JP2016099294A - Diagnostic method of pc structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diagnostic method of PC structure capable of diagnosing a state of PC steel at low cost and effectively.SOLUTION: There is provided a method including: a preliminary step S1 of adding, in a state that there is no fracture in buried PC steel, a predetermined vibration to an excitation position set at a desired position of the PC structure, and measuring an attenuation property of a vibration wave detected at a measuring point set at a desired position of the PC structure as a reference value; a measurement step S3 of adding vibration of the same condition as that of the preliminary step S1 to the excitation position of the PC structure, and measuring an attenuation property of a vibration wave detected at the measuring point of the PC structure; and a diagnosis step S4 of diagnosing fracture of PC steel by comparing the attenuation property of the vibration wave measured in the measurement step S3 with the reference value measured in the preliminary step S1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a diagnostic method for providing an index for soundness evaluation of a structure (PC structure) using prestressed concrete, and particularly used as a tension member for a bridge (PC bridge) which is one of existing PC structures. The present invention relates to a diagnostic method suitable for checking the state of a steel material (PC steel material).

  Conventionally, prestressed concrete in which PC steel is embedded is used for road bridges, railway bridges, and the like to which large loads are frequently applied. Patent Document 1 discloses a monitoring system for monitoring the breakage of PC steel material embedded in such a PC structure.

  This monitoring system includes a sensor for detecting an elastic wave propagating in a PC structure, a memory for storing data relating to the elastic wave detected by the sensor, and a warning when the sensor detects an elastic wave exceeding a reference value. One or more sets of two measurement units each having a control unit that performs display and a communication port that outputs data on elastic waves stored in the memory are installed on the surface of the PC structure. The two measurement units are synchronized, and data relating to the elastic wave stored in the memory of each measurement unit can be appropriately collected via the communication port. According to this monitoring system, a warning can be displayed when an elastic wave exceeding the reference value is detected by the energy released when the PC steel material breaks, and in response to this, the administrator can By collecting and analyzing elastic wave data, it is possible to diagnose the fracture state of the PC steel material.

JP 2004-061432 A

  However, in the monitoring system described in Patent Document 1, one or more sets of measurement units must be permanently installed in the PC structure to continuously monitor elastic waves. Also, even if the PC steel material is not broken, such as when a large impact is applied to the PC structure, an elastic wave exceeding the reference value may be generated. When an elastic wave is detected, it is necessary to collect and analyze the elastic wave data stored in each measurement unit to evaluate the state of the PC steel material. For this reason, it takes cost and time to diagnose the soundness of the PC structure.

  This invention is made | formed in view of the said situation, The objective is to provide the diagnostic method of the PC structure which can diagnose the state of PC steel materials more efficiently at low cost.

  In order to solve the above-mentioned problem, in the present invention, the vibration waveform attenuation characteristics measured in the PC structure are measured in advance under the same conditions for the PC structure in a state in which the PC steel material is not broken. The state of the PC steel is diagnosed by comparing with the waveform attenuation characteristics.

For example, the present invention is a PC structure diagnosis method for diagnosing the state of a PC steel material embedded in a PC structure,
A measurement step of measuring a damping characteristic of a vibration waveform detected at a measurement position set at a desired position of the PC structure as a diagnosis target value;
Prior to the measurement step, a preliminary step of measuring the attenuation characteristics of the vibration waveform detected at the measurement position in a state where the PC steel material is not broken as a reference value;
A diagnosis step of diagnosing the state of the PC steel material by comparing the diagnosis target value measured in the measurement step with the reference value measured in the preliminary step.

  The present inventor has found that the damping characteristic of the vibration waveform of the PC structure differs depending on whether or not the PC steel material embedded in the PC structure is broken. In the present invention, the damping characteristic of the vibration waveform measured in the PC structure is compared with the damping characteristic of the vibration waveform measured in advance under the same conditions for the PC structure in which the PC steel material is not broken. Thus, the state of the PC steel material is diagnosed. For this reason, it is only necessary to operate a device (acceleration sensor) for detecting the vibration of the PC structure only when measuring the damping characteristic of the vibration waveform, and it is not necessary to always operate these devices. Therefore, according to the present invention, the state of the PC steel material can be diagnosed more efficiently at a lower cost.

