KR20220131581A - Dimensional quality inspection method for reinforced concrete structures - Google Patents

Abstract

A method for measuring the shape of reinforced concrete (RC) of the present invention includes steps of: obtaining scan data for a formwork and reinforcing bars constituting a reinforced concrete by a ground laser scanner; removing noise found from the scan data by a data processing device; recognizing the formwork and reinforcing bars by analyzing the scan data by the data processing device; and estimating the dimensions of the formwork and reinforcing bars. In a first step, the ground laser scanner single-scans the reinforced concrete in a Z-axis direction to form the scan data. The present invention is to improve the accuracy of dimensional and quality evaluation.

Description

Reinforced concrete shape measurement method {Dimensional quality inspection method for reinforced concrete structures}

The present invention relates to a method for measuring the shape of reinforced concrete, and more particularly, to a method for automatically measuring the shape of a reinforced concrete structure manufactured at a construction site and a factory using laser scanning.

Matters described in this background section are prepared to promote understanding of the background of the invention, and may include matters that are not already known to those of ordinary skill in the art to which this technology belongs.

Reinforced concrete (RC) means placing reinforcing bars inside concrete to reinforce concrete with weak tensile force. Reinforcing bars and concrete have a characteristic that they behave as one unit because the amount of expansion and contraction according to temperature change is almost the same. In addition, because of various advantages such as high adhesion strength between rebar and concrete, rebar is strong in tension and concrete is strong in compression, rebar in concrete does not corrode, and the coefficient of thermal expansion between rebar and concrete is almost the same, Most of the concrete used in construction sites is reinforced concrete. The end of the reinforcing bar is bent or made into a ring to prevent it from being pulled out from the concrete even when a tensile force is applied.

Dimensional Quality Assessment (DQA) of formwork and reinforcing bars performed before casting the reinforced concrete corresponds to an important inspection task at a factory or construction site. Conventional dimensional quality assessment of formwork and reinforcing bars is There were problems in that an inspector corresponding to a natural person qualified for inspection relied on a manual inspection using a measuring tape, which was labor intensive and excessive time was consumed for the inspection.

In addition, in the case of the conventional dimensional quality evaluation, many safety-related issues have been raised because the inspector must be directly put into the site where the rebar structures are dense for a close evaluation. Criticism has been raised of compromising the integrity of the

Accordingly, the present invention has been devised to solve the problems of the prior art.

Reinforced concrete shape measuring method according to an embodiment of the present invention, by using a laser scanning-based technology, to automatically implement the main dimensions and quality evaluation of reinforced concrete, and to improve the accuracy of the dimension and quality evaluation, There is a purpose.

The shape measurement method of reinforced concrete (RC) for solving the above problems is a step of acquiring scan data for the formwork and reinforcement constituting the reinforced concrete by a ground laser scanner, from the scan data by a data processing device removing the found noise, recognizing the formwork and reinforcing bars by analyzing the scan data by the data processing device, and estimating dimensions of the formwork and reinforcing bars.

In the step of acquiring the scan data, the ground laser scanner performs a single scan of the reinforced concrete in the Z-axis direction, characterized in that the scan data is formed.

In the above, the scan data is characterized in that it includes an upper cover of the formwork, a lower cover of the formwork, an upper reinforcing bar layer, a lower reinforcing bar layer, and background noise.

The step of removing the noise may include subdividing the scan data based on the Z coordinate axis through a histogram and analyzing the peak of the histogram to determine the upper cover, lower cover, upper reinforcing bar layer, lower reinforcing bar layer and background noise. It further includes the step of distinguishing, etc.

In the above, the Otsu threshold is used in the process of removing noise in the step of removing noise.

In the above, the step of recognizing the formwork and reinforcing bars comprises the steps of recognizing the inner surface of the formwork, recognizing the plurality of reinforcing bars, estimating the center point of each of the plurality of reinforcing bars, and line fitting steps for the center point sequentially. .

In the above, the formwork and rebar recognition step, using Random Sample Consensus (RANSAC), is made.

