JPS61102906A - Method and apparatus for forecasting destruction of structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial application field> The disclosed technology detects fatigue failure of a concrete bridge girder, etc. in which a prestressed steel wire is buried, and detects the initial breakage of a strand of the prestressed steel wire that has been previously buried inside. It belongs to the technical field of detection technology that enables predetermined measures to be taken.

Therefore, the invention of this application is a non-destructive method for internally burying tensile strength wires such as PC steel wires made of a plurality of wires twisted together to prevent fatigue failure of structures such as concrete bridge girders. 1 by detecting the first disconnection of one of the strands of
A method for predicting structural failure that can predict and take predetermined countermeasures regardless of the rapid progression of structural fatigue after the initial breakage of a real wire, and a method that can be directly used in the method. This invention relates to a device, and in particular, detects an elastic wave propagating within a structure due to an initial break in one of the strands using a flexible vibrator or the like on the surface of the structure or at an internal part close to the surface. , a method for predicting structural damage that allows for inspection and recording and countermeasures, and a method for predicting structural failure that uses a flexible vibrator such as a piezoelectric element that responds to the elastic wave and a filter electrically connected to the flexible vibrator to store waveforms. This invention relates to a failure prediction device that is electrically connected to the device, and the waveform storage device is connected to a recording device and a clock of a time measuring device from the time when the first wire breakage occurs.

<Prior Art> As is well known, various structures are constructed as buildings, but it is extremely difficult to deal with not only safety measures against sudden impact failures, but also fatigue failures caused by repeated loads of camphor trees. is important.

For example, concrete bridge girders on expressways with buried PC steel wires are typical structures to which repeated loads are applied over time; It is not always possible to predict the fatigue failure of PC steel wires accurately or evenly, and it is impossible to conduct non-destructive tests on-site, and it is difficult to reproduce them through experiments. Similarly, it is impossible to do it properly and with dignity. .

The nuclide PC steel wire is, for example, a stranded wire such as seven piano wires, etc., and it does not break all at once, but breaks at unspecified points due to various non-average repeated loads. When the so-called first break occurs, in which the PC steel wire breaks first, large repeated loads are applied to other wires over time, causing the wires to break one after another, and finally the entire PC steel wire breaks, causing fatigue failure in the concrete bridge girder. This is what happens.

The successive breakage of each strand causes fatigue on the concrete bridge girder, but this process over time cannot be avoided because the PC steel wire is integrally buried inside the concrete bridge girder. A potential limitation is that it is extremely difficult to detect.

Since unexpected fatigue failure of such structures, such as concrete bridge girders on the above-mentioned expressway, can lead to extremely serious consequences, it is important in civil engineering to be able to fully predict such failures. Not only that, but it is also extremely important and necessary socially.

To deal with this, for example, by connecting an electrical resistance measuring device to both ends of the above-mentioned PC&ll wire and measuring the electrical resistance over time, it is possible to detect the initial breakage of one of the PC steel wires, or
It has been considered to predict the breakage of individual wires one by one, but the contact and non-contact states of the multiple wires that make up the PC1J4 wire are complicated, and the surrounding concrete filling and Since contact conditions vary widely, the method of measuring the electrical resistance of PCUI wires in concrete bridge girders, which are not subject to the same conditions, has the disadvantage that it is not possible to make predictions that fully guarantee reproducibility.

In addition, measuring the break position of the initial wire breakage has the disadvantage that it is extremely cumbersome in terms of equipment, and as a result, it also has the disadvantage of increasing costs.

On the other hand, it is also theoretically possible to acoustically attach a microphone or the like to the side of the concrete bridge girder to receive the propagation energy associated with the first break as audio energy, and perform acoustic detection and measurement using this. is possible, but the probability of picking up environmental noise is extremely high, and therefore,
The problem is that it is difficult to measure the detected waveform.

In particular, it is nearly impossible to attach a microphone to a concrete bridge girder in the field, and research data from a laboratory etc. is too different to apply to fatigue fractures in the field, making it impractical. was there.