FIG. 1 is a flowchart for explaining a PC structure diagnosis method according to an embodiment of the present invention. 2A is a flowchart for explaining the preliminary step S1 in FIG. 1, and FIG. 2B is a flowchart for explaining the measuring step S3 in FIG. FIG. 3A is a front view of the post-tension simple T-girder bridge 1 partially used for the loading / vibration test. FIGS. 3B and 3C are shown in FIG. It is AA sectional drawing and BB sectional drawing of the post tension simple T girder bridge 1 shown. FIG. 4 is a diagram for explaining a loading / vibration test performed by the present inventor. FIG. 5 (A) is a diagram showing a damped vibration waveform measured by a loading / vibration test performed in a state in which no PC steel strand 2 is cut, and FIG. It is a figure showing the damped vibration waveform measured by the loading and vibration test implemented in the state where three PC steel strands 2 were cut. FIG. 6 is a diagram showing the logarithmic decay rate of the damped vibration waveform measured at each position CH1 to CH4 of the post-tension simple T-girder bridge 1 by the loading / vibration test.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The state of the PC steel material embedded in the existing PC structure such as the PC bridge is diagnosed by the PC structure diagnosis method according to the present embodiment.

  FIG. 1 is a flowchart for explaining a PC structure diagnosis method according to the present embodiment.

  As shown in the figure, the PC structure diagnosis method according to the present embodiment is a preliminary process S1 that is performed in a sound state in which the PC steel material embedded in the PC structure is not broken, such as when the PC structure is completed. And a measurement process S3 and a diagnosis process S4 that are sequentially performed when the inspection time such as periodic inspection and temporary inspection comes (YES in S2).

  FIG. 2A is a flowchart for explaining the preliminary step S1 of FIG.

  First, an exciter and an acceleration sensor are installed on a PC structure to be diagnosed (S11). Here, the acceleration sensor is preferably installed at one or more positions where there is little loss of vibration energy propagating from the vibrator to the PC steel material embedded in the PC structure. On the other hand, the vibrator may be installed at a position where vibration can be applied to the PC steel material embedded in the PC structure. For example, the vibrator is arbitrarily selected from the central portion of the PC steel material to 1/4 of the PC steel material length. It is installed in the position.

  Next, the vibrator is operated, and the PC structure is vibrated, for example, in the vertical direction with a predetermined vibration time, a predetermined frequency, and a predetermined vibration force (S12). Here, when the PC structure is a PC bridge, it is preferable that the vibration generated in the PC bridge simulates the vibration generated when the vehicle travels. Further, the acceleration sensor is operated from the start of the vibration generation by the vibration generator until a time-out occurs after a predetermined time has elapsed. Then, based on the acceleration sequentially detected by the acceleration sensor during the period, the damped vibration waveform of the PC structure after the vibration is stopped is measured (S13). Then, as a parameter representing the damping characteristic of the damped vibration after the vibration is stopped, for example, a logarithmic attenuation factor that is a natural logarithm of the ratio of adjacent amplitudes of the measured damped vibration waveform is calculated and set as a reference value ( S14).

  FIG. 2B is a flowchart for explaining the measurement step S3 of FIG.

  First, the exciter installed in the PC structure in the preliminary process S1 is operated, and the PC structure is generated under the same excitation conditions (excitation time, excitation force, frequency) as in the preliminary process S1. Shake (S31). In addition, the acceleration sensor installed in the PC structure in the preliminary process S1 is operated from the start of vibration by the vibrator until the time-out occurs after the same predetermined time as in the preliminary process S1. Then, based on the acceleration sequentially detected by the acceleration sensor during the period, the damped vibration waveform of the PC structure after the vibration is stopped is measured (S32). Then, the logarithmic decay rate is calculated in the same manner as in the preliminary step S1, and this is set to a diagnosis target value that is an index representing the soundness of the PC steel (S33).

  In the diagnosis step S4, the state of the PC steel material embedded in the PC structure is diagnosed by comparing the diagnosis target value set in the measurement step S3 with the reference value set in the preliminary step S1. For example, a value representing a variation of the diagnosis target value with respect to the reference value, such as a ratio of the diagnosis target value to the reference value (diagnosis target value / reference value) and a difference between the reference value and the diagnosis target value (diagnosis target value−reference value). When it is less than the predetermined value, the state of the PC steel material as the whole PC structure is evaluated as sound. In addition, when the value representing the magnitude of the variation of the diagnosis target value with respect to the reference value is equal to or greater than the predetermined value, it is determined that the PC steel material has a possibility of fracture, and the degree of fracture (what Estimate whether this break occurred.

  Here, the vibrator and the acceleration sensor installed in the PC structure in the preliminary process S1 are used as they are in the measurement process S3, but they are removed from the PC structure at the end of the preliminary process S1. May be. And at every measurement process S3, even if it installs a vibrator and an acceleration sensor in the same installation position as the case of preliminary process S1, and performs S31-S33, even if these are removed from a PC structure at the end of measurement process S3 Good.

  Moreover, although the vibrator is used in order to generate a vibration to PC structure, this invention is not limited to this. For example, when the PC structure is a PC bridge, vibration generated by a vehicle traveling on the PC bridge may be used.

  The inventor conducted a loading / vibration test of a PC structure.

