JP6261365B2 - Piping bending strain estimation method and piping safety factor evaluation method using the method - Google Patents

Description

  The present invention relates to a pipe bending strain estimation method and a pipe safety factor evaluation method using the method.

  In general, in the maintenance management of buried pipes buried in the ground, the vertical deflection rate and the horizontal deflection rate of the buried pipe are measured, and the safety is evaluated based on the measured values (see FIG. 10). For example, the deflection rate R is represented by the deflection rate R = (flexure amount V) / (tube diameter D). However, since the deflection rate at the time of destruction differs depending on the deformation state of the buried pipe, it is difficult to accurately evaluate the safety based on the deflection rate. Conventionally, a dummy pipe equipped with an optical fiber strain sensor is buried in the ground adjacent to the pipe to be measured, which is an embedded pipe, and an optical signal is incident on this optical fiber strain sensor and from each position in the optical fiber strain sensor. By receiving backscattered light with reflected strain information, the strain distribution along the longitudinal direction of the dummy pipe is obtained, and then the stress distribution generated in the pipe to be measured is estimated from the strain distribution of the dummy pipe. And the management method of the buried pipe which manages the subsidence state of this pipe for measurement is proposed (for example, refer to patent documents 1).

Japanese Patent Publication No. 7-6883

  However, as described above, there is a problem in that it is difficult to accurately evaluate the safety with the deflection rate because the deflection rate at the time of destruction differs depending on the deformation state of the buried pipe. In the invention described in Patent Document 1, if all the buried pipes are of the same type, management can be performed in comparison with the breaking strain or yield strain of the buried pipe, but most of the buried pipes are made of the same material. Not used. In addition, there is a problem in that the dummy pipe with the sensor must be embedded along the pipe to be measured, which increases costs.

  The present invention has been made in order to solve the above-described problems, and is capable of accurately estimating the bending strain of the buried pipe and accurately evaluating the safety factor with a low cost and simple configuration. It is an object of the present invention to provide a strain estimation method, a measuring apparatus used for the method, and a method for evaluating the safety factor of a buried pipe using the method.

In the pipe bending strain estimation method according to claim 1 of the present invention, the measuring means is introduced at an arbitrary position in the pipe after deformation , the distance between the measuring means and the inner surface of the pipe is measured, and the measured value is measured. The first step of obtaining the radius of curvature after deformation relative to the radius of curvature of the pipe before deformation, and estimating the strain of the pipe by applying the elasticity theory of the curved beam to the radius of curvature after deformation obtained in the first step And a second step.

In the bending strain estimation method for piping according to claim 1 of the present invention, measuring means is introduced at an arbitrary position in the pipe after deformation , the distance between the measuring means and the inner surface of the pipe is measured, and the measured value is measured. The first step of obtaining the radius of curvature after deformation relative to the radius of curvature of the pipe before deformation, and estimating the strain of the pipe by applying the elasticity theory of the curved beam to the radius of curvature after deformation obtained in the first step The second step is to be able to easily and quickly estimate the bending strain of the pipe at an arbitrary position, improving the efficiency of maintenance management and ensuring safety for locally deformed pipes. Can be appropriately evaluated.

In the pipe bending strain estimation method according to claim 2 of the present invention, the pipe before deformation in the first step is assumed to be a perfect circle, and the curvature radius after deformation is calculated based on the pipe thickness and the measured value. It is characterized by seeking.

  According to a third aspect of the present invention, there is provided a pipe bending strain estimation method comprising: a first distance measuring instrument; and a leg that supports the first distance measuring instrument in a predetermined position in the pipe. In the first step, the first measuring device is introduced into the pipe, and the distance between the first distance measuring device of the introduced first measuring device and the inner surface of the pipe is measured. At this time, a plurality of measurement points on the inner surface side of the pipe are set at predetermined intervals in the circumferential direction, and the curvature radius is obtained by combining data of the plurality of measurement points.

  In the bending strain estimation method for piping according to claim 3 of the present invention, the measuring means includes a first distance measuring device and a leg that supports the first distance measuring device in a predetermined position in the piping. In the first step, the first measuring device is introduced into the pipe, and the distance between the first distance measuring device of the introduced first measuring device and the inner surface of the pipe is measured. At this time, a plurality of measuring points on the inner surface side of the pipe are set at predetermined intervals in the circumferential direction, and the radius of curvature is obtained by combining the data of a plurality of measuring points, thereby reducing the distance between the measuring points. It is possible to suppress a decrease in accuracy due to the nonuniformity from a perfect circle, to obtain an appropriate distance between measurements, and to obtain a bending strain with high accuracy.

  In the bending strain estimation method for piping according to claim 4 of the present invention, the measurement value measured by the first distance measuring device is corrected by the smoothing process, and the measurement value corrected by the smoothing process is used for any measurement value. It is characterized by selecting three measuring points and calculating the radius of curvature.

