JP4190340B2 - Anchor bolt corrosion thinning diagnostic method and apparatus used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for diagnosing corrosion thinning of an anchor bolt and an apparatus used therefor.
[0002]
[Prior art]
In general, various steel structures such as road lighting pillars, sign pillars, sound insulation walls, buildings, tower structures, and the like are often fixed to a concrete foundation with anchor bolts via a base plate or the like. However, this anchor bolt may corrode with long-term use due to repeated water retention, drying, etc., and its cross-section may be worn (thinned), which may cause problems with the safety of the structure. Has occurred. Therefore, in order to ensure safety, it is important to grasp the state of corrosion thinning in order to clarify the replacement time of the anchor bolt.
[0003]
Conventionally, in order to investigate the corrosion thinning of the anchor bolt, the structure and base plate are removed, the anchor bolt head is exposed from the concrete foundation, and then the diameter of this exposed head is actually measured. A method for directly measuring the corrosion thinning situation has been carried out. However, with this method, not only is the work large, but depending on the structure, it may be difficult to remove, and corrosion thinning may not be measured.
[0004]
On the other hand, in order to non-destructively diagnose the corrosion state of the tensile steel material of the anchor, a method of diagnosing the corrosion state by passing a current through the tensile steel material of the anchor and measuring its natural potential has been proposed (for example, (See Patent Document 1).
[0005]
[Patent Document 1]
JP-A-11-201930 (paragraphs [0012] to [0023])
[0006]
[Problems to be solved by the invention]
However, the above method cannot diagnose the corrosion thinning state of the anchor bolt outcrop.
[0007]
The present invention has been made in view of such circumstances, and the anchor bolt corrosion thinning that can diagnose the corrosion thinning situation of the anchor bolt outcrop while the structure is left as it is. The object is to provide a diagnostic method and a device used therefor.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a base plate that is embedded in a concrete foundation with its head exposed from a concrete foundation, and the outcrop is inserted into a bolt insertion hole of the base plate and mated with a nut. a method of diagnosing a corrosion thinning of the anchor bolt to fix the structure above, remove the nut from the anchor bolt to be measured, a portion of the head of the outcrop to luer Nkaboruto is striking vibration from the base plate, the The vibration vibration sound that is sometimes generated is recorded with a non-contact type sound collecting microphone, and the natural vibration frequency of the anchor bolt is measured from the recorded vibration vibration sound. It was compared to the natural frequency of the anchor bolt, and corrosion thinning amount in the base plate insertion portion of the anchor bolt A method of diagnosing corrosion thinning of the anchor bolt so as also to diagnose the degree of unhealthy degree the first aspect, embedded in the concrete foundation head while being outcrop from concrete foundation, the A device for diagnosing corrosion thinning of an anchor bolt that fixes a structure on the base plate by inserting an outcrop portion into the bolt insertion hole of the base plate and mating with the nut, and the anchor bolt is removed from the base plate when the nut is removed The vibration applying means for striking and vibrating the head part of the head and the vibration sound generated when the anchor bolt is subjected to the striking vibration by the vibration applying means are recorded with a non-contact type sound collecting microphone. measuring means for measuring the natural frequency of the anchor bolt, the measurement results and measured by the measuring means, the positive input in advance By comparing the natural frequency of the natural frequency and thinning anchor bolt such anchor bolt, a computing device that is configured to calculate the corrosion thinning of the base plate insertion portion of the anchor bolt, which is the calculated A second aspect of the present invention is a diagnostic apparatus for corrosion thinning of an anchor bolt provided with a display unit for diagnosing and displaying the amount of corrosion thinning and the degree of unsoundness .
[0009]
That is, according to the diagnostic method of corrosion thinning of an anchor bolt of the present invention, the nut portion is removed and the head portion of the anchor bolt which is exposed from the base plate is subjected to a hammering vibration, and the natural frequency of the anchor bolt at this time is measured. Compare the measurement result with the natural frequency of normal anchor bolts, and diagnose the degree of unsoundness along with the amount of corrosion thinning (diameter of the corroded anchor bolt) at the base plate insertion part of the anchor bolt. It is the method. Therefore, in the method of the present invention, it is not necessary to remove the structure or the base plate and check whether the base plate insertion portion of the anchor bolt is actually corroded, and the structure and the base plate are left as they are. In the state, it can be diagnosed whether the anchor bolt in the base plate insertion portion is thinned by corrosion. In addition, the head of the anchor bolt is vibrated with a hammer or the like, and the natural frequency of the anchor bolt at this time can be measured with a sound collecting microphone, so that the work can be performed in a short time with a small device. On the other hand, according to the anchor bolt corrosion thinning diagnostic apparatus of the present invention, the diagnostic method of the present invention having the above-described excellent effects can be easily realized.
