JP2018009354A - Viaduct state monitoring apparatus and viaduct state monitoring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viaduct state monitoring apparatus and state monitoring method, capable of evaluating whether or not abnormality has occurred at a pile head of a pillar positioned in the vicinity of an underground beam, a foundation, without using visual confirmation.SOLUTION: A viaduct state monitoring apparatus for a viaduct A including an underground beam 3 and pile foundation 2, foundations, a pillar 4 fixed on the underground beam 3, and an upper floor beam 5 fixed on the crown of the pillar 4 comprises: a vibration measurement instrument 11, installed on a pillar base part 10 of the pillar 4 positioned in the vicinity of the underground beam 3 and pile foundation 2, for measuring a vibration obtained by striking or vibrating the pillar base part 10; calculation recording means 13 for calculating and recording a natural frequency in a pile head secondary mode on the basis of a detection value from the vibration measurement instrument 11; and evaluation means 14 for monitoring whether or not reduction in the natural frequency in the pile head secondary mode has occurred on the basis of output from the calculation recording means 13 to perform structure soundness determination by evaluating a damage state of the pile foundation 2 of the viaduct on the basis of a monitoring result.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a soundness evaluation method that can be applied to a concrete structure such as a railway ramen viaduct to efficiently check the presence or absence of damage to a pile foundation including a pile head generated after an earthquake.

In the railway ramen viaduct currently in service, the result of soundness diagnosis when damaged by an earthquake is an important indicator of train operation and early restart.
Therefore, as a technique (health evaluation technique) capable of non-destructively and quantitatively evaluating the degree of stability related to the stability of the railway ramen viaduct, it was obtained by striking the bridge axis perpendicular direction of the pier top with a weight of about 30 kg. An impact vibration test for evaluating the damage level from the magnitude of the natural frequency of the primary natural vibration mode has been established.

Specifically, in “Research on soundness evaluation method of RC ramen viaduct” shown in Non-Patent Document 1, the natural frequency and vibration mode of the pier are obtained from the response when the top of the pier is hit with a weight. The basis soundness is determined by these values.
In addition, in “Research on damage level evaluation of RC ramen viaduct during earthquake” shown in Non-Patent Document 2, when RC ramen viaduct is damaged by an earthquake, recovery measures are determined according to the damage level and countermeasures are taken. Therefore, paying attention to the phenomenon that the natural frequency decreases when the structure is damaged, the damage level of the structure is evaluated.
As a result, Non-Patent Document 2 calculates the plasticity rate of the column end where damage occurred during an earthquake based on the numerical analysis result of the primary natural frequency of the entire system obtained by performing the impact vibration test by hitting the hanging arrow. The overall damage level can be evaluated based on the calculation result.

On the other hand, as a state monitoring system capable of evaluating the soundness of a pier over time, a technique disclosed in Patent Document 1 is provided.
The state monitoring system disclosed in Patent Document 1 uses the first frequency as the upper limit as an index value of the soundness of the pier from the waveform indicating the magnitude of vibration for each frequency obtained from the vibration information of the sensor. A power spectrum area ratio, which is a ratio of the waveform area in the frequency range and the waveform area in the frequency range up to a second frequency greater than the first frequency, is calculated.
In Patent Document 1, for example, by monitoring the correlation between the power spectrum area ratio and the natural frequency by the impact vibration test, it is possible to evaluate the soundness of the bridge pier over time and over time.

JP-A-2015-230206

Akihiko Nishimura: Research on the method for evaluating the soundness of ramen viaducts Railway Research Institute Report Vol.4, No.9, pp14-21, September 1990 Masaki Seki, Akihiko Nishimura, Hiroyuki Sano, Atsushi Nakano: A study on evaluation of damage level of RC ramen viaduct during earthquake No.731 / I-63, pp51-64, April 2003

The natural frequency of the primary vibration mode shown in the above-mentioned non-patent literature or the power spectrum area ratio shown in the patent literature can be used as a health diagnostic index in the entire ramen viaduct that is damaged during an earthquake.
However, in ramen viaduct columns with pile foundations, the pile heads buried in the ground may have been damaged greatly by earthquakes, and the assessment of the soundness of the viaduct under such circumstances There were many unknowns, and there was room for further study.
That is, in the research of the above-mentioned literature, the situation of pile foundation damage is not taken into consideration, and it is not certain whether similar vibration characteristics are exhibited even in a state where damage is caused to the pile foundation member due to an earthquake.

As a result, the current confirmation method is to dig up the pile foundation part and visually check it, and it is difficult to implement in practice. In addition, many of the existing railway ramen viaducts that have been used for many years have been built, and there is a high possibility that many structures are aging. Establishment is required.
In particular, the pile foundation including the pile head is difficult to visually confirm even if there is a risk of damage, so a soundness evaluation method that replaces visual inspection is required.