Among the formwork and reinforcing bar recognition step, the center point estimation step includes dividing the reinforcing bar into a plurality of sections, projecting the divided scan data of the reinforcing bar on a plane perpendicular to the scan direction, and the radius and tolerance threshold of the reinforcing bar The center point is estimated by using the circular Random Sample Consensus (RANSAC).

During the dimension estimation step, the dimension of the formwork is estimated as the distance between the vertices extracted from the intersections of the inner surfaces of the formwork recognized by the third step.

In the dimension estimation step, the distance between the plurality of reinforcing bars is estimated by calculating the shortest distance between the reinforcing bars.

Through the means for solving the above problems, since the method for measuring the shape of reinforced concrete according to an embodiment of the present invention can acquire high-precision data using laser scanning data, the position of the reinforcement corresponding to a relatively small size in the reinforced concrete It is also possible to measure precisely.

In addition, the productivity of construction members in construction sites and factories can be greatly improved due to the automation of the data processing process.

In addition, the effects obtainable or predicted by the embodiments of the present invention are to be disclosed directly or implicitly in the detailed description of the embodiments of the present invention. That is, various effects predicted according to an embodiment of the present invention will be disclosed in the detailed description to be described later.

1 is a view showing a terrestrial laser scanner and a data processing device used in a method for measuring the shape of reinforced concrete according to an embodiment of the present invention.
2 is a flowchart illustrating a method for measuring a shape of reinforced concrete according to an embodiment of the present invention.
3 is a diagram illustrating a scan result of laser scanning according to an embodiment of the present invention.
FIG. 4 is a graph showing the scan result of FIG. 3 .
5 is a view showing the shape of the recognized formwork after noise removal according to an embodiment of the present invention.
6 is a view showing a recognition process of reinforced concrete according to an embodiment of the present invention.
7 is a view showing the reinforcing bar center point estimation and line fitting steps according to an embodiment of the present invention.
8 is a view of the reinforced concrete according to an embodiment of the present invention viewed from the XY plane.
9 is a view of the inside of the reinforced concrete according to an embodiment of the present invention viewed from the YZ plane.

The terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the present disclosure. As used herein, singular forms are intended to include plural forms as well, unless the context clearly dictates otherwise. The terms "comprises" and/or "comprising," when used herein, when used herein specify the recited features, integers, steps, acts, components and/or the presence of components, but other features. It will also be understood that this does not exclude the presence or addition of one or more of: elements, integers, steps, acts, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any one or all combinations of the associated listed items.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar elements throughout the specification.

In addition, in the following description, the names of the components are divided into the first, the second, and the like, because the names of the components are the same to distinguish them, and the order is not necessarily limited thereto.

In addition, the X-axis, Y-axis, and Z-axis directions were set by showing coordinate axes in the drawing, and the axial direction of the present specification follows the direction shown in the drawing.

In the present invention, reinforced concrete is defined as a concept including reinforcing bars and a formwork. In the process of pouring reinforced concrete, after placing the reinforcement inside the formwork of reinforced concrete, before pouring concrete, the dimensional quality evaluation to check the exact location and dimensions of the formwork and the reinforcement is an important task.

This is because the strength of reinforced concrete is determined by the arrangement of the reinforcement inside the reinforced concrete. However, since large differences in formwork dimensions that exceed required manufacturing tolerances can cause discrepancies with adjacent reinforced concrete elements during assembly, laser scanning is used to find discrepancies, such as the location of rebars that need to be corrected before pouring concrete. Inspect the dimensions and positions of formwork and reinforcing bars automatically.

Therefore, the reinforced concrete shape measuring method according to an embodiment of the present invention is to automatically implement the main dimension quality evaluation (Deformation Quantification and Analysis) of the reinforced concrete components including the formwork and the rebar spacing in the formwork and the concrete cover. It corresponds to a technology based on laser scanning.

Briefly describing the technology, for the measurement of the reinforced concrete shape, noise is removed in the scanning process, based on the general geometry of the formwork and the reinforcement. Then, the shape and main dimensions of the formwork and reinforcing bars are analyzed, and the shape and main dimensions are automatically extracted using Random Sample Consensus (RANSAC).

