes an angle adjustment arm (80) supported on a boss (62) and having a rotation center concentric with the encoder shaft (42s); An arcuate long hole (81) formed in the angle adjustment arm (80); A tapped hole (61t) formed in the disk (61) along the arcuate long hole (81); It includes a fixing bolt (82) coupled to the tapped hole (61t) through the circular long hole (81).

As shown in Figures 4 and 6, when changing the angle of the angle adjustment arm 80, the angle adjustment arm 80 rotates around the boss 62, which is concentric with the center of the encoder shaft 42s. , When the angle adjustment arm 80 rotates, the belt 44 rotates together with the angle adjustment arm 80. At this time, since the rotary encoder 42 and the signal line 42w do not move, disconnection that may occur when the signal line 42w moves can be prevented.

After changing the angle of the angle adjustment arm 80, the changed angle of the angle adjustment arm 80 can be maintained by strongly tightening the loosened fixing bolt 82 again. When the angle of the angle adjustment arm 80 is changed, the angle between the pole 30 and the angle adjustment arm 80 is changed, and the center distance between the measuring wheel 40 and the pole 30 can be changed.

For example, the circular long hole 81 can be composed of a pair concentric with the boss 62, and since the center of the circular long hole 81 and the center of the tapped hole 61t coincide, the fixing bolt 82 When loosening and rotating the angle adjustment arm (80), the angle adjustment arm (80) and the fixing bolt (82) do not interfere with each other.

The rotation angle of the angle adjustment arm 80 can be limited depending on the length of the circular hole 81. That is, when the angle adjustment arm 80 is rotated, if the end of the arcuate hole 81 is caught by the fixing bolt 82, the angle adjustment arm 80 stops rotating and the rotation angle of the angle adjustment arm 80 is limited.

Since the center of the encoder shaft (42s) and the rotation center of the angle control arm (80) coincide with each other, when the angle control arm (80) is rotated, the rotary encoder (42) does not move and only the belt (44) moves on the angle control arm ( 80).

If the wheel bearing 46 is installed at the center of the measuring wheel 40, the measuring wheel 40 can rotate smoothly and precisely. For this purpose, a bearing press-fit hole (40h) for press-fitting the outer ring of a pair of wheel bearings (46) is formed at the center of the left and right sides of the measuring wheel (40), and the wheel shaft (45) supported on the wheel bearing (46) is formed. Insert it into the center of the inner ring of the wheel bearing (46).

The configuration for installing the wheel shaft 45 on the angle adjustment arm 80 includes forming center tapped holes 45t at the centers of both ends of the wheel shaft 45, as shown in FIG. 6, and forming the angle adjustment arm 80. ), a circular hole (80h) whose center coincides with the center tapped hole (45t) is formed in the lower part of the wheel, and then the female fixing bolt (83) is connected to the center tapped hole (45t) on one side through the circular hole (80h). The shaft 45 is installed at a right angle to the bottom of the angle adjustment arm 80.

In order to prevent the angle adjustment arm (80) and the driving pulley (41) from contacting each other, a flange (45p) is formed on one side of the outer peripheral surface of the wheel shaft (45) between the angle adjustment arm (80) and the wheel bearing (46). The flange (45p) can be positioned.

In order to prevent the measuring wheel 40 from being separated from the wheel shaft 45, the shaft fixing bolt 47 is coupled to the center tapped hole 45t on the other side so that the bolt head of the shaft fixing bolt 47 is connected to the wheel bearing (46). ) on the inner ring.

The present invention includes a bearing support hole (61h) penetrating through the center of the disk 61 and the boss 62; A small diameter bearing (63) inserted into the bearing support hole (61h) and supporting the end of the encoder shaft (42s); It includes a belt interference prevention groove 64 formed at the corner where the disk 61 and the upper semicircle 60 meet.

The outer ring of the small diameter bearing 63 installed in the bearing support hole 61h can be press-fitted or adhered to the bearing support hole 61h.

The belt interference prevention groove 64 prevents the belt 44, which rotates with the angle adjustment arm 80, from interfering with the corner of the upper semicircular groove 65 when changing the angle by rotating the angle adjustment arm 80. It is for this purpose.

The present invention includes a bent portion 51 formed on an eccentric bracket 50; It is formed on the eccentric bracket 50 and includes a wire sagging prevention hole 50h through which the signal line 42w passes.

The upper part of the eccentric bracket 50 forms an obtuse angle due to the bent portion 51. That is, the angle adjustment arm 80 is tilted to one side with respect to the pole 30 by the bent portion 51.

The wire sagging prevention hole 50h is used to wire the signal line 42w drawn out from the rotary encoder 42 to the wire outlet hole 31h formed in the end cap 31, as shown in FIGS. 4 and 8 to 10. For this purpose, the signal line (42w) drawn from the rotary encoder (42) is inserted into the upper part of the wire sagging prevention hole (50h) and drawn out to the lower part, and then the wire hole (50a) formed in the eccentric bracket (50) and the end cap (31) are inserted into the upper part of the wire sagging prevention hole (50h). ) and wire it by inserting it into the wire outlet hole (31h) formed in .