  This invention was made in view of the above-mentioned circumstances, and is capable of evaluating whether or not an abnormality has occurred in the pile foundation including the pile head, without visual confirmation, and monitoring the state of the viaduct. An apparatus and a state monitoring method are provided.

In order to solve the above problems, the present invention proposes the following means.
The state monitoring device of the present invention is a ramen viaduct having a pile and underground beam as a foundation, a column fixed to the foundation, and an upper floor beam fixed to the top end of the column. A vibration measuring instrument that is installed at the base of a column located in the vicinity of the pile foundation and measures vibration obtained by striking or oscillating the column base, and a pile head 2 based on the detection value output from the vibration measuring instrument The operation recording means for calculating and recording the natural frequency of the next mode, and monitoring whether or not the natural frequency of the pile head secondary mode has decreased based on the output from the operation recording means, and the monitoring result And evaluation means for determining damage to the viaduct pile foundation.

And in the viaduct state monitoring device configured as described above, vibration obtained by striking or oscillating the base of the pillar near the underground beam and the pile foundation is a vibration measuring instrument installed at the base of the pillar. Is detected.
Thereby, the calculation recording means calculates and records the natural frequency of the pile head secondary mode based on the detected value obtained by the vibration measuring instrument, and then the evaluation means calculates the pile head based on the output from the calculation recording means. It is monitored whether or not the natural frequency of the secondary mode has been lowered, and damage to the pile foundation of the viaduct is determined based on the monitoring result.
As a result, the state monitoring device can evaluate whether or not an abnormality has occurred in the pile foundation portion serving as the foundation of the viaduct based on the detection value output from the vibration measuring instrument, without visual confirmation.

  In the present invention, the vibration measurement device measures the striking vibration hitting the vicinity of the column base with a hanging arrow or the like.

  Moreover, in the present invention, the forced vibration of the structure due to sweep excitation from a vibrator installed near the column base is measured by the vibration measuring instrument.

  And in the viaduct state monitoring device configured as described above, the vibration obtained by striking the base of the column near the underground beam and the pile foundation with a hanging arrow or using the vibrator is generated on the base of the column. Detected by installed vibration measuring instrument. Thereby, based on the detected value output from a vibration measuring device, it can be evaluated whether abnormality has arisen in the column base located in the vicinity of the underground beam and pile foundation used as a foundation.

  In addition, the state monitoring device of the present invention includes a pile and underground beam as a foundation, a column fixed to the foundation, and an upper floor beam fixed to the top end of the column. A microtremor measuring instrument installed at the base of a column located near the beam and the head of the pile to measure vibrations caused by microtremors at the base of the pillar, and a secondary mode of the pile head based on the detection value output from the microtremor measuring instrument A calculation recording means for calculating and recording evaluation elements such as power spectrum area ratio, dominant frequency, etc., and whether or not a change has occurred in the evaluation element in the pile head secondary mode based on the output from the calculation recording means And an evaluation means for monitoring and determining damage to the viaduct pile foundation based on the monitoring result.

And, in the viaduct state monitoring device configured as described above, the vibration is caused by the fine movement of the column base that is installed in the column base located near the underground beam and the pile foundation, and is always installed in the column base. It is detected by a fine movement measuring instrument.
Thereafter, the calculation recording means calculates and records evaluation elements such as the power spectrum area ratio and the dominant frequency in the pile head secondary mode based on the detection value obtained by the microtremor measurement device, and then the evaluation means calculates the calculation. Based on the output from the recording means, it is monitored whether or not a change has occurred in the evaluation element in the pile head secondary mode, and damage to the pile foundation of the viaduct is determined based on the monitoring result.
As a result, in the state monitoring device, it is possible to evaluate whether or not an abnormality has occurred in the pile foundation portion based on the detection value output from the microtremor measurement device at all times, without visual confirmation.

  In the present invention, the continuous fine movement measuring device detects fine movement of the pier due to wind or the like.

  And in the viaduct state monitoring apparatus comprised as mentioned above, the fine movement of the bridge pier by a wind etc. is detected with the vibration measuring device installed in the base of the pillar located in the vicinity of an underground beam and a pile foundation. Thereby, based on the detection value output from a vibration measuring device, it can be evaluated whether abnormality has arisen in the pile foundation part.

  Further, the state monitoring method of the present invention includes a ground bridge and a pile foundation as a foundation, a column fixed to the foundation, and an upper floor beam fixed to the top end of the column. A measurement stage for measuring vibrations obtained by striking or oscillating the column base installed at the base of the column located near the beam and pile foundation, and a pile head 2 based on the detection value detected in the measurement stage A calculation stage for calculating and recording the natural frequency of the next mode, and whether or not the natural frequency of the pile head secondary mode has been reduced is monitored based on the calculation result in the calculation stage. And an evaluation stage for determining damage to the viaduct pile foundation.