  In the bending strain estimation method for piping according to claim 4 of the present invention, the measurement value measured by the first distance measuring device is corrected by the smoothing process, and the measurement value corrected by the smoothing process is used for any measurement value. By selecting three measurement points and calculating the radius of curvature, the effect of non-uniformity from a perfect circle due to manufacturing on the accuracy can be reduced, and the bending strain can be determined accurately.

  A pipe bending strain estimation method according to claim 5 of the present invention is a base in which a measuring means is set to a desired length and introduced into the pipe, and both end sides are in contact with each other along the circumferential direction of the pipe inner surface. And a second distance measuring device provided at the center of the base and measuring a radial distance between the measurement position at the center of the base and the inner surface of the pipe. In this step, the second measuring device is introduced into the pipe, and the base of the second measuring device is moved in the circumferential direction to obtain the radial distance.

  In the bending strain estimation method for piping according to claim 5 of the present invention, the measuring means is set to a desired length and introduced into the pipe, and both ends are contacted along the circumferential direction of the pipe inner surface. And a second distance measuring device provided at the center of the base and measuring a radial distance between the measurement position at the center of the base and the inner surface of the pipe. In this step, the second measuring device is introduced into the pipe, and the base of the second measuring device is moved in the circumferential direction to obtain the radial distance, thereby speeding up the measuring work. A highly accurate bending strain can be obtained.

  A pipe bending strain estimation method according to claim 6 of the present invention is a base in which a measuring means is set to a desired length and is introduced into the pipe, and both end sides abut along the circumferential direction of the pipe inner surface. And a third distance measuring device which is provided on the base so as to be slidable in the longitudinal direction, and which measures a distance between a measurement position where the base is displaceable and a measurement point on the inner surface of the pipe which vertically falls from the measurement position. In the first step, the third measuring device is introduced into the pipe, the base is held at an arbitrary first circumferential measuring position, and a third distance measurement is performed. When the vessel is moved along the base, the distance between the plurality of measurement positions of the base within the sliding range and the measurement points on the inner surface of the pipe suspended from these measurement positions is obtained, and the distance at the circumferential measurement position of the base When the measurement is finished, move the base in the circumferential direction. Te is characterized by repeating the measurements by the third distance measuring instrument.

  A pipe bending strain estimation method according to claim 6 of the present invention is a base in which a measuring means is set to a desired length and is introduced into the pipe, and both end sides abut along the circumferential direction of the pipe inner surface. And a third distance measuring device which is provided on the base so as to be slidable in the longitudinal direction, and which measures a distance between a measurement position where the base is displaceable and a measurement point on the inner surface of the pipe which vertically falls from the measurement position. In the first step, the third measuring device is introduced into the pipe, the base is held at an arbitrary first circumferential measuring position, and a third distance measurement is performed. When the vessel is moved along the base, the distance between the plurality of measurement positions of the base within the sliding range and the measurement points on the inner surface of the pipe suspended from these measurement positions is obtained, and the distance at the circumferential measurement position of the base When the measurement is finished, move the base in the circumferential direction. In addition, it is possible to evaluate whether or not the measurement range is uniformly deformed by repeating the measurement by the third distance measuring device, and at the same time evaluate whether or not the length of the base used for measurement is appropriate can do.

  A pipe bending strain estimation method according to claim 7 of the present invention is a base in which a measuring means is set to a desired length and is introduced into the pipe, and both end sides abut along the circumferential direction of the pipe inner surface. A plurality of measurement positions along the base in the longitudinal direction of the base, and a distance between a plurality of measurement positions along the base and the measurement points on the inner surface of the pipe vertically lowered from the plurality of measurement positions of the base. It comprises a fourth measuring device having a fourth distance measuring device to measure, and in the first step, the fourth measuring device is introduced into the pipe, and the base is set to an arbitrary first circumferential measuring position. The distance between the plurality of measurement positions of the base and the measurement points on the inner surface of the pipe suspended from these measurement positions is obtained by a fourth distance measuring device, and the distance at the first circumferential measurement position of the base is measured. When finished, turn the base around So moved is characterized by repeating the measurement by the fourth distance measuring instrument.

  In the bending strain estimation method for piping according to claim 7 of the present invention, the measuring means is set to a desired length and introduced into the pipe, and both ends are contacted along the circumferential direction of the pipe inner surface. A plurality of measurement positions along the base in the longitudinal direction of the base, and a distance between a plurality of measurement positions along the base and the measurement points on the inner surface of the pipe vertically lowered from the plurality of measurement positions of the base. It comprises a fourth measuring device having a fourth distance measuring device to measure, and in the first step, the fourth measuring device is introduced into the pipe, and the base is set to an arbitrary first circumferential measuring position. The distance between the plurality of measurement positions of the base and the measurement points on the inner surface of the pipe suspended from these measurement positions is obtained by a fourth distance measuring device, and the distance at the first circumferential measurement position of the base is measured. When finished, go around the base Is moved by it has to repeat the measurement by the fourth distance measuring instrument, the measuring operation can be obtained bending strain highly expedited precision.

  The pipe bending strain estimation method according to claim 8 of the present invention is characterized in that the pipe is a buried pipe buried in the ground.