[0010]
In the above diagnosis, the natural frequency of the normal anchor bolt embedded in the concrete foundation with the head exposed from the concrete foundation is solved by the bending vibration of the beam fixed to the elastic body. It can be obtained from the calculation formula. In this case, the measured values or known values of normal local anchor bolts can be adopted as Young's modulus, concrete elastic modulus (spring constant), and the like. Similarly, the natural frequency of the anchor bolt in which the diameter of the predetermined portion is formed thin (thinned by processing or the like) can also be obtained by a theoretical calculation formula. Further, these theoretical calculation values can be verified by using a normal anchor bolt and an anchor bolt having a predetermined portion with a narrow diameter, and a measured value actually measured by an experiment. Moreover, you may compare the measurement result of this invention with only the measured value measured by the said experiment.
[0011]
In addition, the natural frequency of the anchor bolt is determined by the diameter d of the anchor bolt and the length (outcrop length) L (the ratio of the outcrop length L to the diameter d of the head portion of the anchor bolt exposed from the concrete foundation: L / D is referred to as an aspect ratio) (see FIG. 3). As shown in FIG. 4, the diameter d of the portion of the anchor bolt that has undergone corrosion thinning at the base plate insertion portion is smaller than that of a normal anchor bolt (that is, the aspect ratio is large). ), The natural frequency of anchor bolts with reduced corrosion is lower than normal.
[0012]
Therefore, in consideration of the following, the degree of unsoundness can be diagnosed together with the corrosion thinning amount of the anchor bolt. That is, in the case of anchor bolts having the same outcrop length L and diameter d, the lower natural frequency is measured in the anchor bolt in which the portion inserted through the insertion hole of the base plate 2 is corrosion-reduced (FIG. 5). reference). Further, when the diameter d is the same and the outcrop length L is different, it can be compared with a theoretical calculation value for each outcrop length L or a measured value actually measured by an experiment. In addition, the natural frequency (theoretical calculation value or the measurement value actually measured by experiment) of the anchor bolt formed with a narrow diameter of the predetermined portion is compared with the measurement value measured by the present invention, so that the anchor bolt reduced in corrosion is thinned. (That is, the amount of corrosion thinning) can be obtained (for the description of the reference numerals in FIGS. 3 to 5, refer to the embodiments described later ) .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 shows an embodiment of a method for diagnosing corrosion thinning of an anchor bolt according to the present invention. In the drawing, 1 is a concrete base, 2 is a flat plate-like structure base plate disposed on the upper surface of the concrete base 1, and a plurality of bolt insertion holes 2a (only two are shown in FIG. 1). )) Has been drilled. Reference numeral 3 denotes an anchor bolt (see FIG. 3) embedded in the concrete base 1, and the outcrop head of the concrete base 1 (the head bolt portion of the anchor bolt 3 that is exposed from the concrete base 1) 3 a is the base plate. 2 is inserted into the bolt insertion holes 2a and is exposed from the bolt insertion holes 2a. Reference numeral 4 denotes a structure such as an illumination column welded and fixed to the upper surface of the base plate 2, and a plurality of leg plates 4 a welded and fixed to the outer peripheral surface of the lower end thereof are welded and fixed to the upper surface of the base plate 2. Yes. In use, the nuts 8 and 9 (see FIG. 2) are engaged with the threaded portion 3b formed on the outcrop 3a of the anchor bolt 3 so that the structure 4 is attached to the base 1 made of concrete. 2 and fixed by an anchor bolt 3.