And in the viaduct state monitoring method comprised as mentioned above, the vibration obtained by striking or oscillating the base of a pillar in the vicinity of an underground beam and a pile foundation in a measurement step is detected.
After that, in the calculation recording stage, the natural frequency of the pile head secondary mode is calculated and recorded based on the detection value obtained in the measurement stage, and then in the evaluation stage, the pile head secondary is calculated based on the output from the calculation recording stage. It is monitored whether or not the natural frequency of the mode has decreased, and damage to the pile foundation of the viaduct is determined based on the monitoring result.
As a result, in the state monitoring method, it is possible to evaluate whether or not an abnormality has occurred in the pile foundation based on the detection value obtained at the measurement stage, without visual confirmation.

  Further, the state monitoring method of the present invention includes a ground bridge and a pile foundation as a foundation, a column fixed to the foundation, and an upper floor beam fixed to the top end of the column. A measurement stage that is installed at the base of a column located in the vicinity of the beam and pile foundation and measures vibration due to microtremors of the column base, and a power spectrum area in the secondary mode of the pile head based on the detection value detected at the measurement stage A calculation recording stage for calculating and recording evaluation elements such as ratio and dominant frequency, and monitoring whether or not a change has occurred in the evaluation elements in the pile head secondary mode based on the calculation result in the calculation recording stage; And an evaluation stage for judging damage to the pile foundation of the viaduct based on the monitoring result.

And in the viaduct state monitoring method comprised as mentioned above, the vibration by the continuous fine movement of a column base part is detected in a measurement step.
Thereafter, in the calculation recording stage, after calculating and recording evaluation elements such as the power spectrum area ratio and the dominant frequency in the pile head secondary mode based on the detection values obtained in the measurement stage, the calculation recording stage Whether or not the evaluation element in the pile head secondary mode has changed is monitored based on the output from the pile, and damage to the pile foundation of the viaduct is determined based on the monitoring result.
As a result, in the state monitoring method, it is possible to evaluate whether or not an abnormality has occurred in the pile foundation based on the detection value obtained at the measurement stage, without visual confirmation.

  According to the present invention, it is possible to evaluate whether or not an abnormality has occurred in the pile foundation including the pile head, based on the detection value output from the vibration measuring instrument, regardless of visual confirmation.

It is a figure which shows schematic structure of embodiment which concerns on this invention, Comprising: (A) is a figure at the time of hit | damaging a pillar base part with a hammer, (B) is a figure at the time of vibrating a pillar base part with a vibrator. . It is explanatory drawing which shows the vibration mode of a pile, Comprising: (A) is a figure which shows the whole primary mode at the time of hit | damaging a pillar top end, (B) is the pile head secondary mode at the time of hit | damaging the column base vicinity. FIG. It is a graph which shows the correlation with the frequency of the vibration mode of the whole primary and pile head secondary, and the rigidity reduction rate of a column. It is a figure which shows the Fourier spectrum obtained from the measurement result of the accelerometer when the pillar base was hit with a hammer or a vibrator. It is a graph which shows the relationship between the frequency and amplitude at the time of hitting a pillar base part normally or weakly. It is a figure which shows the hanging condition of a pile head. 8 is a graph showing fluctuations in the vibration spectrum before and after the suspension, where (A) shows a case where an impact vibration test is performed, and (B) shows a case where an exciter test is performed. It is a schematic block diagram of the state monitoring apparatus used in Experimental example 2. It is the graph which showed the power spectrum with respect to a Fourier amplitude spectrum as a vibration frequency and the vertical axis | shaft as a square value of an amplitude. It is a graph which shows the fluctuation | variation of the power spectrum area ratio in the whole primary mode measured at the fixed time interval. It is a graph which shows the fluctuation | variation of the dominant frequency in the whole primary mode measured at the fixed time interval. It is a graph which shows the relationship between the frequency | count of a measurement in a pile head secondary mode, and a power spectrum area ratio. It is a graph which shows the relationship between the frequency | count of a measurement in a pile head secondary mode, and a dominant frequency.

An embodiment of the present invention will be described with reference to FIGS.
1A and 1B show a concrete structure 1 applied to this embodiment.
The concrete structure 1 mainly includes an underground beam 3 having a pile foundation 2, a column 4 fixed to the underground beam 3, and an upper floor beam 5 fixed to the top end of the column 4. The element is the ramen viaduct A.

The underground beam 3 is a portion that receives a load from the column 4 and is a rod-like structure constructed by cast-in-place concrete.
The underground beam 3 is connected to and supported by the pile foundation 2 and transmits the load from the pillar 4 to the pile foundation 2. The pile foundation 2 is a foundation part for supporting the entire concrete structure 1, and transmits the load from the underground beam 3 to the ground G via the pile head located at the connection point with the underground beam 3. To do.
The pile foundation 2 is, for example, a cast-in-place concrete pile constructed by inserting a reinforcing bar into a hole having a predetermined depth excavated by an excavating machine and driving in concrete.