  The pipe safety factor evaluation method according to claim 9 of the present invention obtains at least any one strain of fracture strain or yield strain in advance for each pipe, and estimates by the method of any one of claims 1 to 8. The quantitative safety factor of the pipe to be evaluated is evaluated based on a comparison between the bending strain of the pipe and the previously obtained strain.

  In the safety factor evaluation method for piping according to claim 9 of the present invention, at least any one strain of fracture strain or yield strain is obtained in advance for each piping, and estimated by the method according to any one of claims 1 to 8. Based on the comparison between the bending strain of the pipe and the strain obtained in advance, the quantitative safety factor of the pipe to be evaluated is evaluated, so that the bending strain of the pipe can be simplified at any position. Therefore, safety can be appropriately evaluated even for locally deformed piping.

In the pipe bending strain estimation method according to claim 1 of the present invention, the measuring means is introduced at an arbitrary position in the pipe after deformation , the distance between the measuring means and the inner surface of the pipe is measured, and the measured value is measured. The first step of obtaining the radius of curvature after deformation relative to the radius of curvature of the pipe before deformation, and estimating the strain of the pipe by applying the elasticity theory of the curved beam to the radius of curvature after deformation obtained in the first step Therefore, the bending strain of the pipe can be estimated easily and quickly at an arbitrary position, the maintenance management becomes efficient, and the cost can be reduced.

  The pipe safety factor evaluation method according to claim 9 of the present invention obtains at least any one strain of fracture strain or yield strain in advance for each pipe, and estimates by the method of any one of claims 1 to 8. Since the quantitative safety factor of the pipe to be evaluated is evaluated based on the comparison between the bending strain of the pipe and the previously obtained strain, the bending strain of the pipe can be easily determined at an arbitrary position. In addition, it is possible to estimate quickly and to improve the efficiency of maintenance and management, and it is possible to appropriately evaluate the safety of a locally deformed pipe.

FIG. 1 is an explanatory view showing a state in which a first measuring device used in a pipe bending strain estimation method according to a first embodiment of the present invention is arranged in a pipe. Example 1 FIG. 2 is an explanatory diagram showing the positions of the measurement points in the piping of FIG. FIG. 3 is a graph showing the relationship between strain and distance between measuring points when calculating the curvature of piping by the distance measuring device of the measuring apparatus of FIG. FIG. 4 is an explanatory diagram showing a bending strain and a change in the radius of curvature when a part of the pipe receives a bending moment. 5A and 5B are graphs showing the measurement position before and after the smoothing process, and the distance from the pipe to the distance measuring device, respectively. FIG. 6 is a table showing a comparison of critical strains. FIG. 7 is an explanatory view showing a state in which the second measuring device used in the pipe bending strain estimation method according to the second embodiment of the present invention is arranged in the pipe. (Example 2) FIG. 8 is an explanatory view showing a state in which the third measuring device used in the pipe bending strain estimation method according to the third embodiment of the present invention is arranged in the pipe. (Example 3) FIG. 9 is an explanatory view showing a state in which the fourth measuring device used in the pipe bending strain estimation method according to the fourth embodiment of the present invention is arranged in the pipe. Example 4 FIG. 10 is an explanatory diagram showing the deflection rate of the pipe.

  In order to accurately estimate the bending strain of the pipe and accurately evaluate the safety factor, in the first step, the first measuring device is introduced at an arbitrary position in the pipe. The distance between the first distance measuring instrument and the pipe inner surface is measured, the radius of curvature after deformation is obtained from the measured value, and the radius of curvature after deformation obtained in the first step is obtained in the second step. The strain of the pipe is estimated by applying the elasticity theory of the bending beam, and at least one of the fracture strain and the yield strain is obtained in advance for each pipe, and is estimated by the first step and the second step. This was realized by evaluating the quantitative safety factor of the pipe to be evaluated based on the comparison between the bending strain of the pipe and the strain obtained in advance.

Hereinafter, the present invention will be described with reference to embodiments shown in the drawings. FIG. 1 is an explanatory diagram showing a state in which a first measuring device used in a pipe bending strain estimation method according to a first embodiment of the present invention is arranged in a pipe. As shown in FIG. 1, the first measuring device (measuring means) 2 according to the present embodiment is introduced into the buried pipe (piping) 3 from the ground via a vertical hole (not shown), and the strain is to be obtained. Placed in. The measuring device (first measuring device) 2 includes a distance measuring device (first distance measuring device) 2A and a support leg 2B that supports the distance measuring device 2A in the buried pipe 3. The distance measuring device 2A measures the distance between each measurement point on the measurement side from the measurement reference point on the measurement device side with, for example, a laser distance meter or a digital scanner. The distance measuring device 2A includes a plurality of measuring points P1 to Pn (in a desired range W1 (W1 = 10 ° to 360 °) in the circumferential direction among the distance measuring device 2A arranged in the embedded tube 3 and the inner surface of the embedded tube 3). n is an arbitrary integer greater than or equal to 1, and in FIG. 1 and FIG. 2, the distance between 11 points P1 to P11) is continuously measured. The angle between adjacent measurement points P is measured at intervals of 10 ° pitch or less. Then, the radius of curvature r after deformation at the central measurement point P (measurement point P6 in FIG. 1) from the measured values d1 to dn (d1 to d11 in FIG. 1) (the curvature radius r6 in FIG. 1). (First step S1). That is, in FIG. 1, the curvature radius r6 after deformation is obtained for the central measurement point P6 (measurement position A). In this first step S1, the buried pipe 3 is assumed to be a perfect circle, and the curvature radius after deformation is obtained based on the pipe thickness t and the measured values d1 to dn.