RANSAC used here is a random sample matching method, and when erroneously measured data (outlier) occurs due to noise or distortion from the measured scan data, it filters it and sets the data belonging to the normal distribution (inlier). ) to perform regression analysis. Briefly describing the steps of performing RANSAC in the present invention, a regression model is obtained by selecting an arbitrary number of scan data and assuming that it is an inlier. The remaining unselected scan data are compared with the regression model, and scan data within a user-specified tolerance are included in the scan data set (inlier).

Hereinafter, with reference to the following drawings, the reinforced concrete shape measuring technology according to the present invention will be studied in more detail.

1 is a view showing a terrestrial laser scanner and a data processing device used in a method for measuring the shape of reinforced concrete according to an embodiment of the present invention, and FIG. 2 is a method for measuring the shape of reinforced concrete according to an embodiment of the present invention. It is a flowchart shown.

1 to 2, the shape measurement method of the reinforced concrete 10 is largely a step of acquiring raw scan data (S100), a step of pre-processing by removing noise from the raw scan data (S200), the rest Using the scan data to recognize the formwork 200 and the reinforcing bar 100 (S300), and the reinforcing bar 100 and the formwork 200, including the estimation step (S400) of the main dimensions including the dimensions.

The step of acquiring raw scan data (S100) is to install a terrestrial laser scanner (TLS) 20 at a certain distance in the Z-axis direction of the reinforced concrete 10, scan the reinforced concrete 10, and It is achieved through the process of acquiring After that, the raw scan data is transmitted to the data processing device 40, and the step of removing noise by the data processing device 40 (S200), the formwork 200 and the reinforcing bar 100 are performed. Recognizing the step (S300), estimating the main dimensions of the formwork 200 and the reinforcing bar 100 (S400) is made.

The data processing apparatus 40 may include at least one processor, a memory, and a communication interface, and may be connected through a bus. In addition, hardware such as an input device and an output device may be included. The data processing device is a kind of computing device, and various software including an operating system capable of driving a program may be loaded.

The processor is a device that controls the operation of the data processing device, and may be a processor of various types capable of processing instructions included in a program, for example, a central processing unit (CPU), a micro processor unit (MPU), and an MCU. (Micro Controller Unit), GPU (Graphic Processing Unit), and the like. The memory may load a corresponding program so that instructions described to execute the operation of the present invention are processed by the processor. The memory may be, for example, read only memory (ROM), random access memory (RAM), or the like. The storage may store various data, programs, etc. required for executing the operation of the present invention. The communication interface may be a wired or wireless communication module.

The data processing device 40 performs a series of commands including removing noise from the scan data transmitted from the terrestrial laser scanner, recognizing the formwork and rebar, and estimating the main dimensions of the formwork and rebar. can

However, according to the above steps, the construction tolerance of the reinforced concrete 10 may be preferentially set before measuring the shape of the reinforced concrete 10 . The set value for the construction tolerance may include the spacing (S) between the reinforcing bars 100, the width (W) and length (L) of the formwork, the quantity of the reinforcing bars 100 and the concrete cover.

As an example, the allowable tolerance for the spacing (S) and the concrete cover of the reinforcing bar 100 of reinforced concrete (RC) of less than 304.8mm depth may correspond to 76.2mm and ±9.5mm, respectively. In addition, the allowable tolerance for the depth D of the formwork 200 may correspond to ±6.35 or ±9.5 mm for reinforced concrete (RC), respectively. Hereinafter, the method of measuring the shape of reinforced concrete (RC) will be described in detail by dividing the order in time series.

1. Raw Scan Data Acquisition Steps

The raw scan data for the structure of the formwork 200 and the reinforcing bar 100 are acquired by the terrestrial laser scanner 20 . As an example, when the reinforced concrete 10 corresponds to the prefabricated reinforced concrete, the entire shape of the formwork 200 and the reinforcing bar 100 is scanned with a single scan in the Z-axis direction of the ground laser scanner 20. Assuming you can scan. At this time, it can be assumed that the prefabricated reinforced concrete includes two reinforcing bars 100 layers and a rectangular formwork 200 .