The column 4 is a portion that supports the upper floor beam 5 and is a bridge pier such as a reinforced concrete column that is constructed at a predetermined interval and arranged in the vertical direction.
The upper floor beam 5 is a part that supports the track R and functions as a roadbed (base), and is a slab PC girder constructed by cast-in-place concrete and arranged in the horizontal direction. A track R is laid on the upper surface of the upper floor beam 5.
The underground beam 3 having the pile foundation 2 is embedded under the ground G, and most of the columns 4 fixed to the underground beam 3 are exposed from the ground G.

  Next, with reference to FIGS. 1-11, the state monitoring apparatus 100 for evaluating the state of the pile foundation 2 of the said ramen viaduct A is demonstrated.

As shown in FIG. 1, the column base portion 10 is a joint portion of the column 4 fixed to the underground beam 3 and a portion located in the vicinity thereof (a section about 500 mm from the underground beam connection portion), and a part thereof It is exposed from the ground G.
The column base 10 located in the vicinity of the underground beam 3 and the pile foundation 2 is provided with a vibration measuring instrument 11 that measures vibrations obtained by hitting or vibrating the column base 10.

For example, a piezoelectric accelerometer is used as the vibration measuring instrument 11. Further, the acceleration data detected by the vibration measuring instrument 11 is supplied to the information processing apparatus C and the data is processed.
In the vibration measuring instrument 11, in addition to measuring the striking vibration hitting the vicinity of the column base 10 with a hanging arrow or the like as shown in FIG. 1 (A), as shown in FIG. Forced vibration of the concrete structure 1 due to sweep excitation from the installed vibrator 12 is measured.

As a technique that can quantitatively evaluate the stability of the stability of the railway ramen viaduct in a non-destructive manner, as shown in FIG. 2 (A), the direction perpendicular to the bridge axis at the top of the pier column (indicated by reference numeral 4A) is 30 kg. An impact vibration test has been established to evaluate from the natural frequency of the first natural vibration mode obtained by striking with a heavy weight, and has been proven to date.
As can be seen with reference to Non-Patent Documents 1 and 2 mentioned above, research on the damage level evaluation method using the impact vibration test at the time of the railway ramen viaduct earthquake was conducted, and the damage level of the column and the primary natural vibration were studied. Numbers are shown to be correlated. From this, the natural frequency of the primary vibration mode in the ramen viaduct is used by railway operators as a soundness diagnostic index in the event of an earthquake.
However, since it is not possible to determine whether or not damage has occurred in the vicinity of the underground beam and pile foundation only by measuring the primary natural frequency, in this example, as shown in FIG. The soundness diagnosis pays attention to the pile head secondary mode which vibrates around the pile head as well as the primary mode which vibrates around the column top end.

In the pre-analysis, an analysis model of the viaduct model was created, eigenvalue analysis was performed with the stiffness of the pile head lowered assuming that the pile head was damaged, and the sensitivity of the natural frequency in each vibration mode was analyzed.
With respect to the overall primary vibration mode, the sensitivity to the decrease in the stiffness of the pile is small, and the decrease in the natural frequency is not significant unless the stiffness decrease rate of the pile head reaches 10%. On the other hand, regarding the secondary vibration mode of the pile head, the ratio of the decrease in the natural frequency to the decrease in the rigidity of the pile head is large. This is a vibration mode in which the pile head is greatly deformed, as can be seen from the pile head secondary vibration mode shown in FIG. 2 (B). This is thought to be because it appeared with good sensitivity. For this reason, in addition to the primary mode that vibrates around the top of the pillar (natural frequency when healthy: 4.3 Hz), the secondary mode that vibrates around the pile head (natural frequency when healthy: 18.1 Hz) ) Is performed (a specific natural frequency is described later). In addition, regarding the analysis model of this time, when the analysis for reducing only the rigidity of the column is performed separately, it has been confirmed that there is a correlation between the natural frequency of the overall primary vibration mode and the rigidity reduction rate of the column.

  The information processing apparatus C shown in FIG. 1 includes a calculation recording means 13 for calculating and recording the natural frequency of the pile head secondary mode based on the detection data output from the vibration measuring instrument 11, and the calculation recording means 13 And an evaluation means 14 for monitoring whether or not the natural frequency of the pile head secondary mode has been lowered based on the output from the bridge and determining damage to the viaduct pile foundation 2 based on the monitoring result. .