<Problems to be Solved by the Invention> The purpose of the invention of this application is to solve the problems of detecting the initial breakage of tensile strength wires in order to deal with fatigue failure of structures embedded with tensile strength wires, such as expressway concrete bridge girders, based on the above-mentioned prior art. is a technical problem to be solved, and one of the tensile strength wires consisting of multiple strands.
Corresponding to the specific frequency of the elastic wave associated with the initial break of the book, it can be detected reliably, and the break as well as the break position can be detected without picking up any environmental vibrations. It is an object of the present invention to provide an excellent structural failure prediction method that can detect the progress of fatigue at an early stage and predict failure, thereby benefiting the field of safe use in the civil engineering and construction industry, and a failure prediction device that can be directly used in the method. It is something to do.

<Means/effects for solving the problem> In order to solve the above-mentioned problem, the structure of the invention of this application, which is based on the scope of the above-mentioned patent claims, is to solve the above-mentioned problem. To detect the initial breakage of a stranded wire such as a PC steel wire that is integrally buried inside a structure from both ends, a pressure of 1
! When a flexible vibrator such as an element is attached, and the loading load of the structure is repeatedly applied, the tensile strength wire of the stranded wire such as the above-mentioned PC steel wire stretched inside the structure will Tension due to the loading load is applied, and the breaking tension acts linearly with the fatigue generated in the structure, and finally, the one that receives the greatest tension among the strands of the tensile strength wire breaks as the first breakage wire,
The elastic wave of the ultrasonic wave generated at the time of the rupture propagates within the structure and becomes a continuous reflected wave.The propagating wave is transmitted through the structure to the above-mentioned flexible transducer, and the plurality of flexible transducers are transmitted to the flexible transducer. If they are attached to different mounting points, there will be a difference in the arrival time, and the flexible vibrator converts the elastic wave into electric vibration and enters the filter of the failure prediction device. The filter removes environmental noise vibrations other than elastic waves from the pro-eutectoid line, which is then input to the waveform storage device, which is further recorded in the recorder, and the time measurement device's clock detects the location where the first break occurs due to the above propagation time difference. However, by observing such a detection state, it is possible to observe the progress of fatigue failure of the structure after the occurrence of the pro-eutectoid line, and to take prescribed countermeasures before an unexpected situation occurs. This was achieved by taking technical measures to make it possible.

<Embodiment - Configuration> Next, one embodiment of the invention of this application will be described below based on the drawings.

The illustrated embodiment is a mode of failure prediction when a concrete bridge girder of an expressway is used as a structure. The target is a concrete bridge girder 2 that is prestressed by burying three wires 1 together.

This example is intended for a test mode, and the three ρC steel wires 1.1.1 are buried at predetermined equal intervals, and the concrete bridge girder 2 is connected to the support body 3 at a predetermined span. .3', and a mounting load F%F is repeatedly applied from above by an appropriate predetermined actuator (not shown).

Reference numeral 5 denotes a fracture prediction device, which constitutes one of the gist of the invention of this application, and includes a detection section 6 attached to the concrete bridge girder 2 and a measurement device electrically connected to the detection section 6. The detection section θ consists of three flexible vibrators 8, &, 8 fixed to the bottom surface of the concrete bridge girder 2 via an adhesive, and is integral with the concrete bridge girder 2. The position is the same in the longitudinal direction along the three PC steel wires 1.1.1 buried in the
It is provided below 1.

Each flexible vibrator 8 is a piezoelectric element made of barium titanate or the like, which is commonly commercially available, and has a large number of fundamental frequencies ranging from several Hz to several hundred kilohertz. When operated with non-resonant vibrations, it is capable of receiving elastic waves of a wide range of frequencies, from acoustic frequencies in the audible range to several hundred kilohertz, and converting them into electrical signals through the piezoelectric effect. , the piezoelectric element 9 and the connector 10 are made into a unit by a case 11 and attached to the bottom surface of the concrete bridge girder 2 at the above-described set interval positions. It is fixed.

Therefore, as shown in the figure, each deflection type vibrates 8.8
．． 1.1.1 Three PC steel wires attached by setting position of 8
If the first east line of any one of the lines breaks for the first time, as shown in Figure 2, the ultrasonic waves of elastic waves generated by the break from the first break will cause damage to the concrete. Due to the time difference between propagating within the bridge girder 2 directly or as a reflected wave and reaching each flexible oscillator 8, any ρ in the length direction as well as the width direction of the concrete bridge girder 2
The measurement unit 1 is configured to detect whether or not a first break has occurred in the C steel wire 1.