Since the scan is performed by installing the ground laser scanner 20 in the Z-axis direction of the formwork 200 and the reinforcing bar 100 , a wide range of scans including the external background of the reinforced concrete 10 is performed in the scanning process.

The terrestrial laser scanner 20 is positioned vertically on the upper part of the reinforced concrete 10 corresponding to the Z-axis so that vertical photography is possible, but the reinforced concrete 10 and the reinforced concrete 10 are spaced apart a certain distance in the X-axis or Y-axis direction, and the Z-axis It is also possible to shoot diagonally at a certain height corresponding to .

2. Noise Removal Step

3 is a view showing a scan result of laser scanning according to an embodiment of the present invention, and FIG. 4 is a view showing the scan result of FIG. 3 as a graph.

The noise removal step aims to remove the noise of the part corresponding to the background of reinforced concrete (RC) found in the scan data and the overlapping scan part in the scanning process.

3 to 4 , segmentation of raw scan data acquired from the terrestrial laser scanner 20 by the data processing device 40 is implemented as follows. 8 and 9, the scan data is largely 1) the upper cover 201 of the formwork 200, 2) the lower cover 203 of the formwork 200, 3) the upper reinforcing bar layer 101 4) the lower The reinforcing bar layer 103, 5) is classified into five types, such as background noise. Accordingly, in the above-described raw scan data acquisition step, the five types of scan data may be acquired by the data processing device 40 .

Three data processing steps are implemented by the data processing device 40 for the plurality of subdivided scan data as described above. First, a histogram of the Z coordinate axis of the raw scan data is generated. Therefore, in the case of the present invention, it is possible to precisely subdivide the scan data of the Z coordinate axis starting from the bottom surface of the reinforced concrete (10).

In the process of removing noise through the data processing device 40 according to an embodiment of the present invention, the concept of the Otsu threshold value may be used to determine multiple threshold values corresponding to peaks on the graph. The principle of the Otsu method is that the threshold is determined as the maximum value or maximum peak in the variance within the Otsu class. Accordingly, referring to FIGS. 3 to 4 , multiple threshold values for dividing five types of raw scan data are formed. Next, based on the fact that the background noise is at the lowest position on the Z axis, a threshold value formed at the lowest height with respect to the Z axis may be estimated and removed as background noise.

When the background noise is removed, overlapping scan data generated at a portion where the reinforcement lines intersect each other, such as the corner of the reinforced concrete 10, is detected and removed in the next step of noise removal. In the case of the present invention, the overlapping scan data is not clearly displayed in the histogram of FIG. 4 because it is rarely present among the scan data values of the reinforced concrete 10 . Therefore, the DBSCAN (Density-based spatial clustering of applications with noise) method is used. Since DBSCAN forms scan data using the density value of the point where the scan is made in the reinforced concrete 10, as described above, there are a plurality of reinforcing bar lines, so the noise of the overlapping part having a relatively high density compared to other parts. ) is easy to identify and remove.

In the histogram of FIG. 4 , two peaks representing the background noise and the lower cover 203 of the formwork 200 of the reinforced concrete 10 are respectively formed as described above. The other four peaks sequentially represent a plurality of lower reinforcing bar layers 103 and an upper reinforcing bar layer 101 in a direction away from the Z-axis direction. of scan values are included. As an example, the orthogonal reinforcing bars 102 are formed in the transverse or longitudinal direction for each reinforcing bar layer. Hereinafter, the step of recognizing the formwork 200 and the reinforcing bar 100 will be described.

3. Formwork and Rebar Recognition Steps

5 is a view showing the shape of a recognized formwork after noise removal according to an embodiment of the present invention, and FIG. 6 is a view showing a recognition process of reinforced concrete according to an embodiment of the present invention.

After the noise removal step described above, using the data processing device 40, the lower cover 203, the lower reinforcing bar layer 103, and the upper reinforcing bar layer of the formwork 200 sequentially for the peaks moving away in the Z-axis direction. (101), it can be seen schematically showing the upper cover 201 of the formwork 200, and the like.