In addition, in order to determine the damage degree of the pile foundation 2 shown below, an example of “evaluation of the soundness of the pile foundation 2 by forced vibration (striking with a hammer, vibrator)” is shown in Experimental Example 1. In Experimental Example 2, an example of “evaluation of soundness of pile foundation 2 using microtremors” is shown.
In Experimental Examples 1 and 2, a reinforced concrete structure simulating one span of the ramen viaduct was created, and a test structure with four bladed steel pipe piles as the foundation type was used.
In addition, the pile head (about 500 mm from the underground beam connection) concentrates the damage and has a small-diameter reinforced concrete structure to verify the damage in more detail. The height is about 1.6m lower than the top of the underground beam. Column height is 3.0m, column thickness is 300x300mm, pile length is 5.0m, pile diameter is 500mm from the top of pile, reinforced concrete member (pile head section) is 250mm, deeper steel pipe member (pile head) The section other than the portion was 416 mm.

(Experimental example 1)
[Evaluation of soundness of pile foundation 2 by forced vibration (striking with hammer, vibrator)]
The soundness evaluation of the pile foundation 2 when the column base 10 located at the lower part of the ramen viaduct A is forcibly vibrated with a hammer or a vibrator will be described with reference to FIGS. 4 to 7.

(1) Examination in sound condition Fig. 4 shows the measurement results measured by the accelerometer (vibration measuring instrument 11) attached to the column base when the column base was hit with a hanging arrow (impact vibration test, vibrator test). The Fourier spectrum obtained from is shown. As a result, a dominant vibration frequency was observed at around 19.0 Hz in the impact vibration test (indicated by symbol c) and the vibrator test (indicated by symbol d) at the column base. This is a value equivalent to the natural frequency (18.1 Hz) of the secondary mode at the time of sound in the preliminary analysis result, and is considered to be the natural frequency of the secondary vibration mode. In addition, the dominant frequency is also confirmed in the vicinity of 4.5 Hz and 6.8 Hz, and this is the natural frequency for the primary vibration mode and the torsional vibration mode based on the result of the column top end hitting and the preliminary analysis result. it is conceivable that. From this result, it is considered that the consistency between the analytical value and the experimental value in the healthy state was confirmed.
In addition, although the primary dominant frequency is seen in the Fourier spectrum when the impact vibration test is performed on the column top end 4A shown in FIG. 2A, the secondary dominant frequency does not appear clearly. . This is considered to be because in the impact vibration test for the column top end 4A, the level of the secondary vibration mode of the pile head where the pile head is greatly deformed is small. On the other hand, when the impact vibration test is performed on the column base 10 shown in FIG. 2 (B), in addition to the primary dominant frequency, the secondary dominant frequency of the pile head is observed. Therefore, in this example, the impact vibration test with respect to the column base 10 is implemented, and the soundness degree which considered the damage of the pile foundation 2 is evaluated.

(2) Examination in consideration of similarity law The test specimen used this time is a 1/2 scale of a general railway ramen viaduct. Here, in order to properly evaluate the effectiveness of this model experiment, it is necessary to consider the similarity law in order to evaluate under the same conditions as possible with the actual size. In this study, this similarity law was examined with reference to previous literature (basic study for development of structural monitoring system, Taisei Construction Technology Center Bulletin, VOL.43, pp.10-1 to 10-4). (Refer to (1) and Formula (2)). This similarity law is similar to the similarity law in the case of equal gravity fields in the previous literature (Similarity Law in Model Vibration Experiments of Earth Structures, Proceedings of JSCE, No.275, pp.69-77, July 1978). The same.

  In this study, it is considered that these relations also hold in the similar rule even in the ramen viaduct model that is the subject of this study, and for the impact vibration test, separately from the usual measurement, the response speed V generated by impact is excited. For the vessel test, the similarity law was considered in comparison with the response speed when it was carried out in the past in the railway ramen viaduct for the inertial force F caused by the vibration force. The inertial force F is composed of a mass and an acceleration as represented by the formula (3), and since it is difficult to change the mass, the acceleration is varied.

  Here, λ is a similarity ratio, F is an inertial force, subscript m is a model, and p is a full-scale structure. Compared to the size of the model of the viaduct at the time of the impact vibration test in the railway ramen viaduct, where the impact vibration test was conducted in the past, the model size is about 1/2, so the actual viaduct with reference to Equation (1) The impact vibration test was performed so that the impact was less than or equal to the weak impact (about 0.11 kine) considering the similarity law according to the measured response speed (about 0.15 kine).

  In addition, regarding the exciter test, since there was no track record for comparison, considering that it is usual to excite at 1000 gal in a general exciter test, With respect to the model, measurement was carried out by varying the excitation force as 250, 500, 750, and 1000 gal with the expectation that the similarity law of inertial force would be about 1/4.