  FIG. 3A is a front view in which a part of the PC structure used in the loading / vibration test is omitted, and FIGS. 3B and 3C show the PC structure shown in FIG. These are AA sectional drawing and BB sectional drawing.

  As shown in the drawing, the present inventor used a post-tension simple T-girder bridge 1 in which five PC steel stranded wires 2 of 12φ7 mm were arranged as a PC structure to be tested. The post-tension simple T-girder bridge 1 has one end 11 in the girder length direction supported by a movable support and the other end 12 supported by a fixed support. Table 1 shows the dimensions of the post-tension simple T-girder bridge 1 including the arrangement positions of the PC steel stranded wires 2 in the post-tension simple T-girder bridge 1.

  FIG. 4 is a diagram for explaining a loading / vibration test of a PC structure.

  As shown in the figure, on the lower surface 14 of the post-tension simple T-girder bridge 1, a point (first point) CH1 that is about 1/4 of the distance L2 between the support position 11 by the movable support, and about the distance L2 between the branches. The acceleration sensor 4 is installed at each of a point having a distance of 2/4 (second point, center portion in the girder length direction) CH2 and a point having a distance of about 3/4 of the inter-branch distance L2 (third point) CH3. In addition, on the upper surface 13 of the post-tension simple T-girder bridge 1, the vibrator 3 is installed at an arbitrary position (fourth point) CH4 between the second point CH2 and the third point CH3. The acceleration sensor 4 is installed in the vessel 3. Then, on the upper surface 13 of the post-tension simple T-girder bridge 1, the static load P / 2 is applied to each of two points that are separated by a distance D (200 mm in this case) with the second point CH2 in the middle. The vibrator 3 is operated, and a vibration having a frequency of 6 to 7 Hz is applied with a predetermined excitation force for about 5 seconds, and during the period until about 20 seconds elapse from the start of the vibration by the vibrator 3. Based on the acceleration sequentially detected by each of the sensors 4, the damped vibration waveform after stopping the vibration at the positions CH <b> 1 to CH <b> 4 is measured.

  In such a loading / vibration test, the PC steel material 2 is simulated by simulating the damage of the PC steel material 2 from the state in which no PC steel stranded wire 2 embedded in the post-tension simple T-girder bridge 1 is cut. While cutting one by one, each state until the four PC steel materials 2 were finally cut was performed. The PC steel stranded wire 2 was cut by core drilling the central portion CH2 in the girder length direction of the post-tension simple T-girder bridge 1.

FIG. 5 (A) shows the attenuation measured by a loading / vibration test carried out in a state where none of the PC steel strands 2 is cut, simulating the state in which all the PC steel strands 2 are healthy. FIG. 5 (B) is a diagram showing a damped vibration waveform 51 measured by a loading / vibration test performed with three PC steel stranded wires 2 cut. is there. Here, the vertical axis represents acceleration (m / s ² ), and the horizontal axis represents time (sec). In addition, the measurement position (installation position of the acceleration sensor 4) of the damped vibration waveforms 50 and 51 is the center part CH2 in the digit length direction. Also, in the figure, in order to make the waveform shape easy to understand, the wavelength is displayed longer (lower frequency) than the actually measured damped vibration waveform.

  A damped vibration waveform 51 measured in a state where three PC steel stranded wires 2 shown in FIG. 5 (B) are cut is a state where none of the PC steel stranded wires 2 shown in FIG. 5 (A) are cut. Compared with the damped vibration waveform 50 measured in (1), the attenuation after the vibration is stopped by the vibrator 3 (after 5 seconds) is large, and the amplitude is rapidly decreased.

  FIG. 6 is a diagram showing the logarithmic attenuation rate of the damped vibration waveform after stopping the vibration measured at each point CH1 to CH4 of the post-tension simple T-girder bridge 1 by the loading / vibration test. Here, reference numerals 60a to 60e are graphs showing the logarithmic attenuation rate of the damped vibration waveform measured at the first point CH1, and reference numerals 61a to 61e are logarithmic attenuation rates of the damped vibration waveform measured at the second point CH2. 62a to 62e are graphs representing logarithmic attenuation rates of the damped vibration waveform measured at the third point CH3, and symbols 63a to 63e are logarithmic attenuations of the damped vibration waveform measured at the fourth point CH4. It is a graph showing a rate. Further, the subscript a of each symbol represents the logarithmic attenuation factor of the damped vibration waveform measured in a state where no PC steel stranded wire 2 is cut, and the subscript b is the PC steel stranded wire 2. Represents the logarithmic attenuation rate of the damped vibration waveform measured with one cut, and the subscript c is the logarithmic attenuation of the damped vibration waveform measured with two PC steel strands 2 cut. The subscript d represents the logarithmic damping factor of the damped vibration waveform measured with three PC steel stranded wires 2 cut, and the subscript e represents the PC steel stranded wire. 2 represents the logarithmic decay rate of the damped vibration waveform measured in a state where four pieces are cut.