At this time, the measurement by the distance measuring device 2A starts with the measurement values d1 to dn of the distance between the distance measuring device 2A arranged in the buried pipe 3 and the measurement points P1 to Pn. Further, the measurement points P1 and P11 (Pn), P2 and P10 (P (n-1)), equidistant from the central measurement point P6 (measurement position A in FIG. 2), P5 and P7 (P (n -4)) can be calculated. Here, the measurement point P1 in FIG. 1 corresponds to the position F in FIG. 2, and the measurement point P2 corresponds to the position E. Thus, the measuring points P3 to P11 (Pn) correspond to the positions D to F ′ in order. The calculation of the radius of curvature is possible if there are three measurement points, and the distortion at the positions A to F ′ to be obtained is calculated using a combination of a plurality of measurement points. For example, as shown in FIG. 2, the curvature radius r6 of the station position A (station P6) is calculated by combining the data ABB ′, ACC ′, ADD ′, AEE ′, and AFF ′ of five types of station. . For example, when the curvature radius r5 of the measurement point P5 (measurement position B) is obtained as the curvature radius after deformation for each of the plurality of measurement points P1 to Pn, when the position where the strain is to be obtained is “B”, The curvature radius r5 of the station position B (station P5) is calculated by combining the data of the three stations, that is, BCA, BDB ′, BEC ′, and BFD ′. Thus, if the range of the measurement point position is expanded and the number of measurement points is increased, the curvature radii r1 to rn (n is an arbitrary integer greater than or equal to 1) at a desired position in the circumferential direction on the inner surface of the buried pipe 3 can be obtained. Here, if the variation of the values of the curvature radii r1 to r11 for each measurement position A to F ′ in the measurement range W1 is small, it indicates that the measurement range W1 is uniformly deformed.

When the distance between measurement points is small (for example, ABB ′) at the measurement point A (measurement point P6), the accuracy is greatly reduced due to non-uniformity from a perfect circle due to manufacturing, and accurate distortion may not be required. Yes (see FIG. 3). For this reason, in this embodiment, the measured values d1 to dn are subjected to a smoothing process so as to reduce the influence of the nonuniformity from the perfect circle due to the manufacturing on the accuracy (FIG. 5A, ( B)). That is, using the smoothed values, arbitrary three points are selected, and the curvature radius after deformation is calculated. In this way, it is possible to estimate the distortion has good accuracy.

  In addition, when the distance between measurement points is small (for example, ABB '), even when the deterioration in accuracy due to non-uniformity from a perfect circle due to manufacturing increases, the accuracy due to non-uniformity increases as the distance between measurement points increases. Since the decrease is small, accurate distortion can be calculated (see FIG. 3). In this way, accurate strain calculation and selection of appropriate measurement points (inter-station distance) can be performed.

Next, the bending strain ε of the buried pipe 3 is estimated by applying the elastic theory of the curved beam to the radius of curvature rn ( r1 , r2 ,... R11 ) obtained in the first step S1 (first step). 2 step S2). That is, as shown in FIG. 4, when a part of the tube is subjected to a bending moment, a bending strain is generated and the radius of curvature changes, and the change in the radius of curvature is measured. The bending strain ε is calculated from the relationship between the derived curvature radius and the bending strain.

(Equation 1)
ε _max = t / 2 (1 / r _a −1 / r _b ) (1)
Where ε _{max is the} maximum bending strain, t is the tube thickness, r _{a is the} radius of curvature of the tube after deformation, and r _b is the radius of curvature of the tube before deformation. Also, equation (1) is established when the tube thickness is sufficiently small with respect to the radius of curvature. Here, the curvature radius r _b of the undeformed tube, a radius of curvature which is guided a buried pipe assuming a perfect circle.