FIG. 5 shows an example of comparison of vibration characteristics between normal impact (indicated by reference symbol e) and weak impact (indicated by reference symbol f) when a column base impact is performed in an impact vibration test.
As a result, even when the striking force was reduced in consideration of the similarity law, the same vibration characteristics as when striking as usual were confirmed. In the vibrator test, even when the excitation force was reduced to 250 gal excitation, the same vibration characteristics could be confirmed as in normal 1000 gal excitation.
Therefore, it was confirmed that the natural frequency of the vibration mode of the whole primary and the pile head secondary can be detected even when the similarity law is taken into consideration.

(3) Examination at the time of partial damage to the pile head Next, a change in the natural frequency was examined when a part of the cover concrete of the pile head was suspended and the pile head was slightly damaged. As a state of simulating a slight partial damage of the pile head, as shown in FIG. 6, the pile head has a range of about 1/4 of the circumferential area, height 250 mm, width 200 mm, and thickness 20 mm. Dropped off at the breaker.

Thereafter, in the state after the suspension, the impact vibration test and the vibrator test were performed in the same manner as before the suspension. FIG. 7 shows a comparison of Fourier spectrum amplitude waveforms before and after fishing in each test.
As a result, there was almost no fluctuation in the natural frequency. This is considered to be because the natural frequency did not change in the cross-sectional defect to the extent that the cover concrete of the pile head was peeled off, and the soundness regarding the stability of the structure was not affected.
In FIG. 7A, reference numeral g1 shows the relationship between the frequency and amplitude before suspension, and reference numeral h1 shows the relationship between the frequency and amplitude after suspension. In FIG. 7B, the symbol g2 shows the relationship between the frequency before the suspension and the transfer function, and the symbol h2 shows the relationship between the frequency and the amplitude after the suspension.

And, as can be seen with reference to the results of Experimental Example 1 described above, there is a constant between the overall primary mode that vibrates around the column top and the pile head secondary mode that vibrates around the pile head. It was confirmed that there is a correlation.
Therefore, when there is a risk of damage to the pile foundation 2 of the ramen viaduct A due to an earthquake or the like, the column base hitting (impact vibration test, vibrator test) is performed as in the primary mode.
And, by reading the detection value of the accelerometer (vibration measuring instrument 11) attached to the column base 10 by hitting the column base, which is based on the natural frequency (18.1 Hz) at the time of sound in the pile head secondary mode, The degree of damage of the pile foundation 2 can be known by observing whether the natural frequency decreases to a certain extent.

As described above, the acceleration data detected by the vibration measuring instrument 11 is supplied to the information processing apparatus C and the data is processed. Then, in the calculation recording means 13 in the information processing apparatus C, a process of calculating and recording the natural frequency of the pile head secondary mode based on the detection value output from the vibration measuring instrument 11 is performed. The evaluation means 14 in the apparatus C monitors whether or not the natural frequency of the pile head secondary mode calculated by the calculation recording means 13 has decreased, and based on the monitoring results, damage to the pile foundation 2 of the ramen viaduct A Determine.
As a result, in the state monitoring device 100, it is possible to accurately evaluate whether or not an abnormality has occurred in the foundation pile foundation 2 based on the detection value output from the vibration measuring instrument 11 without using visual confirmation. it can.

(Experimental example 2)
[Evaluation of soundness of pile foundation 2 using microtremors]
The soundness evaluation that evaluates the damage state of the pile foundation 2 when the ramen viaduct A is constantly finely moved will be described with reference to FIGS.

[1] Outline In maintenance management of civil engineering structures, soundness evaluation methods are being studied for the purpose of enhancing and omitting inspections. For example, in the previous document (Study on evaluation of damage level during earthquake of RC ramen viaduct, Japan Society of Civil Engineers No.731 / I-63, pp51-64, April 2003), acceleration of micro-vibration in the direction perpendicular to the bridge axis The area of the frequency range in the power spectrum has a correlation with the natural frequency, and is shown to be effective in steel girder bridges as a soundness diagnostic index. For this reason, in this Experimental Example 2, a state monitoring method using a power spectrum area ratio was examined for the ramen viaduct model.

In Experimental Example 2, the state monitoring apparatus 100a shown in FIG. 8 is used. In the state monitoring device 100a, the column base 10 located in the vicinity of the underground beam 3 and the pile foundation 2 is provided with a continuous fine movement measuring instrument 11a that measures vibrations due to the fine movement of the column base 10 at all times.
The continuous fine movement measuring instrument 11a detects fine movement of the pier due to wind or the like. The information processing apparatus C includes an operation recording means 13a for calculating and recording evaluation elements such as a power spectrum area ratio and a dominant frequency in the pile head secondary mode based on the detection value output from the microtremor measuring device 11a. The evaluation means 14a for monitoring whether or not a change has occurred in the evaluation element in the pile head secondary mode based on the output from the calculation recording means 13a, and for determining the damage to the viaduct pile foundation 2 based on the monitoring result; Is provided.