In addition, as shown in FIG. 2, the formwork and reinforcing bar recognition step is in detail 1) the formwork inner surface recognition step (S310), 2) the individual rebar recognition step (S320), 3) estimation of the center point of each reinforcing bar of each reinforcing bar and three sub-steps of the line fitting step (S330) for the center point.

Referring to FIG. 5, looking at the step of recognizing the inner surface of the formwork 200, the inner surface of the formwork 200 using the data processing device 40 is used to recognize the interior including the formwork 200 and the cover of the formwork. do. Preferentially, scans of edges corresponding to vertices and corners of the formwork 200 can be divided into four separate edges using RANSAC. Distinguishing into upper and lower parts can be divided into eight edges, in addition to this, it is self-evident that the surface of the formwork can be further subdivided using RANSAC.

Next, look at the individual reinforcing bar 100 recognition step. As an example, the individual reinforcing bar 100 recognition step aims at recognizing the individual reinforcing bars 100 of the prefabricated reinforced concrete. To this end, it is assumed that the upper reinforcement layer 101 and the lower reinforcement layer 102 are parallel to the bottom surface of the reinforced concrete 10 . The divided scan points of each rebar layer are projected on the XY plane. Since each individual reinforcing bar 100 can be assumed as one line, it is possible to recognize several reinforcing bars using RANSAC.

Referring to FIG. 6 , an embodiment in which the reinforcing bar 100 and the formwork 200 using RANSAC are recognized can be seen. In the case of FIG. 6(a), the upper reinforcing bar layer 101 and the upper structure of the formwork 200 corresponds to one embodiment recognized using RANSAC. In particular, a portion expressed in red means a data value of which one side of the arbitrarily selected die 200 is recognized. In the case of FIG. 6( b ), it corresponds to one embodiment in which the lower structure of the formwork in the Y-axis direction was recognized using RANSAC. In the case of Figure 6 (c), the upper reinforcing bar layer 101 and the lower reinforcing bar layer 103, and the reinforcing bar 100 and the orthogonal reinforcing bar 102, one that recognizes both the upper and lower parts of the formwork 200 It corresponds to an embodiment, and in the case of FIG. 6( d ), it corresponds to an embodiment in which only the reinforcing bar 100 is recognized while the formwork 200 is removed.

7 is a view showing the reinforcing bar center point estimation and line fitting steps according to an embodiment of the present invention, FIG. 8 is a view of the reinforced concrete according to an embodiment of the present invention viewed on the X-Y plane, and FIG. 9 is the present invention It is a view viewed from the Y-Z plane inside the reinforced concrete according to an embodiment of

After recognition of the formwork 200 and the reinforcing bar 100 , the center point estimation and center line fitting step of the reinforcing bar 100 is performed. The above step aims at estimating the centers of a plurality of reinforcing bars 100, respectively, and then finding an optimal reinforcing bar line through line fitting of the estimated centers of the plurality of reinforcing bars 100.

In particular, in the case of FIG. 7 , each individual reinforcing bar 100 recognized in the previous step is divided into a plurality of sections as shown in FIG. Here, it is possible to select the number of divided sections of the individual reinforcing bars 100 according to the performance of dimensional quality assessment (DQA). Next, as shown in FIG. 7( b ), the scan data in each divided section may be projected on a plane perpendicular to the scan direction of the reinforcing bar 100 for estimating the center point of the reinforcing bar 100 . However, as one example, the reinforcing bar 100 has irregularly shaped ribs (not shown) that serve to increase the bonding strength between the reinforcing bar 100 and concrete to be poured later, so that the point on the plane has an irregular circular shape. can have

Therefore, in the case of an embodiment according to the present invention, the circular RANSAC method is used to clearly estimate the center position of the reinforcing bar when estimating the center point in the irregular scan point state as shown in FIG. 7(b). For the circular RANSAC implementation, parameters of 1) circle radius (r) and 2) tolerance threshold (δ) corresponding to two predetermined set values are used as input parameters. Each parameter can be determined individually based on the manufacturing specifications of the rebar.