[0015]
Reference numeral 11 denotes a corrosion thinning measuring device, which strikes the outer peripheral surface of the upper end edge of the exposed head 3a of the anchor bolt 3 to give impact vibration to the exposed head 3a (the hitting portion 12a of the test hammer 12 is made of iron or plastic). A condenser microphone 13 that records the sound (ie, the vibration sound of the outcrop 3a) that is generated when the test hammer 12 gives a striking vibration and converts the recorded sound pressure signal into an electrical signal, and the condenser An FFT (Fast Fourier Transform) analyzer (not shown) that converts an electrical signal input from the microphone 13 into a vibration waveform and a vibration spectrum, and the anchor bolt 3 based on the vibration waveform and vibration spectrum input from the FFT analyzer. The natural frequency is determined and the diameter d and the outcrop length L of the anchor bolt 3 input in advance are determined. From theoretical calculation value of the anchor bolt 3 the diameter of the theoretically calculated value or the base plate insertion portion of the normal anchor bolt 3 calculated is formed thinner from measuring the corrosion thinning of the measured anchor bolt 3, quantify or graph An arithmetic device (not shown) such as a personal computer (PC) to be realized. In the figure, reference numeral 13 a denotes a sound collection port of the condenser microphone 13.
[0016]
Using the above-described corrosion thinning measuring apparatus 11, for example, corrosion thinning can be diagnosed as follows. First, the nuts 8 and 9 (see FIG. 2) are removed from the exposed head 3a of the anchor bolt 3 (see FIG. 1). Next, the diameter d of the anchor bolt 3 is measured (or checked by a construction design document or the like) and input to the arithmetic unit. Further, the length of the anchor bolt 3 that is exposed from the base plate 2 and the thickness of the base plate 2 are measured (see FIG. 4), and the length of the exposed head 3a of the anchor bolt 3 that is exposed from the upper surface of the concrete base 1 (outcrop length L ) Is calculated and input to the arithmetic unit. Further, the sound collection port 13a of the condenser microphone 13 is positioned in the vicinity of the outer peripheral surface of the upper end edge of the outcrop 3a of the anchor bolt 3. Next, the outer peripheral surface of the upper end edge of the exposed head 3a of the anchor bolt 3 is hit by the test hammer 12 to give impact vibration to the exposed head 3a. At this time, the striking vibration sound emitted from the outcrop 3a is recorded by the condenser microphone 13, and the recorded sound pressure signal is converted into an electric signal and input to the FFT analyzer. In this FFT analyzer, the electric signal input from the condenser microphone 13 is converted into a vibration waveform and vibration spectrum, and then input to the calculation device, and the calculation device calculates the amount of corrosion thinning at the base plate insertion portion of the anchor bolt 3. The graph is displayed on the screen of the display unit provided in the arithmetic unit.
[0017]
The display section includes four types of natural frequency zones (A to D) determined from the input outcrop length L and diameter d (A zone: a safety zone that is considered to have little or no corrosion thinning). , B zone: Zone where corrosion is thinned slightly, but it is thought that replacement is not necessary yet, C zone: Danger zone where corrosion thinning is in progress and considered to need replacement, D zone: Corrosion reduced The zone where the meat is large and very dangerous is displayed, and it is possible to see at a glance which zone the calculated natural frequency is in (see Fig. 6. In Fig. 6, Fourier transform is performed). The measured spectrum waveform is displayed on the upper side and the TIME waveform of the sound pressure data is displayed on the lower side, and the calculated natural frequency is in the C zone). In this way, diagnosis and determination of corrosion thinning of the anchor bolt 3 can be performed mechanically (without depending on human judgment).
[0018]
As described above, in this embodiment, the nuts 8 and 9 are removed from the exposed head 3a of the anchor bolt 3 that is exposed from the concrete foundation 1, and the exposed head 3a is struck by the test hammer 12 to be oscillated. By measuring the vibration vibration sound at the time with the condenser microphone 13, it is possible to mechanically diagnose the corrosion thinning state of the anchor bolt 3. For this reason, it is not necessary to remove the structure 4 and the base plate 2 from the concrete foundation 1. Moreover, the exposed head 3a of the anchor bolt 3 is hit and vibrated with the test hammer 12, and the hitting vibration sound at this time is measured with the condenser microphone 13, so that the work can be performed in a short time with a small device.