[2] Study on the overall primary mode For the overall primary mode, the power spectrum area ratio obtained from the fine movement was measured over a long period of time to confirm its applicability to state monitoring. The measurement was performed five times at intervals of 30 minutes from 2 am to 4 am for 16 seconds each, and the data was stored.
And the power spectrum was computed from the measured microtremor. In brief, the power spectrum indicates the magnitude of vibration for each frequency in terms of the square of the amplitude, and can express wave energy in frequency units.
Examples of power spectra are shown in FIGS. 9 (A) and 9 (B). FIGS. 9A and 9B are graphs showing power spectra for two types of Fourier amplitude spectra detected at different locations, with the horizontal axis representing the frequency and the vertical axis representing the square of the amplitude. As shown in these figures, in the power spectrum, the level of the value clearly appears compared to the Fourier amplitude spectrum. The information processing apparatus C calculates the power spectrum area ratio as an index value indicating the soundness of the pillar 4 of the pier.

As shown in FIG. 9, the power spectrum area ratio has a power spectrum waveform in a range (A) where the frequency f0 (third frequency) is the lower limit and the frequency f1 (first frequency) is the upper limit. And the ratio by the area of the waveform of the power spectrum in the range (b) where the frequency f0 is the lower limit and the frequency f2 (second frequency) greater than the frequency f1 is the upper limit. Each frequency can be arbitrarily determined on condition that f0 <f1 <f2.
In this example, the area of the power spectrum waveform in the range (b) is divided by the area of the power spectrum waveform in the range (b) to obtain the ratio value. That is, the calculation formula of the power spectrum area ratio is expressed as the following formula 4. The power spectrum area described below refers to the area of the waveform of the power spectrum described above (the integrated value of the waveform).
[Power Spectrum Area Ratio] = (Power Spectrum Area from f0 to f2) / (Power Spectrum Area from f0 to f1) (4)

The information processing apparatus C, for example, calculates the power spectrum area ratio as described above from each microtremor obtained by measurement five times or more per day, and uses the average value as the power spectrum area ratio on the measurement day. Store in a recording medium or the like.
Then, by repeating the above procedure and calculating the power spectrum area ratio over time, long-term monitoring of the pier state can be simplified. Furthermore, the soundness of the pier column 4 can be determined using this power spectrum area ratio.

In this experimental example, the frequency range (f0 to f2) is set to f0: 2 Hz, f1: 5 Hz, and f2: 40 Hz in calculating the power spectrum area ratio. The calculated power spectrum area ratio was averaged on a daily basis, arranged as a change with time, and the result is shown in FIG. 10 as “power spectrum area ratio relative to the overall primary mode”. In addition, the dominant frequency is always read from the fine movement and is shown in FIG. 11 as “the dominant frequency with respect to the overall primary mode” similarly to the power spectrum area ratio.
As can be seen with reference to these figures, the power spectrum area ratio and the dominant frequency were both measured at substantially constant values. With regard to the dominant frequency, the ramen viaduct, which is the subject of this study, has a structure that is very easy to sway with respect to the overall primary mode, so the frequency equivalent to the natural frequency can be measured with a constant value over the long term. It was.

[3] Examination for the pile head secondary mode In order to examine the soundness diagnostic method by the fine tremor of the pile head secondary mode, the fine tremor measurement was performed continuously about 30 times. Using the measured microtremors, changes in the power spectrum area ratio and the dominant frequency were examined, and the results are shown in FIGS.
However, in calculating the power spectrum area ratio, the frequency range (f0 to f2) is set to f0: 10 Hz, f1: 20 Hz, and f2: 40 Hz in order to focus on fluctuations in the frequency range where the pile head secondary mode is dominant. .
As a measurement result, the dominant frequency had a larger variation than the power spectrum area ratio, and the power spectrum area ratio was 0.074 and the dominant frequency was 0.150 in terms of the coefficient of variation. Therefore, regarding the pile head secondary mode, it is considered that the power spectrum area ratio is more effective as a soundness diagnostic index than the dominant frequency.

And, as can be seen with reference to the results of Experimental Example 2 above, when there is a risk of damage to the pile foundation 2 of the ramen viaduct A due to an earthquake or the like, the soundness evaluation of the pile foundation 2 using microtremors at all times Can be implemented.
When evaluating the soundness of the pile foundation 2 using microtremors, the power spectrum area ratio and the dominant frequency were calculated while reading the detection values of the accelerometer (almost microtremor measuring instrument 11a) attached to the column base 10. By observing over time how much the calculated value fluctuates with respect to the sound value in the pile head secondary mode, it is possible to know the influence of the damage on the pile foundation 2 on the soundness.
At this time, the damage evaluation of the pile foundation 2 using the power spectrum area ratio is smaller in variation than the damage evaluation of the pile foundation 2 using the dominant frequency. Therefore, the damage evaluation using the power spectrum area ratio is mainly performed. It is good to carry out.

