JPH03186731A - External pressure strength testing method for centrifugal reinforced concrete pipe - Google Patents

Abstract

PURPOSE:To predict the generation of a crack by detecting a minute sound generated from a centrifugal reinforced concrete pipe during loading at the time of deciding a cracking load in the case of the external pressure strength test of the centrifugal reinforced concrete pipe. CONSTITUTION:In the case of deciding a cracking load at the time of the external pressure strength test of a centrifugal reinforced concrete pipe, by detecting a minute sound generated from the centrifugal reinforced concrete pipe in the course of loading, it becomes an auxiliary means for deciding the cracking load. Also, an acoustic detecting sensor is installed on the surface of the pipe, and with respect to an obtained acoustic signal, by analogizing or digitizing a minute acoustic output generated from the pipe by an acoustic signal processor, and deriving the maximum value of a generated acoustic output per unit time, the generation of a crack of 0.05mm width is predicted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a method for testing the external pressure strength of a centrifugal force reinforced concrete pipe, and particularly to a method for determining cracking load thereof.

[Prior Art 1 A method for determining cracking load during external pressure strength testing of centrifugal reinforced concrete pipes is specified in JIS A 5303. According to this, the cracking load is determined based on the load when a crack with a width of 0.05a+m occurs in the tube. Detection of this crack is generally done by visual inspection with the naked eye, and the crack width is 0.05.
Since 1 mm is the limit that can normally be detected with the naked eye, its detection has been extremely difficult.

In addition, attaching a dial gauge or the like to observe the amount of deformation of the pipe due to pressurization is generally used as an effective method for predicting when cracks will occur, but the point of inflection is not clear. , it is difficult to make accurate judgments.

[Problem to be Solved by the Invention 1] Therefore, since the determination of the cracking load during the external pressure strength test of centrifugal reinforced concrete pipes relies on visual inspection in many parts, it is difficult to determine the true cracking load, and it is difficult to determine the true cracking load. There was a lot of variation in the results due to errors.

[Means for Solving the Problem] The present inventors have discovered that when external pressure acts on a solid material and cracks occur, no matter how small the crack is, sound is generated due to the sudden release of elastic energy. However, by utilizing the phenomenon of widening the inside of a solid, it was found that it is possible to assist in determining the cracking load in the external pressure strength test method for centrifugal reinforced concrete pipes described above, and this led to the completion of the present invention. Ta.

That is, the present invention provides an auxiliary means for determining cracking loads during external pressure strength tests of centrifugal reinforced concrete pipes by detecting minute sounds generated from centrifugal reinforced concrete pipes during loading. The present invention provides a method for testing the external pressure strength of centrifugal force reinforced concrete pipes.

In order to determine the cracking load according to the present invention, an acoustic detection sensor is attached to the pipe surface, and the obtained acoustic signal is converted into analog or digital form by an acoustic signal processing device, and the minute acoustic output generated from the pipe is converted into analog or digital form over a unit time. JIS A 5 by determining the maximum value of the sound output generated per
This is done by predicting the occurrence of cracks with a width of 0.05 nn as specified in 303.

The acoustic detection sensor used in the present invention may be of any type as long as it can detect a wide range of acoustic waves in concrete.

The acoustic signal processing device used in the present invention can be of any type as long as it can convert the acoustic signal from the acoustic detection sensor into an electrical signal, digitize and measure the signal, and process it into an acoustic output per unit time. I don't care.

[Action 1: When an external force acts on a centrifugal reinforced concrete pipe and a crack with a width of 0.05 mm or less that is difficult to detect visually appears on the inner surface of the pipe, the amount of sound emitted by this type of crack is , is considered to show the maximum value.

Therefore, by observing the pipe body with great care immediately after the maximum value of the generated sound output per unit time is reached, the possibility of missing a crack with a width of 0.051 + 11 is extremely small, and the timing of its occurrence can be accurately determined. can be determined.

That is, the detection of the generated sound output per unit time according to the present invention is an extremely effective auxiliary means for predicting the determination of the cracking load according to the JIS standard.

Figure 1 shows that a centrifugal reinforced concrete pipe with a nominal diameter of 600 mm and a length of lra was subjected to an external pressure test in accordance with JIS A 5303, the occurrence of cracks was detected by an acoustic detection sensor, and the occurrence of cracks per unit time was detected by acoustic signal processing. It is a graph showing the amount of sound generated. The horizontal axis of the figure represents loading time, and the vertical axis represents acoustic energy. The acoustic energy is
The amplitude of the acoustic wave was expressed as a voltage (mVl), and its square value was taken as the value.

The load increases as the loading time passes, and the loading amount becomes 508.
The acoustic energy value shows the maximum value when it reaches 0 kgf/+, and then the width is 0.05 at a load of 5110 kgf/m.
A crack of n+m was observed, and this load was determined to be a cracking load.

The result of determining the same sample using the JIS visual method was 5090.
~5370 kg, and measurements according to the invention using acoustic detection were in the range of measurements using this visual method.

[Example 1 The concretes used in the following Examples and Comparative Examples had the formulations shown in Table 1. In addition, the expansion material is placed inside the cement with a nominal diameter of 200mm, 600++n, 1800+n.
In the case of m, 10%, 12%, and 15% were mixed, respectively. In addition, 10 concrete pipes of each nominal diameter were manufactured as measuring concrete pipes.

Table 1 Comparative Examples 1 to 3 According to JIS A 5303, pipe diameter (nominal diameter) 20
External pressure tests were conducted on three types of pipes: 0 mm, 600 questions, and 1800 ms, using five of the concrete pipes for measurement as specimens.

The results are shown in Table 2.

Actual flow examples 1 to 3 For each of the remaining five samples used in the above comparative examples, using the acoustic detection sensor and acoustic signal processing device shown below,
The minute sound generated from the tube was measured, the sound energy generated per unit time was output using an acoustic signal processing device, and from the moment the maximum value was detected, cracks were observed with particular care. The cracking load was determined visually.

Acoustic detection sensor: AE-200 (manufactured by Megacera) Single-sided signal processing device: Megasor AE-I+ (manufactured by Megacera) The results are shown in Table 2.

[Effect of the invention 1 According to the present invention, when determining the cracking load during an external pressure strength test of a centrifugal reinforced concrete pipe, cracks can be detected by detecting minute sounds generated from the centrifugal reinforced concrete pipe during loading. prediction was obtained, and the measurement results were at the same level as those obtained by the JIS standard method, and the variation in results due to human error in the conventional judgment of crack occurrence based only on visual inspection was significantly reduced.

[Brief explanation of drawings]

FIG. 1 shows an example of measurement results obtained by the method of the present invention.

Claims (1)

[Claims] (1) In determining cracking loads during external pressure strength tests of centrifugal reinforced concrete pipes, detecting minute sounds generated from centrifugal reinforced concrete pipes during loading can be used as an auxiliary means for determining cracking loads. A method for testing the external pressure strength of centrifugal reinforced concrete pipes.