[0019]
FIG. 7 shows a reference example of a method for diagnosing corrosion thinning of an anchor bolt according to the present invention. In this reference example , the natural frequency of the outcrop 3a is measured by the acceleration pick-up 15 provided on the upper end surface of the outcrop 3a when a hammering vibration is applied to the outcrop 3a of the anchor bolt 3 by the test hammer 12. The measurement result is input to the FFT analyzer via a charge amplifier (not shown). Other parts are the same as those in the above embodiment, and the same reference numerals are given to the same parts. This reference example also has the same operations and effects as the above embodiment.
[0020]
In the above embodiment, instead of the theoretical calculation value of the normal anchor bolt 3 and the theoretical calculation value of the anchor bolt 3 in which the diameter of the predetermined portion is thin, the measurement value actually measured by experiment (that is, actually measured by experiment). The natural frequency of the normal anchor bolt 3 and the natural frequency of the anchor bolt 3 having a predetermined portion with a small diameter may be used.
[0021]
【The invention's effect】
That is, according to the method for diagnosing anchor bolt corrosion thinning according to the present invention, there is no need to remove the structure or base plate and check whether the anchor bolt base plate insertion portion is actually corrosion thinned. In the state where the base plate and the like are left as they are, the degree of unsoundness can be diagnosed together with the corrosion thinning amount of the anchor bolt in the base plate insertion portion . In addition, the head of the anchor bolt is vibrated with a hammer or the like, and the natural frequency of the anchor bolt at this time can be measured with a sound collecting microphone, so that the work can be performed in a short time with a small device. On the other hand, according to the anchor bolt corrosion thinning diagnostic apparatus of the present invention, the diagnostic method of the present invention having the above-described excellent effects can be easily realized.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an embodiment of a method for diagnosing corrosion thinning of an anchor bolt according to the present invention.
FIG. 2 is an explanatory diagram of the diagnostic method.
FIG. 3 is a cross-sectional view showing a normal anchor bolt.
FIG. 4 is a cross-sectional view showing an anchor bolt that has undergone corrosion thinning.
FIG. 5 is an explanatory diagram of the diagnostic method.
FIG. 6 is an explanatory diagram of waveforms displayed on the display unit.
FIG. 7 is an explanatory view showing a reference example of a method for diagnosing corrosion thinning of an anchor bolt according to the present invention.
[Explanation of symbols]
1 concrete foundation 3 anchor bolt 3a outcrop

Claims (3)

Corrosion reduction of anchor bolts, which are embedded in a concrete foundation with the head exposed from the concrete foundation, and the outcrop head is inserted into the bolt insertion hole of the base plate and mated with the nut, thereby fixing the structure on the base plate. a method of diagnosing the meat, remove the nut from the anchor bolt to be measured, a portion of the head of the outcrop to luer Nkaboruto is striking vibration from the base plate, a non-contact type pickup striking vibration sound emanating at this time Recorded with a microphone, measured the natural frequency of the anchor bolt from the recorded impact vibration sound, and compared the measurement result with the natural frequency of the normal anchor bolt and the natural frequency of the thinned anchor bolt, to diagnose the degree of unhealthy degree with corrosion thinning amount in the base plate insertion portion of the anchor bolt Diagnostic method for corrosion thinning of the anchor bolt, characterized in that it has. Corrosion reduction of anchor bolts, which are embedded in a concrete foundation with the head exposed from the concrete foundation, and the outcrop head is inserted into the bolt insertion hole of the base plate and mated with the nut, thereby fixing the structure on the base plate. A device for diagnosing meat, a vibration applying means for striking and vibrating the head portion of the anchor bolt that is exposed from the base plate with the nut removed, and a blow that is generated when the anchor bolt is vibrated by the vibration applying means Measurement means for recording vibration sound with a non-contact sound collecting microphone and measuring the natural frequency of the anchor bolt from the recorded impact vibration sound, measurement results measured by this measurement means, and normal input normal by comparing the natural frequency of the natural frequency and thinning anchor bolt anchor bolt, the anchor An arithmetic unit that is configured to calculate the corrosion thinning of the base plate insertion portion of the belt, further comprising a display unit for displaying diagnose the degree of the calculated corrosion thinning amount and unhealthy degree A diagnostic device for corrosion thinning of anchor bolts.   The apparatus for diagnosing corrosion thinning of an anchor bolt according to claim 2, wherein the vibration applying means is a hammer.

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