The signal line 42w inserted into the wire outlet hole 31h of the end cap 31 passes through the center of the pole 30 and then connects the microcontroller 90 and the power supply unit (not shown) installed inside or outside the pole 30. ) is connected to.

Hereinafter, the operation according to the present invention will be described in detail based on the attached drawings.

In the process of changing the angle of the angle adjustment arm 80, as shown in FIG. 4, the angle adjustment arm 80 can be rotated around the boss 62 by loosening the fixing bolt 82. At this time, when the angle adjustment arm 80 is rotated, the measuring wheel 40 and the driving pulley 41 rotate along the angle adjustment arm 80, and the belt 44 also rotates the angle adjustment arm (43) around the driven pulley 43. 80).

Since the rotary encoder 42 and the signal line 42w do not move while the angle adjustment arm 80 rotates, disconnection of the signal line 42w due to movement does not occur.

After the angle of the angle adjustment arm (80) is changed, if the loose fixing bolt (82) is tightened, the angle adjustment arm (80) maintains the changed angle.

On the other hand, when measuring the length of the crack 21 occurring in the structure 20 using the measuring wheel 40 and the rotary encoder 42, pressing the zero point switch (SW1) as shown in FIG. 11 causes seven- The value output to the segment module 92 is set to '0'.

Thereafter, when the measuring wheel 40 is brought into close contact with the cracked part 21 and rolled along the cracked part 21, the measuring wheel 40 and the driving pulley 41 are rotated, and the rotational force generated from the driving pulley 41 is transferred to the belt. It is transmitted to the encoder shaft (42s) through (44) and the driven pulley (43), and a pulse waveform is output from the rotary encoder (42) by rotation of the encoder shaft (42s).

The pulse waveform output from the rotary encoder 42 is transmitted to the input port of the microcontroller 90 through the signal line 42w, and the microcontroller 90 counts the input pulse waveform, stores it in memory, and then performs seven-segment The counted value is output in real time through the module 92 to display the crack length.

20: Structure 21: Crack portion
30: Pole 31: End cap
31h: wire outlet 40: measuring wheel
41: driving pulley 42: rotary encoder
42w: signal line 42s: encoder axis
43: driven pulley 44: belt
50: Eccentric bracket 50a: Wire hole
50h: Wire sagging prevention hole 51: Bend part
60: upper semicircular body 61: disk
61t: Tap hole 61h: Bearing support hole
62: Boss 63: Small diameter bearing
64: Belt interference prevention groove 70: Lower semicircular body
80: Angle adjustment arm 81: Circular long hole
82: fixing bolt

Claims (3)

A pole (30) having a certain length;
An end cap (31) installed at the end of the pole (30) and having a wire outlet hole (31h);
A measuring wheel (40) rolling along the crack (21) occurring on the surface of the structure (20);
A driving pulley 41 installed on the measuring wheel 40;
a rotary encoder 42 having a signal line 42w passing through the wire outlet hole 31h and detecting the rotation speed of the measuring wheel 40;
a driven pulley (43) installed on the encoder shaft (42s) of the rotary encoder (42);
A belt 44 that transmits power from the driving pulley 41 to the driven pulley 43;
In the crack length measuring device for structural safety diagnosis including,

An eccentric bracket (50) installed on the end cap (31) and extending to one side;
a wire hole (50a) formed in the eccentric bracket (50) so that its center coincides with the wire outlet hole (31h);
An upper semicircular body (60) installed on the eccentric bracket (50) and in close contact with the upper outer peripheral surface of the rotary encoder (42);
A lower semicircular body (70) coupled to the upper semicircular body (60) and in close contact with the lower outer peripheral surface of the rotary encoder (42);
A disk 61 formed on one side of the upper semicircular body 60;
A boss 62 protruding from the center of the disk 61;
An angle adjustment arm (80) supported on the boss (62) and having a rotation center concentric with the encoder shaft (42s);
An arcuate long hole (81) formed in the angle adjustment arm (80);
A tap hole (61t) formed in the disk (61) along the arcuate long hole (81);
A fixing bolt (82) coupled to the tapped hole (61t) through the arcuate long hole (81);
A crack length measuring device for structural safety diagnosis comprising a. According to clause 1,
a bearing support hole (61h) penetrating through the center of the disk (61) and the boss (62);
A small diameter bearing (63) inserted into the bearing support hole (61h) and supporting an end of the encoder shaft (42s);
a belt interference prevention groove 64 formed at a corner where the disk 61 and the upper semicircular body 60 meet;
A crack length measuring device for structural safety diagnosis comprising a. According to clause 1,
A bent portion 51 formed on the eccentric bracket 50;
a wire sagging prevention hole (50h) formed in the eccentric bracket (50) through which the signal line (42w) passes;
A crack length measuring device for structural safety diagnosis comprising a.

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