Once the first break occurs in the PC steel wire, the measurement unit 1 detects only the elastic wave of the trigger operation and uses a bypass or bandpass filter as a filter to remove surrounding environmental noise vibrations. 12 is electrically connected to each of the above-mentioned flexible transducers, and the filter 12 is further connected to a waveform storage device 13 in which the trigger operation is continuously performed, and the waveform storage device +13 is connected to a recording device 14, It is electrically connected to a clock 15 of the time measuring device, and is configured to record the time at which the trigger operation occurs.

In addition, the clock 15 of this time measuring device is repeatedly loaded on the rack F.
It can also be used as a counter to record the number of times No. 4 is placed on the shelf.

In the above record device 14, as shown in the 3.4 Figure 3.4, the record paper 16 wrapped in a drum that is not shown runs at a low speed, and the recorded pen that is not shown is the above three deflection mobility. The waveform of the detected elastic wave from 8 is recorded.

Depending on the design, the recording device 14 operates when the first breakage of the stranded wire from any PC steel wire 1 - motion ultrasonic wave is generated, and successive waves record one motion of elastic waves. It may also be designed to remember.

<Example - Effect> In the above-described configuration, when the repeated loading load F4 is repeatedly applied to the concrete bridge girder 2 from above by a predetermined actuator (the repeated application situation of the said loading load is of course dependent on other ), one of the PCs [1111, 1, 1) m sum no 1 at a predetermined timing due to an increase in the load on the rack.
The elastic wave caused by the ultrasonic wave generated at the time of rupture propagates within the concrete bridge girder 2, and its direct wave and reflected wave propagate within the concrete bridge girder 2. The signal reaches the piezoelectric element 9 of each flexible vibrator 8 and is received.

Therefore, since there is no trigger vibration before the first wire breakage occurs, no vibration occurs in the recording paper 16 of the recording device 14, as shown in FIG. 3.

Therefore, when the first breakage of one of the strands of one of the PCM wires 1 occurs, in this embodiment, the time difference is adjusted according to the reception of the trigger vibration of the tri-tin flexible vibrator 8.8.8. Accordingly, each elastic wave is immediately converted into an electric signal and transmitted through the filter 12 to the waveform storage device 213.

Then, in the filter 12, noise vibrations and disturbance vibrations from other measuring devices and peripheral equipment for the concrete bridge girder 2 are removed, and once the set voltage is exceeded in the waveform storage device 13, the signal is stored once. .

The received elastic wave signal is then stored in the storage device W114.
As shown in Figure 4, the continuous waveform of the trigger signal from the occurrence of trigger vibration is accurately recorded, but the recording state is as follows.
For example, when the first breakage of one of the strands of the central PC steel wire occurs, as shown in FIG. 4, each flexible vibrator 8.8.
t, t', t' according to the difference in propagation of elastic waves for 8
are recorded with a recording time difference.

In addition, as mentioned above, the time difference of the signal input to the waveform storage device @13 is stored by the clock of the time measuring device 15, and according to the time difference, it is determined which strand of the PC steel wire 1 has the first strand break. It is possible to immediately calculate by a computer (not shown) whether or not this has occurred, and the position of the fracture can be determined.

The fracture position can be determined not only in the longitudinal direction but also in the lateral direction by recording the reception record of the first trigger action elastic wave that is detected and measured.

Therefore, if the detected elastic wave waveform is continuously received and recorded from the state shown in Fig. 3 to the state shown in Fig. 5, from a state where there is almost no wave to a state where there are spikes, the inside of the concrete bridge girder 2 that cannot be directly observed is detected. The first break in the stranded PCwI wire can be detected immediately, thereby making fatigue failure of the concrete bridge girder 2 non-destructive.

It goes without saying that the embodiments of the invention of this application are not limited to the above-mentioned embodiments. For example, in the above-mentioned embodiments, the flexible vibrators are arranged in the horizontal direction, but they may be arranged in the vertical direction,
Alternatively, various embodiments may be adopted in which the initial breaks of a plurality of PC steel wires can be integrally detected and measured by arranging them in a plane in the horizontal and vertical directions.