Next, the effect | action of the bending-strain estimation method of piping which concerns on a present Example is demonstrated. In the pipe bending strain estimation method according to the present embodiment, in the first step S1, a measuring device 2 provided with a distance measuring device 2A such as a laser distance meter or a digital scanner and a leg 2B is installed in an arbitrary position in the embedded pipe 3. The distance between the distance measuring instrument 2A and the inner surface of the buried pipe 3 is measured, and the radius of curvature rn after deformation is measured from the measured values d1 to dn (in this embodiment, the strain is to be obtained) The curvature radius of the measuring point P6 at the measurement position A, which is the position, is obtained, and in the second step S2, the elasticity theory of the curved beam is applied to the curvature radius rn ( r6 ) after the deformation obtained in the first step S1. Thus, the strain ε of the buried pipe 3 is estimated. Therefore, the bending strain ε of the buried pipe 3 can be estimated easily and quickly at an arbitrary position, and maintenance management is made efficient. In the first step S1, the buried pipe 3 is assumed to be a perfect circle, and the curvature radii r1 to rn after deformation are obtained based on the pipe thickness t and the measured values d1 to dn measured. For this reason, it is possible to suppress a decrease in accuracy due to nonuniformity from a perfect circle and to obtain a highly accurate curvature radius. In the first step S1, when measuring the distance from the inner surface of the buried pipe 3 by the distance measuring device 2A, a plurality of measurement points P1 to Pn on the inner surface of the buried pipe 3 are set at predetermined intervals in the circumferential direction. The curvature radii r1 to rn are obtained by combining data of a plurality of measurement points P1 to Pn, that is, data of three measurement points (ABB ′, ACC ′,...). For this reason, a highly accurate radius of curvature can be obtained. Further, in the first step S1, the measurement values d1 to dn measured by the distance measuring device 2A are corrected by the smoothing process, and arbitrary three points are measured using the measurement values corrected by the smoothing process. Since the radius of curvature is selected and the radius of curvature is obtained, a highly accurate radius of curvature can be obtained. Since the curvature radius with high accuracy can be obtained, the accuracy of the estimated bending strain ε is also improved.

  Next, a pipe safety factor evaluation method using the pipe bending strain estimation method according to the first embodiment will be described. In the pipe safety factor evaluation method using the bending strain estimation method according to the above embodiment, first, the fracture strain (or yield strain) is obtained in advance for each manufactured buried pipe 3 and estimated by the bending strain estimation method. The bending strain ε of the buried pipe 3 is compared with the fracture strain (or yield strain) obtained in advance, and if the bending strain ε after deformation is within the criteria for the fracture strain (or yield strain) obtained in advance, a quantitative determination is made. The safety factor is evaluated as high, and if it exceeds the standard, the quantitative safety factor is evaluated as low. Note that either one of the breaking strain and the yield strain may be used, or both may be used in combination.

For example, a reinforced plastic composite pipe (hereinafter referred to as “FRPM pipe”) widely used in pressure pipes for agricultural water is tested based on ISO10471, and the long-term ultimate bending strain B _b after 50 years is obtained from the FRPM pipe. , 9,830 μ. The safety factor is evaluated in comparison with 9,830 μm. The distance as compared to the ultimate bending strain B _b at the measurement point by the measurement instrument 2A, is adapted to evaluate the safety factor at that time.

Furthermore, the AWWA-M45 American Water Works Association (American Water WorksAssociation) as an international standard, long extreme pressure strain 1.8 relative HDB, to consider the safety factor of 1.5 with respect to long-term extreme bending strain _{B b} It is stipulated in. Further, according to the design standards of the Ministry of Agriculture and Fisheries, the upper limit of the use condition is 1/2 of the test internal pressure with respect to the internal pressure and 1/2 of the test external pressure (80% of the fracture external pressure) with respect to the external pressure. In the case of an FRPM tube by filament winding molding (FW molding), the manufacturer sets the limit strain due to internal pressure to 9,000 × 10 ⁻⁶ on the safe side, and further divides it by a creep factor of 1.5 when the test internal pressure is applied Strain. Furthermore, the breaking strain due to the external pressure is 14,900 × 10 ^−6, and 80% of the strain is set as the strain at the test external pressure load. Each value divided by the safety factor 2 is the upper limit during use (see FIG. 6). Thus, in the piping safety factor evaluation method using the bending strain estimation method according to the above-described embodiment, the fracture strain (or yield strain) is obtained in advance for each manufactured buried pipe 3 and obtained in the second step S2. The obtained bending strain ε is compared with the fracture strain (or yield strain) obtained in advance, and based on this comparison, the quantitative safety factor of the buried pipe (piping) 3 to be evaluated for safety is evaluated. Yes. For this reason, the bending strain of the buried pipe 3 can be estimated easily and quickly at an arbitrary position, maintenance management is made efficient, and safety is appropriately evaluated even for locally deformed pipes. Can do.

  Next, a bending strain estimation method for piping according to a second embodiment of the present invention will be described. As shown in FIG. 7, the pipe bending strain estimation method according to the second embodiment is a distance formed by, for example, a laser distance meter or a digital scanner. The measuring instrument 2A is supported in the buried pipe 3 by the support leg 2B, and the distance between the measuring reference point on the measuring instrument 2A side and each measuring point on the measured side is measured. The measuring device 12 of 2 is set to a desired length and introduced into the embedded tube 3, and a base 13 with both ends abutting along the circumferential direction of the inner surface of the embedded tube is provided at the center of the base 13. Except that a depth gauge (second distance measuring device) 14 for measuring a radial distance da (dan) between the measurement position at the center of the base 13 and the inner surface of the buried pipe is different. It has almost the same configuration as the first embodiment.