  As shown in the figure, at any point CH1 to CH4 of the post-tension simple T-girder bridge 1, the logarithmic attenuation rate of the damped vibration waveform after the vibration is stopped increases as the number of cuts of the PC steel stranded wire 2 increases. The logarithmic attenuation factor of the damped vibration waveform measured with three or more PC steel stranded wires 2 cut is the logarithm of the damped vibration waveform measured with no PC steel stranded wire 2 cut. There was a significant difference in the decay rate. In particular, at the fourth point CH4 where the vibrator 3 is installed, the PC steel stranded wire 2 is 1 in terms of the logarithmic damping factor of the damped vibration waveform measured in a state where two PC steel stranded wires 2 are cut. There was also a significant difference in the logarithmic decay rate of the damped vibration waveform measured without the book being cut. In the experiment, the post-tension simple T-girder bridge 1 in which five PC steel stranded wires 2 are arranged is used. However, when a PC structure having a small number of PC steel materials is used, a smaller number of PC steel materials are used. Even if ruptures, the prestress amount of the PC structure is changed, and it is considered that a significant difference is generated with respect to the logarithmic attenuation rate of the damped vibration waveform measured in a state where no PC steel material is cut. .

  From this, the damping characteristics of the vibration waveform after the vibration is stopped, which is detected by the PC structure when the PC structure is vibrated, differs depending on whether the PC steel material embedded in the PC structure is broken or not. Therefore, it is possible to quantitatively evaluate the state of the PC steel as the whole PC structure by using the parameter representing the damping characteristic of the damped vibration after the vibration is stopped as an index representing the soundness of the PC steel. I understood. In addition, the degree of breakage of PC steel materials (how many were broken) by comparing the damping characteristics of vibration waveforms measured at the time of inspection with the damping characteristics of vibration waveforms measured in advance without PC steel material being broken It was found that can be estimated.

  The embodiment of the present invention has been described above.

  In the present embodiment, the PC structure is vibrated, and the damping characteristics of the vibration waveform measured in the PC structure after the vibration is stopped are the same as those for the PC structure in which the PC steel material is not broken. The state of the PC steel material is diagnosed by comparing with the damping characteristic of the vibration waveform measured in (1). For this reason, it is only necessary to operate the exciter 3 and the acceleration sensor 4 only when measuring the damping characteristic of the vibration waveform, and it is not necessary to always operate these devices. In addition, if the parameter representing the damping characteristic of the vibration waveform after the vibration is stopped is used as an index representing the soundness of the PC steel, the state of the PC steel as the PC structure as a whole is quantitatively diagnosed. The prestress state of the structure can be grasped efficiently. Therefore, according to the present embodiment, the fracture state of the PC steel material can be diagnosed more efficiently at a lower cost.

  In the above embodiment, the logarithmic attenuation rate is used as the attenuation characteristic of the vibration waveform as the parameter indicating the attenuation characteristic of the damped vibration after the vibration is stopped, but the present invention is not limited to this. For example, the time required until the amplitude of the vibration waveform becomes a predetermined value (several percent of the amplitude at the end of excitation), the attenuation ratio, or the like may be used as a numerical value representing the attenuation characteristic of the vibration waveform.

1: Post-tension simple T-girder bridge 2: PC steel stranded wire 3: Exciter 4: Acceleration sensor 11, 12: Post-tension simple T-girder bridge 1 end in the girder length direction 13: Post-tension simple Upper surface of T-girder bridge 14, 14: Lower surface of post-tension simple T-girder bridge 1

Claims (4)

A diagnostic method of a PC structure for diagnosing the state of a PC steel material embedded in the PC structure,
A measurement step of measuring a damping characteristic of a vibration waveform detected at a measurement position set at a desired position of the PC structure as a diagnosis target value;
Prior to the measurement step, a preliminary step of measuring the attenuation characteristics of the vibration waveform detected at the measurement position in a state where the PC steel material is not broken as a reference value;
A diagnostic process for diagnosing the state of the PC steel material by comparing the diagnosis target value measured in the measurement process with the reference value measured in the preliminary process. Diagnosis method. A method for diagnosing a PC structure according to claim 1,
A PC structure diagnosis method, comprising: measuring a damping characteristic of the vibration waveform based on an acceleration detected by an acceleration sensor installed at the measurement position. A method for diagnosing a PC structure according to claim 1 or 2,
A logarithmic attenuation factor is used as the attenuation characteristic of the vibration waveform. A method for diagnosing a PC structure according to any one of claims 1 to 3,
The preliminary step and the measurement step include
A method for diagnosing a PC structure, comprising: applying a predetermined vibration to an excitation position set at a desired position of the PC structure, and measuring a damping characteristic of a vibration waveform detected at the measurement position.

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