The acceleration data detected by the microtremor measuring instrument 11a is supplied to the information processing apparatus C and the data is processed.
Then, in the calculation recording means 13a in the information processing apparatus C, a process of calculating and recording the natural frequency of the pile head secondary mode based on the detection value output from the microtremor measuring device 11a is performed, and thereafter the information The evaluation means 14a in the processing apparatus C monitors whether or not the power spectrum area ratio and the dominant frequency of the pile head secondary mode calculated by the calculation recording means 13a have changed, and based on the monitoring result, the ramen viaduct A The influence on the soundness of the structure due to the damage of the pile foundation 2 is determined.
As a result, in the state monitoring apparatus 100a, it is possible to evaluate whether or not an abnormality has occurred in the pile foundation 2 based on the detection value output from the microtremor measuring instrument 11a at all times, without visual confirmation.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

  The present invention relates to a soundness evaluation method that can be applied to a concrete structure such as a railway ramen viaduct to efficiently check the presence or absence of damage to a pile foundation including a pile head generated after an earthquake.

DESCRIPTION OF SYMBOLS 1 Concrete structure 2 Pile foundation 3 Underground beam 4 Column 4A Column top end 5 Upper floor beam 10 Column base 11 Vibration measuring instrument 11a Microtremor measuring instrument 12 Exciter 13 Calculation recording means 13a Calculation recording means 14 Evaluation means 14a Evaluation means DESCRIPTION OF SYMBOLS 100 Condition monitoring apparatus 100a Condition monitoring apparatus A Ramen viaduct C Information processing apparatus G Ground R Orbit

Claims (7)

A state monitoring device for a viaduct having a foundation underground beam and a pile foundation, a column fixed to the underground beam, and an upper floor beam fixed to the top end of the column,
A vibration measuring instrument that is installed in a column base located in the vicinity of the underground beam and the pile foundation and measures vibration obtained by striking or vibrating the column base;
Calculation recording means for calculating and recording the natural frequency of the pile head secondary mode based on the detection value output from the vibration measuring instrument;
Monitoring means for determining whether or not the natural frequency of the pile head secondary mode has decreased based on the output from the calculation recording means, and evaluating means for judging damage to the viaduct pile foundation based on the monitoring results; A state monitoring device of a viaduct characterized by comprising.   2. The viaduct state monitoring apparatus according to claim 1, wherein the vibration measuring device measures a striking vibration of striking the vicinity of the column base with a hammer or the like.   2. The viaduct state monitoring apparatus according to claim 1, wherein the vibration measuring device measures forced vibration of a structure due to sweep excitation from a vibrator installed in the vicinity of the column base. 3. A state monitoring device for a viaduct having a foundation underground beam and a pile foundation, a column fixed to the underground beam, and an upper floor beam fixed to the top end of the column,
A microtremor measuring instrument that is installed in a column base located in the vicinity of the underground beam and the pile foundation and measures vibration due to microtremors of the column base;
Calculation recording means for calculating and recording evaluation elements such as power spectrum area ratio and dominant frequency in the pile head secondary mode based on the detection value output from the microtremor measuring device;
Evaluation means for monitoring whether or not a change has occurred in the evaluation element in the secondary mode of the pile head based on the output from the calculation recording means, and determining damage to the viaduct pile foundation based on the monitoring result; A state monitoring device for a viaduct characterized by:   5. The viaduct state monitoring apparatus according to claim 4, wherein the continuous fine movement measuring device detects fine movement of a pier due to wind or the like. A viaduct state monitoring method comprising a foundation underground beam and a pile foundation, a column fixed to the underground beam, and an upper floor beam fixed to the top end of the column,
A measurement stage for measuring vibration obtained by striking or oscillating the column base installed in the column base located near the underground beam and pile foundation;
A calculation step of calculating and recording the natural frequency of the pile head secondary mode based on the detected value detected in the measurement step;
Monitoring whether or not the natural frequency of the pile head secondary mode is reduced based on the calculation result in the calculation step, and evaluating the damage of the viaduct pile foundation based on the monitoring result; A method for monitoring the state of a viaduct characterized by comprising: A viaduct state monitoring method comprising a foundation underground beam and a pile foundation, a column fixed to the underground beam, and an upper floor beam fixed to the top end of the column,
A measurement stage that is installed in the column base located in the vicinity of the underground beam and the pile foundation, and measures vibration due to microtremors of the column base, and
A calculation recording stage for calculating and recording evaluation elements such as a power spectrum area ratio and a dominant frequency in the pile head secondary mode based on the detection value detected in the measurement stage;
Monitoring whether or not a change has occurred in the evaluation element in the secondary mode of the pile head based on the calculation result in the calculation recording stage, and evaluating the damage of the viaduct pile foundation based on the monitoring result; A method for monitoring the state of a viaduct, comprising:

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