That is, in the pipe bending strain estimation method according to the present embodiment, in the first step S11, the second measuring device 12 is introduced into the buried pipe 3, and the base 13 of the second measuring device 12 is set in the circumferential direction. In other words, the radial distance da (da1, da2,..., Dan) between the measurement position (measurement reference point) Ps of the base 13 and the inner surface Pa of the buried pipe 3 is obtained. In a second step S12, the first embodiment and the radius of curvature ran after deformation obtained in the same manner (ra1, ra2, ··· ran) by applying the theory of elasticity of curved beam bending of buried pipe 3 The strain εa is estimated.

Here, the distance L from the one end 13A of the base 13 to the measurement reference point Ps of the depth gauge 14 is constant, and when the radial distance da from the measurement reference point Ps to the measurement point Pa on the inner surface of the buried pipe 3 is obtained, Pythagoras asked triangle to the theorem distance L between the measured radial distance da and the respectively orthogonal two sides, the radius of curvature ran after deformation (ra1, ra2, ··· ran) is derived.

  In the second measuring device 12 used in the pipe bending strain estimation method according to the present embodiment, the base 13 is formed in a rectangular flat plate shape, and both end corners in the longitudinal direction are in the circumferential direction on the inner surface of the buried pipe 3. It is made to contact | abut to match. The depth gauge 14 is provided at the center in the longitudinal direction and the center in the short dimension direction of the base 13. The depth gauge 14 has a distance da (da1, da2,..., Da) between the measurement reference point Ps that matches the lower surface of the base 13 and the measurement point Pa on the inner surface of the buried pipe 3 that is perpendicularly lowered from the measurement reference point Ps. Is to measure. That is, the distance da is measured while moving the base 13 in the circumferential direction of the inner surface of the buried pipe 3. The center of the circumferential distance W2 between the abutting portions PaA and PaB of the inner surface of the embedded tube 3 with which both ends 13A and 13B of the base 13 are in contact with the measuring point Pa on the inner surface of the embedded tube 3 of the depth gauge 14. (PaA⌒Pa = Pa⌒PaB)

In the bending strain estimation method for piping according to the present embodiment, in the first step S11, the second measuring device 12 is introduced into the buried pipe 3, and the base 13 of the second measuring device 12 is moved in the circumferential direction. Then, the radial distance da (da1, da2,...) Between the measurement position Ps of the base 13 and the inner surface Pa of the buried pipe 3 is obtained, and in the second step S12, the distance between the first embodiment and the first embodiment is obtained. Similarly, so as to estimate a first curvature after modification obtained in step S11 radius ran (ra1, ra2, ··· ran ) bending strain εa of buried pipe 3 by applying the theory of elasticity of curved beam to As a result, the measurement work can be speeded up and a highly accurate bending strain can be obtained.

  Next, a bending strain estimation method for piping according to a third embodiment of the present invention will be described. As shown in FIG. 8, the pipe bending strain estimation method according to the third embodiment is the same as the pipe bending strain estimation method according to the second embodiment, except that the second measuring device 12 is embedded at both ends. 3 comprises a base 13 abutted along the circumferential direction of the inner surface, and a depth gauge 14 provided at the center of the base 13, whereas the third measuring device 22 has a desired length. The base 23 is set so as to be introduced into the buried pipe 3 and both ends 23A and 23B are brought into contact with each other along the circumferential direction of the inner surface of the buried pipe 3, and the base 23 is slidable in the longitudinal direction. , The measurement position Psi (Ps1, Ps2,... Psn) in the longitudinal direction of the base 23 and the measurement points Pb (Pb1, Pb2, Psn) on the inner surface of the buried pipe 3 suspended from the measurement positions Psi (Ps1 to Psn) of the base 23. ... db distance to Pbn) Except that the movable depth gauge (third distance measuring device) 24 for measuring db1, db2,..., dbn) is different, the configuration is almost the same as that of the second embodiment. ing.

  That is, in the third measuring device 22 used in the pipe bending strain estimation method according to the present embodiment, the base 23 is formed in a rectangular flat plate shape, and both longitudinal corners extend in the longitudinal direction on the inner surface of the buried pipe 3. It is made to contact in the circumferential direction. A groove (not shown) is formed in the base 23 along the longitudinal direction, and the movable depth gauge 24 is slidably engaged with the groove (not shown) and moves. The movable depth gauge 24 stops Psi (Ps1, Ps2,... Psn) at a desired measurement position in the longitudinal direction of the base 23, and this measurement position is taken as a measurement reference point Psi from the measurement reference point Psi to the bottom surface of the base 23. A distance db (db1, db2,..., Dbn) between the inner surface of the buried pipe 3 suspended and the measuring point pb is measured. That is, when the movable depth gauge 24 is moved in the longitudinal direction of the base 23 in a state where both ends 23A and 23B of the base 23 are in contact with the circumferential direction of the inner surface of the embedded tube 3, Psi (Ps1, Ps2) is obtained at a desired measurement position. ,... Psn) After stopping the movable depth gauge 24, the distance dbn between the measurement point Pbn on the inner surface of the buried pipe 3 suspended from the measurement position Psi of the base 23 is measured. Then, a plurality of drooping distances db (db1, db2,. ) Is measured. When the measurement at the contact position of the base 23 is completed, the base 23 is moved in the circumferential direction of the inner surface of the buried pipe 3 and the distance db at different contact positions is measured.