The average of the maximum and minimum radii of the reinforcing bar 100 may be used to determine the value of the circle radius r. On the other hand, the tolerance threshold value δ may be determined as half the length of the reinforcing bar 100 calculated using the maximum and minimum diameter information of the reinforcing bar 100 from the manufacturing specification. Based on each parameter, the circle radius (r) value measured from the actual scan value is compared, and the center point is estimated by the circular RANSAC. And finally, the center point of the reinforcing bar 100 estimated in a plurality of divided sections of each reinforcing bar may be finally used for line fitting.

4. Dimension Estimation

As can be seen with reference to FIGS. 8 to 9 , when the estimation of the center point of the reinforcing bar 100 and the line fitting of the reinforcing bar 100 are completed, the distance S between the reinforcing bars 100 by the data processing device 40 , the concrete Including dimensions such as length (L), depth (D), and width (W) of the cover and the formwork 200 , dimensions corresponding to values that the user wants to estimate are estimated. First, in relation to the dimension estimation of the formwork 200, estimation of the dimensions inside the formwork 200 is performed. It is possible to estimate the dimension of the formwork 200 by using the position of the vertex of the formwork 200 corresponding to the intersection of three lines among the inner surfaces of the formwork 200 . In detail, using the distance between the vertices and the vertices of the mold 200 individually estimated, the dimensions of individual corners inside the mold including the length of the top and bottom of the mold or the height in the Z-axis direction of the mold can be estimated.

Estimation of the spacing between the reinforcing bars (S) and the spacing between the reinforcing bars 100 and the formwork 200 and the covers 101, 102, 103 is made in the following manner. First, the distance between the center points of two adjacent reinforcing bars 100 is calculated to estimate the reinforcing bar spacing (S). Next, the cover is largely divided into an upper cover 201 , a side cover 202 , and a lower cover 203 . The distance between the upper cover 201 and the lower cover 203 and the reinforcing bar 100 is the closest distance between the outer surface of the reinforcing bar 100 and the covers, respectively, that is, the reinforcing bar 100 and the inside of the formwork 200 . can be calculated as the nearest distance between the upper and lower surfaces of In a similar manner, the side cover 202 can also be calculated as the closest distance to the outer surface of the reinforcing bar 100 and the surface of the inner side of the formwork 200 .

5. Experimental result value

Next, the method of measuring the formwork and reinforced concrete shape using laser scanning is verified through one experimental example.

In one experimental example, a formwork 200 corresponding to 1500 mm (length) × 1000 mm (width) × 200 mm (height) is manufactured. The formwork 200 is made of laminated plywood, and the thickness of the formwork 200 is set to 18mm. Two (upper and lower) reinforcing bar layers 101 and 103 are formed inside the formwork 200, and the diameters of the reinforcing bars constituting the upper reinforcing bar layer 101 and the lower reinforcing bar layer 103 correspond to 12 mm and 16 mm, respectively. . Orthogonal reinforcing bars 102 are installed in the X-axis or Y-axis direction for each of the reinforcing bar layers 101 and 103 . In the above experiment, 6 in the Y-axis direction and 9 orthogonal reinforcing bars 102 in the X-axis direction are installed. In addition, an annular C-shaped reinforcing bar (not shown) is used to connect the upper and lower reinforcing bar layers 101 and 103 to each other.

The FARO M70 TLS corresponding to the terrestrial laser scanner 20 used in the above experiment is used to identify the scan points of the formwork 200 and the reinforcing bar 100 (hereinafter referred to as 'specimen'). The FARO M70 TLS offers a measurement accuracy of ±3mm and a measurement speed of up to 488,000 points/sec in a range of 0.6 m or more to 7 m or less. In the above experiment, the terrestrial laser scanner 20 of the above specification scans all the reinforcing bars 100 and the inner surface in the formwork 200 . The terrestrial laser scanner 20 is installed on a desk with a height of 2.4 m disposed at a location spaced apart from the specimen by a predetermined distance. In order to check whether the scanning angle and resolution of the terrestrial laser scanner 20 with respect to the specimen affect the error value of dimensional estimation, the angle of the specimen is adjusted. The case where the X-axis of the specimen faces the terrestrial laser scanner 20 is defined as 0°, and the case where the Y-axis and the terrestrial laser scanner 20 face by rotation of the specimen is defined as 90°, 0°, The specimen is scanned by three angles of 45° and 90°. In addition, three different angular resolutions of 0.018°, 0.036° and 0.072° are used for testing.