Furthermore, although the above-described embodiments are for testing and experimentation, measurements may be taken by attaching the apparatus of the invention of this application at predetermined intervals to the core concrete bridge girder of an actually constructed expressway. Alternatively, it is of course possible to attach it to a predetermined location and detect it at different times over time, and it is also possible to apply it to structures with buried tensile strength lines other than concrete bridge girders on expressways. be.

<Effects of the Invention> As described above, according to the invention of this application, fatigue failure of structures in which tensile strength wires such as PC steel wires are integrally buried, such as concrete bridge girders of expressways, can be detected non-destructively at an extremely early stage. This has the advantage of being able to detect fatigue failure before it becomes a fatal fatigue failure and to take appropriate measures such as repair.

Since it is a non-destructive inspection, it also has the advantage that it does not cause any damage to the structure itself, such as concrete bridge girders, and can be inspected and measured while maintaining normal usage conditions. Ru.

In addition, by detecting the elastic waves that propagate inside the structure when the first one of the strands of tensile strength wires that are buried inside the structure is detected, only elastic waves of a specific frequency can be detected. Since it is possible to detect only environmental noise vibrations, disturbance vibrations, etc., the excellent effect that inspection and measurement can be performed extremely accurately is achieved.

In addition, the flexible vibrator has the advantage of being easy to detect, since it is only necessary to use a commercially available piezoelectric element and attach it to a predetermined outer surface of the structure by adhesive or other means. Another advantage is that the detection device is relatively easy to construct.

In this device, since the flexible vibrator is electrically connected to the filter, it is possible to remove disturbances such as imaging, and furthermore, since the device is equipped with a recording device, inspection and measurement can be easily performed. can be visually observed, which also has the effect that the data can be used for other inspection and measurement, and that accurate measures can be taken.

In addition, since the waveform storage device is electrically connected to the time measuring device, it is possible to detect only specific trigger vibrations in which only the waveform exceeding a predetermined voltage is stored, thereby increasing the accuracy of measurement. It has an excellent effect of being able to maintain the structure, and it is also possible to know in which part the first wire breakage has occurred using a time measuring device, and therefore, it is possible to detect the location where fatigue failure has occurred or where it is predicted to occur in the entire structure. Since it is possible to do this, it also has the effect of being able to take precise measures.

[Brief explanation of the drawing]

The drawing is an explanatory diagram of one embodiment of the invention of this application, and the drawing is a first embodiment of the invention of this application.
The figure is a vertical cross-sectional side view of the part where the first wire break of fatigue fracture was detected, Figure 2 is a cross-sectional view of the same, Figure 3 is a plan view of the recording state without the occurrence of the first wire break, and Figure 4 is the trigger waveform plane due to the first wire break. It is a diagram. DESCRIPTION OF SYMBOLS 1... Tensile force line, 2... Structure, 8... Flexible vibrator, 12... Filter, 13... Waveform storage device, 14... Recording device, 15... Time measurement Equipment Applicant Japan Construction Mechanization Association Figure 3

Claims (7)

[Claims] (1) In a method for predicting fatigue failure of a structure in which a tensile strength wire consisting of a plurality of wire aggregates is buried by detecting the first breakage of the wire, A method for predicting structural failure, characterized in that propagating elastic waves are detected on the surface of the structure, visually recorded, and countermeasures are taken. (2) The structure failure prediction method according to claim 1, wherein the detection of the elastic wave is performed by a flexible vibrator. (3) The structure failure prediction method according to claim 1, wherein the elastic waves are detected at a plurality of positions on the surface of the structure. (4) The structure failure prediction method according to claim 3, characterized in that the position of the first break in the strand is detected by detecting the elastic wave. (5) In a device directly used for a method of predicting fatigue failure of a structure in which a tensile strength wire consisting of a plurality of wire aggregates is buried by detecting the first breakage of the wire, the tensile strength wire is buried. A flexible vibrator attached to the surface of the structure is electrically connected to a filter, and the filter is electrically connected to a waveform recording device that is connected to a recording device and a time measurement device. Features: Structural destruction prediction device. (6) The structure destruction prediction device according to claim 5, wherein the filter is a bypass filter. (7) The structure failure prediction device according to claim 5, wherein the flexible vibrator is composed of a piezoelectric element.