Here, when the distance Li from the one end 23A of the base 23 to the measurement reference point Psi at the position where the movable depth gauge 24 is stopped and the measurement distance db from the measurement reference point Psi to the measurement point Pb on the inner surface of the buried pipe 3 are obtained. , Pythagorean's theorem determines a triangle having a distance Li and a measurement distance db each having two right angles, and derives the radius of curvature rbn ( rb1 , rb2 ,... Rbn ) after deformation.

Thus, in the pipe bending strain estimation method according to the present embodiment, in the first step S21, the third measuring device 22 is introduced into the buried pipe 3, and the base 23 is set to an arbitrary first circumferential measurement position. The movable depth gauge 24 is moved in contact with the base 23 and stopped at a plurality of measurement positions Psi (Ps1, Ps2,... Psn) of the base 23 in the sliding range. A distance db (db1, db2,... Dbn) between the inner surface of the buried pipe 3 suspended from Psi and the measuring point Pb (Pb1, Pb2,... Pbn) is obtained. When the measurement of the distance at the circumferential measurement position is completed, the base 23 is moved in the circumferential direction and the measurement by the movable depth gauge 24 is repeated, and the measurement position Psi (Ps1, Ps2,... Ps) of the base 23 is repeated. ) And the distance db (db1, db2 between buried pipe 3 inside surface, so that seek · · · dbn). Then, in the second step S22, similarly to the second embodiment, the elasticity theory of the curved beam is changed to the curvature radius rbn ( rb1 , rb2 ,... Rbn ) obtained in the first step S21. Is applied to estimate the bending strain εb of the buried pipe 3. For this reason, it can be evaluated whether the measurement range is deformed uniformly. At the same time, it is possible to evaluate whether or not the length of the base used for measurement is appropriate. In other words, as to the suitability of the length of the base, it is sufficient that the base is equal to or shorter than the length that can be introduced into the buried pipe 3, but if the length is too short, the measured value may vary and the radius of curvature after deformation may be affected. Because there is.

  Next, a bending strain estimation method for piping according to a fourth embodiment of the present invention will be described. As shown in FIG. 9, the pipe bending strain estimation method according to the fourth embodiment is the same as the pipe bending strain estimation method according to the third embodiment, in which the third measuring device 22, the base 23, In contrast to the movable depth gauge 24 slidably provided in the longitudinal direction of the base 23, the fourth measuring device 32 is set to a desired length so that the inside of the embedded pipe 3 And a plurality of bases 33 provided at both ends 33 </ b> A and 33 </ b> B along the circumferential direction of the inner surface of the buried pipe 3, and provided at a desired interval in the longitudinal direction of the base 33. Measurement positions Psj1 to Psjn (n is an arbitrary integer greater than or equal to 1) and the measurement points Pc1 to Pcn (n is an arbitrary integer greater than or equal to 1) on the inner surface of the pipe suspended from the plurality of measurement positions Psj1 to Psjn of the base 33 ) The distance between Outside the points constructed by a measuring securing the depth gauge (fourth distance measuring device) 34 a - 34 e are different, has almost the same configuration as the third embodiment.

  That is, in the fourth measuring device 32 used in the pipe bending strain estimation method according to the present embodiment, the base 33 is formed in a rectangular flat plate shape, and both longitudinal corners 33A and 33B are formed on the inner surface of the buried pipe 3. The longitudinal direction is matched with the circumferential direction so as to come into contact. The base 33 is provided with a plurality of fixed depth gauges 34a to 34e at a desired interval along the longitudinal direction, and each of the fixed depth gauges 34a to 34e is provided with measurement reference points Psj1 to Psjn (in this embodiment, measurement is performed). Distances dc1 to dcn between the measurement points pc1 to Pcn (in this embodiment, Pc1 to Pc5) of the inner surface of the buried pipe 3 suspended from the bottom surface of the base 33 from the five reference points Psj1 to Psj5 (this embodiment) In the example, dc1 to dc5) are respectively measured. Then, a plurality of drooping distances dc1 to dc5 are measured in a circumferential range W4 (PcA） PcB) between the contact portions PcA and PcB on the inner surface of the embedded pipe 3 where both ends 33A and 33B of the base 33 abut. Yes. When the measurement at the contact position of the base 33 is completed, the base 33 is moved in the circumferential direction of the inner surface of the buried pipe 3, and the distance dc at different contact positions is measured.