Table 1 shows the experimental results using various specimen angles and angular resolution. Here, "dimension mismatch" is defined as the difference between the dimension estimated by the proposed method and the actual dimension measurement. From the above results, it can be seen that the average discrepancy of the rebar 100 spacing is 2.15 mm and the discrepancy range is between 1.07 mm and 4.39 mm. However, in the case of the rebar (100) spacing, it was observed that the maximum average discrepancy of 4.39 mm occurred in the bottom layer at a sample angle of 45° and an angular resolution of 0.072°.

For the dimension estimation of the formwork 200, it can be seen that the dimensional discrepancy of the formwork 200 averages 2.52 mm and the discrepancy range is between 0.31 mm and 6.26 mm. Similar to the result of dimensional discrepancy of rebar 100 spacing, the maximum mean discrepancy of formwork 200 dimensions corresponds to 6.26 mm occurring in the floor layer at a specimen angle of 45° and an angular resolution of 0.072°.

For the three different specimen angles, it can be seen that the average dimensional mismatch worsens as the angular resolution increases from 0.018° to 0.072°. It is estimated that this is because when the number of scan points recognized on the surface of the reinforcing bar 100 decreases, the performance of estimating the position of the reinforcing bar 100 is negatively affected.

In contrast to the rebar 100 spacing estimation results when the specimen angle is 0° and 45°, the average dimensional discrepancy of the upper reinforcing bar layer 101 at 90° specimen angle is larger than the average dimensional discrepancy of the lower reinforcing bar layer 103 tends to This phenomenon is presumed to be due to the presence of a C-shaped reinforcing bar (not shown) that connects the upper reinforcing bar layer 101 and the lower reinforcing bar layer 103 and serves as a connector between the reinforcing bars near the longitudinal side of the formwork 200 .

The increase in the dimension mismatch due to the C-shaped reinforcing bar (not shown) adversely affects the estimation of the center point of the reinforcing bar 100 . In addition, since the upper reinforcing bar layer 100 is relatively smaller in size than the lower reinforcing bar layer 103, the upper reinforcing bar layer 100 has a small number of scan points recognized on the reinforcing bar surface, so inaccurate rebar spacing estimation seems inevitable. .

Table 2 shows the results of the mismatch of the upper cover 201, lower cover 203) and side cover 202 according to various specimen angles and angular resolution. The experimental results show that the average value of the dimensional estimation mismatch of each cover is about 2.18 mm from 0.96 mm to 4.43 mm. The maximum discrepancy value of the plurality of covers is 14.55 mm generated near the lower cover 203 at a specimen angle of 45° and an angular resolution of 0.072°. For the side cover 202, the average discrepancy value corresponds to 3.12 mm in the range of 1.66 mm to 7.76 mm. The highest discrepancy value of 7.76 mm is observed at the lower side where the sample angle is 45° at an angular resolution of 0.072°, similar to the case of numerical estimation of the cover (top cover 201, bottom cover 203).

In relation to the estimation of the dimensions of the upper cover 201 and the lower cover 203 according to the experimental values, three main results can be derived. First, as the resolution of the angular resolution increases, the dimensional mismatch increases as the number of scan points decreases. It is clearly observed that the dimensional mismatch effect according to the angular resolution is more exacerbated at the specimen angle of 45°. Second, the angle of the specimen has no effect on the estimation of the dimensions of the upper cover 201 and the lower cover 203 . The dimensional difference between the upper cover 201 and the lower cover 203 at three different specimen angles corresponds to less than 1 mm. Third, the dimensional estimation average discrepancy value of the lower reinforcement layer 103 (1.09 mm) is smaller than the average discrepancy value of the upper reinforcement layer 101 (2.83 mm). This is presumed to be because the lower reinforcing bar layer 103 is supported by a cover spacer (not shown) installed to maintain a constant distance between the bottom surface of the formwork and the lower reinforcing bar layer 103 .