Thus, in the pipe bending strain estimation method according to the present embodiment, in the first step S31, the fourth measuring device 32 is introduced into the buried pipe 3, and the base 33 is set to an arbitrary first circumferential measurement position. The distances dc1 to dc5 between the measurement points Pc1 to Pc5 on the inner surface of the buried pipe 3 suspended from the respective measurement positions Psj1 to Psj5 by the fixed depth gauges 34a to 34e are obtained, and the base 33 is applied. When the measurement of the distance at the contacted circumferential measurement position is completed, the base 33 is moved in the circumferential direction, and the measurement by the fixed depth gauges 34a to 34e is repeated. The distances dc1 to dc5 between the two are obtained. In the second step S32, similarly to the third embodiment, the elasticity theory of the curved beam is set to the radius of curvature rcn ( rc1 , rc2 ,... Rc5 ) after the deformation obtained in the first step S31. Is applied to estimate the bending strain εc of the buried pipe 3. For this reason, in the bending strain estimation method for piping according to the present embodiment, the measurement work is speeded up, and a highly accurate bending strain can be obtained.

  In addition, although the said Example has described the buried pipe buried in the ground, it is not restricted to this, and it cannot be overemphasized that it is applicable also to the piping installed on the ground.

2 Measuring device (first measuring device, measuring means)
3 buried pipes (piping)
d1 to dn Distance between measuring device and buried pipe
radius of curvature after r1 to rn deformation S1 first step S2 second step

Claims (9)

Measuring means is introduced at an arbitrary position in the pipe after deformation , the distance between the measuring means and the inner surface of the pipe is measured, and the curvature radius after deformation with respect to the curvature radius of the pipe before deformation is obtained from the measured value. Bending of piping characterized by having a first step and a second step of estimating strain of the piping by applying the elasticity theory of the bending beam to the radius of curvature after deformation obtained in the first step Strain estimation method. 2. The pipe bending strain according to claim 1, wherein the pipe before deformation is assumed to be a perfect circle in the first step, and the radius of curvature after deformation is obtained based on the pipe thickness and the measured value. Estimation method.   The measuring means is constituted by a first measuring device including a first distance measuring device and a leg that supports the first distance measuring device at a predetermined position in the pipe. When measuring the distance between the first distance measuring device of the introduced first measuring device and the inner surface of the pipe, the measuring points on the inner surface side of the pipe are set at predetermined intervals in the circumferential direction. The method for estimating bending strain of piping according to claim 1 or 2, wherein a plurality of settings are made and the curvature radius is obtained by combining data of a plurality of measurement points.   The measurement value measured by the first distance measuring device is corrected by the smoothing process, and any three measurement points are selected using the measurement value corrected by the smoothing process, and the curvature radius is obtained. The bending strain estimation method for piping according to claim 3. The measuring means is set to a desired length and introduced into the pipe, and both ends are abutted along the circumferential direction of the pipe inner surface, and the measurement position of the center of the base is provided at the center of the base. And a second measuring device comprising a second distance measuring device for measuring a radial distance between the pipe and the inner surface of the pipe,
3. In the first step, the second measuring device is introduced into a pipe and the base of the second measuring device is moved in the circumferential direction to obtain the radial distance. The bending strain estimation method of piping as described in 2. The measuring means is set to a desired length and introduced into the pipe, and both ends are abutted along the circumferential direction of the pipe inner surface, and the base is slidable in the longitudinal direction. A third measuring device comprising a third distance measuring device for measuring a distance between the displaceable measuring position and a measuring point on the inner surface of the pipe vertically falling from the measuring position,
In the first step, the third measuring device is introduced into the pipe, the base is held at an arbitrary first circumferential measuring position, and the third distance measuring device is moved along the base to slide. Find the distance between the multiple measurement positions of the base in the range and the measurement points on the inner surface of the pipe suspended from these measurement positions, and when the distance measurement at the circumferential measurement position of the base is completed, move the base in the circumferential direction Then, the measurement by the third distance measuring device is repeated, and the bending strain estimation method for piping according to claim 1 or 2. A plurality of measuring means are set in a desired length and introduced into the pipe, and a plurality of bases with both ends abutting along the circumferential direction of the pipe inner surface are provided at a desired interval in the longitudinal direction of the base. And a fourth distance measuring device that measures a distance between the plurality of measurement positions along the base and the measurement points on the inner surface of the pipe that respectively descend vertically from the plurality of measurement positions of the base. Consisting of equipment,
In the first step, the fourth measuring device is introduced into the pipe, the base is held at any initial circumferential measurement position, and a plurality of measurement positions of the base and these measurement positions are measured by the fourth distance measuring device. After measuring the distance from the measurement point on the inner surface of the pipe hanging down from the base and measuring the distance at the first circumferential measurement position of the base, move the base in the circumferential direction and measure with the fourth distance measuring instrument. The method of estimating a bending strain of piping according to claim 1 or 2, wherein:   The pipe bending strain estimation method according to any one of claims 1 to 7, wherein the pipe is a buried pipe buried in the ground.   Comparing the bending strain of the pipe estimated by the method according to any one of claims 1 to 8 with the previously determined strain, by obtaining at least any one of breaking strain and yield strain for each piping in advance. A method for evaluating the safety factor of a pipe, characterized in that a quantitative safety factor of the pipe to be evaluated is evaluated based on

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