Similarly, three main results are derived for the side cover 202 dimension estimation. First, since the rebar center position estimation and inner side estimation performance are greatly affected in terms of angular resolution, the side cover dimension estimation mismatch generally increases as the angular resolution increases. Second, unlike the results of the upper cover 201 and the lower cover 203, the specimen angle effect is observed. The dimensional discrepancy of the side cover 202 corresponds to the lowest average value of 2.48 mm.

Third, since the estimation of the dimensions of the side cover 202 includes the estimation of the inner surface, the result of the estimation of the dimensions of the side cover 202 of the lower reinforcing bar layer 103 is larger than the result of the upper reinforcing bar layer 101 .

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be easily changed by a person skilled in the art from the embodiment of the present invention to equivalent Including all changes to the extent recognized as such.

10: reinforced concrete 20: ground laser scanner
40: data processing unit
100: reinforcing bar 101: upper reinforcing bar layer
102: orthogonal reinforcing bar 103: lower reinforcing bar layer
200: formwork 201: top cover
202: side cover 203: lower cover
L: Formwork Length S: Rebar Spacing
D: Formwork Depth W: Formwork Width

Claims (10)

In the shape measuring method of reinforced concrete (RC),
obtaining scan data for the formwork and reinforcing bars constituting the reinforced concrete by a ground laser scanner;
removing noise found from the scan data by a data processing device;
recognizing the formwork and reinforcing bars by analyzing the scan data by the data processing device; and
A shape measuring method of reinforced concrete comprising the step of estimating the dimensions of the formwork and the reinforcement. According to claim 1,
In the step of acquiring the scan data, the ground laser scanner scans the reinforced concrete in the Z-axis direction to form the scan data. According to claim 1,
The scan data is a shape measuring method of reinforced concrete, characterized in that it includes the upper cover of the formwork, the lower cover of the formwork, upper reinforcing bar layer, lower reinforcing bar layer and background noise. 4. The method of claim 3,
The removing of the noise may include: subdividing the scan data based on the Z coordinate axis through a histogram;
By analyzing the peak of the histogram, the shape measuring method of reinforced concrete further comprising the step of classifying the upper cover, the lower cover, the upper reinforcing bar layer, the lower reinforcing bar layer, and the background noise. 5. The method of claim 4,
The shape measurement method of reinforced concrete, characterized in that the Otsu threshold is used in the process of removing the noise in the step of removing the noise. According to claim 1,
Recognizing the formwork and reinforcing bars includes recognizing the inner surface of the formwork,
Recognizing the plurality of reinforcing bars,
A shape measuring method of reinforced concrete comprising the steps of estimating the center point of each of the plurality of reinforcing bars and fitting a line for the center point. 7. The method of claim 6,
The step of recognizing the formwork and reinforcing bars is a shape measuring method of reinforced concrete made by using Random Sample Consensus (RANSAC). 7. The method of claim 6,
In the step of recognizing the formwork and the reinforcing bar, the center point estimation step is a step of dividing the reinforcing bar into a plurality of sections,
Projecting the divided scan data of the reinforcing bar on a plane perpendicular to the scan direction and
A method for measuring the shape of reinforced concrete by estimating the center point by circular Random Sample Consensus (RANSAC) using the radius and tolerance threshold of the reinforcement. 7. The method of claim 6,
In the step of estimating the dimension, the dimension of the formwork is a shape measuring method of reinforced concrete estimating as the distance between the vertices extracted from the intersection of the inner surface of the formwork recognized by the step of recognizing the formwork and the reinforcing bar. 7. The method of claim 6,
In the step of estimating the dimensions, the distance between the plurality of reinforcing bars is a shape measuring method of reinforced concrete for estimating the shortest distance between the reinforcing bars.

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